@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/106814,
title ="Conjecture on the Design of Helical Proteins",
author = "Kozak, John J. and Gray, Harry B.",
journal = "Journal of Physical Chemistry B",
volume = "124",
number = "49",
pages = "11067-11071",
month = "December",
year = "2020",
doi = "10.1021/acs.jpcb.0c05669",
issn = "1520-6106",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20201124-122000714",
note = "© 2020 American Chemical Society. \n\nReceived: June 22, 2020; Revised: October 31, 2020; Published: November 24, 2020. \n\nThe authors thank R. A. Garza-López for helpful discussions. Work at Caltech was supported by the NIH (DK019038) and the Arnold and Mabel Beckman Foundation. \n\nThe authors declare no competing financial interest.",
revision_no = "16",
abstract = "In an important advance in our understanding of protein folding, Wolynes and Onuchic found that the frustration ratio, T_f/T_s, for funneled energy landscapes is T_f/T_s ∼1.6. In our recent work on four heme proteins, we showed that when a protein unfolds from the native state to an early unfolded state, the degree of departure is characterized by a ratio f ∼1.6, where f is a measure of the elongation of n-residue segments of the polypeptide chain. Our analysis, which accounts for this apparent similarity in calculated signatures, is based on a logistic-map model of unfolding. We offer an important take home for the de novo protein synthesis community: in order to increase the probability of obtaining good quality crystals, nearest-neighbor repulsive interactions between adjacent residues (or sequences of residues) in the polypeptide chain must be propagated correctly.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/106962,
title ="Third-Generation W(CNAr)₆ Photoreductants (CNAr = Fused-Ring and Alkynyl-Bridged Arylisocyanides)",
author = "Fajardo, Javier, Jr. and Schwan, Josef",
journal = "Inorganic Chemistry",
month = "December",
year = "2020",
doi = "10.1021/acs.inorgchem.0c02912",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20201208-105038243",
note = "© 2020 American Chemical Society. ACS Editors' Choice. \n\nReceived 30 September 2020. Published online 6 December 2020. \n\nWe thank Dr. David VanderVelde and Lawrence M. Henling for assistance with NMR and XRD experiments, respectively. The X-ray Crystallography Facility in the Beckman Institute at Caltech was supported by the Dow Next Generation Instrumentation Grant. \n\nFunding:\nThis work was supported by the National Science Foundation\n(Grant CHE-1763429) and the Beckman Institute Laser\nResource Center, supported by the Arnold and Mabel\nBeckman Foundation.\n\nAuthor Contributions. All authors have given approval to the final version of the manuscript. \n\nThe authors declare no competing financial interest.",
revision_no = "15",
abstract = "Homoleptic tungsten(0) arylisocyanides possess photophysical and photochemical properties that rival those of archetypal ruthenium(II) and iridium(III) polypyridine complexes. Previous studies established that extending the π-system of 2,6-diisopropylphenylisocyanide (CNDipp) by coupling aryl substituents para to the isocyanide functionality results in W(CNDippAr)₆ oligoarylisocyanide complexes with greatly enhanced metal-to-ligand charge transfer (MLCT) excited-state properties relative to those of W(CNDipp)₆. Extending electronic modifications to delineate additional design principles for this class of photosensitizers, herein we report a series of W(CNAr)₆ compounds with naphthalene-based fused-ring (CN-1-(2-ⁱPr)-Naph) and CNDipp-based alkynyl-bridged (CNDipp^(CC)Ar) arylisocyanide ligands. Systematic variation of the secondary aromatic system in the CNDippCCAr platform provides a straightforward method to modulate the photophysical properties of W(CNDipp^(CC)Ar)₆ complexes, allowing access to an extended range of absorption/luminescence profiles and highly reducing excited states, while maintaining the high molar absorptivity MLCT absorption bands, high photoluminescence quantum yields, and long excited-state lifetimes of previous W(CNAr)₆ complexes. Notably, W(CN-1-(2-iPr)-Naph)₆ exhibits the longest excited-state lifetime of all W(CNAr)₆ complexes explored thus far, highlighting the potential benefits of utilizing fused-ring arylisocyanide ligands in the construction of tungsten(0) photoreductants.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/104974,
title ="Cathodic NH₄⁺ leaching of nitrogen impurities in CoMo thin-film electrodes in aqueous acidic solutions",
author = "Yu, Weilai and Buabthong, Pakpoom",
journal = "Sustainable Energy and Fuels",
volume = "4",
number = "10",
pages = "5080-5087",
month = "October",
year = "2020",
doi = "10.1039/d0se00674b",
issn = "2398-4902",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20200817-095314564",
note = "© 2020 The Royal Society of Chemistry. \n\nSubmitted 01 May 2020; Accepted 05 Aug 2020; First published 05 Aug 2020. \n\nK. B. acknowledges funding from the fellowship program of the German National Academy of Sciences – Leopoldina, grant LPDS 2016-06. Acknowledgment is made to the donors of The American Chemical Society Petroleum Research Fund for partial support of this research. Sample preparation and analyses were performed at the Joint Center for Artificial Photosynthesis, supported through the Office of Science of the U.S. Department of Energy under Award Number DE-SC0004993, which also provided support for N. S. L., W. Y., P. B. and C. G. R. We acknowledge use of instrumentation in the Molecular Materials Research Center of the Beckman Institute at Caltech. N. F. D. is grateful to the Linde Center for support. The Environmental Analysis Center is supported by the Beckman Institute at Caltech. W. Y. and C. G. R. acknowledge the Resnick Sustainability Institute at Caltech for fellowship support. Dr Fabai Wu and Prof. Victoria Orphan are acknowledged for providing the ¹⁵NH₄Cl standard reagent for UPLC-MS analysis. Mr Christopher Kenseth is thanked for assistance with UPLC-MS analysis. Dr Yuanlong Huang is acknowledged for assistance with chemiluminescence analysis. All authors would like to acknowledge the reviewers for their valuable comments in the first round. \n\nThere are no conflicts to declare.",
revision_no = "24",
abstract = "Electrocatalytic reduction of dinitrogen (N₂) to ammonium (NH₄⁺) in acidic aqueous solutions was investigated at ambient temperature and pressure using a cobalt–molybdenum (CoMo) thin-film electrode prepared by magnetron reactive sputtering. Increased concentrations of ammonium ions (NH₄⁺) were consistently detected in the electrolyte using ion chromatography (IC) after constant-potential electrolysis at various potentials (≤−0.29 V vs. RHE). Using a newly developed analytical method based on ammonia derivatization, performing the experiments with ¹⁵N₂-labelled gas led however to the detection of increased ¹⁴NH₄⁺ concentrations instead of ¹⁵NH₄⁺. X-ray photoelectron spectroscopic (XPS) analysis of the electrode surface revealed the presence of Mo N and Mo–NH_x species. Several contamination sources were identified that led to substantial increases in the concentration of ammonium ions, including ¹⁵NH₃ impurities in ¹⁵N₂ gas. The observed ammonium concentrations can be consistently ascribed to leaching of nitrogen (¹⁴N) impurities incorporated in the CoMo film during the sputtering process. Researchers in the field are therefore urged to adopt extended protocols to identify and eliminate sources of ammonia contamination and to very carefully monitor the ammonium concentrations in each experimental step.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/104400,
title ="Structural stability of the SARS-CoV-2 main protease: Can metal ions affect function?",
author = "Kozak, John J. and Gray, Harry B.",
journal = "Journal of Inorganic Biochemistry",
volume = "211",
pages = "Art. No. 111179",
month = "October",
year = "2020",
doi = "10.1016/j.jinorgbio.2020.111179",
issn = "0162-0134",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20200716-094538897",
note = "© 2020 Elsevier Inc. \n\nReceived 26 May 2020, Revised 8 July 2020, Accepted 10 July 2020, Available online 16 July 2020. \n\nWork at Caltech was supported by the NIH (DK019038) and the Arnold and Mabel Beckman Foundation. Support at Pomona College was provided by the Howard Hughes Medical Institute Research Program and a Sontag Research Fellowship Award. Molecular graphics and analyses performed with UCSF Chimera, developed by the Resource for Biocomputing, Visualization, and Informatics at the University of California, San Francisco, with support from NIH P41-GM103311. \n\nThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.",
revision_no = "24",
abstract = "We have investigated the structural stability of the SARS (Severe acute respiratory syndrome)-CoV-2 main protease monomer (Mpro). We quantified the spatial and angular changes in the structure using two independent analyses, one based on a spatial metrics (δ, ratio), the second on angular metrics. The order of unfolding of the 10 helices in Mpro is characterized by beta vs alpha plots similar to those of cytochromes and globins. The longest turning region is anomalous in the earliest stage of unfolding. In an investigation of excluded-volume effects, we found that the maximum spread in average molecular-volume values for Mpro, cytochrome c-b₅₆₂, cytochrome c’, myoglobin, and cytoglobin is ~10 ų. This apparent universality is a consequence of the dominant contributions from six residues: ALA, ASP, GLU, LEU, LYS and VAL. Of the seven Mpro histidines, residues 41, 163, 164, and 246 are in stable H-bonded regions; metal ion binding to one or more of these residues could break up the H-bond network, thereby affecting protease function. Our analysis also indicated that metal binding to cysteine residues 44 and 145 could disable the enzyme.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/104882,
title ="Unfolding cytochromes c-b₅₆₂ and Rd apo b₅₆₂",
author = "Kozak, John J. and Gray, Harry B.",
journal = "Journal of Inorganic Biochemistry",
volume = "211",
pages = "Art. No. 111209",
month = "October",
year = "2020",
doi = "10.1016/j.jinorgbio.2020.111209",
issn = "0162-0134",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20200810-134213212",
note = "© 2020 Elsevier Inc. \n\nReceived 30 April 2020, Revised 26 July 2020, Accepted 28 July 2020, Available online 10 August 2020. \n\nWe thank Devarajan (Dave) Thirumalai for very helpful comments. Work at Caltech was supported by the NIH (DK019038) and the Arnold and Mabel Beckman Foundation. Support at Pomona College was provided by the Howard Hughes Medical Institute Research Program and a Sontag Research Fellowship Award. \n\nThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.",
revision_no = "16",
abstract = "We have analyzed the early stages of unfolding of cytochromes c-b₅₆₂ (PDB ID: 2BC5) and Rd apo b₅₆₂ (PDB ID: 1YYJ). Our geometrical approach proceeds from an analysis of the crystal structure reported for each protein. We quantify, residue-by-residue and region-by-region, the spatial and angular changes in the structure as the protein denatures, and quantify differences that result from the seven residues that differ in the two proteins. Using two independent analyses, one based on spatial metrics and the second on angular metrics, we establish the order of unfolding of the five helices in cyt c-b₅₆₂ and the four helices in the apo protein. For the two helices nearest the N-terminal end of both proteins, the ones in the apo protein unfold first. For the two helices nearest the C-terminal end, the interior helix of the apo protein unfolds first, whereas the terminal helix of the holo protein unfolds first. Excluded-volume effects (repulsive interactions) are minimized in turning regions; the overall range in Δ values is Δ = 36.3 ų for cyt c-b₅₆₂ and Δ = 36.6 ų for the apo protein, whereas the span for all 20 amino acids is Δ = 167.7 ų. As our work indicates that the interior helix of cytochrome c-b₅₆₂ is the first to fold, we suggest that this helix protects the heme from misligation, consistent with ultrafast folding over a minimally frustrated funneled landscape.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/104194,
title ="Cyano-Ambivalence: Spectroscopy and Photophysics of [Ru(diimine)(CN-BR₃)₄]²⁻ Complexes",
author = "Ngo, Danh and Del Ciello, Sarah A.",
journal = "Polyhedron",
volume = "188",
pages = "Art. No. 114692",
month = "September",
year = "2020",
doi = "10.1016/j.poly.2020.114692",
issn = "0277-5387",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20200701-145206963",
note = "© 2020 Elsevier Ltd. \n\nReceived 4 December 2019, Accepted 24 June 2020, Available online 30 June 2020.",
revision_no = "9",
abstract = "The UV-visible absorption and luminescence spectra of [Ru(diimine)(CN)₄]²⁻ derivatives have been tuned over wide ranges through variations in solvent, substituents on the diimine ligand, and boronation of the cyanide ligands. Trifluoromethyl substitution at the 4 and 4′ positions of the diimine induces red shifts in metal-to-ligand charge-transfer (MLCT) absorption and luminescence bands. Boronation of the cyanide ligands produces substantial blue shifts in MLCT energies. The combination of diimine trifluoromethylation and cyanide boronation produces MLCT blue shifts that are about 75% as large as those produced by boronation alone.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/107241,
title ="Solar photochemistry",
author = "Gray, Harry B.",
pages = "PRES-0005",
month = "August",
year = "2020",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20201221-125027615",
note = "© 2020 American Chemical Society.",
revision_no = "8",
abstract = "Solar-driven water splitting to produce renewable fuels and materials is one of the holy grails of 21st century chem. We\nhave been working on methods for the synthesis of robust mixed-metal catalysts for the oxidn. of water and other inert\nsubstrates.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/104347,
title ="A Super-Oxidized Radical Cationic Icosahedral Boron Cluster",
author = "Stauber, Julia M. and Schwan, Josef",
journal = "Journal of the American Chemical Society",
volume = "142",
number = "30",
pages = "12948-12953",
month = "July",
year = "2020",
doi = "10.1021/jacs.0c06159",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20200713-085326752",
note = "© 2020 American Chemical Society. \n\nReceived: June 8, 2020; Published: July 10, 2020. \n\nThis work was supported as part of the Center for Synthetic Control Across Length-scales for Advancing Rechargeables (SCALAR), an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES) under Award No. DE-SC0019381 (A.M.S. and K.A.S. synthesis and characterization; T.F.M., computational work and theory). A.M.S. is a Research Corporation for Science Advancement (RCSA) Cottrell Scholar and a Dreyfus Foundation Camille Dreyfus Teacher-Scholar. Acknowledgment is made to the donors of The American Chemical Society Petroleum Research Fund for funding work in the H.B.G. lab (J.S. and H.B.G.). Work in the Beckman Institute at Caltech was supported by the Arnold and Mabel Beckman Foundation (B.J.M., J.R.W.). X.Z. acknowledges the Agency for Science, Technology and Research (Singapore) for an A*STAR fellowship. X.Z. and T.F.M. acknowledge the computational resources from the Extreme Science and Engineering Discovery Environment (XSEDE) Bridges computer at the Pittsburgh Supercomputing Center through allocation TG-MCB160013. A.J.M. acknowledges support through a postdoctoral fellowship from the Resnick Sustainability Institute at Caltech. D.J. acknowledges the UCLA Graduate Division for the Dissertation Year Fellowship. The National Science Foundation (NSF-1531940) and the Dow Next Generation Educator Fund are acknowledged for EPR facility support. \n\nThe authors declare the following competing financial interest(s): UCLA has patents on several compounds reported in this work from which A.M.S. and current/former co-workers may receive royalty payments. The Cs₂[B₁₂(OH)₁₂] salt (Catalog #902209) is commercially available through the MilliporeSigma catalog.",
revision_no = "20",
abstract = "While the icosahedral closo-[B₁₂H₁₂]²⁻ cluster does not display reversible electrochemical behavior, perfunctionalization of this species via substitution of all 12 B–H vertices with alkoxy or benzyloxy (OR) substituents engenders reversible redox chemistry, providing access to clusters in the dianionic, monoanionic, and neutral forms. Here, we evaluated the electrochemical behavior of the electron-rich B₁₂(O-3-methylbutyl)₁₂ (1) cluster and discovered that a new reversible redox event that gives rise to a fourth electronic state is accessible through one-electron oxidation of the neutral species. Chemical oxidation of 1 with [N(2,4-Br₂C₆H₃)₃]·⁺ afforded the isolable [1]·⁺ cluster, which is the first example of an open-shell cationic B₁₂ cluster in which the unpaired electron is proposed to be delocalized throughout the boron cluster core. The oxidation of 1 is also chemically reversible, where treatment of [1]·⁺ with ferrocene resulted in its reduction back to 1. The identity of [1]·⁺ is supported by EPR, UV–vis, multinuclear NMR (¹H, ¹¹B), and X-ray photoelectron spectroscopic characterization.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/104953,
title ="Protein-coated corrole nanoparticles for the treatment of prostate cancer cells",
author = "Soll, Matan and Chen, Qiu-Cheng",
journal = "Cell Death Discovery",
volume = "6",
pages = "Art. No. 67",
month = "July",
year = "2020",
doi = "10.1038/s41420-020-0288-x",
issn = "2058-7716",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20200813-094027297",
note = "© 2020 The Author(s). Open Access. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. \n\nReceived: 11 December 2019. Revised: 18 May 2020. Accepted: 28 May 2020. Published online: 28 July 2020. \n\nThe work by HBG at the California Institute of Technology was supported by NIH R01DK019038. Research at the City of Hope (J.T.) and at Technion (Z.G.) was supported by an International Collaboration Grant from the Jacki and Bruce Barron Cancer Research Scholars Program, a partnership of the ICRF and City of Hope funded by the Harvey L. Miller Family Foundation. \n\nThe authors declare no conflict of interests.",
revision_no = "18",
abstract = "Development of novel therapeutic strategies to eradicate malignant tumors is of paramount importance in cancer research. In a recent study, we have introduced a facile protocol for the preparation of corrole-protein nanoparticles (NPs). These NPs consist of a corrole-core coated with protein. We now report that a novel lipophilic corrole, (2)Ga, delivered as human serum albumin (HSA)-coated NPs, displayed antineoplastic activity towards human prostate cancer DU-145 cells. Cryo-TEM analysis of these NPs revealed an average diameter of 50.2\u2009±\u20098.1\u2009nm with a spherical architecture exhibiting low polydispersity. In vitro cellular uptake of (2)Ga/albumin NPs was attributable to rapid internalization of the corrole through ligand binding-dependent extracellular release and intercalation of the corrole cargo into the lipid bilayer of the plasma membrane. This finding is in contrast with a previously reported study on corrole-protein NPs that displayed cellular uptake via endocytosis. Investigation of the non-light-induced mechanism of action of (2)Ga suggested the induction of necrosis through plasma membrane destabilization, impairment of calcium homeostasis, lysosomal stress and rupture, as well as formation of reactive oxygen species (ROS). (2)Ga also exhibited potent light-induced cytotoxicity through ROS generation. These findings demonstrate a rapid cellular uptake of (2)Ga/protein NPs along with targeted induction of tumor cell necrosis.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/104465,
title ="Does Tyrosine Protect S. Coelicolor Laccase from Oxidative Degradation?",
author = "Kielb, Patrycja J. and Gray, Harry B.",
month = "July",
year = "2020",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20200720-145555975",
note = "Licence: CC BY-NC-ND 4.0. \n\nSubmitted date: 18/07/2020; Posted date: 20/07/2020. \n\nFunding: National Institute of Diabetes and Digestive and Kidney Diseases. \n\nAuthors declare no conflict of interest.",
revision_no = "12",
abstract = "We have investigated the roles of tyrosine (Tyr) and tryptophan (Trp) residues in the four-electron reduction of oxygen catalyzed by Streptomyces coelicolor laccase (SLAC). During normal enzymatic turnover in laccases, reducing equivalents are delivered to a type 1 Cu center (Cu_(T1)) and then are transferred over 13 Å to a trinuclear Cu site (TNC: (Cu_(T3))₂Cu_(T2)) where O₂ reduction occurs. The TNC in SLAC is surrounded by a large cluster of Tyr and Trp residues that can provide reducing equivalents when the normal flow of electrons is disrupted. Canters and coworkers have shown that when O₂ reacts with a reduced SLAC variant lacking the CuT1 center, a Tyr108· radical near the TNC forms rapidly. We have found that ascorbate reduces the Tyr108· radical in wild-type SLAC about 10 times faster than it reacts with the Cu_(T1)²⁺ center, possibly owing to radical transfer along a Tyr/Trp chain. Aerobic oxidation of two reduced SLAC mutants (Y108F and W132F) leads to the formation of a long-lived (~15 min) Tyr· radical with distinct absorption at 408 nm. The diffusion of redox equivalents away from the primary enzymatic pathway in SLAC may indicate a poorly optimized enzyme or a mechanism to protect against protein damage.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/104073,
title ="Electronic Structures, Spectroscopy, and Electrochemistry of [M(diimine)(CN-BR₃)₄]²⁻ (M = Fe, Ru; R = Ph, C₆F₅) Complexes",
author = "Ngo, Danh X. and Del Ciello, Sarah A.",
journal = "Inorganic Chemistry",
volume = "59",
number = "14",
pages = "9594-9604",
month = "July",
year = "2020",
doi = "10.1021/acs.inorgchem.0c00632",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20200626-103612516",
note = "© 2020 American Chemical Society. \n\nReceived: February 28, 2020; Published: June 25, 2020. \n\nWe thank Jay Winkler for help in interpretation of transient absorption spectra. Larry Henling and Mike Takase provided invaluable assistance in collection and refinement of X-Ray crystal structures. We acknowledge the X-ray Crystallography Facility in the Beckman Institute at Caltech and the Dow Next Generation Instrumentation Grant for X-ray structure collection. We thank David van der Velde for assistance in NMR interpretation. Calculations were made on the Caltech High Performance Cluster, partially supported by a grant from the Gordon and Betty Moore Foundation. \n\nAccession Codes: CCDC 1986320, 1986326–1986327, and 1986331 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing data_request@ccdc.cam.ac.uk, or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033. \n\nThis work was supported by the National Science Foundation (CHE-1763429). Additional funding was provided by an Arthur A. Noyes SURF Fellowship (D.X.N.) and the Beckman Institute Laser Resource Center supported by the Arnold and Mabel Beckman Foundation. \n\nThe authors declare no competing financial interest.",
revision_no = "23",
abstract = "Complexes with the formula [M(diimine)(CN-BR₃)₄]²⁻, where diimine = bipyridine (bpy), phenanthroline (phen), 3,5-trifluoromethylbipyridine (flpy), R = Ph, C₆F₅, and M = Fe^(II), Ru^(II), were synthesized and characterized by X-ray crystal structure analysis, UV–visible spectroscopy, IR spectroscopy, and voltammetry. Three highly soluble complexes, [Fe^(II)(bpy)(CN-B(C₆F₅)₃)₄]²⁻, [Ru^(II)(bpy)(CN-B(C₆F₅)₃)₄]²⁻, and [Ru^(II)(flpy)(CN-B(C₆F₅)₃)₄]²⁻, exhibit electrochemically reversible redox reactions, with large potential differences between the bpy^(0/–) or flpy^(0/–) and MIII/II couples of 3.27, 3.52, and 3.19 V, respectively. CASSCF+NEVPT2 calculations accurately reproduce the effects of borane coordination on the electronic structures and spectra of cyanometallates.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/103106,
title ="Funneled angle landscapes for helical proteins",
author = "Kozak, John J. and Gray, Harry B.",
journal = "Journal of Inorganic Biochemistry",
volume = "208",
pages = "Art. No. 111091",
month = "July",
year = "2020",
doi = "10.1016/j.jinorgbio.2020.111091",
issn = "0162-0134",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20200511-125453032",
note = "© 2020 Published by Elsevier Inc. \n\nReceived 4 January 2020, Revised 14 April 2020, Accepted 16 April 2020, Available online 11 May 2020. \n\nWe thank Devarajan (Dave) Thirumalai for very helpful comments. Work at Caltech was supported by the NIH (DK019038) and the Arnold and Mabel Beckman Foundation. Support at Pomona College was provided by the Howard Hughes Medical Institute Research Program and a Sontag Research Fellowship Award.\n\nDeclaration of competing interest:\nThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.",
revision_no = "22",
abstract = "We use crystallographic data for four helical iron proteins (cytochrome c-b₅₆₂, cytochrome c′, sperm whale myoglobin, human cytoglobin) to calculate radial and angular signatures as each unfolds from the native state stepwise though four unfolded states. From these data we construct an angle phase diagram to display the evolution of each protein from its native state; and, in turn, the phase diagram is used to construct a funneled angle landscape for comparison with the topography of its folding energy landscape. We quantify the departure of individual helical and turning regions from the areal, angular profile of corresponding regions of the native state. This procedure allows us to identify the similarities and differences among individual helical and turning regions in the early stages of unfolding of the four helical heme proteins.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/103283,
title ="A colloquium on the status and challenges in science for decarbonizing our energy landscape",
author = "Eisenberg, Richard and Gray, Harry B.",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "117",
number = "23",
pages = "12541-12542",
month = "June",
year = "2020",
doi = "10.1073/pnas.2005221117",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20200518-132457628",
note = "© 2020 National Academy of Sciences. Published under the PNAS license. \n\nPNAS first published May 18, 2020. \n\nAuthor contributions: R.E., H.B.G., and G.W.C. wrote the paper. \n\nThe authors declare no competing interest. \n\nThis paper results from the Arthur M. Sackler Colloquium of the National Academy of Sciences, “Status and Challenges in Decarbonizing our Energy Landscape,” held October 10–12, 2018, at the Arnold and Mabel Beckman Center of the National Academies of Sciences and Engineering in Irvine, CA. NAS colloquia began in 1991 and have been published in PNAS since 1995. From February 2001 through May 2019 colloquia were supported by a generous gift from The Dame Jillian and Dr. Arthur M. Sackler Foundation for the Arts, Sciences, & Humanities, in memory of Dame Sackler’s husband, Arthur M. Sackler. The complete program and video recordings of most presentations are available on the NAS website at http://www.nasonline.org/decarbonizing.",
revision_no = "19",
abstract = "An Arthur M. Sackler Colloquium titled “Status and Challenges in Science for Decarbonizing our Energy Landscape” was held at the Arnold and Mabel Beckman Center in Irvine, California in October 2018. The papers that follow in this issue of PNAS (1–7) stem from that activity, which addressed a topic of compelling interest and importance to our community from a perspective often not addressed.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/99123,
title ="Addressing the challenge of carbon-free energy",
author = "Eisenberg, Richard and Gray, Harry B.",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "117",
number = "23",
pages = "12543-12549",
month = "June",
year = "2020",
doi = "10.1073/pnas.1821674116",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20191007-142915530",
note = "© 2019 National Academy of Sciences. Published under the PNAS license. \n\nEdited by David A. Weitz, Harvard University, Cambridge, MA, and approved August 19, 2019 (received for review April 4, 2019). PNAS first published October 7, 2019.\n\nR.E., H.B.G., and G.W.C. contributed equally to this work. \n\nAuthor contributions: R.E., H.B.G., and G.W.C. analyzed data and wrote the paper. \n\nThe authors declare no conflict of interest. \n\nThis paper results from the Arthur M. Sackler Colloquium of the National Academy of Sciences, “Status and Challenges in Decarbonizing our Energy Landscape,” held October 10–12, 2018, at the Arnold and Mabel Beckman Center of the National Academies of Sciences and Engineering in Irvine, CA. NAS colloquia began in 1991 and have been published in PNAS since 1995. From February 2001 through May 2019 colloquia were supported by a generous gift from The Dame Jillian and Dr. Arthur M. Sackler Foundation for the Arts, Sciences, & Humanities, in memory of Dame Sackler’s husband, Arthur M. Sackler. The complete program and video recordings of most presentations are available on the NAS website at http://www.nasonline.org/decarbonizing. \n\nThis article is a PNAS Direct Submission.",
revision_no = "19",
abstract = "This century will witness a major transformation in how energy is acquired, stored, and utilized globally. The impetus for this change comes from the deep impacts that both developed and developing societies have had on our planet’s environment during the past century, and the projections going forward of what will happen if we do not act transformatively within the next 2 decades. This paper describes the basis for a meeting held in October 2018 on the need for decarbonization in our energy landscape, and specifically the status and challenges of the science that provides the foundation for such technology. Within the realm of decarbonization in energy generation lies the science of solar energy conversion using new or improved photovoltaic materials and artificial photosynthesis for water splitting and other energy-storing reactions. The intimately related issue of renewable energy storage is being addressed with new strategies, materials, and approaches under current investigation and development. The need to improve the interactions between scientists working on these connected but separately considered challenges and on the transition of scientific achievement to practical application was also addressed, with specific efforts enumerated.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/102594,
title ="Isotopically Selective Quantification by UPLC-MS of Aqueous Ammonia at Submicromolar Concentrations Using Dansyl Chloride Derivatization",
author = "Yu, Weilai and Lewis, Nathan S.",
journal = "ACS Energy Letters",
volume = "5",
number = "5",
pages = "1532-1536",
month = "May",
year = "2020",
doi = "10.1021/acsenergylett.0c00496",
issn = "2380-8195",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20200417-094556803",
note = "© 2020 American Chemical Society. \n\nReceived: March 2, 2020; Accepted: April 6, 2020; Published: April 16, 2020. \n\nAcknowledgement is made to the donors of The American Chemical Society Petroleum Research Fund for partial support of this research. This work was also supported by the Office of Science of the U.S. Department of Energy under Award Number DE-SC0004993. N.F.D. is grateful to the Linde Center for support. The Environmental Analysis Center is grateful for support from the Beckman Institute at Caltech. Dr. Fabai Wu and Prof. Victoria Orphan are thanked for providing the ¹⁵NH₄Cl standard sample. Mr. Christopher Kenseth is thanked for assistance with UPLC-MS analysis. Dr. Yuanlong Huang is thanked for fruitful discussions. \n\nViews expressed in this Viewpoint are those of the authors and\nnot necessarily the views of ACS. \n\nThe authors declare no competing financial interest.",
revision_no = "23",
abstract = "Ammonia (NH₃) is essential for food production and is commercially synthesized from nitrogen (N₂) and hydrogen (H₂) using the Haber–Bosch process. Enormous amounts of ammonia are made every year in a reaction that requires high temperatures and pressures, with the Haber–Bosch accounting for ∼1.6% of total annual global energy consumption. Electrocatalysts are also being explored to convert in an environmentally friendly manner N₂ to NH₃ at ambient temperature and pressure. ",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/102207,
title ="Enhanced Synthetic Access to Tris-CF₃-Substituted Corroles",
author = "Yadav, Pinky and Khoury, Sally",
journal = "Organic Letters",
volume = "22",
number = "8",
pages = "3119-3122",
month = "April",
year = "2020",
doi = "10.1021/acs.orglett.0c00879",
issn = "1523-7060",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20200331-133818896",
note = "© 2020 American Chemical Society. \n\nReceived: March 9, 2020; Published: March 31, 2020. \n\nThis research was supported by the Israel Science Foundation (to ZG) and the United States National Institutes of Health (R01 DK019038 to HBG). \n\nAuthor Contributions: P.Y. and S.K. made equal contributions. \n\nThe authors declare no competing financial interest.",
revision_no = "18",
abstract = "Separate focus on the oligomerization and oxidative cyclization steps required for the synthesis of 5,10,15-tris(trifluoromethyl)corrole revealed [bis(trifluoroacetoxy)iodo]benzene (PIFA) as a superior alternative oxidant. Under optimized conditions, the pure free-base corrole was obtained with a 6-fold increase in chemical yield and an 11-fold rise in isolated material per synthesis. The corresponding gallium(III) and manganese(III) complexes were isolated by adding the appropriate metal salt prior to corrole purification.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/101922,
title ="Hole Hopping through Cytochrome P450",
author = "Sørensen, Mette L. H. and Sanders, Brian C.",
journal = "Journal of Physical Chemistry B",
volume = "124",
number = "15",
pages = "3065-3073",
month = "April",
year = "2020",
doi = "10.1021/acs.jpcb.9b09414",
issn = "1520-6106",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20200316-150527143",
note = "© 2020 American Chemical Society. \n\nReceived: October 7, 2019; Revised: March 15, 2020; Published: March 16, 2020. \n\nResearch reported in this publication was supported by the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health under Award Number R01DK019038. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. T.H. thanks the Lundbeck Foundation for generous financial support. B.C.S. was supported by the National Institutes of Health under Award Number F32GM123639-01 and in part by the U.S. Department of Energy (DOE), Oak Ridge National Laboratory Programmatic Fund, during manuscript preparation. \n\nAuthor Contributions: M.L.H.S. and B.C.S. contributed equally to this work. \n\nThe authors declare no competing financial interest.",
revision_no = "20",
abstract = "High-potential iron–oxo species are intermediates in the catalytic cycles of oxygenase enzymes. They can cause heme degradation and irreversible oxidation of nearby amino acids. We have proposed that there are protective mechanisms in which hole hopping from oxidized hemes through tryptophan/tyrosine chains generates a surface-exposed amino-acid oxidant that could be rapidly disarmed by reaction with cellular reductants. In investigations of cytochrome P450_(BM3), we identified Trp96 as a critical residue that could play such a protective role. This Trp is cation−π paired with Arg398 in 81% of mammalian P450s. Here we report on the effect of the Trp/Arg cation−π interaction on Trp96 formal potentials as well as on electronic coupling strengths between Trp96 and the heme both for wild type cytochrome P450 and selected mutants. Mutation of Arg398 to His, which decreases the Trp96 formal potential, increases Trp-heme electronic coupling; however, surprisingly, the rate of phototriggered electron transfer from a Ru-sensitizer (through Trp96) to the P450BM3 heme was unaffected by the Arg398His mutation. We conclude that Trp96 has moved away from Arg398, suggesting that the protective mechanism for P450s with this Trp-Arg pair is conformationally gated.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/101354,
title ="Electronic structures and redox properties of boronated cyanometalates",
author = "Gray, Harry B. and McNicholas, Brendon James",
pages = "CATL-0122",
month = "March",
year = "2020",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20200219-075302879",
note = "© 2020 American Chemical Society.",
revision_no = "8",
abstract = "We have synthesized and structurally characterized homoleptic and heteroleptic tris(pentafluorophenyl)borane adducts of iron, ruthenium, and osmium cyanides. The III/II formal potentials are more than 2.0 V higher in the boronated octahedral complexes; and, in the boronated heteroleptic complexes, the MLCT excited triplets are relatively long-lived (he MLCT absorptions are dramatically blue-shifted).The boronated homoleptic complexes, which are electrochem. reversible, exhibit energy efficiencies of 80% in nonaq. redox flow batteries; and the boronated heteroleptic complexes exhibit cell potentials over 3.0 V in sym-rf batteries.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/101360,
title ="Kinetic and thermodynamic studies on T. thermophilus laccase catalysis",
author = "Shin, Jieun and Gray, Harry B.",
pages = "INOR-0605",
month = "March",
year = "2020",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20200219-081333782",
note = "© 2020 American Chemical Society.",
revision_no = "10",
abstract = "Multicopper oxidases (MCOs) are lignin degrading enzymes with four copper sites involved in their catalysis. The consensus mechanism suggests that substrate oxidn. occurs near a type 1 Cu center (CuT1), followed by long-range electron transfer to a trinuclear Cu center (TNC) where O₂ is reduced to H₂O. Although laccases are capable of aerobic oxidn. of lignin as their primary function, the potential of CuT1 (E°(Cu²⁺/⁺) ≈0.5 V vs. NHE, pH 5.5) is as much as 0.5 V lower than that expected for one-electron oxidn. of polyphenolic substrates. Investigations on redox-active residues crit. for enzyme catalysis as well as reactive intermediates are crucial for elucidating this potential discrepancy and the mechanistic details of substrate oxidn. Our study focused on the MCO from a thermophilic bacterium, Thermus thermophilus HB27 (T. thermophilus Laccase) in particular (Figure 1), which is stable and active even above 90°C. Thus, thermodn. parameters assocd. with the enzyme's thermostability and improved activity at elevated temps. are of special importance. Approaches to enhancing our understanding of how the enzyme has evolved to utilize O₂ to degrade lignin from recalcitrant lignocellulosic substrates will be useful for developing environmentally friendly biocatalysts.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/101367,
title ="Redox chemistry of metal oxos",
author = "Gray, Harry B.",
pages = "INOR-0090",
month = "March",
year = "2020",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20200219-085102421",
note = "© 2020 American Chemical Society.",
revision_no = "9",
abstract = "I will discuss the roles metal oxos play in two of the most important chem. reactions on planet Earth, water oxidn. to oxygen and hydrocarbon oxygenation to alcs.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/101372,
title ="Spectroscopy and photophysics of tungsten arylisocyanides",
author = "Gray, Harry B. and Fajardo, Javier",
pages = "INOR-0444",
month = "March",
year = "2020",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20200219-101133498",
note = "© 2020 American Chemical Society.",
revision_no = "8",
abstract = "We report the structures and spectroscopic properties of third generation tungsten(0) arylisocyanides. These complexes exhibit very intense absorptions and strikingly bright emissions in the visible region. The lowest electronic excited states, some with microsecond lifetimes, are very strong reductants. The complexes also have large two-photon absorption cross sections (> 1000 GMs), enabling the study of near-IR-triggered photoredox chem.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/100871,
title ="Stability/activity tradeoffs in Thermus thermophilus HB27 laccase",
author = "Shin, Jieun and Gray, Harry B.",
journal = "Journal of Biological Inorganic Chemistry",
volume = "25",
number = "3",
pages = "233-238",
month = "March",
year = "2020",
doi = "10.1007/s00775-020-01754-7",
issn = "0949-8257",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20200123-100835510",
note = "© 2020 Society for Biological Inorganic Chemistry (SBIC). \n\nReceived: 4 November 2019; Accepted: 25 December 2019. First Online: 22 January 2020. \n\nResearch reported in this publication was supported by the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health under award number R01DK019038. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. Additional support for this research was provided by the Arnold and Mabel Beckman Foundation.",
revision_no = "21",
abstract = "We report the temperature dependence of the formal potential of type 1 copper (Cu_(T1)) in Thermusthermophilus HB27 laccase. Employing [Ru(NH₃)₄ (bpy)](PF₆)₂ (0.505 vs. NHE) as the redox titrant, we found that the Cu_(T1)^(2+/+) potential decreased from approximately 480 to 420 mV (vs. NHE) as the temperature was raised from 20 to 65 °C. Of importance is that the ΔS_(rc)° of\u2009−\u2009120 J mol⁻¹ K⁻¹ is substantially more negative than those for other blue copper proteins. We suggest that the highly unfavorable reduction entropy is attributable to Cu_(T1) inaccessibility to the aqueous medium. Although the active site residues are buried, which is critical for maintaining thermostability, the flexibility around Cu_(T1) is maintained, allowing enzyme activity at ambient temperature.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/102267,
title ="Stability/activity tradeoffs in Thermusthermophilus HB27 laccase",
author = "Shin, Jieun and Gray, Harry B.",
journal = "Journal of Biological Inorganic Chemistry",
volume = "25",
number = "2",
pages = "233-238",
month = "March",
year = "2020",
doi = "10.1007/s00775-020-01754-7",
issn = "0949-8257",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20200402-121027505",
note = "© 2020 Springer Nature Switzerland AG. \n\nReceived 04 November 2019; Accepted 25 December 2019; Published 22 January 2020. \n\nResearch reported in this publication was supported by the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health under award number R01DK019038. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. Additional support for this research was provided by the Arnold and Mabel Beckman Foundation.",
revision_no = "12",
abstract = "We report the temperature dependence of the formal potential of type 1 copper (Cu_(T1)) in Thermusthermophilus HB27 laccase. Employing [Ru(NH₃)₄ (bpy)](PF₆)₂ (0.505 vs. NHE) as the redox titrant, we found that the Cu_(T1)^(2+/+) potential decreased from approximately 480 to 420 mV (vs. NHE) as the temperature was raised from 20 to 65 °C. Of importance is that the ΔS_(rc)° of\u2009−\u2009120 J mol⁻¹ K⁻¹ is substantially more negative than those for other blue copper proteins. We suggest that the highly unfavorable reduction entropy is attributable to CuT1 inaccessibility to the aqueous medium. Although the active site residues are buried, which is critical for maintaining thermostability, the flexibility around Cu_(T1) is maintained, allowing enzyme activity at ambient temperature.",
}
@book_section {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/101523,
title ="Electron Transfer Proteins",
author = "Warren, Jeffrey J. and Gray, Harry B.",
month = "February",
year = "2020",
doi = "10.1016/b978-0-12-409547-2.14831-0",
isbn = "978-0-12-409547-2",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20200225-083801926",
note = "© 2020 Elsevier Inc.\n\nAvailable online 22 February 2020.\n",
revision_no = "6",
abstract = "Biological electron carriers are central to life. Numerous technological advances have engendered rapid growth in the field between 2003 and 2018. Special emphasis is put on key advances in this 15 year time frame. Our understanding of how electrons move between and through proteins has matured. We are now at a point where predictions of redox properties and behavior are possible. Particular emphasis is placed on iron (heme and non-heme) and copper proteins.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/100718,
title ="Light-Induced Nanosecond Relaxation Dynamics of Rhenium-Labeled Pseudomonas aeruginosa Azurins",
author = "Pospíšil, Petr and Sýkora, Jan",
journal = "Journal of Physical Chemistry B",
volume = "124",
number = "5",
pages = "788-797",
month = "February",
year = "2020",
doi = "10.1021/acs.jpcb.9b10802",
issn = "1520-6106",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20200114-133306708",
note = "© 2020 American Chemical Society. \n\nReceived: November 18, 2019; Revised: January 2, 2020; Published: January 14, 2020. \n\nThis work was supported by the Czech Science Foundation (GAČR) grant 17-011375, the Czech Ministry of Education (MŠMT) grant LTAUSA18026, the EPSRC grant (UK) EP/R029687/1, and the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health under award number R01DK019038. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. Yuling Sheng (Caltech) is acknowledged for her help with protein preparation. \n\nThe authors declare no competing financial interest.",
revision_no = "19",
abstract = "Time-resolved phosphorescence spectra of Re(CO)₃(dmp)⁺ and Re(CO)₃ (phen)⁺ chromophores (dmp = 4,7-dimethyl-1,10-phenanthroline, phen = 1,10-phenanthroline) bound to surface histidines (H83, H124, and H126) of Pseudomonas aeruginosa azurin mutants exhibit dynamic band maxima shifts to lower wavenumbers following 3-exponential kinetics with 1–5 and 20–100 ns major phases and a 1.1–2.5 μs minor (5–16%) phase. Observation of slow relaxation components was made possible by using an organometallic Re chromophore as a probe whose long phosphorescence lifetime extends the observation window up to ∼3 μs. Integrated emission-band areas also decay with 2- or 3-exponential kinetics; the faster decay phase(s) is relaxation-related, whereas the slowest one [360–680 ns (dmp); 90–140 ns (phen)] arises mainly from population decay. As a result of shifting bands, the emission intensity decay kinetics depend on the detection wavelength. Detailed kinetics analyses and comparisons with band-shift dynamics are needed to disentangle relaxation and population decay kinetics if they occur on comparable timescales. The dynamic phosphorescence Stokes shift in Re-azurins is caused by relaxation motions of the solvent, the protein, and solvated amino acid side chains at the Re binding site in response to chromophore electronic excitation. Comparing relaxation and decay kinetics of Re(dmp)124K122Cu^(II) and Re(dmp)124W122Cu^(II) suggests that electron transfer (ET) and relaxation motions in the W122 mutant are coupled. It follows that nanosecond and faster photo-induced ET steps in azurins (and likely other redox proteins) occur from unrelaxed systems; importantly, these reactions can be driven (or hindered) by structural and solvational dynamics.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/100455,
title ="EPR spectroscopy of iron- and nickel-doped [ZnAl]-layered double hydroxides: modeling active sites in heterogeneous water oxidation catalysts",
author = "Sayler, Richard I. and Hunter, Bryan M.",
journal = "Journal of the American Chemical Society",
volume = "142",
number = "4",
pages = "1838-1845",
month = "January",
year = "2020",
doi = "10.1021/jacs.9b10273",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20200102-104558690",
note = "© 2019 American Chemical Society. \n\nReceived: September 23, 2019; Published: December 31, 2019. \n\nThis work was supported by the NSF CCI Solar Fuels Program (CHE-1305124) and the Arnold and Mabel Beckman Foundation. \n\nThe authors declare no competing financial interest.",
revision_no = "20",
abstract = "Iron-doped nickel layered double hydroxides (LDHs) are among the most active heterogeneous water oxidation catalysts. Due to inter-spin interactions, however, the high density of magnetic centers results in line-broadening in magnetic resonance spectra. As a result, gaining atomic-level insight into the catalytic mechanism via electron paramagnetic resonance (EPR) is not generally possible. To circumvent spin-spin broadening, iron and nickel atoms were doped into non-magnetic [ZnAl]-LDH materials and the coordination environments of the isolated Fe(III) and Ni(II) sites were characterized. Multifrequency EPR spectroscopy identified two distinct Fe(III) sites (S = 5/2) in [Fe:ZnAl]-LDH. Changes in zero field splitting (ZFS) were induced by dehydration of the material, revealing that one of the Fe(III) sites is solvent-exposed (i.e. at an edge, corner, or defect site). These solvent-exposed sites feature an axial ZFS of 0.21 cm⁻¹ when hydrated. The ZFS increases dramatically upon dehydration (to -1.5 cm⁻¹), owing to lower symmetry and a decrease in the coordination number of iron. The ZFS of the other (“inert”) Fe(III) site maintains an axial ZFS of 0.19-0.20 cm⁻¹ under both hydrated and dehydrated conditions. We observed a similar effect in [Ni:ZnAl]-LDH materials; notably, Ni(II) (S = 1) atoms displayed a single, small ZFS (±0.30 cm⁻¹) in hydrated material, whereas two distinct Ni(II) ZFS values (±0.30 and ±1.1 cm⁻¹) were observed in the dehydrated samples. Although the magnetically-dilute materials were not active catalysts, the identification of model sites in which the coordination environments of iron and nickel were particularly labile (e.g. by simple vacuum drying) is an important step towards identifying sites in which the coordination number may drop spontaneously in water, a probable mechanism of water oxidation in functional materials.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/99736,
title ="Electronic Structure of Tetracyanonickelate(II)",
author = "Oppenheim, Julius J. and McNicholas, Brendon J.",
journal = "Inorganic Chemistry",
volume = "58",
number = "22",
pages = "15202-15206",
month = "November",
year = "2019",
doi = "10.1021/acs.inorgchem.9b02135",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20191107-105330295",
note = "© 2019 American Chemical Society. \n\nReceived: July 17, 2019; Published: November 7, 2019. \n\nTime on a computing cluster was provided by the Beckman Institute Materials and Process Simulation Center; absorption spectroscopy was performed in the BI Laser Center (with assistance from Jay Winkler). We thank Garnet Chan, Daniel Weitekamp, Thomas Gallup, Christopher Lamartina, Jonathan Chan, and Kaitlyn Takata for helpful discussions. Our work was supported by NSF CHE-1763429. The authors also appreciate and acknowledge a quote given in a lecture at the ICCC meeting in Vienna in 1964 by one of the authors of this paper (H.B.G.), where he announced: “As there are so many square planar d-orbital energy orderings in the literature, one must be correct, so all we need to do is to find who found it!” \n\nThe authors declare no competing financial interest.",
revision_no = "19",
abstract = "Tetracyanonickelate(II) has been a poster child of ligand field theory for several decades. We have revisited the literature assignments of the absorption spectrum of [Ni(CN) ₄]²⁻ and the calculated ordering of orbitals with metal d character. Using low-temperature single-crystal absorption spectroscopy and accurate ab initio and density functional quantum mechanical methods (NEVPT2-CASSCF, EOM-CCSD, TD-DFT), we find an ordering of the frontier d- and p-orbitals of xy < xz, yz < z² < z < x²–y² < x, y and assign the d-d bands in the absorption spectrum to ¹A_(1g) → ³B_(1g) < ³E_g < ³A_(2g) < ¹B_(1g) < ¹E_g < ¹A_(2g). While differing from all previous interpretations, our assignments accord with an MO model in which strong π-backbonding in the plane of the molecule stabilizes d_(xy) more than out-of-plane bonding stabilizes d_(xz) and d_(yz).",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/98854,
title ="Mentoring: Reflections and Suggestions",
author = "Gray, Harry B.",
journal = "ACS Central Science",
volume = "5",
number = "9",
pages = "1475-1476",
month = "September",
year = "2019",
doi = "10.1021/acscentsci.9b00840",
issn = "2374-7943",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20190925-110648119",
note = "© 2019 American Chemical Society. This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes. \n\nPublished: September 25, 2019.",
revision_no = "12",
abstract = "I have been enormously lucky in my 58 years of working with students and postdocs. A great many members of the Gray Nation have been successful in careers in academia, industry, and government. Mark Wrighton, one of my first Caltech students, just retired from his position as Chancellor at Washington University St. Louis. (See the accompanying editorial, DOI 10.1021/acscentsci.9b00841.) Mark made transformational changes at WUSTL during his 24-year tenure. Five others also have led major universities, and over a hundred are provosts, deans, and professors in the USA, Canada, UK, Denmark, Sweden, Germany, the Czech Republic, Italy, South Korea, Japan, Australia, Taiwan, Hong Kong, and China. Can I take credit for their contributions to the science enterprise? Did my mentoring make a difference? I would like to think so!",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/98578,
title ="Stereochemistry of residues in turning regions of helical proteins",
author = "Kozak, John J. and Gray, Harry B.",
journal = "Journal of Biological Inorganic Chemistry",
volume = "24",
number = "6",
pages = "879-888",
month = "September",
year = "2019",
doi = "10.1007/s00775-019-01696-9",
issn = "0949-8257",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20190911-131606828",
note = "© 2019 Society for Biological Inorganic Chemistry (SBIC). \n\nReceived: 26 June 2019; Accepted: 2 August 2019; First Online: 11 September 2019. \n\nWork at Caltech was supported by the National Institutes of Health (DK-019038 to HBG).",
revision_no = "17",
abstract = "We have developed a geometrical approach to quantify differences in the stereochemistry of α-helical and turning regions in four iron proteins. Two spatial signatures are used to analyze residue coordinate data for each protein; and a third is employed to analyze amino-acid molecular volume data. The residue-by-residue analysis of the results, taken together with the finding that two major factors stabilize an α-helix (minimization of side-chain steric interference and intrachain H-bonding), lead to the conclusion that certain residues are preferentially selected for α-helix formation. In the sequential, de novo synthesis of a turning region, residues are preferentially selected such that the overall molecular volume profile (representing purely repulsive, excluded-volume effects) spans a small range Δ of values (Δ\u2009=\u200939.1 Å^3) relative to the total range that could be spanned (Δ\u2009=\u2009167.7 Å^3). It follows that excluded-volume effects are of enormous importance for residues in helical regions as well as those in adjacent turning regions. Once steric effects are taken into account, down-range attractive interactions between residues come into play in the formation of α-helical regions. The geometry of α-helices can be accommodated by conformational changes in less-structured turning regions of a polypeptide, thereby producing a globally optimized (native) protein structure.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/96698,
title ="Photooxidative Generation of Dodecaborate-Based Weakly Coordinating Anions",
author = "Axtell, Jonathan C. and Messina, Marco S.",
journal = "Inorganic Chemistry",
volume = "58",
number = "16",
pages = "10516-10526",
month = "August",
year = "2019",
doi = "10.1021/acs.inorgchem.9b00935",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20190625-112728745",
note = "© 2019 American Chemical Society. \n\nReceived: March 30, 2019; Published: June 25, 2019. \n\nSpecial Issue: Celebrating the Year of the Periodic Table: Emerging Investigators in Inorganic Chemistry. \n\nThe authors acknowledge Aayush Gupta (UIC) for preliminary computational work. M.S.M. was supported by NSF Bridge-to-Doctorate (Grant HRD-1400789) and Predoctoral Fellowship (Grant DGE-0707424) and the UCLA Christopher S. Foote Fellowship. H.B.G. was supported by the NSF (Grants CHE-1305124 and CHE-1763429). A.N.A. was supported by NSF CAREER Award CHE-1351968. Research pertaining to synthesis of the cluster compounds performed at UCLA was supported as part of the Synthetic Control Across Length-scales for Advancing Rechargeables (SCALAR) and Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Award DE-SC0019381. A.M.S. thanks 3M for a Non-Tenured Faculty Award, the Alfred P. Sloan Foundation for a Fellowship in Chemistry, and the Research Corporation for Science Advancement (RCSA) for a Cottrell Scholar Award. M.D.S. acknowledges a Dr. Raymond and Dorothy Wilson Research Fellowship (UCLA). A.I.W. acknowledges the University of California, Los Angeles, Graduate Division, for a Dissertation Year Fellowship. \n\nThe authors declare the following competing financial interest(s): UCLA holds patents on materials used in this work, from which A.M.S. may receive royalty payments.",
revision_no = "26",
abstract = "Redox-active proanions of the type B_(12)(OCH_2Ar)_(12) [Ar = C_6F_5 (1), 4-CF_3C_6H_4 (2), 3,5-(CF_3)_2C_6H_3 (3)] are introduced in the context of an experimental and computational study of the visible-light-initiated polymerization of a family of styrenes. Neutral, air-stable proanions 1–3 were found to initiate styrene polymerization through single-electron oxidation under blue-light irradiation, resulting in polymers with number-average molecular weights (M_n) ranging from ∼6 to 100 kDa. Shorter polymer products were observed in the majority of experiments, except in the case of monomers containing 4-X (X = F, Cl, Br) substituents on the styrene monomer when polymerized in the presence of 1 in CH_2Cl_2. Only under these specific conditions are longer polymers (>100 kDa) observed, strongly supporting the formulation that reaction conditions significantly modulate the degree of ion pairing between the dodecaborate anion and cationic chain end. This also suggests that 1–3 behave as weakly coordinating anions (WCA) upon one-electron reduction because no incorporation of the cluster-based photoinitiators is observed in the polymeric products analyzed. Overall, this work is a conceptual realization of a single reagent that can serve as a strong photooxidant, subsequently forming a WCA.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/97366,
title ="Structures and Spectroscopic Properties of Metallocorrole Nanoparticles",
author = "Oppenheim, Julius and Gray, Mike H. B.",
journal = "Inorganic Chemistry",
volume = "58",
number = "15",
pages = "10287-10294",
month = "August",
year = "2019",
doi = "10.1021/acs.inorgchem.9b01441",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20190723-152249204",
note = "© 2019 American Chemical Society. \n\nReceived: May 17, 2019. Publication Date:July 23, 2019. \n\nResearch at Caltech was supported by the National Institutes of Health (DK-019038 to H.B.G.) and by an Ernest H. Swift Summer Undergraduate Research Fellowship (to J.O.). Research at the City of Hope (J.T.) and at Technion (Z.G.) was supported by an International Collaboration Grant from the Jacki and Bruce Barron Cancer Research Scholars Program, a partnership of the ICRF and City of Hope funded by the Harvey L. Miller Family Foundation. \n\nThe authors declare no competing financial interest. \n\nWe thank Zhuo Li at the City of Hope Electron Microscopy Core Facility for expert help with TEM experiments. Raman and IR spectra were collected (by M.H.B.G.) in the Beckman Institute Laser Resource Center, and time on the computing cluster (for J.O.) was provided by the Beckman Institute Materials and Process Simulation Center. The Arnold and Mabel Beckman Foundation supports the BI Laser and Materials Centers.",
revision_no = "22",
abstract = "In aqueous media, hydrophobic metallocorroles form nanoparticles that are potential theranostic anticancer agents. We have analyzed the electronic and Raman spectra of Al(III), Ga(III), and Au(III) corrole nanoparticles (and made comparisons with DFT-validated assignments of the IR spectra of corresponding monomers) in order to estimate the strengths of corrole–corrole electronic couplings in these assemblies. We find that these spectra are virtually unchanged upon aggregation, confirming that the intermolecular interactions in these nanoparticles are very weak.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/97755,
title ="Electron flow through proteins",
author = "Gray, Harry B.",
pages = "TOXI-0001",
month = "August",
year = "2019",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20190812-092528552",
note = "© 2019 American Chemical Society.",
revision_no = "10",
abstract = "Biol. electron transfers often occur between metal-contg. cofactors that are sepd. by very large mol. distances. Understanding the underlying physics and chem. of these electron transfer processes is the goal of much of the work in my lab. Employing laser flash-quench triggering methods, my coworkers and I have shown that 2-nm, coupling-limited Fe(II) to Ru(III) and Cu(I) to Ru(III) electron tunneling reactions in Ru-modified cytochromes and blue copper proteins occur on microsecond to nanosecond timescales. Redox equiv. can be transferred even longer distances by multistep tunneling (called hopping) through intervening tyrosines and tryptophans: notably, in our work on cytochrome P 450 and\nazurin, we have found that long-range hole hopping through intervening tryptophans can be orders of magnitude faster than single-step tunneling. Water interactions with tryptophan radical cation intermediates play key roles in promoting these hole hopping processes.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/97751,
title ="Reactive intermediates in multicopper oxidase catalysis",
author = "Shin, Jieun and Winkler, Jay Richmond",
pages = "INOR-0224",
month = "August",
year = "2019",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20190812-090439146",
note = "© 2019 American Chemical Society.",
revision_no = "10",
abstract = "In the past few decades, there has been growing interest in using metalloenzymes for improved biomass degrdn. and utilization. Multicopper oxidases (MCOs) are lignin degrading enzymes with four copper sites (Figure 1): a type 1 Cu center (Cu_(T1)) is involved in substrate oxidn. and electron transfer to a trinuclear Cu center (TNC) where O_2 is reduced to H_2O. The MCO of interest in this study is from the HB27 strain of the thermophilic bacterium Thermus thermophilus; it is stable and active even above 90°C. The enzyme is active for lignin oxidn., although the potential of Cu_(T1) (E°(Cu2+/+) = 0.53 V vs. NHE, pH 4.5) is lower than that expected for one-electron oxidn. of methoxy phenols. It is important, therefore, to elucidate the mechanistic details of substrate oxidn. by characterizing electron-transfer pathways and trapping reactive intermediates crit. for enzyme catalysis and function. Detn. of crit. residues for enzyme catalysis as well as gaining a deeper understanding of the redox chem. involved in the catalytic pathways of MCOs will facilitate the development of more energy-efficient and environmentally friendly biocatalysts.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/99594,
title ="Toxicity of Transition Metal Complex-based Nanophotoswitches in Retina",
author = "Yue, Lan and Shi, Yi",
journal = "Investigative Ophthalmology and Visual Science",
volume = "60",
number = "9",
pages = "Art. No. 4987",
month = "July",
year = "2019",
issn = "0146-0404",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20191031-140439364",
note = "© 2019 This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. \n\nThis abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.",
revision_no = "9",
abstract = "Purpose: Nanophotoswitches (NPSs) based on transition metal complexes offer a new tool for optical stimulation of neural activity in photoreceptor degenerated retina. We previously reported robust light-elicited neural activity in degenerate retinae exposed to ruthenium bipyridine based NPSs (Rubpy-C17) and its iridium analog (Irbpy-C17). Irbpy-C17 was developed as an alternative to Rubpy-C17 for the biosafety properties of the iridium complexes. Here we present a study of the toxicity of both NPSs in rodent retinae.\nMethods: Toxicity of Rubpy-C17 was tested in wildtype C57BL/6J mice and Irbpy-C17 in wildtype Long Evans rats. Animals were intravitreally injected with the test molecules (up to 50 µM) and sacrificed at different time points post injection: 3, 7, 14 and 28 days, respectively. Retinae were obtained, fixed and sliced for histological analysis immediately after animal euthanization. H&E staining was performed to examine morphological integrity of retina and TUNEL staining performed to detect apoptosis of retinal cells. For comparison, Ru(bpy)3]Cl2 injection and sham surgery were included for control.\nResults: H&E staining revealed no detectable sign of morphological or structural changes in the retinae after prolonged exposure to either Rubpy-C17 or Irbpy-C17 versus the control. There was no significant reduction in the thickness of different nuclear and plexiform retinal layers or the density of retinal neurons (p<0.05), nor was there evidence of significant aggregation of immune cells. TUNEL staining showed minimal occurrence of cell apoptosis in the NPS treated retinae, similar to the control (p<0.05). No longitudinal changes in either the morphology or the cell apoptosis was observed with the post injection time.\nConclusions: Overall our data did not find ocular toxicity associated with either the ruthenium or the iridium based NPSs within the concentration range tested. The results obtained with both complexes are similar to that obtained with the control molecule [Ru(bpy)3]Cl2, which lacks a membrane-anchoring 17 carbon chain attached to the bipyridine group, indicating that the inclusion of the carbon chain did not enable NPSs entry into the cells, nor did it cause apoptotic response. The present study provides new evidence of biosafety of our NPSs in rodent retinae, further encouraging developing NPS-based molecular retinal prosthesis to potentially restore high-acuity prosthetic vision in the blind.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/98361,
title ="(Nobel Laureate Signature Award for Graduate Education in Chemistry sponsored by Avantor Performance Materials) Trapping an iron(VI) water-\u200bsplitting intermediate in nonaqueous media",
author = "Hunter, Bryan Michael and Gray, Harry B.",
pages = "INOR-0522",
month = "April",
year = "2019",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20190830-085821545",
note = "© 2019 American Chemical Society.",
revision_no = "10",
abstract = "Understanding the mechanisms of highly-active earth-abundant water oxidn. electrocatalysts can guide the development of advanced water-splitting devices that convert renewable electricity to clean fuels and value-added products. Catalytic intermediates are difficult to isolate and characterize because they tend to be extremely transient and present at low concns. One approach to this problem is to slow down turnover by limiting the availability of the substrate. In cases where substrate and solvent are the same-such as in water oxidn.-the problem can be more complex. By dramatically limiting the availability of substrate (water and hydroxide) in nickel-iron catalyzed heterogeneous water oxidn., we have obsd. and characterized a high-valent iron intermediate. Orthogonal spectroscopies indicate that the intermediate contains iron in the rare 6+ oxidn. state. By considering this \"ferrate\" analog as a reactive intermediate, we can improve catalytic efficiency for water oxidn., and design new reactions to synthesize chems. and materials.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/94109,
title ="Electron flow through multicopper oxidases",
author = "Gray, Harry B. and Shin, Jieun",
pages = "INOR-0478",
month = "April",
year = "2019",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20190325-095621617",
note = "© 2019 American Chemical Society.",
revision_no = "10",
abstract = "We have investigated laser-triggered electron flow through Ru-modified Thermus thermophilus laccase. The results indicate that tryptophan and tyrosine residues near the trinuclear (type 2/type 3) copper site play a key role in the catalytic cycle of the enzyme.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/94108,
title ="Electronic structures and electrochemistry of boronated cyanometalates",
author = "Gray, Harry B. and McNicholas, Brendon",
pages = "INOR-0028",
month = "April",
year = "2019",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20190325-095401293",
note = "© 2019 American Chemical Society.",
revision_no = "10",
abstract = "We have synthesized and structurally characterized a series of organoboron-modified cyanometalates. The redn. potentials of these modified metal complexes span an exceptionally wide range, owing to variations in the electronic properties of the appended organoboron derivs. Selected highly sol. redox pairs exhibit electrochem. reversibility over a 2.1 V range in non-aq. solvents, making them excellent candidates for non-aq. redox flow batteries. Our model flow battery systems exhibit near unity Coulombic efficiencies and high energy efficiencies.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/94113,
title ="Electrons, holes, protons, and proteins",
author = "Winkler, Jay Richmond and Gray, Harry B.",
pages = "INOR-0100",
month = "April",
year = "2019",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20190325-102027071",
note = "© 2019 American Chemical Society.",
revision_no = "10",
abstract = "Most biol. redox transformations involve reagents with formal potentials in the ±1 V vs. NHE range. At the periphery of this potential window, proteins present a decidedly unsym. medium for electron transfer (ET). Whereas redn. of peptides and small arom. groups only proceeds at potentials more neg. than -2.5 V vs. NHE, one-electron oxidns. of arom. and sulfur-contg. amino-acids, as well as the peptide backbone itself, can occur at potentials in the 1.0-1.5 V vs. NHE range. This asymmetry suggests that proteins are superexchange mediators of ET in reactions of low-potential redox couples, but in high-potential redox transformations, proteins can support multistep tunneling (hopping). The sidechains of tyrosine (Tyr) and tryptophan (Trp) residues generate acidic radical cations upon oxidn. at high potentials, and several enzymes are known to utilize Tyr and Trp radicals in their catalytic mechanisms. Precise positioning of Tyr and Trp sidechains, and suitable proton acceptors, is required to provide effective redox function. A search of the protein structural database reveals that about one third of all proteins contain Tyr/Trp chains composed of three or more residues. Although these chains are distributed among all enzyme classes, they appear with greatest frequency in the oxidoreductases and hydrolases. Approx. half of the dioxygen-utilizing oxidoreductases have Tyr/Trp chain lengths of three or more residues. Our current efforts are aimed at elucidating the roles of Tyr and Trp radicals in the redox chem. of heme oxgenases and multicopper oxidases.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/94091,
title ="Hole hopping through tryptophan and tyrosine chains in proteins",
author = "Gray, Harry B.",
pages = "BIOL-0028",
month = "April",
year = "2019",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20190325-084510216",
note = "© 2019 American Chemical Society.",
revision_no = "9",
abstract = "Jay Winkler and I have found that most iron oxygenases have Trp/Tyr chains very near their active sites. We have suggested that an uncoupled high-valent iron-oxo enzyme intermediate would be reduced by hole transfer to the nearby residue in one of these chains. Electron transfer to the terminal residue in the chain could then protect the enzyme from oxidative degrdn.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/93902,
title ="Robust catalysts for solar-driven water splitting",
author = "Gray, Harry B.",
pages = "INOR-0014",
month = "April",
year = "2019",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20190318-074446824",
note = "© 2019 American Chemical Society.",
revision_no = "8",
abstract = "The efficient generation of mol. hydrogen from sunlight and water is one of the holy grails of 21st century chem.\nHydrogen is a clean, renewable fuel that could play a key role in meeting the world's skyrocketing demand for energy.\nInvestigators in the NSF CCI Solar Fuels Program have found that Ni-Mo nanopowders and metal phosphide\nnanocrystals have catalytic efficiencies near that of platinum for hydrogen evolution from water. We also have developed robust mixed-metal nanostructured catalysts for the prodn. of oxygen from water. There is an urgent need to find even better water oxidn. catalysts, as the protons and electrons liberated when oxygen is evolved are the fundamental particles required for sustainable energy storing reactions, not only for hydrogen prodn., but also for the conversion of nitrogen and carbon dioxide to fuels and chems.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/93221,
title ="Tuning the formal potential of ferrocyanide over a 2.1 V range",
author = "McNicholas, Brendon J. and Grubbs, Robert H.",
journal = "Chemical Science",
volume = "10",
number = "12",
pages = "3623-3626",
month = "March",
year = "2019",
doi = "10.1039/c8sc04972f",
issn = "2041-6520",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20190225-102849319",
note = "© 2019 The Royal Society of Chemistry. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. \n\nThe article was received on 08 Nov 2018, accepted on 17 Feb 2019 and first published on 21 Feb 2019. \n\nThe authors thank Mike Gray and Kimberly See for help in collecting solid-state Raman data. Mike Takase and Larry Henling provided invaluable assistance in collecting and refining X-ray crystallographic data. The authors also thank Brian Sanders and Wesley Kramer for helpful discussions. Supported by NSF (CCI CHE-1305124) and (CHE-1763429). Additional support was provided by the Arnold and Mabel Beckman Foundation. \n\nThere are no conflicts to declare.",
revision_no = "20",
abstract = "We report the synthesis and characterization of homoleptic borane adducts of hexacyanoferrate(II). Borane coordination blueshifts d–d transitions and CN IR and Raman frequencies. Control over redox properties is established with respect to borane Lewis acidity, reflected in peak anodic potential shifts per borane of +250 mV for BPh_3 and +350 mV for B(C_6F_5)_3. Electron transfer from [Fe(CN-B(C_6F_5)_3)_6]^(4−) to photogenerated [Ru(2,2′-bipyridine)_3]^(3+) is very rapid, consistent with voltammetry data. Coordination by Lewis acids provides an avenue for selective modification of the electronic structures and electrochemical properties of cyanometalates.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/92816,
title ="Hole Hopping Across a Protein–Protein Interface",
author = "Takematsu, Kana and Pospíšil, Petr",
journal = "Journal of Physical Chemistry B",
volume = "123",
number = "7",
pages = "1578-1591",
month = "February",
year = "2019",
doi = "10.1021/acs.jpcb.8b11982",
issn = "1520-6106",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20190211-081130545",
note = "© 2019 American Chemical Society. \n\nReceived: December 13, 2018; Revised: January 15, 2019; Published: January 23, 2019. \n\nThis work was supported by the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health under Award No. R01DK019038. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. Further support was provided the Czech Science Foundation (GAČR) Grant No. 17-011375, the Czech Ministry of Education (MŠMT) Grant No. LTAUSA18026, “IT4Innovations National Supercomputing Center – LM2015070”, EPSRC Grant No. (UK) EP/R029687/1, the STFC Rutherford Appleton Laboratory (UK), and the Arnold and Mabel Beckman Foundation. We thank Dr. Hana Kvapilová (JH Institute) for the help with measuring TRIR spectra. Yuling Shen (Caltech) is acknowledged for the help with protein preparation. \n\nThe authors declare no competing financial interest.",
revision_no = "26",
abstract = "We have investigated photoinduced hole hopping in a Pseudomonas aeruginosa azurin mutant Re126WWCuI, where two adjacent tryptophan residues (W124 and W122) are inserted between the Cu^I center and a Re photosensitizer coordinated to a H126 imidazole (Re = Re^I(H126)(CO)_3(dmp)^+, dmp = 4,7-dimethyl-1,10-phenanthroline). Optical excitation of this mutant in aqueous media (≤40 μM) triggers 70 ns electron transport over 23 Å, yielding a long-lived (120 μs) Re^I(H126)(CO)_3(dmp&•–)WWCu^(II) product. The Re126FWCu^I mutant (F124, W122) is not redox-active under these conditions. Upon increasing the concentration to 0.2–2 mM, {Re126WWCu^I}_2 and {Re126FWCu^I}_2 are formed with the dmp ligand of the Re photooxidant of one molecule in close contact (3.8 Å) with the W122′ indole on the neighboring chain. In addition, {Re126WWCu^I}_2 contains an interfacial tryptophan quadruplex of four indoles (3.3–3.7 Å apart). In both mutants, dimerization opens an intermolecular W122′ → //*Re ET channel (// denotes the protein interface, *Re is the optically excited sensitizer). Excited-state relaxation and ET occur together in two steps (time constants of ∼600 ps and ∼8 ns) that lead to a charge-separated state containing a Re(H126)(CO)3(dmp•–)//(W122^•+)′ unit; then (Cu^I)′ is oxidized intramolecularly (60–90 ns) by (W122^•+)′, forming Re^I(H126)(CO)_3(dmp^•–)WWCu^I//(Cu^(II))′. The photocycle is closed by ∼1.6 μs Re^I(H126)(CO)_3(dmp^•–) → //(Cu^(II))′ back ET that occurs over 12 Å, in contrast to the 23 Å, 120 μs step in Re126WWCu^I. Importantly, dimerization makes Re126FWCu^I photoreactive and, as in the case of {Re126WWCu^I}_2, channels the photoproduced “hole” to the molecule that was not initially photoexcited, thereby shortening the lifetime of Re^I(H126)(CO)_3(dmp^•–)//Cu^(II). Although two adjacent W124 and W122 indoles dramatically enhance Cu^I → *Re intramolecular multistep ET, the tryptophan quadruplex in {Re126WWCu^I}_2 does not accelerate intermolecular electron transport; instead, it acts as a hole storage and crossover unit between inter- and intramolecular ET pathways. Irradiation of {Re126WWCu^(II)}_2 or {Re126FWCu^(II)}_2 also triggers intermolecular W122′ → //*Re ET, and the Re(H126)(CO)_3(dmp^•–)//(W122^•+)′ charge-separated state decays to the ground state by ∼50 ns Re^I(H126)(CO)_3(dmp^•–)^+ → //(W122^•+)′ intermolecular charge recombination. Our findings shed light on the factors that control interfacial hole/electron hopping in protein complexes and on the role of aromatic amino acids in accelerating long-range electron transport.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/92984,
title ="Cell-Penetrating Protein/Corrole Nanoparticles",
author = "Soll, Matan and Goswami, Tridib K.",
journal = "Scientific Reports",
volume = "9",
pages = "Art. No. 2294",
month = "February",
year = "2019",
doi = "10.1038/s41598-019-38592-w",
issn = "2045-2322",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20190219-134141446",
note = "© 2019 The Author(s). This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. \n\nReceived 19 June 2018; Accepted 18 December 2018; Published\n19 February 2019. \n\nThis study was supported by an International Collaboration Grant from the Jacki and Bruce Barron Cancer Research Scholars’ Program, a partnership of the ICRF and City of Hope, as supported by The Harvey L. Miller Family Foundation to ZG and JT. Research at Caltech was supported by the National Institutes of Health (DK-019038 to HBG). Initial support from the Caltech/City of Hope Biomedical Initiative to HBG and JT also is gratefully acknowledged. \n\nAuthor Contributions: Most of the experimental work was done by M.S. at the Technion, with contributions by T.K.G. for the human serum binding studies, Q.C.C. and S.C. for the TF HPLC analyses, P.L., R.D.T. and A.J.D.B. for the cytotoxicity studies, and I.S. for the catalysis reactions. M.S.h. performed the MALDI-MS. M.S., J.T., H.B.G. and Z.G. wrote the article. The project was supervised by J.T., H.B.G. and Z.G. \n\nThe authors declare no competing interests.",
revision_no = "14",
abstract = "Recent work has highlighted the potential of metallocorroles as versatile platforms for the development of drugs and imaging agents, since the bioavailability, physicochemical properties and therapeutic activity can be dramatically altered by metal ion substitution and/or functional group replacement. Significant advances in cancer treatment and imaging have been reported based on work with a water-soluble bis-sulfonated gallium corrole in both cellular and rodent-based models. We now show that cytotoxicities increase in the order Ga\u2009<\u2009Fe\u2009<\u2009Al\u2009<\u2009Mn\u2009<\u2009Sb\u2009<\u2009Au for bis-sulfonated corroles; and, importantly, that they correlate with metallocorrole affinities for very low density lipoprotein (VLDL), the main carrier of lipophilic drugs. As chemotherapeutic potential is predicted to be enhanced by increased lipophilicity, we have developed a novel method for the preparation of cell-penetrating lipophilic metallocorrole/serum-protein nanoparticles (NPs). Cryo-TEM revealed an average core metallocorrole particle size of 32\u2009nm, with protein tendrils extending from the core (conjugate size is ~100\u2009nm). Optical imaging of DU-145 prostate cancer cells treated with corrole NPs (≤100\u2009nM) revealed fast cellular uptake, very slow release, and distribution into the endoplasmic reticulum (ER) and lysosomes. The physical properties of corrole NPs prepared in combination with transferrin and albumin were alike, but the former were internalized to a greater extent by the transferrin-receptor-rich DU-145 cells. Our method of preparation of corrole/protein NPs may be generalizable to many bioactive hydrophobic molecules to enhance their bioavailability and target affinity.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/92125,
title ="Two Tryptophans Are Better Than One in Accelerating Electron Flow through a Protein",
author = "Takematsu, Kana and Williamson, Heather R.",
journal = "ACS Central Science",
volume = "5",
number = "1",
pages = "192-200",
month = "January",
year = "2019",
doi = "10.1021/acscentsci.8b00882",
issn = "2374-7943",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20190108-080959942",
note = "© 2018 American Chemical Society. This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes. \n\nReceived: November 30, 2018; Published: January 7, 2019. \n\nWe thank Martin Pižl (JH Institute) for his help analyzing the TRIR spectra. Research reported in this publication was supported by the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health under Award Number R01DK019038. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. Additional support was provided by the Arnold and Mabel Beckman Foundation, the Czech Science Foundation (GAČR) Grant 17-011375, and the STFC Rutherford Appleton Laboratory (UK). X-ray crystallography data were collected on SSRL Beamline 12-2 through the support of the Caltech Molecular Observatory, funded by the Gordon and Betty Moore Foundation, Beckman Institute, and the Sanofi-Aventis Bioengineering Research Program. Operations at SSRL are supported by U.S. DOE and NIH. \n\nThe authors declare no competing financial interest. \n\nSafety Statement: No unexpected or unusually high safety hazards were encountered.",
revision_no = "24",
abstract = "We have constructed and structurally characterized a Pseudomonas aeruginosa azurin mutant Re126WWCu^I, where two adjacent tryptophan residues (W124 and W122, indole separation 3.6–4.1 Å) are inserted between the Cu^I center and a Re photosensitizer coordinated to the imidazole of H126 (Re^I(H126)(CO)_3(4,7-dimethyl-1,10-phenanthroline)^+). Cu^I oxidation by the photoexcited Re label (*Re) 22.9 Å away proceeds with a ∼70 ns time constant, similar to that of a single-tryptophan mutant (∼40 ns) with a 19.4 Å Re–Cu distance. Time-resolved spectroscopy (luminescence, visible and IR absorption) revealed two rapid reversible electron transfer steps, W124 → *Re (400–475 ps, K_1 ≅ 3.5–4) and W122 → W124•^+ (7–9 ns, K_2 ≅ 0.55–0.75), followed by a rate-determining (70–90 ns) Cu^I oxidation by W122•^+ ca. 11 Å away. The photocycle is completed by 120 μs recombination. No photochemical Cu^I oxidation was observed in Re126FWCu^I, whereas in Re126WFCu^I, the photocycle is restricted to the ReH126W124 unit and Cu^I remains isolated. QM/MM/MD simulations of Re126WWCu^I indicate that indole solvation changes through the hopping process and W124 → *Re electron transfer is accompanied by water fluctuations that tighten W124 solvation. Our finding that multistep tunneling (hopping) confers a ∼9000-fold advantage over single-step tunneling in the double-tryptophan protein supports the proposal that hole-hopping through tryptophan/tyrosine chains protects enzymes from oxidative damage.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/91946,
title ="Structure, Spectroscopy, and Electrochemistry of Manganese(I) and Rhenium(I) Quinoline Oximes",
author = "Ngo, Danh X. and Kramer, Wesley W.",
journal = "Inorganic Chemistry",
volume = "58",
number = "1",
pages = "737-746",
month = "January",
year = "2019",
doi = "10.1021/acs.inorgchem.8b02862",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20181221-091725545",
note = "© 2018 American Chemical Society. \n\nReceived: October 13, 2018; Published: December 21, 2018.\n\nWe thank Larry Henling, Michael Takase, David VanderVelde, Mona Shahgholi, and Naseem Torian for experimental assistance and discussions. \n\nThis work was funded by NSF CCI Solar Fuels (CHE-130124). Additional support was provided by the Resnick Sustainability Institute at Caltech and a Dr. and Mrs. Daniel C. Harris SURF Fellowship. \n\nAccession Codes: CCDC 1567369–1567373 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, by emailing data_request@ccdc.cam.ac.uk, or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033. \n\nThe authors declare no competing financial interest.",
revision_no = "17",
abstract = "Reactions of α- and β-diimine quinoline aldoximes with Mn(I) and Re(I) tricarbonyl halides afford quinoline oxime complexes. Both Mn(I) and Re(I) complexes experience severe geometric strain due to ligand steric interactions: 6-membered metallocycles exhibit more pronounced distortions than 5-membered ones, consistent with density functional theory structural analyses. Such distortions likely also affect reactivity patterns, as evidenced by Re(I)-induced deoximation of a quinoline variant containing a CF_3-ketoxime.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/89207,
title ="Geometrical Description of Protein Structural Motifs",
author = "Kozak, John J. and Gray, Harry B.",
journal = "Journal of Physical Chemistry B",
volume = "122",
number = "49",
pages = "11289-11294",
month = "December",
year = "2018",
doi = "10.1021/acs.jpcb.8b07130",
issn = "1520-6106",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180828-103040438",
note = "© 2018 American Chemical Society. \n\nReceived: July 25, 2018; Revised: August 22, 2018; Published: August 24, 2018. \n\nWe thank Istvan Horvath (Chalmers University) for making structural images. Roberto Garza-Lopez (Pomona College) provided helpful insights in early stages. Work performed at Caltech was supported by NIH (R01 DK019038 to H.B.G.) and by the Barbro Osher Pro Svecia Foundation (funding a sabbatical for P.W.-S. at Caltech).",
revision_no = "19",
abstract = "We present a geometrical method that can identify secondary structural motifs in proteins via angular correlations. The method uses crystal structure coordinates to calculate angular and radial signatures of each residue relative to an external reference point as the number of nearest-neighbor residues increases. We apply our approach to the blue copper protein amicyanin using the copper cofactor as the external reference point. We define a signature termed Δβ which describes the change in angular correlation as the span of nearest neighbor residues increases. We find that three turn regions of amicyanin harbor residues with Δβ near zero, while residues in other secondary structures have Δβ greater than zero: for β-strands, Δβ changes gradually residue by residue along the strand. Extension of our analysis to other blue copper proteins demonstrated that the noted structural trends are general. Importantly, our geometrical description of the folded protein accounts for all forces holding the structure together. Through this analysis, we identified some of the turns in amicyanin as symmetrical anchor points.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/87936,
title ="Living with Oxygen",
author = "Gray, Harry B. and Winkler, Jay R.",
journal = "Accounts of Chemical Research",
volume = "51",
number = "8",
pages = "1850-1857",
month = "August",
year = "2018",
doi = "10.1021/acs.accounts.8b00245",
issn = "0001-4842",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180717-145213728",
note = "© 2018 American Chemical Society. ACS AuthorChoice - This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes. \n\nReceived: May 30, 2018; Published: July 17, 2018. \n\nResearch reported in this Account was supported by the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health under Award Number R01DK019038. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. Additional support was provided by the National Science Foundation (CHE-1305124) and the Arnold and Mabel Beckman Foundation. \n\nThe authors declare no competing financial interest.",
revision_no = "17",
abstract = "Work on the electronic structures of metal–oxo complexes began in Copenhagen over 50 years ago. This work led to the prediction that tetragonal multiply bonded transition metal–oxos would not be stable beyond the iron–ruthenium–osmium oxo wall in the periodic table and that triply bonded metal–oxos could not be protonated, even in the strongest Brønsted acids. In this theory, only double bonded metal–oxos could attract protons, with basicities being a function of the electron donating ability of ancillary ligands. Such correlations of electronic structure with reactivity have gained importance in recent years, most notably owing to the widespread recognition that high-valent iron–oxos are intermediates in biological reactions critical to life on Earth.\nIn this Account, we focus attention on the oxygenations of inert organic substrates by cytochromes P450, as these reactions involve multiply bonded iron–oxos. We emphasize that P450 iron–oxos are strong oxidants, so strong that they would destroy nearby amino acids if substrates are not oxygenated rapidly; it is our view that these high-valent iron–oxos are such dangerous reactive oxygen species that Nature surely found ways to disable them. Looking more deeply into this matter, mainly by examining many thousands of structures in the Protein Data Bank, we have found that P450s and other enzymes that require oxygen for function have chains of tyrosines and tryptophans that extend from active-site regions to protein surfaces. Tyrosines are near the heme active sites in bacterial P450s, whereas tryptophan is closest in most human enzymes. High-valent iron–oxo survival times taken from hole hopping maps range from a few nanoseconds to milliseconds, depending on the distance of the closest Trp or Tyr residue to the heme. In our proposed mechanism, multistep hole tunneling (hopping) through Tyr/Trp chains guides the damaging oxidizing hole to the protein surface, where it can be quenched by soluble protein or small molecule reductants. As the Earth’s oxygenic atmosphere is believed to have developed about 2.5 billion years ago, the increase in occurrence frequency of tyrosine and tryptophan since the last universal evolutionary ancestor may be in part a consequence of enzyme protective functions that developed to cope with the environmental toxin, O_2.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/90767,
title ="Organoboron-modified cyanometalates for use in nonaqueous redox flow batteries",
author = "Gray, Harry B. and McNicholas, Brendon J.",
pages = "INOR-334",
month = "August",
year = "2018",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20181108-144044224",
note = "© 2018 American Chemical Society.",
revision_no = "10",
abstract = "We have synthesized and structurally characterized a series of organoboron-modified cyanometalates. The redn. potentials of these modified metal complexes can be tuned over a wide range by variations in the Lewis acidities of the appended organoboron derivs. We have found half-wave potential shifts of +250 mV/BPh_3 and +380 mV/B(C_6F_5)_3, with total shifts of +1.5 and +2.1 V, resp., relative to the parent M^(III/II) (M = Mn, Fe) redox couples. Selected highly sol. complexes are attractive candidates for use in flow batteries, as their redox pairs exhibit electrochem. reversibility over a wide potential range in nonaq. solvents.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/90774,
title ="Robust catalysts for solar-driven water splitting",
author = "Gray, Harry B.",
pages = "INOR-254",
month = "August",
year = "2018",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20181108-161056825",
note = "© 2018 American Chemical Society.",
revision_no = "9",
abstract = "The efficient generation of mol. hydrogen from sunlight and water is one of the holy grails of 21st century chem. Hydrogen is a clean, renewable fuel that could play a key role in meeting the world's skyrocketing demand for energy. Several investigators have employed hydrogenases as catalysts coupled to cathodes for H_2 prodn., as these enzymes can operate in water with very high turnover frequencies. But these enzymes are not stable under aerobic conditions, so recent work has largely focused on robust inorg. materials. Among inorg. materials, platinum is a very active catalyst for proton redn., but scarcity and high cost limit its widespread use. Clearly, we must replace platinum in solar-driven water splitting devices!. The good news is that investigators in the NSF CCI Solar Fuels Program have accepted this\nchallenge: working together, we have found that Ni-Mo nanopowders and metal phosphide nanocrystals have catalytic efficiencies near that of platinum for hydrogen evolution from water. We also have developed robust mixed-metal nanostructured catalysts for the prodn. of oxygen from water. There is an urgent need to find even better water oxidn. catalysts, as the protons and electrons liberated when oxygen is evolved are the fundamental particles required for sustainable energy storing reactions, not only for hydrogen prodn., but also for the conversion of nitrogen and carbon dioxide to fuels and chems.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/86186,
title ="Structural stabilities of calcium proteins: Human intelectin-1 and frog lectin XEEL",
author = "Kozak, John J. and Gray, Harry B.",
journal = "Journal of Inorganic Biochemistry",
volume = "185",
pages = "86-102",
month = "August",
year = "2018",
doi = "10.1016/j.jinorgbio.2018.04.021",
issn = "0162-0134",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180502-085201827",
note = "© 2018 Elsevier Inc. \n\nReceived 23 December 2017, Revised 10 April 2018, Accepted 30 April 2018, Available online 2 May 2018. \n\nWe thank NIH (R01 DK019038 to HBG) for support of work performed at the California Institute of Technology. Financial support for R.A.G.-L. was provided in part by grant # 52007555 to Pomona College from the Howard Hughes Medical Institute through the Precollege and Undergraduate Science Education Program. KW was supported in part by Grants for Development of New Faculty Staff, Ratchadaphiseksomphot Endowment Fund (Grant no. GDNS 59-059-23-020 and DNS 61-011-23-003-2), Chulalongkorn University and the Research Fund for DPST Graduate with First Placement [Grant no. 018/2559] from the Institute for the Promotion of Teaching Science and Technology (IPST), Thailand. Molecular graphics images were produced using the Chimera package from the Computer Graphics Laboratory, University of California, San Francisco (supported by NIH P41RR-01081).",
revision_no = "24",
abstract = "We extend our study of the structural stability of helical and nonhelical regions in chain A of human intelectin-1 to include a second human intelectin (4WMY) and the frog protein “Xenopus embryonic epidermal lectin” (XEEL). These unique lectins have been shown to recognize carbohydrate residues found exclusively in microbes, thus they could potentially be developed into novel microbe detection and sequestration tools. We believe that by studying the structural stability of these proteins we can provide insights on their biological role and activities. Using a geometrical model introduced previously, we perform computational analyses of protein crystal structures that quantify the resiliency of the native state to steric perturbations. Based on these analyses, we conclude that differences in the resiliency of the human and frog proteins can be attributed primarily to differences in non-helical regions and to residues near Ca ions. Since these differences are particularly pronounced in the vicinity of the ligand binding site, they provide an explanation for the finding that human intelectin-1 has a higher affinity for a ligand than XEEL. We also present data on conserved and position-equivalent pairs of residues in 4WMY and XEEL. We identify residue pairs as well as regions in which the influence of neighboring residues is nearly uniform as the parent protein denatures. Since the structural signatures are conserved, this identification provides a basis for understanding why both proteins exhibit trimeric structures despite poor sequence conservation at the interface.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/90803,
title ="Trapping an iron(VI) water-splitting intermediate in nonaqueous media",
author = "Hunter, Bryan and Thompson, Niklas",
pages = "INOR-67",
month = "August",
year = "2018",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20181109-141642042",
note = "© 2018 American Chemical Society.",
revision_no = "9",
abstract = "Understanding the mechanisms of highly-active, earth-abundant water oxidn. electrocatalysts can guide the development of advanced water-splitting devices that convert renewable electricity to clean fuels. Unfortunately, catalytic intermediates are difficult to isolate and characterize because they tend to be extremely transient and present at low concns. A typical approach to this problem is to slow down turnover by limiting the availability of substrate. However, in cases where substrate and solvent are identical-such as in water oxidn.-the soln. can be more complex. By dramatically limiting the availability of substrate (water and hydroxide) in nickel-iron catalyzed heterogeneous water oxidn., we have\nobsd. and characterized a high-valent iron intermediate. Orthogonal spectroscopies indicate that the intermediate contains iron in the rare 6+ oxidn. state. This ferrate analog makes dioxygen upon addn. of hydroxide and can be stepwise regenerated by anodic polarization.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/87338,
title ="Vibrational coherence transfer in the ultrafast intersystem crossing of a diplatinum complex in solution",
author = "Monni, Roberto and Capano, Gloria",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "115",
number = "28",
pages = "E6396-E6403",
month = "July",
year = "2018",
doi = "10.1073/pnas.1719899115",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180626-075430344",
note = "© 2018 National Academy of Sciences. Published under the PNAS license. \n\nEdited by Martin Gruebele, University of Illinois at Urbana–Champaign, Urbana, IL, and approved June 1, 2018 (received for review November 23, 2017). Published ahead of print June 25, 2018. \n\nThis work was supported by the Swiss National Science Foundation (NSF) via the National Center of Competence in Research/Molecular Ultrafast Science and Technology and Contract 200021_137717. We also thank the European collaboration program Cooperation in Science and Technology (Actions CM1202 and CM1405), the Czech Science Foundation (Grant 17-011375), and the NSF Center for Chemical Innovation in Solar Fuels Program (CHE-1305124) for support. \n\nAuthor contributions: M.C. designed research; R.M., G.C., G.A., and I.T. performed research; G.C., H.B.G., and I.T. contributed new reagents/analytic tools; R.M., G.C., G.A., A.V., I.T., and M.C. analyzed data; and M.C. wrote the paper. \n\nThe authors declare no conflict of interest. \n\nThis article is a PNAS Direct Submission. \n\nThis article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1719899115/-/DCSupplemental.",
revision_no = "21",
abstract = "We investigate the ultrafast transient absorption response of tetrakis(μ-pyrophosphito)diplatinate(II), [Pt_2(μ-P_2O_5H_2)_4]^(4−) [hereafter abbreviated Pt(pop)], in acetonitrile upon excitation of its lowest singlet ^1A_(2u) state. Compared with previously reported solvents [van der Veen RM, Cannizzo A, van Mourik F, Vlček A, Jr, Chergui M (2011) J Am Chem Soc 133:305–315], a significant shortening of the intersystem crossing (ISC) time (<1 ps) from the lowest singlet to the lowest triplet state is found, allowing for a transfer of vibrational coherence, observed in the course of an ISC in a polyatomic molecule in solution. Density functional theory (DFT) quantum mechanical/molecular mechanical (QM/MM) simulations of Pt(pop) in acetonitrile and ethanol show that high-lying, mostly triplet, states are strongly mixed and shifted to lower energies due to interactions with the solvent, providing an intermediate state (or manifold of states) for the ISC. This suggests that the larger the solvation energies of the intermediate state(s), the shorter the ISC time. Because the latter is smaller than the pure dephasing time of the vibrational wave packet, coherence is conserved during the spin transition. These results underscore the crucial role of the solvent in directing pathways of intramolecular energy flow.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/90235,
title ="Activity of iridium pyridine-based nanophotoswitches in retina",
author = "Yue, Lan and Pribisko, Melanie",
journal = "Investigative Ophthalmology and Visual Science",
volume = "59",
number = "9",
pages = "Art. No. 3976",
month = "July",
year = "2018",
issn = "0146-0404",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20181010-142930931",
note = "© 2018 The Authors. This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.",
revision_no = "12",
abstract = "Purpose : Nanophotoswitches (NPSs) offer a new tool for optical stimulation of neuronal activity, in vitro and potentially in vivo. Our group previously reported a ruthenium bipyridine-based NPS (Rubpy-C17) that, after injection into the eyes of photoreceptor degenerated blind rats, elicited electrical activity in the contralateral superior colliculus upon light exposure. Compared with the ruthenium complexes, the family of iridium complexes has been more widely used in clinics, owing to its biosafety profile. We have thus synthesized and tested Irbpy-C17, an analog of Rubpy-C17 with the ruthenium core replaced by iridium.\n\nMethods : Rubpy molecules can be visualized by their luminescence upon visible wavelength illumination. To examine membrane incorporation, fluorescence imaging of HEK cells was obtained after incubation with Irbpy-C17. Activity of Irbpy-C17 was studied by MEA recording from wholemount retina after intravitreal injection. The test molecules were administered into the vitreous of blind RCS rats at the concentration of 200 µM. Animals were kept in dark after injection until the surgical dissection of retina. Acutely isolated retina was mounted on the MEA with the ganglion cell layer facing down to capture the spiking activity in response to light stimuli.\n\nResults : Irbpy-C17 exhibited good membrane incorporation similar to that of Rubpy-C17. Interestingly, despite that Irbpy-C17 elicited minimal light response initially, subsequent application of synaptic blocker cocktail that pharmacologically isolated RGCs substantially enhanced the light activation of RGCs (1.8 ± 0.3 fold increase in spike frequency). In comparison with the 3-hour incubation between injection and dissection, prolonged 24-hour incubation led to a more pronounced 2.5 ± 0.5 fold increase in spike frequency.\n\nConclusions : Our data suggest that Irbpy-C17 may act on multiple components of the retinal neural circuitry that could suppress its direct action on RGCs via synaptic transmission. These molecules intravitreally administered remain stable and active in the ocular environment up to at least one day post injection. These data will prompt us to further study the iridium complexes in parallel with the ruthenium counterparts, particularly for the underlying mechanism of their differential behavior. The NPSs obviates the need for gene manipulation or toxic UV illumination, highlighting its potential in generating high-acuity prosthetic vision in the blind.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/89961,
title ="Delivery and Toxicity of Ruthenium Pyridine-based Nanophotoswitches in Retina",
author = "Pribisko, Melanie and Herget, Uli",
journal = "Investigative Ophthalmology and Visual Science",
volume = "59",
number = "9",
pages = "Art. No. 232",
month = "July",
year = "2018",
issn = "0146-0404",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180926-125050352",
note = "© 2018 This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. \n\nCommercial Relationships: Melanie Pribisko, None; Uli Herget, None; Lan Yue, None; Ming-yi Lin, None; Robert Chow, None; Mark Humayun, None; Robert Grubbs, None; Harry Gray, None. \n\nSupport: NSF AIRTT.",
revision_no = "9",
abstract = "Purpose : Nanophotoswitches (NPSs) offer a new tool for optical stimulation of neuronal activity, in vitro and potentially in vivo. Our group previously reported a ruthenium bipyridine (Rubpy)-based NPS (Rubpy-C17) that, after injection into the eyes of photoreceptor degenerated blind rats, elicited electrical activity in the contralateral superior colliculus upon light illumination. We wish to optimize delivery, efficacy and biosafety of the NPSs; our preliminary experiments examining the Rubpy complexes in vivo suggest low acute toxicity. Intravitreal delivery of the Rubpy-C17 complexes has been shown to restore light response recorded from the superior colliculus of the photoreceptor degenerate RCS rats 1 day after the injection. The restored light response was largely preserved 3 days after the injection, suggesting that the Rubpy-C17 complexes are well tolerated by the retinal neurons during the test period.\n\nMethods : Promising NPSs molecules absorb and can be visualized by their luminescence upon visible wavelength illumination. This enables us to evaluate the toxicity of the NPSs using an array of in vitro, in vivo and ex vivo tests, including in vitro electrochemical and spectroscopic studies to determine DNA binding and DNA intercalation. In addition, the NPSs were embedded in polymer matrices and the emission monitored to determine the rate of release upon injection into the eye.\n\nResults : Preliminary data show that young zebrafish tolerate injection of up to 100 uM Rubpy-C17 into the eye, with complete disappearance of the Rubpy-C17 emission from the eye within a day. Interestingly, blue-green emission appears in the liver region as the orange-red emission of Rubpy-C17 decreases. As this may be a result of metabolism of the Rubpy-C17, we extracted the blue-green emitting molecule for characterization. Initial studies of slow-release drug delivery system and conditions indicate some success with polyethyleneglycol-poly(lactic-co-glycolic acid)-poly-L-lysine (PEG-PLGA-PEG) and polycaprolactone (PCL) polymers.\n\nConclusions : Our data suggest that NPSs dissolved in a DMSO solution and intravitreally administered remain stable and active in the ocular environment up to at least one day post injection, which can be extended when coadministered with certain polymer mixtures. The DNA binding and DNA intercalation studies, in combination with the extended release polymers, address toxicity concerns of the NPSs in the eye.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/86677,
title ="Fluctuating hydrogen-bond networks govern anomalous electron transfer kinetics in a blue copper protein",
author = "Kretchmer, Joshua S. and Boekelheide, Nicholas",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "115",
number = "24",
pages = "6129-6134",
month = "June",
year = "2018",
doi = "10.1073/pnas.1805719115",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180529-142106727",
note = "© 2018 the Author(s). Published by PNAS. This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND). \n\nEdited by Michael L. Klein, Temple University, Philadelphia, PA, and approved May 4, 2018 (received for review April 3, 2018). Published ahead of print May 29, 2018. \n\nThis work was supported by the NIH under Award R01DK019038 (to H.B.G. and J.R.W.) and by the NSF under Award CHE-1611581 (to T.F.M.). Additional support was provided by NIH Grant GM095037 (to J.J.W.), the Arnold and Mabel Beckman Foundation, and NSF Grant DGE-1144469 (to J.S.K.). \n\nAuthor contributions: J.S.K., N.B., J.J.W., J.R.W., H.B.G., and T.F.M. designed research; J.S.K., N.B., and J.J.W. performed research; J.S.K., N.B., J.J.W., J.R.W., H.B.G., and T.F.M. analyzed data; and J.S.K., N.B., J.J.W., J.R.W., H.B.G., and T.F.M. wrote the paper. \n\nThe authors declare no conflict of interest. \n\nThis article is a PNAS Direct Submission. \n\nThis article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1805719115/-/DCSupplemental.",
revision_no = "28",
abstract = "We combine experimental and computational methods to address the anomalous kinetics of long-range electron transfer (ET) in mutants of Pseudomonas aeruginosa azurin. ET rates and driving forces for wild type (WT) and three N47X mutants (X = L, S, and D) of Ru(2,2′-bipyridine)2 (imidazole)(His83) azurin are reported. An enhanced ET rate for the N47L mutant suggests either an increase of the donor–acceptor (DA) electronic coupling or a decrease in the reorganization energy for the reaction. The underlying atomistic features are investigated using a recently developed nonadiabatic molecular dynamics method to simulate ET in each of the azurin mutants, revealing unexpected aspects of DA electronic coupling. In particular, WT azurin and all studied mutants exhibit more DA compression during ET (>2 Å) than previously recognized. Moreover, it is found that DA compression involves an extended network of hydrogen bonds, the fluctuations of which gate the ET reaction, such that DA compression is facilitated by transiently rupturing hydrogen bonds. It is found that the N47L mutant intrinsically disrupts this hydrogen-bond network, enabling particularly facile DA compression. This work, which reveals the surprisingly fluctional nature of ET in azurin, suggests that hydrogen-bond networks can modulate the efficiency of long-range biological ET.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/84697,
title ="Trapping an Iron(VI) Water-Splitting Intermediate in Nonaqueous Media",
author = "Hunter, Bryan M. and Thompson, Niklas B.",
journal = "Joule",
volume = "2",
number = "4",
pages = "747-763",
month = "April",
year = "2018",
doi = "10.1016/j.joule.2018.01.008",
issn = "2542-4351",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180207-065509383",
note = "© 2018 Elsevier Inc. \n\nReceived: December 20, 2017. Revised: January 8, 2018. Accepted: January 11, 2018. Published: February 6, 2018. \n\nThis work was supported by the NSF CCI Solar Fuels Program ( CHE- 1305124 ) and the Arnold and Mabel Beckman Foundation, with additional support from NSF EAR-1322082 . B.M.H. is a Fellow of the Resnick Sustainability Institute at Caltech. The authors thank Jonas Peters for helpful discussions. Additional data and methods are available in the Supplemental Information. \n\nAuthor Contributions: B.M.H. designed and performed the experiments; N.B.T. collected and analyzed the Mössbauer spectra; A.M.M. synthesized and characterized the materials; G.R.R. assisted with luminescence and Raman electrochemistry; M.G.H. assisted with electrochemistry and IR spectroelectrochemistry; J.R.W. and H.B.G., with the other authors, developed the proposed mechanism. All authors wrote the manuscript. \n\nThe authors declare no competing interests.",
revision_no = "19",
abstract = "We report in situ spectroscopic measurements in nonaqueous media designed to trap an exceptionally strong oxidant generated electrochemically from an iron-containing nickel layered double hydroxide ([NiFe]-LDH) material. Anodic polarization of this material in acetonitrile produces metal-oxo vibrational spectroscopic signatures along with an extremely narrow near-infrared luminescence peak that strongly indicate that the reactive intermediate is cis-dioxo-iron(VI). Chemical trapping experiments reveal that addition of H_2O to the polarized electrochemical cell produces hydrogen peroxide; and, most importantly, addition of HO– generates oxygen. Repolarization of the electrode restores the iron(VI) spectroscopic features, confirming that the high-valent oxo complex is active in the electrocatalytic water oxidation cycle.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/85964,
title ="Iron Is the Active Site in Nickel/Iron Water Oxidation Electrocatalysts",
author = "Hunter, Bryan M. and Winkler, Jay R.",
journal = "Molecules",
volume = "23",
number = "4",
pages = "Art. No. 903",
month = "April",
year = "2018",
doi = "10.3390/molecules23040903",
issn = "1420-3049",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180418-165501153",
note = "© 2018 The Author(s). This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0). \n\nReceived: 28 February 2018 / Revised: 10 April 2018 / Accepted: 12 April 2018 / Published: 14 April 2018. \n\n(This article belongs to the Special Issue Artificial Photosynthesis: Recent Progress in Solar Energy Utilization).\n\nThis work was supported by the NSF CCI Solar Fuels Program (CHE-1305124) and the Arnold and Mabel Beckman Foundation. B.M.H. acknowledges a Fellowship from the Resnick Sustainability Institute at Caltech. \n\nThe authors declare no conflict of interest.",
revision_no = "12",
abstract = "Efficient catalysis of the oxygen-evolution half-reaction (OER) is a pivotal requirement for the development of practical solar-driven water splitting devices. Heterogeneous OER electrocatalysts containing first-row transition metal oxides and hydroxides have attracted considerable recent interest, owing in part to the high abundance and low cost of starting materials. Among the best performing OER electrocatalysts are mixed Fe/Ni layered double hydroxides (LDH). A review of the available experimental data leads to the conclusion that iron is the active site for [NiFe]-LDH-catalyzed alkaline water oxidation.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/84610,
title ="Photoelectrochemical Performance of BiVO_4 Photoanodes Integrated with [NiFe]-Layered Double Hydroxide Nanocatalysts",
author = "Sinclair, Timothy S. and Gray, Harry B.",
journal = "European Journal of Inorganic Chemistry",
volume = "2018",
number = "9",
pages = "1059",
month = "March",
year = "2018",
doi = "10.1002/ejic.201800083",
issn = "1434-1948",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180131-145419816",
note = "© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. \n\nIssue online: 1 March 2018; Version of record online: 30 January 2018.",
revision_no = "23",
abstract = "Invited for the cover of this issue are Astrid M. Müller and co-workers from California Institute of Technology, Pasadena, California, USA. The cover image shows a drawing of an integrated photoanode whose active materials are laser-synthesized highly efficient [NiFe]-layered double hydroxide or Co_3O_4 water oxidation nanocatalysts and sunlight-absorbing BiVO_4. ",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/82837,
title ="Photoelectrochemical Performance of BiVO_4 Photoanodes Integrated with [NiFe]-Layered Double Hydroxide Nanocatalysts",
author = "Sinclair, Timothy S. and Gray, Harry B.",
journal = "European Journal of Inorganic Chemistry",
volume = "2018",
number = "9",
pages = "1060-1067",
month = "March",
year = "2018",
doi = "10.1002/ejic.201701231",
issn = "1434-1948",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20171101-124030260",
note = "© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. \n\nIssue online: 1 March 2018; Version of record online: 6 December 2017; Accepted manuscript online: 31 October 2017; Manuscript Received: 18 October 2017. \n\nWe thank Chi Ma and June Wicks for help with SEM imaging and EDS mapping, and George Rossman for help with reflectance measurements. Research was carried out in the Laser Resource Center and the Molecular Materials Research Center of the Beckman Institute of the California Institute of Technology. T. S. S. acknowledges the Caltech SURF office, a Dr. Terry Cole SURF Fellowship, and a Jack and Edith Roberts SURF Fellowship. The National Science Foundation (NSF) CCI Solar Fuels Program (CHE-1305124) and the Arnold and Mabel Beckman Foundation supported this work.",
revision_no = "36",
abstract = "We immobilized laser-made nickel iron layered double hydroxide ([NiFe]-LDH) nanocatalysts on BiVO_4 photoanodes. We compared photoelectrochemical performance of integrated [NiFe]-LDH–BiVO_4 photoanodes in sulfite-free aqueous electrolyte with photocurrent generation of neat BiVO_4 photoanodes in aqueous electrolyte with sulfite added as sacrificial hole acceptor. We optimized catalyst mass loading, which is a tradeoff between most efficient depletion of photogenerated holes that drive catalytic turnover and parasitic light absorption by the catalyst particles. We also mitigated nanocatalyst aggregation on the BiVO_4 surface by a surfactant that selectively ligated the catalysts or by dispersing the catalyst suspension more rapidly on the photoanode surface. Our rational optimization strategies enhanced photoelectrochemical performance of integrated nanocatalyst photoanodes: Two thirds of all photogenerated holes escaped loss processes in our optimized integrated [NiFe]-LDH–BiVO_4 photoanodes under 100 mW\u2009cm^(–2) of simulated air mass 1.5 G illumination in aqueous pH 9.2 buffered electrolyte. Our systematic optimization strategies for integration of highly efficient water oxidation nanocatalysts with a visible-light absorber provide a path towards functional artificial photosynthesis devices.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/85787,
title ="Electron flow through multicopper oxidases",
author = "Gray, Harry",
pages = "INOR-448",
month = "March",
year = "2018",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180412-130011500",
note = "© 2018 American Chemical Society.",
revision_no = "9",
abstract = "Biol. electron transfers often occur between metal-contg. cofactors that are sped. By very large mol. distances. Understanding the underlying physics and chem. of these long-range redox processes is the goal of much of the work in my lab. In collaboration with Jay Winkler, Jieun Shin, Shabnam Hematian, and Brian Sanders have investigated laser-triggered electron flow through native, mutant, and Ru-modified multicopper oxides. The results indicate that Trp and Tyr residues near the trinuclear (type 2/type 3) site play key roles during catalysis of substrate oxidsn. by these enzymes.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/85797,
title ="Living with oxos",
author = "Gray, Harry",
pages = "INOR-533",
month = "March",
year = "2018",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180412-154951618",
note = "© 2018 American Chemical Society.",
revision_no = "10",
abstract = "The theory of multiple bonding in metal oxos, which accounts for their ground state electronic structures and\nspectroscopic properties, predicts that an \"oxo wall\" separates Fe-Ru-Os and Co-Rh-Ir in the periodic table.\nAfter reviewing this work, I will discuss the roles metal oxos play in hydrocarbon oxygenation catalyzed by\ncytochrome P 450. Interestingly, Jay Winkler and I have found that most P450s have Trp/Tyr chains very near\nthe heme active sites. We have suggested that uncoupled high-valent iron-oxo intermediates would be reduced\nby hole transfer to these chains, thereby protecting P450s from oxidative degrdn.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/85796,
title ="Making oxygen for space travel",
author = "Gray, Harry",
pages = "INOR-464",
month = "March",
year = "2018",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180412-154700914",
note = "© 2018 American Chemical Society.",
revision_no = "9",
abstract = "Working with JPL, Bryan Hunter, Emmanuelle Despagnet-Ayoub, Brendon McNicholas, Jill Clinton, Mamadou Diallo, Tom\nSheridan, and Brian Sanders are exploring ways to electrocatalytically make oxygen from carbon dioxide at relatively low\ntemps. We have shown that water is a co-product of Mn (or Re) catalyzed substrate redn. to carbon monoxide. Oxidn. of\nwater liberates oxygen, as well as the protons and electrons required for sustained catalysis. We also are making robust\nmetal-carbide and metal-oxide nanoscale materials by pulsed-laser plasma synthesis with the goal of improving the\nperformance of our catalytic cathodes and anodes. We would like to have the inorg. chem. in place to make it possible (when\nneeded for space missions) to convert some fraction of carbon dioxide in the Mars atm. to oxygen.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/85855,
title ="Photoelectrochemical performance of BiVO_4 photoanodes integrated with [NiFe]-layered double hydroxide water oxidation nanocatalysts",
author = "Mueller, Astrid M. and Sinclair, Timothy S.",
pages = "INOR-563",
month = "March",
year = "2018",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180413-155002349",
note = "© 2018 American Chemical Society.",
revision_no = "12",
abstract = "We integrated laser-made highly active nickel iron layered double hydroxide ([NiFe]-LDH) water oxidn. nanocatalysts, which we\ndeveloped in our group, with BiVO_4 photoanodes and tested their photoelectrochem. performance under simulated sunlight\nillumination. We demonstrated decreased aggregation and increased photocurrent generation with nanocatalysts that contain\ndipos. metals ([NiFe]-LDH and cobalt oxide) as citrate surfactant selectively ligated the catalyst nanoparticles. We also\noptimized catalyst mass loading, which is a tradeoff between most efficient depletion of photogenerated holes that drive\ncatalytic turnover and parasitic light absorption by the catalyst particles. Integrated [NiFe]-LDH-BiVO_4 photoanodes enhanced\nphotocurrent generation by a factor of 3.3 compared to bare BiVO_4. Comparison of photoelectrochem. performance of\nintegrated [NiFe]-LDH-BiVO_4 photoanodes in sulfite-free aq. electrolyte with photocurrent generation of neat BiVO_4\nphotoanodes in aq. electrolyte with sulfite added as sacrificial hole acceptor showed that two thirds of all photogenerated holes\nescaped loss processes in our optimized integrated photoanodes. Our systematic integration strategies provide a path towards\nfunctional artificial photosynthesis devices.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/84163,
title ="Resistance to receptor-blocking therapies primes tumors as targets for HER3-homing nanobiologics",
author = "Sims, Jessica D. and Taguiam, Jan Michael",
journal = "Journal of Controlled Release",
volume = "271",
pages = "127-138",
month = "February",
year = "2018",
doi = "10.1016/j.jconrel.2017.12.024",
issn = "0168-3659",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180108-103844165",
note = "© 2018 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/BY-NC-ND/4.0/). \n\nReceived 12 August 2017; revised 9 December 2017; accepted 21 December 2017; available online 27 December 2017. \n\nThe authors thank Josie Bergeron, Catherine Bresee, and Xiao Zhang for assistance with biostatistics; and Accixx Biomedical Consulting (www.Accixx.com) for editorial assistance. LKMK thanks C Rey, A and M Medina-Kauwe, and D Revetto for ongoing support. \n\nThis work was supported in part by grants to LKMK from the NIH/NCI (R01 CA129822, R01 CA140995), the DoD (W81XWH-15-1-0604), the Avon Foundation (02–2015-060), Margie and Robert E. Petersen Foundation, and the Clinical and Translational Science Institute (CTSI V087). The studies shown in Fig. S1, D-I were supported by Eos Biosciences through a contractual research agreement. \n\nDr. Medina-Kauwe and Cedars-Sinai Medical Center hold significant financial interest in Eos Biosciences, Inc., of which Dr. Medina-Kauwe is co-founder and scientific advisor. A patent describing the H3-D (HerDox) nanobiotherapeutic (US Patent No. 9,078,927) has been awarded, and another describing the application of this particle for treating resistant tumors (No. 62/342,829) has recently been filed.",
revision_no = "26",
abstract = "Resistance to anti-tumor therapeutics is an important clinical problem. Tumor-targeted therapies currently used in the clinic are derived from antibodies or small molecules that mitigate growth factor activity. These have improved therapeutic efficacy and safety compared to traditional treatment modalities but resistance arises in the majority of clinical cases. Targeting such resistance could improve tumor abatement and patient survival. A growing number of such tumors are characterized by prominent expression of the human epidermal growth factor receptor 3 (HER3) on the cell surface. This study presents a “Trojan-Horse” approach to combating these tumors by using a receptor-targeted biocarrier that exploits the HER3 cell surface protein as a portal to sneak therapeutics into tumor cells by mimicking an essential ligand. The biocarrier used here combines several functions within a single fusion protein for mediating targeted cell penetration and non-covalent self-assembly with therapeutic cargo, forming HER3-homing nanobiologics. Importantly, we demonstrate here that these nanobiologics are therapeutically effective in several scenarios of resistance to clinically approved targeted inhibitors of the human EGF receptor family. We also show that such inhibitors heighten efficacy of our nanobiologics on naïve tumors by augmenting HER3 expression. This approach takes advantage of a current clinical problem (i.e. resistance to growth factor inhibition) and uses it to make tumors more susceptible to HER3 nanobiologic treatment. Moreover, we demonstrate a novel approach in addressing drug resistance by taking inhibitors against which resistance arises and re-introducing these as adjuvants, sensitizing tumors to the HER3 nanobiologics described here.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/83427,
title ="Relaxation of structural constraints during Amicyanin unfolding",
author = "Kozak, John J. and Gray, Harry B.",
journal = "Journal of Inorganic Biochemistry",
volume = "179",
pages = "135-145",
month = "February",
year = "2018",
doi = "10.1016/j.jinorgbio.2017.11.016",
issn = "0162-0134",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20171122-090433323",
note = "© 2017 Elsevier Inc. \n\nReceived 5 July 2017, Revised 28 September 2017, Accepted 17 November 2017, Available online 22 November 2017. \n\nWe thank NIH (R01 DK019038 to HBG) for support of work performed at the California Institute of Technology. Financial support for R.A.G.-L. was provided in part by grant # 52007555 to Pomona College from the Howard Hughes Medical Institute through the Precollege and Undergraduate Science Education Program. Molecular graphics images were produced using the Chimera package from the Computer Graphics Laboratory, University of California, San Francisco (supported by NIH P41RR-01081).",
revision_no = "21",
abstract = "We study the thermal unfolding of amicyanin by quantifying the resiliency of the native state to structural perturbations. Three signatures characterizing stages of unfolding are identified. The first signature, lateral extension of the polypeptide chain, is calculated directly from the reported crystallographic data. Two other signatures, the radial displacement of each residue from Cu(II) and the angular spread in the chain as the protein unfolds, are calculated using crystallographic data in concert with a geometrical model we introduced previously (J.J. Kozak, H. B. Gray, R. A. Garza-López, J. Inorg. Biochem. 155(2016) 44–55). Particular attention is paid to the resiliency of the two beta sheets in amicyanin. The resiliency of residues in the near neighborhood of the Cu center to destabilization provides information on the persistence of the entatic state. Similarly, examining the resiliency of residues intercalated between structured regions (beta sheets, the alpha helix) provides a basis for identifying a “hydrophobic core.” A principal focus of our study is to compare results obtained using our geometrical model with the experimental results (C. La Rosa, D. Milardi, D. M. Grasso, M. P. Verbeet, G. W. Canters, L. Sportelli, R. Guzzi, Eur. Biophy. J.30(8),(2002) 559–570) on the denaturation of amicyanin, and we show that our results support a classical model proposed by these authors.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/88143,
title ="Irving Langmuir Award in Chemical Physics: George W. Flynn",
author = "Gray, Harry B.",
journal = "Chemical and Engineering News",
volume = "96",
number = "2",
pages = "40",
month = "January",
year = "2018",
issn = "0009-2347",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180723-153922653",
note = "© 2018 American Chemical Society.",
revision_no = "9",
abstract = "Sponsor: ACS and the ACS Division of Physical Chemistry \n\nCitation: For contributions to our fundamental understanding of the structural and chemical behavior of graphene interfaces. \n\nCurrent position: Eugene Higgins Professor of Chemistry, Columbia University \n\nEducation: B.S., chemistry, Yale University; Ph.D., chemistry, Harvard University \n\nFlynn on his scientific role model and why: “Four mentors have had a significant influence in determining the course of my scientific career: my high school chemistry teacher, Mr. Coburn, who made chemistry a remarkably clear discipline and introduced me to independent research; Ali Javan, who taught me to think like a physicist about the interaction of light and matter; and John Baldeschwieler and E. Bright Wilson, who were my Ph.D. mentors and taught me the importance of clear thinking in scientific discussions and about being fearless in attacking new research areas.” \n\nWhat his colleagues say: “In groundbreaking work, he demonstrated that single sheet graphenes are much more reactive than multiple sheet materials. His fundamental work will surely be of great help to investigators who are working on electronic devices based on graphene and doped-graphene materials.”—Harry B. Gray, California Institute of Technology.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/83257,
title ="Triphenylsulfonium topophotochemistry",
author = "Despagnet-Ayoub, E. and Kramer, W. W.",
journal = "Photochemical and Photobiological Sciences",
volume = "17",
number = "1",
pages = "27-34",
month = "January",
year = "2018",
doi = "10.1039/c7pp00324b",
issn = "1474-905X",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20171116-114003756",
note = "© 2017 The Royal Society of Chemistry and Owner Societies. \n\nThe article was received on 25 Aug 2017, accepted on 03 Nov 2017 and first published on 03 Nov 2017. \n\nWe thank Dr VanderVelde for his help on the DOSY-NMR experiment. This work was supported by the National Science Foundation Center for Chemical Innovation in Solar Fuels (CHE-1305124) and in part by The Dow Chemical Company through a university partnership program (Agreement # 227027AK). \n\nThere are no conflicts to declare.",
revision_no = "19",
abstract = "The products from the 193 nm irradiation of triphenylsulfonium nonaflate (TPS) embedded in a poly(methyl methacrylate) (PMMA) film have been characterized. The analysis of the photoproduct formation was performed using chromatographic techniques including HPLC, GPC and GC-MS as well as UV-vis and NMR spectroscopic methods. Two previously unreported TPS photoproducts, triphenylene and dibenzothiophene, were detected; additionally, GPC and DOSY-NMR spectroscopic analyses after irradiation suggested that TPS fragments had been incorporated into the polymer film. The irradiation of acetonitrile solutions containing 10% w/v PMMA and 1% w/v TPS in a 1 cm-path-length cuvette showed only a trace amount of triphenylene or dibenzothiophene, indicating that topochemical factors were important for the formation of these molecules. The accumulated evidence indicates that both products were formed by in-cage, secondary photochemical reactions: 2-(phenylthio)biphenyl to triphenylene, and diphenylsulfide to dibenzothiophene.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/83220,
title ="Ultrafast Wiggling and Jiggling: Ir_2(1,8-diisocyanomenthane)_4^(2+)",
author = "Pižl, Martin and Hunter, Bryan M.",
journal = "Journal of Physical Chemistry A",
volume = "121",
number = "48",
pages = "9275-9283",
month = "December",
year = "2017",
doi = "10.1021/acs.jpca.7b10215",
issn = "1089-5639",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20171115-101044605",
note = "© 2017 American Chemical Society. \n\nReceived: October 15, 2017; Published: November 13, 2017. \n\nThis work was supported by the Czech Science Foundation Grant 17-011375, NSF CCI Solar Fuels Program (CHE-1305124) and STFC (UK). B.M.H. is a Fellow of the Resnick Sustainability Institute at Caltech. Additional support was provided by the Arnold and Mabel Beckman Foundation, the Ministry of Education of the Czech Republic (Grant LTC17052), and COST Action CM1405. \n\nThe authors declare no competing financial interest.",
revision_no = "24",
abstract = "Binuclear complexes of d^8 metals (Pt^(II), Ir^I, Rh^I,) exhibit diverse photonic behavior, including dual emission from relatively long-lived singlet and triplet excited states, as well as photochemical energy, electron, and atom transfer. Time-resolved optical spectroscopic and X-ray studies have revealed the behavior of the dimetallic core, confirming that M–M bonding is strengthened upon dσ* → pσ excitation. We report the bridging ligand dynamics of Ir2(1,8-diisocyanomenthane)_4^(2+)(Ir(dimen)), investigated by fs–ns time-resolved IR spectroscopy (TRIR) in the region of C≡N stretching vibrations, ν(C≡N), 2000–2300 cm^(–1). The ν(C≡N) IR band of the singlet and triplet dσ*pσ excited states is shifted by −22 and −16 cm^(–1) relative to the ground state due to delocalization of the pσ LUMO over the bridging ligands. Ultrafast relaxation dynamics of the ^1dσ*pσ state depend on the initially excited Franck–Condon molecular geometry, whereby the same relaxed singlet excited state is populated by two different pathways depending on the starting point at the excited-state potential energy surface. Exciting the long/eclipsed isomer triggers two-stage structural relaxation: 0.5 ps large-scale Ir–Ir contraction and 5 ps Ir–Ir contraction/intramolecular rotation. Exciting the short/twisted isomer induces a ∼5 ps bond shortening combined with vibrational cooling. Intersystem crossing (70 ps) follows, populating a ^3dσ*pσ state that lives for hundreds of nanoseconds. During the first 2 ps, the ν(C≡N) IR bandwidth oscillates with the frequency of the ν(Ir–Ir) wave packet, ca. 80 cm^(–1), indicating that the dephasing time of the high-frequency (16 fs)^(−1) C≡N stretch responds to much slower (∼400 fs)^(−1)Ir–Ir coherent oscillations. We conclude that the bonding and dynamics of bridging di-isocyanide ligands are coupled to the dynamics of the metal–metal unit and that the coherent Ir–Ir motion induced by ultrafast excitation drives vibrational dephasing processes over the entire binuclear cation.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/81675,
title ="Two-photon spectroscopy of tungsten(0) arylisocyanides using nanosecond-pulsed excitation",
author = "Takematsu, Kana and Wehlin, Sara A. M.",
journal = "Dalton Transactions",
volume = "46",
number = "39",
pages = "13188-13193",
month = "October",
year = "2017",
doi = "10.1039/c7dt02632c",
issn = "1477-9226",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170921-104309376",
note = "© 2017 The Royal Society of Chemistry. \n\nThe article was received on 19 Jul 2017, accepted on 11 Sep 2017 and first published on 21 Sep 2017. \n\nResearch was supported by CCI Solar Fuels (NSF CHE-1305124) and the Arnold and Mabel Beckman Foundation. \n\nThere are no conflicts to declare.",
revision_no = "22",
abstract = "The two-photon absorption (TPA) cross sections (δ) for tungsten(0) arylisocyanides (W(CNAr)6) were determined in the 800–1000 nm region using two-photon luminescence (TPL) spectroscopy. The complexes have high TPA cross sections, in the range 1000–2000 GM at 811.8 nm. In comparison, the cross section at 811.8 nm for tris-(2,2′-bipyridine)ruthenium(II), [Ru(bpy)_3]^(2+), is 7 GM. All measurements were performed using a nanosecond-pulsed laser system.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/81922,
title ="Driving Force Dependence of Electron Transfer from Electronically Excited [Ir(COD)(μ-Me_2pz)]_2 to Photo-Acid Generators",
author = "Sattler, Wesley and Rachford, Aaron A.",
journal = "Journal of Physical Chemistry A",
volume = "121",
number = "40",
pages = "7572-7575",
month = "October",
year = "2017",
doi = "10.1021/acs.jpca.7b07777",
issn = "1089-5639",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170929-115128097",
note = "© 2017 American Chemical Society. \n\nReceived: August 4, 2017; Revised: September 10, 2017; Published: September 28, 2017. \n\nThis work was supported in part by the National Science Foundation Center for Chemical Innovation in Solar Fuels (Grant CHE-1305124), Center for Chemical Innovation postdoctoral fellowship to W.S. This work was also funded in part by The Dow Chemical Company through a university partnership program (Agreement 227027AH). \n\nThe authors declare no competing financial interest.",
revision_no = "16",
abstract = "We report the rates of electron transfer (ET) reactions of electronically excited [Ir(COD)(μ-Me_2pz)]_2 with onium salt photoacid generators (PAGs). The reduction potentials of the PAGs span a large electrochemical window that allows determination of the driving force dependence of the ET reactions. Rate constants of ET from electronically excited [Ir(COD)(μ-Me_2pz)]_2 to onium PAGs are determined by the reaction driving force until the diffusion limit in acetonitrile is reached.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/82541,
title ="Electrochemistry in ionic liquids: Case study of a manganese corrole",
author = "McNicholas, Brendon J. and Blumenfeld, Carl",
journal = "Russian Journal of Electrochemistry",
volume = "53",
number = "10",
pages = "1189-1193",
month = "October",
year = "2017",
doi = "10.1134/S1023193517100068",
issn = "1023-1935",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20171020-140056026",
note = "© 2017 Pleiades Publishing, Ltd. \n\nReceived January 6, 2017; in final form, February 3, 2017. First Online: 21 October 2017. \n\nThis paper is the authors’ contribution to the special issue of Russian Journal of Electrochemistry dedicated to the 100th anniversary of the birth of the outstanding Soviet electrochemist Veniamin G. Levich. \n\nThe article is published in the original. \n\nThe authors thank Shabnam Hematian for helpful discussions. This work was supported by the NSF CCI Solar Fuels Program (CHE-1305124) (H.B.G. and J. R. W.). Additional support was provided by King Fahd University of Petroleum and Minerals (R.H.G.). The authors declare no competing financial interest",
revision_no = "10",
abstract = "Voltammetry of [5,10,15-tris(pentafluorophenylcorrole)]Mn(III) was investigated in four different ionic liquids (ILs): 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIm-TFSI); 1-ethyl-3-methylimidazolium ethylsulfate (EMIm-EtOSO_3); 1-ethyl-3-methylimidazolium triflate (EMIm-OTf); and 1-ethyl-3-methylimidazolium tetracyanoborate (EMIm-TCB). We found that Mn^(IV/III) E_(1/2) values depend on IL counter anion: OTf–< EtOSO_3− < TFSI− < TCB−. In EMIm-TCB and BMIm- TFSI, reversible, diffusion-controlled MnIV/III reactions occurred, as evidenced in each case by the ratio of anodic to cathodic diffusion coefficients over a range of scan rates. Axial coordination was evidenced by a cathodic to anodic diffusion coefficient ratio greater than one, an increasing cathodic to anodic peak current ratio with increasing scan rate, and a split Soret band in the UV-vis spectrum of the complex.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/81148,
title ="Role of Ligand Protonation in Dihydrogen Evolution from a Pentamethylcyclopentadienyl Rhodium Catalyst",
author = "Johnson, Samantha I. and Gray, Harry B.",
journal = "Inorganic Chemistry",
volume = "56",
number = "18",
pages = "11375-11386",
month = "September",
year = "2017",
doi = "10.1021/acs.inorgchem.7b01698",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170905-141449913",
note = "© 2017 American Chemical Society. \n\nReceived: July 18, 2017; Published: September 1, 2017. \n\nThe authors thank Dr. Jay Winkler, Dr. Robert Nielsen, Dr. Sijia Dong, Dr. Davide Lionetti, Yufeng Huang, and Sydney Corona for numerous helpful discussions. This work was supported by the US National Science Foundation through the CCI Solar Fuels Program (CHE-1305124) and the Resnick Sustainability Institute at Caltech (fellowship to S.I.J.). J.D.B. was supported during preparation of this manuscript by an award from the State of Kansas through the University of Kansas New Faculty General Research Fund. \n\nThe authors declare no competing financial interest.",
revision_no = "21",
abstract = "Recent work has shown that Cp*Rh(bpy) [Cp* = pentamethylcyclopentadienyl, bpy = 2,2′- bipyridine] undergoes endo protonation at the [Cp*] ligand in the presence of weak acid (Et_3NH^+; pK_a = 18.8 in MeCN). Upon exposure to stronger acid (e.g., DMFH+; pK_a = 6.1), hydrogen is evolved with unity yield. Here, we study the mechanisms by which this catalyst evolves dihydrogen using density functional theory (M06) with polarizable continuum solvation. The calculations show that the complex can be protonated by weak acid first at the metal center with a barrier of 3.2 kcal/mol; this proton then migrates to the ring to form the detected intermediate, a rhodium(I) compound bearing endo η^4-Cp*H. Stronger acid is required to evolve hydrogen, which calculations show happens via a concerted mechanism. The acid approaches and protonates the metal, while the second proton simultaneously migrates from the ring with a barrier of ∼12 kcal/mol. Under strongly acidic conditions, we find that hydrogen evolution can proceed through a traditional metal–hydride species; protonation of the initial hydride to form an H–H bond occurs before migration of the hydride (in the form of a proton) to the [Cp*] ring (i.e., H–H bond formation is faster than hydride–proton tautomerization). This work demonstrates the role of acid strength in accessing different mechanisms of hydrogen evolution. Calculations also predict that modification of the bpy ligand by a variety of functional groups does not affect the preference for [Cp*] protonation, although the driving force for protonation changes. However, we predict that exchange of bpy for a bidentate phosphine ligand will stabilize a rhodium(III) hydride, reversing the preference for bound [Cp*H] found in all computed bpy derivatives and offering an appealing alternative ligand platform for future experimental and computational mechanistic studies of H_2 evolution.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77775,
title ="Conservation of vibrational coherence in ultrafast electronic relaxation: The case of diplatinum complexes in solution",
author = "Monni, Roberto and Auböck, Gerald",
journal = "Chemical Physics Letters",
volume = "683",
pages = "112-120",
month = "September",
year = "2017",
doi = "10.1016/j.cplett.2017.02.071",
issn = "0009-2614",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170525-154729378",
note = "© 2017 Elsevier B.V. \n\nReceived 25 January 2017, Accepted 21 February 2017, Available online 24 February 2017. \n\nThis work was supported by the Swiss NSF via the NCCR:MUST, contract n° 200021_137717 and IZK0Z2_150425. We thank Yan Choi Lam and Tania Darnton for supplying samples (work at Caltech was supported by NSF CCI Solar Fuels CHE-1305124). Petr Pospíšil (J. Heyrovský Inst.) and Igor Sazanovich (Rutherford Appleton Lab, UK) are thanked for their help with measurements of stationary emission-excitation and nanosecond time-resolved spectra, respectively. We also thank the European collaboration program COST Action CM1202, the Czech Ministry of Education grant LD14129, and the Czech Science Foundation grant 17-011375 for support.",
revision_no = "19",
abstract = "We report the results of ultrafast transient absorption studies of tetrakis(μ-pyrophosphito)diplatinate(II), [Pt_2(μ-P_2O_5H_2)_4]^(4−) (Pt(pop)) and its perfluoroborated derivative [Pt_2(μ-P_2O_5(BF_2)_4]^(4−) (Pt(pop-BF_2)) in water and acetonitrile upon excitation of high lying (<300 nm) UV absorption bands. We observe an ultrafast relaxation channel from high lying states to the lowest triplet state that partly (Pt(pop) in H_2O, Pt(pop-BF_2)) or fully (Pt(pop) in MeCN) bypasses the lowest singlet excited state. As a consequence, vibrational wave packets are detected in the lowest triplet state and/or the lowest excited singlet of both complexes, even though the electronic relaxation cascade spans ca. 2 and 1.3 eV, respectively. In the case of Pt(pop-BF_2), coherent wave packets generated by optical excitation of the lowest singlet ^1A_(2u) state also are reported. Overall, the reported dephasing times of the Pt-Pt oscillator in the ground, singlet and triplet states do not depend much on the solvent or the molecular structure.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/80464,
title ="Photoelectrochemical Behavior of a Molecular Ru-Based Water-Oxidation Catalyst Bound to TiO_2-Protected Si Photoanodes",
author = "Matheu, Roc and Moreno-Hernandez, Ivan A.",
journal = "Journal of the American Chemical Society",
volume = "139",
number = "33",
pages = "11345-11348",
month = "August",
year = "2017",
doi = "10.1021/jacs.7b06800",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170816-083201966",
note = "© 2017 American Chemical Society. \n\nReceived: June 30, 2017; Published: August 7, 2017. \n\nThe National Science Foundation under NSF Center CHE-1305124 provided support for H.B.G., I.M.H., N.S.L., B.S.B., and R.M. and for supplies at Caltech, I.M.H. was supported by a NSF Graduate Research Fellowship (Grant No. DGE-1144469). Instrumentation support was also provided by the Molecular Materials Resource Center of the Beckman Institute at California Institute of Technology. R.M., A.L., and X.S. acknowledge MINECO and FEDER (CTQ2016-80058-R, CTQ2015-64261-R, SEV 2013-0319, ENE2016-82025-REDT, CTQ2016-81923-REDC), AGAUR (2014-SGR-915), and “La Caixa” foundation. We acknowledge Dr. K. Sun for helpful discussions. \n\nThe authors declare no competing financial interest.",
revision_no = "23",
abstract = "A hybrid photoanode based on a molecular water oxidation precatalyst was prepared from TiO_2-protected n- or p+-Si coated with multiwalled carbon nanotubes (CNT) and the ruthenium-based water oxidation precatalyst [Ru^(IV)(tda)(py-pyr)_2(O)], 1(O) (tda^(2–) is [2,2′:6′,2″-terpyridine]-6,6″-dicarboxylato and py-pir is 4-(pyren-1-yl)-N-(pyridin-4-ylmethyl)butanamide). The Ru complex was immobilized by π–π stacking onto CNTs that had been deposited by drop casting onto Si electrodes coated with 60 nm of amorphous TiO_2 and 20 nm of a layer of sputtered C. At pH = 7 with 3 Sun illumination, the n-Si/TiO_2/C/CNT/[1+1(O)] electrodes exhibited current densities of 1 mA cm^(–2) at 1.07 V vs NHE. The current density was maintained for >200 min at a constant potential while intermittently collecting voltammograms that indicated that over half of the Ru was still in molecular form after O_2 evolution.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/74420,
title ="Electronic structures and photophysics of d^8-d^8 complexes",
author = "Gray, Harry B. and Záliš, Stanislav",
journal = "Coordination Chemistry Reviews",
volume = "345",
pages = "297-317",
month = "August",
year = "2017",
doi = "10.1016/j.ccr.2017.01.008",
issn = "0010-8545",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170221-084923487",
note = "© 2017 Elsevier B.V. \n\nReceived 29 October 2016, Revised 17 January 2017, Accepted 18 January 2017, Available online 21 January 2017. \n\nWe thank our colleagues for interesting discussions of d^8-d^8 chemistry as well as sharing some (yet) unpublished data, most especially Majed Chergui, Ivano Tavernelli, Roberto Moni, and Gloria Capano (EFPFL, Switzerland); and Jay Winkler, Bryan Hunter, and Yan-Choi Lam (Caltech). This work was supported by the NSF CCI Solar Fuels Program (CHE-1305124), the Arnold and Mabel Beckman Foundation, the Ministry of Education of the Czech Republic - grant LH13015, and the COST Action CM1405. \n\nDedicated to Barry Lever, consummate scholar and treasured friend, in recognition of his deep and lasting contributions to coordination chemistry.",
revision_no = "16",
abstract = "Research on d^8-d^8 complexes is being actively pursued, owing, in part, to newly developed time-resolved optical, IR, and X-ray methods that directly interrogate bonding changes upon excitation. Our review covers work on the ground- and electronic excited states, as well as the oxidized and reduced forms, of these complexes. Recent experimental and theoretical results add a new chapter to the rich history of d^8-d^8 spectroscopic and chemical behavior.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/81348,
title ="Catalysts for solar-driven water splitting",
author = "Gray, Harry",
pages = "INOR-309",
month = "August",
year = "2017",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170912-100434963",
note = "© 2017 American Chemical Society.",
revision_no = "9",
abstract = "We are working on heterogeneous inorg. catalysts that could be part of scalable solar fuel devices. We have found that\nmaterials such as Ni-Mo nanopowders and metal phosphide nanocrystals have catalytic efficiencies near that of platinum for redn. of protons in aq. solns. A major challenge is to find scalable materials that can be employed as active catalysts in integrated photoanodes for prodn. of oxygen from water, as required for the generation of protons and electrons for combination at photocathodes. We have found that mixed-metal nanosheet hydroxides made by pulsed laser ablation of precursors in water are very active water oxidn. catalysts. We are working on the structures and mechanisms of these nanosheet materials to aid in the design and construction of more efficient and robust integrated photoanodes for water splitting.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/81347,
title ="Living with oxygen",
author = "Gray, Harry",
pages = "INOR-25",
month = "August",
year = "2017",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170912-100243787",
note = "© 2017 American Chemical Society.",
revision_no = "9",
abstract = "Metal-oxos are active intermediates in reactions crit. for life on Planet Earth, water oxidn. to oxygen in photosynthesis, and oxygen redn. in respiration. The ligand field theory of metal-oxo electronic structure, which accounts for the spectroscopic and magnetic properties of these complexes, also provides a platform for discussion of their roles in the mechanisms of inorg. and biol. redox reactions.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/81299,
title ="Mechanistic investigations of a recombinant laccase from Thermus thermophilus HB27",
author = "Hematian, Shabnam and Sanders, Brian C.",
pages = "INOR-800",
month = "August",
year = "2017",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170911-134714732",
note = "© 2017 American Chemical Society.",
revision_no = "12",
abstract = "Laccases belong to the family of multicopper oxidases (MCOs) that couple oxidn. of a wide spectrum of substrates to the four-electron redn. of dioxygen (O_2) to water. Laccases typically contain four copper ion sites arranged in two centers: one type 1 blue copper center and one trinuclear cluster (TNC) consisting of one type 2 copper and a binuclear type 3 copper pair. Dioxygen binding, activation, and redn. are believed to proceed at the TNC with electrons delivered from the type 1 site. The precise mechanism of coupling O_2 redn. to substrate oxidn. is a subject of considerable fundamental and technol. significance. Of particular interest is the mechanism by which laccases oxidize refractory substrates such as phenols and lignin. To gain deeper insight into laccase catalysis, we have cloned the gene for a recombinant multicopper oxidase from the hyperthermophilic bacterium Thermus thermophilus HB27 (Tth-MCO), and expressed the enzyme as a 6Histagged protein in Escherichia coli. Several mutants of the recombinant enzyme have been prepd. by sitedirected mutagenesis and investigated using various structural and spectroscopic techniques. Our recent results\non the reaction pathways and intermediates involved in the enzymic reaction will be discussed.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/78892,
title ="Hole Hopping through Tryptophan in Cytochrome P450",
author = "Ener, Maraia E. and Gray, Harry B.",
journal = "Biochemistry",
volume = "56",
number = "28",
pages = "3531-3538",
month = "July",
year = "2017",
doi = "10.1021/acs.biochem.7b00432",
issn = "0006-2960",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170710-110217062",
note = "© 2017 American Chemical Society. This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes. \n\nReceived: May 5, 2017; Revised: June 16, 2017; Published: July 9, 2017. \n\nResearch reported in this publication was supported by the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health under Award Number R01DK019038. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. Additional support was provided by the Arnold and Mabel Beckman Foundation. \n\nThe authors declare no competing financial interest.",
revision_no = "25",
abstract = "Electron-transfer kinetics have been measured in four conjugates of cytochrome P450 with surface-bound Ru-photosensitizers. The conjugates are constructed with enzymes from Bacillus megaterium (CYP102A1) and Sulfolobus acidocaldarius (CYP119). A W96 residue lies in the path between Ru and the heme in CYP102A1, whereas H76 is present at the analogous location in CYP119. Two additional conjugates have been prepared with (CYP102A1)W96H and (CYP119)H76W mutant enzymes. Heme oxidation by photochemically generated Ru^(3+) leads to P450 compound II formation when a tryptophan residue is in the path between Ru and the heme; no heme oxidation is observed when histidine occupies this position. The data indicate that heme oxidation proceeds via two-step tunneling through a tryptophan radical intermediate. In contrast, heme reduction by photochemically generated Ru+ proceeds in a single electron tunneling step with closely similar rate constants for all four conjugates.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/73614,
title ="Mixed-Metal Tungsten Oxide Photoanode Materials Made by Pulsed-Laser in Liquids Synthesis",
author = "Blumenfeld, Carl M. and Lau, Marcus",
journal = "ChemPhysChem",
volume = "18",
number = "9",
pages = "1091-1100",
month = "May",
year = "2017",
doi = "10.1002/cphc.201601285",
issn = "1439-4235",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170123-100309949",
note = "© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. \n\nManuscript received: November 22, 2016;\nAccepted Article published: January 17, 2017;\nFinal Article published: February 2, 2017.\n\nWe thank George Rossman for help with optical spectroscopy, Chi Ma for help with SEM (both Division of Geological and Planetary Sciences Caltech), and Nathan Dalleska (Environmental Analysis Center at Caltech) for help with ICP-MS. We performed research in the Laser Resource Center and the Molecular Materials Research Center of the Beckman Institute of the California Institute of Technology. The NSF CCI Solar Fuels Program (CHE-1305124) and the Arnold and Mabel Beckman Foundation supported this work.\n\nConflict of interest:\nThe authors declare no conflict of interest.",
revision_no = "15",
abstract = "Globally scalable sunlight-driven devices that convert solar energy into storable fuels will require efficient light absorbers that are made of non-precious elements. Suitable photoanode materials are yet to be discovered. Here we utilised the timesaving nature of pulsed-laser in liquids synthesis and prepared a series of neat and mixed-metal tungsten oxide photoanode materials to investigate the effect of ad-metals on optical and photocurrent generation properties. We obtained sub-μm-sized materials with different colours from W, Al, Ta, or first-row transition metal targets in water or aqueous ammonium metatungstate solutions. We observed metastable polymorphs of WO3 and tungsten oxides with varying degrees of oxygen deficiency. Pulsed-laser in liquids synthesis of Ni in ammonium metatungstate solutions produced hollow spheres (with ≤ 6% Ni with respect to W). Photocurrent generation in strong aqueous acid was highest in mixed-metal tungsten oxide photoanode materials with around 5% of iron or nickel.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77154,
title ="Electronic structures of diplatinum complexes",
author = "Gray, Harry B.",
pages = "INOR-6",
month = "April",
year = "2017",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170503-105050009",
note = "© 2017 American Chemical Society.",
revision_no = "10",
abstract = "The unusual photophys. properties of d8d8 complexes have intrigued inorg. chemists for many years. Nilay\nHazari and I (with other good friends) worked on dipalladium electronic structures during the time he was in\nthe Bercaw-Labinger group at Caltech. In my lecture in his honor, I will discuss the latest developments in the\nfield, with emphasis on work by Jay Winkler and Yan Choi Lam on diplatinum photophysics, and by Bryan\nHunter, Tania Darnton, Mike Hill, Tony Vlcek, and Standa Zalis on rare (unique) 6p-sigma-bonded complexes.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77148,
title ="Metal-oxos in chemistry and biology",
author = "Gray, Harry B.",
pages = "INOR-608",
month = "April",
year = "2017",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170503-103335721",
note = "© 2017 American Chemical Society.",
revision_no = "8",
abstract = "The dianionic oxo ligand occupies a very special place in coordination chem., owing to its ability to stabilize high oxidn. states of metals. My first papers on the ligand field theory of multiple bonding in metal-oxos appeared in the first vol. of Inorg. Chem. The theory, which accounts for the optical and EPR spectroscopic properties of these complexes, also predicts that there must be an \"oxo wall\" between Fe-Ru-Os and Co-Rh-Ir in the periodic table. There have been many attempts to break down the wall, but it is still in pretty good shape!. I will review this early work, then discuss the roles metal-oxos play in two of the most\nimportant chem. reactions on planet Earth, hydrocarbon oxygenation catalyzed by cytochrome P 450, and solar-driven water oxidn. catalyzed by photosystem-II. Water splitting catalyzed by inorg. materials also is of great current interest. In this area, recent work has shown that Fe(VI)-oxos likely are key intermediates in water oxidn. catalyzed by robust LDH-(Fe,Ni)-nanosheets.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77150,
title ="Pulsed-laser synthesis of advanced nanomaterials for water-oxidation catalysis and sunlight capture",
author = "Mueller, Astrid M. and Winkler, Jay R.",
pages = "INOR-71",
month = "April",
year = "2017",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170503-103650482",
note = "© 2017 American Chemical Society.",
revision_no = "10",
abstract = "Conversion of solar energy into storable fuels is essential to meet future global energy demands. Efficient, robust catalysts and light absorbers that are exclusively made of non-precious elements are imperative for a sustainable energy economy. In pulsed-laser synthesis, nanoparticles are formed by very rapid cooling of a laser-induced plasma comprised of elements from the solid target and the surrounding liq. We achieved control of nanoparticle size, polydispersity, and compn. by choice of laser pulse energy and the chem. nature of the solid target or liq. medium. We have readily prepd. multi-metal nanomaterials with tailored compns. by adding metal ions into the aq. liq.; our approach allowed us to rapidly optimize highly active, robust [NiFe]-layered double hydroxide nanocatalysts for water oxidn. in base. Choice of dissolved anions mattered for zinc or copper-based nanomineral formation. We also applied our method to make mixed-metal tungsten oxide\nnanomaterials for oxidative photocatalysis in aq. acid.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77149,
title ="Sixty years of inorganic chemistry",
author = "Gray, Harry B.",
pages = "INOR-8",
month = "April",
year = "2017",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170503-103511240",
note = "© 2017 American Chemical Society.",
revision_no = "10",
abstract = "I was a graduate student at Northwestern when DIC was founded. I have witnessed great advances in our field over the the last sixty years. I will tell a few stories to kick off the celebration.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77152,
title ="Solar fuels science",
author = "Gray, Harry B.",
pages = "INOR-194",
month = "April",
year = "2017",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170503-104240786",
note = "© 2017 American Chemical Society.",
revision_no = "9",
abstract = "We and many others are designing solar-driven mol. machines that could be used on a global scale to store solar energy by splitting water into its elemental components. We are investigating the structures and mechanisms of hydrogen evolving catalysts made from Earth abundant elements such as cobalt, iron, and nickel. We also are employing pulsed laser ablation in water for synthesis of robust oxygen evolving catalysts. To aid our research, we have recruited hundreds of students to join a Solar Army whose mission is the discovery of new materials for the prodn. of solar fuels.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/74435,
title ="Electronic Structures of Reduced and Superreduced Ir_2(1,8-diisocyanomenthane)_4^(n+) Complexes",
author = "Záliš, Stanislav and Hunter, Bryan M.",
journal = "Inorganic Chemistry",
volume = "56",
number = "5",
pages = "2874-2883",
month = "March",
year = "2017",
doi = "10.1021/acs.inorgchem.6b03001",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170221-141613246",
note = "© 2017 American Chemical Society. \n\nReceived: December 8, 2016; Published: February 20, 2017. \n\nThis work was supported by the NSF CCI Solar Fuels Program (CHE-1305124). Additional support was provided by the Arnold and Mabel Beckman Foundation, the Ministry of Education of the Czech Republic (grant LD14129), and COST Actions CM1202 and CM1405.",
revision_no = "21",
abstract = "Molecular and electronic structures of Ir_2(1,8-diisocyanomenthane)_4^(n+) (Ir(dimen)^(n+)) complexes have been investigated by DFT for n = 2, 1, 0 (abbreviated 2+, 1+, 0). Calculations reproduced the experimental structure of 2+, ν(C≡N) IR, and visible absorption spectra of all three oxidation states, as well as the EPR spectrum of 1+. We have shown that the two reduction steps correspond to successive filling of the Ir–Ir pσ orbital. Complexes 2+ and 1+ have very similar structures with 1+ having a shorter Ir–Ir distance. The unpaired electron density in 1+ is delocalized along the Ir–Ir axis and over N atoms of the eight C≡N– ligands. The second reduction step 1+ → 0 changes the Ir(CN−)_4 coordination geometry at each Ir site from approximately planar to seesaw whereby one −N≡C–Ir–C≡N– moiety is linear and the other bent at the Ir (137°) as well as N (146°) atoms. Although complex 0 is another example of a rare (pσ)2 dimetallic species (after [Pt_2(μ-P_2O_5(BF_2)_2)_4]^(6–), J. Am. Chem. Soc. 2016, 138, 5699), the redistribution of lower lying occupied molecular orbitals increases electron density predominantly at the bent C≡N– ligands whose N atoms are predicted to be nucleophilic reaction centers.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77747,
title ="Foreword",
author = "Aukauloo, Ally and Gray, Harry B.",
journal = "Comptes Rendus Chimie",
volume = "20",
number = "3",
pages = "207",
month = "March",
year = "2017",
doi = "10.1016/j.crci.2016.03.016",
issn = "1631-0748",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170525-080332378",
note = "© 2016 Académie des sciences. Published by Elsevier Masson SAS. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). \n\nAvailable online 27 April 2016.",
revision_no = "7",
abstract = "UNESCO proclaimed 2015 as the international year of light and light-based technologies. This internationally celebrated event has opened the way for thoughtful discussions of how light-based technologies could help mankind make a transition to a sustainable planet. Light plays a key role in our daily lives and will become even more important in a world increasingly dependent on technologies that require energy to function. The energy that has led to our technological advancement is mainly based on fossil fuels. Their extensive use has led to a steady increase in CO_2 emissions, which in turn has drastically affected the global climate. After several political attempts to reach a common objective to reverse the current trends in emissions, a historic agreement was reached at COP21 held in Paris in December 2015, the year of light. Remarkably, fully 195 countries are engaged in cutting emissions of greenhouse gases. We view this event as an urgent call to chemists and other scientists to develop new materials and methods for the production of clean solar fuels. The grand challenge facing us is the development of scalable integrated artificial photosynthetic devices built from robust materials for optimal light capture and conversion.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/71389,
title ="Fighting Cancer with Corroles",
author = "Teo, Ruijie D. and Hwang, Jae Youn",
journal = "Chemical Reviews",
volume = "117",
number = "4",
pages = "2711-2729",
month = "February",
year = "2017",
doi = "10.1021/acs.chemrev.6b00400",
issn = "0009-2665",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20161024-122920631",
note = "© 2016 American Chemical Society. \n\nReceived: June 24, 2016. Publication Date (Web): October 19, 2016. \n\n\nSpecial Issue: Expanded, Contracted, and Isomeric Porphyrins. \n\nWe have greatly enjoyed working with Lali Medina-Kauwe, Daniel Farkas, and many other colleagues on research discussed in this review. This work was supported by a Caltech-COH grant (J.T., H.B.G., and Z.G.), the AACR–Thomas J. Bardos Science Education Award (R.D.T.), the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (NRF-2014R1A1A2054934, NRF-2014M3A9D7070668), and Samsung Research Funding for Future Technology (J.Y.H.). Research in the Beckman Institute Laser Center at Caltech was supported by NIH R01 DK019038, while research performed at Technion was supported by the Israel Science Foundation. \n\nThe authors declare no competing financial interest.",
revision_no = "20",
abstract = "Corroles are exceptionally promising platforms for the development of agents for simultaneous cancer-targeting imaging and therapy. Depending on the element chelated by the corrole, these theranostic agents may be tuned primarily for diagnostic or therapeutic function. Versatile synthetic methodologies allow for the preparation of amphipolar derivatives, which form stable noncovalent conjugates with targeting biomolecules. These conjugates can be engineered for imaging and targeting as well as therapeutic function within one theranostic assembly. In this review, we begin with a brief outline of corrole chemistry that has been uniquely useful in designing corrole-based anticancer agents. Then we turn attention to the early literature regarding corrole anticancer activity, which commenced one year after the first scalable synthesis was reported (1999–2000). In 2001, a major advance was made with the introduction of negatively charged corroles, as these molecules, being amphipolar, form stable conjugates with many proteins. More recently, both cellular uptake and intracellular trafficking of metallocorroles have been documented in experimental investigations employing advanced optical spectroscopic as well as magnetic resonance imaging techniques. Key results from work on both cellular and animal models are reviewed, with emphasis on those that have shed new light on the mechanisms associated with anticancer activity. In closing, we predict a very bright future for corrole anticancer research, as it is experiencing exponential growth, taking full advantage of recently developed imaging and therapeutic modalities.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/71730,
title ="Earth-Abundant Heterogeneous Water Oxidation Catalysts",
author = "Hunter, Bryan M. and Gray, Harry B.",
journal = "Chemical Reviews",
volume = "116",
number = "22",
pages = "14120-14136",
month = "November",
year = "2016",
doi = "10.1021/acs.chemrev.6b00398",
issn = "0009-2665",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20161104-074948999",
note = "© 2016 American Chemical Society. \n\nReceived: June 23, 2016. Publication Date (Web): October 31, 2016. \n\nWe thank Dave Britt and Troy Stich for helpful discussions. Research was performed in the Laser Resource Center and the Molecular Materials Research Center of the Beckman Institute of the California Institute of Technology. The NSF CCI Solar Fuels Program (CHE-1305124) and the Arnold and Mabel Beckman Foundation supported this work. B.M.H. is a fellow of the Resnick Sustainability Institute at Caltech.",
revision_no = "14",
abstract = "Water oxidation is a key chemical transformation for the conversion of solar energy into chemical fuels. Our review focuses on recent work on robust earth-abundant heterogeneous catalysts for the oxygen-evolving reaction (OER). We point out that improvements in the performance of OER catalysts will depend critically on the success of work aimed at understanding reaction barriers based on atomic-level mechanisms. We highlight the challenge of obtaining acid-stable OER catalysts, with proposals for elements that could be employed to reach this goal. We suggest that future advances in solar fuels science will be accelerated by the development of new methods for materials synthesis and characterization, along with in-depth investigations of redox mechanisms at catalytic surfaces.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/71632,
title ="Structural Stability of Intelectin-1",
author = "Kozak, John J. and Gray, Harry B.",
journal = "Journal of Physical Chemistry B",
volume = "120",
number = "46",
pages = "11888-11896",
month = "November",
year = "2016",
doi = "10.1021/acs.jpcb.6b08691",
issn = "1520-6106",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20161031-151245906",
note = "© 2016 American Chemical Society. \n\nReceived 28 August 2016. Publication Date (Web): October 26, 2016. \n\nWe are delighted that our work is included in the special issue of Journal of Physical Chemistry in honor of Professor Mark Gordon, an all-around good guy who has made groundbreaking contributions to the quantum chemistry of atoms and molecules. His development of (the computational program) GAMESS has had a big impact on the field. One of the authors (JJK) is indebted to Dr. K. Wangkanont for clarifying details of the crystal structure of the lectin proteins cited in the Discussion. We thank the National Institutes of Health (R01 DK 019038 to HBG) for support of work performed at the California Institute of Technology. Financial support for R.A.G.-L. was provided by the Howard Hughes Medical Institute Research Program from Pomona College. The molecular graphics images were produced using the Chimera package from the Computer Graphics Laboratory, University of California, San Francisco (supported by NIH P41 RR-01081).",
revision_no = "19",
abstract = "We study the structural stability of helical and non-helical regions in chain A of human intelectin-1. Using a geometrical model introduced previously, a computational analysis based on the recently reported crystal structure of this protein by Kiessling et al. [Nature Struct. Mole. Bio. 22 (2015), 603] is carried out to quantify the resiliency of the native state to steric perturbations. Response to these perturbations is characterized by calculating, relative to the native state, the lateral, radial and angular displacements of n-residue segments of the polypeptide chain centered on each residue. By quantifying the stability of the protein through six stages of unfolding, we are able to identify regions in chain A of intelectin-1 which are markedly affected by structural perturbations versus those which are relatively unaffected, the latter suggesting that the native-state geometry of these regions is essentially conserved. Importantly, residues in the vicinity of calcium ions comprise a conserved region, suggesting that Ca ions play a role not only in the coordination of carbohydrate hydroxyl groups, but in preserving the integrity of the structure.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/70775,
title ="Intersystem Crossing in Diplatinum Complexes",
author = "Lam, Yan Choi and Gray, Harry B.",
journal = "Journal of Physical Chemistry A",
volume = "120",
number = "39",
pages = "7671-7676",
month = "October",
year = "2016",
doi = "10.1021/acs.jpca.6b07891",
issn = "1089-5639",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20161003-160458042",
note = "© 2016 American Chemical Society. \n\nReceived: August 4, 2016. Revised: September 13, 2016. \n\nPublication Date (Web): September 26, 2016.\n\nWe have enjoyed several stimulating discussions with Tony Vlček and Hartmut Yersin about the nature of excited-state decay pathways in diplatinum complexes. We thank them for their contributions to the field. Our work was supported by NSF CCI Solar Fuels (Grant CHE-1305124). \n\nThe authors declare no competing financial interest.",
revision_no = "22",
abstract = "Intersystem crossing (ISC) in solid [(C_4H_9)_4N]4[Pt_2(μ-P_2O_5(BF_2)_2)_4], abbreviated Pt(pop-BF2), is remarkably slow for a third-row transition metal complex, ranging from τ_(ISC) ≈ 0.9 ns at 310 K to τ_(ISC) ≈ 29 ns below 100 K. A classical model based on Boltzmann population of one temperature-independent and two thermally activated pathways was previously employed to account for the ISC rate behavior. An alternative we prefer is to treat Pt(pop-BF_2) ISC quantum mechanically, using expressions for multiphonon radiationless transitions. Here we show that a two-channel model with physically plausible parameters can account for the observed ISC temperature dependence. In channel 1, ^1A_(2u) intersystem crosses directly into ^3A_(2u) using a high energy B–F or P–O vibration as accepting mode, resulting in a temperature-independent ISC rate. In channel 2, ISC occurs via a deactivating state of triplet character (which then rapidly decays to ^3A_(2u)), using Pt–Pt stretching (160 cm^(–1)) as a distorting mode to provide the energy needed. Fitting indicates that the deactivating state, ^3X, is moderately displaced (S = 0.5–3) and blue-shifted (ΔE = 1420–2550 cm^(–1)) from ^1A_(2u). Our model accounts for the experimental observation that ISC in both temperature independent and thermally activated channels is faster for Pt(pop) than for Pt(pop-BF_2): in the temperature independent channel because O–H modes in the former more effectively accept than B–F modes in the latter, and in the thermally activated pathway because the energy gap to ^3X is larger in the latter complex.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/71599,
title ="Metal-oxos in chemistry and biology",
author = "Gray, Harry B.",
pages = "SERMACS-128",
month = "October",
year = "2016",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20161031-080025729",
note = "© 2016 American Chemical Society.",
revision_no = "8",
abstract = "The dianionic oxo ligand occupies a very special place in coordination chem., owing to its ability to donate pi electrons to stabilize high oxidn. states of metals. My papers on the ligand field theory of multiple bonding in metal-oxos were published over 50 years ago in the first vol. of Inorg. Chem. The theory, which accounts for the optical and EPR spectroscopic properties of these complexes, also predicts that there must be an \"oxo wall\" between Fe-Ru-Os and Co-Rh-Ir in the periodic table. There have been many attempts to break down the wall, but it is still in pretty good shape!. I will review this early work, then discuss the roles metal-oxos play in two of the most important chem. reactions on planet Earth, hydrocarbon oxygenation catalyzed by cytochrome P 450, and solar-driven water oxidn. catalyzed by the Mn-Ca cluster of photosystem-II. Water splitting catalyzed by inorg. materials also is of great current interest. In this area, recent work in my lab has shown that high-valent iron-oxos likely are key intermediates in water oxidn. catalyzed by robust Fe,Ni-layered double hydroxides.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/72295,
title ="The Rise of Radicals in Bioinorganic Chemistry",
author = "Gray, Harry B. and Winkler, Jay R.",
journal = "Israel Journal of Chemistry",
volume = "56",
number = "9-10",
pages = "640-648",
month = "October",
year = "2016",
doi = "10.1002/ijch.201600069",
issn = "0021-2148",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20161128-084537050",
note = "© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. \n\nIssue online: 4 October 2016; Version of record online: 29 July 2016; Manuscript Received: 24 June 2016. \n\nThe research reported in this publication was supported by National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health under award number R01DK019038. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. Additional support was provided by the Arnold and Mabel Beckman Foundation.",
revision_no = "23",
abstract = "Prior to 1950, the consensus was that biological transformations occurred in two-electron steps, thereby avoiding the generation of free radicals. Dramatic advances in spectroscopy, biochemistry, and molecular biology have led to the realization that protein-based radicals participate in a vast array of vital biological mechanisms. Redox processes involving high-potential intermediates formed in reactions with O_2 are particularly susceptible to radical formation. Clusters of tyrosine (Tyr) and tryptophan (Trp) residues have been found in many O_2-reactive enzymes, raising the possibility that they play an antioxidant protective role. In blue copper proteins with plastocyanin-like domains, Tyr/Trp clusters are uncommon in the low-potential single-domain electron-transfer proteins and in the two-domain copper nitrite reductases. The two-domain muticopper oxidases, however, exhibit clusters of Tyr and Trp residues near the trinuclear copper active site where O_2 is reduced. These clusters may play a protective role to ensure that reactive oxygen species are not liberated during O_2 reduction.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/70272,
title ="Translational Science for Energy and Beyond",
author = "McKone, James R. and Crans, Debbie C.",
journal = "Inorganic Chemistry",
volume = "55",
number = "18",
pages = "9131-9143",
month = "September",
year = "2016",
doi = "10.1021/acs.inorgchem.6b01097",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160912-091156171",
note = "© 2016 American Chemical Society. \n\nReceived: May 5, 2016. Publication Date (Web): September 8, 2016. \n\nWe thank the American Chemical Society, Committee for Science, for sponsoring a session at the 249th ACS National Meeting in the Spring of 2015 highlighting the importance of translational research programs, where discussions leading to this manuscript began. We additionally acknowledge helpful input from Dr. Siddharth Dasgupta in the preparation of this manuscript. \n\nThe authors declare no competing financial interest.",
revision_no = "19",
abstract = "A clear challenge for the coming decades is decreasing the carbon intensity of the global energy supply while simultaneously accommodating a rapid worldwide increase in power demand. Meeting this challenge of providing abundant, clean energy undoubtedly requires synergistic efforts between basic and applied researchers in the chemical sciences to develop and deploy new technologies. Among the available options, solar energy is one of the promising targets because of the high abundance of solar photons over much of the globe. Similarly, decarbonization of the global energy supply will require clean sources of hydrogen to use as reducing equivalents for fuel and chemical feedstocks. In this report, we discuss the importance of translational research—defined as work that explicitly targets basic discovery as well as technology development—in the context of photovoltaics and solar fuels. We focus on three representative research programs encompassing translational research in government, industry, and academia. We then discuss more broadly the benefits and challenges of translational research models and offer recommendations for research programs that address societal challenges in the energy sector and beyond.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/70191,
title ="Electrocatalysis of CO_2 Reduction in Brush Polymer Ion Gels",
author = "McNicholas, Brendon J. and Blakemore, James D.",
journal = "Journal of the American Chemical Society",
volume = "138",
number = "35",
pages = "11160-11163",
month = "September",
year = "2016",
doi = "10.1021/jacs.6b08795",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160907-092755707",
note = "© 2016 American Chemical Society. \n\nReceived: August 23, 2016; Published: August 25, 2016. \n\nThis work was supported by the NSF CCI Solar Fuels Program (CHE-1305124). Additional support was provided by King Fahd University of Petroleum and Minerals. C.M.B. thanks the Dreyfus Foundation for Environmental Postdoc Fellowship EP-13-142. A.B.C. thanks the U.S. Department of Defense for support through the NDSEG Fellowship. \n\nThe authors declare no competing financial interest.",
revision_no = "13",
abstract = "The electrochemical characterization of brush polymer ion gels containing embedded small-molecule redox-active species is reported. Gels comprising PS–PEO–PS triblock brush polymer, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIm-TFSI), and some combination of ferrocene (Fc), cobaltocenium (CoCp_2^+), and Re(bpy)(CO)_3Cl (1) exhibit diffusion-controlled redox processes with diffusion coefficients approximately one-fifth of those observed in neat BMIm-TFSI. Notably, 1 dissolves homogeneously in the interpenetrating matrix domain of the ion gel and displays electrocatalytic CO_2 reduction to CO in the gel. The catalytic wave exhibits a positive shift versus Fc^(+/0) compared with analogous nonaqueous solvents with a reduction potential 450 mV positive of onset and 90% Faradaic efficiency for CO production. These materials provide a promising and alternative approach to immobilized electrocatalysis, creating numerous opportunities for application in solid-state devices.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/66596,
title ="Photoactivation of an Acid-Sensitive Ion Channel Associated with Vision and Pain",
author = "Shafaat, Oliver S. and Winkler, Jay R.",
journal = "ChemBioChem",
volume = "17",
number = "14",
pages = "1323-1327",
month = "July",
year = "2016",
doi = "10.1002/cbic.201600230",
issn = "1439-4227",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160502-142605593",
note = "© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. \n\nManuscript received: April 19, 2016; Accepted article published: April 28, 2016; Final article published: June 2, 2016. \n\nThe authors thank Jeffrey\u2005 J. Warren for helpful discussions. Professor Stefan Gründer generously provided the ASIC2a plasmid used in this work. Research reported in this publication was supported by the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health (NIH) under award number R01K019038 to H.B.G. and J.R.W. and by the W.\u2005M. Keck Foundation to D.A.D. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH. Additional support was provided by the Arnold and Mabel Beckman Foundation.",
revision_no = "34",
abstract = "We describe the reversible photoactivation of the acid sensitive ligand-gated ion channel ASIC2a, a mammalian channel found throughout the central and peripheral nervous systems that is associated with vision and pain. We also show the activation of GLIC, an acid-sensitive prokaryotic homologue of the nicotinic acetylcholine receptor. Photoactivation was achieved by using visible light irradiation of a newly synthesized water-soluble merocyanine photoacid, 1, which was designed to remove adverse channel blocking effects of a related system. Activation of ASIC2a and GLIC occurs reversibly, in a benign manner, and only upon irradiation. Further studies using transient absorption spectroscopy showed that protonation of a colorimetric base occurred rapidly (ca. 100\u2005μs) after excitation of 1. These results demonstrate that irradiation of 1 can induce rapid, local pH changes that can be used to investigate both biological and chemical proton transfer reactions.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/64631,
title ="Lanthanides: Applications in Cancer Diagnosis and Therapy",
author = "Teo, Ruijie D. and Termini, John",
journal = "Journal of Medicinal Chemistry",
volume = "59",
number = "13",
pages = "6012-6024",
month = "July",
year = "2016",
doi = "10.1021/acs.jmedchem.5b01975",
issn = "0022-2623",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160222-104525554",
note = "© 2016 American Chemical Society. \n\nReceived: December 21, 2015. Publication Date (Web): February 10, 2016. \n\nThis work was supported by the Caltech-City of Hope Biomedical Research Initiative (J.T. and H.B.G.) and the AACR Thomas J. Bardos Science Education Award (R.D.T.). Support from NIH Grant R01 DK019038 (H.B.G.) and NIH Grant R01 CA176611 (J.T.) also is acknowledged. \n\nThe authors declare no competing financial interest.",
revision_no = "14",
abstract = "Lanthanide complexes are of increasing importance in cancer diagnosis and therapy, owing to the versatile chemical and magnetic properties of the lanthanide-ion 4f electronic configuration. Following the first implementation of gadolinium(III)-based contrast agents in magnetic resonance imaging in the 1980s, lanthanide-based small molecules and nanomaterials have been investigated as cytotoxic agents and inhibitors, in photodynamic therapy, radiation therapy, drug/gene delivery, biosensing, and bioimaging. As the potential utility of lanthanides in these areas continues to increase, this timely review of current applications will be useful to medicinal chemists and other investigators interested in the latest developments and trends in this emerging field.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/67877,
title ="Visible-Light-Induced Olefin Activation Using 3D Aromatic Boron-Rich Cluster Photooxidants",
author = "Messina, Marco S. and Axtell, Jonathan C.",
journal = "Journal of the American Chemical Society",
volume = "138",
number = "22",
pages = "6952-6955",
month = "June",
year = "2016",
doi = "10.1021/jacs.6b03568",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160613-124225978",
note = "© 2016 American Chemical Society. \n\nReceived: April 6, 2016. Published: May 17, 2016. \n\nA.M.S. thanks the UCLA Department of Chemistry and Biochemistry for start-up funds and 3M for a Non-Tenured Faculty Award. M.S.M. thanks the NSF for the Bridge-to-Doctorate and the Predoctoral (GRFP) Fellowships. H.B.G. and O.S.S. acknowledge funding from the NIH (R01DK019038) and the Arnold and Mabel Beckman Foundation. A.N.A. thanks the NSF for CAREER Award CHE-1351968. Y.W. thanks the CSST Scholarship. H.D.M. thanks the NSF (CHE-1507735) for funding. B.M.U. thanks UCLA for a Dissertation Year Fellowship. The authors thank Mr. Daniel Hatfield (UCLA) for assistance with computational studies and Prof. Andrea Kasko (UCLA) for generously allowing access to her GPC instrument. \n\nAuthor Contributions: M.S.M. and J.C.A. contributed equally to the project. \n\nThe authors declare no competing financial interest.",
revision_no = "22",
abstract = "We report a discovery that perfunctionalized icosahedral dodecaborate clusters of the type B_(12)(OCH_2Ar)_(12) (Ar = Ph or C_6F_5) can undergo photo-excitation with visible light, leading to a new class of metal-free photooxidants. Excitation in these species occurs as a result of the charge transfer between low-lying orbitals located on the benzyl substituents and an unoccupied orbital delocalized throughout the boron cluster core. Here we show how these species, photo-excited with a benchtop blue LED source, can exhibit excited-state reduction potentials as high as 3 V and can participate in electron-transfer processes with a broad range of styrene monomers, initiating their polymerization. Initiation is observed in cases of both electron-rich and electron-deficient styrene monomers at cluster loadings as low as 0.005 mol%. Furthermore, photo-excitation of B_(12)(OCH_2C_6F_5)_(12) in the presence of a less activated olefin such as isobutylene results in the production of highly branched poly(isobutylene). This work introduces a new class of air-stable, metal-free photo-redox reagents capable of mediating chemical transformations.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/67333,
title ="Proton–hydride tautomerism in hydrogen evolution catalysis",
author = "Aguirre Quintana, Luis M. and Johnson, Samantha I.",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "113",
number = "23",
pages = "6409-6414",
month = "June",
year = "2016",
doi = "10.1073/pnas.1606018113 ",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160525-080847791",
note = "© 2016 National Academy of Sciences. \n\nContributed by Harry B. Gray, April 17, 2016 (sent for review February 4, 2016; reviewed by Alexander Miller and David Milstein). Published online before print May 24, 2016. \n\nS.I.J. thanks Dr. Robert Nielsen for helpful discussions. This research, which was carried out in part at the Molecular Materials Research Center and the Laser Resource Center of the Beckman Institute (California Institute of Technology), was supported by NSF CCI Solar Fuels Program CHE-1305124. S.I.J. and J.D.B. acknowledge fellowships from the Resnick Sustainability Institute at Caltech. \n\nAuthor contributions: S.I.J., D.G.V., J.R.W., H.B.G., and J.D.B. designed research; L.M.A.Q., S.I.J., S.L.C., W.V., M.K.T., and J.D.B. performed research; W.A.G. contributed new reagents/analytic tools; L.M.A.Q., S.I.J., S.L.C., W.V., M.K.T., D.G.V., J.R.W., H.B.G., and J.D.B. analyzed data; and S.I.J., J.R.W., H.B.G., and J.D.B. wrote the paper. \n\nReviewers: A.M., University of North Carolina; and D.M., The Weizmann Institute of Science. \n\nThe authors declare no conflict of interest. \n\nData deposition: The atomic coordinates and structure factors have been deposited in the Cambridge Crystallographic Data Centre (accession no. 1424707). \n\nThis article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1606018113/-/DCSupplemental.",
revision_no = "19",
abstract = "Efficient generation of hydrogen from renewable resources requires development of catalysts that avoid deep wells and high barriers. Information about the energy landscape for H_2 production can be obtained by chemical characterization of catalytic intermediates, but few have been observed to date. We have isolated and characterized a key intermediate in 2e^– + 2H^+ → H_2 catalysis. This intermediate, obtained by treatment of Cp*Rh(bpy) (Cp*, η^5-pentamethylcyclopentadienyl; bpy, κ^2-2,2′-bipyridyl) with acid, is not a hydride species but rather, bears [η^4-Cp*H] as a ligand. Delivery of a second proton to this species leads to evolution of H_2 and reformation of η^5-Cp* bound to rhodium(III). With suitable choices of acids and bases, the Cp*Rh(bpy) complex catalyzes facile and reversible interconversion of H^+ and H_2.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/66485,
title ="Reduced and Superreduced Diplatinum Complexes",
author = "Darnton, Tania V. and Hunter, Bryan M.",
journal = "Journal of the American Chemical Society",
volume = "138",
number = "17",
pages = "5699-5705",
month = "May",
year = "2016",
doi = "10.1021/jacs.6b02559",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160426-131418190",
note = "© 2016 American Chemical Society. \n\nReceived: March 9, 2016. Publication Date (Web): April 11, 2016. \n\nWe thank James Blakemore, Angelo Di Bilio, Yan-Choi Lam, and Jay R. Winkler for assistance with experiments and helpful discussions. This work was supported by the NSF CCI Solar Fuels Program (CHE-1305124). Additional support was provided by the Arnold and Mabel Beckman Foundation, the Ministry of Education of the Czech Republic (grants LH13015 and LD14129), and COST Actions CM1202 and CM1405. B.M.H. is a Fellow of the Resnick Sustainability Institute at Caltech; T.V.D. is an NSF Graduate Research Fellow. \n\nAuthor Contributions: T.V.D. and B.M.H. contributed equally. \n\nThe authors declare no competing financial interest.",
revision_no = "21",
abstract = "A d^8–d^8 complex [Pt_2(μ-P_2O_5(BF_2)_4]^(4–) (abbreviated Pt(pop-BF_2)^(4–)) undergoes two 1e– reductions at E_(1/2) = −1.68 and E_p = −2.46 V (vs Fc+/Fc) producing reduced Pt(pop-BF_2)^(5–) and superreduced Pt(pop-BF_2)^(6–) species, respectively. The EPR spectrum of Pt(pop-BF_2)^(5–) and UV–vis spectra of both the reduced and the superreduced complexes, together with TD-DFT calculations, reveal successive filling of the 6pσ orbital accompanied by gradual strengthening of Pt–Pt bonding interactions and, because of 6pσ delocalization, of Pt–P bonds in the course of the two reductions. Mayer–Millikan Pt–Pt bond orders of 0.173, 0.268, and 0.340 were calculated for the parent, reduced, and superreduced complexes, respectively. The second (5–/6−) reduction is accompanied by a structural distortion that is experimentally manifested by electrochemical irreversibility. Both reduction steps proceed without changing either d^8 Pt electronic configuration, making the superreduced Pt(pop-BF_2)^(6–) a very rare 6p^2 σ-bonded binuclear complex. However, the Pt–Pt σ bonding interaction is limited by the relatively long bridging-ligand-imposed Pt–Pt distance accompanied by repulsive electronic congestion. Pt(pop-BF_2)^(4–) is predicted to be a very strong photooxidant (potentials of +1.57 and +0.86 V are estimated for the singlet and triplet dσ*pσ excited states, respectively).",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/65876,
title ="Effect of interlayer anions on [NiFe]-LDH nanosheet water oxidation activity",
author = "Hunter, B. M. and Hieringer, W.",
journal = "Energy and Environmental Science",
volume = "2016",
number = "5",
pages = "1734-1743",
month = "May",
year = "2016",
doi = "10.1039/C6EE00377J",
issn = "1754-5692",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160404-081907582",
note = "© 2016 Royal Society of Chemistry. \n\nReceived 5th February 2016, Accepted 17th March 2016. First published online 17 Mar 2016. \n\nWe thank George Rossman for help with solid-state IR spectroscopy. Research was carried out in the Laser Resource Center and the Molecular Materials Research Center of the Beckman Institute of the California Institute of Technology. This work was supported by the NSF CCI Solar Fuels Program (CHE-1305124) and the Arnold and Mabel Beckman Foundation. B. M. H. is a Fellow of the Resnick Sustainability Institute at Caltech. W. H. thanks the Deutsche Forschungsgemeinschaft and the Cluster of Excellence \"Engineering of Advanced Materials\" at the University of Erlangen-Nürnberg for support.",
revision_no = "19",
abstract = "We synthesized nickel–iron layered double hydroxide ([NiFe]-LDH) nanosheets with different interlayer anions to probe their role in water oxidation catalysis. In alkaline electrolyte in ambient air, carbonate rapidly replaced other interlayer anions and catalytic activity was highest. Electrocatalytic water oxidation in virtually carbonate-free alkaline electrolyte revealed that activity was a function of anion basicity. Our [NiFe]-LDH nanosheets, prepared by pulsed laser ablation in liquids, were regenerated in carbonate-containing aqueous KOH. Anion binding motifs were assessed by X-ray photoelectron spectroscopy in combination with density functional theory calculations, suggesting that nitrite species bound to edge-site Fe in the precatalyst correlated with higher water oxidation activity.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/65919,
title ="Cellular uptake and anticancer activity of carboxylated gallium corroles",
author = "Pribisko, Melanie and Palmer, Joshua",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "113",
number = "16",
pages = "E2258-E2266",
month = "April",
year = "2016",
doi = "10.1073/pnas.1517402113",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160405-091631208",
note = "© 2016 National Academy of Sciences. \n\nContributed by Harry B. Gray, March 1, 2016 (sent for review September 1, 2015; reviewed by David Dolphin and Daniel T. Gryko). Published online before print April 4, 2016. \n\nThe experimental assistance of Dr. Shane Mangold and software assistance of Dr. Ching Ouyang are gratefully acknowledged. We thank Dr. Brian Armstrong of the Light Microscopy Digital Imaging Core Facility and Dr. Gerald Wuenschell of the Translational Biomarker Discovery Core Facility of the City of Hope Comprehensive Cancer Center for their technical assistance, and the NCI Developmental Therapeutics Program for the 60 cell line screen. This work was supported by a Caltech/COH grant (to J.T. and H.B.G.) and by NIH Grant DK01038 (to H.B.G.). \n\nuthor contributions: M.P., J.P., R.H.G., H.B.G., J.T., and P.L. designed research; M.P. and P.L. performed research; M.P. and P.L. contributed new reagents/analytic tools; M.P., J.T., and P.L. analyzed data; and M.P., J.P., R.H.G., H.B.G., J.T., and P.L. wrote the paper. \n\nReviewers: D.D., University of British Columbia; and D.T.G., Polish Academy of Sciences. \n\nThe authors declare no conflict of interest.",
revision_no = "17",
abstract = "We report derivatives of gallium(III) tris(pentafluorophenyl)corrole, 1 [Ga(tpfc)], with either sulfonic (2) or carboxylic acids (3, 4) as macrocyclic ring substituents: the aminocaproate derivative, 3 [Ga(ACtpfc)], demonstrated high cytotoxic activity against all NCI60 cell lines derived from nine tumor types and confirmed very high toxicity against melanoma cells, specifically the LOX IMVI and SK-MEL-28 cell lines. The toxicities of 1, 2, 3, and 4 [Ga(3-ctpfc)] toward prostate (DU-145), melanoma (SK-MEL-28), breast (MDA-MB-231), and ovarian (OVCAR-3) cancer cells revealed a dependence on the ring substituent: IC_(50) values ranged from 4.8 to >200 µM; and they correlated with the rates of uptake, extent of intracellular accumulation, and lipophilicity. Carboxylated corroles 3 and 4, which exhibited about 10-fold lower IC_(50) values (<20 µM) relative to previous analogs against all four cancer cell lines, displayed high efficacy (E_(max) = 0). Confocal fluorescence imaging revealed facile uptake of functionalized gallium corroles by all human cancer cells that followed the order: 4 >> 3 > 2 >> 1 (intracellular accumulation of gallium corroles was fastest in melanoma cells). We conclude that carboxylated gallium corroles are promising chemotherapeutics with the advantage that they also can be used for tumor imaging.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/65383,
title ="Computational Study of Fluorinated Diglyoxime-Iron Complexes: Tuning the Electrocatalytic Pathways for Hydrogen Evolution",
author = "Harshan, Aparna Karippara and Solis, Brian H.",
journal = "Inorganic Chemistry",
volume = "55",
number = "6",
pages = "2934-2940",
month = "March",
year = "2016",
doi = "10.1021/acs.inorgchem.5b02857",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160316-073650099",
note = "© 2016 American Chemical Society. \n\nReceived: December 9, 2015; Publication Date (Web): March 4, 2016. \n\nThis work was supported by the Center for Chemical Innovation of the National Science Foundation (Solar Fuels, Grant No. CHE-1305124). B.H.S. thanks the Alexander von Humboldt-Stiftung/Foundation for postdoctoral support during the writing of this paper. \n\nThe authors declare no competing financial interest.",
revision_no = "22",
abstract = "The ability to tune the properties of hydrogen-evolving molecular electrocatalysts is important for developing alternative energy sources. Fluorinated diglyoxime-iron complexes have been shown to evolve hydrogen at moderate overpotentials. Herein two such complexes, [(dAr^FgBF_2)_2Fe(py)_2], denoted A, and [(dAr^Fg_2H-BF_2)Fe(py)_2], denoted B [dAr^Fg = bis(pentafluorophenyl-glyoximato); py = pyridine], are investigated with density functional theory calculations. B differs from A in that one BF_2 bridge is replaced by a proton bridge of the form O–H–O. According to the calculations, the catalytic pathway for A involves two consecutive reduction steps, followed by protonation of an Fe^0 species to generate the active Fe^(II)-hydride species. B is found to proceed via two parallel pathways, where one pathway is similar to that for A, and the additional pathway arises from protonation of the O–H–O bridge, followed by spontaneous reduction to an Fe^0 intermediate and intramolecular proton transfer from the ligand to the metal center or protonation by external acid to form the same active Fe^(II)-hydride species. Simulated cyclic voltammograms (CVs) based on these mechanisms are in qualitative agreement with experimental CVs. The two parallel pathways identified for B arise from an equilibrium between the protonated and unprotonated ligand and result in two catalytic peaks in the CVs. The calculations predict that the relative probabilities for the two pathways, and therefore the relative magnitudes of the catalytic peaks, could be tuned by altering the pK_a of the acid or the substituents on the ligands of the electrocatalyst. The ability to control the catalytic pathways through acid strength or ligand substituents is critical for designing more effective catalysts for energy conversion processes.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/66114,
title ="DFT study of an unusual proton-relay role for Cp* in hydrogen evolution catalysis",
author = "Johnson, Samantha I. and Corona, Sydney L.",
pages = "INOR-759",
month = "March",
year = "2016",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160413-110622091",
note = "© 2016 American Chemical Society.",
revision_no = "13",
abstract = "Understanding mechanisms of the hydrogen evolution reaction (HER) is crucial to designing efficient catalysts for the prodn.\nof solar fuels. Cp*Rh(bpy) (Cp* = η^5- pentamethylcyclopentadienyl; bpy = κ^2-2,2'- bipyridyl) generates hydrogen in the\npresence of acid. However, the nature of the elementary steps leading to H-H formation has not been clear, as chem.\ncharacterization of intermediates in the catalytic reaction has been difficult to obtain. Here, we present a joint exptl.-\ncomputational study that addresses this challenge. D. functional theory (DFT) calcns. demonstrate that the catalyst first\nundergoes a 2e- redn. to form a Rh^I complex. Subsequently, in presence of acid, the Rh complex undergoes protonation at the\nCp* ligand to form a complex bearing an [η^4-Cp*H] ligand, preserving the RhI center. DFT calcns. show that this complex is\n6.8 kcal /mol more stable than the analogous Rh^(III) hydride. Following the formation of this intermediate, a second protonation\ncan be carried out which results in evolution of hydrogen and restoration of η^5-Cp*. To the best of our knowledge, these\nresults are among the first to show Cp* can serve as a proton relay in HER. New DFT results on the full mechanism for this\ncompd. will be presented, and predictions of possible improvements to the catalyst will be discussed in light of the newly\ncharacterized intermediate.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/66113,
title ="Effect of interlayer anions on [NiFe]-LDH nanosheet water oxidation activity",
author = "Hunter, Bryan M. and Winkler, Jay R.",
pages = "INOR-1132",
month = "March",
year = "2016",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160413-105235075",
note = "© 2016 American Chemical Society.",
revision_no = "12",
abstract = "Powering the planet with sustainable, carbon-neutral fuels affects every aspect of human life. Sunlight-driven water splitting is\nan attractive soln. to provide environmentally benign hydrogen fuel. Global scalability demands that all photoelectrode and\ncatalyst materials consist of earth- abundant elements. The water oxidn. half reaction requires four coupled electron and\nproton transfer steps, for which robust and efficient electrocatalysts are needed. We have shown previously that [NiFe] - layered double hydroxide (LDH) nanosheets are highly active water oxidn. catalysts [Hunter, Blakemore, Deimund, Gray,\nWinkler, Mueller, J. Am. Chem. Soc. 2014, 136, 13118]. They were synthesized by pulsed laser ablation in liqs. (PLAL), a\nmedium-throughput method that yields small, monodisperse, surfactant- free, size and compn. controlled nanomaterials\n[Blakemore, Gray, Winkler, Mueller, A. M. ACS Catal. 2013, 3, 2497]. Our [NiFe]-LDH nanosheets are among the best earthabundant\nwater oxidn. catalysts, reaching 10 mA cm^(-2) at only 280 mV overpotential on a flat electrode in 1 M aq. KOH. We\nhave now investigated the effect of interlayer anions on water oxidn. activity. Our [NiFe]-LDH materials consisted of\nsheets of edge- shared nickel oxide octahedra, with 22 % of ferric iron substituting at nickel sites. The excess pos. charges of\nFe^(3+) substituting for Ni^(2+) were balanced by interlayer anions; water was also present in the interlayer galleries. The small\nsize (<20 nm) of our nanosheets made by PLAL allowed for complete exchange of interlayer anions simply by soaking in aq.\nsolns. We synthesized twelve materials with different interlayer anions, either by anion exchange or directly by PLAL, and\nassessed their water oxidn. activity in strong aq. base. Const.- current electrolysis data showed that the basicity of\ninterlayer anions matters for water oxidn. catalysis. The catalysts were most active and self- healing in self-buffered\ncarbonate-contg. alk. electrolyte.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/66149,
title ="Electrochemical CO2 reduction catalyzed by Mn catalysts: DFT investigations point to strategies for overpotential reduction and activity improvement",
author = "Lam, Yan Choi and Nielsen, Robert J.",
pages = "CATL-198",
month = "March",
year = "2016",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160414-084344138",
note = "© 2016 American Chemical Society.",
revision_no = "11",
abstract = "Exptl., [(L) Mn(CO)_3]- (where L = bis alkyl- substituted bipyridine) has been obsd. to catalyze the electrochem. redn. of CO_2 to\nCO in the presence of trifluoroethanol (TFEH). Our DFT calcns. (B3LYP- d3 with continuum solvation) of the free energies of\nreaction and activation show that the highly exergonic hydrogen bonding between TFEH and TFE (homoconjugation) plays a\ncrit. role in reaction thermodn. and kinetics. The analgous 2,2'- bipyrimidine complex is predicted to have a lower (by ca. 0.5 V)\nonset overpotential, but at the expense of max. catalytic activity. As a strategy to improve catalytic activity and onset\noverpotential, a series of 2,2'- and 4,4'- bipyrimidines with tethered alc. or phenol was examd. The major predictions were that:\n(a) PhOH is not significantly more effective than TFEH at promoting dehydroxylation, due to their similar hydrogen bond\nacidities; (b) the appended phenols are less effective at promoting catalysis than the appended alc.; and (c) inclusion of one\nappended phenol arm promotes catalytic turnover by eliminating the entropic penalty of including an external PhOH in the\ndehydroxylation TS, but inclusion of two phenol arms is detrimental because intramol. hydrogen bonding stabilizes the resting\nstate of the catalytic cycle.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/65897,
title ="Electron flow through metalloproteins",
author = "Gray, Harry",
pages = "INOR-517",
month = "March",
year = "2016",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160404-132052605",
note = "© 2016 American Chemical Society.",
revision_no = "11",
abstract = "Understanding the underlying physics and chem. of biol. electron transfer processes is the goal of much of the work in my lab.\nEmploying laser flash-quench triggering methods, my coworkers and I have shown that long-range (1.5 to 2.5 nm) electron\ntunneling reactions in Ru-modified cytochromes and blue copper proteins occur on microsecond to nanosecond timescales.\nRedox equiv. can be transferred even longer distances by multistep tunneling (called hopping) through intervening tyrosines\nand tryptophans: notably, in our work on cytochrome P 450 and azurin, we have found that long-range hole hopping through\nintervening tryptophans can be orders of magnitude faster than single-step tunneling. Could hole hopping through Tyr/Trp\nchains protect redox enzymes from oxidative damage. Jay Winkler and I think so: by examg. the structures of P450s and many\nother oxygenases, we have identified conserved Tyr/Trp chains that could transfer holes rapidly from uncoupled high-potential\nintermediates to reductants in contact with protein surface sites.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/65961,
title ="Electronic structures and reactions of metal-oxos",
author = "Gray, Harry",
pages = "INOR-638",
month = "March",
year = "2016",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160406-095339421",
note = "© 2016 American Chemical Society.",
revision_no = "9",
abstract = "The dianionic oxo ligand occupies a very special place in coordination chem., owing to its ability to donate pi\nelectrons to stabilize high oxidn. states of metals. The ligand field theory of multiple bonding in metal-oxos,\nwhich was formulated over 50 years ago, predicts that there must be an \"oxo wall\" between Fe-Ru-Os and Co-\nRh-Ir in the periodic table. After reviewing early work, I will discuss the electronic structures of metal-oxo\ncomplexes that catalyze hydrocarbon oxygenation and water oxidn. reactions. In the latter area, work in my\nlab by Bryan Hunter and Astrid Mueller has shown that water oxidn. to dioxygen catalyzed by mixed-metal\nlayered double hydroxides likely involves high-valent Fe-oxo intermediates.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/65817,
title ="Fred Basolo and the (re)naissance of American inorganic chemistry",
author = "Labinger, Jay and Gray, Harry",
pages = "HIST-12",
month = "March",
year = "2016",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160331-155214201",
note = "© 2016 American Chemical Society.",
revision_no = "12",
abstract = "It was an Australian/British chemist, Sir Ronald Nyholm, who first spoke of a \"renaissance\" of inorg. chem.; but\nits emergence as a newly dynamic subfield, beginning in the 1950s, can be seen even more clearly in the US.\nWhile John Bailar is often credited as the \"Father of American Inorg. Chem.,\" it is arguable that Fred Basolo,\nBailar's student at Illinois, has had the most lasting impact on the dramatic growth of the field in American\nacademia. Our justification for that assertion will include comments and reminiscences from the students (one\nof them first-person!) he trained, as well as an examn. of his seminal contributions in the form of both original\nresearch and textbooks, particularly the groundbreaking 1958 work \"Mechanisms of Inorg. Reactions,\" written\nwith his Northwestern colleague Ralph Pearson, which played a central role in raising the intellectual stature of\ninorg. chem. by bringing the study of mechanism to the forefront.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/65849,
title ="In-situ spectroscopies of mixed-metal nanosheet water oxidation catalysts made by pulsed laser ablation in liquids",
author = "Hunter, Bryan and Winkler, Jay",
pages = "INOR-1134",
month = "March",
year = "2016",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160401-110652850",
note = "© 2016 American Chemical Society.",
revision_no = "11",
abstract = "Our ability to utilize sustainable resources will be crit. in meeting the ever-increasing global energy demand in\nan eco-friendly manner. The most reliable and available source of sustainable energy is the sun. The biggest\nchallenges to its practical utilization are its intermittency on earth and unequal local energy needs. As a\nconsequence, we must find a way to convert solar energy into storable, transportable fuels. We envision a solar\nwater splitting device that produces hydrogen fuel. Subsequent functionalization with carbon dioxide will\nproduce liq. fuels that are carbon neutral upon combustion. Water oxidn., the more demanding half-reaction in\nthe water splitting process, is a key component to such a working device. Earth-abundant, efficient, and robust\nwater oxidn. catalysts need to be rationally designed based on their catalytic mechanisms. We have employed\nnovel in-situ spectroelectrochem. techniques to identify short-lived catalytic intermediates under turnover\nconditions. We recently reported [NiFe]-LDH (layered double hydroxide) nanocatalyst materials that are highly\nactive for water oxidn. [Hunter, Blakemore, Deimund, Gray, Winkler, M.ovrddot.uller, J. Soc.2014, 136, 13118]\n. Our in-situ IR, Raman, and UV-visible spectroscopic data in non-aq. solvents suggest that the LDH framework\nmay support high-valent metal species. Strategic injection of substrate indicates that this transient species is\nquenched by water. Our isotope labeling expts. have shed light on the structure of catalytic intermediates.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/66650,
title ="Mechanistic investigation of proton reduction by cobaloximes: Insight from H2 oxidation kinetics",
author = "Del Ciello, Sarah A. and Winkler, Jay R.",
pages = "INOR-889",
month = "March",
year = "2016",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160504-105818808",
note = "© 2016 American Chemical Society.",
revision_no = "10",
abstract = "Cobaloximes are a class of earth- abundant proton redn. catalysts that have been known since the 1980's. Previous studies\nhave come to conflicting conclusions about the mechanism of proton redn. by these catalysts, with evidence existing for both a\nhomolytic and heterolytic mechanism. In this work, kinetic anal. of the reverse reaction is used to gain further insight.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/66395,
title ="Observation and reactivity studies of an unusual RhI intermediate in H2 evolution catalysis",
author = "Aguirre Quintana, Luis and Gray, Harry",
pages = "INOR-884",
month = "March",
year = "2016",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160422-084313796",
note = "© 2016 American Chemical Society.",
revision_no = "10",
abstract = "Understanding mechanisms of hydrogen evolution is important for improving catalysts that generate clean fuels. Catalysts\noften operate via unknown mechanism(s) due to the difficulty of observing or isolating key intermediates in the 2e-/2H+ redn.\nprocess. For our study, we prepd. a family of RhI complexes bearing the pentamethylcyclopentadienyl (η5-Cp*) ligand in\naddn. to derivs. of 4,4'- bipyridyl or 1,10- phenanthroline (bound in the κ2 mode). Under carefully chosen conditions, these\ncompds. formed intermediate species that suggest a previously unknown mechanism of H2 evolution involving protonhydride\ntautomerism driven by the Cp* ligand. This intermediate complex could be isolated in a MeCN soln., and even as a\nsolid, making it amenable to further mechanistic investigations. The intermediate species were analyzed by mass\nspectrometry, 1H NMR, and 2H NMR (NMR is NMR spectroscopy). Results will be discussed concerning the properties and\nreactivity of these active intermediates.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/64036,
title ="Proton-coupled electron hopping in Ru-modified P. aeruginosa azurin",
author = "Warren, Jeffrey J. and Shafaat, Oliver S.",
journal = "Journal of Biological Inorganic Chemistry",
volume = "21",
number = "1",
pages = "113-119",
month = "March",
year = "2016",
doi = "10.1007/s00775-016-1332-4",
issn = "0949-8257",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160127-160435518",
note = "© 2016 SBIC. \n\nReceived: 8 December 2015; Accepted: 4 January 2016. First online: 20 January 2016. \n\nTopical Issue in Honor of R.J.P. Williams. \n\nResearch reported in this publication was supported by The National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health under Award Number R01DK019038 to HBG and JRW. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. Additional support was provided by the Arnold and Mabel Beckman Foundation.",
revision_no = "24",
abstract = "We constructed two artificial multiple-step electron transfer (hopping) systems based on Pseudomonas aeruginosa azurin where a tyrosine (YOH) is situated between Ru(2,2′-bipyridine)_2(imidazole)(histidine) and the native copper site: RuH107YOH109 and RuH124-YOH122. We investigated the rates of Cu^I oxidation by flash-quench generated Ru^(III) over a range of conditions that probed the role of proton-coupled oxidation/reduction of YOH in the reaction. Rates of Cu^I oxidation were enhanced over single-step electron transfer by factors between 3 and 80, depending on specific scaffold and buffer conditions.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/66109,
title ="Proton-hydride tautomerism in hydrogen evolution catalysis",
author = "Blakemore, James D. and Aguirre Quintana, Luis M.",
pages = "INOR-1280",
month = "March",
year = "2016",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160413-095050455",
note = "© 2016 American Chemical Society.",
revision_no = "12",
abstract = "Efficient generation of hydrogen from renewable resources requires development of catalysts that avoid deep wells and high\nbarriers. Information about such features can be obtained by chem. characterization of catalytic intermediates, but few have\nbeen obsd. to date. Here, we have mapped the energy landscape of hydrogen evolution in a 2e- + 2H+ reaction sequence by\nchem. characterization of the intermediate formed upon initial protonation. This intermediate, obtained by treatment of Cp*Rh\n(bpy) (Cp* = η^5-pentamethylcyclcopentadienyl; bpy = κ^2- 2, 2'- bipyridyl) with acid, is not a hydride species but rather bears [η^4-Cp*H] as a ligand. The preserved Rh^I center can readily be protonated, leading to evolution of H_2 and reformation of η^4-Cp*\nbound to rhodium(III) . To the best of our knowledge, this is the first direct observation of a proton- relay role for the\nubiquitous Cp* ligand, which is revealed here to minimize energy barriers by enabling proton- hydride tautomerism. These\nlow barriers enable reversible catalysis; interconversion of H+ and H_2 can be achieved by minor variation of base concn. in the\nsystem. In this presentation, the energy landscape of the system will be discussed, including details from spectroscopic studies\nof the newly detected intermediate.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/67813,
title ="A corrole nanobiologic crosses the blood-brain-barrier and recognizes triple negative breast cancer: Implications for targeting brain metastases",
author = "Medina-Kauwe, L. and Sims, J.",
journal = "Cancer Research",
volume = "76",
number = "S4",
pages = "Art. No. P6-17",
month = "February",
year = "2016",
doi = "10.1158/1538-7445.SABCS15-P6-17-05",
issn = "0008-5472",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160610-085311876",
note = "© 2016 American Association for Cancer Research.",
revision_no = "10",
abstract = "Patients with breast cancer metastases to the brain on average survive less than one year. These tumors tend to be resistant to current therapies, and the majority of targeted therapeutics are unable to breach the blood brain barrier (BBB) to reach these tumors, thus improved alternatives are urgently needed.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/67810,
title ="Therapeutic efficacy of HER3-targeted nanobiologics on resistant tumors",
author = "Medina-Kauwe, L. and Sims, J.",
journal = "Cancer Research",
volume = "76",
number = "S4",
pages = "Art. No. P6-13",
month = "February",
year = "2016",
doi = "10.1158/1538-7445.SABCS15-P6-13-10",
issn = "0008-5472",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160610-081611441",
note = "© 2016 American Association for Cancer Research.",
revision_no = "9",
abstract = "Elevated cell surface levels of the human epidermal growth factor receptor subunit 3 (HER3) are associated with resistance to a number of signal-blocking breast cancer treatments, including inhibitors of EGF-R (lapatinib), HER2 (lapatinib, trastuzumab, T-DM1), HER2-3 (pertuzumab), and combination therapy. Additionally, HER3 elevation has been identified on \"untarget-able\" tumors such as triple-negative breast cancer (TNBC), including TNBC with acquired resistance to EGF-R inhibition. Patients with such refractory tumors currently have limited treatment options and a poor prognosis. Moreover, as up to 70% of cases resist or acquire resistance to signal-blocking therapies, an alternative approach addressing this important clinical problem has the potential for significant clinical impact. ",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/64635,
title ="Immobilization and electrochemical properties of ruthenium and iridium complexes on carbon electrodes",
author = "Gupta, Ayush and Blakemore, James D.",
journal = "Journal of Physics: Condensed Matter",
volume = "28",
number = "9",
pages = "Art. No. 094002",
month = "February",
year = "2016",
doi = "10.1088/0953-8984/28/9/094002",
issn = "0953-8984",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160222-122103336",
note = "© 2016 IOP Publishing Ltd. \n\nReceived 10 June 2015, revised 30 July 2015. Accepted for publication 11 August 2015. Published 12 February 2016. \n\nThis research was carried out in part at the Molecular materials Research Center of the Beckman Institute at Caltech. The research was supported by the Resnick Sustainability Institute at Caltech (Postdoctoral Fellowship to J D B) and the NSF CCI Solar Fuels Program (CHE-1305124 and a CCI Postdoctoral Fellowship to J D B). The x-ray photoelectron spectroscopy was supported by a contract with the California Energy Commission (500-11-023).",
revision_no = "11",
abstract = "We report the synthesis and surface immobilization of two new pyrene-appended molecular metal complexes: a ruthenium tris(bipyridyl) complex (1) and a bipyridyl complex of [Cp^*Ir] (2) (Cp^*\u2009\u2009=\u2009\u2009pentamethylcyclopentadienyl). X-ray photoelectron spectroscopy confirmed successful immobilization on high surface area carbon electrodes, with the expected elemental ratios for the desired compounds. Electrochemical data collected in acetonitrile solution revealed a reversible reduction of 1 near\u2009\u2009−1.4\u2009V, and reduction of 2 near\u2009\u2009−0.75\u2009V. The noncovalent immobilization, driven by association of the appended pyrene groups with the surface, was sufficiently stable to enable studies of the molecular electrochemistry. Electroactive surface coverage of 1 was diminished by only 27% over three hours soaking in electrolyte solution as measured by cyclic voltammetry. The electrochemical response of 2 resembled its soluble analogues, and suggested that ligand exchange occurred on the surface. Together, the results demonstrate that noncovalent immobilization routes are suitable for obtaining fundamental understanding of immobilized metal complexes and their reductive electrochemical properties.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/62508,
title ="Cytochrome unfolding pathways from computational analysis of crystal structures",
author = "Kozak, John J. and Gray, Harry B.",
journal = "Journal of Inorganic Biochemistry",
volume = "155",
pages = "44-55",
month = "February",
year = "2016",
doi = "10.1016/j.jinorgbio.2015.11.001",
issn = "0162-0134",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20151201-134904984",
note = "© 2016 Elsevier Inc. \n\nReceived 1 August 2015; Received in revised form 7 October 2015; Accepted 1 November 2015; Available online 10 November 2015. \n\nWe wish to acknowledge conversations with a number of colleagues who have provided valuable insights on both the strengths and limitations of the model presented here. Special thanks go to David Eisenberg, who suggested that the development would benefit from a graphical representation of selected results, and to J.R. Winkler. The authors would also like to thank one of the reviewers for drawing attention to one aspect of Ramachandran's (φ, ψ) plots. Financial support for R.A.G.-L. was provided by the Howard Hughes Medical Institute (grant # 52007555) Research Program from Pomona College. The authors would like to thank Pomona College undergraduates Sabari Kumar, Don Chen, Spencer Satz and Neil Chan for their help in developing the images for this paper. The molecular graphics images were produced using the Chimera package from the Computer Graphics Laboratory, University of California, San Francisco (supported by NIH P41 RR-01081). H.B. Gray thanks NIH (DK019038) and the Arnold and Mabel Beckman Foundation (BILRC) for support of the work. Research at the California Institute of Technology was supported by the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health under Award R01DK019038 (to H.B.G.).",
revision_no = "13",
abstract = "We have developed a model to study the role of geometrical factors in influencing the early stages of unfolding in three cytochromes: cyt c′, cyt c-b_(562) and cyt c. Each stage in unfolding is quantified by the spatial extension 〈λ_i〉 of n-residue segments, and by their angular extension 〈β_n〉. Similarities and differences between and among the three cytochromes in the unfolding of helical and non-helical regions can be determined by analyzing the data for each signature separately. Definite conclusions can be drawn when spatial and angular changes are considered in tandem. To facilitate comparisons, we present graphical portraits of the three cytochromes at the same stage of unfolding, and in relation to their native state structures. We also display specific segments at different stages of unfolding to illustrate differences in stability of defined domains thereby allowing us to make specific predictions on the unfolding of corresponding internal and terminal helices in cyt c′ and cyt c-b_(562). Our work accords with an earlier experimental report on the presence and persistence of a hydrophobic core in cyt c.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/60184,
title ="A corrole nanobiologic elicits tissue-activated MRI contrast enhancement and tumor-targeted toxicity",
author = "Sims, Jessica D. and Hwang, Jae Youn",
journal = "Journal of Controlled Release",
volume = "217",
pages = "92-101",
month = "November",
year = "2015",
doi = "10.1016/j.jconrel.2015.08.046",
issn = "0168-3659",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150911-091604421",
note = "© 2015 Elsevier B.V.\n\nReceived 23 April 2015; Received in revised form 10 August 2015; Accepted 24 August 2015; Available online 31 August 2015. \n\nThis research was supported by grants to LKMK from the NIH/NCI (R01 CA140995 and R01 CA129822), and from the National Center for Research Resources, Grant UL1RR033176, which is now at the National Center for Advancing Translational Sciences, Grant UL1TR000124. The authors are grateful to IC Atanasov, X Zhang, LS Lam, and H Zhou at the Electron Imaging Center for NanoMachines (EICN) within the California NanoSystems Institute (CNSI) at UCLA for EMservices and assistance; and acknowledge the use of instruments within the EICN supported by the NIH(1S10RR23057 to ZHZ) and CNSI at UCLA. The authors also thank X Da and W Tawackoli of the Cedars-Sinai Imaging Core for Xenogen imaging services provided for this study. Finally, we thank the University of Wisconsin–Madison Biochemistry MediaLab for use of mouse clipart. JDS thanks A Rozenek and JR Sims for their support and inspiration; and LKMK thanks C Rey, MM-Kauwe, and D Revetto for unwavering support and guidance. ZG thanks the Israel Science Foundation (Grant No. 274/13) for financial support of work performed at the Technion. IH, GK, KS, RAM thank the Radiology Research Endowment Fund and the Small Animal Imaging Core at the Saban Research Instititute.",
revision_no = "16",
abstract = "Water-soluble corroles with inherent fluorescence can form stable self-assemblies with tumor-targeted cell penetration proteins, and have been explored as agents for optical imaging and photosensitization of tumors in pre-clinical studies. However, the limited tissue-depth of excitation wavelengths limits their clinical applicability. To examine their utility in more clinically-relevant imaging and therapeutic modalities, here we have explored the use of corroles as contrast enhancing agents for magnetic resonance imaging (MRI), and evaluated their potential for tumor-selective delivery when encapsulated by a tumor-targeted polypeptide. We have found that a manganese-metallated corrole exhibits significant T1 relaxation shortening and MRI contrast enhancement that is blocked by particle formation in solution but yields considerable MRI contrast after tissue uptake. Cell entry but not low pH enables this. Additionally, the corrole elicited tumor-toxicity through the loss of mitochondrial membrane potential and cytoskeletal breakdown when delivered by the targeted polypeptide. The protein–corrole particle (which we call HerMn) exhibited improved therapeutic efficacy compared to current targeted therapies used in the clinic. Taken together with its tumor-preferential biodistribution, our findings indicate that HerMn can facilitate tumor-targeted toxicity after systemic delivery and tumor-selective MR imaging activatable by internalization.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/59443,
title ="Computational predictions of corroles as a class of Hsp90 inhibitors",
author = "Teo, Ruijie D. and Dong, Sijia S.",
journal = "Molecular BioSystems",
volume = "11",
number = "11",
pages = "2907-2914",
month = "November",
year = "2015",
doi = "10.1039/c5mb00352k",
issn = "1742-206X",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150812-101036401",
note = "© 2015 The Royal Society of Chemistry. \n\nReceived 22nd May 2015, Accepted 31st July 2015, First published online 31 July 2015. \n\nA Caltech/COH grant (H.B.G. and Z.G.) and the AACR-Thomas J. Bardos Science Education Award (R.D.T.) are gratefully acknowledged. SSD and WAG were supported partially by NIH (R01NS073115 and R01AI040567). We would also like to thank Y. C. Lam for helpful discussions.",
revision_no = "26",
abstract = "Corroles have been shown experimentally to cause cell cycle arrest, and there is some evidence that this might be attributed to an inhibitory effect of corroles on Heat shock protein 90 (Hsp90), which is known to play a vital role in cancer cell proliferation. In this study, we used molecular dynamics to examine the interaction of gallium corroles with Hsp90, and found that they can bind preferentially to the ATP-binding N-terminal site. We also found that structural variations of the corrole ring can influence the binding energies and affinities of the corrole to Hsp90. We predict that both the biscarboxylated corrole (4-Ga) and a proposed 3,17-bis-sulfonated corrole (7-Ga) are promising alternatives to Ga(III) 5,10,15-tris(pentafluorophenyl)-2,17-bis(sulfonic acid)-corrole (1-Ga) as anti-cancer agents.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/61975,
title ="Electron flow through biological molecules: does hole hopping protect proteins from oxidative damage?",
author = "Winkler, Jay R. and Gray, Harry B.",
journal = "Quarterly Reviews of Biophysics",
volume = "48",
number = "4",
pages = "411-420",
month = "November",
year = "2015",
doi = "10.1017/S0033583515000062",
issn = "0033-5835",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20151109-085816154",
note = "© 2015 Cambridge University Press 2015. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/3.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited. \n\nPublished online: 16 July 2015.\n\nWe thank Maraia Ener, Jeff Warren, Lionel Cheruzel, Kana Takematsu, and Oliver Shafaat for helpful discussions. \n\nResearch reported in this publication was supported by The National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health under award number R01DK019038 to HBG and JRW. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. Additional support was provided by the Arnold and Mabel Beckman Foundation.",
revision_no = "15",
abstract = "Biological electron transfers often occur between metal-containing cofactors that are separated by very large molecular distances. Employing photosensitizer-modified iron and copper proteins, we have shown that single-step electron tunneling can occur on nanosecond to microsecond timescales at distances between 15 and 20 Å. We also have shown that charge transport can occur over even longer distances by hole hopping (multistep tunneling) through intervening tyrosines and tryptophans. In this perspective, we advance the hypothesis that such hole hopping through Tyr/Trp chains could protect oxygenase, dioxygenase, and peroxidase enzymes from oxidative damage. In support of this view, by examining the structures of P450 (CYP102A) and 2OG-Fe (TauD) enzymes, we have identified candidate Tyr/Trp chains that could transfer holes from uncoupled high-potential intermediates to reductants in contact with protein surface sites.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/61730,
title ="Discovery of the magnetic behavior of hemoglobin: A beginning of bioinorganic chemistry",
author = "Bren, Kara L. and Eisenberg, Richard",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "112",
number = "43",
pages = "13123-13127",
month = "October",
year = "2015",
doi = "10.1073/pnas.1515704112 ",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20151030-074457750",
note = "© 2015 National Academy of Sciences.\n\nEdited by Michael A. Marletta, University of California, Berkeley, CA, and approved September 18, 2015 (received for review August 7, 2015).\n\nWe thank Jay R. Winkler for a critical reading of the manuscript and for several helpful suggestions. Research in biological inorganic chemistry at the California Institute of Technology is supported by the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health under Award R01DK019038 (to H.B.G. and J. R. Winkler) and at the University of Rochester is supported by National Science Foundation Award CHE-1409929 (to K.L.B.). \n\nAuthor contributions: K.L.B., R.E., and H.B.G. wrote the paper. \n\nThe authors declare no conflict of interest. \n\nThis article is a PNAS Direct Submission. \n\nThis article is part of the special series of PNAS 100th Anniversary articles to commemorate exceptional research published in PNAS over the last century. See the companion articles, “The magnetic properties and structure of the hemochromogens and related substances” on page 159 in issue 3 of volume 22, and “The magnetic properties and structure of hemoglobin, oxyhemoglobin and carbonmonoxyhemoglobin” on page 210 in issue 4 of volume 22.",
revision_no = "11",
abstract = "Two articles published by Pauling and Coryell in PNAS nearly 80 years ago described in detail the magnetic properties of oxy- and deoxyhemoglobin, as well as those of closely related compounds containing hemes. Their measurements revealed a large difference in magnetism between oxygenated and deoxygenated forms of the protein and, along with consideration of the observed diamagnetism of the carbonmonoxy derivative, led to an electronic structural formulation of oxyhemoglobin. The key role of hemoglobin as the main oxygen carrier in mammalian blood had been established earlier, and its allosteric behavior had been described in the 1920s. The Pauling–Coryell articles on hemoglobin represent truly seminal contributions to the field of bioinorganic chemistry because they are the first to make connections between active site electronic structure and the function of a metalloprotein.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/59572,
title ="Functional integration of Ni–Mo electrocatalysts with Si microwire array photocathodes to simultaneously achieve high fill factors and light-limited photocurrent densities for solar-driven hydrogen evolution",
author = "Shaner, Matthew R. and McKone, James R.",
journal = "Energy and Environmental Science",
volume = "8",
number = "10",
pages = "2977-2984",
month = "October",
year = "2015",
doi = "10.1039/C5EE01076D",
issn = "1754-5692",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150814-170845573",
note = "© Royal Society of Chemistry 2015.\n\nReceived 05 Apr 2015, Accepted 13 Jul 2015; First published online 07 Aug 2015. \n\nThis article is part of themed collection: Fundamentals and Applications of Inorganic Chemistry.\n\nDevice modeling, fabrication and testing were supported by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub supported through the Office of Science of the U.S. Department of Energy under award number DE-SC004993. Development of the Ni–Mo nanopowder catalyst was supported by the National Science Foundation (NSF) Powering the Planet Center for Chemical Innovation (CHE-1305124) and by the Molecular Materials Research Center of the Beckman Institute at the California Institute of Technology. The authors acknowledge additional support by the Gordon and Betty Moore Foundation (GBMF1225). MRS acknowledges the Resnick Sustainability Institute for a graduate fellowship. JRM acknowledges the Department of Energy, Office of Science, for a graduate research fellowship and the Department of Energy, Office of Energy Efficiency and Renewable Energy, for a SunShot postdoctoral research award.",
revision_no = "24",
abstract = "An n+p-Si microwire array coupled with a two-layer catalyst film consisting of Ni–Mo nanopowder and TiO_2 light-scattering nanoparticles has been used to simultaneously achieve high fill factors and light-limited photocurrent densities from photocathodes that produce H_2(g) directly from sunlight and water. The TiO_2 layer scattered light back into the Si microwire array, while optically obscuring the underlying Ni–Mo catalyst film. In turn, the Ni–Mo film had a mass loading sufficient to produce high catalytic activity, on a geometric area basis, for the hydrogen-evolution reaction. The best-performing microwire array devices prepared in this work exhibited short-circuit photocurrent densities of −14.3 mA cm^(−2), photovoltages of 420 mV, and a fill factor of 0.48 under 1 Sun of simulated solar illumination, whereas the equivalent planar Ni–Mo-coated Si device, without TiO_2 scatterers, exhibited negligible photocurrent due to complete light blocking by the Ni–Mo catalyst layer.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/59776,
title ="Electronic Excited States of Tungsten(0) Arylisocyanides",
author = "Kvapilová, Hana and Sattler, Wesley",
journal = "Inorganic Chemistry",
volume = "54",
number = "17",
pages = "8518-8528",
month = "September",
year = "2015",
doi = "10.1021/acs.inorgchem.5b01203",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150819-154731553",
note = "© 2015 American Chemical Society. ACS AuthorChoice - This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes. \n\nReceived: May 27, 2015. Publication Date (Web): August 12, 2015.\n\nThis work was supported by the STFC Rutherford Appleton Laboratory, Ministry of Education of the Czech Republic Grant LH13015 (program KONTAKT II), COST Action CM1202. Research at Caltech was supported by the NSF CCI Solar Fuels Program (CHE-1305124) and the Arnold and Mabel Beckman Foundation.",
revision_no = "25",
abstract = "W(CNAryl)_6 complexes containing 2,6-diisopropylphenyl isocyanide (CNdipp) are powerful photoreductants with strongly emissive long-lived excited states. These properties are enhanced upon appending another aryl ring, e.g., W(CNdippPh^(OMe)_2)_6; CNdippPh^(OMe)_2 = 4-(3,5-dimethoxyphenyl)-2,6-diisopropylphenylisocyanide (Sattler et al. J. Am. Chem. Soc. 2015, 137, 1198−1205). Electronic transitions and low-lying excited states of these complexes were investigated by time-dependent density functional theory (TDDFT); the lowest triplet state was characterized by time-resolved infrared spectroscopy (TRIR) supported by density functional theory (DFT). The intense absorption band of W(CNdipp)_6 at 460 nm and that of W(CNdippPh^(OMe)_2)_6 at 500 nm originate from transitions of mixed ππ*(C≡N–C)/MLCT(W → Aryl) character, whereby W is depopulated by ca. 0.4 e– and the electron-density changes are predominantly localized along two equatorial molecular axes. The red shift and intensity rise on going from W(CNdipp)_6 to W(CNdippPh^(OMe)_2)_6 are attributable to more extensive delocalization of the MLCT component. The complexes also exhibit absorptions in the 300–320 nm region, owing to W → C≡N MLCT transitions. Electronic absorptions in the spectrum of W(CNXy)_6 (Xy = 2,6-dimethylphenyl), a complex with orthogonal aryl orientation, have similar characteristics, although shifted to higher energies. The relaxed lowest W(CNAryl)_6 triplet state combines ππ* excitation of a trans pair of C≡N–C moieties with MLCT (0.21 e–) and ligand-to-ligand charge transfer (LLCT, 0.24–0.27 e–) from the other four CNAryl ligands to the axial aryl and, less, to C≡N groups; the spin density is localized along a single Aryl–N≡C–W–C≡N–Aryl axis. Delocalization of excited electron density on outer aryl rings in W(CNdippPh^(OMe)_2)_6 likely promotes photoinduced electron-transfer reactions to acceptor molecules. TRIR spectra show an intense broad bleach due to ν(C≡N), a prominent transient upshifted by 60–65 cm^(–1), and a weak down-shifted feature due to antisymmetric C≡N stretch along the axis of high spin density. The TRIR spectral pattern remains unchanged on the femtosecond-nanosecond time scale, indicating that intersystem crossing and electron-density localization are ultrafast (<100 fs).",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/58959,
title ="Hole hopping through tyrosine/tryptophan chains protects proteins from oxidative damage",
author = "Gray, Harry B. and Winkler, Jay R.",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "112",
number = "35",
pages = "10920-10925",
month = "September",
year = "2015",
doi = "10.1073/pnas.1512704112",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150721-094104240",
note = "© 2015 National Academy of Sciences.\n\nContributed by Harry B. Gray, June 29, 2015 (sent for review June 10, 2015; reviewed by David Beratan and Peter Brzezinski). Published online before print July 20, 2015.\n\nFor many years we enjoyed collaborative work with the late John H. (Jack) Richards; discussions with him influenced our current view of the roles of hole hopping in biology. Research reported in this publication was supported by The National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health under Award R01DK019038 (to H.B.G. and J.R.W.). Additional support was provided by the Arnold and Mabel Beckman Foundation. \n\nAuthor contributions: J.R.W. designed research; J.R.W. performed research; H.B.G. and J.R.W. analyzed data; and H.B.G. and J.R.W. wrote the paper. \n\nReviewers: D.B., Duke University; and P.B., Stockholm University. \n\nThe authors declare no conflict of interest. \n\nThis article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1512704112/-/DCSupplemental.",
revision_no = "21",
abstract = "Living organisms have adapted to atmospheric dioxygen by exploiting its oxidizing power while protecting themselves against toxic side effects. Reactive oxygen and nitrogen species formed during oxidative stress, as well as high-potential reactive intermediates formed during enzymatic catalysis, could rapidly and irreversibly damage polypeptides were protective mechanisms not available. Chains of redox-active tyrosine and tryptophan residues can transport potentially damaging oxidizing equivalents (holes) away from fragile active sites and toward protein surfaces where they can be scavenged by cellular reductants. Precise positioning of these chains is required to provide effective protection without inhibiting normal function. A search of the structural database reveals that about one third of all proteins contain Tyr/Trp chains composed of three or more residues. Although these chains are distributed among all enzyme classes, they appear with greatest frequency in the oxidoreductases and hydrolases. Consistent with a redox-protective role, approximately half of the dioxygen-using oxidoreductases have Tyr/Trp chain lengths ≥3 residues. Among the hydrolases, long Tyr/Trp chains appear almost exclusively in the glycoside hydrolases. These chains likely are important for substrate binding and positioning, but a secondary redox role also is a possibility.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/60316,
title ="H2 oxidation by cobaloximes: Mechanistic insight into hydrogen evolution catalysis",
author = "Del Ciello, Sarah A. and Winkler, Jay R.",
pages = "INOR-685",
month = "August",
year = "2015",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150918-085547603",
note = "© 2015 American Chemical Society.",
revision_no = "10",
abstract = "Cobaloximes are a series of macrocyclic cobalt complexes that have been shown to catalyze the hydrogen\nevolution reaction (HER) at low overpotentials. There has been much debate about the mechanism of this\nreaction, particularly with regard to H-H bond formation. As catalysts that operate close to the thermodn.\npotential, cobaloximes show some degree of reversibility, oxidizing hydrogen in the presence of base to form\nthe conjugate acid. Presented here are kinetic studies of the cobaloxime-mediated oxidn. of hydrogen in the\npresence of base. Insight into the bifurcation between homolytic and heterolytic mechanisms of cobaloximecatalyzed\nHER is gained by studying the microscopic reverse reaction.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/60331,
title ="Mixed-metal nanosheet water oxidation catalysts made by pulsed-laser ablation in liquids - Part 1: Synthesis, characterization, and electrocatalysis",
author = "Hunter, Bryan M. and Blakemore, James D.",
pages = "INOR-317",
month = "August",
year = "2015",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150918-134235578",
note = "© 2015 American Chemical Society.",
revision_no = "10",
abstract = "Global sustainable energy solns. remain one of the greatest challenges of the 21st century. Health and climate risks assocd. with\ncombustion of fossil fuels threaten global stability, development and national security. The sun is the most abundant and\ncleanest source of energy, but its intermittence on earth and unequal local energy needs require conversion into stored fuels.\nChem. can meet this challenge by solar-driven water splitting with earth-abundant, efficient and robust materials. Water\noxidn. is central to the prodn. of storable chem. fuels, since ample supply of cleanly, efficiently, and affordably generated\nprotons and electrons is a prerequisite for all sustainable chem. transformations. Pulsed-laser ablation in liqs. (PLAL) is a flexible\nsynthetic strategy to prep. earth-abundant, surfactant-free, mixed-metal (hydrous) oxide nanoparticle water oxidn.\ncatalysts [Blakemore, Gray, Winkler, Mueller, ACS Catal. 2013, 3, 2497]. It offers size and compn. control through multiple\ntuneable parameters (e.g. laser pulse energy and elemental content in the ablation target and liq.). With PLAL, many different\nnanocatalysts can readily be synthesized and screened for water oxidn. activity, rendering PLAL a medium-throughput method\nfor catalyst design. We prepd. a series of Ni-Fe materials and systematically varied Fe content. Oxygen evolution activity in\nbasic electrolyte increased as Fe content decreased to 22%. Addn. of Ti^(4+) and La^(3+) ions further enhanced electrocatalysis,\nreaching 10 mA cm^(-2) at 260 mV overpotential; on a flat working electrode, this is the lowest overpotential to date for Fe-Ni\ncatalysts. We spectroscopically identified [Ni-Fe]-layered double hydroxide nanosheets with intercalated nitrate and water,\n[Ni_(1-x)Fe_x(OH_2)](NO_3)_y(OH)_(x-y)•nH_2O, as the most active precatalyst. Higher turnover frequencies were obsd. with a\ngreater relative proportion of a 405.1 eV N 1s (XPS binding energy) species in the nanosheets [Hunter, Blakemore, Deimund,\nGray, Winkler, Mueller, J. Am. Chem. Soc. 2014, 136, 13118]. The effect of different intercalated anions on water oxidn.\nactivity was investigated.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/60330,
title ="Mixed-metal nanosheet water oxidation catalysts made by pulsed-laser ablation in liquids - Part 2: Mechanistic insights gained by novel in-situ spectroscopies",
author = "Hunter, Bryan M. and Gray, Harry B.",
pages = "INOR-322",
month = "August",
year = "2015",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150918-133442730",
note = "© 2015 American Chemical Society.",
revision_no = "12",
abstract = "Sustainable energy solns. impact every aspect of human life. National security, health, access to clean water, the extent of\nclimate change, and biodiversity all critically depend on the global availability of clean, affordable energy. The sun is our most\nabundant source of energy; more energy from sunlight strikes earth within a single hour than mankind consumes per yr. To\nsustainably power the planet, sunlight capture, charge transport, and catalysis are needed for fuel prodn. through water\nsplitting. Water oxidn. provides reducing equiv. through a complex four-electron transfer process. Sufficiently active, robust,\nearth-abundant catalysts for this important reaction are much needed yet still elusive; they will only be discovered through\nrational catalyst design guided by mechanistic insights into individual reaction steps. We recently reported highly efficient [NiFe]\n- layered double hydroxide water oxidn. nanocatalysts [Hunter, Blakemore, Deimund, Gray, Winkler, Mueller, J. 2014, 136,\n13118]. To gain mechanistic information, several in-situ electrochem. spectroscopies (i.e. IR, Raman, EPR, and x-ray absorption\nspectroscopies) have been developed, by which transient species during catalytic turnover were detected. We applied potentials\nto the catalyst nanosheets, at which in aq. electrolyte water oxidn. would occur, but instead we used non-aq. media to halt the\ncatalytic cycle; strategic injection of water led to turnover, and short-lived species could be identified. This way, we obtained\nexptl. evidence for intermediates required for efficient water oxidn.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/60027,
title ="Molecules, materials, and mechanisms for solar fuel production",
author = "Gray, Harry B.",
pages = "PRES-37",
month = "August",
year = "2015",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150902-104403641",
note = "© 2015 American Chemical Society.",
revision_no = "8",
abstract = "Collaborative research efforts in the NSF CCI Solar Fuels Program are focused on developing new fundamental\nunderstanding of mols. and materials that efficiently generate renewable hydrogen fuel using the energy of\nsunlight. Emphasis in these efforts is placed on a mechanistic understanding of reactions relevant to achieving\nfuel formation. Catalysis of water oxidn., the anodic half reaction of overall water splitting, is being intensely\nstudied. Pulsed laser ablation has proven to be a valuable technique for synthesis of small, surfactant-free,\nmixed-metal nanomaterials with size and compn. control. Deposition of these materials on electrodes results\nin assemblies that are highly active for water oxidn. In-situ spectroscopic studies of these assemblies are\nproviding new insights into possible mechanisms of oxygen evolution. In-situ spectroscopies are also being\napplied to investigate new trimetallic water-oxidn. catalysts. Metal oxides contg. Ni, Fe, and a third metal (M = Al, Ga, Mo, Cr) have been found to be superior in catalytic performance to the Ni-only or Ni-Fe analogs.\nUnderstanding the role of the third metal promises better understanding of the mechanism of catalysis in these\nmaterials. Exptl. cyclic voltammetry has demonstrated that fluorinated iron glyoxime complexes act as\nhydrogen evolving catalysts at modest overpotentials. Our objective is to use d. functional theory (DFT) calcns.\nand CV simulations to identify the mechanisms that are consistent with the obsd. activity. The calcd. redn.\npotentials and pKa's have allowed us to propose mechanisms for two catalyst derivs. In one case, the\nmechanism involves a single pathway through an Fe(0) intermediate and a subsequent Fe(II)-hydride\nintermediate. In a second case, a parallel pathway involving protonation of the ligand gives rise to a qual.\ndifferent electrochem. response. These mechanistic insights are guiding the synthesis of more active mol.\nelectrocatalysts.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/60034,
title ="Solar fuels",
author = "Gray, Harry B.",
pages = "PRES-2",
month = "August",
year = "2015",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150902-130713206",
note = "© 2015 American Chemical Society.",
revision_no = "10",
abstract = "Investigators in the NSF CCI Solar Fuels Program are working on syntheses of light absorbers and catalysts to be\ncomponents in devices for solardriven water splitting. Catalysts both for water oxidn. to dioxygen (OER) and prot\ndihydrogen (HER) have been fully characterized. Promising HER heterogeneous catalysts include Ni- Mo nanopowd\n(Ni, Co) phosphides, which reduce protons in acidic aq. solns. with catalytic efficiencies near that of platinum. PIs\nFuels also are investigating homogeneous iron, cobalt, and nickel complexes that catalyze H2 prodn. from protic\nrelatively low overpotentials. Both exptl. and theor. work has shed light on the mechanisms of these reactions. A\nnew photoanode materials, tantalum nitrides and dinitrogen- intercalated tungsten oxide are esp. promising. Also\ntheor. and exptl. study are bismuth vanadate photoanode- catalyst materials; and, in recent work, a promising me\nsynthesis of mixed- metal- oxide water oxidn. catalysts, pulsed laser ablation in liqs. (PLAL) , has been developed. S\nnanocryst. materials, including a highly active Ni, Fe, Ln, Ti- oxide nanosheet OER catalyst, have been obtained by P.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/60319,
title ="Two- photon absorption spectroscopy of inorganic compounds",
author = "Takematsu, Kana and Wehlin, Sara",
pages = "INOR-418",
month = "August",
year = "2015",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150918-103225666",
note = "© 2015 American Chemical Society.",
revision_no = "13",
abstract = "Two-photon absorption spectroscopy (TPAS) is a powerful spect\nelectronic structures of excited states that are not accessible under one-p\nTPAS in microscopy and photodynamic therapy are growing, as two- pho\npenetrate biol. tissues. While there is both a fundamental and prac\nproperties of dyes and other photoactive compds., lab. studies are cons\nand optics required to cover a broad tuning range. We demonstrate h\npumped OPO system can be utilized to obtain TPA spectra of inorg. comp\nobtained TPA spectra for the ruthenium(II) bipyridyl complex, Ru(bpy)_3^(2+)\nphotoreductants. We show that this methodol. can be further extended\nmetal carbonyl compds.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/59194,
title ="Electron-Transfer Reactions of Electronically Excited Zinc Tetraphenylporphyrin with Multinuclear Ruthenium Complexes",
author = "Henderson, Jane and Glover, Starla D.",
journal = "Journal of Physical Chemistry B",
volume = "119",
number = "24",
pages = "7473-7479",
month = "June",
year = "2015",
doi = "10.1021/jp511213p",
issn = "1520-6106",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150804-154353645",
note = "© 2014 American Chemical Society.\n\nReceived: November 9, 2014; Revised: December 11, 2014; Published: December 14, 2014. \n\nWe thank Jonas Petersson for his valuable collaboration. We also thank Professor Judy Kim for use of the Nd:YAG laser, Ignacio López-Peña for his spectroscopic support, and Dr. Brian Leigh for his continual enthusiasm. This work was supported by the National Science Foundation under Grants CHE-1145893 (C.P.K.) and CHE-1305124 (J.R.W., H.B.G.). \n\nThe authors declare no competing financial interest.",
revision_no = "14",
abstract = "Transient absorption decay rate constants (k_(obs)) for reactions of electronically excited zinc tetraphenylporphyrin (^3ZnTPP*) with triruthenium oxo-centered acetate-bridged clusters [Ru_3(μ_3-O)(μ-CH_3CO_2)_6(CO)(L)]_2(μ-pz), where pz = pyrazine and L = 4-cyanopyridine (cpy) (1), pyridine (py) (2), or 4-dimethylaminopyridine (dmap) (3), were obtained from nanosecond flash-quench spectroscopic data (quenching constants, k_q, for ^3ZnTPP*/1–3 are 3.0 × 10^9, 1.5 × 10^9, and 1.1 × 10^9 M^(–1) s^(–1), respectively). Values of k_q for reactions of ^3ZnTPP* with 1–3 and Ru_3(μ_3-O)(μ-CH_3CO_2)_6(CO)(L)_2 [L = cpy (4), py (5), dmap (6)] monomeric analogues suggest that photoinduced electron transfer is the main pathway of excited-state decay; this mechanistic proposal is consistent with results from a photolysis control experiment, where growth of characteristic near-IR absorption bands attributable to reduced (mixed-valence) Ru_3O-cluster products were observed.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/62097,
title ="Imaging Novel Ruthenium bipyridine-based Nanophotoswitches in Retina",
author = "Yue, Lan and Walston, Sean",
journal = "Investigative ophthalmology & visual science",
volume = "56",
number = "7",
pages = "1676-1676",
month = "June",
year = "2015",
issn = "0146-0404",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20151113-113545991",
note = "© 2015 by the Association for Research in Vision and Ophthalmology, Inc. \n\nNSF CBET-1404089; Research to Prevent Blindness; USC Eye Institute; Institute of Biomedical Therapeutics.",
revision_no = "18",
abstract = "Nanophotoswitches (NPSs) offer a new tool for optical\nstimulation of neuronal activity, in vitro and also potentially in vivo. Our group previously reported a ruthenium bipyridine (Rubpy)-based NPS that inserts into the plasma membrane and upon visible illumination generates an electrical dipole, triggering action potentials in adrenal chromaffin cells. We have recently demonstrated\nthat after intravitreal injection of this NPS into the eyes of blind rats, illumination of the eye elicited electrical activity in the contralateral superior colliculus. To better understand the site of action of the NPS in retina, we examined the distribution of the molecules in different\nretinal layers after intravitreal injection.\n\nMethods: Rubpy molecules can be visualized by their luminescence (610 nm) upon visible wavelength illumination (460 nm). To resolve the luminescence from different retinal layers, a rapid-scan twophoton imaging system (LaVison) was used (Ti:Sapphire laser tuned to 900 nm). Intravitreal injection (1 mM, 4 μL Rubpy-based NPSs\nin BSS), followed by eye removal and retina isolation 2-5 hrs after, was performed on young RCS rats. Luminescence images of the wholemount retina were captured by an EM-CCD camera (Andor). \n\nResults: At 2 hrs after intravitreal injection and with continuous superfusion of Ames medium, luminescence was confined near the injection site. Luminescence was observed localized to surface membranes of axons and somata of retinal ganglion cells (RGC), demonstrating the impermeability of the cell membrane to the NPS molecules. The outer retina did not show significant luminescence.\nAfter 3 additional hours, luminescence was more diffused within the RGC layer and still did not extend to the outer retina. \n\nConclusions: This study shows marked staining of RGC layer by intravitreally injected Rubpy-based NPS molecules, consistent with the hypothesis that the photoactivated NPS molecules induce electrical activity in the superior colliculus by acting on the RGCs that deliver electrical signals to the visual pathway outside the eyes. Distinct from other nano-scale optical cellular modulating approaches using optogenetics or azobenzene-based photoswitches, the NPS approach obviates the need for gene manipulation or toxic UV illumination, highlighting its potential in generating high-acuity prosthetic vision in patients blinded by retinal degenerative diseases.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/57042,
title ="Comparison of the Performance of CoP-Coated and Pt-Coated Radial Junction n^+p-Silicon Microwire-Array Photocathodes for the Sunlight-Driven Reduction of Water to H_2(g)",
author = "Roske, Christopher W. and Popczun, Eric J.",
journal = "Journal of Physical Chemistry Letters",
volume = "6",
number = "9",
pages = "1679-1683",
month = "May",
year = "2015",
doi = "10.1021/acs.jpclett.5b00495",
issn = "1948-7185",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150428-095042468",
note = "© 2015 American Chemical Society.\n\nReceived: March 9, 2015; Accepted: April 7, 2015; Publication Date (Web): April 20, 2015.\n\nThis work was supported by the NSF CCI Solar Fuels Program (CHE-1305124) and the Center for Individual Nanoparticle Functionality (CINF) (DNRF54). C.W.R. thanks the National Science Foundation and Link Energy Foundation for graduate research fellowships. Research was in part carried out at the Molecular Materials Research Center of the Beckman Institute of the California Institute of Technology. N.S.L. acknowledges support from the Energy from Sunlight Project funded by the Gordon and Betty Moore Foundation (GBMF1225).",
revision_no = "23",
abstract = "The electrocatalytic performance for hydrogen evolution has been evaluated for radial-junction n^+p-Si microwire (MW) arrays with Pt or cobalt phosphide, CoP, nanoparticulate catalysts in contact with 0.50 M H_2SO_4(aq). The CoP-coated (2.0 mg cm^(–2)) n^+p-Si MW photocathodes were stable for over 12 h of continuous operation and produced an open-circuit photovoltage (V_(oc)) of 0.48 V, a light-limited photocurrent density (J_(ph)) of 17 mA cm^(–2), a fill factor (ff) of 0.24, and an ideal regenerative cell efficiency (η_(IRC)) of 1.9% under simulated 1 Sun illumination. Pt-coated (0.5 mg cm^(–2)) n^+p-Si MW-array photocathodes produced V_(oc) = 0.44 V, J_(ph) = 14 mA cm^(–2), ff = 0.46, and η = 2.9% under identical conditions. Thus, the MW geometry allows the fabrication of photocathodes entirely comprised of earth-abundant materials that exhibit performance comparable to that of devices that contain Pt.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/55965,
title ="The Influence of Water on the Optical Properties of Single-Layer Molybdenum Disulfide",
author = "Varghese, Joseph O. and Agbo, Peter",
journal = "Advanced Materials",
volume = "27",
number = "17",
pages = "2734-2740",
month = "May",
year = "2015",
doi = "10.1002/adma.201500555",
issn = "0935-9648",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150323-101933830",
note = "© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.\n\nReceived: February 3, 2015; Revised: February 26, 2015. Article first published online: 18 Mar 2015.\n\nThe authors thank Dr. Jamil Tahir-Kheli for helpful discussions. The authors acknowledge grants from the Department of Energy (Grant No. DE-FG03-01ER46175: J.R.H.) and the National Science Foundation (Grant No. EAR-1322082: G.R.R.). Collection of PL spectra was supported in part by NSF CCI Solar Fuels grant (Grant No. CHE-1305124: H.B.G).",
revision_no = "24",
abstract = "Adsorbed molecules can significantly affect the properties of atomically thin materials. Physisorbed water plays a significant role in altering the optoelectronic properties of single-layer MoS_2, one such 2D film. Here we demonstrate the distinct quenching effect of adsorbed water on the photoluminescence of single-layer MoS_2 through scanning-probe and optical microscopies.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/56367,
title ="Control of Oligomerization and Oxidation Steps in the Synthesis of Tris(pentafluorophenyl)corrole",
author = "Blumenfeld, Carl and Fisher, Katherine J.",
journal = "European Journal of Organic Chemistry",
volume = "2015",
number = "14",
pages = "3022-3025",
month = "May",
year = "2015",
doi = "10.1002/ejoc.201500276",
issn = "1434-193X",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150406-084337401",
note = "© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim\n\nReceived: February 27, 2015. Article first published online: 1 Apr. 2015.\n\nThe authors acknowledge the Doheny Eye Institute, Sanofi, the Gordon and Betty Moore Foundation, Caltech, and the National Institutes of Health (NIH) (grant number RR027690) for financial and infrastructural support. The authors are grateful to Professor Zeev Gross for ongoing support in these efforts and suggestions on the presentation of this work. The authors also wish to thank Dr. David VanderVelde for assistance in obtaining NMR spectra of compounds 4-10 and Prof. Brian Stoltz for helpful discussions.",
revision_no = "23",
abstract = "The mechanistic features of oligomerization and oxidative cyclization steps in the synthesis of tris(pentafluorophenyl)corrole (1) have been thoroughly studied. Separation of the intermediates by preparative HPLC and analysis by NMR spectroscopy and high resolution mass spectrometry allowed for the identification of product-forming intermediates and monitoring of undesired byproducts. Conditions for complete end-capping with pyrrole were optimized for improved yields of oligomers leading to the desired corrole 1. A yield of 84\u2009% was achieved during oxidation of an isolated precursor; the overall yield of 1 was 17.0\u2009%.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/53059,
title ="Factors affecting bismuth vanadate photoelectrochemical performance",
author = "Sinclair, Timothy S. and Hunter, Bryan M.",
journal = "Materials Horizons",
volume = "2",
number = "3",
pages = "330-337",
month = "May",
year = "2015",
doi = "10.1039/c4mh00156g",
issn = "2051-6347",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20141222-075342492",
note = "© 2015 The Royal Society of Chemistry.\n\nReceived 22 Aug 2014, Accepted 02 Dec 2014, First published online 02 Dec 2014.\n\nWe thank June Wicks for help with SEM imaging, Matthew Shaner for providing electrodeposited BiVO_4 samples on FTO-glass prepared according to Choi, Richard P. Gerhart for fabrication of the photoelectrochemical cell, and Robert H. Coridan for valuable discussions. Research was performed at the Molecular Materials Research Center of the Beckman Institute of the California Institute of Technology. T.S.S. acknowledges a SURF Fellowship in honour of Dr Terry Cole, and B.M.H. is an NSF Graduate Fellow. This work was supported by the NSF CCI Solar Fuels Program (CHE-1305124) and the Arnold and Mabel Beckman Foundation.",
revision_no = "21",
abstract = "Bismuth vanadate is a promising photoanode material, but recent reports on undoped BiVO_4 without sublayers and co-catalysts showed large variations in photocurrent generation. We addressed this issue by correlating photoelectrochemical performance with physical properties. We devised a novel anodic electrodeposition procedure with iodide added to the aqueous plating bath, which allowed us to prepare BiVO_4 photoanodes with virtually identical thicknesses but different morphologies, and we could control surface Bi content. Morphologies were quantified from SEM images as distributions of crystallite areas and aspect-ratio-normalised diameters, and their statistical moments were derived. We could obtain clear photocurrent generation trends only from bivariate data analysis. Our experimental evidence suggests that a combination of low Bi/V ratio, small aspect-ratio-normalised diameters, and crystallites sizes that were small enough to provide efficient charge separation yet sufficiently large to prevent mass transport limitations led to highest photoelectrochemical performance.",
}
@book_section {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/69643,
title ="Multiple-Step Electron Flow in Proteins",
author = "Warren, Jeffrey J. and Ener, Maraia E.",
pages = "235-252",
month = "April",
year = "2015",
isbn = "9781439813188",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160816-081743396",
note = "© 2015 CRC Press.",
revision_no = "9",
abstract = "[No abstract]",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/57364,
title ="Spin−Orbit TDDFT Electronic Structure of Diplatinum(II,II) Complexes",
author = "Záliš, Stanislav and Lam, Yan-Choi",
journal = "Inorganic Chemistry",
volume = "54",
number = "7",
pages = "3491-3500",
month = "April",
year = "2015",
doi = "10.1021/acs.inorgchem.5b00063",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150508-082616550",
note = "© 2015 American Chemical Society. ACS AuthorChoice - This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes. \n\nReceived: January 9, 2015. Publication Date (Web): March 16, 2015. \n\nWe thank Mr. L. Henling (Beckman Institute) for his help with determining and presenting the X-ray structure. This work was supported by the Ministry of Education of the Czech Republic Grant No. LH13015 (Program KONTAKT II), the NSF CCI Solar Fuels Program (CHE-1305124), and the Arnold and Mabel Beckman Foundation.",
revision_no = "17",
abstract = "[Pt_2(μ-P_2O_5H_2)_4]^(4–) (Pt(pop)) and its perfluoroborated derivative [Pt_2(μ-P_2O_5(BF_2)_2)_4]^(4–) (Pt(pop-BF_2)) are d^8–d^8 complexes whose electronic excited states can drive reductions and oxidations of relatively inert substrates. We performed spin–orbit (SO) TDDFT calculations on these complexes that account for their absorption spectra across the entire UV–vis spectral region. The complexes exhibit both fluorescence and phosphorescence attributable, respectively, to singlet and triplet excited states of dσ*pσ origin. These features are energetically isolated from each other (∼7000 cm^(–1) for (Pt(pop-BF_2)) as well as from higher-lying states (5800 cm^(–1)). The lowest ^3dσ*pσ state is split into three SO states by interactions with higher-lying singlet states with dπpσ and, to a lesser extent, pπpσ contributions. The spectroscopically allowed dσ*pσ SO state has ∼96% singlet character with small admixtures of higher triplets of partial dπpσ and pπpσ characters that also mix with 3dσ*pσ, resulting in a second-order ^1dσ*pσ–^3dσ*pσ SO interaction that facilitates intersystem crossing (ISC). All SO interactions involving the dσ*pσ states are weak because of large energy gaps to higher interacting states. The spectroscopically allowed dσ*pσ SO state is followed by a dense manifold of ligand-to-metal–metal charge transfer states, some with pπpσ (at lower energies) or dπpσ contributions (at higher energies). Spectroscopically active higher states are strongly spin-mixed. The electronic structure, state ordering, and relative energies are minimally perturbed when the calculation is performed at the optimized geometries of the ^1dσ*pσ and ^3dσ*pσ excited states (rather than the ground state). Results obtained for Pt(pop) are very similar, showing slightly smaller energy gaps and, possibly, an additional ^1dσ*pσ – ^3dσ*pσ second order SO interaction involving higher ^1dπpσ* states that could account in part for the much faster ISC. It also appears that ^1dσ*pσ → ^3dσ*pσ ISC requires a structural distortion that has a lower barrier for Pt(pop) than for the more rigid Pt(pop-BF_2).",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/57781,
title ="An In Vitro Enzymatic Assay to Measure Transcription Inhibition by Gallium(III) and H_3 5,10,15-tris(pentafluorophenyl)corroles",
author = "Tang, Grace Y. and Pribisko, Melanie A.",
journal = "Journal of Visualized Experiments",
volume = "97",
pages = "Art. No. e52355",
month = "March",
year = "2015",
doi = "10.3791/52355",
issn = "1940-087X",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150522-124507826",
note = "© 2015 JoVE.\n\nDate Published: 3/18/2015.\n\nWe sincerely thank Dr. Cindy N. Chiu for help with gel electrophoresis, and Andy Zhou and Michael Grodick for their generous donation of DNA\nand restriction enzyme. We gratefully acknowledge Professor J. Heath and Professor D. Prober for generous access to equipment and materials.\nWe thank Dr. Karn Sorasaenee for helpful suggestions. We thank Mary H. Tang for creating the illustration used in the schematic overview in the\nvideo. Funding was provided by Johnson & Johnson and USC Y86786.",
revision_no = "11",
abstract = "Chemotherapy often involves broad-spectrum cytotoxic agents with many side effects and limited targeting. Corroles are a class of tetrapyrrolic\nmacrocycles that exhibit differential cytostatic and cytotoxic properties in specific cell lines, depending on the identities of the chelated metal and\nfunctional groups. The unique behavior of functionalized corroles towards specific cell lines introduces the possibility of targeted chemotherapy.\nMany anticancer drugs are evaluated by their ability to inhibit RNA transcription. Here we present a step-by-step protocol for RNA transcription in\nthe presence of known and potential inhibitors. The evaluation of the RNA products of the transcription reaction by gel electrophoresis and UVVis\nspectroscopy provides information on inhibitive properties of potential anticancer drug candidates and, with modifications to the assay, more\nabout their mechanism of action.\nLittle is known about the molecular mechanism of action of corrole cytotoxicity. In this experiment, we consider two corrole compounds:\ngallium(III) 5,10,15-(tris)pentafluorophenylcorrole (Ga(tpfc)) and freebase analogue 5,10,15-(tris)pentafluorophenylcorrole (tpfc). An RNA\ntranscription assay was used to examine the inhibitive properties of the corroles. Five transcription reactions were prepared: DNA treated with\nActinomycin D, triptolide, Ga(tpfc), tpfc at a [complex]:[template DNA base] ratio of 0.01, respectively, and an untreated control.\nThe transcription reactions were analyzed after 4 hr using agarose gel electrophoresis and UV-Vis spectroscopy. There is clear inhibition by\nGa(tpfc), Actinomycin D, and triptolide.\nThis RNA transcription assay can be modified to provide more mechanistic detail by varying the concentrations of the anticancer complex,\nDNA, or polymerase enzyme, or by incubating the DNA or polymerase with the complexes prior to RNA transcription; these modifications would\ndifferentiate between an inhibition mechanism involving the DNA or the enzyme. Adding the complex after RNA transcription can be used to test\nwhether the complexes degrade or hydrolyze the RNA. This assay can also be used to study additional anticancer candidates.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/54688,
title ="Could tyrosine and tryptophan serve multiple roles in biological redox processes?",
author = "Winkler, Jay R. and Gray, Harry B.",
journal = "Philosophical Transactions A: Mathematical, Physical and Engineering Sciences",
volume = "373",
number = "2037",
pages = "Art. No. 20140178",
month = "March",
year = "2015",
doi = "10.1098/rsta.2014.0178",
issn = "1364-503X",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150211-080309298",
note = "© 2015 The Author(s). Published by the Royal Society.\n\nPublished 9 February 2015.\n\nOur work on biological electron transfer processes is supported by the National Institutes of Health (DK-019038) and the Arnold and Mabel Beckman Foundation.",
revision_no = "11",
abstract = "Single-step electron tunnelling reactions can transport charges over distances of 15–20 Å in proteins. Longer-range transfer requires multi-step tunnelling processes along redox chains, often referred to as hopping. Long-range hopping via oxidized radicals of tryptophan and tyrosine, which has been identified in several natural enzymes, has been demonstrated in artificial constructs of the blue copper protein azurin. Tryptophan and tyrosine serve as hopping way stations in high-potential charge transport processes. It may be no coincidence that these two residues occur with greater-than-average frequency in O_2- and H_2O_2-reactive enzymes. We suggest that appropriately placed tyrosine and/or tryptophan residues prevent damage from high-potential reactive intermediates by reduction followed by transfer of the oxidizing equivalent to less harmful sites or out of the protein altogether.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/56636,
title ="Integrated catalyst-electrodes for the production of solar fuels",
author = "Blakemore, James D. and Gupta, Ayush",
journal = "Abstracts of Papers of the American Chemical Society",
volume = "249",
pages = "INOR-821",
month = "March",
year = "2015",
issn = "0065-7727",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150414-130714462",
note = "© 2015 American Chemical Society.",
revision_no = "13",
abstract = "Immobilization of selective catalysts for fuel- forming reactions on (photo) electrode surfaces is an appealing route to structures\nfor the generation of renewable fuel. Our recent work has focused on immobilization of mol. catalysts on graphitic carbon\nelectrode surfaces via noncovalent interactions. The general approach relies on a pyrene- appended bipyridyl ligand (P) that\nserves as the linker between the catalysts and the surface. With this method, proton redn. to dihydrogen was catalyzed with an\nimmobilized rhodium complex, [Cp*Rh(P) Cl] Cl, and CO_2 redn. to CO was catalyzed with a rhenium complex, Re(P) (CO)_3Cl.\nSpectroscopic studies of the [Cp*Rh] - and [Re(CO)_3] - functionalized electrodes are providing new insights into the activity of\nthese assemblies. Catalysis continues over the timescale of hours, and in the case of hydrogen evolution, with estd. turnover\nfrequency near 1 per s. We are also now extending work to earth- abundant systems, and have prepd. Mn(P) (CO)_3Br as a\ncandidate CO_2 - redn. catalyst. Immobilization results in electroactive material, and electrocatalytic CO prodn. has been\nmeasured. Recent results will be presented, including spectroscopic characterization, electrochem. stability, and electrocatalytic\nCO_2 redn. with these catalysts.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/56921,
title ="Reconstitution and in-vitro activation of the prokaryotic pentameric ligand-gated ion channel ELIC",
author = "Shafaat, Oliver S. and Rusinova, Radda",
journal = "Abstracts of Papers of the American Chemical Society",
volume = "249",
pages = "BIOL-246",
month = "March",
year = "2015",
issn = "0065-7727",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150423-131529413",
note = "© 2015 American Chemical Society.",
revision_no = "11",
abstract = "Pentameric ligand- gated ion channels are a large class of ion channels that aid in signal transduction between cells.\nEukaryotic members of this family include the cation- selective nicotinic acetylcholine receptor (nAChR) and the anion- selective\nγ- aminobutyric acid (GABA) receptor. Signal transduction and activation follow two processes: first, ligand binds to the\nchannel; and second, a conformational change occurs that leads to channel opening. The ligand binding interactions have\nbeen elucidated in numerous studies. However, the subsequent conformational changes that lead to channel opening remain\nelusive. Recently, prokaryotic members of this ion channel family were isolated, and high- resoln. structures obtained. An\nactivation mechanism was proposed based on the assignment of these structures to putative 'open' and 'closed' states.\nActivation, however, is dynamic; initiated with ligand binding, and followed by conformational changes that result in pore\nopening and ion flux through the channel. The sequence of steps that connect the initial ligand binding to channel opening\nremain poorly understood. Our goal is to explore these steps using dynamic exptl. techniques. Continuous- flow ultrafast (μs)\nmixing permits delivery of ligand to channels reconstituted into lipid vesicles of defined compn. Combined with time- resolved\nenergy transfer, this approach allows for high- resoln. monitoring of the dynamics of activation. To that end, the prokaryotic\nligand- gated ion channel ELIC has been reconstituted into large unilamellar lipid vesicles and activation was monitored\nusing a stopped- flow fluorescence- quench assay. Activation characteristics of the reconstituted ELIC, and developments\ntoward monitoring the early activation steps in the ultrafast mixer, will be discussed.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/56873,
title ="Will solar- driven water splitting devices see the light of day?",
author = "Gray, Harry B.",
journal = "Abstracts of Papers of the American Chemical Society",
volume = "249",
pages = "COMSCI-1",
month = "March",
year = "2015",
issn = "0065-7727",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150422-105112123",
note = "© 2015 American Chemical Society.",
revision_no = "8",
abstract = "Several promising technologies have been developed in recent years for the generation of hydrogen from solar- driven water\nsplitting. I will highlight areas where breakthroughs will be needed if we are to realize global- scale prodn. of this and other\nclean solar fuels.",
}
@book_section {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/85788,
title ="Electrochemical Activation of Cytochrome P450",
author = "Udit, Andrew K. and Hill, Michael G.",
pages = "133-167",
month = "February",
year = "2015",
doi = "10.1002/9781118899076.ch7",
isbn = "9780470578452",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180412-130552536",
note = "© 2015 John Wiley & Sons, Inc. \n\nPublished Online: 29 May 2015; Published Print: 26 February 2015.",
revision_no = "8",
abstract = "This chapter reviews the efforts to develop catalytically competent P450 systems in which a simple electrode replaces NAD(P)H, and in some instances native reductase proteins, in the catalytic cycle. Notably, in evaluating the successes of P450 electrocatalytic methods, there is an important distinction to be made between mammalian and bacterial systems. While some mention of notable mammalian P450 electrocatalytic systems is made, the chapter focuses primarily on bacterial systems and specifically on the NADPH dependent flavocytochrome P450 from Bacillus megaterium (BM3). Harnessing P450 activity for in vitro applications may be most simply accomplished with electrochemical systems utilizing soluble mediators. Protein–surfactant film voltammetry has been widely used for studying the redox chemistry of P450s. Another striking aspect of P450 electrochemistry in surfactant films is the dramatic shift of the Fe^(III/II) couple to positive potentials. Finally, mediated electrochemical P450 systems are perhaps the best bets for large‐scale biocatalysis.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/55975,
title ="A Mn Bipyrimidine Catalyst Predicted To Reduce CO_2 at Lower Overpotential",
author = "Lam, Yan Choi and Nielsen, Robert J.",
journal = "ACS Catalysis",
volume = "5",
number = "4",
pages = "2521-2528",
month = "February",
year = "2015",
doi = "10.1021/cs501963v",
issn = "2155-5435",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150323-132108582",
note = "© 2015 American Chemical Society.\n\nReceived: September 18, 2014; Revised: February 12, 2015. Publication Date (Web): February 16, 2015.\n\nY.C.L., who performed the calculations and data analysis, was supported by the National Science Foundation (NSF) through the Centers for Chemical Innovation (CCI), Solar Fuels grant CHE-1305124, as was H.B.G. R.J.N. and W.A.G., who developed the computational strategy, interpretation, and analysis studies, are supported by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under Award Number DE-SC0004993. We gratefully acknowledge Professor Clifford P. Kubiak for helpful discussions.",
revision_no = "14",
abstract = "Experimentally, [(L)Mn(CO)_3]− (where L = bis-alkyl-substituted bipyridine) has been observed to catalyze the electrochemical reduction of CO_2 to CO in the presence of trifluoroethanol (TFEH). Here we report the atomistic level mechanism of complete catalytic cycles for this reaction, on the basis of DFT calculations (B3LYP-D3 with continuum solvation) of the free energies of reaction and activation, as well as reduction potentials for all catalytically relevant elementary steps. The highly exergonic homoconjugation and carbonation of TFE– play critical roles in reaction thermodynamics and kinetics, the overall half-reaction being 3CO_2 + 2TFEH + 2e– → CO + H_2O + 2[F_3CCH_2OCO_2]− (calculated standard reduction potential: −1.49 V vs SCE). In the catalytic cycle for CO formation, CO_2 coordinates to [(L)Mn(CO)_3]− (1a, L = bpy), and the adduct is then protonated to form [(L)Mn(CO)_3(CO_2H)] (3a). 3a subsequently reacts to form [(L)Mn(CO)_4]0 (5a) via one of two pathways: (a) TFEH-mediated dehydroxylation to [(L)Mn(CO)_4]+ (4a), followed by one-electron reduction to 5a, or (b) under more reducing potentials, one-electron reduction to [(L)Mn(CO)_3(CO_2H)]− (3′a), followed by dehydroxylation to 5a. Pathway b has a lower activation energy by 2.2 kcal mol^(–1). Consequently, the maximum catalytic turnover frequency (TOF_(max)) is achieved at ∼−1.75 V vs SCE (∼0.25 V overpotential). For the analogous bipyrimidine compound (not yet studied experimentally), reduction of 3b to 3′b occurs at a potential 0.5 V more positive than that of 3a, and the overpotential required to achieve TOF_(max) is predicted to be lower by ∼0.25 V. This improvement is, however, achieved at the price of a lower TOF_(max), and we predict that 1b has superior TOF at potentials above ∼−1.6 V vs SCE. In addition, the various factors contributing to product selectivity (CO over H_2) are discussed.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/54064,
title ="Bespoke Photoreductants: Tungsten Arylisocyanides",
author = "Sattler, Wesley and Henling, Lawrence M.",
journal = "Journal of the American Chemical Society",
volume = "137",
number = "3",
pages = "1198-1205",
month = "January",
year = "2015",
doi = "10.1021/ja510973h",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150126-093535146",
note = "© 2015 American Chemical Society. \n\nReceived October 24, 2014. Publication Date (Web): January 16, 2015. \n\nWe thank Michael Takase and David VanderVelde for assistance with X-ray and NMR experiments. Discussions with Aaron Rachford, Paul LaBeaume, Jim Thackeray, and Jim Cameron in the early stages of this work were very helpful. The Bruker KAPPA APEX II X-ray diffractometer was purchased via an NSF CRIF:MU award to the California Institute of Technology (CHE-0639094). Our work is supported by the National Science Foundation Center for Chemical Innovation in Solar Fuels (CHE-1305124) and a CCI postdoctoral fellowship to W.S.",
revision_no = "29",
abstract = "Modular syntheses of oligoarylisocyanide ligands that are derivatives of 2,6-diisopropylphenyl isocyanide (CNdipp) have been developed; tungsten complexes incorporating these oligoarylisocyanide ligands exhibit intense metal-to-ligand charge-transfer visible absorptions that are red-shifted and more intense than those of the parent W(CNdipp)_6 complex. Additionally, these W(CNAr)_6 complexes have enhanced excited-state properties, including longer lifetimes and very high quantum yields. The decay kinetics of electronically excited W(CNAr)_6 complexes (*W(CNAr)_6) show solvent dependences; faster decay is observed in higher dielectric solvents. *W(CNAr)_6 lifetimes are temperature dependent, suggestive of a strong coupling nonradiative decay mechanism that promotes repopulation of the ground state. Notably, *W(CNAr)_6 complexes are exceptionally strong reductants: [W(CNAr)_6]+/*W(CNAr)_6 potentials are more negative than −2.7 V vs [Cp_2Fe]^+/Cp_2Fe.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/52221,
title ="Catalysis of Proton Reduction by a [BO_4]-Bridged Dicobalt Glyoxime",
author = "Laga, Stephanie M. and Blakemore, James D.",
journal = "Inorganic Chemistry",
volume = "53",
number = "24",
pages = "12668-12670",
month = "December",
year = "2014",
doi = "10.1021/ic501804h",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20141201-105741726",
note = "© 2014 American Chemical Society.\n\nReceived: July 28, 2014; published: November 19, 2014.\n\nThe authors thank Ivonne Ferrer for helpful discussions and\nAaron Sattler for assistance in preparation of Figure 2. This research was carried out in part at the Molecular Materials Research Center of the Beckman Institute at Caltech. The research was supported by the Resnick Sustainability Institute at Caltech (Postdoctoral Fellowship to J.D.B.) and the NSF CCI Solar Fuels Program (CHE-1305124 and a CCI Postdoctoral Fellowship to J.D.B.). The Bruker KAPPA APEXII X-ray diffractometer was purchased via an NSF CRIF:MU award to the California Institute of Technology (CHE-0639094). Gas chromatographs were collected at the Joint Center for Artificial Photosynthesis at Caltech.",
revision_no = "28",
abstract = "We report the preparation of a dicobalt compound with two singly proton-bridged cobaloxime units linked by a central [BO_4] bridge. Reaction of a doubly proton-bridged cobaloxime complex with trimethyl borate afforded the compound in good yield. Single-crystal X-ray diffraction studies confirmed the bridging nature of the [BO_4] moiety. Using electrochemical methods, the dicobalt complex was found to be an electrocatalyst for proton reduction in acetonitrile solution. Notably, the overpotential for proton reduction (954 mV) was found to be higher than in the cases of two analogous single-site cobalt glyoximes under virtually identical conditions.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/53768,
title ="Pentamethylcyclopentadienyl rhodium complexes",
author = "Blakemore, James D. and Hernandez, Emilia S.",
journal = "Polyhedron",
volume = "84",
pages = "14-18",
month = "December",
year = "2014",
doi = "10.1016/j.poly.2014.05.022 ",
issn = "0277-5387",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150115-100257213",
note = "© 2014 Elsevier Ltd. \n\nReceived 3 April 2014; Accepted 8 May 2014; Available online 20 May 2014. \n\nThe authors thank Aaron Sattler and Nathan Schley for helpful discussions. This research was carried out in part at the Molecular Materials Research Center of the Beckman Institute at Caltech. This work was supported by the NSF CCI Solar Fuels Program (CHE-1305124) and CCI Postdoctoral Fellowships to JDB and WS. The Bruker KAPPA APEXII X-ray diffractometer was purchased via an NSF CRIF:MU award to the California Institute of Technology (CHE-0639094).",
revision_no = "24",
abstract = "We report syntheses and structures of pentamethylcyclopentadienyl (Cp∗) rhodium(III) and rhodium(I) complexes. Dicationic rhodium(III) complexes, [Cp∗Rh(bpy)(MeCN)](PF_6)_2 and [Cp∗Rh(vbpy)(MeCN)](PF_6)_2 (bpy = 2,2′-bipyridyl and vbpy = 4-vinyl-2,2′-bipyridyl), were prepared by treatment of [Cp∗Rh(MeCN)_3](PF_6)_2 with bpy and vbpy, respectively. The monocationic rhodium(III) complex, [Cp∗Rh(Me_4phen)Cl]Cl (Me_4phen = 3,4,7,8-tetramethyl-1,10-phenanthroline), was prepared by treatment of the chloride-bridged rhodium dimer, [Cp∗RhCl_2]_2, with Me_4phen. Two rhodium(I) complexes were synthesized via reduction of their rhodium(III) counterparts using two different methods: Cp∗Rh(bpy) was produced via a new route involving treatment of [Cp∗Rh(bpy)Cl]Cl with thallium formate in dry acetonitrile, whereas [Cp∗Rh(Me_4phen)Cl]Cl was reduced with Na(Hg) to give Cp∗Rh(Me_4phen). The colors of the Rh(I) complexes are attributable to relatively intense visible-region MLCT absorptions.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/50070,
title ="A cytotoxic and cytostatic gold(III) corrole",
author = "Teo, Ruijie D. and Gray, Harry B.",
journal = "Chemical Communications",
volume = "50",
number = "89",
pages = "13789-13792",
month = "November",
year = "2014",
doi = "10.1039/c4cc06577h",
issn = "1359-7345",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140926-131926805",
note = "© 2014 The Royal Society of Chemistry.\n\nReceived 21st August 2014,\nAccepted 4th September 2014,\nFirst published online 05 Sep 2014.\n\nWe thank Roger E. Moore of the Mass Spectrometry and\nProteomics Core (City of Hope) for technical assistance. Our\nwork is supported by the Caltech-City of Hope Biomedical\nResearch Initiative (H.B.G., J.T., Z.G.) and the Caltech Summer Undergraduate Research Fellowship program (D.R.T.).",
revision_no = "15",
abstract = "We have synthesized and characterized a water-soluble gold(III) corrole (1-Au) that is highly toxic to cisplatin-resistant cancer cells. Relative to its 1-Ga analogue, axial ligands bind only weakly to 1-Au, which likely accounts for its lower affinity for human serum albumin (HSA). We suggest that the cytotoxicity of 1-Au may be related to this lower HSA affinity.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/47541,
title ="Cellular uptake and cytotoxicity of a near-IR fluorescent corrole–TiO_2 nanoconjugate",
author = "Blumenfeld, Carl M. and Sadtler, Bryce F.",
journal = "Journal of Inorganic Biochemistry",
volume = "140",
pages = "39-44",
month = "November",
year = "2014",
doi = "10.1016/j.jinorgbio.2014.06.015",
issn = "0162-0134",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140729-072109271",
note = "© 2014 Elsevier Inc. \n\nReceived 13 March 2014, Revised 19 June 2014, Accepted 20 June 2014, Available online 28 June 2014. \n\nWe thank the CHLA Radiology Endowment Fund (K.S.), Sanofi (H.B.G.), Doheny Eye Institute (R.H.G.), and Beckman Institute Postdoctoral Fellowship (B.F.S.) for the support. We also thank Anahit Hovsepyan, Seda Mkhitaryan, Vazgen Khankaldyyan, and Gevorg Karapetyan for the help with the bioluminescence assays. Absorption measurements and profilometry were performed at the Molecular Materials Research Center, Beckman Institute, Caltech. We thank\nCarol M. Garland for the assistance in TEM imaging. B.F.S. and N.S.L. acknowledge the support from the “Light–Material Interactions in Energy Conversion” Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences (DE-SC0001293).",
revision_no = "23",
abstract = "We are investigating the biological and biomedical imaging roles and impacts of fluorescent metallocorrole–TiO_2 nanoconjugates as potential near-infrared optical contrast agents in vitro in cancer and normal cell lines. The TiO_2 nanoconjugate labeled with the small molecule 2,17-bis(chlorosulfonyl)-5,10,15-tris(pentafluorophenyl)corrolato aluminum(III) (1-Al–TiO_2) was prepared. The nanoparticle 1-Al–TiO_2 was characterized by transmission electron microscopy (TEM) and integrating-sphere electronic absorption spectroscopy. TEM images of three different samples of TiO_2 nanoparticles (bare, H_2O_2 etched, and 1-Al functionalized) showed similarity in shapes and sizes with an average diameter of 29 nm for 1-Al–TiO_2. Loading of 1-Al on the TiO_2 surfaces was determined to be ca. 20–40 mg 1-Al/g TiO_2. Confocal fluorescence microscopy (CFM) studies of luciferase-transfected primary human glioblastoma U87-Luc cells treated with the nanoconjugate 1-Al–TiO_2 as the contrast agent in various concentrations were performed. The CFM images revealed that 1-Al–TiO_2 was found inside the cancer cells even at low doses (0.02–2 μg/mL) and localized in the cytosol. Bioluminescence studies of the U87-Luc cells exposed to various amounts of 1-Al–TiO_2 showed minimal cytotoxic effects even at higher doses (2–2000 μg/mL) after 24 h. A similar observation was made using primary mouse hepatocytes (PMH) treated with 1-Al–TiO_2 at low doses (0.0003–3 μg/mL). Longer incubation times (after 48 and 72 h for U87-Luc) and higher doses (> 20 μg/mL 1-Al–TiO_2 for U87-Luc and > 3 μg/mL 1-Al–TiO_2 for PMH) showed decreased cell viability.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/47359,
title ="Assembly, characterization, and electrochemical properties of immobilized metal bipyridyl complexes on silicon(111) surface",
author = "Lattimer, Judith R. C. and Blakemore, James D.",
journal = "Dalton Transactions",
volume = "43",
number = "40",
pages = "15004-15012",
month = "October",
year = "2014",
doi = "10.1039/c4dt01149j",
issn = "1477-9226",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140721-090909176",
note = "© 2014 Royal Society of Chemistry. \n\nAdvance Article. Received 18th April 2014; Accepted 9th July 2014. First published online 17 Jul 2014. \n\nThe authors thank Aaron Sattler for helpful discussions. Research was carried out in part at the Molecular Materials Research Center of the Beckman Institute at the California Institute of Technology. This work was supported by the NSF CCI Solar Fuels Program (CHE-1305124) and CCI Postdoctoral Fellowships to JDB and WS. The synchrotron facility was provided by the Stanford Synchrotron Radiation Laboratory (SSRL) at beam line 7-3. The SSRL Biomedical Technology program is supported by the National Institute of Health (NIH), the National Center for Research Resources, and the DOE Office of Biological and Environmental Research. XAS work was funded by the Director, Office of Science, Office of Basic Energy Sciences (OBES), Division of Chemical Sciences, Geosciences, and Biosciences of the Department of Energy (DOE) under Contract DE-AC02-05CH11231.",
revision_no = "24",
abstract = "Silicon(111) surfaces have been functionalized with mixed monolayers consisting of submonolayer coverages of immobilized 4-vinyl-2,2′-bipyridyl (1, vbpy) moieties, with the remaining atop sites of the silicon surface passivated by methyl groups. As the immobilized bipyridyl ligands bind transition metal ions, metal complexes can be assembled on the silicon surface. X-ray photoelectron spectroscopy (XPS) demonstrates that bipyridyl complexes of [Cp*Rh], [Cp*Ir], and [Ru(acac)2] were formed on the surface (Cp* is pentamethylcyclopentadienyl, acac is acetylacetonate). For the surface prepared with Ir, X-ray absorption spectroscopy at the Ir LIII edge showed an edge energy as well as post-edge features that were essentially identical with those observed on a powder sample of [Cp*Ir(bpy)Cl]Cl (bpy is 2,2′-bipyridyl). Charge-carrier lifetime measurements confirmed that the silicon surfaces retain their highly favorable photoelectronic properties upon assembly of the metal complexes. Electrochemical data for surfaces prepared on highly doped, n-type Si(111) electrodes showed that the assembled molecular complexes were redox active. However the stability of the molecular complexes on the surfaces was limited to several cycles of voltammetry.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/51546,
title ="Theoretical Modeling of Low-Energy Electronic Absorption\nBands in Reduced Cobaloximes",
author = "Bhattacharjee, Anirban and Chavarot-Kerlidou, Murielle",
journal = "ChemPhysChem",
volume = "15",
number = "14",
pages = "2951-2958",
month = "October",
year = "2014",
doi = "10.1002/cphc.201402398",
issn = "1439-4235",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20141111-082813986",
note = "© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Article first published online: 11 Aug 2014. Manuscript Revised: 8 Jul 2014. Manuscript Received: 4 Jun 2014. \n\nFinancial support from the French National Research Agency\n(NiFe-Cat, ANR-10-BLAN-7-11 and LABEX ARCANE, ANR-11-LABX-\n0D03-01), the FP7 CEA-Eurotalent COFUND Programme, the CEA’s\nDSV-ENERGIE 2011 Programme, the European Research Council\nunder the European Union’s Seventh Framework Programme (FP/\n2007-2013)/ERC Grant Agreement no. 306398, the NSF Center for Chemical Innovation (CCI Solar, CHE-1305124), the U.S. Department of Energy (DOE) under contract number DE-AC02-\n98CH10886, and the Brazilian FAPESP (project 12/02501-4) is\ngratefully acknowledged.",
revision_no = "18",
abstract = "The reduced Co^I states of cobaloximes are powerful nucleophiles that play an important role in the hydrogen-evolving catalytic activity of these species. In this work we analyze the low-energy electronic absorption bands of two cobaloxime systems experimentally and use a variety of density functional theory and molecular orbital ab initio quantum chemical approaches. Overall we find a reasonable qualitative understanding of the electronic excitation spectra of these compounds but show that obtaining quantitative results remains a challenging task.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/50053,
title ="Modeling Dioxygen Reduction at Multicopper Oxidase Cathodes",
author = "Agbo, Peter and Heath, James R.",
journal = "Journal of the American Chemical Society",
volume = "136",
number = "39",
pages = "13882-13887",
month = "October",
year = "2014",
doi = "10.1021/ja5077519",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140926-091054210",
note = "© 2014 American Chemical Society. \n\nReceived: July 29, 2014. \n\nPublication Date (Web): September 4, 2014. \n\nWe thank Fan Liu, Joseph Varghese, and Jay Winkler for helpful discussions and the Beckman Institute Molecular Materials Research Center for access to equipment. This research was funded by the NSF CCI Solar Fuels Program (CHE-1305124) and a Perkins Grant (JRH.PERKINS3-1-GRANT.PERKINS3). \n\nThe authors declare no competing financial interest.",
revision_no = "25",
abstract = "We report a general kinetics model for catalytic dioxygen reduction on multicopper oxidase (MCO) cathodes. Our rate equation combines Butler–Volmer (BV) electrode kinetics and the Michaelis–Menten (MM) formalism for enzymatic catalysis, with the BV model accounting for interfacial electron transfer (ET) between the electrode surface and the MCO type 1 copper site. Extending the principles of MM kinetics to this system produced an analytical expression incorporating the effects of subsequent intramolecular ET and dioxygen binding to the trinuclear copper cluster into the cumulative model. We employed experimental electrochemical data on Thermus thermophilus laccase as benchmarks to validate our model, which we suggest will aid in the design of more efficient MCO cathodes. In addition, we demonstrate the model’s utility in determining estimates for both the electronic coupling and average distance between the laccase type-1 active site and the cathode substrate.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/49692,
title ="Stabilization of n-cadmium telluride photoanodes for water oxidation to O_2(g) in aqueous alkaline electrolytes using amorphous TiO_2 films formed by atomic-layer deposition",
author = "Lichterman, Michael F. and Carim, Azhar I.",
journal = "Energy and Environmental Science",
volume = "7",
number = "10",
pages = "3334-3337",
month = "October",
year = "2014",
doi = "10.1039/C4EE01914H ",
issn = "1754-5692",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140915-092918358",
note = "© 2014 Royal Society of Chemistry. \n\nReceived 20th June 2014; accepted 21st August 2014. First published online 22 Aug 2014. \n\nThis material is based upon work performed by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U. S. Department of Energy under Award Number DE-SC0004993. The authors gratefully acknowledge Dr Ke Sun for insightful discussions and Dr Slobodan Mitrovic for assistance collecting XPS data. AIC is grateful to the National Science Foundation for support from an NSF Graduate Research Fellowship. BSB and HBG acknowledge\nthe Beckman Institute Materials and Laser Resource Centers\nand NSF CHE-1305124 for support.",
revision_no = "25",
abstract = "Although II–VI semiconductors such as CdS, CdTe, CdSe, ZnTe, and alloys thereof can have nearly ideal band gaps and band-edge positions for the production of solar fuels, II–VI photoanodes are well-known to be unstable towards photocorrosion or photopassivation when in contact with aqueous electrolytes. Atomic-layer deposition (ALD) of amorphous, “leaky” TiO_2 films coated with thin films or islands of Ni oxide has been shown to robustly protect Si, GaAs, and other III–V materials from photocorrosion and therefore to facilitate the robust, solar-driven photoelectrochemical oxidation of H_2O to O_2(g). We demonstrate herein that ALD-deposited 140 nm thick amorphous TiO_2 films also effectively protect single crystalline n-CdTe photoanodes from corrosion or passivation. An n-CdTe/TiO_2 electrode with a thin overlayer of a Ni-oxide based oxygen-evolution electrocatalyst produced 435 ± 15 mV of photovoltage with a light-limited current density of 21 ± 1 mA cm^−2 under 100 mW cm^−2 of simulated Air Mass 1.5 illumination. The ALD-deposited TiO_2 films are highly optically transparent and electrically conductive. We show that an n-CdTe/TiO_2/Ni oxide electrode enables the stable solar-driven oxidation of H_2O to O_2(g) in strongly alkaline aqueous solutions, where passive, intrinsically safe, efficient systems for solar-driven water splitting can be operated.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/51051,
title ="Symmetry-Breaking Charge Transfer of Visible Light Absorbing Systems: Zinc Dipyrrins",
author = "Trinh, Cong and Kirlikovali, Kent",
journal = "Journal of Physical Chemistry C",
volume = "118",
number = "38",
pages = "21834-21845",
month = "September",
year = "2014",
doi = "10.1021/jp506855t",
issn = "1932-7447",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20141030-092012977",
note = "© 2014 American Chemical Society. ACS AuthorChoice - This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes. \n\nReceived: July 9, 2014; Revised: August 27, 2014; Published: August 27, 2014.\n\nWe thank Dr. Ralf Haiges for the help with crystallographic\nstudies and Dr. Sean Roberts for helpful discussion regarding the TA data. We acknowledge financial support from following organizations: the synthesis and characterization of zinc dipyrrins were supported by the Nanoflex Power Corp.; Xray crystallography was performed on a Bruker APEX II CCD system, acquired with funds provided by the NSF CRIF program (Award 1048807); some of the NMR spectra were recorded on a Varian 400-MR spectrometer, acquired with funds provided by the NSF CRIF program (Award 0840366); ns-to-ms TA experiments were performed at the Beckman Institute Laser Resource Center at Caltech; M.E.E. was supported by NIH Grant RO1-DK019038; ultrafast (fs-to-ns) TA studies were supported by the Center for Energy Nanoscience (CEN) at USC. CEN is an Energy Frontier\nResearch Center funded by the U.S. Department of Energy,\nOffice of Science, Office of Basic Energy Sciences (DESC0001013).",
revision_no = "20",
abstract = "Zinc dipyrrin complexes with two identical dipyrrin ligands absorb strongly at 450–550 nm and exhibit high fluorescence quantum yields in nonpolar solvents (e.g., 0.16–0.66 in cyclohexane) and weak to nonexistent emission in polar solvents (i.e., <10^(–3), in acetonitrile). The low quantum efficiencies in polar solvents are attributed to the formation of a nonemissive symmetry-breaking charge transfer (SBCT) state, which is not formed in nonpolar solvents. Analysis using ultrafast spectroscopy shows that in polar solvents the singlet excited state relaxes to the SBCT state in 1.0–5.5 ps and then decays via recombination to the triplet or ground states in 0.9–3.3 ns. In the weakly polar solvent toluene, the equilibrium between a localized excited state and the charge transfer state is established in 11–22 ps.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/50808,
title ="Highly Active Mixed-Metal Nanosheet Water Oxidation Catalysts Made by Pulsed-Laser Ablation in Liquids",
author = "Hunter, Bryan M. and Blakemore, James D.",
journal = "Journal of the American Chemical Society",
volume = "136",
number = "8",
pages = "13118-13121",
month = "September",
year = "2014",
doi = "10.1021/ja506087h",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20141024-143748867",
note = "© 2014 American Chemical Society. Received: June 17, 2014.\nPublished: September 8, 2014. Publication Date (Web): September 8, 2014. \n\nWe thank Richard Gerhart for fabrication of an electrochemical\ncell, Alasdair McDowall for help with TEM, and George Rossman for help with solid-state Raman and IR spectroscopies.\nResearch was carried out in the Laser Resource Center and the Molecular Materials Research Center of the Beckman Institute of the California Institute of Technology. This work was supported by the NSF CCI Solar Fuels Program (CHE-1305124) and the Arnold and Mabel Beckman Foundation. ",
revision_no = "16",
abstract = "Surfactant-free mixed-metal hydroxide water oxidation nanocatalysts were synthesized by pulsed-laser ablation in liquids. In a series of [Ni-Fe]-layered double hydroxides with intercalated nitrate and water, [Ni_(1–x)Fe_x(OH)_2](NO_3)_y(OH)_(x−y)·nH_2O, higher activity was observed as the amount of Fe decreased to 22%. Addition of Ti^(4+) and La^(3+) ions further enhanced electrocatalysis, with a lowest overpotential of 260 mV at 10 mA cm^(–2). Electrocatalytic water oxidation activity increased with the relative proportion of a 405.1 eV N 1s (XPS binding energy) species in the nanosheets.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/50051,
title ="Fluorescence Quenching of (Dimethylamino)naphthalene Dyes\nBadan and Prodan by Tryptophan in Cytochromes P450 and Micelles",
author = "Pospíšil, Petr and Luxem, Katja E.",
journal = "Journal of Physical Chemistry B",
volume = "118",
number = "34",
pages = "10085-10091",
month = "August",
year = "2014",
doi = "10.1021/jp504625d",
issn = "1520-6106",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140926-090835212",
note = "© 2014 American Chemical Society. ACS AuthorChoice - This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes. \n\nReceived: May 11, 2014; Revised: July 7, 2014; Published: July 31, 2014.\n\nThis research was supported by the Grant Agency of the Czech\nRepublic (P106/12/G016) and the Ministry of Education of\nthe Czech Republic program Kontakt II (grant LH13015).\nM.H. acknowledges financial support by ASCR via the\nPraemium Academiae award. Work at Caltech was supported\nby NIH grant DK019038 to H.B.G. and a Summer Undergraduate\nResearch Fellowship (SURF) to K.E.L.",
revision_no = "19",
abstract = "Fluorescence of 2-(N,N-dimethylamino)-6-propionylnaphthalene dyes Badan and Prodan is quenched by tryptophan in Brij 58 micelles as well as in two cytochrome P450 proteins (CYP102, CYP119) with Badan covalently attached to a cysteine residue. Formation of nonemissive complexes between a dye molecule and tryptophan accounts for about 76% of the fluorescence intensity quenching in micelles, the rest is due to diffusive encounters. In the absence of tryptophan, fluorescence of Badan-labeled cytochromes decays with triexponential kinetics characterized by lifetimes of about 100 ps, 700–800 ps, and 3 ns. Site mutation of a histidine residue in the vicinity of the Badan label by tryptophan results in shortening of all three decay lifetimes. The relative amplitude of the fastest component increases at the expense of the two slower ones. The average quenching rate constants are 4.5 × 10^8 s^–1 (CYP102) and 3.7 × 10^8 s^–1 (CYP119), at 288 K. Cyclic voltammetry of Prodan in MeCN shows a reversible reduction peak at −1.85 V vs NHE that becomes chemically irreversible and shifts positively upon addition of water. A quasireversible reduction at −0.88 V was observed in an aqueous buffer (pH 7.3). The excited-state reduction potential of Prodan (and Badan) is estimated to vary from about +0.6 V (vs NHE) in polar aprotic media (MeCN) to approximately +1.6 V in water. Tryptophan quenching of Badan/Prodan fluorescence in CYPs and Brij 58 micelles is exergonic by ≤0.5 V and involves tryptophan oxidation by excited Badan/Prodan, coupled with a fast reaction between the reduced dye and water. Photoreduction is a new quenching mechanism for 2-(N,N-dimethylamino)-6-propionylnaphthalene dyes that are often used as solvatochromic polarity probes, FRET donors and acceptors, as well as reporters of solvation dynamics.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/48477,
title ="Assembly, characterization, and electrochemical properties of immobilized metal bipyridyl complexes on silicon(111) surfaces",
author = "Blakemore, James D. and Lattimer, Judith R.",
pages = "INOR 348",
month = "August",
year = "2014",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140813-084518207",
note = "© 2014 American Chemical Society.",
revision_no = "13",
abstract = "A route to bipyridine-functionalized silicon(111) surfaces has been developed which gave submonolayer surface coverage of immobilized 4-vinyl-2,2'-bipyridyl (vbpy). The remaining atop sites of the silicon surface were passivated with Me groups. The immobilized bipyridyl ligands bound metal ions, thus enabling assembly of metal complexes on the silicon surface. XPS studies demonstrated that [Cp*Rh(vbpy)Cl]Cl, [Cp*Ir(vbpy)Cl]Cl, and Ru(acac)2vbpy were assembled on the surface (Cp* is pentamethylcyclopentadienyl, acac is acetylacetonate). For the surface prepd. with iridium, X-ray absorption spectroscopy at the Ir L_(III) edge showed an edge energy and post-edge features consistent with a powder sample of [Cp*Ir(bpy)Cl]Cl (bpy is 2,2'-bipyridyl). Cyclic voltammetry data for surfaces prepd. on highly doped, conducting silicon confirmed electroactivity of the assembled complexes.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/48354,
title ="Factors affecting bismuth vanadate photoelectrochemical performance",
author = "Sinclair, Timothy S. and Winkler, Jay R.",
pages = "INOR 1028",
month = "August",
year = "2014",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140811-152908877",
note = "© 2014 American Chemical Society.",
revision_no = "9",
abstract = "Bismuth vanadate has recently emerged as a promising photoanode material for solar water splitting applications. Reports on unmodified BiVO_4 showed large variations in photocurrent generation. We prepd. BiVO_4 photoanodes with different chem. surface compns. and morphologies by electrodeposition and spin coating. We devised an electrodeposition procedure with iodide added to the plating bath; this way, we could obtain BiVO_4 films with matching thicknesses and control surface Bi/V ratios. Morphologies were quantified from scanning microscopy image anal. Smaller crystallites were synthesized by spin coating. We correlated chem. surface compn. and morphol. to photocurrent densities and obsd. trends only from bivariate data. Best photoelectrochem. performance required low surface Bi/V ratios, short distances to crystallites' edges, and crystallite areas that were small enough to provide good elec. contact to the FTO underneath yet sufficiently large to prevent mass transport limitations.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/48353,
title ="First-\u200brow transition metal oxide nanoparticle water oxidation catalysts made by pulsed laser ablation in liquids",
author = "Blakemore, James D. and Gray, Harry B.",
pages = "INOR 1029",
month = "August",
year = "2014",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140811-152657186",
note = "© 2014 American Chemical Society.",
revision_no = "8",
abstract = "Conversion of solar energy into storable fuels, such as hydrogen from light-driven water splitting, will be the most viable future source of energy. To meet the world's energy demand, materials must be robust, based on earth-abundant elements, and efficient. We synthesized novel first-row transition metal oxide nanomaterials, using pulsed laser ablation in liqs. (PLAL). This method offers size and compn. control through many tunable exptl. parameters. Unlike electrodeposited catalysts, nanoparticles made by PLAL are suitable for mech. deposition on photoanodes in integrated solar water splitting devices. Mixed-metal materials were synthesized by adding metal ions into the aq. ablation liq. With PLAL, many different nanocatalysts can readily be prepd. and screened for water oxidn. activity. Our iron-nickel-oxygen nanocatalysts exhibited varying nickel content and cryst. phases, depending on ablation target, ion concn., and laser pulse energy. Characterization with XPS, powder x-ray diffraction, and electrochem. revealed that high amts. of jamborite nickel hydroxide in the partially cryst. nanomaterials led to highest water oxidn. activity in alk. conditions, with overpotentials of <300 mV at 10 mA cm^(-2).",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/48613,
title ="Noncovalent immobilization of electrocatalysts for fuel production on carbon electrodes",
author = "Blakemore, James D. and Gupta, Ayush",
pages = "AEI 30",
month = "August",
year = "2014",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140815-110039335",
note = "© 2014 American Chemical Society.",
revision_no = "10",
abstract = "Assembling systems for the conversion of solar light energy into chem. fuels (i.e., artificial photosynthesis) requires the development of strategies for functionalization of electrode surfaces with catalysts. We have demonstrated that mol. catalysts for fuel-forming reactions can be immobilized on graphitic carbon electrode surfaces via noncovalent interactions. Our general approach relies on a pyrene-appended bipyridine ligand that serves as the linker between the catalysts and the surface. Immobilization of a rhodium proton-redn. catalyst and a rhenium CO_2-redn. catalyst afford electrocatalytically active assemblies. XPS and electrochem. studies confirm catalyst immobilization. Redn. of the rhodium system in the presence of p-toluenesulfonic acid results in catalytic H_2 prodn., while redn. of the rhenium system in the presence of CO_2 results in catalytic CO prodn.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/48423,
title ="Organometallic photoreductants",
author = "Sattler, Wesley and Winkler, Jay",
pages = "INOR 406",
month = "August",
year = "2014",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140812-135326530",
note = "© 2014 American Chemical Society.",
revision_no = "9",
abstract = "We have synthesized and fully characterized several tungsten arylisocyanide complexes, W(CNAr)_6, all of which exhibit intense metal-to-ligand charge transfer (MLCT) absorptions in the visible region of the spectrum. The lowest triplet excited state is emissive, with lifetimes ranging from 17 ns to 3.0 μs depending on the arylisocyanide ligand. A modular synthesis has been developed for tungsten oligoaryl isocyanide complexes whose triplet excited states, *W(CNAr)_6, are extremely powerful reductants: *W(CNAr)_6/[W(CNAr)6]+ potentials are near -2.7 V vs. Cp_2Fe/Cp_2Fe+. *W(CNAr)6 complexes rapidly reduce anthracene, benzophenone, and cobalticenium ion, thereby demonstrating that very challenging electron transfer reactions can be driven by these sensitizers. We are extending our work to include investigations of the photophysics and photochem. of closely related arylisocyanide complexes of chromium and molybdenum.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/48606,
title ="Recruiting the next generation of chemists through hands-\u200bon research experiences",
author = "Hansen, Michelle and Dasgupta, Siddharth",
pages = "CHED 120",
month = "August",
year = "2014",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140815-100702535",
note = "© 2014 American Chemical Society.",
revision_no = "8",
abstract = "Mentoring future scientists and doing groundbreaking lab. research are not mutually exclusive. They actually strengthen each other. Our NSF Solar Fuels Center for Chem. Innovation has implemented a robust outreach program consisting of 3 components. In the Solar Energy Activities Lab (SEAL), high school and college students in our Solar Army search for robust metal-oxide materials with tools and coaching by CCI scientists. CCI investigators follow up with more advanced theor. and exptl. work on these and related materials, while gaining fresh insights and perspectives from training and guiding the students. In Juice-from-Juice, CCI scientists are training teachers to make dye-sensitized solar cells using natural pigments from fruits and vegetables. This maps well into the high school STEM curriculum by teaching fundamental concepts in chem., physics, and biol. The third program targets middle school kids from disadvantaged backgrounds who have not had much exposure to chem. By having a meaningful scientific experience before entering high school, these kids are more likely to pursue STEM careers than otherwise. We have been working with Informal Science Educational professionals, high school \"near peer\" mentors, evaluators, and local museums to provide a groundbreaking model of chem. informal science education outside the classroom. These types of symbiotic relationships are important steps toward the goal of a scientifically literate citizenry.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/48418,
title ="Solar-\u200bdriven water splitting",
author = "Gray, Harry",
pages = "INOR 485",
month = "August",
year = "2014",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140812-134809714",
note = "© 2014 American Chemical Society.",
revision_no = "7",
abstract = "Investigators in our NSF CCI Solar Fuels Program are working on catalysts for both water oxidn. to dioxygen (OER) and proton redn. to dihydrogen (HER). Promising HER heterogeneous catalysts include Ni-Mo and CoP, which reduce protons in aq. solns. with catalytic efficiencies near that of platinum. We also are investigating sol. iron, cobalt, and nickel complexes that catalyze dihydrogen prodn. from protic solns. at relatively low overpotentials. Employing laser flash/quench and NMR methods, we have shown that the active intermediate in cobalt-catalyzed dihydrogen evolution is a Co(II)-hydride. Among several new photoanode materials synthesized at Caltech, one that is esp. promising is dinitrogen-intercalated tungsten oxide. This 1.9 eV band gap oxide exhibits photocurrent under illumination out to 640 nm with a faradaic efficiency near unity for OER in perchloric acid solns. In other work of note, we have shown that robust metal-oxide water oxidn. catalysts can be made by pulsed laser ablation of precursors in liqs.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/48484,
title ="Tungsten photosensitizers",
author = "Sattler, Wesley and Winkler, Jay R.",
pages = "INOR 343",
month = "August",
year = "2014",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140813-091541691",
note = "© 2014 American Chemical Society.",
revision_no = "9",
abstract = "The development of photosensitizers is of great interest due to their ability to carry out difficult inorg. and org. reactions in their excited states. We have developed a new class of homoleptic arylisocyanide tungsten photosensitizers, W(CNAr)_6, and studied their photoelectrochem. properties. A modular synthesis allows for the prodn. of a variety of oligoaryl isocyanide complexes of tungsten, all of which display intense metal-to-ligand charge transfer (MLCT) absorptions in the visible region. Their excited states, *W(CNAr)_6, are highly emissive with lifetimes ranging from 17 ns to 3.0 μs depending on the arylisocyanide ligand. *W(CNAr)_6, are extremely powerful reductants: [W(CNAr)_6]^+/*W(CNAr)_6 redn. potentials are more neg. than -2.6 V vs. Cp2Fe^+/Cp2Fe.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/48486,
title ="Upgrading light olefins by trimerization catalysis",
author = "Sattler, Aaron and Winkler, Jay R.",
pages = "INOR 341",
month = "August",
year = "2014",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140813-091823187",
note = "© 2014 American Chemical Society.",
revision_no = "8",
abstract = "Activation of a (phenoxy-imine) titanium tri-Me complex with one equiv. of B(C_6F_5)_3 effects the catalytic trimerization of ethylene. Stoichiometric activation with B(C_6F_5)_3 allows for mechanistic studies to be conducted, which give insight into catalyst initiation, trimerization, and decompn., and the relative rates of these processes. In addn. to ethylene, α-olefins are oligomerized with high selectivity for trimers (> 95%), of which approx. 85% are one regioisomer.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/43215,
title ="A Euclidean perspective on the unfolding of azurin: chain motion",
author = "Gray, Harry B. and Warren, Jeffrey J.",
journal = "Journal of Biological Inorganic Chemistry",
volume = "19",
number = "4-5",
pages = "555-563",
month = "June",
year = "2014",
doi = "10.1007/s00775-013-1077-2",
issn = "0949-8257",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140106-090740745",
note = "© 2013 SBIC. \n\nReceived: 23 September 2013; Accepted: 6 December 2013. Published online 31 December 2013. \n\nTopical Issue in honor of Ivano Bertini. \n\nWork at the California Institute of Technology was supported by the National Institutes of Health (grant GM095037 to J.J.W. and grant DK019038 to H.B.G. and J.R.W.).",
revision_no = "31",
abstract = "We present a new approach to visualizing and quantifying the displacement of segments of Pseudomonas aeruginosa azurin in the early stages of denaturation. Our method is based on a geometrical method developed previously by the authors, and elaborated extensively for azurin. In this study, we quantify directional changes in three α-helical regions, two regions having β-strand residues, and three unstructured regions of azurin. Snapshots of these changes as the protein unfolds are displayed and described quantitatively by introducing a scaling diagnostic. In accord with molecular dynamics simulations, we show that the long α-helix in azurin (residues 54–67) is displaced from the polypeptide scaffolding and then pivots first in one direction, and then in the opposite direction as the protein continues to unfold. The two β-strand chains remain essentially intact and, except in the earliest stages, move in tandem. We show that unstructured regions 72–81 and 84–91, hinged by β-strand residues 82–83, pivot oppositely. The region comprising residues 72–91 (40 % hydrophobic and 16 % of the 128 total residues) forms an effectively stationary region that persists as the protein unfolds. This static behavior is a consequence of a dynamic balance between the competing motion of two segments, residues 72–81 and 84–91.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/42835,
title ="Electron Flow through Metalloproteins",
author = "Winkler, Jay R. and Gray, Harry B.",
journal = "Chemical Reviews",
volume = "114",
number = "7",
pages = "3369-3380",
month = "April",
year = "2014",
doi = "10.1021/cr4004715",
issn = "0009-2665",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20131204-141845630",
note = "© 2013 American Chemical Society. \n\nReceived: August 26, 2013. Published: November 27, 2013. \n\nElectron transfer research in our laboratories is supported by the National Institutes of Health (DK-019038), the National Science Foundation (CHE-1305124), and the Arnold and Mabel Beckman Foundation.",
revision_no = "34",
abstract = "Electron flow through proteins and protein assemblies in the\nphotosynthetic and respiratory machinery commonly occurs\nbetween metal centers or other redox cofactors that are\nseparated by relatively large molecular distances, often in the\n10−20 Å range. To inorganic chemists, such long-distance\nelectron transfer was a mystery for many years, as we were\naccustomed to close-contact models for the transition states of\nsimple self-exchange reactions between metal ions in aqueous\nsolution. One of our favorite reactions was the ferrous/ferric\nself-exchange, which had been investigated thoroughly by\nRichard (Dick) Dodson at the Brookhaven National Laboratory\nin the 1940s (and published in Journal of the American Chemical\nSociety in 1950). Dodson showed that the half-time for this\nreaction was on the order of seconds, which he noted was “fast”\nbut in today’s femtosecond world is very “slow”. Indeed, this\nvery simple electron transfer, where no bonds are formed or\nbroken, was found to be orders of magnitude slower than long-distance electron flow through metalloprotein molecules. How could this be?",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/55726,
title ="Labeling metal oxide nanoparticles with optical dyes: Bioimaging applications of corrole-metal oxide nanoconjugates",
author = "Sorasaenee, Karn and Blumenfeld, Carl M.",
journal = "Abstracts of Papers of the American Chemical Society",
volume = "247",
pages = "173-BIOT",
month = "March",
year = "2014",
issn = "0065-7727",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150312-082719382",
note = "© 2014 American Chemical Society.",
revision_no = "12",
abstract = "Probe development involving nanoscale materials has become increasingly significant and at the forefront in\nmol. imaging for both diagnosis and drug development based on improved understanding of biol. processes.\nVarious nanosized probes, namely, quantum dots and superparamagnetic iron oxides, have been explored using\nappropriate imaging modalities and biomedical studies. Owing to their vast surface area and extensive\npossibility for surface decoration with multiple groups to attain desirable functionalities, metal oxide\nnanomaterials, such as TiO_2 and ZnO, offer unique benefits over traditional small mols. and biomols. as contrast\nagents. Examples of potential near-IR contrast agents involving TiO_2 nanoparticle surfaces covalently decorated\nwith fluorescent corroles will be presented. Corrole prepn. and conjugation of the corroles to TiO_2\nnanoparticles will be discussed. Photophys. and imaging studies of the corrole-TiO_2 nanocojugates will be\naddressed.",
}
@book_section {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/45866,
title ="Chemists: Public Outreach Is an Essential Investment of Time, Not a Waste of It",
author = "Bracher, Paul J. and Gray, Harry B.",
number = "1157",
pages = "37-50",
month = "March",
year = "2014",
doi = "10.1021/bk-2014-1157.ch005",
isbn = "9780841229389",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140521-093549336",
note = "© 2014 American Chemical Society. Publication Date (Web): March 10, 2014. Our research on solar fuels and the outreach efforts that accompany it are supported by the NSF CCI Program (CCI Solar, CHE-1305124). We thank the many scientists in ccr Solar who power our outreach efforts with their dedicated service as mentors in local schools and clubs. CCI Solar's outreach efforts are coordinated and managed by Carolyn Panerson and Siddharth Dasgupta. The\nSHArK and SEAL programs owe their success to the instrument platforms developed by Bruce Parkinson, Jay Winkler, and their coworkers. The SEAL program has been coordinated at Caltech by Jillian Dempsey, James McKone, Hill Harman, and James Blakemore, and on an international scale by Jennifer\nSchuttlefield. The Juice-from-Juice kit was developed by Qixi Mi and Michael Walter (Caltech), along with Debbie Hawks (Blair High School) and Gurupreet Khalsa (Pasadena Unified School District). The project has subsequently been\ncoordinated at Caltech by Shane Ardo, Tania Damton, and Amanda Shing. CCI Solar's ISE efforts have been spearheaded by Benjamin Dickow (WSSC), Ariel Levi Simons (Wildwood School), Anna Beck (Caltech), and P.J.B. (Caltech). P.J.B. gratefully acknowledges an NSF American Competitiveness in Chemistry postdoctoral fellowship grant (CHE-0936996). We also thank ACS President Marinda Li Wu, H. N. Cheng, and Sadiq Shah for organizing the Vision 2025 symposium and for the opportunity to discuss these important issues that face the chemical enterprise.",
revision_no = "10",
abstract = "In this chapter, we discuss the state of the public image of chemistry and some of the potential consequences of its deterioration. We explain why it is important that chemists engage the public to educate citizens about science and communicate the value of scientific research. Next, as an example of how chemists can interact with the public in a meaningful manner related to their research, we discuss the development and implementation of a multifaceted outreach program by our group at Caltech. We close with suggestions for how chemists can create their own outreach activities and how our field can encourage this work by recognizing and rewarding it.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/45329,
title ="Cobalt catalyzed hydrogen evolution and formic acid dehydrogenation",
author = "Marinescu, Smaranda C. and Laga, Stephanie M.",
pages = "INOR-420",
month = "March",
year = "2014",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140429-155014408",
note = "© 2014 American Chemical Society.",
revision_no = "13",
abstract = "A Co^I-triphos complex (triphos = 1,1,1-tris(diphenylphosphinomethyl)ethane) reacts at room temp. with ptoulenesulfonic\nacid monohydrate in acetonitrile to generate hydrogen (0.5 equiv) and Co^(II) with a driving\nforce of just 30 meV/Co. Protonation of Co^I produces a transient Co^(III)-H complex that has been characterized\nby NMR spectroscopy. The Co^(III)-H intermediate decays by second-order kinetics with an inverse dependence\non acid concn. Anal. of the kinetics suggests that Co^(III)-H produces hydrogen by a dominant heterolytic\nchannel in which a highly reactive Co^(II)-H transient is generated by Co^I redn. of Co^(III)-H. The Co^I-triphos\ncomplex also reacts with excess formic acid to produce H_2 and CO_2. The mechanism of this transformation\nhas been probed electrochem. and in studies of the gas evolution kinetics.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/45210,
title ="DNA interactions with cytotoxic platinum-corrole conjugates",
author = "Pribisko, Melanie A. and Tang, Grace A.",
pages = "INOR-591",
month = "March",
year = "2014",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140425-082253626",
note = "© 2014 American Chemical Society.",
revision_no = "11",
abstract = "One of the great challenges in cancer treatment is the selective targeting of cancer cells over normal cells. The\nspecific nuclear penetration of functionalizable corroles introduces the possibility of targeted, efficient delivery of\ncovalently-tethered chemotherapy drugs. Indeed, previous expts. demonstrate a sulfonated corrole can act as\na carrier mol. for chemotherapeutic agents, specifically the DNA-intercalating anthracycline drug doxorubicin,\nresulting in enhanced drug cytotoxicity. Anticancer drugs due to their notorious lack of specificity for cancerous\ncells over normal cells and their need to be localized in the nucleus to be effective. Exploiting the selective\nuptake of the sulfonated corrole into the nucleus of brain metastatic prostate carcinoma by synthesizing a\nplatinum-corrole conjugate could result in a highly specific and effective treatment for this type of\nmetastases. Synthethic routes to bioactive platinum-corrole conjugates and their interactions with DNA\nwill be presented.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/44644,
title ="Earth-abundant hydrogen evolution electrocatalysts",
author = "McKone, James R. and Marinescu, Smaranda C.",
journal = "Chemical Science",
volume = "5",
number = "3",
pages = "865-878",
month = "March",
year = "2014",
doi = "10.1039/C3SC51711J",
issn = "2041-6520",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140403-143550660",
note = "This journal is © The Royal Society of Chemistry 2014. \n\nReceived 19th June 2013; Accepted 4th November 2013. First published online 05 Nov 2013. \n\nThis work was supported by the National Science Foundation “Powering the Planet” Center for Chemical Innovation (CHE-1305124). S.C.M. acknowledges the National Science Foundation for a CCI postdoctoral fellowship. J.R.M. additionally acknowledges the U.S. Department of Energy, Office of Science, for a graduate research fellowship.",
revision_no = "14",
abstract = "Splitting water to hydrogen and oxygen is a promising approach for storing energy from intermittent renewables, such as solar power. Efficient, scalable solar-driven electrolysis devices require active electrocatalysts made from earth-abundant elements. In this mini-review, we discuss recent investigations of homogeneous and heterogeneous hydrogen evolution electrocatalysts, with emphasis on our own work on cobalt and iron complexes and nickel-molybdenum alloys.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/45223,
title ="Electron Transfer in Ru-Modified Cytochrome cb562",
author = "Ford, N. B. and Shin, D. W.",
journal = "Journal of Biological Inorganic Chemistry",
volume = "19",
number = "S1",
pages = "S335",
month = "March",
year = "2014",
doi = "10.1007/s00775-014-1095-8",
issn = "0949-8257",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140425-094321995",
note = "© 2014 Springer. CONTROL ID: 1721487",
revision_no = "11",
abstract = "We explore electron tunneling rates and unfolded protein dynamics in a series of Ru-modified cytochrome cb562 variants. [Ru(bpy)2(5-iodoacetamido-1,10-phenanthroline)]2^+ is covalently coupled to single-cysteine mutations, distributed throughout the protein.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/45203,
title ="Electron flow through tyrosine in Ru-modified P. aeruginosa azurin",
author = "Warren, J. J. and Herrera, N.",
journal = "Journal of Biological Inorganic Chemistry",
volume = "19",
number = "S1",
pages = "S271",
month = "March",
year = "2014",
doi = "10.1007/s00775-014-1095-8",
issn = "0949-8257",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140425-070521756",
note = "© 2014 Springer. CONTROL ID: 1715120.",
revision_no = "16",
abstract = "Functional biological redox chains rely upon control of both electrons and acid/base equivalents. The pH dependent reduction potentials of many enzymes and biological cofactors (e.g., tryptophan and tyrosine) underscore the relationship between electron transfer (ET) and proton transfer. ",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/45205,
title ="Functionalized Corroles as Theranostics for Prostate Cancer",
author = "Yen, M. P. and Mangold, S. A.",
journal = "Journal of Biological Inorganic Chemistry",
volume = "19",
number = "S1",
pages = "S680",
month = "March",
year = "2014",
doi = "10.1007/s00775-014-1095-8",
issn = "0949-8257",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140425-071804850",
note = "© 2014 Springer.",
revision_no = "16",
abstract = "Recent synthetic advancement have made it possible to produce substituted derivatives of meso-5,10,15-(tris)pentafluorophenylcorrole (H3tpfc).",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/45200,
title ="Intra- and intermolecular electron hopping via tryptophan in azurin",
author = "Takematsu, K. and Williamson, H.",
journal = "Journal of Biological Inorganic Chemistry",
volume = "19",
number = "Supplement1",
pages = "S231",
month = "March",
year = "2014",
doi = "10.1007/s00775-014-1095-8",
issn = "0949-8257",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140424-153153082",
note = "© 2014 Springer. CONTROL ID: 1709659",
revision_no = "11",
abstract = "We previously showed that electron transfer (ET) between electronically excited Re (^*RE) and Cu(I)in Re-modified Pseudomonas aeruginosa azurin mutant ReH124W122Cu(I)(Re=4,7-dimethylphenanthrolineRe(CO)3) is facilitated by W122, with hopping occurring over 19 Å in 30 ns, >100x faster than single step electron tunneling.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/45193,
title ="Ion Channel Dynamics: Physical monitoring of the gating event using electrophysiology and time-resolved spectroscopy",
author = "Shafaat, O. S. and Winkler, J. R.",
journal = "Journal of Biological Inorganic Chemistry",
volume = "19",
number = "Supplement1",
pages = "S583",
month = "March",
year = "2014",
doi = "s00775-014-1095-8",
issn = "0949-8257",
isbn = "ISSN 0949-8257",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140424-140725710",
note = "© 2014 Springer. CONTROL ID: 1698961",
revision_no = "14",
abstract = "Pentameric ligand-gated Ion channels are a large class of proteins involved in electrochemical signal transduction. This family includes cation selective Ion channels such as the acetylcholine receptor, as well as anion selective Ion channels, such as the GABA receptor.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/45221,
title ="Photo-initiated and electron transfer reactivity of ruthenium-labeled cytochrome P450",
author = "Ener, M. E. and Coelho, P. S.",
journal = "Journal of Biological Inorganic Chemistry",
volume = "19",
number = "S1",
pages = "S219",
month = "March",
year = "2014",
doi = "10.1007/s00775-014-1095-8",
issn = "0949-8257",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140425-092704426",
note = "© 2014 Springer.",
revision_no = "11",
abstract = "High-valent iron species are responsible for the catalytic activity of various hemes enzymes, including the ubiquitous cytochromes P450.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/44645,
title ="Long-Range Electron Tunneling",
author = "Winkler, Jay R. and Gray, Harry B.",
journal = "Journal of the American Chemical Society",
volume = "136",
number = "8",
pages = "2930-2939",
month = "February",
year = "2014",
doi = "10.1021/ja500215j",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140403-144433692",
note = "© 2014 American Chemical Society. ACS AuthorChoice - This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes. \n\nPublished In Issue: February 26, 2014. Article ASAP: February 18, 2014. Just Accepted Manuscript: February 05, 2014. Received: January 08, 2014. \n\nOur electron transfer research is supported by the National\nInstitutes of Health (DK-019038), the National Science\nFoundation (CHE-1305124), the Gordon and Betty Moore\nFoundation, and the Arnold and Mabel Beckman Foundation. \n\nSupporting Information: Estimation of the gas-phase Fc+/Fc electron exchange\ntunneling energy and additional comparisons of amino acid\noccurrence frequencies. This material is available free of charge\nvia the Internet at http://pubs.acs.org.",
revision_no = "17",
abstract = "Electrons have so little mass that in less than a second they can tunnel through potential energy barriers that are several electron-volts high and several nanometers wide. Electron tunneling is a critical functional element in a broad spectrum of applications, ranging from semiconductor diodes to the photosynthetic and respiratory charge transport chains. Prior to the 1970s, chemists generally believed that reactants had to collide in order to effect a transformation. Experimental demonstrations that electrons can transfer between reactants separated by several nanometers led to a revision of the chemical reaction paradigm. Experimental investigations of electron exchange between redox partners separated by molecular bridges have elucidated many fundamental properties of these reactions, particularly the variation of rate constants with distance. Theoretical work has provided critical insights into the superexchange mechanism of electronic coupling between distant redox centers. Kinetics measurements have shown that electrons can tunnel about 2.5 nm through proteins on biologically relevant time scales. Longer-distance biological charge flow requires multiple electron tunneling steps through chains of redox cofactors. The range of phenomena that depends on long-range electron tunneling continues to expand, providing new challenges for both theory and experiment.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/47117,
title ="Conformational Dynamics of a Fast Folding Cytochrome Captured by Time-Resolved Spectroscopy",
author = "Bouley Ford, Nicole D. and Shin, Dong Woo",
journal = "Biophysical Journal",
volume = "106",
number = "2",
pages = "473A",
month = "January",
year = "2014",
doi = "10.1016/j.bpj.2013.11.2674",
issn = "0006-3495",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140710-082331092",
note = "© 2014 Biophysical Society. Published by Elsevier Inc.",
revision_no = "12",
abstract = "We probe intrachain contact dynamics in unfolded cytochrome cb562 by monitoring heme quenching of excited ruthenium photosensitizers covalently bound to residues along the polypeptide. Tertiary contact formation kinetics provide insight into the upper \"speed limit\" for protein folding rates. The rate constants exhibit a power-law dependence on the number of peptide bonds between the heme and Ru complex. Adherence of our data to a slope of −1.5 is consistent with theoretical models for ideal, freely-jointed Gaussian chain polymers, but its magnitude is smaller than reported for synthetic polypeptides. We also examine rates of contact formation within a stable loop in a His63-heme ligated form of the protein. Additionally, we resolve millisecond-timescale folding by coupling time-resolved fluorescence energy transfer (trFRET) to a continuous flow microfluidic mixer to obtain intramolecular distance distributions throughout the folding process. Our results suggest that cytochrome cb562 is minimally frustrated.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/47119,
title ="Prokaryotic Cys-Loop Receptor Homologs as Mechanistic Models for Channel Function",
author = "Rienzo, Matthew and Shafaat, Oliver S.",
journal = "Biophysical Journal",
volume = "106",
number = "2",
pages = "545A",
month = "January",
year = "2014",
doi = "10.1016/j.bpj.2013.11.3037",
issn = "0006-3495",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140710-083537652",
note = "© 2014 Biophysical Society. Published by Elsevier Inc.",
revision_no = "11",
abstract = "Pentameric ligand-gated ion channels are a large class of proteins involved in electrochemical signal transduction. Signal transduction is a result of two processes: (1) ligand binding to the receptor and (2) a conformational wave that opens a pore far from the binding site (>20Å). Recently, two prokaryotic members of this family were identified, one from Gloeobacter violaceus (GLIC), and one from Erwinia chrysanthemi (ELIC). These receptors provide a valuable platform for the study of ligand binding and channel gating in the Cys-loop receptor family.\n\nReceptors were expressed heterologously in Xenopus laevis oocytes, and whole-cell voltage-clamp electrophysiology was used as a reporter for ligand binding and channel gating. To examine the proton-binding event in GLIC, unnatural amino acids were incorporated via nonsense-suppression with chemically acylated tRNA. This approach provides a subtle probe of intrasubunit interactions with the highly sensitive H11' site, which has been previously identified as necessary for the proton sensitivity of GLIC. A unique pair of proline residues at the extracellular terminus of the M1 helix were also investigated to examine potential intersubunit interactions that may play a role in channel gating.\n\nDespite the availability of putative \"open\" and \"closed\" X-ray structures of GLIC and ELIC, the mechanism of gating is not yet clear. Gating is a dynamic process initiated with ligand binding and resulting in conformational changes and pore opening tens of angstroms away. To fully understand this process will require a dynamic picture of the events that occur during the gating of ion channels, which we ultimately aim to uncover using time-resolved fluorescence energy transfer. Progress towards the development of temporal control for triggering channel opening/closing will be discussed.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/44051,
title ="Will Solar-Driven Water-Splitting Devices See the Light of Day?",
author = "McKone, James R. and Lewis, Nathan S.",
journal = "Chemistry of Materials",
volume = "26",
number = "1",
pages = "407-414",
month = "January",
year = "2014",
doi = "10.1021/cm4021518",
issn = "0897-4756",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140228-085825144",
note = "© 2013 American Chemical Society.\n\nPublished In Issue January 14, 2014; Article ASAP October 14, 2013; Just Accepted Manuscript August 27, 2013; Received: July 01, 2013; Revised: August 22, 2013.\n\nThis article is part of the Celebrating Twenty-Five Years of Chemistry of Materials special issue.\n\nN.S.L. acknowledges support from the Joint Center for\nArtificial Photosynthesis, a DOE Energy Innovation Hub,\nsupported through the Office of Science of the U.S.\nDepartment of Energy under Award Number DE-SC0004993.\nJ.R.M. and H.B.G. acknowledge the National Science\nFoundation for support through the Powering the Planet\nCenter for Chemical Innovation, Grant CHE-1305124. J.R.M.\nacknowledges the DOE Office of Science for a graduate\nresearch fellowship. The authors thank Dr. Shane Ardo and\nAdam Nielander for helpful comments during the preparation\nof this manuscript.",
revision_no = "11",
abstract = "Through decades of sustained effort, researchers have made substantial progress on developing technologies for solar-driven water splitting. Nevertheless, more basic research is needed before prototype devices with a chance for commercial success can be demonstrated. In this Perspective, we summarize the major design constraints that motivate continued research in the field of solar-driven water splitting. Additionally, we discuss key device components that are now available for use in demonstration systems and prototypes. Finally, we highlight research areas where breakthroughs will be critical for continued progress toward commercial viability for solar-driven water-splitting devices.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/43700,
title ="Redox Properties of Mixed Methyl/Vinylferrocenyl Monolayers on Si(111) Surfaces",
author = "Lattimer, Judith R. C. and Brunschwig, Bruce S.",
journal = "Journal of Physical Chemistry C",
volume = "117",
number = "51",
pages = "27012-27022",
month = "December",
year = "2013",
doi = "10.1021/jp409958c",
issn = "1932-7447",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140206-113901424",
note = "© 2013 American Chemical Society. \n\nReceived: October 7, 2013; revised: November 27, 2013; published: December 2, 2013. \n\nWe thank Dr. James Blakemore for helpful discussions, Dr.\nLeslie O’Leary for training in silicon surface modification and discussions, and Joseph Beardslee and Dr. Ron Grimm for\nassistance with the instrumentation. This work was supported\nby the NSF Powering the Planet Center for Chemical\nInnovation (CHE-1305124), the National Science Foundation\n(CHE-1214152), and the Molecular Materials Research Center\nof the Beckman Institute at the California Institute of\nTechnology.",
revision_no = "13",
abstract = "We report the redox properties of Si(111) surfaces functionalized with a mixed monolayer of vinylferrocenyl and methyl moieties that have been characterized using spectroscopic, electrical, and electrochemical techniques. The silicon was functionalized using reaction conditions analogous to those of hydrosilylation, but instead of a H-terminated Si surface, a chlorine-terminated Si precursor surface was used to produce the linked vinyl-modified functional group. The functionalized surfaces were characterized by time-resolved photoconductivity decay, X-ray photoelectron spectroscopy, electrochemical measurements, and photoelectrochemical measurements. The functionalized Si surface was well passivated, exhibited high surface coverage and few remaining reactive Si atop sites, had a very low surface recombination velocity, and displayed little initial surface oxidation. The surface was stable toward atmospheric and electrochemical oxidation. The surface coverage of vinylferrocene (or fluorostyrene) was controllably varied from 0 up to 30% of a monolayer. Interfacial charge transfer to the attached ferrocene group was relatively rapid, and a photovoltage of 0.4 V was generated upon illumination of functionalized n-type silicon surfaces in CH_(3)CN.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/42806,
title ="Noncovalent Immobilization of Electrocatalysts on Carbon Electrodes for Fuel Production",
author = "Blakemore, James D. and Gupta, Ayush",
journal = "Journal of the American Chemical Society",
volume = "135",
number = "49",
pages = "18288-18291",
month = "December",
year = "2013",
doi = "10.1021/ja4099609",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20131203-150617731",
note = "© 2013 American Chemical Society. \n\nReceived: September 26, 2013. Publication Date (Web): November 18, 2013. \n\nThe authors thank Peter Agbo for helpful discussions regarding surface preparation and David Lacy for assistance with the GC product analysis. Research was carried out in part at the Molecular Materials Research Center of the Beckman Institute at Caltech. This work was supported by the NSF CCI Solar Fuels Program (CHE-1305124) and a CCI Postdoctoral Fellowship to J.D.B.",
revision_no = "20",
abstract = "We show that molecular catalysts for fuel-forming reactions can be immobilized on graphitic carbon electrode surfaces via noncovalent interactions. A pyrene-appended bipyridine ligand (P) serves as the linker between each complex and the surface. Immobilization of a rhodium proton-reduction catalyst, [Cp*Rh(P)Cl]Cl (1), and a rhenium CO_2-reduction catalyst, Re(P)(CO)_3Cl (2), afford electrocatalytically active assemblies. X-ray photoelectron spectroscopy and electrochemistry confirm catalyst immobilization. Reduction of 1 in the presence of p-toluenesulfonic acid results in catalytic H_2 production, while reduction of 2 in the presence of CO_2 results in catalytic CO production.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/43303,
title ="Enhanced Stability and Activity for Water Oxidation in Alkaline Media with Bismuth Vanadate Photoelectrodes Modified with a Cobalt Oxide Catalytic Layer Produced by Atomic Layer Deposition",
author = "Lichterman, Michael F. and Shaner, Matthew R.",
journal = "Journal of Physical Chemistry Letters",
volume = "4",
number = "23",
pages = "4188-4191",
month = "December",
year = "2013",
doi = "10.1021/jz4022415 ",
issn = "1948-7185",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140110-084420760",
note = "© 2013 American Chemical Society. \n\nReceived: October 16, 2013; Accepted: November 21, 2013; Published: November 21, 2013. \n\nThis work was supported through the Office of Science of the U.S. Department of Energy under award DE-SC0004993 to the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub. XPS and AFM data were collected at the Molecular Materials Research Center of the Beckman Institute of the California Institute of Technology. We thank Dr. Ragip Pala for helpful discussions.",
revision_no = "15",
abstract = "Atomic-layer deposition (ALD) of thin layers of cobalt oxide on n-type BiVO_4 produced photoanodes capable of water oxidation with essentially 100% faradaic efficiency in alkaline, pH = 13 electrolytes. By contrast, under the same operating conditions, BiVO_4 photoanodes without the Co oxide catalytic layer exhibited lower faradaic yields, of ca. 70%, for O_2 evolution and were unstable, becoming rapidly photopassivated. High numbers (>25) of ALD cycles of Co oxide deposition gave electrodes that displayed poor photoelectrochemical behavior, but 15–20 ALD cycles produced Co oxide overlayers ~1 nm in thickness, with the resulting photoelectrodes exhibiting a stable photocurrent density of 1.49 mA cm^(–2) at the oxygen-evolution potential and an open-circuit potential of 0.404 V versus the reversible hydrogen electrode, under 100 mW cm^(–2) of simulated air mass 1.5 illumination.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/43278,
title ="Enhancement of Anion Binding in Lanthanide Optical Sensors",
author = "Cable, Morgan L. and Kirby, James P.",
journal = "Accounts of Chemical Research",
volume = "46",
number = "11",
pages = "2576-2584",
month = "November",
year = "2013",
doi = "10.1021/ar400050t",
issn = "0001-4842",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140109-070700700",
note = "© 2013 American Chemical Society. \n\nReceived on March 5, 2013. Publication Date (Web): September 16, 2013. \n\nWe dedicate this Account to the memory of Michael Day,\na wonderful colleague and great friend. The authors would also like to acknowledge helpful comments by the reviewers of this manuscript. The research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautic and Space Administration and was sponsored by NASA's Astrobiology and Planetary Protection Programs (A.P., J.P.K.), the Department of Homeland Security's Chemical and Biological Research & Development Program (A.P.), and the NASA Graduate Student Research Program (M.L.C.). Work at Caltech was supported NIH Grant DKO19038 and the Arnold and Mabel Beckman Foundation.",
revision_no = "17",
abstract = "In the design of molecular sensors, researchers exploit binding interactions that are usually defined in terms of topology and charge complementarity. The formation of complementary arrays of highly cooperative, noncovalent bonding networks facilitates protein-ligand binding, leading to motifs such as the “lock-and-key”. Synthetic molecular sensors often employ metal complexes as key design elements as a way to construct a binding site with the desired shape and charge to achieve target selectivity. In transition metal complexes, coordination number, structure and ligand dynamics are governed primarily by a combination of inner-sphere covalent and outer-sphere noncovalent interactions. These interactions provide a rich variable space that researchers can use to tune structure, stability, and dynamics.\nIn contrast, lanthanide(III)-ligand complex formation and ligand-exchange dynamics are dominated by reversible electrostatic and steric interactions, because the unfilled f shell is shielded by the larger, filled d shell. Luminescent lanthanides such as terbium, europium, dysprosium, and samarium display many photophysical properties that make them excellent candidates for molecular sensor applications. Complexes of lanthanide ions act as receptors that exhibit a detectable change in metal-based luminescence upon binding of an anion. In our work on sensors for detection of dipicolinate, the unique biomarker of bacterial spores, we discovered that the incorporation of an ancillary ligand (AL) can enhance binding constants of target anions to lanthanide ions by as much as two orders of magnitude.\nIn this Account, we show that selected ALs in lanthanide/anion systems greatly improve sensor performance for medical, planetary science, and biodefense applications. We suggest that the observed anion binding enhancement could result from an AL-induced increase in positive charge at the lanthanide ion binding site. This effect depends on lanthanide polarizability, which can be established from the ionization energy of Ln^(3+) → Ln^(4+). These results account for the order Tb^(3+) > Dy^(3+) > Eu^(3+) ≈ Sm^(3+). As with many lanthanide properties, ranging from hydration enthalpy to vaporization energy, this AL-induced enhancement shows a large discrepancy between Tb^(3+) and Eu^(3+) despite their similarity in size, a phenomenon known as the “gadolinium break”. This discrepancy, based on the unusual stabilities of the Eu^(2+) and Tb^(4+) oxidation states, results from the half-shell effect, as both of these ions have half-filled 4f-shells. The high polarizability of Tb^(3+) explains the extraordinarily large increase in the binding affinity of anions for terbium compared to other lanthanides.\nWe recommend that researchers consider this AL-induced enhancement when designing lanthanide-macrocycle optical sensors. Ancillary ligands also can reduce the impact of interfering species such as phosphate commonly found in environmental and physiological samples.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/42848,
title ="Co_3O_4 Nanoparticle Water-Oxidation Catalysts Made by Pulsed-Laser Ablation in Liquids",
author = "Blakemore, James D. and Gray, Harry B.",
journal = "ACS Catalysis",
volume = "3",
number = "11",
pages = "2497-2500",
month = "November",
year = "2013",
doi = "10.1021/cs400639b ",
issn = "2155-5435",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20131205-085654384",
note = "© 2013 American Chemical Society.\n\nReceived: August 2, 2013; Revised: October 1, 2013; Published: October 3, 2013.\n\nWe thank Richard P. Gerhart for fabrication of the electrochemical\ncell used for the oxygen-detection experiment, and Bryce F. Sadtler and Alasdair W. McDowall for help with TEM. Research was carried out in the Laser Resource Center and the\nMolecular Materials Research Center of the Beckman Institute of the California Institute of Technology. This work was supported by the NSF CCI Solar Fuels Program (CHE-1305124) and the Arnold and Mabel Beckman Foundation.",
revision_no = "16",
abstract = "Surfactant-free, size- and composition-controlled, unsupported, <5-nm, quantum-confined cobalt oxide nanoparticles with high electrocatalytic oxygen-evolution activity were synthesized by pulsed laser ablation in liquids. These crystalline Co_3O_4 nanoparticles have a turnover frequency per cobalt surface site among the highest ever reported for Co_3O_4 nanoparticle oxygen evolution catalysts in base and overpotentials competitive with the best electrodeposited cobalt oxides, with the advantage that they are suitable for mechanical deposition on photoanode materials and incorporation in integrated solar water-splitting devices.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/42837,
title ="Intrachain Contact Dynamics in Unfolded Cytochrome cb_(562)",
author = "Bouley Ford, Nicole D. and Shin, Dong-Woo",
journal = "Journal of Physical Chemistry B",
volume = "117",
number = "42",
pages = "13206-13211",
month = "October",
year = "2013",
doi = "10.1021/jp403234h ",
issn = "1520-6106",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20131204-142946287",
note = "© 2013 American Chemical Society.\n\nReceived: April 1, 2013;\nRevised: August 11, 2013;\nPublished: August 30, 2013.\n\nWe celebrate Peter Wolynes, our very good friend and\ncollaborator. Our explorations of protein folding dynamics\nhave been greatly enhanced by the many discussions we have\nhad with him over the last 20 years. We thank Lionel Cheruzel,\nJeffrey Warren, Maraia Ener, and Katja Luxem for experimental\nassistance and helpful discussions. Our work was supported by\nNIH (Grants DK019038 and GM068461) and the Arnold and\nMabel Beckman Foundation.",
revision_no = "14",
abstract = "We have investigated intrachain contact dynamics in unfolded cytochrome cb_(562) by monitoring heme quenching of excited ruthenium photosensitizers covalently bound to residues along the polypeptide. Intrachain diffusion for chemically denatured proteins proceeds on the microsecond time scale with an upper limit of 0.1 μs. The rate constants exhibit a power-law dependence on the number of peptide bonds between the heme and Ru complex. The power-law exponent of −1.5 is consistent with theoretical models for freely jointed Gaussian chains, but its magnitude is smaller than that reported for several synthetic polypeptides. Contact formation within a stable loop was examined in a His63-heme ligated form of the protein under denaturing conditions. Loop formation accelerated contact kinetics for the Ru66 labeling site, owing to reduction in the length of the peptide separating redox sites. For other labeling sites within the stable loop, quenching rates were modestly reduced compared to the open chain polymer.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/42254,
title ="Tryptophan-Accelerated Electron Flow Across a Protein−Protein\nInterface",
author = "Takematsu, Kana and Williamson, Heather",
journal = "Journal of the American Chemical Society",
volume = "135",
number = "41",
pages = "15515-15525",
month = "October",
year = "2013",
doi = "10.1021/ja406830d",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20131105-131815168",
note = "© 2013 American Chemical Society. \n\nPublication Date (Web): September 13, 2013. Received: July 4, 2013. \n\nAuthor Contributions K.T. and H.W. contributed equally to this work. \nThe authors declare no competing financial interest. \n\nWe thank Yuling Shen, Crystal Shih, and Jeff Warren (Caltech), \nrespectively, for azurin mutant preparation, preliminary laser \nmeasurements, and helpful discussions. Prof. B. Brutschy \n(Frankfurt) is thanked for discussions on LILBID-MS, and \nHana Kvapilová and Jan Sýkora (JH Institute) for their help \nwith some of the TRIR and TCSPC emission experiments. \nResearch at Caltech was supported by NIH (DK019038 to \nHBG, JRW) and the Arnold and Mabel Beckman Foundation. \nThe TRIR experiments were funded by the STFC Rutherford \nAppleton Laboratory, Queen Mary University of London, and \nthe Ministry of Education of the Czech Republic grant \nLH13015. Crystal data were collected on the SSRL Beamline \n12-2 through the support of the Caltech Molecular\nObservatory, funded by the Gordon and Betty Moore \nFoundation, the Sanofi-Aventis Bioengineering Research\nProgram. ",
revision_no = "25",
abstract = "We report a new metallolabeled blue copper protein, Re126W122Cu^I Pseudomonas aeruginosa azurin, which has three redox sites at well-defined distances in the protein fold: Re^I(CO)_3(4,7-dimethyl-1,10-phenanthroline) covalently bound at H126, a Cu center, and an indole side chain W122 situated between the Re and Cu sites (Re-W122(indole) = 13.1 Å, dmp-W122(indole) = 10.0 Å, Re-Cu = 25.6 Å). Near-UV excitation of the Re chromophore leads to prompt Cu^I oxidation (<50 ns), followed by slow back ET to regenerate Cu^I and ground-state Re^I with biexponential kinetics, 220 ns and 6 μs. From spectroscopic measurements of kinetics and relative ET yields at different concentrations, it is likely that the photoinduced ET reactions occur in protein dimers, (Re126W122CuI)2 and that the forward ET is accelerated by intermolecular electron hopping through the interfacial tryptophan: ^*Re//←W122←Cu^I, where // denotes a protein–protein interface. Solution mass spectrometry confirms a broad oligomer distribution with prevalent monomers and dimers, and the crystal structure of the Cu^(II) form shows two Re126W122Cu^(II) molecules oriented such that redox cofactors Re(dmp) and W122-indole on different protein molecules are located at the interface at much shorter intermolecular distances (Re-W122(indole) = 6.9 Å, dmp-W122(indole) = 3.5 Å, and Re-Cu = 14.0 Å) than within single protein folds. Whereas forward ET is accelerated by hopping through W122, BET is retarded by a space jump at the interface that lacks specific interactions or water molecules. These findings on interfacial electron hopping in (Re126W122Cu^I)^2 shed new light on optimal redox-unit placements required for functional long-range charge separation in protein complexes.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/41895,
title ="Fifty years of metal oxos",
author = "Gray, Harry",
pages = "INOR-371",
month = "September",
year = "2013",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20131011-111111928",
note = "© 2013 American Chemical Society.",
revision_no = "11",
abstract = "The ligand field theory of multiple bonding in metal-oxos predicts that there must be an \"oxo wall\" between Fe-Ru-Os and Co-\nRh-Ir in the periodic table. The wall is still in pretty good shape, even after many attempts to break it down. I will discuss early\nwork on the structures and reactivities of metal oxos as well as new developments in the field.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/41099,
title ="Photoelectrochemical oxidation of anions by WO_3 in aqueous and nonaqueous electrolytes",
author = "Mi, Qixi and Coridan, Robert H.",
journal = "Energy and Environmental Science",
volume = "6",
number = "9",
pages = "2646-2653",
month = "September",
year = "2013",
doi = "10.1039/c3ee40712h ",
issn = "1754-5692",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130905-093517424",
note = "© 2013 The Royal Society of Chemistry. \n\nReceived 1st March 2013; Accepted 18th June 2013. First published online 18 Jun 2013. \n\nWe acknowledge the National Science Foundation (NSF) Powering the Planet Center for Chemical Innovation (CCI-Solar),\nGrants CHE-0802907 and CHE-0947829, and the Molecular Materials Research Center of the Beckman Institute at the\nCalifornia Institute of Technology, for support. QM acknowledges Dr Elizabeth A. Santori for assistance with the spectral response experiments, and the NSF for support as a CCI-Solar Postdoctoral Fellow.",
revision_no = "15",
abstract = "The behavior of WO_3 photoanodes has been investigated in contact with a combination of four anions (Cl−, CH_3SO_3−, HSO_4−, and ClO_4−) and three solvents (water, acetonitrile, and propylene carbonate), to elucidate the role of the semiconductor surface, the electrolyte, and redox kinetics on the current density vs. potential properties of n-type WO_3. In 1.0 M aqueous strong acids, although the flat-band potential (E_(fb)) of WO_3 was dominated by electrochemical intercalation of protons into WO_3, the nature of the electrolyte influenced the onset potential (E_(on)) of the anodic photocurrent. In aprotic solvents, the electrolyte anion shifted both E_(fb) and E_(on), but did not significantly alter the overall profile of the voltammetric data. For 0.50 M tetra(n-butyl)ammonium perchlorate in propylene carbonate, the internal quantum yield exceeded unity at excitation wavelengths of 300–390 nm, indicative of current doubling. A regenerative photoelectrochemical cell based on the reversible redox couple B_(10)Br_(10)^(˙−/2−) in acetonitrile, with a solution potential of 1.7 V vs. the normal hydrogen electrode, exhibited an open-circuit photovoltage of 1.32 V under 100 mW cm^(−2) of simulated Air Mass 1.5 global illumination.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/41894,
title ="Powering the planet with solar fuel",
author = "Gray, Harry B.",
pages = "MOTION-9",
month = "September",
year = "2013",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20131011-110858633",
note = "© 2013 American Chemical Society.",
revision_no = "10",
abstract = "Mol. hydrogen has emerged as an attractive candidate for a clean, renewable fuel to meet the world's skyrocketing demand for\nenergy. Hydrogenase enzymes that contain iron and nickel cofactors evolve H_2 catalytically from water with turnover\nfrequencies as high as 9000 s^(-1) at 30 C. However, the relative instability of these enzymes under aerobic conditions has led to\nthe search for robust inorg. catalysts that can produce hydrogen from water. Platinum is an excellent catalyst for proton redn.\nand hydrogen oxidn., but scarcity and high cost limit its widespread use. Our emphasis is on heterogeneous and homogeneous\ncatalysts made from earth-abundant elements that could be part of scalable solar fuel devices. Promising heterogeneous\ncatalysts include MoS_2 and Ni-Mo, which reduce protons in aq. solns. with catalytic efficiencies near that of platinum. While\nhomogeneous catalysts typically degrade faster than their heterogeneous counterparts, mol. systems are much easier to study\nmechanistically. Cobalt complexes enable electrocatalytic prodn. of H_2 from solns. with high turnover frequencies, and kinetics\ninvestigations have established that the reactive intermediate is a Co(II)-hydride. The challenge of water oxidn. in many ways\neclipses that of proton redn. The oxidn. reaction involves the rearrangement of more protons and electrons, and fewer good\ncatalysts for the reaction exist that are made of earth-abundant materials. We have found that 3 to 5 nm metal-oxide particles\nmade by pulsed laser ablation of precursors in water are very active water oxidn. catalysts. We hope to elucidate the electronic\nstructures of these very small nanoparticles as part of a program with the goal of understanding their mechanisms.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/42069,
title ="Electron Flow through Nitrotyrosinate in Pseudomonas aeruginosa Azurin",
author = "Warren, Jeffrey J. and Herrera, Nadia",
journal = "Journal of the American Chemical Society",
volume = "135",
number = "30",
pages = "11151-11158",
month = "July",
year = "2013",
doi = "10.1021/ja403734n",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20131025-104510564",
note = "© 2013 American Chemical Society.\n\nReceived: April 15, 2013; published: July 16, 2013.\n\nOur work was supported by NIH (DK019038 to H.B.G. and\nJ.R.W.; GM095037 to J.J.W.), an NSF Center for Chemical\nInnovation (Powering the Planet, CHE-0947829), and the\nArnold and Mabel Beckman Foundation. We also acknowledge\nthe Gordon and Betty Moore Foundation and the Sanofi-\nAventis Bioengineering Research Program for their support of\nthe Molecular Observatory facilities at the California Institute of Technology. X-ray crystallography data was collected at the Stanford Synchrotron Radiation Lightsource (SSRL), a Directorate of the SLAC National Accelerator Laboratory and an Office of Science User Facility operated for the U.S. Department of Energy, Office of Molecular Biology Program and Environmental Research, and by the National Institutes of Health, National Center for Research Resources, Biomedical Technology Program (P41RR001209), and the National Institute of General Medical Sciences.",
revision_no = "18",
abstract = "We have designed ruthenium-modified Pseudomonas aeruginosa azurins that incorporate 3-nitrotyrosine (NO_(2)YOH) between Ru(2,2′-bipyridine)_2(imidazole)(histidine) and Cu redox centers in electron transfer (ET) pathways. We investigated the structures and reactivities of three different systems: RuH107NO_(2)YOH109, RuH124NO_(2)YOH122, and RuH126NO_(2)YOH122. RuH107NO_(2)YOH109, unlabeled H124NO_(2)YOH122, and unlabeled H126NO_(2)YOH122 were structurally characterized. The pKa’s of NO_(2)YOH at positions 122 and 109 are 7.2 and 6.0, respectively. Reduction potentials of 3-nitrotyrosinate (NO_(2)YO^–)-modified azurins were estimated from cyclic and differential pulse voltammetry data: oxidation of NO_(2)YO^(–)122 occurs near 1.1 versus NHE; oxidation of NO_(2)YO^(–)109 is near 1.2 V. Our analysis of transient optical spectroscopic experiments indicates that hopping via NO_(2)YO^– enhances Cu^I oxidation rates over single-step ET by factors of 32 (RuH107NO_(2)YO^(–)109), 46 (RuH126NO_(2)YO^(–)122), and 13 (RuH124NO_(2)YO^(–)122).",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/41736,
title ="Generation of Powerful Tungsten Reductants by Visible Light Excitation",
author = "Sattler, Wesley and Ener, Maraia E.",
journal = "Journal of the American Chemical Society",
volume = "135",
number = "29",
pages = "10614-10617",
month = "July",
year = "2013",
doi = "10.1021/ja4047119",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20131008-104014521",
note = "© 2013 American Chemical Society.\n\nReceived: May 10, 2013; Published: July 15, 2013.\n\nDedicated to the memory of Nicholas J. Turro. The authors\nthank Jeffrey J. Warren, James R. McKone, and Oliver S.\nShafaat for helpful discussions. Our work is supported by the\nNational Science Foundation Center for Chemical Innovation\nin Solar Fuels (CHE-0802907); CCI postdoctoral fellowship to\nW.S.; and the Dow Chemical Company through the university\npartnership program (Agreement No. 227027AH).",
revision_no = "15",
abstract = "The homoleptic arylisocyanide tungsten complexes, W(CNXy)_6 and W(CNIph)_6 (Xy = 2,6-dimethylphenyl, Iph = 2,6-diisopropylphenyl), display intense metal to ligand charge transfer (MLCT) absorptions in the visible region (400–550 nm). MLCT emission (λ_max ≈ 580 nm) in tetrahydrofuran (THF) solution at rt is observed for W(CNXy)6 and W(CNIph)_6 with lifetimes of 17 and 73 ns, respectively. Diffusion-controlled energy transfer from electronically excited W(CNIph)_6 (*W) to the lowest energy triplet excited state of anthracene (anth) is the dominant quenching pathway in THF solution. Introduction of tetrabutylammonium hexafluorophosphate, [Bun4N][PF_6], to the THF solution promotes formation of electron transfer (ET) quenching products, [W(CNIph)6]+ and [anth]^•–. ET from *W to benzophenone and cobalticenium also is observed in [Bun4N][PF6]/THF solutions. The estimated reduction potential for the [W(CNIph)6]^(+)/*W couple is −2.8 V vs Cp_(2)Fe^(+/0), establishing W(CNIph)_6 as one of the most powerful photoreductants that has been generated with visible light.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/41065,
title ="Ivano Bertini (1940–2012), Biological Inorganic Chemistry Pioneer, An Obituary-Tribute",
author = "Gray, Harry B. and Banci, Lucia",
journal = "Chemical Educator",
volume = "18",
pages = "209-222",
month = "July",
year = "2013",
doi = "10.1007/s00897132499",
issn = "1430-4171",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130903-140739456",
note = "© 2013 The Chemical Educator.\nPublished: 23 July 2013.",
revision_no = "10",
abstract = "After a four-month battle with lung cancer, Ivano Bertini, Professor of Chemistry and the founder and\nsoul of the Magnetic Resonance Center (CERM) at the Università degli Studi di Firenze, Florence, Italy, where\nhe was scientifically active until the end, died on July 7, 2012. A globally recognized pioneer in the field of\nbiological inorganic chemistry, which he greatly enriched by developing powerful new NMR methods to study\nparamagnetic metalloproteins, he was immensely interested in the role of inorganic chemistry in biology. His\ninfluential 2007 book, Biological Inorganic Chemistry, introduced many young persons to the field. This article,\nco-authored with his closest collaborators, reviews his life, career, contributions, honors, and legacy.",
}
@book_section {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/54276,
title ="Solar Fuels: Approaches to Catalytic Hydrogen Evolution",
author = "Dempsey, J. L. and Winkler, J. R.",
pages = "553-565",
month = "July",
year = "2013",
doi = "10.1016/B978-0-08-097774-4.00806-8",
isbn = "978-0-08-096529-1",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150202-083557905",
note = "© 2013 Elsevier Ltd.\n\nAvailable online 23 July 2013;\nReviewed 26 November 2014.\n\nThis work was supported by NSF Center for Chemical Innovation\n(Powering the Planet, CHE-0947829), the Arnold and\nMabel Beckman Foundation, and CCSER (Gordon and Betty\nMoore Foundation). J.L.D. was supported by an NSF Graduate\nResearch Fellowship.",
revision_no = "13",
abstract = "In response to political and environmental motivations to develop alternative energy resources, researchers have taken a variety of approaches to develop solar energy conversion technologies. Solar fuel production is an area of enormous promise where, in analogy to natural photosynthesis, sunlight drives the conversion of energy-poor molecules (H_2O and CO_2) to energy-rich ones (O_2, H_2, and (CH_2O)_n). To realize a solar-driven water splitting device based on earth-abundant materials, new chemistry is needed, including materials for light harvesting and electrocatalysts for fuel production. In this chapter, we focus on molecular hydrogen production catalysts capable of evolving H_2 at low overpotentials. Recent synthetic advances in catalyst design, detailed electrochemical and photochemical studies, and developments in mechanistic understandings are covered.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/39936,
title ="Kinetics of CO recombination to the heme in Geobacillus stearothermophilus nitric oxide synthase",
author = "Whited, Charlotte A. and Warren, Jeffrey J.",
journal = "Polyhedron",
volume = "58",
pages = "134-138",
month = "July",
year = "2013",
doi = "10.1016/j.poly.2012.08.079 ",
issn = "0277-5387",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130815-084001492",
note = "© 2012 Elsevier Ltd.\n\nAvailable online 21 September 2012.\n\nOur work was supported by NIH (DK019038 to H.B.G. and\nJ.R.W.) and (GM095037 to J.J.W.).",
revision_no = "14",
abstract = "We report the kinetics of CO rebinding to the heme in His134Ser, Ile223Val and His134Ser/Ile223Ser mutants of Geobacillus stearothermophilus nitric oxide synthase (gsNOS). The amplitudes of the two observed kinetics phases, which are insensitive to CO concentration, depend on enzyme concentration. We suggest that two forms of gsNOS are in equilibrium under the conditions employed (6.1–27 μM gsNOS with 20 or 100% CO atmosphere). The kinetics of CO rebinding to the heme do not depend on the identity of the NO-gate residues at positions 134 and 223.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/39170,
title ="Decorating Metal Oxide Surfaces with Fluorescent Chlorosulfonated Corroles",
author = "Blumenfeld, Carl M. and Grubbs, Robert H.",
journal = "Inorganic Chemistry",
volume = "52",
number = "9",
pages = "4774-4776",
month = "May",
year = "2013",
doi = "10.1021/ic400410k",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130701-134750446",
note = "© 2013 American Chemical Society. \n\nReceived: February 16, 2013; published: April 23, 2013. \n\nDue to a production error, this paper was published ASAP on April 23, 2013, with minor errors in the caption for Figure 1. The corrected version was reposted on April 24, 2013. \n\nWe thank the CHLA Radiology Endowment Fund, Sanofi, and Doheny Eye Institute for financial support. We thank Esteban Fernandez, George Rossman, Bruce Brunschwig, Zeev Gross, and Michael Lichterman for their help and discussion on this work. We thank Mona Shahgholi (CCE Division Multiuser Mass Spectrometry Lab at Caltech) for her help with electrospray ionization mass spectrometry experiments.",
revision_no = "15",
abstract = "We have prepared 2,17-bis(chlorosulfonyl)-5,10,15-tris(pentafluorophenyl)corrole (1), 2,17-bis(chlorosulfonyl)-5,10,15-tris(pentafluorophenyl)corrolatoaluminum(III) (1-Al), and 2,17-bis(chlorosulfonyl)-5,10,15-tris(pentafluorophenyl)corrolatogallium(III) (1-Ga). The metal complexes 1-Al and 1-Ga were isolated and characterized by electronic absorption and NMR spectroscopies, as well as by mass spectrometry. Relative emission quantum yields for 1, 1-Al, and 1-Ga, determined in toluene, are 0.094, 0.127, and 0.099, respectively. Reactions between 1, 1-Al, and 1-Ga and TiO2 nanoparticles (NPs) result in corrole–TiO_2 NP conjugates. The functionalized NP surfaces were investigated by solid-state Fourier transform infrared and X-ray photoelectron spectroscopies and by confocal fluorescence imaging. The fluorescence images for 1-Al–TiO_2 and 1-Ga–TiO_2 suggest a promising application of these NP conjugates as contrast agents for noninvasive optical imaging.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/38837,
title ="Electron Transfer Triggered by Optical Excitation of Phenothiazin-tris(meta-phenylene-ethynylene)-(tricarbonyl)(bpy)(py)rhenium(I)",
author = "Bingöl, Bahar and Durrell, Alec C.",
journal = "Journal of Physical Chemistry B",
volume = "117",
number = "16",
pages = "4177-4182",
month = "April",
year = "2013",
doi = "10.1021/jp3010053",
issn = "1520-6106",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130606-115526109",
note = "© 2012 American Chemical Society. \n\nReceived: January 31, 2012; Revised: April 9, 2012; Published: April 25, 2012. \n\nDedicated to the memory of Paul Barbara, a great scientist and dear friend. We thank Tony Vlcek for many helpful discussions and Angelo Di Bilio for assistance with EPR experiments. Supported by a NSF Center for Chemical Innovation grant (Powering the Planet CHE-0802907) and the Arnold and Mabel Beckman Foundation.",
revision_no = "21",
abstract = "We have investigated excited-state electron transfer in a donor-bridge-acceptor complex containing phenothiazine (PTZ) linked via tris(meta-phenylene-ethynylene) to a tricarbonyl(bipyridine)(pyridine)Re(I) unit. Time-resolved luminescence experiments reveal two excited-state (*Re) decay regimes, a multiexponential component with a mean lifetime of 2.7 ns and a longer monoexponential component of 530 ns in dichloromethane solution. The faster decay is attributed to PTZ → *Re electron transfer in a C-shaped PTZ-bridge-Re conformer (PTZ–Re ≈ 7.5 Å). We assign the longer lifetime, which is virtually identical to that of free *Re, to an extended conformer (PTZ–Re > 20 Å). The observed biexponential *Re decay requires that interconversion of PTZ-bridge-Re conformers be slower than 10^6 s^(–1).",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/44491,
title ="Euclidean perspective on the unfolding of azurin: angular correlations",
author = "Warren, Jeffrey J. and Gray, Harry B.",
journal = "Molecular Physics",
volume = "111",
number = "24",
pages = "3762-3769",
month = "April",
year = "2013",
doi = "10.1080/00268976.2013.787153",
issn = "0026-8976",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140325-091200933",
note = "© 2013 Taylor & Francis. Received 29 January 2013; final version received 7 March 2013. Work at Caltech was supported by NIH (GM095037 to JJW, DK019038 to HBG and GM06846l to JRW).",
revision_no = "11",
abstract = "The geometrical model introduced previously by the authors has been extended quantitatively to document changes in angular correlations between and among residues as azurin unfolds. In the early stages of denaturation, these changes are found to be more pronounced than changes in the spatial displacement of residues, a result that is also found for residues acting in concert, viz., α-helices, β-sheet residues and residues in ‘turning regions.’ Our analysis leads to a picture of the large-scale motion of the polypeptide chain as azurin denatures. Flanking a central ‘ribbon’ of residues whose orientation remains essentially invariant, we find that in the early stages of unfolding, left- and right-hand ‘wings’ adjacent to this stationary scaffolding pivot counterclockwise, while smaller regions on opposing ends of the β-barrel pivot clockwise. As spatial constraints characterising the native state are further relaxed, our calculations show that some regions reverse their orientational motion, reflecting the enhanced flexibility of the polypeptide chain in the denatured state.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/38660,
title ="Light-Triggered Modulation of Cellular Electrical Activity by Ruthenium Diimine Nanoswitches",
author = "Rohan, Joyce G. and Citron, Y. Rose",
journal = "ACS Chemical Neuroscience",
volume = "4",
number = "4",
pages = "585-593",
month = "April",
year = "2013",
doi = "10.1021/cn300213f",
issn = "1948-7193",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130523-115225576",
note = "© 2013 American Chemical Society. ACS AuthorChoice. \n\nReceived: November 27, 2012; Accepted: January 18, 2013; Published: February 18, 2013. Published In Issue April 17, 2013. \n\nThe present work was supported by the following funding agencies NSF ERC EEC-0310723 (M.H., R.H.C.), Beckman Initiative for Macular Research Grant 1113 (V.P., R.H.C.), Doheny Eye Institute through the Arnold and Mabel Beckman Foundation (M.H., R.H.G.), NIH RO1 GM85791 (R.H.C.), NIH DK019038 (H.B.G.), and NIH F32GM088967 (J.G.R.). \n\nAuthor Contributions: J.G.R. and Y.R.C. contributed equally to the manuscript. M.H. and R.H.C. designed the study. A.C.D. and L.E.C. synthesized and characterized the ruthenium-diimine compound. J.G.R. and Y.R.C. conducted the electrophysiological and imaging experiments. J.G.R., Y.R.C., and R.H.C. wrote the manuscript. All authors participated in the discussion of data and revision of manusccript. \n\nThe authors declare no competing financial interest.",
revision_no = "18",
abstract = "Ruthenium diimine complexes have previously been used to facilitate light-activated electron transfer in the study of redox metalloproteins. Excitation at 488 nm leads to a photoexcited state, in which the complex can either accept or donate an electron, respectively, in the presence of a soluble sacrificial reductant or oxidant. Here, we describe a novel application of these complexes in mediating light-induced changes in cellular electrical activity. We demonstrate that RubpyC17 ([Ru(bpy)_(2)(bpy-C17)]^(2+), where bpy is 2,2′-bipyridine and bpy-C17 is 2,2′-4-heptadecyl-4′-methyl-bipyridine), readily incorporates into the plasma membrane of cells, as evidenced by membrane-confined luminescence. Excitable cells incubated in RubpyC17 and then illuminated at 488 nm in the presence of the reductant ascorbate undergo membrane depolarization leading to firing of action potentials. In contrast, the same experiment performed with the oxidant ferricyanide, instead of ascorbate, leads to hyperpolarization. These experiments suggest that illumination of membrane-associated RubpyC17 in the presence of ascorbate alters the cell membrane potential by increasing the negative charge on the outer face of the cell membrane capacitor, effectively depolarizing the cell membrane. We rule out two alternative explanations for light-induced membrane potential changes, using patch clamp experiments: (1) light-induced direct interaction of RubpyC17 with ion channels and (2) light-induced membrane perforation. We show that incorporation of RubpyC17 into the plasma membrane of neuroendocrine cells enables light-induced secretion as monitored by amperometry. While the present work is focused on ruthenium diimine complexes, the findings point more generally to broader application of other transition metal complexes to mediate light-induced biological changes.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/37869,
title ="Capturing protein dynamics by time-resolved spectroscopy: Folding and electron tunneling in cytochromes",
author = "Ford, Nicole B. and Yamada, Seiji",
pages = "PHYS-352",
month = "April",
year = "2013",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130410-144330557",
revision_no = "13",
abstract = "We have resolved the folding kinetics of two c-type cytochromes, one that exhibits twostate\nfolding and one that has an on-pathway folding intermediate. We resolve\nmillisecond-timescale folding by coupling time-resolved fluorescence energy transfer\n(FRET) with a continuous flow mixer. The efficiency of energy transfer between a dansyl\nlabel, attached to single-cysteine mutants, and the cytochrome heme during the folding\nprocess provides us with time-dependent distance distributions, which provide information\nabout the kinetics and mechanism of folding.We are also interested in characterizing the\npathway dependence of electron tunneling rates between metal sites in proteins. We have\nconverted a b-type cytochrome to a c-type cytochrome by covalently linking the porphyrin\nto cysteine residues. We investigate the effects of these changes to the protein structure,\ni.e., increased rigidity and potential new equatorial tunneling pathways, on the electron\ntransfer rates, measured via transient absorption, in a series of Ru-modified proteins.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/41512,
title ="A Euclidean perspective on the unfolding of azurin: spatial correlations",
author = "Warren, Jeffrey J. and Gray, Harry B.",
journal = "Molecular Physics",
volume = "111",
number = "7",
pages = "922-929",
month = "April",
year = "2013",
doi = "10.1080/00268976.2012.758324",
issn = "0026-8976",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130924-143326481",
note = "© 2013 Taylor & Francis.\n\nReceived: 23 Sep 2012;\nAccepted: 9 Nov 2012;\nAccepted author version posted online: 14 Dec 2012;\nPublished online: 23 Jan 2013.\n\nWork at Caltech was supported by NIH (GM095037 to JJW,\nDK019038 to HBG and GM068461 to JRW).",
revision_no = "17",
abstract = "We investigate the stability to structural perturbation of Pseudomonas aeruginosa azurin using a previously developed geometric model. Our analysis considers Ru(2,2′,6′,2″-terpyridine)(1,10-phenanthroline)(His83)-labelled wild-type azurin and five variants with mutations to Cu-ligating residues. We find that in the early stages of unfolding, the β-strands exhibit the most structural stability. The conserved residues comprising the hydrophobic core are dislocated only after nearly complete unfolding of the β-barrel. Attachment of the Ru-complex at His83 does not destabilize the protein fold, despite causing some degree of structural rearrangement. Replacing the Cys112 and/or Met121 Cu ligands does not affect the conformational integrity of the protein. Notably, these results are in accord with experimental evidence, as well as molecular dynamics simulations of the denaturation of azurin.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/41851,
title ="Conformational dynamics of a fast folding cytochrome captured by electron transfer, time-resolved fluorescence energy transfer, and microfluidic mixing",
author = "Ford, Nicole B. and Shin, Dong Woo",
pages = "BIOT-146",
month = "April",
year = "2013",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20131010-083823832",
note = "© 2013 American Chemical Society.",
revision_no = "12",
abstract = "Cytochrome c-b_(562) belongs to an interesting family of four-helix bundle cytochromes that have nearly identical structures yet\nwidely divergent folding pathways, creating a unique opportunity to study the relationship between primary sequences and\nfolding in proteins with similar topologies. We characterize the dynamics of cytochrome c-b_(562) through a combination of\nelectron transfer and fluorescence energy transfer (FRET). The dynamics of intrachain diffusion in unfolded cytochromes\nare probed by monitoring contact quenching of a photoexcited, covalently-bound [Ru(bpy)2(IA-phen)]^(2+) dye by the heme Fe^(III).\nQuenching of the *Ru^(II) luminescence decay provides information about the electron transfer rates, which correspond to the\nrates of transient contact formation. We resolve fast folding by coupling time-resolved FRET with an ultrafast continuous flow\nmixer. FRET occurs between a small, covalently-bound dansyl fluorophore and the heme. Fitting the dansyl fluorescence decay\nfollowing picosecond laser excitation provides us with time-dependent dansyl-heme distance distributions during the two-state\nfolding process.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/39380,
title ="Efficient and stable photoelectrochemical energy conversion using p-type WSe2 photocathodes implications",
author = "McKone, James R. and Pieterick, Adam P.",
pages = "INOR 1209",
month = "April",
year = "2013",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130716-081436296",
note = "© 2013 American Chemical Society.",
revision_no = "12",
abstract = "We have synthesized highly cryst. p-type WSe2 and characterized its electrochem. and photoelectrochem. behavior in a variety of\naq. redox couples. Energy conversion efficiencies of > 7% with respect to the thermodn. potential for hydrogen evolution have\nbeen achieved for p-WSe2 photocathodes deposited with a mixed Ru/Pt cocatalyst under 100 mW cm^(-2) white light illumination.\nAddnl., these photocathodes exhibit good stability during photoredn. of Me viologen for at least two hours under illumination at\npH values of 2 and 10. Spectral response measurements suggest that energy conversion efficiencies are limited by short\nminority-carrier diffusion lengths, but impedance spectroscopy indicates that the p-WSe2 band-edge positions are nearly ideal for\nattaining max. photovoltages for the hydrogen evolution reaction.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/39517,
title ="Functionalized corroles as diatherapeutic, multi-modal imaging agents",
author = "Pribisko, Melanie A. and Lim, Punnajit",
pages = "INOR 263",
month = "April",
year = "2013",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130723-085848481",
note = "© 2013 American Chemical Society.",
revision_no = "12",
abstract = "Recent synthetic advancements have made it possible to produce substituted derivs. of meso-5,10,15-(tris)\npentafluorophenylcorrole (H_3tpfc) in reasonable yields. We present the scalable syntheses of new H_3tpfc derivs., and a few of\ntheir metal complexes, through nucleophilic arom. substitution on the pentafluorophenyl substituents. These complexes have\npotential applications both as imaging agents and chemotherapeutic drugs.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/39460,
title ="Making oxygen: Novel catalytic transition metal oxide nanoparticles made by pulsed laser ablation in liquids",
author = "Müller, Astrid M. and Blakemore, James D.",
pages = "INOR 772",
month = "April",
year = "2013",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130719-083843047",
note = "© 2013 American Chemical Society.",
revision_no = "11",
abstract = "Powering the Planet sustainably poses the greatest challenge to humankind. Harvesting solar energy by water splitting will set\nthe stage for clean fuel generation, using Earth-abundant, environmentally friendly transition metal nanomaterial catalysts.We\nuse pulsed laser ablation (PLA) in liqs. to synthesize novel nanomaterials with unique electronic and catalytic properties that are\nstable under anodic conditions, and that exhibit high oxygen-evolution efficiencies. Nanoparticle catalysts exhibit max. surface\narea and introduce addnl. benefits through the modulation of electronic properties as a result of quantum confinement.\nTransition metal oxides are the most promising catalytic materials for electrochem. oxygen evolution from water.We present a\nsystematic study of cobalt oxide and mixed metal oxide nanoparticles made by PLA in water, which we synthesized as a function\nof irradn. intensity and time, with and without additives. We characterized the nanomaterials by absorption spectroscopy, ICPMS,\nXPS, TEM, and voltammetry, and we assessed their oxygen-evolution capability.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/39624,
title ="Mechanistic investigations of cobalt-catalyzed hydrogen evolution",
author = "Marinescu, Smaranda C. and Dempsey, Jillian L.",
pages = "ENFL 665",
month = "April",
year = "2013",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130729-103349212",
note = "© 2013 American Chemical Society.",
revision_no = "11",
abstract = "Natural photosynthesis uses sunlight to drive the conversion of energy-poor mols. (H_2O, CO_2) to energy-rich ones (O_2, CH_2O_n).\nMany scientists are actively engaged in developing efficient artificial photosynthetic systems that split water into H_2 and O_2.\nSolar fuels prodn. involves three basic components: light absorption; charge transport; and multielectron redox catalysis. High\non the list of challenges is the discovery of mols. that efficiently catalyze the redn. of protons to H_2. We have investigated the\nmechanisms of two types of cobalt hydrogen evolution catalysts: Co^(II)-diglyoxime and Co^I-(1,1,1-tris(diphenylphosphinomethyl)\nethane) complexes. Time resolved spectroscopic measurements have provided crit. insights into the kinetics of H_2 prodn. In\nboth cases, protonation of Co^I produces a Co^(III)-H complex. Redn. of Co^(III)-H by Co^I produces a Co^(II)-H transient that reacts\nrapidly with proton donors to produce H_2.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/39433,
title ="Mechanistic studies of fluorinated cobaloximes",
author = "Mercado, Rocio and Rose, Michael J.",
pages = "INOR 873",
month = "April",
year = "2013",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130718-080740331",
note = "© 2013 American Chemical Society.\n",
revision_no = "11",
abstract = "In a previous work, a family of cobalt complexes derived from the fluorinated diphenylglyoxime ligand (\"dAr^FgH_2\") was\nsynthesized. These complexes, [Co(dAr^FgH)_2(py)_2] (1 ) and [Co(dAr^FgH-BF_2)_2(py)_2] (2 ), are variations of the extensively\nstudied diglyoxime systems [Co(dRgBF_2)_2L_2] (R = Me, phenyl), which have been shown to catalyze hydrogen evolution at low\noverpotentials. Like these catalysts, 2 minimizes energy losses by generating hydrogen at negligible thermodn. overpotentials\nin electrocatalysis expts. Through cyclic voltammetry, it was detd. that hydrogen evolution is occurring in protic solns. at the\nsecond redn. potential (-0.88 V vs. Its precursor, 1 , was also characterized and studied as a means of better understanding the\nhydrogen evolution pathway in 2 since both complexes possess a similar electronic structure. This complex exhibits a similar\ncatalytic peak at E = -0.86 V vs. Nevertheless, the two complexes differ in their electrochem. and suggest that the asym.\ncomplex 2 is a better catalyst for hydrogen evolution.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/39393,
title ="Molecular proton-reduction catalysis at silicon semiconductor surfaces",
author = "Blakemore, James D. and Lattimer, Judith R.",
pages = "INOR 1177",
month = "April",
year = "2013",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130716-130435999",
note = "© 2013 American Chemical Society.\n",
revision_no = "14",
abstract = "Driving catalysis at semiconductor:liq. junctions with light enables the efficient conversion and storage of solar energy in chem.\nfuels. Hydrogen evolution from water is one possible path to fuel, as there are known heterogeneous and homogeneous\ncatalysts for proton redn. Homogeneous catalysts show the greatest promise for clarifying both (1) key mechanistic aspects of\nthe hydrogen-evolution reaction at the surface and (2) energetic considerations of the semiconductor band structure. Along this\nline, we are studying a family of rhodium complexes as model catalysts for hydrogen evolution at semiconductor:liq. junctions.\nBoth diffusional and silicon surface-attached systems have been developed, and will be compared. This approach has yielded\nnew information concerning the ambiguities of homogeneous vs. Heterogeneous catalysis, as well as the possible catalytic\nmechanism(s) of the surface-attached species.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/37850,
title ="NSF Center for Chemical Innovation Solar Fuels program",
author = "Gray, Harry B.",
pages = "PRES 9",
month = "April",
year = "2013",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130410-101631371",
note = "© 2013 American Chemical Society.",
revision_no = "11",
abstract = "The NSF Center for Chem. Innovation in Solar Fuels (CCI Solar) focuses on one of the holy\ngrails of 21st century chem. - the efficient and economical conversion of solar energy into\nstored chem. fuel. CCI Solar activities directly impact thousands of students, postdoctoral\nscholars, working scientists, and members of the public at large. Our outreach program\ndelivers Juice-from-Juice solar science activity kits to elementary, middle, and high school\nstudents. Solar Energy Activity Lab kits introduce high school and undergraduate students\nto research involving a combinatorial search for new solar materials. CCI Solar graduate\nstudents and postdoctoral scholars acquire invaluable experience by serving as mentors in\nthese outreach programs. CCI Solar researchers are delivering the message of clean\nrenewable solar fuels in television, radio, and online programs, as well as in public\nlectures, scientific research conferences, and consultations with local, state, and federal\ngovernment officials. The technol., environmental, economic, and social benefits of\nrenewable solar fuels cannot be overstated, as every human being on Earth would be\nimpacted by the development of sustainable energy resources.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/39458,
title ="Pt(pop-BF2) as a photosensitizer in photocatalytic carbon-chlorine bond formation",
author = "Jackson, Megan N. and Ener, Maraia E.",
pages = "INOR 872",
month = "April",
year = "2013",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130719-081932359",
note = "© 2013 American Chemical Society.\n",
revision_no = "11",
abstract = "Palladium complexes perform regioselective C-H functionalizations, which are essential for many syntheses. We are interested in\nhalogenation of C-H bonds using [(benzo[h]quinoline)PdII(μ-OAc)]2 catalysts. Bulk electrolysis expts. show that we can\nchlorinate C-H bonds using chloride and Pd catalysts, eliminating the need for harsh chlorinating agents. To improve the speed\nand energetic cost of C-H transformations we are exploring reactions with photooxidants. Electronically excited fluoroborated\ntetrakis(μ-pyrophosphito)diplatinate(II) (Pt(pop-BF2)) undergoes facile electron transfer reactions. Electrochem. (E°(PtII-PtII/PtIPtII)\n= 1.3 V vs. SCE in MeCN) and fluorescence data were used to calc. E°(*PtII-PtII/PtII-PtI) = 1.4 V vs. SCE, suggesting that\nelectronically excited Pt(pop-BF2) can oxidize Pd catalysts. Absorbance spectra of the transiently reduced Pt complexes were\nrecorded. Time-resolved laser expts. in the presence of Pd catalyst suggest that *Pt(pop-BF2) generates catalytically active Pd\nintermediates, making it a viable sensitizer for photocatalyic C-H functionalizations.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/39372,
title ="Pulsed laser ablation synthesis of nanostructured proton reduction catalysts",
author = "Darnton, Tania V. and Winkler, Jay R.",
pages = "INOR 1389",
month = "April",
year = "2013",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130715-145633172",
note = "© 2013 American Chemical Society.",
revision_no = "14",
abstract = "Emerging global energy demands and the overarching need to reduce fossil fuel consumption have strongly motivated the study\nof artificial photosynthesis in the past decade. One great challenge is to develop systems that efficiently catalyze the redn. of H+\nto H_2. We are investigating the prepn. of catalytic nanoparticles using pulsed laser ablation of solid targets immersed in liqs.\n(PLAL). PLAL generates picoliter reaction vols. of a liq.-confined plasma characterized by extremes of temp., pressure, and atom\nd., permitting exploration of extreme regions of materials phase diagrams. Initial efforts have been directed toward MoS_2, a\nknown proton redn. catalyst. PLAL expts. with a powd. MoS_2 target have produced a nanoparticulate material. Full\ncharacterization of this material, including evaluation of its electrocatalytic H_2 evolution performance, will be presented. Effects\nof laser pulse energy, ablation time, and liq. medium on nanoparticle size, compn., morphol., and proton redn. activity will also\nbe examd.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/39501,
title ="Solar fuels",
author = "Marinescu, Smaranda and Winkler, Jay",
pages = "INOR 623",
month = "April",
year = "2013",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130722-132336387",
note = "© 2013 American Chemical Society.\n",
revision_no = "11",
abstract = "Our NSF funded CCI Solar Fuels Program involves many experimentalists and theorists in an interdisciplinary effort with the goal\nof developing light absorbers and catalysts that could be incorporated in devices to split water to hydrogen and oxygen. Our\nemphasis is on heterogeneous and homogeneous catalysts made from earth-abundant elements that could be part of scalable\nsolar fuel devices. While homogeneous catalysts typically degrade faster than their heterogeneous counterparts, mol. systems\nare much easier to study mechanistically. In recent work on hydrogen evolution from protic solns. catalyzed by a tripodal\nphosphine cobalt complex, we have shown that the dominant reaction channel involves a Co(II)-hydride as the reactive\nintermediate. The lessons we have learned from such mechanistic investigations are guiding the design and construction of very\nactive catalysts both for water redn. and oxidn.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/42175,
title ="Symmetry breaking charge transfer processes of zinc dipyrrin complexes",
author = "Trinh, Cong and Kirlikovali, Kent",
pages = "INOR-176",
month = "April",
year = "2013",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20131101-085854371",
note = "© 2013 American Chemical Society.",
revision_no = "10",
abstract = "Photoinduced charge transfer (CT) via symmetry breaking (SB) processes plays a crucial role in\nphotosynthetic reaction center of biol. systems. In such systems, which contain two or more identical and sym.\nchromophores, CT process from one to another chromophore occurs upon photo-excitation, thus breaking the\nsymmetry. It is of great interest to apply SBCT processes in org. photovoltaics (OPV) and related systems.\nFor application to OPVs, it is desirable for compds. that undergo SB processes to have absorption in the visible\nspectrum. The most well-documented compds. for SB phenomenon, such as bianthryl derivs., do not absorb\nvisible light. Herein we present study on Zinc Dipyrrin complexes, which contain two identical dipyrrin\nligands and absorb strongly at 450-550 nm. These compds. undergo efficient SBCT processes in polar\nsolvents; the photoinduced CT state from the singlet excited state occurs in 4-7 ps, and then recombines back to\nthe triplet state in 1-4 ns.",
}
@book_section {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/37867,
title ="Solar fuels",
author = "Marinescu, Smaranda C. and Bracher, Paul J.",
journal = "AIP Conference Proceedings",
number = "1519",
pages = "64-67",
month = "March",
year = "2013",
doi = "10.1063/1.4794711",
issn = "0094-243X",
isbn = "978-0-7354-1142-5",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130410-140848013",
note = "© 2013 American Institute of Physics.",
revision_no = "27",
abstract = "The generation of hydrogen from water and sunlight may provide the clean, renewable fuel that solves our planet's growing demand for energy. However, for any approach to be practical, we will need to develop robust catalysts containing earthabundant elements for the efficient reduction of protons to H_2 and oxidation of water to O_2.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/38320,
title ="Making Carbon–Chlorine Bonds by Dipalladium Electrocatalysis",
author = "Durrell, Alec C. and Jackson, Megan N.",
journal = "European Journal of Inorganic Chemistry",
volume = "2013",
number = "7",
pages = "1134-1137",
month = "March",
year = "2013",
doi = "10.1002/ejic.201201498",
issn = "1434-1948",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130507-103535110",
note = "© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.\n\nReceived: December 11, 2012; Published Online: January 18, 2013.\n\nThis work was supported by an National Science Foundation\n(NSF) Center for Innovation (CCI Solar, CHE-0802907), the\nAmgen Foundation (M. N. J.), and the Caltech Summer Undergraduate Research Fellowship Program (M. N. J.).",
revision_no = "18",
abstract = "[(Benzo[h]quinolinyl)Pd^(II)(μ-OAc)]_2 and [(2-phenylpyridinyl)PdII(μ-OAc)]_2 undergo one-electron oxidation to afford mixed-valent (Pd^(II)–Pd^(III)) species. Electrochemical oxidation of the Pd^(II)–Pd^(II) complexes in the presence of chloride at the Pd^(III)–Pd^(II)/Pd^(II)–Pd^(II) potential results in a two-electron loss with addition of two chlorides to form [(benzo[h]quinolinyl)Pd^(III)Cl(μ-OAc)]_2 and [(2-phenylpyridinyl)Pd^(III)Cl(μ-OAc)]_2, respectively. When both excess benzo[h]quinoline and chloride are present, [(benzo[h]quinolinyl)Pd^(II)(μ-OAc)]2 electrocatalyzes the chlorination of the substrate to afford 10-chlorobenzo[h]quinoline with high chemical and Faradaic yields.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/37699,
title ="Solar fuels editorial",
author = "Dasgupta, Siddharth and Brunschwig, Bruce S.",
journal = "Chemical Society Reviews",
volume = "42",
number = "6",
pages = "2213-2214",
month = "February",
year = "2013",
doi = "10.1039/c3cs90016a",
issn = "0306-0012",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130401-100227836",
note = "© 2013 The Royal Society of Chemistry.\n\nFirst published on the web 21 Feb 2013.\n\nThis article is part of the collection: Solar fuels",
revision_no = "14",
abstract = "Every major change in the living\nstandards for humans on our planet has\nhad an energy revolution at its heart – the\nadvent of the industrial age with the\nsteam engine and use of coal, the internal\ncombustion engine and large-scale\nelectricity generation. The energy demand,\nprimarily from emerging economies, will\ndouble by 2050. The countervailing\nurgency of the threat of climate change\nrequires a major shift in our energy\nsourcing, creating four new trends that\nwill shape the current century: electrification,\ndecarbonization, localization,\nand optimization.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/37853,
title ="Long-Range Proton-Coupled Electron-Transfer Reactions of Bis(imidazole) Iron Tetraphenylporphyrins Linked to Benzoates",
author = "Warren, Jeffrey J. and Menzeleev, Artur R.",
journal = "Journal of Physical Chemistry Letters",
volume = "4",
number = "3",
pages = "519-523",
month = "February",
year = "2013",
doi = "10.1021/jz400029w",
issn = "1948-7185",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130410-103426798",
note = "© 2013 American Chemical Society.\n\nReceived: January 6, 2013; Accepted: January 14, 2013; Published: January 14, 2013.\n\nOur work was supported by NIH (GM50422 to J.M.M., DK019038\nto H.B.G., and GM095037 to J.J.W.), the NSF (CHE-1057112 to\nT.F.M. and DGE-1144469 to J.S.K.), the DOE (DE-SC0006598 to\nT.F.M.), and the University of Washington (J.J.W. and J.M.M.).\nT.F.M. acknowledges computing support from the National Energy\nResearch Scientific Computing Center (DE-AC02-05CH11231)\nand the Oak Ridge Leadership Computing Facility (DE-AC05-\n00OR22725).",
revision_no = "21",
abstract = "Concerted proton–electron transfer (CPET) reactions in iron carboxytetraphenylporphyrin complexes have been investigated using both experimental and theoretical methods. Synthetic heme models abstract H+ and e– from the hydroxylamine TEMPOH or an ascorbate derivative, and the kinetics of the TEMPOH reaction indicate concerted transfer of H+ and e–. Phenylene linker domains vary the electron donor/acceptor separation by approximately 4 Å. The rate data and extensive molecular simulations show that the electronic coupling decay constant (β) depends on conformational flexibility and solvation associated with the linker domain. Our best estimate of β is 0.23 ± 0.07 Å^(–1), a value that is near the low end of the range (0.2–0.5 Å^(–1)) established for electron-transfer reactions involving related linkers. This is the first analysis of β for a CPET reaction.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/37403,
title ="Ni–Mo Nanopowders for Efficient Electrochemical Hydrogen Evolution",
author = "McKone, James R. and Sadtler, Bryce F.",
journal = "ACS Catalysis",
volume = "3",
number = "2",
pages = "166-169",
month = "February",
year = "2013",
doi = "10.1021/cs300691m",
issn = "2155-5435",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130308-080802822",
note = "© 2012 American Chemical Society. \n\nReceived: October 26, 2012. Revised: November 30, 2012. Published: December 3, 2012. \n\nThis work was supported by the National Science Foundation\n“Powering the Planet” Center for Chemical Innovation (CHE-\n0802907). We thank Carol M. Garland for assistance with\ntransmission electron microscopy. J.R.M. acknowledges the\nDepartment of Energy, Office of Science for a graduate research\nfellowship. C.A.W. thanks the Caltech Summer Undergraduate\nResearch Fellowship (SURF) program for support during the\nsummer of 2012. B.F.S. acknowledges the Beckman Institute\nfor a postdoctoral fellowship.",
revision_no = "18",
abstract = "Earth-abundant metals are attractive alternatives to the noble metal composite catalysts that are used in water electrolyzers based on proton-exchange membrane technology. Ni–Mo alloys have been previously developed for the hydrogen evolution reaction (HER), but synthesis methods to date have been limited to formation of catalyst coatings directly on a substrate. We report a method for generating unsupported nanopowders of Ni–Mo, which can be suspended in common solvents and cast onto arbitrary substrates. The mass-specific catalytic activity under alkaline conditions approaches that of the most active reported non-noble HER catalysts, and the coatings display good stability under alkaline conditions. We have also estimated turnover frequencies per surface atom at various overpotentials and conclude that the activity enhancement for Ni–Mo relative to pure Ni is due to a combination of increased surface area and increased fundamental catalytic activity.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/37120,
title ="Snapshots of a protein folding intermediate",
author = "Yamada, Seiji and Bouley Ford, Nicole D.",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "110",
number = "5",
pages = "1606-1610",
month = "January",
year = "2013",
doi = "10.1073/pnas.1221832110",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130225-151557249",
note = "© 2013 National Academy of Sciences.\nContributed by Harry B. Gray, December 13, 2012 (sent for review May 29, 2012).\nPublished online before print January 14, 2013.\nS.Y. thanks Dr. Julie A. Hoy (Caltech) for X-ray data\ncollection; Dr. Hiroshi Nakajima (Nagoya University) for advice on expression\nand purification of c552; and Drs. Yuichi Tokita and Yoshio Goto (Sony Corporation)\nfor the management, promotion, and kind support of this study.\nS.Y. was supported by a Research Fellowship of Sony Corporation. Research\nat Caltech was supported by National Institutes of Health Grants DK019038\n(to H.B.G. and J.R.W.) and GM068461 (to J.R.W.).\n\n\nAuthor contributions: S.Y., N.D.B.F., H.B.G., and J.R.W. designed research; S.Y. and\nN.D.B.F. performed research; S.Y., N.D.B.F., W.C.F., H.B.G., and J.R.W. analyzed data; and\nS.Y., N.D.B.F., G.E.K., H.B.G., and J.R.W. wrote the paper.",
revision_no = "26",
abstract = "We have investigated the folding dynamics of Thermus thermophilus cytochrome c_(552) by time-resolved fluorescence energy transfer between the heme and each of seven site-specific fluorescent probes. We have found both an equilibrium unfolding intermediate and a distinct refolding intermediate from kinetics studies. Depending on the protein region monitored, we observed either two-state or three-state denaturation transitions. The unfolding intermediate associated with three-state folding exhibited native contacts in β-sheet and C-terminal helix regions. We probed the formation of a refolding intermediate by time-resolved fluorescence energy transfer between residue 110 and the heme using a continuous flow mixer. The intermediate ensemble, a heterogeneous mixture of compact and extended polypeptides, forms in a millisecond, substantially slower than the ∼100-μs formation of a burst-phase intermediate in cytochrome c. The surprising finding is that, unlike for cytochrome c, there is an observable folding intermediate, but no microsecond burst phase in the folding kinetics of the structurally related thermostable protein.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/37122,
title ="Catalysis of Dioxygen Reduction by Thermus thermophilus Strain HB27 Laccase on Ketjen Black Electrodes",
author = "Agbo, Peter and Heath, James R.",
journal = "Journal of Physical Chemistry B",
volume = "117",
number = "2",
pages = "527-534",
month = "January",
year = "2013",
doi = "10.1021/jp309759g ",
issn = "1520-6106",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130225-154105117",
note = "© 2012 American Chemical Society. \n\nReceived: October 2, 2012; Revised: November 7, 2012; Published: November 19, 2012. \n\nWe thank James Mckone, Alec Durrell, and Bryan Stubbert for\nhelpful discussions regarding electrochemistry and Kyle\nLancaster for discussions regarding biochemistry. This research\nwas funded by GCEP (Stanford), CSER (The Gordon and\nBetty Moore Foundation), and NIH (DK019038). Additional\nsupport was provided by a partial fellowship from the Institute\nfor Collaborative Biotechnologies through grant W911NF-09-\n0001 from the U.S. Army Research Office and the Department\nof Energy, Basic Energy Sciences (DE-FG03-01ER46175)(JRH\nPI).",
revision_no = "17",
abstract = "We present electrochemical analyses of the catalysis of dioxygen reduction by Thermus thermophilus strain HB27 laccase on ketjen black substrates. Our cathodes reliably produce 0.56 mA cm^(-2) at 0.0 V vs Ag|AgCl reference at 30 °C in air-saturated buffer, under conditions of nonlimiting O_(2) flux. We report the electrochemical activity of this laccase as a function of temperature, pH, time, and the efficiency of its conversion of dioxygen to water. We have measured the surface concentration of electrochemically active species, permitting the extraction of electron transfer rates at the enzyme-electrode interface: 1 s^(-1) for this process at zero driving force at 30 °C and a limiting rate of 23 s^(-1) at 240 mV overpotential at 50 °C.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/36773,
title ="Hydrogen Evolution from Pt/Ru-Coated p-Type WSe_2 Photocathodes",
author = "McKone, James R. and Peiterick, Adam P.",
journal = "Journal of the American Chemical Society",
volume = "135",
number = "1",
pages = "223-231",
month = "January",
year = "2013",
doi = "10.1021/ja308581g",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130205-103231488",
note = "© 2012 American Chemical Society. \n\nReceived: August 29, 2012; published: November 30, 2012. \n\nThis material is based upon work performed by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under Award Number DE-SC0004993. The contributions from JRM and HBG were supported by CCSER (the Gordon and Betty Moore Foundation). JRM is supported by a graduate research fellowship from the Office of Science of the U.S. Department of Energy.",
revision_no = "14",
abstract = "Crystalline p-type WSe_2 has been grown by a chemical vapor transport method. After deposition of noble metal catalysts, p-WSe_2 photocathodes exhibited thermodynamically based photoelectrode energy-conversion efficiencies of >7% for the hydrogen evolution reaction under mildly acidic conditions, and were stable under cathodic conditions for at least 2 h in acidic as well as in alkaline electrolytes. The open circuit potentials of the photoelectrodes in contact with the H^(+)/H_2 redox couple were very close to the bulk recombination/diffusion limit predicted from the Shockley diode equation. Only crystals with a prevalence of surface step edges exhibited a shift in flat-band potential as the pH was varied. Spectral response data indicated effective minority-carrier diffusion lengths of ~1 μm, which limited the attainable photocurrent densities in the samples to ~15 mA cm^(–2) under 100 mW cm^(–2) of Air Mass 1.5G illumination.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/36741,
title ="Hopping maps for photosynthetic reaction centers",
author = "Warren, Jeffrey J. and Winkler, Jay R.",
journal = "Coordination Chemistry Reviews",
volume = "257",
number = "1",
pages = "165-170",
month = "January",
year = "2013",
doi = "10.1016/j.ccr.2012.07.002 ",
issn = "0010-8545",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130201-110533889",
note = "© 2012 Elsevier B.V. \n\nReceived 16 May 2012; \nReceived in revised form 3 July 2012; Accepted 4 July 2012; \nAvailable online 14 July 2012.\n\n\nOur work is supported by NIH (DK019038 to HBG and JRW;\nGM095037 to JJW), and an NSF Center for Chemical Innovation\n(Powering the Planet, CHE-0947829).",
revision_no = "16",
abstract = "Photosynthetic reaction centers (PRCs) employ multiple-step tunneling (hopping) to separate electrons and holes that ultimately drive the chemistry required for metabolism. We recently developed hopping maps that can be used to interpret the rates and energetics of electron/hole hopping in three-site (donor–intermediate–acceptor) tunneling reactions, including those in PRCs. Here we analyze several key ET reactions in PRCs, including forward ET in the L-branch, and hopping that could involve thermodynamically uphill intermediates in the M-branch, which is ET-inactive in vivo. We also explore charge recombination reactions, which could involve hopping. Our hopping maps support the view that electron flow in PRCs involves strong electronic coupling between cofactors and reorganization energies that are among the lowest in biology (≤0.4 eV).",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/36307,
title ="Photoexcitation of tumor-targeted corroles induces singlet oxygen-mediated augmentation of cytotoxicity",
author = "Hwang, Jae Youn and Lubow, David J.",
journal = "Journal of Controlled Release",
volume = "163",
number = "3",
pages = "368-373",
month = "November",
year = "2012",
doi = "10.1016/j.jconrel.2012.09.015",
issn = "0168-3659",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130110-154703589",
note = "© 2012 Elsevier B.V.\n\nReceived 6 September 2012, Accepted 22 September 2012, Available online 4 October 2012.\n\nThis work was supported by grants from the NIH (R01 CA140995,\nand R01 CA129822). Work at Caltech was supported by NIH\nDK019038 and the Arnold and Mabel Beckman Foundation. Work at\nthe Technion was supported by The Herbert Irving Cancer and Atherosclerosis\nResearch Fund and The United States–Israel Binational\nScience Foundation.\n\n\n\n\n\n",
revision_no = "34",
abstract = "The tumor-targeted corrole particle, HerGa, displays preferential toxicity to tumors in vivo and can be tracked\nvia fluorescence for simultaneous detection, imaging, and treatment. We have recently uncovered an additional\nfeature of HerGa in that its cytotoxicity is enhanced by light irradiation. In the present study, we\nhave elucidated the cellular mechanisms for HerGa photoexcitation-mediated cell damage using fluorescence\noptical imaging. In particular, we found that light irradiation of HerGa produces singlet oxygen, causing mitochondrial damage and cytochrome c release, thus promoting apoptotic cell death. An understanding of the\nmechanisms of cell death induced by HerGa, particularly under conditions of light-mediated excitation, may\ndirect future efforts in further customizing this nanoparticle for additional therapeutic applications and enhanced\npotency.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/36870,
title ="Thermally Stable N_2-Intercalated WO_3 Photoanodes for Water Oxidation",
author = "Mi, Qixi and Ping, Yuan",
journal = "Journal of the American Chemical Society",
volume = "134",
number = "44",
pages = "18318-18324",
month = "November",
year = "2012",
doi = "10.1021/ja3067622 ",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20130212-095922217",
note = "© 2012 American Chemical Society. \n\nReceived: July 14, 2012. Published: September 28, 2012. \n\nWe thank Prof. George R. Rossman for discussions and for assistance with the Raman microscope, and Prof. Francois Gygi for discussions of ab initio calculations. This work was supported by the National Science Foundation (NSF) Powering the Planet Center for Chemical Innovation (CCISolar), Grants CHE-0802907 and CHE-0947829. Q.M. was a CCI-Solar Postdoctoral Fellow. P.G.K. thanks the support of the U.S. Department of Energy under the Hydrogen Fuel Initiative. Research was in part carried out in the Molecular Materials Research Center of the Beckman Institute of the California Institute of Technology, and in part carried out at Brookhaven National Laboratory under No. DE-AC02-98CH10886 with the U.S. Department of Energy. Use of the Teragrid computational facilities is gratefully acknowledged.",
revision_no = "17",
abstract = "We describe stable intercalation compounds of the composition xN_2•WO_3 (x = 0.034–0.039), formed by trapping N_2 in WO_3. The incorporation of N_2 significantly reduced the absorption threshold of WO_3; notably, 0.039N_2•WO_3 anodes exhibited photocurrent under illumination at wavelengths ≤640 nm with a faradaic efficiency for O_2 evolution in 1.0 M HClO_4(aq) of nearly unity. Spectroscopic and computational results indicated that deformation of the WO3 host lattice, as well as weak electronic interactions between trapped N_2 and the WO_3 matrix, contributed to the observed red shift in optical absorption. Noble-gas-intercalated WO_3 materials similar to xN_2•WO_3 are predicted to function as photoanodes that are responsive to visible light.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/35511,
title ="Electron hopping through proteins",
author = "Warren, Jeffrey J. and Ener, Maraia E.",
journal = "Coordination Chemistry Reviews",
volume = "256",
number = "21-22",
pages = "2478-2487",
month = "November",
year = "2012",
doi = "10.1016/j.ccr.2012.03.032",
issn = "0010-8545",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20121116-101610363",
note = "© 2012 Elsevier B.V. \n\nReceived 17 December 2011; Accepted 30 March 2012; Available online 5 April 2012. \n\nOur work is supported by NIH (DK019038 to H.B.G. and J.R.W.;\nGM095037 to J.J.W.), an NSF Center for Chemical Innovation\n(Powering the Planet, CHE-0947829) and by a Czech Ministry of\nEducation Grant ME10124 to A.V. \n\nThis article belongs to a special issue \"Solar Fuels- by invitation only,\" edited By Tony Vlcek.",
revision_no = "20",
abstract = "Biological redox machines require efficient transfer of electrons and holes for function. Reactions involving multiple tunneling steps, termed “hopping,” often promote charge separation within and between proteins that is essential for energy storage and conversion. Here we show how semiclassical electron transfer theory can be extended to include hopping reactions: graphical representations (called hopping maps) of the dependence of calculated two-step reaction rate constants on driving force are employed to account for flow in a rhenium-labeled azurin mutant as well as in two structurally characterized redox enzymes, DNA photolyase and MauG. Analysis of the 35 Å radical propagation in ribonucleotide reductases using hopping maps shows that all tyrosines and tryptophans on the radical pathway likely are involved in function. We suggest that hopping maps can facilitate the design and construction of artificial photosynthetic systems for the production of fuels and other chemicals.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/35514,
title ="Hydrogen-evolution characteristics of Ni–Mo-coated, radial junction, n+p-silicon microwire array photocathodes\n",
author = "Warren, Emily L. and McKone, James R.",
journal = "Energy and Environmental Science",
volume = "5",
number = "11",
pages = "9653-9661",
month = "November",
year = "2012",
doi = "10.1039/C2EE23192A ",
issn = "1754-5692",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20121116-105842933",
note = "© 2012 Royal Society of Chemistry. \n\nReceived 16 August 2012; Accepted 13 September 2012; First published on the web 08 October 2012. \n\nELW and NSL acknowledge support from the Department of\nEnergy (DE-FG02-05ER15754) for Si MW growth and device\nfabrication. JRM and HBG acknowledge support from the\nNational Science Foundation (NSF) Powering the Planet Center\nfor Chemical Innovation (CHE-0802907) for catalyst preparation and characterization. The authors would like to thank Hal Emmer, Dan Turner-Evans, and Elizabeth Santori for help with device fabrication and spectral response data collection. We acknowledge critical support and infrastructure provided for this work by the Kavli Nanoscience Institute at Caltech. JRM would like to thank the Department of Energy, Office of Science, for a graduate research fellowship.",
revision_no = "22",
abstract = "The photocathodic H_2-evolution performance of Ni–Mo-coated radial n+p junction Si microwire (Si MW) arrays has been evaluated on the basis of thermodynamic energy-conversion efficiency as well as solar cell figures of merit. The Ni–Mo-coated n^(+)p-Si MW electrodes yielded open-circuit photovoltages (V_oc) of 0.46 V, short-circuit photocurrent densities (J_sc) of 9.1 mA cm^(−2), and thermodynamically based energy-conversion efficiencies (η) of 1.9% under simulated 1 Sun illumination. Under nominally the same conditions, the efficiency of the Ni–Mo-coated system was comparable to that of Pt-coated n+p-Si MW array photocathodes (V_oc = 0.44 V, J_sc = 13.2 mA cm^(−2_, η = 2.7%). This demonstrates that, at 1 Sun light intensity on high surface area microwire arrays, earth-abundant electrocatalysts can provide performance comparable to noble-metal catalysts for photoelectrochemical hydrogen evolution. The formation of an emitter layer on the microwires yielded significant improvements in the open-circuit voltage of the microwire-array-based photocathodes relative to Si MW arrays that did not have a buried n^(+)p junction. Analysis of the spectral response and light-intensity dependence of these devices allowed for optimization of the catalyst loading and photocurrent density. The microwire arrays were also removed from the substrate to create flexible, hydrogen-evolving membranes that have potential for use in a solar water-splitting device.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/35637,
title ="Inner- and outer-sphere metal coordination in blue copper proteins",
author = "Warren, Jeffrey J. and Lancaster, Kyle M.",
journal = "Journal of Inorganic Biochemistry",
volume = "115",
pages = "119-126",
month = "October",
year = "2012",
doi = " 10.1016/j.jinorgbio.2012.05.002",
issn = "0162-0134",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20121126-112150310",
note = "© 2012 Elsevier Inc. Received 10 March 2012. Received in revised form 30 April 2012. Accepted 1 May 2012. Available online 9 May 2012. Our work is supported by the NIH (DK019038 to HBG) and (GM095037 to JJW). We are grateful to Alejandro Vila for a preprint of reference",
revision_no = "15",
abstract = "Blue copper proteins (BCPs) comprise classic cases of Nature's profound control over the electronic structures and chemical reactivity of transition metal ions. Early studies of BCPs focused on their inner coordination spheres, that is, residues that directly coordinate Cu. Equally important are the electronic and geometric perturbations to these ligands provided by the outer coordination sphere. In this tribute to Hans Freeman, we review investigations that have advanced the understanding of how inner-sphere and outer-sphere coordination affects biological Cu properties.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/33819,
title ="Catalytic hydrogen evolution from a covalently linked dicobaloxime",
author = "Valdez, Carolyn N. and Dempsey, Jillian L.",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "109",
number = "39",
pages = "15589-15593",
month = "September",
year = "2012",
doi = "10.1073/pnas.1118329109",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20120904-101007499",
note = "© 2012 by the National Academy of Sciences. \n\nEdited by Thomas J. Meyer, University of North Carolina at Chapel Hill, Chapel Hill, NC, and approved June 14, 2012 (received for review February 7, 2012). Published online before print July 11, 2012. \n\nWe thank Ian Stewart, Alex Miller, Bryan Stubbert, Charles McCrory, Xile Hu, and Jonas Peters for insightful discussions. This work was supported by the NSF Center for Chemical Innovation (Powering the Planet, CHE-0802907), the Arnold and Mabel Beckman Foundation, CCSER (Gordon and Betty Moore Foundation), and the BP MC2 program. CNV is grateful for support from the Caltech Summer Undergraduate Research Program and an Amgen Scholars Fellowship. JLD was supported by an NSF Graduate Research Fellowship. \n\nAuthor contributions: C.N.V., J.L.D., J.R.W., and H.B.G. designed research; C.N.V. and J.L.D. performed research; C.N.V. and J.L.D. contributed new reagents/analytic tools; C.N.V., J.L.D., and B.S.B. analyzed data; and C.N.V., J.L.D., J.R.W., and H.B.G. wrote the paper. \n\nThe authors declare no conflict of interest. \n\nThis article is a PNAS Direct Submission.",
revision_no = "21",
abstract = "A dicobaloxime in which monomeric Co(III) units are linked by an octamethylene bis(glyoxime) catalyzes the reduction of protons from p-toluenesulfonic acid as evidenced by electrocatalytic waves at -0.4 V vs. the saturated calomel electrode (SCE) in acetonitrile solutions. Rates of hydrogen evolution were determined from catalytic current peak heights (k_(app) = 1100 ± 70 M^(-1) s^(-1)). Electrochemical experiments reveal no significant enhancement in the rate of H2 evolution from that of a monomeric analogue: The experimental rate law is first order in catalyst and acid consistent with previous findings for similar mononuclear cobaloximes. Our work suggests that H_2 evolution likely occurs by protonation of reductively generated Co^(II)H rather than homolysis of two Co^(III)H units.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/35009,
title ="Molecular mechanisms of cobalt-catalyzed hydrogen evolution",
author = "Marinescu, Smaranda C. and Winkler, Jay R.",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "109",
number = "38",
pages = "15127-15131",
month = "September",
year = "2012",
doi = "10.1073/pnas.1213442109",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20121022-125521843",
note = "© 2012 National Academy of Sciences.\n\nContributed by Harry B. Gray, August 6, 2012; sent for review July 19, 2012; Published online before print September 4, 2012.\n\nWe thank Lawrence M. Henling and the late Dr. Michael\nW. Day for crystallographic assistance, and Dr. Jay A. Labinger for insightful comments. Our work is supported by the National Science Foundation Center for Chemical Innovation in Solar Fuels (CHE-0802907); Center for Chemical\nInnovation postdoctoral fellowship to S.C.M. We thank Chevron-Phillips for additional support. The Bruker KAPPA APEX II X-ray diffractometer was purchased via a National Science Foundation Chemistry Research Instrumentation\nand Facilities: Departmental Multi-User Instrumentation (CRIF:MU) award to the California Institute of Technology, CHE-0639094.\n\nAuthor contributions: S.C.M. designed research; S.C.M. performed research; S.C.M.\ncontributed new reagents/analytic tools; S.C.M., J.R.W., and H.B.G. analyzed data; and\nS.C.M., J.R.W., and H.B.G. wrote the paper.\nThe authors declare no conflict of interest.\nData deposition: The atomic coordinates have been deposited in the Cambridge Structural Database, Cambridge Crystallographic Data Centre, Cambridge CB2 1EZ, United\nKingdom http://www.ccdc.cam.ac.uk, [CSD reference numbers 838815 (1), 844589 (2), and 846384 (3)].\n",
revision_no = "27",
abstract = "Several cobalt complexes catalyze the evolution of hydrogen from acidic solutions, both homogeneously and at electrodes. The detailed molecular mechanisms of these transformations remain unresolved, largely owing to the fact that key reactive intermediates have eluded detection. One method of stabilizing reactive intermediates\ninvolves minimizing the overall reaction free-energy\nchange. Here, we report a new cobalt(I) complex that reacts with tosylic acid to evolve hydrogen with a driving force of just 30 meV∕Co. Protonation of Co^I produces a transient Co^(IIII)-H complex that was characterized by nuclear magnetic resonance spectroscopy.\nThe Co^(IIII)-H intermediate decays by second-order kinetics\nwith an inverse dependence on acid concentration. Analysis of the kinetics suggests that Co^(IIII)-H produces hydrogen by two competing pathways: a slower homolytic route involving two Co^(IIII)-H species and a dominant heterolytic channel in which a highly reactive Co^(II)-H transient is generated by Co^I reduction of Co^(IIII)-H.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/34999,
title ="Ivano Bertini 1940–2012",
author = "Gray, Harry Barkus and Banci, Lucia",
journal = "Nature Structural & Molecular Biology",
volume = "19",
number = "9",
pages = "868-869",
month = "September",
year = "2012",
doi = "10.1038/nsmb.2369",
issn = "1545-9985",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20121022-094446939",
note = "© 2012 Nature Publishing Group. Published online 06 September 2012.",
revision_no = "13",
abstract = "Ivano Bertini was one of a kind. You could always tell when he was near, as his booming voice made the walls tremble and everyone within them take notice. He loved life and his friends with a passion that is rarely seen. Finding he had lung cancer, he fought bravely but passed away on 7 July of this year. In his scientific life, he took biological inorganic chemistry to new heights with the development of powerful new NMR methods to study paramagnetic metalloproteins. And, equally importantly to us and to many others, he and his beautiful wife, Renata, were lovable, caring and fiercely loyal friends.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/33960,
title ="Structural Control of ^1A_(2u)-to-^3A_(2u) Intersystem Crossing in Diplatinum(II,II) Complexes",
author = "Durrell, Alec C. and Keller, Gretchen E.",
journal = "Journal of the American Chemical Society",
volume = "134",
number = "34",
pages = "14201-14207",
month = "August",
year = "2012",
doi = "10.1021/ja305666b",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20120910-110255434",
note = "© 2012 American Chemical Society. Received: June 15, 2012. Publication Date (Web): August 6, 2012. We thank Renske van der Veen for interesting discussions. Research at Caltech was supported by the NSF Center for Chemical Innovation (Powering the Planet CHE-0802907 and CHE-0947829) and CSER (Gordon and Betty Moore Foundation). Work at the J. Heyrovský Institute was funded by the Czech Ministry of Education program KONTAKT\n(grant ME10124). ",
revision_no = "18",
abstract = "Analysis of variable-temperature fluorescence quantum yield and lifetime data for per(difluoroboro)tetrakis(pyrophosphito)diplatinate(II) ([Pt_2(μ-P_2O_5(BF_2)_(2)4)]^(4–), abbreviated Pt(pop-BF_2)), yields a radiative decay rate (k_r = 1.7 × 10^8 s^(–1)) an order of magnitude greater than that of the parent complex, Pt(pop). Its temperature-independent and activated intersystem crossing (ISC) pathways are at least 18 and 142 times slower than those of Pt(pop) [ISC activation energies: 2230 cm^(–1) for Pt(pop-BF_2); 1190 cm^(–1) for Pt(pop)]. The slowdown in the temperature-independent ISC channel is attributed to two factors: (1) reduced spin–orbit coupling between the ^1A_(2u) state and the mediating triplet(s), owing to increases of LMCT energies relative to the excited singlet; and (2) diminished access to solvent, which for Pt(pop) facilitates dissipation of the excess energy into solvent vibrational modes. The dramatic increase in E_a is attributed to increased P-O-P framework rigidity, which impedes symmetry-lowering distortions, in particular asymmetric vibrations in the Pt_2(P-O-P)_4 core that would allow direct ^1A_(2u)–^3A_(2u) spin–orbit coupling.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/33552,
title ="Spectroscopic and magnetic properties of an iodo Co^I tripodal phosphine complex",
author = "Rose, Michael J. and Bellone, Donatela E.",
journal = "Dalton Transactions",
volume = "41",
number = "38",
pages = "11788-11797",
month = "August",
year = "2012",
issn = "1477-9226",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20120827-095929289",
note = "© 2012 Royal Society of Chemistry.\n\nReceived 7th June 2012, Accepted 31st July 2012.\nFirst published on the web 20 Aug 2012.\nWe thank Larry Henling and the late Michael Day for X-ray data collection and crystal structure refinement. We gratefully acknowledge Markus Ribbe (UC Irvine) for generous use of a dual mode EPR cavity. Our work was supported by the NSF CCI Solar Fuels program (CHE-0802907) and by CSER (Gordon and Betty Moore Foundation); MJR acknowledges an ACC-F postdoctoral fellowship from the NSF (CHE-1042009). DEB thanks the Rossum family for a SURF award. The Bruker KAPPA APEXII X-ray diffractometer was purchased via an NSF CRIF:MU award to the California Institute of Technology (CHE-0639094).",
revision_no = "18",
abstract = "Reaction of the tripodal phosphine ligand 1,1,1-tris((diphenylphosphino)phenyl)ethane (PhP3) with CoI_2 spontaneously generates a one-electron reduced complex, [(PhP3)Co^(I)(I)] (1). The crystal structure of 1 reveals a distorted tetrahedral environment, with an apical Co–I bond distance of ~2.52 Å. Co^(II/I) redox occurs at an unusually high potential (+0.38 V vs. SCE). The electronic absorption spectrum of 1 exhibits an MLCT peak at 320 nm (ε = 8790 M^(−1) cm^(−1)) and a d–d feature at 850 nm (ε = 840 M^(−1) cm^(−1)). Two more d–d bands are observed in the NIR region, 8650 (ε = 450) and 7950 cm−1 (ε = 430 M−1 cm^(−1)). Temperature dependent magnetic measurements (SQUID) on 1 (solid state, 20–300 K) give μ_eff = 2.99(6) μB, consistent with an S = 1 ground state. Magnetic susceptibilities below 20 K are consistent with a zero field splitting (zfs) |D| = 8 cm^(−1). DFT calculations also support a spin-triplet ground state for 1, as optimized (6-31G*/PW91) geometries (S = 1) closely match the X-ray structure. EPR measurements performed in parallel mode (X-band; 0–15 000 G, 15 K) on polycrystalline 1 or frozen solutions of 1 (THF/toluene) exhibit a feature at g ≈ 4 that arises from a (Δm = 2) transition within the MS = <+1,−1> manifold. Below 10 K, the EPR signal decreases significantly, consistent with a solution zfs parameter (|D| ≈ 8 cm^(−1)) similar to that obtained from SQUID measurements. Our work provides an EPR signature for high-spin Co^I in trigonal ligation.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/33303,
title ="A Multimode Optical Imaging System for Preclinical Applications In Vivo: Technology Development, Multiscale Imaging, and Chemotherapy Assessment",
author = "Hwang, Jae Youn and Wachsmann-Hogiu, Sebastian",
journal = "Molecular Imaging and Biology",
volume = "14",
number = "4",
pages = "431-442",
month = "August",
year = "2012",
doi = "10.1007/s11307-011-0517-z",
issn = "1536-1632",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20120817-134341510",
note = "© 2011 World Molecular Imaging Society.\n\nPublished Online: 27 August 2011.\n\nWe thank Dr. Mark Gaon for help developing and\ntesting the gated anesthesia instrument. Some of this work was done in partial fulfillment of Ph.D. thesis research requirements by Dr. J.Y. Hwang, at the University of Southern California. Work at the California Institute of\nTechnology was supported by the Arnold and Mabel Beckman Foundation. Z.G. thanks Johnson & Johnson for research support. We are grateful for the following federal support of our research: NIH (5R01CA123495-03 and\n1U01CA151815-0) to JYL; NIH (1R01 CA140995 and 1R01 CA129822) and DOD W81XWH-06-1-0549 to LKMK; and US Navy Bureau of Medicine and Surgery (1435-04-04-GT-41387 and -43096), NIH (N01-CO- 07119), and NSF (BESOO 79483) to DLF.\nConflict of Interest. The authors declare they have no conflicts of interest.",
revision_no = "17",
abstract = "Purpose: Several established optical imaging approaches have been applied, usually in isolation, to preclinical studies; however, truly useful in vivo imaging may require a simultaneous combination of imaging modalities to examine dynamic characteristics of cells and tissues. We developed a new multimode optical imaging system designed to be application-versatile, yielding high sensitivity, and specificity molecular imaging. Procedures: We integrated several optical imaging technologies, including fluorescence\nintensity, spectral, lifetime, intravital confocal, two-photon excitation, and bioluminescence, into\na single system that enables functional multiscale imaging in animal models. Results: The approach offers a comprehensive imaging platform for kinetic, quantitative, and environmental analysis of highly relevant information, with micro-to-macroscopic resolution. Applied to small animals in vivo, this provides superior monitoring of processes of interest, represented here by chemo-/nanoconstruct therapy assessment. Conclusions: This new system is versatile and can be optimized for various applications, of which cancer detection and targeted treatment are emphasized here.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/32334,
title ="M–M Bond-Stretching Energy Landscapes for M_2(dimen)_(4)^(2+) (M = Rh, Ir; dimen = 1,8-Diisocyanomenthane) Complexes",
author = "Hunter, Bryan M. and Villahermosa, Randy M.",
journal = "Inorganic Chemistry",
volume = "51",
number = "12",
pages = "6898-6905",
month = "June",
year = "2012",
doi = "10.1021/ic300716q",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20120710-133619920",
note = "© 2012 American Chemical Society.\n\nPublication Date (Web): May 23, 2012.\n\nWe thank Jay Winkler for helpful discussions. Our work was\nsupported by the NSF Center for Chemical Innovation (Grant\nCHE-0802907) and by the David & Lucille Packard\nFoundation Initiative for Interdisciplinary Research. B.M.H. is an NSF Graduate Fellow.",
revision_no = "19",
abstract = "Isomers of Ir_2(dimen)_(4)^(2+) (dimen = 1,8-diisocyanomenthane) exhibit different Ir–Ir bond distances in a 2:1 MTHF/EtCN solution (MTHF = 2-methyltetrahydrofuran). Variable-temperature absorption data suggest that the isomer with the shorter Ir–Ir distance is favored at room temperature [K = ~8; ΔH° = −0.8 kcal/mol; ΔS° = 1.44 cal mol^(–1) K^(–1)]. We report calculations that shed light on M_2(dimen)_(4)^(2+) (M = Rh, Ir) structural differences: (1) metal–metal interaction favors short distances; (2) ligand deformational-strain energy favors long distances; (3) out-of-plane (A_(2u)) distortion promotes twisting of the ligand backbone at short metal–metal separations. Calculated potential-energy surfaces reveal a double minimum for Ir_2(dimen)_(4)^(2+) (4.1 Å Ir–Ir with 0° twist angle and ~3.6 Å Ir–Ir with ±12° twist angle) but not for the rhodium analogue (4.5 Å Rh–Rh with no twisting). Because both the ligand strain and A_(2u) distortional energy are virtually identical for the two complexes, the strength of the metal–metal interaction is the determining factor. On the basis of the magnitude of this interaction, we obtain the following results: (1) a single-minimum (along the Ir–Ir coordinate), harmonic potential-energy surface for the triplet electronic excited state of Ir_2(dimen)_(4)^(2+) (R_(e,Ir–Ir) = 2.87 Å; F_(Ir–Ir) = 0.99 mdyn Å^(–1)); (2) a single-minimum, anharmonic surface for the ground state of Rh_2(dimen)_(4)^(2+) (R_(e,Rh–Rh) = 3.23 Å; F_(Rh–Rh) = 0.09 mdyn Å^(–1)); (3) a double-minimum (along the Ir–Ir coordinate) surface for the ground state of Ir_2(dimen)_(4)^(2+) (R_(e,Ir–Ir) = 3.23 Å; F_(Ir–Ir) = 0.16 mdyn Å^(–1)).",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/31996,
title ="Hydrogen Generation Catalyzed by Fluorinated Diglyoxime−Iron\nComplexes at Low Overpotentials",
author = "Rose, Michael J. and Gray, Harry B.",
journal = "Journal of the American Chemical Society",
volume = "134",
number = "20",
pages = "8310-8313",
month = "May",
year = "2012",
doi = "10.1021/ja300534r",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20120621-073446298",
note = "© 2012 American Chemical Society. Received: January 17, 2012. Publication Date (Web): May 14, 2012. This work was supported by the NSF CCI Solar Fuels Program (CHE-0802907). M.J.R. was supported by an NSF ACC-F Fellowship (CHE-1042009). The Bruker APEXII diffractometer\nwas obtained via an NSF CRIF:MU Award (CHE-0639094). We thank Larry Henling and Michael Day for solving the crystal structures. ",
revision_no = "25",
abstract = "Fe^(II) complexes containing the fluorinated ligand 1,2-bis(perfluorophenyl)ethane-1,2-dionedioxime (dAr^FgH_2; H = dissociable proton) exhibit relatively positive Fe^(II/I) reduction potentials. The air-stable difluoroborated species [(dAr^FgBF_2)_2Fe(py)_2] (2) electrocatalyzes H_2 generation at −0.9 V vs SCE with i_(cat)/i_p ≈ 4, corresponding to a turnover frequency (TOF) of ~ 20 s^(–1) [Faradaic yield (FY) = 82 ± 13%]. The corresponding monofluoroborated, proton-bridged complex [(dArFg2H-BF2)Fe(py)2] (3) exhibits an improved TOF of ~ 200 s^(–1) (i_(cat)/i_p ≈ 8; FY = 68 ± 14%) at −0.8 V with an overpotential of 300 mV. Simulations of the electrocatalytic cyclic voltammograms of 2 suggest rate-limiting protonation of an Fe“0” intermediate (k_(RLS) ≈ 200 M^(–1) s^(–1)) that undergoes hydride protonation to form H_2. Complex 3 likely reacts via protonation of an Fe^I intermediate that subsequently forms H_2 via a bimetallic mechanism (k_(RLS) ≈ 2000 M^(–1) s^(–1)). 3 catalyzes production at relatively positive potentials compared with other iron complexes.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/31876,
title ="Outer-Sphere Contributions to the Electronic Structure of Type Zero Copper Proteins",
author = "Lancaster, Kyle M. and Zaballa, María-Eugenia",
journal = "Journal of the American Chemical Society",
volume = "134",
number = "19",
pages = "8241-8253",
month = "May",
year = "2012",
doi = "10.1021/ja302190r",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20120611-154824690",
note = "© 2012 American Chemical Society. \n\nReceived: March 13, 2012; Published: May 7, 2012. \n\nWe thank Eckhard Bill and Andreas Göbels for assistance with MCD data collection. The NMR spectrometer in Rosario was \npurchased with funds from ANPCyT and CONICET. A.J.V.\nthanks ANPCyT for funding (PICT 2007-0314). A.J.V. is staff\nmember of CONICET and an HHMI International Scholar,\nand M.E.Z. is recipient of a doctoral fellowship from\nCONICET. M.S. was supported by Alexander von Humboldt\nand K.S. Krishnan Research Associateship fellowships for\nfunding. Financial support of this work by the SFB 624\n(‘Template Effects’) and the Max-Planck-Society is also\ngratefully acknowledged. K.M.L., J.H.R., and H.B.G. were\nsupported by NIH DK019038 and Stanford GCEP.",
revision_no = "32",
abstract = "Bioinorganic canon states that active-site\nthiolate coordination promotes rapid electron transfer (ET)\nto and from type 1 copper proteins. In recent work, we have\nfound that copper ET sites in proteins also can be constructed\nwithout thiolate ligation (called “type zero” sites). Here we\nreport multifrequency electron paramagnetic resonance\n(EPR), magnetic circular dichroism (MCD), and nuclear\nmagnetic resonance (NMR) spectroscopic data together with\ndensity functional theory (DFT) and spectroscopy-oriented\nconfiguration interaction (SORCI) calculations for type zero Pseudomonas aeruginosa azurin variants. Wild-type (type 1) and type\nzero copper centers experience virtually identical ligand fields. Moreover, O-donor covalency is enhanced in type zero centers\nrelative that in the C112D (type 2) protein. At the same time, N-donor covalency is reduced in a similar fashion to type 1\ncenters. QM/MM and SORCI calculations show that the electronic structures of type zero and type 2 are intimately linked to the\norientation and coordination mode of the carboxylate ligand, which in turn is influenced by outer-sphere hydrogen bonding.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/31693,
title ="Groups 5 and 6 Terminal Hydrazido(2−) Complexes: N_β Substituent Effects on Ligand-to-Metal Charge-Transfer Energies and Oxidation States",
author = "Tonks, Ian A. and Durrell, Alec C.",
journal = "Journal of the American Chemical Society",
volume = "134",
number = "17",
pages = "7301-7304",
month = "May",
year = "2012",
doi = "10.1021/ja302275j",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20120530-084227048",
note = "© 2012 American Chemical Society. Received: March 7, 2012. Publication Date (Web): April 16, 2012. We thank Lawrence Henling and Dr. Michael Day for assistance with the X-ray studies. The Bruker KAPPA APEXII X-ray diffractometer was purchased via an NSF CRIF:MU Award (CHE-0639094) to the California Institute of Technology. This work was supported by the U.S. DOE Office of Basic Energy Sciences (DE-FG03-85ER13431 to J.E.B.). Photophysics investigations were supported by an NSF Center for Chemical Innovation Grant (CHE-0802907 to H.B.G.).",
revision_no = "25",
abstract = "Brightly colored terminal hydrazido(2−) (dme)MCl_3(NNR_2) (dme = 1,2-dimethoxyethane; M = Nb, Ta; R = alkyl, aryl) or (MeCN)WCl_4(NNR_2) complexes have been synthesized and characterized. Perturbing the electronic environment of the β (NR_2) nitrogen affects the energy of the lowest-energy charge-transfer (CT) transition in these complexes. For group 5 complexes, increasing the energy of the N_β lone pair decreases the ligand-to-metal CT (LMCT) energy, except for electron-rich niobium dialkylhydrazides, which pyramidalize N_β in order to reduce the overlap between the Nb═Nα π bond and the Nβ lone pair. For W complexes, increasing the energy of N_β eventually leads to reduction from formally [W^(VI)≡N–NR_2] with a hydrazido(2−) ligand to [W^(IV)═N═NR_2] with a neutral 1,1-diazene ligand. The photophysical properties of these complexes highlight the potential redox noninnocence of hydrazido ligands, which could lead to ligand- and/or metal-based redox chemistry in early transition metal derivatives.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/35492,
title ="A novel ruthenium(II)–cobaloxime supramolecular complex for photocatalytic H_2 evolution: synthesis, characterisation and mechanistic studies",
author = "Cropek, Donald M. and Metz, Anja",
journal = "Dalton Transactions",
volume = "41",
number = "42",
pages = "13060-13073",
month = "April",
year = "2012",
doi = "10.1039/C2DT30309D ",
issn = "1477-9226",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20121115-133308631",
note = "© 2012 Royal Society of Chemistry.\n\nReceived 10th February 2012, Accepted 2nd April 2012.\nFirst published on the web 11 Apr 2012.\nThis research was supported in part by an appointment to the\nStudent Research Participation Program at the U.S. Army Engineer Research and Development Center, Construction Engineering Research Laboratory, administered by the Oak Ridge Institute for Science and Education through an interagency agreement between the U.S. Department of Energy and ERDC-CERL. This work was also supported by the Center Directed Research Program at the U.S. Army Corps of Engineers, the Arnold and Mabel Beckman Foundation, The Mississippi LSAMP (grant #HRD-0602740), and by the Mississippi INBRE funded by grants from the National Center for Research Resources (5P20RR016476-11) and the National Institute of General Medical Sciences (8 P20 GM103476-11) from the National Institutes of Health. The authors also acknowledge the National Science Foundation (NSF) for funding our ESI and MALDI-ToF mass spectrometers (Grant CHE 0639208). We are also grateful for the use of our BrukerBiospin EMXmicro ESR spectrometer, which was funded by the NSF CRIF:MU Award #0741991; also our new 400 MHZ NMR spectrometer, which was funded by the NSF CRIF:MU Award #0840390. AAH would like to thank the NSF for an NSF CAREER Award; also this material is based upon work supported by the NSF under CHE - 1151832. The authors would like to acknowledge the scientists at Olis, Inc. for acquiring all of the NIR spectra on their Olis-modernized Cary\n14 UV/Vis/NIR spectrophotometer. We also acknowledge Dr Aimin Liu and Ms. Fange Liu of Georgia State University for their assistance in acquiring two ESR spectra for us in liquid helium. D.C.H. and T.H. would like to thank Dr Karen Mulfort of Argonne National Laboratory (ANL) for her assistance during their summer research stint in summer 2009 at ANL.",
revision_no = "40",
abstract = "We report the synthesis and characterization of novel mixed-metal binuclear ruthenium(II)–cobalt(II) photocatalysts for hydrogen evolution in acidic acetonitrile. First, 2-(2′-pyridyl)benzothiazole (pbt), 1, was reacted with RuCl_(3)·xH_(2)O to produce [Ru(pbt)_(2)Cl_2]·0.25CH_(3)COCH_3, 2, which was then reacted with 1,10-phenanthroline-5,6-dione (phendione), 3, in order to produce [Ru(pbt)_(2)(phendione)](PF_(6))_2·4H_(2)O, 4. Compound 4 was then reacted with 4-pyridinecarboxaldehyde in order to produce [Ru(pbt)_(2)(L-pyr)](PF_6)_(2)·9.5H_(2)O, 5 (where L-pyr = (4-pyridine)oxazolo[4,5-f]phenanthroline). Compound 5 was then reacted with [Co(dmgBF_2)_(2)(H_(2)O)_2] (where dmgBF_(2) = difluoroboryldimethylglyoximato) in order to produce the mixed-metal binuclear complex, [Ru(pbt)_(2)(L-pyr)Co(dmgBF_(2))_(2)(H_(2)O)](PF_(6))_2·11H_(2)O·1.5CH_(3)COCH_3, 6. [Ru(Me_(2)bpy)_2(L-pyr)Co(dmgBF_2)_(2)(OH_2)](PF_6)_(2), 7 (where Me_(2)bpy = 1,10-phenanthroline, 4,4′-dimethyl-2,2′-bipyridine) and [Ru(phen)_(2)(L-pyr)Co(dmgBF_2)_(2)(OH_2)](PF_(6))_2, 8 were also synthesised. All complexes were characterized by elemental analysis, ESI MS, HRMS, UV-visible absorption, ^(11)B, ^(19)F, and ^(59)Co NMR, ESR spectroscopy, and cyclic voltammetry, where appropriate. Photocatalytic studies carried out in acidified acetonitrile demonstrated constant hydrogen generation longer than a 42 hour period as detected by gas chromatography. Time resolved spectroscopic measurements were performed on compound 6, which proved an intramolecular electron transfer from an excited Ru(II) metal centre to the Co(II) metal centre via the bridging L-pyr ligand. This resulted in the formation of a cobalt(I)-containing species that is essential for the production of H_2 gas in the presence of H^+ ions. A proposed mechanism for the generation of hydrogen is presented.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/31487,
title ="Spin Delocalization Over Type Zero Copper",
author = "Potapov, Alexey and Lancaster, Kyle M.",
journal = "Inorganic Chemistry",
volume = "51",
number = "7",
pages = "4066-4075",
month = "April",
year = "2012",
doi = "10.1021/ic202336m",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20120515-154220333",
note = "© 2012 American Chemical Society. Received: October 28, 2011.\nPublication Date (Web): March 20, 2012. Notes: The authors declare no competing financial interest. This work was supported by U.S.−Israel Binational Science Foundation (2006179) (D.G.) and was made possible in part by the historic generosity of the Harold Perlman Family (D.G.). D.G. holds the Erich Klieger Professorial Chair in Chemical Physics. Work at Caltech was supported by NIH DK019038.",
revision_no = "29",
abstract = "Hard-ligand, high-potential copper sites have been characterized in double mutants of Pseudomonas aeruginosa azurin (C112D/M121X (X = L, F, I)). These sites feature a small A_(zz)(Cu) splitting in the EPR spectrum together with enhanced electron transfer activity. Due to these unique properties, these constructs have been called “type zero” copper sites. In contrast, the single mutant, C112D, features a large A_(zz)(Cu) value characteristic of the typical type 2 Cu^(II). In general, A_(zz)(Cu) comprises contributions from Fermi contact, spin dipolar, and orbital dipolar terms. In order to understand the origin of the low A_(zz)(Cu) value of type zero Cu^(II), we explored in detail its degree of covalency, as manifested by spin delocalization over its ligands, which affects A_(zz)(Cu) through the Fermi contact and spin dipolar contributions. This was achieved by the application of several complementary EPR hyperfine spectroscopic techniques at X- and W-band (~9.5 and 95 GHz, respectively) frequencies to map the ligand hyperfine couplings. Our results show that spin delocalization over the ligands in type zero Cu^(II) is different from that of type 2 Cu^(II) in the single C112D mutant. The ^(14)N hyperfine couplings of the coordinated histidine nitrogens are smaller by about 25–40%, whereas that of the ^(13)C carboxylate of D112 is about 50% larger. From this comparison, we concluded that the spin delocalization of type zero copper over its ligands is not dramatically larger than in type 2 C112D. Therefore, the reduced A_(zz)(Cu) value of type zero Cu^(II) is largely attributable to an increased orbital dipolar contribution that is related to its larger g_(zz) value, as a consequence of the distorted tetrahedral geometry. The increased spin delocalization over the D112 carboxylate in type zero mutants compared to type 2 C112D suggests that electron transfer paths involving this residue are enhanced.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/31447,
title ="Signatures of unfolding in the early stages of protein denaturation",
author = "Gray, Harry B. and Winkler, Jay R.",
journal = "Molecular Physics",
volume = "110",
number = "7",
pages = "419-429",
month = "April",
year = "2012",
doi = "10.1080/00268976.2011.651168",
issn = "0026-8976",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20120514-102559323",
note = "© 2012 Taylor & Francis. Received 30 September 2011; final version received 14 December 2011. Available online: 11 Apr 2012. \n",
revision_no = "12",
abstract = "A comparative study of the early stages of unfolding of five proteins: cyt c, c-b_(562), cyt c′, azurin, and lysozyme is reported. From crystallographic data, helical regions and intervening non-helical (or ‘turning’) regions are identified in each. Exploiting a previously introduced geometrical model, the paper describes quantitatively the stepwise extension of a polypeptide chain subject to the geometrical constraint that the spatial relationship among the residues of each triplet is fixed by native-state crystallographic data. Despite differences among the above-cited proteins, remarkable universality of behavior is found in the early stages of unfolding. At the very earliest stages, internal residues in each helical region have a common unfolding history; the terminal residues, however, are extraordinarily sensitive to structural perturbations. Residues in non-helical sections of the polypeptide unfold after residues in the internal helical regions, but with increasing steric perturbation playing a dominant role in advancing denaturation.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/29977,
title ="Redox properties of tyrosine and related molecules",
author = "Warren, Jeffrey J. and Winkler, Jay R.",
journal = "FEBS Letters",
volume = "586",
number = "5",
pages = "596-602",
month = "March",
year = "2012",
doi = "10.1016/j.febslet.2011.12.014",
issn = "0014-5793",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20120404-105819558",
note = "© 2011 Federation of European Biochemical Societies. \n\nPublished by Elsevier B.V. All rights reserved. Received 10 October 2011. Revised 4 December 2011. Accepted 12 December 2011. Available online 26 December 2011. Edited by Miguel Teixeira and Ricardo O. Louro. \n\nDedicated to the memory of Antonio Xavier, an outstanding scientist and dear friend. We thank Seiji Yamada, Julie Hoy and Jens Kaiser for assistance \nwith X-ray structure determination. Our work is supported by NIH (DK019038 to H.B.G. and J.R.W.; GM095037 to J.J.W.). The Gordon and Betty Moore Foundation supports the Molecular Observatory at Caltech, and NIH and DOE support operation of the Stanford Synchrotron Radiation Laboratory (SSRL) beamline 12-2.",
revision_no = "19",
abstract = "Redox reactions of tyrosine play key roles in many biological processes, including water oxidation and DNA synthesis. We first review the redox properties of tyrosine (and other phenols) in small molecules and related polypeptides, then report work on (H20)/(Y48)-modified Pseudomonas aeruginosa azurin. The crystal structure of this protein (1.18 Å resolution) shows that H20 is strongly hydrogen bonded to Y48 (2.7–2.8 Å tyrosine-O to histidine-N distance). A firm conclusion is that proper tuning of the tyrosine potential by a proton-accepting base is critical for biological redox functions.\n",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/30235,
title ="Fe_4 Cluster and a Buckled Macrocycle Complex from the Reduction of [(dmgBF_2)_(2)Fe(L)_2] (L = MeCN, ^(t)Bu^(i)NC)",
author = "Rose, Michael J. and Winkler, Jay R.",
journal = "Inorganic Chemistry",
volume = "51",
number = "4",
pages = "1980-1982",
month = "February",
year = "2012",
doi = "10.1021/ic202253v",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20120420-132701817",
note = "© 2012 American Chemical Society.\n\nReceived: October 19, 2011; Published: February 9, 2012.\n\nThe authors thank Larry Henling and Michael Day for X-ray\nstructures and Angelo Di Bilio for assistance with EPR spectra.\nWe acknowledge Allen Oliver (University of Notre Dame) and\nJeannette Krause (University of Cincinati) for X-ray data\ncollection on 3 via the SCrALS program at Beamline 11.3.1,\nAdvanced Light Source (LBNL), supported by the U.S. DOE,\nEnergy Material Sciences Division. The Bruker KAPPA APEX\nII was purchased via an NSF CRIF:MU. The authors thank\nNicole Fry for obtaining magnetic susceptibility data on 4.\nFunding sources: NSF Grant CHE-0802907 (to M.J.R., J.R.W.,\nand H.B.G.); NSF Grant CHE-1042009 (to M.J.R.); Grant\nDOE-AC02-05CH11231 (synchrotron X-ray structure); NSF\nGrant CHE-0639094 (Mo Kα X-ray structures).",
revision_no = "29",
abstract = "We report the syntheses, X-ray structures, and reductive electrochemistry of the Fe^(II) complexes [(dmgBF_2)_(2)Fe(MeCN)_2] (1; dmg = dimethylglyoxime, MeCN = acetonitrile) and [(dmgBF_2)Fe(^(t)Bu^(i)NC)_2] (2; ^(t)Bu^(i)NC = tert-butylisocyanide). The reaction of 1 with Na/Hg amalgam led to isolation and the X-ray structure of [(dmgBF_2)_(2)Fe(glyIm)] (3; glyIm = glyimine), wherein the (dmgBF_2)_2 macrocyclic frame is bent to accommodate the binding of a bidentate apical ligand. We also report the X-ray structure of a rare mixed-valence Fe4 cluster with supporting dmg-type ligands. In the structure of [(dmg_(2)BF_2)_(3)Fe_3(1/2dmg)_(3)Fe(O)_6] (4), the (dmgBF_(2))_2 macrocycle has been cleaved, eliminating BF_2 groups. Density functional theory calculations and electron paramagnetic resonance data are in accordance with a central FeIII ion surrounded by three formally Fe^(II)dmg_(2)BF_2 units.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/29496,
title ="A quantitative assessment of the competition between water and anion oxidation at WO_3 photoanodes in acidic aqueous electrolytes",
author = "Mi, Qixi and Zhanaidarova, Almagul",
journal = "Energy and Environmental Science",
volume = "5",
number = "2",
pages = "5694-5700",
month = "February",
year = "2012",
doi = "10.1039/c2ee02929d",
issn = "1754-5692",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20120228-074506627",
note = "© 2012 The Royal Society of Chemistry. \n\nReceived 19th October 2011, Accepted 7th December 2011. First published on the web 03 Jan 2012. \n\nWe acknowledge the National Science Foundation (NSF) Powering the Planet Center for Chemical Innovation (CCI-Solar), Grants CHE-0802907 and CHE-0947829, and the Molecular Materials Research Center of the Beckman Institute at the California Institute of Technology, for support. QM also acknowledges the NSF for support as a CCI-Solar Postdoctoral Fellow.",
revision_no = "16",
abstract = "The faradaic efficiency for O_2(g) evolution at thin-film WO_3 photoanodes has been evaluated in a series of acidic aqueous electrolytes. In 1.0 M H_2SO_4, persulfate was the predominant photoelectrochemical oxidation product, and no O_2 was detected unless catalytic quantities of Ag^+(aq) were added to the electrolyte. In contact with 1.0 M HClO_4, dissolved O_2 was observed with nearly unity faradaic efficiency, but addition of a hole scavenger, 4-cyanopyridine N-oxide, completely suppressed O_2 formation. In 1.0 M HCl, Cl_2(g) was the primary oxidation product. These results indicate that at WO_3 photoanodes, water oxidation is dominated by oxidation of the acid anions in 1.0 M HCl, H_2SO_4, and HClO_4, respectively.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/29820,
title ="Differential Cytostatic and Cytotoxic Action of Metallocorroles against Human Cancer Cells: Potential Platforms for Anticancer Drug Development",
author = "Lim, Punnajit and Mahammed, Atif",
journal = "Chemical Research in Toxicology",
volume = "25",
number = "2",
pages = "400-409",
month = "February",
year = "2012",
issn = "0893-228X",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20120323-091012038",
note = "© 2011 American Chemical Society. Received: October 18, 2011. \nPublication Date (Web): December 20, 2011. The technical assistance of Dr. Richard Yip and Charlie Hsin of\nthe High Throughput Screening and Dr. Brian Armstrong of\nthe Light Microscopy Digital Imaging Core Facilities of the\nCity of Hope Comprehensive Cancer Center is gratefully\nacknowledged. This work was supported by Caltech-City of Hope Biomedical Research Initiative and the U.S. Army RDECOM Acquisition Center, Natick Contracting Division, Natick, MA, under\nContract no. W911QY-10-C-0176",
revision_no = "25",
abstract = "A gallium(III)-substituted amphiphilic corrole noncovalently associated with a targeting protein was previously found by us to confer promising cytotoxic and antitumor activities against a breast cancer cell line and a mouse xenograft breast cancer model. To further explore potential anticancer applications, the cytostatic and cytotoxic properties of six nontargeted metallocorroles were evaluated against seven human cancer cell lines. Results indicated that toxicity toward human cancer cells depended on the metal ion as well as corrole functional group substitution. Ga(III)-substituted metallocorrole 1-Ga inhibited proliferation of breast (MDA-MB-231), melanoma (SK-MEL-28), and ovarian (OVCAR-3) cancer cells primarily by arrest of DNA replication, whereas 2-Mn displayed both cytostatic and cytotoxic properties. Confocal microscopy revealed extensive uptake of 1-Ga into the cytoplasm of melanoma and ovarian cancer cells, while prostate cancer cells (DU-145) displayed extensive nuclear localization. The localization of 1-Ga to the nucleus in DU-145 cells was exploited to achieve a 3-fold enhancement in the IC_(50) of doxorubicin upon coadministration. Time–course studies showed that over 90% of melanoma cells incubated with 30 μM 1-Ga internalized metallocorrole after 15 min. Cellular uptake of 1-Ga and 1-Al was fastest and most efficient in melanoma, followed by prostate and ovarian cancer cells. Cell cycle analyses revealed that bis-sulfonated corroles containing Al(III), Ga(III), and Mn(III) induced late M phase arrest in several different cancer cell lines, a feature that could be developed for potential therapeutic benefit.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/29957,
title ="Gating NO Release from Nitric Oxide Synthase",
author = "Whited, Charlotte A. and Warren, Jeffrey J.",
journal = "Journal of the American Chemical Society",
volume = "134",
number = "1",
pages = "27-30",
month = "January",
year = "2012",
doi = "10.1021/ja2069533",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20120403-112410644",
note = "© 2011 American Chemical Society. Received: July 29, 2011. Publication Date (Web): December 7, 2011. C.A.W. thanks Michael Winter for valuable discussions and Dr. Josh Woodward for a spectrum of ferric-NO NOS. Supported by an NSF graduate fellowship (C.A.W.), the NIH (DK019038 to H.B.G. and J.R.W.; GM068461 to J.R.W.; GM095037 postdoctoral fellowship to J.J.W.), and the Arnold and Mabel Beckman Foundation.",
revision_no = "30",
abstract = "We have investigated the kinetics of NO escape from Geobacillus stearothermophilus nitric oxide synthase (gsNOS). Previous work indicated that NO release was gated at position 223 in mammalian enzymes; our kinetics experiments include mutants at that position along with measurements on the wild type enzyme. Employing stopped-flow UV–vis methods, reactions were triggered by mixing a reduced enzyme/N-hydroxy-l-arginine complex with an aerated buffer solution. NO release kinetics were obtained for wt NOS and three mutants (H134S, I223V, H134S/I223V). We have confirmed that wt gsNOS has the lowest NO release rate of known NOS enzymes, whether bacterial or mammalian. We also have found that steric clashes at positions 223 and 134 hinder NO escape, as judged by enhanced rates in the single mutants. The empirical rate of NO release from the gsNOS double mutant (H134/I223V) is nearly as rapid as that of the fastest mammalian enzymes, demonstrating that both positions 223 and 134 function as gates for escape of the product diatomic molecule.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/30069,
title ="Investigating photoexcitation-induced mitochondrial damage by chemotherapeutic corroles using multimode optical imaging",
author = "Hwang, Jae Youn and Farkas, Daniel L.",
journal = "Journal of Biomedical Optics",
volume = "17",
number = "1",
pages = "Art. No. 015003",
month = "January",
year = "2012",
doi = "10.1117/1.JBO.17.1.015003 ",
issn = "1083-3668",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20120412-133338394",
note = "© 2012 SPIE.\n\nPaper 11395P received Jul. 22, 2011; revised manuscript received Nov. 7, 2011; accepted for publication Nov. 8, 2011; published online\nFeb. 6, 2012.\n\nWe thank Kevin Burton (Cedars-Sinai Medical Center) for providing\nvaluable comments. This work was supported by grants\nfrom the U.S. Navy Bureau of Medicine and Surgery, the NIH\n(R21 CA116014, R01 CA140995, and R01 CA129822), the\nDoD (BC050662), the Susan G. Komen Breast Cancer foundation\n(BCTR0201194), and the Donna and Jesse Garber Award.\nWork at Caltech was supported by NIH DK019038 and the\nArnold and Mabel Beckman Foundation. Work at the Technion\nwas supported by The Herbert Irving Cancer and Atherosclerosis\nResearch Fund and The United States-Israel Binational\nScience Foundation.",
revision_no = "15",
abstract = "We recently reported that a targeted, brightly fluorescent gallium corrole (HerGa) is highly effective for breast tumor detection and treatment. Unlike structurally similar porphryins, HerGa exhibits tumor-targeted toxicity without the need for photoexcitation. We have now examined whether photoexcitation further modulates HerGa toxicity, using multimode optical imaging of live cells, including two-photon excited fluorescence, differential interference contrast (DIC), spectral, and lifetime imaging. Using two-photon excited fluorescence imaging, we observed that light at specific wavelengths augments the HerGa-mediated mitochondrial membrane potential disruption of breast cancer cells in situ. In addition, DIC, spectral, and fluorescence lifetime imaging enabled us to both validate cell damage by HerGa photoexcitation and investigate HerGa internalization, thus allowing optimization of light dose and timing. Our demonstration of HerGa phototoxicity opens the way for development of new methods of cancer intervention using tumor-targeted corroles.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/29120,
title ="A Mechanistic Study of Tumor-Targeted Corrole Toxicity",
author = "Hwang, Jae Youn and Lubow, Jay",
journal = "Molecular Pharmaceutics",
volume = "8",
number = "6",
pages = "2233-2243",
month = "December",
year = "2011",
doi = "10.1021/mp200094w",
issn = "1543-8384",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20120203-102207173",
note = "© 2011 American Chemical Society.\n\nPublished In Issue December 05, 2011; Article ASAP October 25, 2011; Just Accepted Manuscript October 10, 2011; Received: February 25, 2011; Accepted: October 09, 2011;\nRevised: July 19, 2011.\n\nL.K.M.-K. thanks J.C., D.R., and M.M.-K. for continued\nsupport. This work was supported by grants to L.K.M.-K. from\nthe NIH (R21 CA116014, R01 CA102126, R01 CA129822, and\nR01 CA140995), the DoD (BC050662), the Susan G. Komen Breast Cancer foundation (BCTR0201194), and the Donna and\nJesse Garber Award. Work at Caltech was supported by NIH\nDK019038 and the Arnold and Mabel Beckman Foundation.\nWork at the Technion was supported by The Herbert Irving\nCancer and Atherosclerosis Research Fund.",
revision_no = "30",
abstract = "HerGa is a self-assembled tumor-targeted particle that bears both tumor detection and elimination activities in a single, two-component complex (Agadjanian et al. Proc. Natl. Acad. Sci. U.S.A.2009, 106, 6105–6110). Given its multifunctionality, HerGa (composed of the fluorescent cytotoxic corrole macrocycle, S2Ga, noncovalently bound to the tumor-targeted cell penetration protein, HerPBK10) has the potential for high clinical impact, but its mechanism of cell killing remains to be elucidated, and hence is the focus of the present study. Here we show that HerGa requires HerPBK10-mediated cell entry to induce toxicity. HerGa (but not HerPBK10 or S2Ga alone) induced mitochondrial membrane potential disruption and superoxide elevation, which were both prevented by endosomolytic-deficient mutants, indicating that cytosolic exposure is necessary for corrole-mediated cell death. A novel property discovered here is that corrole fluorescence lifetime acts as a pH indicator, broadcasting the intracellular microenvironmental pH during uptake in live cells. This feature in combination with two-photon imaging shows that HerGa undergoes early endosome escape during uptake, avoiding compartments of pH < 6.5. Cytoskeletal disruption accompanied HerGa-mediated mitochondrial changes whereas oxygen scavenging reduced both events. Paclitaxel treatment indicated that HerGa uptake requires dynamic microtubules. Unexpectedly, low pH is insufficient to induce release of the corrole from HerPBK10. Altogether, these studies identify a mechanistic pathway in which early endosomal escape enables HerGa-induced superoxide generation leading to cytoskeletal and mitochondrial damage, thus triggering downstream cell death.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/28696,
title ="Rapid Water Reduction to H_2 Catalyzed by a Cobalt Bis(iminopyridine) Complex",
author = "Stubbert, Bryand D. and Peters, Jonas C.",
journal = "Journal of the American Chemical Society",
volume = "133",
number = "45",
pages = "18070-18073",
month = "November",
year = "2011",
doi = "10.1021/ja2078015",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20120106-104425949",
note = "© 2011 American Chemical Society. Received: August 17, 2011. Publication Date (Web): October 24, 2011. We thank Charles C. L. McCrory, Christopher Uyeda, and\nJames R. McKone for helpful discussions. Our work was supported by the NSF Center for Chemical Innovation on Solar\nFuels (CCI Solar, CHE-0802907 and CHE-0947829) and the\nStanford Global Climate and Energy Project (GCEP).",
revision_no = "25",
abstract = "A cobalt bis(iminopyridine) complex is a highly active electrocatalyst for water reduction, with an estimated apparent second order rate constant k_(app) ≤ 10^7 M^(–1)s^(–1) over a range of buffer/salt concentrations. Scan rate dependence data are consistent with freely diffusing electroactive species over pH 4–9 at room temperature for each of two catalytic reduction events, one of which is believed to be ligand based. Faradaic H_2 yields up to 87 ± 10% measured in constant potential electrolyses (−1.4 V vs SCE) confirm high reactivity and high fidelity in a catalyst supported by the noninnocent bis(iminopyridine) ligand. A mechanism involving initial reduction of Co^(2+) and subsequent protonation is proposed.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/25353,
title ="Redox reactivity of photogenerated osmium(II) complexes",
author = "Dempsey, Jillian L. and Winkler, Jay R.",
journal = "Dalton Transactions",
volume = "2011",
number = "40",
pages = "10633-10636",
month = "October",
year = "2011",
doi = "10.1039/C1DT11138H ",
issn = "1477-9226",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20110916-103243483",
note = "© 2011 The Royal Society of Chemistry. Received 16th June 2011, Accepted 8th August 2011. \nFirst published on the web 02 September 2011. This research was supported by an NSF Center for Chemical Innovation (CHE-0802907), the Arnold and Mabel Beckman Foundation, and CCSER (Gordon and Betty Moore Foundation).",
revision_no = "36",
abstract = "Powerful reductants [Os^(II)(NH_3)_5(L]^(2+) (L = OH_ 2, CH_3, CN can be generated upon ultraviolet excitation of relatively inert [Os^(II)(NH_3)_5(N_2)]^(2+) in aqueous and acetonitrile solutions. Reactions of photogenerated Os(II) complexes with methyl viologen to form methyl viologen radical cation and [Os^(III)(NH_3)_5L]^(3+) were monitored by transient absorption spectroscopy. Rate constants range from 4.9 × 10^4 M^(−1) s^(−1) in acetonitrile solution to 3.2 × 10^7 (pH 3) and 2.5 × 10^8 M^(−1) s^(−1) (pH 12) in aqueous media. Photogeneration of five-coordinate Os(II) complexes opens the way for mechanistic investigations of activation/reduction of CO_2 and other relatively inert molecules.\n",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/27791,
title ="Dual Coordination Modes of Ethylene-Linked NP2 Ligands in Cobalt(II) and Nickel(II) Iodides",
author = "Dong, Qingchen and Rose, Michael J.",
journal = "Inorganic Chemistry",
volume = "50",
number = "20",
pages = "10213-10224",
month = "October",
year = "2011",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20111115-152532868",
note = "© 2011 American Chemical Society. Received: June 7, 2011. Publication Date (Web): September 13, 2011. This work was supported by the NSF CCI Solar Fuels Research Program (CHE-0802907). M.J.R. also received support from an NSF ACC-F postdoctoral fellowship (NSF CHE-1042009). W.Y.W. and Q.C.D. thank the Hong Kong Research Grants Council (HKBU202508), the University Grants Committee of HKSAR, China (Project No. [AoE/P-03/08]) and Hong Kong Baptist University for support. We thank Drs. Larry Henling and Michael Day for assistance in solving crystal structures, and Dr. Angelo Di Bilio for assistance in recording EPR spectra. The Bruker KAPPA APEXII X-ray diffractometer was purchased via an NSF CRIF:MU award to the California Institute of Technology (CHE-0639094).",
revision_no = "29",
abstract = "Here we report the syntheses and crystal structures of a series of cobalt(II) and nickel(II) complexes derived from _RNP2 ligands (where R = OMe_(Bz), H_(Bz), Br_(Bz), Ph) bearing ethylene linkers between a single N and two P donors. The Co^(II) complexes generally adopt a tetrahedral configuration of general formula [(NP2)Co(I)_2], wherein the two phosphorus donors are bound to the metal center but the central N-donor remains unbound. We have found one case of structural isomerism within a single crystal structure. The Co^(II) complex derived from _(Bz)NP2 displays dual coordination modes: one in the tetrahedral complex [(_(Bz)NP2)Co(I)_2]; and the other in a square pyramidal variant, [(_(Bz)NP2)Co(I)_2]. In contrast, the Ni^(II) complexes adopt a square planar geometry in which the P(Et)N(Et)P donors in the ligand backbone are coordinated to the metal center, resulting in cationic species of formula [(_RNP2)Ni(I)]^+ with iodide as counterion. All Ni^(II) complexes exhibit sharp ^1H and ^(31)P spectra in the diamagnetic region. The Co^(II) complexes are high-spin (S = 3/2) in the solid state as determined by SQUID measurements from 4 to 300 K. Solution electron paramagnetic resonance (EPR) experiments reveal a high-spin/low-spin Co^(II) equilibrium that is dependent on solvent and ligand substituent.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/27792,
title ="Noninnocence in Metal Complexes: A Dithiolene Dawn",
author = "Eisenberg, Richard and Gray, Harry B.",
journal = "Inorganic Chemistry",
volume = "50",
number = "20",
pages = "9741-9751",
month = "October",
year = "2011",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20111116-071608250",
note = "© 2011 American Chemical Society. Received: May 31, 2011. Publication Date (Web): September 13, 2011. We dedicate this Forum contribution to the memory of our dear friend, Ed Stiefel, who made deep and lasting contributions to our story of dithiolene noninnocence. We are enormously grateful to the National Science Foundation for steadfast support of our work in the 1960s. We are still working with the NSF, now as PI (H.B.G.) and advisor (R.E.) in the CCI Solar Fuels Program (CHE-0802907).",
revision_no = "19",
abstract = "Noninnocence in inorganic chemistry traces its roots back half a century to work that was done on metal complexes containing unsaturated dithiolate ligands. In a flurry of activity in the early 1960s by three different research groups, homoleptic bis and tris complexes of these ligands, which came to be known as dithiolenes, were synthesized, and their structural, electrochemical, spectroscopic, and magnetic properties were investigated. The complexes were notable for facile one-electron transfers and intense colors in solution, and conventional oxidation-state descriptions could not account for their electronic structures. The bis complexes were, in general, found to be square-planar, including the first examples of this geometry for paramagnetic complexes and different formal dn configurations. Several of the neutral and monoanionic tris complexes were found to have trigonal-prismatic coordination, the first time that this geometry had been observed in molecular metal complexes. Electronic structural calculations employing extended Hückel and other semiempirical computational methods revealed extensive ligand–metal mixing in the frontier orbitals of these systems, including the observation of structures in which filled metal-based orbitals were more stable than ligand-based orbitals of the same type, suggesting that the one-electron changes upon oxidation or reduction were occurring on the ligand rather than on the metal center. A summary of this early work is followed with a brief section on the current interpretations of these systems based on more advanced spectroscopic and computational methods. The take home message is that the early work did indeed provide a solid foundation for what was to follow in investigations of metal complexes containing redox-active ligands.",
}
@book_section {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/34821,
title ="Electronic Structures of Oxo-Metal Ions",
author = "Winkler, Jay R. and Gray, Harry B.",
number = "142",
pages = "17-28",
month = "October",
year = "2011",
doi = "10.1007/430_2011_55",
isbn = "9783642273704",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20121010-111127266",
note = "© 2011 Springer-Verlag Berlin Heidelberg. Published online: 6 October 2011.\nWe dedicate this paper to the memory of Carl Ballhausen, a great scientist\nand a dear friend (Fig. 5). We note in closing that the B&G model is providing a firm foundation for structure/reactivity correlations in our current work on oxo-metal complexes [oxidative enzymes P450 and nitric oxide synthase (NIH DK019038, GM068461): water oxidation catalysts (NSF CCI Solar Program, CHE-0947829): and trans-dioxo osmium(VI) electrochemistry and\nphotochemistry (BP)]. We thank the Gordon and Betty Moore Foundation and the Arnold and Mabel Beckman Foundation for support of our research programs.\n",
revision_no = "17",
abstract = "The dianionic oxo ligand occupies a very special place in coordination\nchemistry, owing to its ability to donate π electrons to stabilize high oxidation states\nof metals. The ligand field theory of multiple bonding in oxo-metal ions, which was\nformulated in Copenhagen 50 years ago, predicts that there must be an \"oxo wall\"\nbetween Fe-Ru-Os and Co-Rh-Ir in the periodic table. In this tribute to Carl\nBallhausen, we review this early work as well as new developments in the field.\nIn particular, we discuss the electronic structures of beyond-the-wall (groups 9 and\n10) complexes containing metals multiply bonded to O- and N-donor ligands.\n",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/25510,
title ="Nitrogen Insertion into a Corrole Ring: Iridium Monoazaporphyrins",
author = "Palmer, Joshua H. and Brock-Nannestad, Theis",
journal = "Angewandte Chemie International Edition",
volume = "50",
number = "40",
pages = "9433-9436",
month = "September",
year = "2011",
issn = "1433-7851",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20110930-110349275",
note = "© 2011 Wiley-VCH Verlag GmbH & Co. Received: April 27, 2011.\nRevised: June 21, 2011. Article first published online: 30 Aug 2011. This work was supported by the NSF (CCI Solar, CHE-0802907 and CHE-0947829), the US-Israel BSF, CCSER (Gordon and Betty Moore Foundation), and the Arnold and Mabel Beckman Foundation. We thank Drs. Lawrence\u2005M. Henling and Michael\u2005W. Day for assistance with the acquisition and analysis of crystallographic data.",
revision_no = "17",
abstract = "A new route to rare porphyrinoids: The non-innocence of the corrole ring allows the oxidative ring insertion of a nitrogen atom under mild conditions (see scheme; NBS=N-bromosuccinimide). The resulting meso-substituted azaporphyrins exhibit high-energy Soret absorption bands and red luminescence. This new synthetic route will allow for the development of novel azaporphyrin complexes with relevance to the study of biomimetic oxidations.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/25490,
title ="Evaluation of Pt, Ni, and Ni–Mo electrocatalysts for hydrogen evolution on crystalline Si electrodes",
author = "McKone, James R. and Warren, Emily L.",
journal = "Energy and Environmental Science",
volume = "4",
number = "9",
pages = "3573-3583",
month = "September",
year = "2011",
doi = "10.1039/c1ee01488a",
issn = "1754-5692",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20110929-104011152",
note = "© 2011 The Royal Society of Chemistry. \n\nReceived 19 Apr 2011, Accepted 22 Jun 2011. First published on the web 01 Aug 2011. \n\nThis work was supported by the National Science Foundation (NSF) Powering the Planet Center for Chemical Innovation (CCI), Grants CHE-0802907 and CHE-0947829, and by the Molecular Materials Research Center of the Beckman Institute at the California Institute of Technology. The authors would like to acknowledge Joseph Beardslee for assistance with XPS analysis. JRM would like to thank the Department of Energy, Office of Science, for a graduate research fellowship. SWB gratefully acknowledges fellowship support from the Kavli Nanoscience Institute. ",
revision_no = "27",
abstract = "The dark electrocatalytic and light photocathodic hydrogen evolution properties of Ni, Ni–Mo alloys, and Pt on Si electrodes have been measured, to assess the viability of earth-abundant electrocatalysts for integrated, semiconductor coupled fuel formation. In the dark, the activities of these catalysts deposited on degenerately doped p^+-Si electrodes increased in the order Ni < Ni–Mo ≤ Pt. Ni–Mo deposited on degenerately doped Si microwires exhibited activity that was very similar to that of Pt deposited by metal evaporation on planar Si electrodes. Under 100 mW cm^(−2) of Air Mass 1.5 solar simulation, the energy conversion efficiencies of p-type Si/catalyst photoelectrodes ranged from 0.2–1%, and increased in the order Ni ≈ Ni–Mo < Pt, due to somewhat lower photovoltages and photocurrents for p-Si/Ni–Mo relative to p-Si/Ni and p-Si/Pt photoelectrodes. Deposition of the catalysts onto microwire arrays resulted in higher apparent catalytic activities and similar photoelectrode efficiencies than were observed on planar p-Si photocathodes, despite lower light absorption by p-Si in the microwire structures.\n",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/47915,
title ="Homogeneous cobalt electrocatalysts for solar driven hydrogen evolution from water",
author = "Stubbert, Bryan D. and Peters, Jonas C.",
journal = "Abstracts of Papers of the American Chemical Society",
volume = "242",
pages = "INOR 489",
month = "August",
year = "2011",
issn = "0065-7727",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140804-135735898",
note = "© 2011 American Chemical Society.",
revision_no = "12",
abstract = "Towards the bigger picture of developing modular solns. for photoelectrochem. water splitting, catalytic proton\nredn. mediated by cobalt bis(iminopyridine) complexes has been explored in buffered aq. media over a broad\nrange of pH conditions. The extremely rapid rates of electrocatalytic hydrogen evolution exhibited by firstgeneration\ncatalysts will be discussed in conjunction with the performance of second-generation\nelectrocatalysts. Details of electrochem. and photochem. mechanistic studies, kinetic competency, and the\neffects of reaction medium on H_2 evolution will also be presented.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/25460,
title ="Iodinated Aluminum(III) Corroles with Long-Lived Triplet\nExcited States",
author = "Vestfrid, Jenya and Botoshansky, Mark",
journal = "Journal of the American Chemical Society",
volume = "133",
number = "33",
pages = "12899-12901",
month = "August",
year = "2011",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20110928-083924165",
note = "© 2011 American Chemical Society. Received: April 4, 2011. Published: July 27, 2011. Publication Date (Web): July 27, 2011. This research was supported by the U.S. - Israel Binational Science Foundation (BSF) to Z.G. and H.B.G.",
revision_no = "27",
abstract = "The first reported iodination of a corrole leads to selective functionalization of the four C–H bonds on one pole of the macrocycle. An aluminum(III) complex of the tetraiodinated corrole, which exhibits red fluorescence, possesses a long-lived triplet excited state.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/24594,
title ="Shedding Light on Solar Fuel Efficiencies",
author = "Hammarström, Leif and Winkler, Jay R.",
journal = "Science",
volume = "333",
number = "6040",
pages = "288-288",
month = "July",
year = "2011",
doi = "10.1126/science.333.6040.288-a",
issn = "0036-8075",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20110729-085817678",
note = "© 2011 American Association for the Advancement of Science. ",
revision_no = "13",
abstract = "In their review \"Comparing photosynthetic\nand photovoltaic efficiencies and recognizing\nthe potential for improvement\" (13\nMay, p. 805), R. E. Blankenship et al. compare\nthe conversion efficiency of photosynthesis\nwith that for production of hydrogen\nby photovoltaics and subsequent water\nelectrolysis (PV-EL). They conclude that the\nlatter technology is more efficient, but also\npoint out ongoing and future research directions\nthat could lead to substantial conversion\nefficiency increases in plants and microorganisms.\nWe agree that careful analysis of\ncurrent limitations for a system is valuable as\na guide to researchers working on solutions\nto bottleneck problems. However, using a single\nfigure of merit may discount other important\nconsiderations, and could prematurely\nidentify technology winners and discourage\nresearch in other promising areas.\n",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/24862,
title ="Ratiometric spectral imaging for fast tumor detection\nand chemotherapy monitoring in vivo",
author = "Hwang, Jae Youn and Gross, Zeev",
journal = "Journal of Biomedical Optics",
volume = "16",
number = "6",
pages = "Art. No. 066007",
month = "June",
year = "2011",
doi = "10.1117/1.3589299",
issn = "1083-3668",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20110815-134404525",
note = "© 2011 SPIE. \n\nPaper 10601RR received Dec. 14, 2010; revised manuscript received Apr. 10, 2011; accepted for publication Apr. 12, 2011; published online Jun. 9, 2011. \n\nThis research was supported by the US Navy Bureau of Medicine and Surgery (D.L.F.), the NIH DK019038 (H.B.G.), the NIH R01 CA140995 (L.K.M.K.), the NIH R01 CA129822 (L.K.M.K.), and the BSF (Z.G. and H.B.G.).We sincerely thank Dr. V. Krishnan Ramanujan for providing valuable comments and Dr. Jihoon Jeong for developing and providing an ImageJ\\ plug-in program for spectral imaging.",
revision_no = "14",
abstract = "We report a novel in vivo spectral imaging approach to cancer detection and chemotherapy assessment. We describe and characterize a ratiometric spectral imaging and analysis method and evaluate its performance for tumor detection and delineation by quantitatively monitoring the specific accumulation of targeted gallium corrole (HerGa) into HER2-positive (HER2 +) breast tumors. HerGa temporal accumulation in nude mice bearing HER2 + breast tumors was monitored comparatively by a. this new ratiometric imaging and analysis method; b. established (reflectance and fluorescence) spectral imaging; c. more commonly used fluorescence intensity imaging. We also tested the feasibility of HerGa imaging in vivo using the ratiometric spectral imaging method for tumor detection and delineation. Our results show that the new method not only provides better quantitative information than typical spectral imaging, but also better specificity than standard fluorescence intensity imaging, thus allowing enhanced in vivo outlining of tumors and dynamic, quantitative monitoring of targeted chemotherapy agent accumulation into them.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/23806,
title ="Phototriggering Electron Flow through Re^I-modified Pseudomonas aeruginosa Azurins",
author = "Blanco-Rodríguez, Ana María and Di Bilio, Angel J.",
journal = "Chemistry: a European Journal",
volume = "17",
number = "19",
pages = "5350-5361",
month = "May",
year = "2011",
doi = "10.1002/chem.201002162",
issn = "0947-6539",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20110526-090614868",
note = "© 2011 Wiley VCH Verlag GmbH&Co. KGaA, Weinheim.\n\nReceived: July 28, 2010. Revised: December 12, 2010. Published online: April 5, 2011.\n\n\nWe thank Lucie Sokolová (J.W. Goethe University, Frankfurt am Main) for measuring and interpreting the solution LILBID mass spectra. Research at Caltech was supported by the NSF Center for Chemical Innovation (Powering the Planet CHE-0802907 and CHE-0947829) and by NIH (DK019038 to HBG, JRW). The crystallographic work was supported by the NSF-CHE-0749997(BRC). The TRIR and theoretical investigations were funded by the STFC Rutherford Appleton Laboratory, CMSD 43, Queen Mary University of London, European COST D35 and ESF-DYNA programs, and Ministry of Education of the Czech Republic grants ME10124 and OC09043. ",
revision_no = "37",
abstract = "The [Re^I(CO)_3(4,7-dimethyl-1,10-phenanthroline)(histidine-124)(tryptophan-122)] complex, denoted [Re^I(dmp)(W122)], of Pseudomonas aeruginosa azurin behaves as a single photoactive unit that triggers very fast electron transfer (ET) from a distant (2\u2005nm) Cu^I center in the protein. Analysis of time-resolved (ps–μs) IR spectroscopic and kinetics data collected on [Re^I(dmp)(W122)AzM] (in which M=Zn^(II), Cu^(II), Cu^I; Az=azurin) and position-122 tyrosine (Y), phenylalanine (F), and lysine (K) mutants, together with excited-state DFT/time-dependent (TD)DFT calculations and X-ray structural characterization, reveal the character, energetics, and dynamics of the relevant electronic states of the [Re^I(dmp)(W122)] unit and a cascade of photoinduced ET and relaxation steps in the corresponding Re–azurins. Optical population of [Re^I(imidazole-H124)(CO)_3]→dmp ^1CT states (CT=charge transfer) is followed by around 110\u2005fs intersystem crossing and about 600\u2005ps structural relaxation to a ^3CT state. The IR spectrum indicates a mixed Re^I(CO)_3,A→dmp/π→π^*(dmp) character for aromatic amino acids A122 (A=W, Y, F) and Re^I(CO)_3→dmp metal–ligand charge transfer (MLCT) for [Re^I(dmp)(K122)AzCu^(II)]. In a few ns, the ^3CT state of [Re^I(dmp)(W122)AzM] establishes an equilibrium with the [Re^I(dmp.^−)(W122.^+)AzM] charge-separated state, ^3CS, whereas the ^3CT state of the other Y, F, and K122 proteins decays to the ground state. In addition to this main pathway, ^3CS is populated by fs- and ps-W(indole)→Re^(II) ET from ^1CT and the initially “hot” ^3CT states, respectively. The ^3CS state undergoes a tens-of-ns dmp.^−→W122.^+ ET recombination leading to the ground state or, in the case of the Cu^I azurin, a competitively fast (≈30\u2005ns over 1.12\u2005nm) Cu^I→W.^+ ET, to give [Re^I(dmp.^−)(W122)AzCu^(II)]. The overall photoinduced CuI→Re(dmp) ET through [Re^I(dmp)(W122)AzCu^I] occurs over a 2\u2005nm distance in <50\u2005ns after excitation, with the intervening fast ^3CT–^3CS equilibrium being the principal accelerating factor. No reaction was observed for the three Y, F, and K122 analogues. Although the presence of [Re(dmp)(W122)AzCu^(II)] oligomers in solution was documented by mass spectrometry and phosphorescence anisotropy, the kinetics data do not indicate any significant interference from the intermolecular ET steps. The ground-state dmp–indole π–π interaction together with well-matched W/W.^+ and excited-state [Re^II(CO)_3(dmp.^−)]/[Re^I(CO)_3(dmp.^−)] potentials that result in very rapid electron interchange and ^3CT–^3CS energetic proximity, are the main factors responsible for the unique ET behavior of [Re^I(dmp)(W122)]-containing azurins.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/23640,
title ="Mass Spectrometric Characterization of Oligomers in Pseudomonas aeruginosa Azurin Solutions",
author = "Soklová, Lucie and Williamson, Heather",
journal = "Journal of Physical Chemistry B",
volume = "115",
number = "16",
pages = "4790-4800",
month = "April",
year = "2011",
doi = "10.1021/jp110460k",
issn = "1520-6106",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20110511-101806238",
note = "© 2011 American Chemical Society.\n\nPublished In Issue April 28, 2011; Article ASAP March 31, 2011; Received: November 02, 2010; Revised: February 16, 2011.\n\nTechnical support from Mr. H.D. Barth (Frankfurt) is gratefully acknowledged. Funding was provided by the “Cluster of Excellence Frankfurt (CEF) Macromolecular complexes”, Queen Mary University of London, Ministry of Education of the Czech Republic grants ME10124 and LC06063 (J. Sýkora, M. Hof) as well as the European collaboration program COST Action D35. Work at Caltech was supported by NIH (DK019038 to HBG).",
revision_no = "32",
abstract = "We have employed laser-induced liquid bead ion desorption mass spectroscopy (LILBID MS) to study the solution behavior of Pseudomonas aeruginosa azurin as well as two mutants and corresponding Re-labeled derivatives containing a Re(CO)_(3)(4,7-dimethyl-1,10-phenanthroline)^+ chromophore appended to a surface histidine. LILBID spectra show broad oligomer distributions whose particular patterns depend on the solution composition (pure H_(2)O, 20−30 mM NaCl, 20 and 50 mM NaP_i or NH_(4)P_i at pH = 7). The distribution maximum shifts to smaller oligomers upon decreasing the azurin concentration and increasing the buffer concentration. Oligomerization is less extensive for native azurin than its mutants. The oligomerization propensities of unlabeled and Re-labeled proteins are generally comparable, and only Re126 shows some preference for the dimer that persists even in highly diluted solutions. Peak shifts to higher masses and broadening in 20−50 mM NaP_i confirm strong azurin association with buffer ions and solvation. We have found that LILBID MS reveals the solution behavior of weakly bound nonspecific protein oligomers, clearly distinguishing individual components of the oligomer distribution. Independently, average data on oligomerization and the dependence on solution composition were obtained by time-resolved anisotropy of the Re-label photoluminescence that confirmed relatively long rotation correlation times, 6−30 ns, depending on Re−azurin and solution composition. Labeling proteins with Re-chromophores that have long-lived phosphorescence extends the time scale of anisotropy measurements to hundreds of nanoseconds, thereby opening the way for investigations of large oligomers with long rotation times.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/23500,
title ="Electron Transfer Reactivity of Type Zero Pseudomonas aeruginosa Azurin",
author = "Lancaster, Kyle M. and Farver, Ole",
journal = "Journal of the American Chemical Society",
volume = "133",
number = "13",
pages = "4865-4873",
month = "April",
year = "2011",
doi = "10.1021/ja1093919",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20110429-103650204",
note = "© 2011 American Chemical Society.\n\nPublished In Issue April 06, 2011; Article ASAP March 15, 2011; Received: October 28, 2010.\n\nWe thank Jay Winkler and Bruce Brunschwig for helpful\ndiscussions, Serena DeBeer for XAS advice, Matt Sazinsky for\nuse of an anaerobic chamber, and Eran Gilad for valuable\nassistance with PR system operations. We also acknowledge\nseveral suggestions from a reviewer. Our research was supported by NIH DK019038 and Stanford GCEP. X-ray absorption spectroscopic experiments were carried out at the Stanford Synchrotron Radiation Lightsource, a national user facility operated by Stanford University on behalf of the U.S. Department of Energy, Office of Basic Energy Sciences. The SSRL Structural Molecular Biology Program is supported by the Department of Energy, Office of Biological and Environmental Research, and by the National Institutes of Health, National Center for Research Resources, Biomedical Technology Program.",
revision_no = "28",
abstract = "Type zero copper is a hard-ligand analogue of the classical type 1 or blue site in copper proteins that function as electron transfer (ET) agents in photosynthesis and other biological processes. The EPR spectroscopic features of type zero Cu^(II) are very similar to those of blue copper, although lacking the deep blue color, due to the absence of thiolate ligation. We have measured the rates of intramolecular ET from the pulse radiolytically generated C3−C26 disulfide radical anion to the Cu^(II) in both type zero C112D/M121L and type 2 C112D Pseudomonas aeruginosa azurins in pH 7.0 aqueous solutions between 8 and 45 °C. We also have obtained rate/temperature (10−30 °C) profiles for ET reactions between these mutants and the wild-type azurin. Analysis of the rates and activation parameters for both intramolecular and intermolecular ET reactions indicates that the type zero copper reorganization energy falls in a range (0.9−1.1 eV) slightly above that for type 1 (0.7−0.8 eV), but substantially smaller than that for type 2 (>2 eV), consistent with XAS and EXAFS data that reveal minimal type zero site reorientation during redox cycling.",
}
@book_section {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/85886,
title ="Metals, Microbes, and Solar Fuel",
author = "Gray, Harry B. and Magyar, John S.",
pages = "279-290",
month = "March",
year = "2011",
doi = "10.1002/9781118007099.ch17",
isbn = "9780470390436",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180416-160315014",
note = "© 2011 John Wiley & Sons, Inc. \n\nPublished Online: 14 March 2011; Published Print: 21 March 2011.\n\n",
revision_no = "10",
abstract = "[no abstract]",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/24055,
title ="Bioinorganic Chemistry - Special Issue of the Indian Journal of Chemistry, Section A - Foreword",
author = "Gray, Harry B.",
journal = "Indian Journal of Chemistry Section A",
volume = "50",
number = "3-4",
pages = "341-341",
month = "March",
year = "2011",
issn = "0376-4710",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20110620-095641722",
note = "© 2011 NISCAIR.\n\n\n\n",
revision_no = "11",
abstract = "I am very pleased that in this International Year of Chemistry several of my\ndistinguished colleagues in India have put together a special bioinorganic\nchemistry issue of the Indian Journal of Chemistry, Sect. A. I am grateful to my\nvery good friend Prof. Shyamalava Mazumdar, and the other guest editors for the\ninvitation to write a few lines of introduction to this special issue.",
}
@book_section {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/73420,
title ="Multimode optical imaging for translational chemotherapy: in vivo tumor detection and delineation by targeted gallium corroles",
author = "Hwang, Jae Youn and Gross, Zeev",
number = "7902",
pages = "Art. No. 79020F",
month = "February",
year = "2011",
doi = "10.1117/12.877780",
issn = "0277786X",
isbn = "978-0-81948-439-0",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170111-103042462",
note = "© 2011 SPIE. \n\nPartial support from the US Navy Bureau of Medicine and Surgery is gratefully acknowledged. This work was partially supported by grants from the NIH (R21 CA116014, R01 CA102126, R01 CA129822, and R01 CA140995), the DoD (BC050662), the Susan G. Komen Breast Cancer foundation (BCTR0201194), and the Donna and Jesse Garber Award. Work at Caltech was supported by NIH DK019038 and the Arnold and Mabel Beckman Foundation. Work at the Technion was supported by The Herbert Irving Cancer and Atherosclerosis Research Fund.",
revision_no = "12",
abstract = "We report the feasibility of tumor detection and delineation in vivo using multimode optical imaging of targeted gallium corrole (HerGa). HerGa is highly effective for targeted HER2+ tumor elimination in vivo, and it emits intense fluorescence. These unique characteristics of HerGa prompted us to investigate the potential of HerGa for tumor detection and delineation, by performing multimode optical imaging ex vivo and in vivo; the imaging modes included fluorescence intensity, spectral (including ratiometric), lifetime, and two-photon excited fluorescence, using our custombuilt imaging system. While fluorescence intensity imaging provided information about tumor targeting capacity and tumor retention of HerGa, ratiometric spectral imaging offered more quantitative and specific information about HerGa location and accumulation. Most importantly, the fluorescence lifetime imaging of HerGa allowed us to discriminate between tumor and non-tumor regions by fluorescence lifetime differences. Finally, two-photon excited fluorescence images provided highly resolved and thus topologically detailed information around the tumor regions where HerGa accumulates. Taken together, the results shown in this report suggest the feasibility of tumor detection and delineation by multimode optical imaging of HerGa, and fluorescent chemotherapy agents in general. Specifically, the multimode optical imaging can offer complementary and even synergetic information simultaneously in the tumor detection and delineation by HerGa, thus enhancing contrast.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/22680,
title ="Spectroscopic and redox properties of amine-unctionalized K_2[Os-^(II)(bpy)(CN)_4] complexes",
author = "Ahrens, Michael J. and Bertin, Paul A.",
journal = "Dalton Transactions",
volume = "40",
number = "8",
pages = "1732-1736",
month = "February",
year = "2011",
issn = "1477-9226",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20110307-093950733",
note = "© 2011 Royal Society of Chemistry. Received 26th October 2010, Accepted 13th December 2010. We acknowledge the Integrated Molecular Structure Education\nand Research Center (IMSERC) at Northwestern University for\ninstrument use (NMR, HRMS). Work at California Institute of\nTechnology is supported by NIH DK019038.",
revision_no = "27",
abstract = "We report the first examples of amine-functionalized K_2[Os^(II)(bpy)(CN)_4] (bpy = 2,2'-bipyridine) complexes. The tetracyanoosmate complexes were prepared by UV irradiation (λ = 254 nm) of K_4[Os^(II)(CN)_6] and primary amine-functionalized bpy ligands in acidic aqueous media. The aqueous solution pH dependences of the spectroscopic and redox properties of 4,4'- and 5,5'-substituted complexes have been investigated. The pendant amine functional groups and coordinated cyanide ligands are basic sites that can be sequentially protonated, thereby allowing systematic tuning of electrochemical and optical spectroscopic properties.",
}
@book_section {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/71578,
title ="Investigating the photosensitizer-potential of targeted gallium corrole using multimode optical imaging",
author = "Hwang, Jae Youn and Lubow, Jay",
number = "7886",
pages = "Art. No. 78860M",
month = "February",
year = "2011",
doi = "10.1117/12.873337",
isbn = "9780819484239",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20161028-124138808",
note = "© 2011 SPIE. \n\nThis work was supported by grants from the NIH (R21 CA116014, R01 CA102126, R01 CA129822, and R01 CA140995), the DoD (BC050662), the Susan G. Komen Breast Cancer foundation (BCTR0201194), and the Donna and Jesse Garber Award. Work at Caltech was supported by NIH DK019038 and the Arnold and Mabel Beckman Foundation. Work at the Technion was supported by The Herbert Irving Cancer and Atherosclerosis Research Fund. Partial support from the US Navy Bureau of Medicine and Surgery is gratefully acknowledged. LKMK wishes to thank JC, MMK, and DR for ongoing support.",
revision_no = "11",
abstract = "We recently developed a novel therapeutic particle, HerGa, for breast cancer treatment and detection. HerGa consists of a tumor-targeted cell penetration protein noncovalently assembled with a gallium-metallated corrole. The corrole is structurally similar to porphyrin, emits intense fluorescence, and has proven highly effective for breast tumor treatment preclinically, without light exposure. Here, we tested HerGa as a photosensitizer for photodynamic therapy and investigated its mechanism of action using multimode optical imaging. Using confocal fluorescence imaging, we observed that HerGa disrupts the mitochondrial membrane potential in situ, and this disruption is substantially augmented by light exposure. In addition, spectral and fluorescence lifetime imaging were utilized to both validate the mitochondrial membrane potential disruption and investigate HerGa internalization, allowing us to optimize the timing for light dosimetry. We observed, using advanced multimode optical imaging, that light at a specific wavelength promotes HerGa cytotoxicity, which is likely to cause disruption of mitochondrial function. Thus, we can identify for the first time the capacity of HerGa as a photosensitizer for photodynamic therapy and reveal its mechanism of action, opening possibilities for therapeutic intervention in human breast cancer management.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/23227,
title ="Electronic Structures of Group 9 Metallocorroles with Axial Ammines",
author = "Dong, Sijia S. and Nielsen, Robert J.",
journal = "Inorganic Chemistry",
volume = "50",
number = "3",
pages = "764-770",
month = "February",
year = "2011",
doi = "10.1021/ic1005902",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20110404-100258063",
note = "© 2011 American Chemical Society. Published In Issue February 07, 2011. Article ASAP January 07, 2011. Received March 29, 2010. This work was supported by an NSF Center for Chemical Innovation (CCI Powering the Planet, Grants CHE-0802907 and CHE-0947829), the U.S.-Israel BSF (Z.G. and H.B.G.), CCSER (Gordon and Betty Moore Foundation), and the Arnold and Mabel Beckman Foundation. W.A.G. and R.S.N. and\nthe quantum mechanicals calculations were supported as\npart of the Center for Catalytic Hydrocarbon Functionalization, an Energy Frontier Research Center funded\nby the U.S. Department of Energy, Office of Science,\nOffice of Basic Energy Sciences under Award Number\nDE-SC0001298. S.S.D. was also supported by the Overseas\nResearch Fellowship Scheme from the Faculty of\nScience, University of Hong Kong. ",
revision_no = "36",
abstract = "The electronic structures of metallocorroles (tpfc)M(NH_3)_2 and (tfc)M(NH_3)_2 (tpfc is the trianion of 5,10,15-(tris)pentafluorophenylcorrole, tfc is the trianion of 5,10,15-trifluorocorrole, and M = Co, Rh, Ir) have been computed using first principles quantum mechanics [B3LYP flavor of Density Functional Theory (DFT) with Poisson−Boltzmann continuum solvation]. The geometry was optimized for both the neutral systems (formal M^(III) oxidation state) and the one-electron oxidized systems (formally M^(IV)). As expected, the M^(III) systems have a closed shell d^6 configuration; for all three metals, the one-electron oxidation was calculated to occur from a ligand-based orbital (highest occupied molecular orbital (HOMO) of B_1 symmetry). The ground state of the formal M^(IV) system has M^(III)-Cπ character, indicating that the metal remains d^6, with the hole in the corrole π system. As a result the calculated M^(IV/III) reduction potentials are quite similar (0.64, 0.67, and 0.56 V vs SCE for M = Ir, Rh and Co, respectively), whereas the differences would have been large for purely metal-based oxidations. Vertically excited states with substantial metal character are well separated from the ground state in one-electron-oxidized cobalt (0.27 eV) and rhodium (0.24 eV) corroles, but become closer in energy in the iridium (0.15 eV) analogues. The exact splittings depend on the chosen functional and basis set combination and vary by ~0.1 eV.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/29586,
title ="Multimodal wide-field two-photon excitation imaging: characterization of the technique for in vivo applications",
author = "Hwang, Jae Youn and Wachsmann-Hogiu, Sebastian",
journal = "Biomedical Optics Express",
volume = "2",
number = "2",
pages = "356-364",
month = "February",
year = "2011",
doi = "10.1364/BOE.2.000356",
issn = "2156-7085",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20120306-091219207",
note = "© 2011 Optical Society of America. Received 9 Dec 2010; revised 9 Jan 2011; accepted 10 Jan 2011; published 13 Jan 2011. Partial support from the U.S. Navy Bureau of Medicine and Surgery is gratefully acknowledged. Work at Caltech was supported by a CIT-COH initiative grant.",
revision_no = "12",
abstract = "We report fast, non-scanning, wide-field two-photon fluorescence excitation with spectral and lifetime detection for in vivo biomedical applications. We determined the optical characteristics of the technique, developed a Gaussian flat-field correction method to reduce artifacts resulting from non-uniform excitation such that contrast is enhanced, and showed that it can be used for ex vivo and in vivo cellular-level imaging. Two applications were demonstrated: (i) ex vivo measurements of beta-amyloid plaques in retinas of transgenic mice, and (ii) in vivo imaging of sulfonated gallium(III) corroles injected into tumors. We demonstrate that wide-field two photon fluorescence excitation with flat-field correction provides more penetration depth as well as better contrast and axial resolution than the corresponding one-photon wide field excitation for the same dye. Importantly, when this technique is used together with spectral and fluorescence lifetime detection modules, it offers improved discrimination between fluorescence from molecules of interest and autofluorescence, with higher sensitivity and specificity for in vivo applications.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/23014,
title ="Geometrical analysis of cytochrome c unfolding",
author = "Urie, Kristopher G. and Pletneva, Ekaterina",
journal = "Molecular Physics",
volume = "109",
number = "2",
pages = "301-313",
month = "January",
year = "2011",
doi = "10.1080/00268976.2010.521202",
issn = "0026-8976",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20110321-142051991",
note = "© 2011 Taylor & Francis.\n\nReceived 14 July 2010; final version received 31 August 2010. \nFirst Published on: 22 December 2010.\n\nResearch at Caltech is supported by the National Institutes\nof Health (DKOI9038, GM068461), the National Science\nFoundation (CHE-0802907), and the Arnold and Mabel\nBeckman Foundation.",
revision_no = "16",
abstract = "A geometrical model has been developed to study the unfolding of iso-1 cytochrome c. The model draws on the crystallographic data reported for this protein. These data were used to calculate the distance between specific residues in the folded state, and in a sequence of extended states defined by n = 3, 5, 7, 9, 11, 13, and 15 residue units. Exact calculations carried out for each of the 103 residues in the polypeptide chain demonstrate that different regions of the chain have different unfolding histories. Regions where there is a persistence of compact structures can be identified, and this geometrical characterization is fully consistent with analyses of time-resolved fluorescence energy-transfer (TrFET) data using dansyl-derivatized cysteine side-chain probes at positions 39, 50, 66, 85, and 99. The calculations were carried out assuming that different regions of the polypeptide chain unfold synchronously. To test this assumption, lattice Monte Carlo simulations were performed to study systematically the possible importance of asynchronicity. Calculations show that small departures from synchronous dynamics can arise if displacements of residues in the main body of the chain are much more sluggish than near-terminal residues.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/23318,
title ="Unfolding four-helix bundles",
author = "Gray, Harry B. and Winkler, Jay R.",
journal = "Molecular Physics",
volume = "109",
number = "6",
pages = "905-916",
month = "January",
year = "2011",
doi = "10.1080/00268976.2011.558855 ",
issn = "0026-8976",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20110414-085410464",
note = "© 2011 Taylor & Francis. Received 25 October 2010; final version received 24 January 2011. ",
revision_no = "15",
abstract = "A geometrical model has been developed to describe the early stages of unfolding of cytochromes c' and c-b_(562). Calculations are based on a step-wise extension of the polypeptide chain subject to the constraint that the spatial relationship among the residues of each triplet is fixed by the native-state crystallographic data. The response of each protein to these structural perturbations allows the evolution of each of the four helices in these two proteins to be differentiated. It is found that the two external helices in c' unfold before its two internal helices, whereas exactly the opposite behaviour is demonstrated by c-b_(562). Each of these cytochromes has an extended, internal, non-helical (\"turning\") region that initially lags behind the most labile helix but then, at a certain stage (identified for each cytochrome), unravels before any of the four helices present in the native structure. It is believed that these predictions will be useful in guiding future experimental studies on the unfolding of these two cytochromes. ",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/21675,
title ="Mechanism of H_2 Evolution from a Photogenerated Hydridocobaloxime\n",
author = "Dempsey, Jillian L. and Winkler, Jay R.",
journal = "Journal of the American Chemical Society",
volume = "132",
number = "47",
pages = "16774-1677",
month = "December",
year = "2010",
doi = "10.1021/ja109351h ",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20110110-150437628",
note = "© 2010 American Chemical Society.\n\nReceived October 17, 2010. Publication Date (Web): November 10, 2010. \n\nWe thank Bruce Brunschwig, Alec Durrell, Maraia Ener, Jonas Peters, and Jeff Warren for helpful discussions and experimental advice. Charles McCrory and Jacob Good are acknowledged for generous assistance with GC measurements. This work was supported by an NSF Center for Chemical Innovation (Powering the Planet, CHE-0947829), the Arnold and Mabel Beckman Foundation, and CCSER (Gordon and Betty Moore Foundation). J.L.D. was supported by an NSF Graduate Research Fellowship.",
revision_no = "16",
abstract = "Proton transfer from the triplet excited state of brominated naphthol to a difluoroboryl bridged Co^I-diglyoxime complex, forming Co^(III)H, was monitored via transient absorption. The second-order rate constant for Co^(III)H formation is in the range (3.5−4.7) × 10^9 M^(−1) s^(−1), with proton transfer coupled to excited-state deactivation of the photoacid. Co^(III)H is subsequently reduced by excess Co^I-diglyoxime in solution to produce Co^(II)H (k_(red) = 9.2 × 10^6 M^(−1) s^(−1)), which is then protonated to yield Co^(II)-diglyoxime and H_2.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/33247,
title ="Electron tunneling through mutant azurins on mixed SAM gold electrodes",
author = "Yokoyama, K. and Nakamura, N.",
month = "December",
year = "2010",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20120816-072045664",
note = "© 2012 American Chemical Society.",
revision_no = "13",
abstract = "We are investigating interfacial electron transfer rates of P. aeruginosa azurin and its mutants using electrochem. at 1:1\nCH3(CH2)nSH:HO(CH2)nSH mixed-SAM gold electrodes. We have examd. interfacial electron transfer rates of mutant\nazurins in which asparagine-47 was replaced by alanine, aspartic acid, lysine, arginine, leucine, threonine, serine, and\nglutamine. The N47D mutant on a mixed SAM exhibited a well-defined electrochem. response; N47T and N47S gave a\nweak signal; but the other 5 mutants showed no response. It is likely that the N47 side-chain carbonyl interacts with the\nmixed SAM surface, providing a very favorable electron tunneling pathway to the copper via an N47-C112 hydrogen\nbond. We also have examd. interfacial electron transfer rates of M121X mutant azurins. The ET rates for M121E are 2\norders of magnitude smaller; those for M121Q are almost 1 order of magnitude smaller; and those for the M121L protein\nare similar to those of wild-type azurin at pH 7. In addn., we have found that type zero azurins have higher ET rates than\nthose of type 2 proteins (rates for C112D are 3 orders of magnitude smaller; those for type zero C112D/M121X (X=L and\nI) are 2 orders of magnitude smaller than wild-type at pH 7).",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/21864,
title ="Proton-Coupled Electron Flow in Protein Redox Machines\n",
author = "Dempsey, Jillian L. and Winkler, Jay R.",
journal = "Chemical Reviews",
volume = "110",
number = "12",
pages = "7024-7039",
month = "December",
year = "2010",
doi = "10.1021/cr100182b ",
issn = "0009-2665",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20110124-105132769",
note = "© 2010 American Chemical Society.\n\nReceived June 11, 2010.\nPublication Date (Web): November 17, 2010.\nThis article is part of the 2010 Proton-Coupled Electron Transfer special issue.\n\nOur work is supported by the NIH (DK019038, GM068461),\nan NSF Center for Chemical Innovation Grant (CHE-0802907), GCEP (Stanford), CCSER (Gordon and Betty\nMoore Foundation), and the Arnold and Mabel Beckman\nFoundation.",
revision_no = "25",
abstract = "Electron transfer (ET) reactions are fundamental steps in biological redox processes. Respiration is a case in point: at least 15 ET reactions are required to take reducing equivalents from NADH, deposit them in O_2, and generate the electrochemical proton gradient that drives ATP synthesis. Most of these reactions involve quantum tunneling between weakly coupled redox cofactors (ET distances > 10 Å) embedded in the interiors of folded proteins. Here we review experimental findings that have shed light on the factors controlling these distant ET events. We also review work on a sensitizer-modified copper protein photosystem in which multistep electron tunneling (hopping) through an intervening tryptophan is orders of magnitude faster than the corresponding single-step ET reaction.If proton transfers are coupled to ET events, we refer to the processes as proton coupled ET, or PCET, a term introduced by Huynh and Meyer in 1981. Here we focus on two protein redox machines, photosystem II and ribonucleotide reductase, where PCET processes involving tyrosines are believed to be critical for function. Relevant tyrosine model systems also will be discussed.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/20942,
title ="Photooxidation of cytochrome P450-BM3",
author = "Ener, Maraia E. and Lee, Young-Tae",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "107",
number = "44",
pages = "18783-18786",
month = "November",
year = "2010",
doi = "10.1073/pnas.1012381107 ",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20101122-111913931",
note = "© 2010 National Academy of Sciences.\n\nContributed by Harry B. Gray, August 19, 2010 (sent for review July 2, 2010).\nPublished online before print October 14, 2010.\nThis research was supported by the National Institutes\nof Health (DK019038) and The Arnold and Mabel Beckman Foundation. L.C. thanks Dr. Phoebe Glazer for helpful discussions.\nAuthor contributions: M.E.E., J.R.W., H.B.G., and L.C. designed research; M.E.E., Y.-T.L., and L.C. performed research; M.E.E., J.R.W., and L.C. analyzed data; and M.E.E., J.R.W., H.B.G., and L.C. wrote the paper.\nThe authors declare no conflict of interest.\nData deposition: The crystallography, atomic coordinates, and structure factors have been deposited in the Protein Data Bank, www.pdb.org (PDB ID code 3NPL and Research Collaboratory for Structural Bioinformatics (RCSB) ID code RCSB060120).\n\n",
revision_no = "23",
abstract = "High-valent iron-oxo species are thought to be intermediates in the catalytic cycles of oxygenases and peroxidases. An attractive route to these iron-oxo intermediates involves laser flash-quench oxidation of ferric hemes, as demonstrated by our work on the ferryl\n(compound II) and ferryl porphyrin radical cation (compound I) intermediates of horseradish peroxidase. Extension of this work to include cytochrome P450-BM3 (CYP102A1) has required covalent attachment of a Ru^(II) photosensitizer to a nonnative cysteine near the heme (Ru^(II)_(K97C)-Fe^(III)_(P450)), in order to promote electron transfer from the Fe^(III) porphyrin to photogenerated Ru^(III). The Ru^(II)_(K97C)Fe^(III)_(P450) conjugate was structurally characterized by X-ray crystallography (2.4 Å resolution; Ru-Fe distance, 24 Å). Flash-quench oxidation of the ferric-aquo heme produces an Fe^(IV)-hydroxide species (compound II) within 2 ms. Difference spectra for three singly oxidized P450-BM3 intermediates were obtained from kinetics modeling of the transient absorption data in combination with generalized singular value decomposition analysis and multiexponential\nfitting.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/20555,
title ="Outer-Sphere Effects on Reduction Potentials of Copper Sites in Proteins: The Curious Case of High Potential Type 2 C112D/M121E Pseudomonas aeruginosa Azurin",
author = "Lancaster, Kyle M. and Sproules, Stephen",
journal = "Journal of the American Chemical Society",
volume = "132",
number = "41",
pages = "14590-14595",
month = "October",
year = "2010",
doi = "10.1021/ja105731x",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20101027-093220417",
note = "© 2010 American Chemical Society. \n\nReceived June 29, 2010. Publication Date (Web): September 29, 2010. Published In Issue October 20, 2010. \n\nWe thank Prof. Serena DeBeer and Prof. Israel Pecht for insightful discussions. This work was supported by the NIH (DK019038 to H.B.G.). Portions of this research were carried out at the Stanford Synchrotron Radiation Lightsource, a national user facility operated by Stanford University on behalf of the U.S. Department of Energy, Office of Basic Energy Sciences. The SSRL Structural Molecular Biology Program is supported by the Department of Energy, Office of Biological and Environmental Research, and by the National Institutes of Health, National Center for Research Resources, Biomedical Technology Program. The Gordon and Betty Moore Foundation is acknowledged for their support of the Molecular Observatory at Caltech. \n\nSupporting Information: Representative redox titration, EPRs across the experimental pH range, and pH 10.0 crystal structure data. This material is available free of charge via the Internet at http://pubs.acs.org.",
revision_no = "33",
abstract = "Redox and spectroscopic (electronic absorption, multifrequency electron paramagnetic resonance (EPR), and X-ray absorption) properties together with X-ray crystal structures are reported for the type 2 Cu^(II) C112D/M121E variant of Pseudomonas aeruginosa azurin. The results suggest that Cu^(II) is constrained from interaction with the proximal glutamate; this structural frustration implies a “rack” mechanism for the 290 mV (vs NHE) reduction potential measured at neutral pH. At high pH (~9), hydrogen bonding in the outer coordination sphere is perturbed to allow axial glutamate ligation to Cu^(II), with a decrease in potential to 119 mV. These results highlight the role played by outer-sphere interactions, and the structural constraints they impose, in determining the redox behavior of transition metal protein cofactors.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/19735,
title ="Electron flow through metalloproteins",
author = "Gray, Harry B. and Winkler, Jay R.",
journal = "Biochimica et Biophysica Acta",
volume = "1797",
number = "9",
pages = "1563-1572",
month = "September",
year = "2010",
doi = "10.1016/j.bbabio.2010.05.001 ",
issn = "0005-2728",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20100831-100225099",
note = "© 2010 Published by Elsevier B.V.\nReceived 10 February 2010; revised 21 April 2010; accepted 3 May 2010. Available online 10 May 2010. \nOur work is supported by NIH, NSF, and the Arnold and Mabel\nBeckman Foundation.",
revision_no = "12",
abstract = "Electron transfers in photosynthesis and respiration commonly occur between metal-containing cofactors that are separated by large molecular distances. Understanding the underlying physics and chemistry of these biological electron transfer processes is the goal of much of the work in our laboratories. Employing laser flash-quench triggering methods, we have shown that 20 Å, coupling-limited Fe(II) to Ru(III) and Cu(I) to Ru(III) electron tunneling in Ru-modified cytochromes and blue copper proteins can occur on the microsecond timescale both in solutions and crystals; and, further, that analysis of these rates suggests that distant donor–acceptor electronic couplings are mediated by a combination of sigma and hydrogen bonds in folded polypeptide structures. Redox equivalents can be transferred even longer distances by multistep tunneling, often called hopping, through intervening amino acid side chains. In recent work, we have found that 20 Å hole hopping through an intervening tryptophan is several hundred-fold faster than single-step electron tunneling in a Re-modified blue copper protein.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/19276,
title ="Electronic structures, photophysical properties, and electrochemistry of ruthenium(II)(bpy)_2 pyridylimidazole complexes",
author = "Lancaster, Kyle M. and Gerken, James B.",
journal = "Coordination Chemistry Reviews",
volume = "254",
number = "15-16",
pages = "1803-1811",
month = "August",
year = "2010",
doi = "10.1016/j.ccr.2010.04.005",
issn = "0010-8545",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20100804-134627105",
note = "© 2010 Published by Elsevier B.V. \n\nReceived 20 August 2009; accepted 9 April 2010. Available online 24 April 2010. \n\nWe thank Jay Winkler and Theis Brock-Nannestad for discussions. We thank Tony Vlček for a critical reading of this manuscript. We also thank John D. Roberts and Brian Stoltz for the kind loan of reagents and equipment. This work was supported by the NSF Center for Chemical Innovation (Powering the Planet, CHE-0802907 and CHE-0947829), the Arnold and Mabel Beckman Foundation, and CCSER (Gordon and Betty Moore Foundation).",
revision_no = "15",
abstract = "The properties of Ru^(II) complexes involving the imidazole moiety are discussed. Complexes [Ru(bpy)_2(L)]^(2+) [bpy = 2,2′-bipyridine, L = 2-(2′-pyridyl)imidazole (2-pimH) and 4-(2′-pyridyl)imidazole (4-pimH)] have been synthesized and fully characterized. Reduction potentials are 0.76 V vs. Fc^+/Fc^0 for both complexes in acetonitrile solution, and the deprotonated complexes undergo irreversible electrochemical oxidation at 0.38 V vs. Fc^+/Fc^0. Density functional theory (DFT) calculations suggest that oxidation of the protonated complexes is primarily metal-based and that of the deprotonated complexes is ligand-centered. The pK_a of the 4-pimH complex was found to be 9.7 ± 0.2; the pK_a of the 2-pimH complex is 7.9 ± 0.2. Luminescence lifetimes (L = 4-pimH, 277 ns; 2-pimH, 224 ns; 4pim^−, 40 ns; 2pim^−, 34 ns in 5% methanol/water solution) combined with quantum yield data and acid–base behavior suggest that the non-coordinated imidazole nitrogen tunes deactivation pathways.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/19285,
title ="Near-IR Phosphorescence of Iridium(III) Corroles at Ambient Temperature",
author = "Palmer, Joshua H. and Durrell, Alec C.",
journal = "Journal of the American Chemical Society",
volume = "132",
number = "27",
pages = "9230-9231",
month = "July",
year = "2010",
doi = "10.1021/ja101647t ",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20100805-082356637",
note = "© 2010 American Chemical Society.\nReceived March 2, 2010.\nPublication Date (Web): June 22, 2010.\n\nThis work was supported by the NSF Center\nfor Chemical Innovation (CCI Powering the Planet, Grants CHE-\n0802907 and CHE-0947829), the US-Israel BSF, CCSER (Gordon\nand Betty Moore Foundation), and the Arnold and Mabel Beckman\nFoundation.",
revision_no = "20",
abstract = "The photophysical properties of Ir(III) corroles differ from those of phosphorescent porphyrin complexes, cyclometalated and polyimine Ir(III) compounds, and other luminescent metallocorroles. Ir(III) corrole phosphorescence is observed at ambient temperature at wavelengths much longer (>800 nm) than those of most Ir(III) phosphors. The solvatochromic behavior of Ir(III)-corrole Soret and Q absorption bands suggests that the lowest singlet excited states (S2 and S1) are substantially more polar than the ground state.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/18631,
title ="Terbium-Macrocycle Complexes as Chemical Sensors: Detection of an Aspirin Metabolite in Urine Using a Salicylurate-Specific Receptor Site",
author = "Esplin, Taran L. and Cable, Morgan L.",
journal = "Inorganic Chemistry",
volume = "49",
number = "10",
pages = "4643-4647",
month = "May",
year = "2010",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20100610-083640997",
note = "© 2010 American Chemical Society.\n\nReceived February 13, 2010.\nPublication Date (Web): April 21, 2010.\n\nThe authors thank Mona Shahgholi\nfor assistance withmass spectrometry. This research was\ncarried out at the Jet Propulsion Laboratory, California\nInstitute of Technology, under contract with the National\nAeronautic and Space Administration and was\nsponsored by the NASA Astrobiology and Planetary\nProtection Programs (A.P.), the Department of Homeland\nSecurity Chemical and Biological Research &\nDevelopment Program (A.P.), the NASA Graduate\nStudent Research Program (M.L.C.), and the NASA\nUndergraduate Student Research Program (T.L.E.).\nWork at the Beckman Institute was supported by the\nNIH, NSF, and the Arnold and Mabel Beckman Foundation\n(H.B.G.).",
revision_no = "20",
abstract = "Salicylurate (SU) is the major metabolite in urine of acetylsalicylic acid (aspirin) and can be used as a metric to monitor aspirin pharmacokinetics and as an indicator of appendicitis, anemia, and liver disease. Detection in urine and plasma currently requires solvent extraction or other sample handling prior to analysis. We present a simple method to quantify SU in urine via chelation to a terbium binary complex with the macrocycle 1,4,7,10-tetraazacyclododecane-1,7-bisacetate (DO2A). Binding of SU to form the [Tb(DO2A)(SU)]− ternary complex triggers intense luminescence under UV excitation due to an absorbance-energy transfer-emission mechanism. Here we report characterization of the [Tb(DO2A)(SU)]− ternary complex and application of this sensitized lanthanide luminescence method to quantify SU in urine samples following a low-dose aspirin regimen.\n",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/18317,
title ="Tris(hydroxypropyl)phosphine Oxide: A Chiral Three-Dimensional Material with Nonlinear Optical Properties",
author = "Durrell, Alec C. and Gray, Harry B.",
journal = "Crystal Growth and Design",
volume = "10",
number = "4",
pages = "1482-1485",
month = "April",
year = "2010",
doi = "10.1021/cg1001286 ",
issn = "1528-7483",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20100517-091141484",
note = "© 2010 American Chemical Society.\n\nReceived January 27, 2010. Publication Date (Web): March 17, 2010. \n\nWe thank Larry Henling for assistance with face indexing the crystal and George Rossman for assistance with single crystal Raman spectroscopy. This research was supported in part by the Starter Grant Award from the Spectroscopy Society of Pittsburgh (to E. C.Y.Y.) and the NSF Center for Chemical Innovation (CCI Powering the Plant, Grants CHE-0802907 and CHE-0947829 to H.B.G.).",
revision_no = "20",
abstract = "The achiral C_(3v) organic phosphine tris(hydroxypropyl)phosphine oxide (1) crystallizes in the unusual chiral hexagonal space group P6_3. The structure is highly ordered because each phosphine oxide moiety forms three hydrogen bonds with adjacent hydroxy groups from three different molecules. The properties of the crystals and the presence of hydrogen bonding interactions were investigated using single crystal Raman spectroscopy. The crystals show nonlinear optical properties and are capable of efficient second harmonic generation.\n",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/17671,
title ="Electronic Structures of Pd^(II) Dimers",
author = "Bercaw, John E. and Durrell, Alec C.",
journal = "Inorganic Chemistry",
volume = "49",
number = "4",
pages = "1801-1810",
month = "February",
year = "2010",
doi = "10.1021/ic902189g ",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20100305-091958620",
note = "© 2010 American Chemical Society.\nReceived November 5, 2009.\n\nPublication Date (Web): January 21, 2010\n\n\nWe thank George Rossman and Elizabeth\nMiura Boyd for assistance with single-crystal Raman\nspectroscopy and Larry Henling and Michael Day for assistance\nwith X-ray crystallography. This work was supported by BP\nthrough the MC2 program, the NSF Center for Chemical\nInnovation (Powering the Planet, CHE-0802907 and CHE-\n0947829), and CCSER (Gordon and Betty Moore Foundation).\nThe Bruker KAPPA APEXII X-ray diffractometer used in this\nwork was purchased via an NSF CRIF:MU CHE-0639094\naward to the California Institute of Technology.",
revision_no = "24",
abstract = "The Pd^(II) dimers [(2-phenylpyridine)Pd(μ-X)]_2 and [(2-p-tolylpyridine)Pd(μ-X)]_2 (X = OAc or TFA) do not exhibit the expected planar geometry (of approximate D_(2h) symmetry) but instead resemble an open “clamshell” in which the acetate ligands are perpendicular to the plane containing the Pd atoms and 2-arylpyridine ligands, with the Pd atoms brought quite close to one another (approximate distance 2.85 Å). The molecules adopt this unusual geometry in part because of a d^8−d^8 bonding interaction between the two Pd centers. The Pd−Pd dimers exhibit two successive one-electron oxidations: Pd^(II)−Pd^(II) to Pd^(II)−Pd^(III) to Pd^(III)−Pd^(III). Photophysical measurements reveal clear differences in the UV−visible and low-temperature fluorescence spectra between the clamshell dimers and related planar dimeric [(2-phenylpyridine)Pd(μ-Cl)]_2 and monomeric [(2-phenylpyridine)Pd(en)][Cl] (en = ethylenediamine) complexes that do not have any close Pd−Pd contacts. Density functional theory and atoms in molecules analyses confirm the presence of a Pd−Pd bonding interaction in [(2-phenylpyridine)Pd(μ-X)]_2 and show that the highest occupied molecular orbital is a d_(z2) σ* Pd−Pd antibonding orbital, while the lowest unoccupied molecular orbital and close-lying empty orbitals are mainly located on the 2-phenylpyridine rings. Computational analyses of other Pd^(II)−Pd^(II) dimers that have short Pd−Pd distances yield an orbital ordering similar to that of [(2-phenylpyridine)Pd(μ-X)]_2, but quite different from that found for d^8−d^8 dimers of Rh, Ir, and Pt. This difference in orbital ordering arises because of the unusually large energy gap between the 4d and 5p orbitals in Pd and may explain why Pd d^8−d^8 dimers do not exhibit the distinctive photophysical properties of related Rh, Ir, and Pt species.\n",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/17499,
title ="Electron tunneling through sensitizer wires bound to proteins\n",
author = "Hartings, Matthew R. and Kurnikov, Igor V.",
journal = "Coordination Chemistry Reviews",
volume = "254",
number = "3-4",
pages = "248-253",
month = "February",
year = "2010",
doi = "10.1016/j.ccr.2009.08.008",
issn = "0010-8545",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20100217-095253375",
note = "© 2009 Elsevier B.V.\n\nReceived 23 June 2009; accepted 7 August 2009. Available online 15 August 2009. \n\nInorganic Reaction Mechanisms - A Tribute to Ralph Pearson on the occasion of his 90th birthday.\nWe thank David Beratan for helpful discussions. This work\nwas supported by NIH (GM078792 to MRH and DK019038 to\nHBG and GM068461 to JRW) and NSF (CHE-0802907 to HBG and\nJRW). MR thanks the MURI program of the AFOSR and the Chemistry\nDivision of the NSF for support. This paper is dedicated\nto Ralph Pearson—friend, mentor, colleague, scientist and honest\nbroker.",
revision_no = "16",
abstract = "We report a quantitative theoretical analysis of long-range electron transfer through sensitizer wires bound in the active-site channel of cytochrome P450cam. Each sensitizer wire consists of a substrate group with high binding affinity for the enzyme active site connected to a ruthenium-diimine through a bridging aliphatic or aromatic chain. Experiments have revealed a dramatic dependence of electron transfer rates on the chemical composition of both the bridging group and the substrate. Using combined molecular dynamics simulations and electronic coupling calculations, we show that electron tunneling through perfluorinated aromatic bridges is promoted by enhanced superexchange coupling through virtual reduced states. In contrast, electron flow through aliphatic bridges occurs by hole-mediated superexchange. We have found that a small number of wire conformations with strong donor–acceptor couplings can account for the observed electron tunneling rates for sensitizer wires terminated with either ethylbenzene or adamantane. In these instances, the rate is dependent not only on electronic coupling of the donor and acceptor but also on the nuclear motion of the sensitizer wire, necessitating the calculation of average rates over the course of a molecular dynamics simulation. These calculations along with related recent findings have made it possible to analyze the results of many other sensitizer-wire experiments that in turn point to new directions in our attempts to observe reactive intermediates in the catalytic cycles of P450 and other heme enzymes.\n\n",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/17867,
title ="Kinetics of Electron Transfer Reactions of H_2-Evolving Cobalt Diglyoxime Catalysts",
author = "Dempsey, Jillian L. and Winkler, Jay R.",
journal = "Journal of the American Chemical Society",
volume = "132",
number = "3",
pages = "1060-1065",
month = "January",
year = "2010",
doi = "10.1021/ja9080259",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20100406-102958526",
note = "© 2009 American Chemical Society. Received September 21, 2009. Publication Date (Web): December 31, 2009. We thank Bruce Brunschwig, Xile Hu, Jay\nLabinger, and Jonas Peters for insightful discussions. We also thank\nEtsuko Fujita for generous assistance in obtaining in situ absorption\nspectra. This work was supported by the NSF Center for Chemical\nInnovation (Powering the Planet, CHE-0802907 and CHE-\n0947829), the Arnold and Mabel Beckman Foundation, CCSER\n(Gordon and Betty Moore Foundation), and the BP MC2 program.\nJLD is an NSF Graduate Research Fellow.",
revision_no = "23",
abstract = "Co−diglyoxime complexes catalyze H_2 evolution from protic solutions at modest overpotentials. Upon reduction to Co^I, a Co^(III)-hydride is formed by reaction with a proton donor. Two pathways for H_2 production are analyzed: one is a heterolytic route involving protonation of the hydride to release H_2 and generate Co^(III); the other is a homoytic pathway requiring association of two Co^(III)-hydrides. Rate constants and reorganization parameters were estimated from analyses of laser flash−quench kinetics experiments (Co^(III)−Co^(II) self-exchange k = 9.5 × 10^(−8) − 2.6 × 10^(−5) M^(−1) s^(−1); λ = 3.9 (±0.3) eV: Co^(II)−Co^(I) self-exchange k = 1.2 (±0.5) × 10^5 M^(−1) s^(−1); λ = 1.4 (±0.05) eV). Examination of both the barriers and driving forces associated with the two pathways indicates that the homolytic reaction (Co^(III)H + Co^(III)H → 2 Co^(II) + H_2) is favored over the route that goes through a Co^(III) intermediate (Co^(III)H + H+ → Co^(III) + H_2).",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/17228,
title ="Hydrogen Evolution Catalyzed by Cobaloximes",
author = "Dempsey, Jillian L. and Brunschwig, Bruce S.",
journal = "Accounts of Chemical Research",
volume = "42",
number = "12",
pages = "1995-2004",
month = "December",
year = "2009",
doi = "10.1021/ar900253e",
issn = "0001-4842",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20100120-084526967",
note = "© 2009 American Chemical Society. \n\nReceived on September 30, 2009. Publication Date (Web): November 23, 2009. \n\nWe thank Xile Hu, Louise Berben, Brandi Cossairt, and Jonas Peters for discussions and their important contributions to cobaloxime chemistry. This work was supported by an NSF Center for Chemical Innovation (CCI Powering the Planet, Grants CHE-0802907 and CHE-0947829), the Arnold and Mabel Beckman Foundation, CCSER (Gordon and Betty Moore Foundation), and the BP MC2 program. J.L.D. is an NSF Graduate Research Fellow.",
revision_no = "23",
abstract = "Natural photosynthesis uses sunlight to drive the conversion\nof energy-poor molecules (H_2O, CO_2) to energyrich\nones (O_2, (CH_2O)_n). Scientists are working hard to develop\nefficient artificial photosynthetic systems toward the “Holy\nGrail” of solar-driven water splitting. High on the list of challenges\nis the discovery of molecules that efficiently catalyze\nthe reduction of protons to H_2. In this Account, we report on\none promising class of molecules: cobalt complexes with diglyoxime\nligands (cobaloximes).\nChemical, electrochemical, and photochemical methods all\nhave been utilized to explore proton reduction catalysis by\ncobaloxime complexes. Reduction of a Co^(II)-diglyoxime generates\na Co^I species that reacts with a proton source to produce\na Co^(III)-hydride. Then, in a homolytic pathway, two Co^(III) hydrides\nreact in a bimolecular step to eliminate H_2.\nAlternatively, in a heterolytic pathway, protonation of the\nCo^(III)-hydride produces H_2 and Co^(III).\nA thermodynamic analysis of H_2 evolution pathways sheds\nnew light on the barriers and driving forces of the elementary\nreaction steps involved in proton reduction by Co^I-diglyoximes.\nIn combination with experimental results, this\nanalysis shows that the barriers to H_2 evolution along the heterolytic\npathway are, in most cases, substantially greater than those of the homolytic route. In particular, a formidable barrier\nis associated with Co^(III)-diglyoxime formation along the heterolytic pathway.\nOur investigations of cobaloxime-catalyzed H_2 evolution, coupled with the thermodynamic preference for a homolytic route,\nsuggest that the rate-limiting step is associated with formation of the hydride. An efficient water splitting device may require\nthe tethering of catalysts to an electrode surface in a fashion that does not inhibit association of Co^(III)-hydrides.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/17086,
title ="Type-zero copper proteins",
author = "Lancaster, Kyle M. and George, Serena DeBeer",
journal = "Nature Chemistry",
volume = "1",
number = "9",
pages = "711-715",
month = "December",
year = "2009",
doi = "10.1038/NCHEM.412 ",
issn = "1755-4330",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20100107-092654651",
note = "© 2009 Macmillan Publishers Limited. \n\nReceived 5 May 2009; Accepted 15 September 2009; Published online 1 November 2009. \n \nWe thank B. Brunschwig for assistance with Fourier transform infrared spectroscopy, Z. Gates and L. Thomas for assistance with X-ray diffraction data collection, and M. Day and J. Kaiser for discussions of crystal structural analyses. We thank E. Solomon for helpful comments on electronic structural formulations, and Y. Sheng for assistance with protein expression and purification. Stanford Synchrotron Radiation Lightsource operations are funded by DOE(BES). The Structural Molecular Biology program is supported by NIH (NCRR BMTP) (Grant Number 5 P41 RR001209)N and DOE(BER). This work was supported by NIH DK019038(HBG), Stanford GCEP, and NSF CHE-0802907. The Caltech Molecular Observatory is supported by the Gordon and Betty Moore Foundation. \n\nAuthor Contributions: K.M.L. and H.B.G. conceived and designed the experiments; K.M.L., S.D.G., and K.Y. performed the experiments; K.M.L., S.D.G., K.Y., and H.B.G. analysed the data, K.M.L., S.D.G., J.H.R., and H.B.G. co-wrote the paper.",
revision_no = "24",
abstract = "Many proteins contain copper in a range of coordination environments, where it has various biological roles, such as transferring electrons or activating dioxygen. These copper sites can be classified by their function or spectroscopic properties. Those with a single copper atom are either type 1, with an intense absorption band near 600 nm, or type 2, with weak absorption in the visible region. We have built a novel copper(ii) binding site within structurally modified Pseudomonas aeruginosa azurins that does not resemble either existing type, which we therefore call 'type zero'. X-ray crystallographic analysis shows that these sites adopt distorted tetrahedral geometries, with an unusually short Cu–O (G45 carbonyl) bond. Relatively weak absorption near 800 nm and narrow parallel hyperfine splittings in electron paramagnetic resonance spectra are the spectroscopic signatures of type zero copper. Cyclic voltammetric experiments demonstrate that the electron transfer reactivities of type-zero azurins are enhanced relative to that of the corresponding type 2 (C112D) protein.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/17023,
title ="Electron flow through proteins",
author = "Gray, Harry B. and Winkler, Jay R.",
journal = "Chemical Physics Letters",
volume = "483",
number = "1-3",
pages = "1-9",
month = "November",
year = "2009",
doi = "10.1016/j.cplett.2009.10.051",
issn = "0009-2614",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20091223-093852288",
note = "© 2009 Elsevier B.V.\n\nReceived 13 October 2009; accepted 14 October 2009. Available online 17 October 2009. \n\n\nWe thank NIH, NSF, GCEP (Stanford), CCSER (Gordon and Betty\nMoore Foundation), and the Arnold and Mabel Beckman Foundation \nfor support of our research program.",
revision_no = "16",
abstract = "Electron transfers in photosynthesis and respiration commonly occur between metal-containing cofactors that are separated by large molecular distances. Employing laser flash-quench triggering methods, we have shown that 20-Å, coupling-limited Fe^(II)–Ru^(III) and Cu^I–Ru^(III) electron tunneling in Ru-modified cytochromes and blue copper proteins can occur on the microsecond timescale both in solutions and crystals. Redox equivalents can be transferred even longer distances by multistep tunneling, often called hopping, through intervening amino acid side chains. Our work has established that 20-Å hole hopping through an intervening tryptophan is two orders of magnitude faster than single-step electron tunneling in a Re-modified blue copper protein.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/16309,
title ="Structures and Reactivity Patterns of Group 9 Metallocorroles",
author = "Palmer, Joshua H. and Mahammed, Atif",
journal = "Inorganic Chemistry",
volume = "48",
number = "19",
pages = "9308-9315",
month = "October",
year = "2009",
doi = "10.1021/ic901164r",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20091013-093451813",
note = "Copyright © 2009 American Chemical Society. \n\nReceived June 17, 2009. Publication Date (Web): September 8, 2009. \n\nThis work was supported by the Center for Chemical Innovation Grant NSF CHE-0802907, U.S.−Israel BSF (Z.G. and H.B.G.), BP, CCSER (Gordon and Betty Moore Foundation), and the Arnold and Mabel Beckman Foundation. We thank Dr. Angelo Di Bilio for help with measurements of low-temperature EPR spectra; and Drs. Lawrence M. Henling and Michael W. Day for assistance with the acquisition and analysis of crystallographic data. \n\nSupporting Information: Additional information as noted in the text. This material is available free of charge via the Internet at http://pubs.acs.org.",
revision_no = "25",
abstract = "Group 9 metallocorroles 1-M(PPh_3) and 1-M(py)_2 [M = Co(III), Rh(III), Ir(III); 1 denotes the trianion of 5,10,15-tris-pentafluorophenylcorrole] have been fully characterized by structural, spectroscopic, and electrochemical methods. Crystal structure analyses reveal that average metal−N(pyrrole) bond lengths of the bis-pyridine metal(III) complexes increase from Co (1.886 Å) to Rh (1.957 Å)/Ir (1.963 Å); and the average metal−N(pyridine) bond lengths also increase from Co (1.995 Å) to Rh (2.065 Å)/Ir (2.059 Å). Ligand affinities for 1-M(PPh_3) axial coordination sites increase dramatically in the order 1-Co(PPh_3) < 1-Rh(PPh_3) < 1-Ir(PPh_3). There is a surprising invariance in the M(+/0) reduction potentials within the five- and six-coordinate corrole series, and even between them; the average M(+/0) potential of 1-M(PPh_3) is 0.78 V vs Ag/AgCl in CH_2Cl_2 solution, whereas that of 1-M(py)_2 is 0.70 V under the same conditions. Electronic structures of one-electron-oxidized 1-M(py)_2 complexes have been assigned by analysis of electron paramagnetic resonance spectroscopic measurements: oxidation is corrole-centered for 1-Co(py)_2 (g = 2.008) and 1-Rh(py)_2 (g = 2.003), and metal-centered for 1-Ir(tma)_2 (g_(zz) = 2.489, g_(yy) = 2.010, g_(xx) = 1.884, g_(av) = 2.128) and 1-Ir(py)_2 (g_(zz) = 2.401, g_(yy) = 2.000, g_(xx) = 1.937, g_(av) = 2.113).",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/15805,
title ="Relaxation Dynamics of Pseudomonas aeruginosa Re^I(C)O_3(α-diimine)(HisX)^+ (X=83, 107, 109, 124, 126)Cu-^(II) Azurins",
author = "Blanco-Rodríguez, Ana María and Busby, Michael",
journal = "Journal of the American Chemical Society",
volume = "131",
number = "33",
pages = "11788-11800",
month = "August",
year = "2009",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20090911-153601363",
note = "Copyright © 2009 American Chemical Society. \n\nReceived April 10, 2009; Publication Date (Web): July 29, 2009. \n\nThis work was supported by EPSRC (EP/E060544), STFC (CMSD43), COST D35, Ministry of Education of the Czech Republic (OC09043 and LC06063), NSF (CHE-0802907 and CHE-0749997), and NIH (DK019038). \n\nSupporting Information: Tables of experimentally determined orientation of the histidine imidazole ligand relative to the Re(CO)_3(phen) unit in the five proteins, DFT-calculated frontier Kohn−Sham orbitals and electronic transitions of Re(Etim) in two conformations, comparison of calculated and experimental ground- and excited-state ν(CO) IR wavenumbers of Re(Etim), and results of stretched-exponential fitting of the A′(1) ν(CO) band shift kinetics at different concentrations. Figures of DFT-calculated structures of Re(Etim) in several ground- and excited-state conformations and time traces of the peak energy of the A′(1) ν(CO) band of 107-dmp, 124-phen, and 126-phen measured at different concentrations. Full text of ref 33 (Gaussian 03 software) is provided. This material is available free of charge via the Internet at http://pubs.acs.org.",
revision_no = "25",
abstract = "Photoinduced relaxation processes of five structurally characterized Pseudomonas aeruginosa Re^I(CO)_3(α-diimine)(HisX) (X = 83, 107, 109, 124, 126)Cu^(II) azurins have been investigated by time-resolved (ps−ns) IR spectroscopy and emission spectroscopy. Crystal structures reveal the presence of Re-azurin dimers and trimers that in two cases (X = 107, 124) involve van der Waals interactions between interdigitated diimine aromatic rings. Time-dependent emission anisotropy measurements confirm that the proteins aggregate in mM solutions (D2O, KPi buffer, pD = 7.1). Excited-state DFT calculations show that extensive charge redistribution in the ReI(CO)_3 → diimine ^3MLCT state occurs: excitation of this ^3MLCT state triggers several relaxation processes in Re-azurins whose kinetics strongly depend on the location of the metallolabel on the protein surface. Relaxation is manifested by dynamic blue shifts of excited-state ν(CO) IR bands that occur with triexponential kinetics: intramolecular vibrational redistribution together with vibrational and solvent relaxation give rise to subps, 2, and 8−20 ps components, while the ~10^2 ps kinetics are attributed to displacement (reorientation) of the Re^I(CO)_3(phen)(im) unit relative to the peptide chain, which optimizes Coulombic interactions of the Re^I excited-state electron density with solvated peptide groups. Evidence also suggests that additional segmental movements of Re-bearing β-strands occur without perturbing the reaction field or interactions with the peptide. Our work demonstrates that time-resolved IR spectroscopy and emission anisotropy of Re^I carbonyl−diimine complexes are powerful probes of molecular dynamics at or around the surfaces of proteins and protein−protein interfacial regions.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/15341,
title ="Deamidation of α-synuclein",
author = "Robinson, Noah E. and Robinson, Matthew L.",
journal = "Protein Science",
volume = "18",
number = "8",
pages = "1766-1773",
month = "August",
year = "2009",
doi = "10.1002/pro.183",
issn = "0961-8368",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20090826-113104565",
note = "© 2009 Wiley.\n\nReceived: 19 April 2009; Revised: 27 May 2009; Accepted: 2 June 2009.\n\nGrant sponsors: John Kinsman Foundation, Morse Foundation,\nEllison Medical Foundation.",
revision_no = "15",
abstract = "The rates of deamidation of α-synuclein and single Asn residues in 13 Asn-sequence mutants have been measured for 5 × 10^(-5)M protein in both the absence and presence of 10^(-2)M sodium dodecyl sulfate (SDS). In the course of these experiments, 370 quantitative protein deamidation measurements were performed and 37 deamidation rates were determined by ion cyclotron resonance Fourier transform mass spectrometry, using an improved whole protein isotopic envelope method and a mass defect method with both enzymatic and collision-induced fragmentation. The measured deamidation index of α-synuclein was found to be 0.23 for an overall deamidation half-time of 23 days, without or with SDS micelles, owing primarily to the deamidation of Asn(103) and Asn(122). Deamidation rates of 15 Asn residues in the wild-type and mutant proteins were found to be primary sequence controlled without SDS. However, the presence of SDS micelles slowed the deamidation rates of nine N-terminal region Asn residues, caused by the known three-dimensional structures induced through protein binding to SDS micelles.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/14958,
title ="Detection of bacterial spores with lanthanide-macrocycle binary complexes",
author = "Cable, Morgan L. and Kirby, James P.",
journal = "Journal of the American Chemical Society",
volume = "131",
number = "27",
pages = "9562-9570",
month = "July",
year = "2009",
doi = "10.1021/ja902291v",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20090811-114903763",
note = "© 2009 American Chemical Society.\nPublished In Issue: July 15, 2009; Article ASAP:\nJune 19, 2009; Received: March 28, 2009.\nThe authors thank Larry Henling and Mike Day for crystallographic analysis and Kyle Lancaster for assistance\nwith mass spectrometry. The research described in this paper was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautic and Space Administration and was sponsored by NASA’s Astrobiology and Planetary Protection Programs (A.P., J.P.K.), the Department of Homeland Security’s Chemical and Biological Research & Development\nProgram (A.P.), the National Defense Science and Engineering\nGraduate Fellowship Program (M.L.C.), the NASA Graduate\nStudent Research Program (M.L.C.), the AmGen Scholars\nProgram (D.J.L.), and the Caltech Summer Undergraduate Research Fellowship Program (D.J.L., M.J.M.). Work at the Beckman Institute was supported by the NIH, NSF, and the Arnold and Mabel Beckman Foundation (H.B.G.).\nSupporting Information Available: Crystallographic data\n(CIF) of the Ln(DO2A)(DPA)- complexes, where Ln ) Sm,\nEu, Tb, or Dy; derivation of model for Ln(DPA) binding affinity;\nthermal ellipsoid plots of Dy(DO2A)(DPA)- ternary complex\nand Sm coordination geometry; normalized excitation and\nabsorption spectra of Ln(DO2A)(DPA)- complexes; calculation\nof quantum yields and molar extinction coefficients for\nLn(DO2A)(DPA)- complexes; Ka′ values of Tb(DO2A)(DPA)-\ncomplex over time; emission spectra of various terbium,\neuropium, and samarium complexes; emission intensity variation\nin Tb(DO2A)(DPA)+ due to interference from common cations\nand anions; ion competition experiments with phosphate, sulfate,\npotassium, and carbonate; enthalpic and entropic components\nfor Tb(DO2A)(DPA)- and Eu(DO2A)(DPA)-; time courses of\nDPA binding to Tb(DO2A)+ at various pH values; and\ncalculation of signal-to-noise ratio for the bacterial spore\ndetection study. This material is available free of charge via\nthe Internet at http://pubs.acs.org.",
revision_no = "41",
abstract = "The detection of bacterial spores via dipicolinate-triggered lanthanide luminescence has been improved in terms of detection limit, stability, and susceptibility to interferents by use of lanthanide−macrocycle binary complexes. Specifically, we compared the effectiveness of Sm, Eu, Tb, and Dy complexes with the macrocycle 1,4,7,10-tetraazacyclododecane-1,7-diacetate (DO2A) to the corresponding lanthanide aquo ions. The Ln(DO2A)^+ binary complexes bind dipicolinic acid (DPA), a major constituent of bacterial spores, with greater affinity and demonstrate significant improvement in bacterial spore detection. Of the four luminescent lanthanides studied, the terbium complex exhibits the greatest dipicolinate binding affinity (100-fold greater than Tb^(3+) alone, and 10-fold greater than other Ln(DO2A)^+ complexes) and highest quantum yield. Moreover, the inclusion of DO2A extends the pH range over which Tb−DPA coordination is stable, reduces the interference of calcium ions nearly 5-fold, and mitigates phosphate interference 1000-fold compared to free terbium alone. In addition, detection of Bacillus atrophaeus bacterial spores was improved by the use of Tb(DO2A)^+, yielding a 3-fold increase in the signal-to-noise ratio over Tb^(3+). Out of the eight cases investigated, the Tb(DO2A)^+ binary complex is best for the detection of bacterial spores.\n",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/15628,
title ="Nanosecond photoreduction of inducible nitric oxide synthase by a Ru-diimine electron tunneling wire bound distant from the active site",
author = "Whited, Charlotte A. and Belliston-Bittner, Wendy",
journal = "Journal of Inorganic Biochemistry",
volume = "103",
number = "6",
pages = "906-911",
month = "June",
year = "2009",
doi = "10.1016/j.jinorgbio.2009.04.001",
issn = "0162-0134",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20090904-135737718",
note = "© 2009 Elsevier. \n\nReceived 3 December 2008; revised 1 April 2009; accepted 2 April 2009. Available online 17 April 2009. \n\nWe thank Michael Marletta for the generous gift of protein reagents and for assistance with the iNOS purification protocol. This work was supported by NIH (DK19038 (H.B.G); GM070868 (H.B.G); GM068461 (J.R.W)), by the Fannie and John Hertz Foundation (A.R.D), the Ellison Medical Foundation (Senior Scholar Award in Aging to H.B.G), a NSF graduate research fellowship (C.A.W), and the Arnold and Mabel Beckman Foundation. \n\nSupplementary data associated with this article can be found, in the online version, at doi:10.1016/j.jinorgbio.2009.04.001.",
revision_no = "20",
abstract = "A Ru-diimine wire, [(4,4′,5,5′-tetramethylbipyridine)_2Ru(F_9bp)]^(2+) (tmRu-F_9bp, where F_9bp is 4-methyl-4′-methylperfluorobiphenylbipyridine), binds tightly to the oxidase domain of inducible nitric oxide synthase (iNOSoxy). The binding of tmRu-F_9bp is independent of tetrahydrobiopterin, arginine, and imidazole, indicating that the wire resides on the surface of the enzyme, distant from the active-site heme. Photoreduction of an imidazole-bound active-site heme iron in the enzyme-wire conjugate (k_(ET) = 2(1) × 10^7 s^(−1)) is fully seven orders of magnitude faster than the in vivo process.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/15009,
title ="Folding energy landscape of cytochrome cb_(562) \n \n",
author = "Kimura, Tetsunari and Lee, Jennifer C.",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "106",
number = "19",
pages = "7834-7839",
month = "May",
year = "2009",
doi = "10.1073/pnas.0902562106",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20090813-110702430",
note = "© 2009 by the National Academy of Sciences.\nContributed by Harry B. Gray, March 9, 2009 (received for review February 11, 2009). Published online before print April 28, 2009, doi: 10.1073/pnas.0902562106. \nAuthor contributions: T.K., J.C.L., H.B.G., and J.R.W. designed research; T.K. and J.C.L.\nperformed research; T.K., J.C.L., H.B.G., and J.R.W. analyzed data; and T.K., J.C.L., H.B.G.,\nand J.R.W. wrote the paper.\nWe thank Professor Linda Thöny-Meyer (Eidgenössische Technische Hochschule Zürich, Zürich, Switzerland) for the ccm plasmid pEC86. We also thank Ekaterina V. Pletneva for many helpful discussions. This work was supported by National Institutes of Health Grants GM068461 (to J.R.W.) and DK019038 (to H.B.G.) and by an Arnold and Mabel Beckman Foundation Senior Research Fellowship (to J.C.L.). T.K. was supported by Japan Society for the Promotion of Science Postdoctoral Fellowships for Young Scientists and for Research Abroad. \n\nThe authors declare no conflict of interest.",
revision_no = "22",
abstract = "Cytochrome cb_(562) is a variant of an Escherichia coli four-helix bundle b-type heme protein in which the porphyrin prosthetic group is covalently ligated to the polypeptide near the terminus of helix 4. Studies from other laboratories have shown that the apoprotein folds rapidly without the formation of intermediates, whereas the holoprotein loses heme before native structure can be attained. Time-resolved fluorescence energy transfer (TRFET) measurements of cytochrome cb_(562) refolding triggered using an ultrafast continuous-flow mixer (150 μs dead time) reveal that heme attachment to the polypeptide does not interfere with rapid formation of the native structure. Analyses of the TRFET data produce distributions of Trp-59–heme distances in the protein before, during, and after refolding. Characterization of the moments and time evolution of these distributions provides compelling evidence for a refolding mechanism that does not involve significant populations of intermediates. These observations suggest that the cytochrome b_(562) folding energy landscape is minimally frustrated and able to tolerate the introduction of substantial perturbations (i.e., the heme prosthetic group) without the formation of deep misfolded traps. \n\n",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/14219,
title ="Tumor detection and elimination by a targeted gallium corrole",
author = "Agadjanian, Hasmik and Ma, Jun",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "106",
number = "15",
pages = "6105-6110",
month = "April",
year = "2009",
doi = "10.1073/pnas.0901531106",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20090514-144240338",
note = "© 2009 by the National Academy of Sciences.\nContributed by Harry B. Gray, February 15, 2009 (received for review December 18, 2008).\nWe thank Krishnan Ramanujan for helpful feedback\nand critical review of this work; Kolja Wawrowsky (Cedars-Sinai Medical\nCenter Confocal Core Facility) and Sarah Hamm-Alvarez and Jiansong Xie\n(University of Southern California Department of Pharmaceutical Sciences) for\nassistance with microscopic imaging; and Renata Stripecke and Emmanuelle\nFaure-Kumar (UCLA Vector Core) for provision of adenovirus and lentivirus\nvectors. This work was supported by National Institutes of Health (NIH) Grants\nR21 CA116014 and R01 CA102126, Department of Defense Grant BC050662,\nSusan G. Komen Breast Cancer Foundation Grant BCTR0201194, and a Donna\nand Jesse Garber Award (all to L.K.M.-K.), and by the U.S. Navy Bureau of\nMedicine and Surgery (D.L.F.). Work performed at the Technion-Israel Institute\nof Technology was supported by grants from the Gurwin and Binational\nScience foundations (to Z.G.). Research at California Institute of Technology\nwas supported by grants from NIH and the National Science Foundation (to\nH.B.G.).",
revision_no = "22",
abstract = "Sulfonated gallium(III) corroles are intensely fluorescent macrocyclic compounds that spontaneously assemble with carrier proteins to undergo cell entry. We report in vivo imaging and therapeutic efficacy of a tumor-targeted corrole noncovalently assembled with a heregulin-modified protein directed at the human epidermal growth factor receptor (HER). Systemic delivery of this protein-corrole complex results in tumor accumulation, which can be visualized in vivo owing to intensely red corrole fluorescence. Targeted delivery in vivo leads to tumor cell death while normal tissue is spared. These findings contrast with the effects of doxorubicin, which can elicit cardiac damage during therapy and required direct intratumoral injection to yield similar levels of tumor shrinkage compared with the systemically delivered corrole. The targeted complex ablated tumors at >5 times a lower dose than untargeted systemic doxorubicin, and the corrole did not damage heart tissue. Complexes remained intact in serum and the carrier protein elicited no detectable immunogenicity. The sulfonated gallium(III) corrole functions both for tumor detection and intervention with safety and targeting advantages over standard chemotherapeutic agents.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/15445,
title ="Powering the planet with solar fuel",
author = "Gray, Harry B.",
journal = "Nature Chemistry",
volume = "1",
number = "1",
pages = "7",
month = "April",
year = "2009",
issn = "1755-4330",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20090828-231032888",
note = "© 2009 Nature Publishing Group. \n\nI would like to thank my colleagues Jay R. Winkler, Bruce S. Brunschwig and Douglas L. Smith for their contributions to this article. \n\nCorrected: 19 March 2009.",
revision_no = "13",
abstract = "With energy swiftly rising to the top of the world's agenda, Harry B. Gray at the California Institute of Technology looks at how chemistry can help to harness the power of the Sun to meet the world's energy needs.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/14713,
title ="Obituary-Fred Basolo (1920–2007) \n",
author = "Kauffman, George B. and Kauffman, Laurie M.",
journal = "Inorganica Chimica Acta",
volume = "362",
number = "4",
pages = "1396-1397",
month = "March",
year = "2009",
issn = "0020-1693",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20090729-084449319",
note = "© 2009 Elsevier.\nAvailable online 12 February 2009. \n\nWe are greatly indebted to Robert J. Angelici, John L. Burmeister,\nAlison Butler, James P. Collman, Alvin L. Crumbliss, James A. Ibers,\nRonald C. Johnson, Kazuo Nakamoto, Thomas V. O’Halloran, Ralph\nG. Pearson, David H. Petering, Anthony J. Poë, Kenneth N. Raymond,\nWilliam C. Trogler, and Andrew Wojcicki for sharing Basolo memorabilia\nwith us.",
revision_no = "9",
abstract = "No abstract.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/15723,
title ="High-Potential C112D/M121X (X = M, E, H, L) Pseudomonas aeruginosa Azurins",
author = "Lancaster, Kyle M. and Yokoyama, Keiko",
journal = "Inorganic Chemistry",
volume = "48",
number = "4",
pages = "1278-1280",
month = "February",
year = "2009",
doi = "10.1021/ic802322e",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20090910-101427356",
note = "© 2009 American Chemical Society. Received December 3, 2008.\nWe thank Yuling Sheng and Matthew\nR. Hartings for assistance and Israel Pecht for useful\ndiscussions. This work was supported by the NSF (Grant\nCHE-0553150 to H.B.G. and J.R.W.; graduate fellowship\nto K.M.L.), GCEP (Stanford), and NIH (Grant DK019038\nto H.B.G.)",
revision_no = "26",
abstract = "Site-directed mutagenesis of Pseudomonas aeruginosa azurin\nC112D at the M121 position has afforded a series of proteins with\nelevated Cu^(II/I) reduction potentials relative to the CuII aquo ion.\nThe high potential and low axial hyperfine splitting (Cu^(II) electron\nparamagnetic resonance A|) of the C112D/M121L protein are\nremarkably similar to features normally associated with type 1\ncopper centers.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/13254,
title ="Electrostatic effects on funneled landscapes and structural diversity in denatured protein ensembles",
author = "Weinkam, Patrick and Pletneva, Ekaterina V.",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "106",
number = "6",
pages = "1796-1801",
month = "February",
year = "2009",
doi = "10.1073/pnas.0813120106",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:WEIpnas09",
note = "© 2009 by The National Academy of Sciences of the USA. \n\nContributed by Harry B. Gray, December 23, 2008 (sent for review December 3, 2008). Published online before print January 30, 2009, doi: 10.1073/pnas.0813120106 \n\nWe thank Garyk Papoian for advice on making the funnel images. This work was supported by National Institutes of Health Grants GM044557 (to P.G.W.), GM068461 (to J.R.W.), and DK019038 (to H.B.G.) and by National Science Foundation Center for Theoretical Biological Physics Grant PHY-0822283. \n\nAuthor contributions: P.W. and P.G.W. designed research; P.W. performed research; P.W., E.V.P., H.B.G., J.R.W., and P.G.W. contributed new reagents/analytic tools; P.W., E.V.P., H.B.G., J.R.W., and P.G.W. analyzed data; and P.W., E.V.P., H.B.G., J.R.W., and P.G.W. wrote the paper. \n\nThe authors declare no conflict of interest.",
revision_no = "21",
abstract = "The denatured state of proteins is heterogeneous and susceptible to general hydrophobic and electrostatic forces, but to what extent does the funneled nature of protein energy landscapes play a role in the unfolded ensemble? We simulate the denatured ensemble of cytochrome c using a series of models. The models pinpoint the efficacy of incorporating energetic funnels toward the native state in contrast with models having no native structure-seeking tendency. These models also contain varying strengths of electrostatic effects and hydrophobic collapse. The simulations based on these models are compared with experimental distributions for the distances between a fluorescent donor and the heme acceptor that were extracted from time-resolved fluorescence energy transfer experiments on cytochrome c. Comparing simulations to detailed experimental data on several labeling sites allows us to quantify the dominant forces in denatured protein ensembles.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/13192,
title ="Synchronous vs Asynchronous Chain Motion in α-Synuclein Contact Dynamics",
author = "Urie, Kristopher G. and Angulo, David",
journal = "Journal of Physical Chemistry B",
volume = "113",
number = "2",
pages = "522-530",
month = "January",
year = "2009",
doi = "10.1021/jp806727e",
issn = "1520-6106",
url = "https://resolver.caltech.edu/CaltechAUTHORS:URIjpcb09",
note = "© 2008 American Chemical Society. \n\nReceived: July 29, 2008; Revised Manuscript Received: October 10, 2008. Publication Date (Web): December 19, 2008. \n\nThis research was supported by grants from the National Institutes of Health (GM068461 to J.R.W.; DK19038 to H.B.G.) and the Ellison Medical Foundation (Senior Scholar Award in Aging to H.B.G.), and by the Intramural Research Program of the National Institutes of Health, the National Heart, Lung, and Blood Institute (J.C.L.).",
revision_no = "20",
abstract = "α-Synuclein (α-syn) is an intrinsically unstructured 140-residue neuronal protein of uncertain function that is implicated in the etiology of Parkinson’s disease. Tertiary contact formation rate constants in α-syn, determined from diffusion-limited electron-transfer kinetics measurements, are poorly approximated by simple random polymer theory. One source of the discrepancy between theory and experiment may be that interior-loop formation rates are not well approximated by end-to-end contact dynamics models. We have addressed this issue with Monte Carlo simulations to model asynchronous and synchronous motion of contacting sites in a random polymer. These simulations suggest that a dynamical drag effect may slow interior-loop formation rates by about a factor of 2 in comparison to end-to-end loops of comparable size. The additional deviations from random coil behavior in α-syn likely arise from clustering of hydrophobic residues in the disordered polypeptide.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/11731,
title ="Spermine Binding to Parkinson’s Protein α-Synuclein and Its Disease-Related A30P and A53T Mutants",
author = "Grabenauer, Megan and Bernstein, Summer L.",
journal = "Journal of Physical Chemistry B",
volume = "112",
number = "35",
pages = "11147-11154",
month = "September",
year = "2008",
doi = "10.1021/jp801175w",
issn = "1520-6106",
url = "https://resolver.caltech.edu/CaltechAUTHORS:GRAjpcb08",
note = "Copyright © 2008 American Chemical Society. \n\nReceived: February 8, 2008; Revised Manuscript Received: June 11, 2008. Web Release Date: August 9, 2008. \n\nWe thank Professor Joe Loo for suggesting the experiments with spermine and Dr. Catherine J. Carpenter for help with preparation of the figures. Support from the National Science Foundation (grant CHE-0503728 (M.T.B.)), National Institutes of Health (grant GM068461 (J.R.W.)), the Ellison Medical Foundation (Senior Scholar Award in Aging to H.B.G.), and the Arnold and Mabel Beckman Foundation (J.C.L.) are gratefully acknowledged.",
revision_no = "22",
abstract = "Aggregation of α-synuclein (α-syn), a protein implicated in Parkinson’s disease (PD), is believed to progress through formation of a partially folded intermediate. Using nanoelectrospray ionization (nano-ESI) mass spectrometry combined with ion mobility measurements we found evidence for a highly compact partially folded family of structures for α-syn and its disease-related A53T mutant with net charges of −6, −7, and −8. For the other early onset PD mutant, A30P, this highly compact population was only evident when the protein had a net charge of −6. When bound to spermine near physiologic pH, all three proteins underwent a charge reduction from the favored solution charge state of −10 to a net charge of −6. This charge reduction is accompanied by a dramatic size reduction of about a factor of 2 (cross section of 2600 Å^2 (−10 charge state) down to 1430 Å^2 (−6 charge state)). We conclude that spermine increases the aggregation rate of α-syn by inducing a collapsed conformation, which then proceeds to form aggregates.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/13376,
title ="Probing the heme-thiolate oxygenase domain of inducible nitric oxide synthase with Ru(II) and Re(I) electron tunneling wires",
author = "Whited, Charlotte A. and Belliston-Bittner, Wendy",
journal = "Journal of Porphyrins and Phthalocyanines",
volume = "12",
number = "9",
pages = "971-978",
month = "September",
year = "2008",
doi = "10.1142/S1088424608000352",
issn = "1088-4246",
url = "https://resolver.caltech.edu/CaltechAUTHORS:WHIjpp08",
note = "© 2008 Society of Porphyrins & Phthalocyanines.\nReceived 19 September 2008.\n\nAccepted 28 September 2008.\n\nOur work is supported by the NIH (DK 19038 and\nGM070868 to HBG; GM068461 to JRW); the Ellison\nMedical Foundation (Senior Scholar Award in Aging\nto HBG); an NSF graduate fellowship (CAW); the\nFannie and John Hertz Foundation (ARO); the Parsons\nFoundation (WBB); and the Arnold and Mabel\nBeckman Foundation.",
revision_no = "22",
abstract = "Nitric oxide synthase (NOS) catalyzes the production of nitric oxide from L-arginine and dioxygen at a thiolate-ligated heme active site. Although many of the reaction intermediates are as yet unidentified, it is well established that the catalytic cycle begins with substrate binding and rate-limiting electron transfer to the heme. Here, we show that Ru(II)-diimine and Re(I)-diimine electron tunneling wires trigger nanosecond photoreduction of the active-site heme in the enzyme. Very rapid generation of a reduced thiolate-ligated heme opens the way for direct observation of short-lived intermediates in the NOS reaction cycle. ",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/71722,
title ="Spectroscopic Analysis of Ligand Binding to Lanthanide−Macrocycle Platforms",
author = "Kirby, James P. and Cable, Morgan L.",
journal = "Analytical Chemistry",
volume = "80",
number = "15",
pages = "5750-5754",
month = "August",
year = "2008",
doi = "10.1021/ac800154d",
issn = "0003-2700",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20161103-135143734",
note = "© 2008 American Chemical Society. \n\nReceived for review January 22, 2008. Accepted April 18, 2008. Publication Date (Web): June 26, 2008. \n\nThe authors thank Larry Henling and Mike Day for assistance. M.L.C. acknowledges support from the National Defense Science and Engineering Graduate (NDSEG) Fellowship Program. D.J.L. was supported by the Amgen Fellowship Program. Work at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration was supported by NASA’s Astrobiology and Planetary Protection Programs and Department of Homeland Security’s Chemical and Biological Research & Development Program. Work at the Beckman Institute was supported by NSF and the Arnold and Mabel Beckman Foundation.",
revision_no = "12",
abstract = "A high-affinity, binary Eu^(3+) receptor site consisting of 1,4,7,10-tetraazacyclododecane-1,7-diacetate (DO2A) was constructed with the goal of improving the detection of dipicolinic acid (DPA), a major component of bacterial spores. Ternary Eu(DO2A)(DPA)− complex solutions (1.0 µM crystallographically characterized TBA·Eu(DO2A)(DPA)) were titrated with EuCl_3 (1.0 nM−1.0 mM); increased Eu^(3+) concentration resulted in a shift in equilibrium population from Eu(DO2A)(DPA)^− to Eu(DO2A)^+ and Eu(DPA)^+, which was monitored via the ligand field sensitive ^5D_0 → ^7F_3 transition (λ_(em) = 670−700 nm) using luminescence spectroscopy. A best fit of luminescence intensity titration data to a two-state thermodynamic model yielded the competition equilibrium constant (K_c), which in conjunction with independent measurement of the Eu(DPA)^+ formation constant (K_a) allowed calculation of the ternary complex formation constant (K_a^′). With this binding affinity by competition (BAC) assay, we determined that K_a^′ = 10^(8.21) M^(−1), which is ∼1 order of magnitude greater than the formation of Eu(DPA)^+. In general, the BAC assay can be employed to determine ligand binding constants of systems where the lanthanide platform (usually a binary complex) is stable and the ligand bound versus unbound states can be spectroscopically distinguished.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/51885,
title ="Tryptophan-Accelerated Electron Flow Through Proteins",
author = "Shih, Crystal and Museth, Anna Katrine",
journal = "Science",
volume = "320",
number = "5884",
pages = "1760-1762",
month = "June",
year = "2008",
doi = "10.1126/science.1158241",
issn = "0036-8075",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20141118-091949973",
note = "© 2008 American Association for the Advancement of Science.\n\nReceived 24 March 2008; accepted 21 May 2008.\n\nWe thank C. Grădinaru, B. Leigh, and J. Miller for\nassistance in the early stages of this work. Supported\nby NIH (DK19038 to H.B.G.); NSF (CHE-0749997 to\nB.R.C., and CHE-0533150 to H.B.G. and J.R.W.); the\nFoundation BLANCEFLOR Boncompagni-Ludovisi,\nnée Bildt; STINT, the Swedish Foundation for\nInternational Cooperation in Research and Higher\nEducation (MLAA); the Engineering and Physical\nSciences Research Council; Queen Mary, University\nof London; and the Science and Technology Facilities\nCouncil (CMSD43). The coordinates of the ReI(CO)3\n(dmp)(H124)|(W122)|AzCuII crystal structure have\nbeen deposited in the Protein Data Bank (accession\nnumber 2I7O).",
revision_no = "18",
abstract = "Energy flow in biological structures often requires submillisecond charge transport over long molecular distances. Kinetics modeling suggests that charge-transfer rates can be greatly enhanced by multistep electron tunneling in which redox-active amino acid side chains act as intermediate donors or acceptors. We report transient optical and infrared spectroscopic experiments that quantify the extent to which an intervening tryptophan residue can facilitate electron transfer between distant metal redox centers in a mutant Pseudomonas aeruginosa azurin. CuI oxidation by a photoexcited ReI-diimine at position 124 on a histidine(124)-glycine(123)-tryptophan(122)-methionine(121) β strand occurs in a few nanoseconds, fully two orders of magnitude faster than documented for single-step electron tunneling at a 19 angstrom donor-acceptor distance.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77331,
title ="Enantiomer-Specific Binding of Ruthenium(II) Molecular Wires by the Amine Oxidase of Arthrobacter globiformis",
author = "Langley, David B. and Brown, Doreen E.",
journal = "Journal of the American Chemical Society",
volume = "130",
number = "25",
pages = "8069-8078",
month = "June",
year = "2008",
doi = "10.1021/ja801289f",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170510-090742106",
note = "© 2008 American Chemical Society. \n\nReceived February 26, 2008. Publication Date (Web): May 29, 2008. \n\nWe thank Nick Halpern-Manners and Alexander Dunn for assistance in the early stages of this work. The work was supported by the National Institutes of Health (DK19038 to H.B.G, GM27659 to D.M.D.) and the Australian Research Council (DP0208320 to J.M.G. and H.C.F.).",
revision_no = "17",
abstract = "The copper amine oxidase from Arthrobacter globiformis (AGAO) is reversibly inhibited by molecular wires comprising a Ru(II) complex head group and an aromatic tail group joined by an alkane linker. The crystal structures of a series of Ru(II)-wire−AGAO complexes differing with respect to the length of the alkane linker have been determined. All wires lie in the AGAO active-site channel, with their aromatic tail group in contact with the trihydroxyphenylalanine quinone (TPQ) cofactor of the enzyme. The TPQ cofactor is consistently in its active (“off-Cu”) conformation, and the side chain of the so-called “gate” residue Tyr296 is consistently in the “gate-open” conformation. Among the wires tested, the most stable complex is produced when the wire has a −(CH_2)_4− linker. In this complex, the Ru(II)(phen)(bpy)_2 head group is level with the protein molecular surface. Crystal structures of AGAO in complex with optically pure forms of the C4 wire show that the linker and head group in the two enantiomers occupy slightly different positions in the active-site channel. Both the Λ and Δ isomers are effective competitive inhibitors of amine oxidation. Remarkably, inhibition by the C4 wire shows a high degree of selectivity for AGAO in comparison with other copper-containing amine oxidases.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77417,
title ="Iridium Corroles",
author = "Palmer, Joshua H. and Day, Michael W.",
journal = "Journal of the American Chemical Society",
volume = "130",
number = "25",
pages = "7786-7787",
month = "June",
year = "2008",
doi = "10.1021/ja801049t",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170512-130427477",
note = "© 2008 American Chemical Society. \n\nReceived February 11, 2008. Publication Date (Web): May 31, 2008. \n\nThis work was supported by the US-Israel BSF (Z.G. and H.B.G.), BP, NSF, CCSER (Gordon and Betty Moore Foundation), and the Arnold and Mabel Beckman Foundation (H.B.G.).",
revision_no = "18",
abstract = "This work reports the synthesis and full characterization of 5,10,15-tris-pentafluorophenylcorrolato-iridium(III) bis-trimethylamine 1 and its octabromo derivative 2. The corrole is planar in both cases (the mean deviation from the plane is as low as 0.0371 Å for 1 and 0.0325 Å for 2), the UV−vis spectra display a split Soret band with a shoulder attributable to an MLCT transition, and cyclic voltammetry reveals that the iridium(II) oxidation state cannot be accessed, while the oxidation to formal iridium(IV) complexes is achieved at much lower potentials than in other coordination environments.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/74809,
title ="Copper(II) Binding to α-Synuclein, the Parkinson’s Protein",
author = "Lee, Jennifer C. and Gray, Harry B.",
journal = "Journal of the American Chemical Society",
volume = "130",
number = "22",
pages = "6898-6899",
month = "June",
year = "2008",
doi = "10.1021/ja711415b",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170306-150523974",
note = "© 2008 American Chemical Society. ACS AuthorChoice. \n\nReceived December 26, 2007; Publication Date (Web): May 9, 2008. \n\nSupported by the Intramural Research Program of the National Institutes of Health, the National Heart, Lung, and Blood Institute (JCL), and grants from the Ellison Medical Foundation (Senior Scholar Award in Aging to H.B.G.) and NIH (GM068461 to J.R.W.; DK19038 to H.B.G.). Initial work was supported by a Beckman Senior Research Fellowship (J.C.L.).",
revision_no = "16",
abstract = "Variations in tryptophan fluorescence intensities confirm that copper(II) interacts with α-synuclein, a protein implicated in Parkinson’s disease. Trp4 fluorescence decay kinetics measured for the F4W protein show that Cu(II) binds tightly (K_d ∼ 100 nM) near the N-terminus at pH 7. Work on a F4W/H50S mutant indicates that a histidine imidazole is not a ligand in this high-affinity site.",
}
@book_section {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/84667,
title ="Large field of view scanning fluorescence lifetime imaging system for multimode optical imaging of small animals\n",
author = "Hwang, Jae Youn and Agadjanian, Hasmik",
number = "6859",
pages = "Art. No. 68590G",
month = "March",
year = "2008",
doi = "10.1117/12.769305",
issn = "0277786X",
isbn = "978-0-8194-7034-8",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180205-090030536",
note = "© 2008 Society of Photo-Optical Instrumentation Engineers (SPIE). \n\nWe thank our colleagues, and particularly Dr. V K. Ramanujan and A. Nowatzyk for their contributions, and useful discussions. This research was supported in part by the US Navy Bureau of Medicine and Surgery.",
revision_no = "11",
abstract = "We describe a scanning fluorescence lifetime imaging (SFLIM) system that provides a large field of view (LFOV), using a femtosecond (fs) pulsed laser, for multi-mode optical imaging of small animals. Fluorescence lifetime imaging (FLIM) can be a useful optical method to distinguish between fluorophores inside small animals. However, difficulty arises when LFOV is required in FLIM using a fs pulsed laser for the excitation of the fluorophores at low wavelengths (<500nm), primarily because the field of view of the pulsed blue excitation light generated from the second harmonic of the fs pulsed light is limited to about a centimeter in diameter due to the severe scattering and absorption of the light inside tissues. Here, we choose a scanning method in order to acquire a FLIM image with LFOV as one alternative. In the SFLIM system, we used a conventional cooled CCD camera coupled to an ultra-fast time-gated intensifier, a tunable femtosecond laser for the excitation of fluorophores, and an x-y moving stage for scanning. Images acquired through scanning were combined into a single image and then this reconstructed image was compared with images obtained by spectral imaging. The resulting SFLIM system is promising as an alternative method for the FLIM imaging of small animals, containing fluorophores exited by blue light, for LFOV applications such as whole animal imaging.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/76815,
title ="Preface on Making Oxygen",
author = "Eisenberg, Richard and Gray, Harry B.",
journal = "Inorganic Chemistry",
volume = "47",
number = "6",
pages = "1697-1699",
month = "March",
year = "2008",
doi = "10.1021/ic800155g",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170421-103318821",
note = "© 2008 American Chemical Society. \n\nReceived January 25, 2008. Publication Date (Web): March 10, 2008.",
revision_no = "9",
abstract = "Imagine a planet whose atmosphere is irreversibly changed\nby the dominant lifeform inhabiting it. The lifeform releases a gas--a waste gas--trillions and trillions of tons of it. The atmosphere becomes so altered that evolution on the planet is forever changed. Science fiction? Not at all! The planet is Earth, but the waste gas is not carbon dioxide and the time is not now. Instead, the unwanted gas is oxygen, the subject of this issue’s Forum, and the time is long, long ago. On primordial Earth, the atmosphere was reducing, most likely made up mainly of nitrogen, methane, ammonia, and water vapor. While oxygen is the most abundant element in the Earth’s crust, it did not exist in the atmosphere in primordial times to even a small fraction of the extent that it does today.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/79136,
title ="Probing Melittin Helix−Coil Equilibria in Solutions and Vesicles",
author = "Hartings, Matthew R. and Gray, Harry B.",
journal = "Journal of Physical Chemistry B",
volume = "112",
number = "10",
pages = "3202-3207",
month = "March",
year = "2008",
doi = "10.1021/jp709866g",
issn = "1520-6106",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170717-151917379",
note = "© 2008 American Chemical Society. \n\nReceived 9 October 2007. Published online 21 February 2008. Published in print 1 March 2008. \n\nThis work was supported by NIH (GM068461 to J.R.W., GM078792A to M.R.H.), Ellison Medical Foundation (Senior Scholar Award in Aging to H.B.G.), and the Arnold and Mabel Beckman Foundation.",
revision_no = "9",
abstract = "Melittin is a toxic, amphipathic peptide that rearranges from a random coil in solution to a helical structure upon binding to cell membranes or lipid vesicles. We have found that mutation of the valine at position five of the peptide to a phenylalanine or 3-nitrotyrosine induces aggregation and helix formation at low concentrations (20−80 μM). Donor−acceptor distances obtained from analyses of fluorescence energy transfer kinetics experiments with the 3-nitrotyrosine mutant indicate that both coil and helix structures are present in 2 and 20 μM aqueous solutions. The helical peptide population increases upon addition of phospholipid vesicles or in high ionic strength solutions.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/56973,
title ="Electron Tunneling through Pseudomonas aeruginosa Azurins on SAM Gold Electrodes",
author = "Yokoyama, Keiko and Leigh, Brian S.",
journal = "Inorganica Chimica Acta",
volume = "361",
number = "4",
pages = "1095-1099",
month = "March",
year = "2008",
doi = "10.1016/j.ica.2007.08.022",
issn = "0020-1693",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150424-150000195",
note = "© 2007 Elsevier. \n\nReceived 1 August 2007; accepted 18 August 2007; Available online 30 August 2007. \n\nDedicated to Edward Solomon in appreciation of his pioneering work on blue copper proteins. \n\nThis work was supported by NIH DK19038.",
revision_no = "13",
abstract = "Robust voltammetric responses were obtained for wild-type and Y72F/H83Q/Q107H/Y108F azurins adsorbed on CH_3(CH_2)_nSH:HO(CH_2)_mSH (n=m=4,6,8,11; n=13,15 m=11) self-assembled monolayer (SAM) gold electrodes in acidic solution (pH 4.6) at high ionic strengths. Electron-transfer (ET) rates do not vary substantially with ionic strength, suggesting that the SAM methyl headgroup binds to azurin by hydrophobic interactions. The voltammetric responses for both proteins at higher pH values (>4.6 to 11) also were strong. A binding model in which the SAM hydroxyl headgroup interacts with the Asn47 carboxamide accounts for the relatively strong coupling to the copper center that can be inferred from the ET rates. Of particular interest is the finding that rate constants for electron tunneling through n = 8, 13 SAMs are higher at pH 11 than those at pH 4.6, possibly owing to enhanced coupling of the SAM to Asn 47 caused by deprotonation of nearby surface residues.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/51753,
title ="Deeply Inverted Electron-Hole Recombination in a Luminescent Antibody-Stilbene Complex",
author = "Debler, Erik W. and Kaufmann, Gunnar F.",
journal = "Science",
volume = "319",
number = "5867",
pages = "1232-1235",
month = "February",
year = "2008",
doi = "10.1126/science.1153445",
issn = "0036-8075",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20141114-093033379",
note = "© 2008 American Association for the Advancement of Science.\n\nReceived 27 November 2007; accepted 18 January 2008.\n\nWe thank S. Ferguson for assistance in Fab preparation\nand the staff at Advanced Light Source beamline 5.0.1\nfor their support. We gratefully acknowledge A. Deniz for\nproviding access to his fluorimeter, and S. Mukhopadhyay\nfor assistance with anisotropy measurements as well as\nhelpful discussions. We thank J. Saltiel as well as the\nreviewers for critically reading the manuscript and\nproviding helpful comments. Coordinates and structure\nfactors for the EP2-25C10-1 complex have been\ndeposited at the Protein Data Bank (PDB) with accession\nnumber 2NZR. Supported by NIH grants GM38273\n(I.A.W.), GM56528 (P.G.S.), and DK19038 (H.B.G.) and a\nSkaggs predoctoral fellowship and Jairo H. Arévalo\nfellowship from The Scripps Research Institute graduate\nprogram (E.W.D.). This is publication 18959-MB from The\nScripps Research Institute.",
revision_no = "15",
abstract = "The blue-emissive antibody EP2-19G2 that has been elicited against trans-stilbene has unprecedented ability to produce bright luminescence and has been used as a biosensor in various applications. We show that the prolonged luminescence is not stilbene fluorescence. Instead, the emissive species is a charge-transfer excited complex of an anionic stilbene and a cationic, parallel π-stacked tryptophan. Upon charge recombination, this complex generates exceptionally bright blue light. Complex formation is enabled by a deeply penetrating ligand-binding pocket, which in turn results from a noncanonical interface between the two variable domains of the antibody.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/101256,
title ="Electronic structures of tetragonal nitrido and nitrosyl metal complexes",
author = "Hummel, Patrick and Winkler, Jay R.",
journal = "Theoretical Chemistry Accounts",
volume = "119",
number = "1-3",
pages = "35-38",
month = "January",
year = "2008",
doi = "10.1007/s00214-006-0236-8",
issn = "1432-881X",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20200212-153542105",
note = "© 2007 Springer-Verlag. \n\nReceived: 13 August 2006; Accepted: 8 November 2006; Published online: 12 January 2007. \n\nThis paper is dedicated to Philip Stephens in appreciation of his deep and lasting contributions to molecular spectroscopy. The work was supported by the National Science Foundation and the Arnold and Mabel Beckman Foundation.",
revision_no = "10",
abstract = "The standard oxidation states of central metal atoms in C_(4v) nitrido ([M(N)(L)₅]^z) complexes are four units higher than those in corresponding nitrosyls ([M(NO)(L)₅]^z) (L=CN: z = 3−, M = Mn, Tc, Re; z = 2−, M = Fe, Ru, Os; L = NH₃: z = 2+, M = Mn, Tc, Re; z = 3+, M = Fe, Ru, Os). Recent work has suggested that [Mn(NO)(CN)₅]³⁻ behaves electronically much closer to Mn(V)[b₂(xy)]², the ground state of [Mn(N)(CN)₅]³⁻, than to Mn(I)[b₂(xy)]²[e(xz,yz)]⁴. We have employed density functional theory and time-dependent density functional theory to calculate the properties of the ground states and lowest-lying excitations of [M(N)(L)₅]^z and [M(NO)(L)₅]^z . Our results show that [M(N)(L)₅]^z and [M(NO)(L)₅]^z complexes with the same z value have strikingly similar electronic structures.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/98107,
title ="Fred Basolo (1920–2007): Coordination chemist par excellence",
author = "Kauffman, G. B. and Kauffman, L. M.",
journal = "Russian Journal of Coordination Chemistry",
volume = "33",
number = "11",
pages = "865-866",
month = "November",
year = "2007",
doi = "10.1134/s1070328407110127",
issn = "1070-3284",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20190822-112507959",
note = "© 2007 Pleiades Publishing, Ltd. \n\nReceived: 05 May 2007.",
revision_no = "9",
abstract = "On February 27, 2007, Fred Basolo, Charles E. and Emma H. Morrison Professor of Chemistry Emeritus at Northwestern University, died of congestive heart failure at age 87 in Skokie, Illinois.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77845,
title ="Probing the cytochrome c′ folding landscape",
author = "Pletneva, Ekaterina V. and Zhao, Ziqing",
journal = "Journal of Inorganic Biochemistry",
volume = "101",
number = "11-12",
pages = "1768-1775",
month = "November",
year = "2007",
doi = "10.1016/j.jinorgbio.2007.06.019",
issn = "0162-0134",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170531-085209969",
note = "© 2007 Elsevier Inc. \n\nReceived 3 April 2007; received in revised form 31 May 2007; accepted 1 June 2007; Available online 21 June 2007. \n\nWe thank Professor Amy H. Andreotti for providing human cyclophilin plasmid and Binghai Ling for screening bacterial colonies for cyt c′ expression. Our work was supported by NIH (GM068461 to J.R.W.), the Ellison Medical Foundation (Senior Scholar Award in Aging to H.B.G.), the Caltech SURF program (Mr. and Mrs. Samuel Krown fellowship to Z.Z.), and the Japan Society for the Promotion of Science for Young Scientists (Research Fellowship to T.K.).",
revision_no = "12",
abstract = "The folding kinetics of R. palustris cytochrome c′ (cyt c′) have been monitored by heme absorption and native Trp72 fluorescence at pH 5. The Trp72 fluorescence burst signal suggests early compaction of the polypeptide ensemble. Analysis of heme transient absorption spectra reveals deviations from two-state behavior, including a prominent slow phase that is accelerated by the prolyl isomerase cyclophilin. A nonnative proline configuration (Pro21) likely interferes with the formation of the helical bundle surrounding the heme.",
}
@book_section {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/98343,
title ="Electron Tunneling Through Iron and Copper Proteins",
author = "Winkler, Jay R. and Dunn, Alexander R.",
pages = "1-23",
month = "October",
year = "2007",
doi = "10.1007/978-1-4020-6500-2_1",
isbn = "9781402064999",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20190829-131533188",
note = "© Springer 2008. \n\nOur research on electron tunneling through proteins is supported by the National Institutes of Health, the National Science Foundation, and the Arnold and Mabel Beckman Foundation.",
revision_no = "9",
abstract = "Iron and copper redox centers facilitate the transfer of electrons through proteins that are part of the respiratory and photosynthetic machinery of cells. Much work has been done with the goal of understanding the factors that control electron flow through these proteins. The results of many of the key experiments have been interpreted in terms of semiclassical theory.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77859,
title ="Probing Heme Coordination States of Inducible Nitric Oxide Synthase with a Re(I)(imidazole-alkyl-nitroarginine) Sensitizer-Wire",
author = "Nguyen, Yen Hoang Le and Winkler, Jay R.",
journal = "Journal of Physical Chemistry B",
volume = "111",
number = "24",
pages = "6628-6633",
month = "June",
year = "2007",
doi = "10.1021/jp071405+",
issn = "1520-6106",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170531-130123854",
note = "© 2007 American Chemical Society. \n\nReceived: February 19, 2007; In Final Form: April 4, 2007.\nPublication Date (Web): May 31, 2007. \n\nWe thank Professor Michael Marletta for materials and assistance in connection with the iNOSoxy preparation. Our work was supported by NIH and the Ellison Medical Foundation (Senior Scholar in Aging to H.B.G.).",
revision_no = "13",
abstract = "Mammalian inducible nitric oxide synthase (iNOS) catalyzes the production of L-citrulline and nitric oxide (NO) from L-arginine and O_2. The Soret peak in the spectrum of the iNOS heme domain (iNOS_(oxy)) shifts from 423 to 390 nm upon addition of a sensitizer-wire, [Re^I-imidazole-(CH_2)_8-nitroarginine]^+, or [ReC_8argNO_2]^+, owing to partial displacement of the water ligand in the active site. From analysis of competitive binding experiments with imidazole, the dissociation constant (K_d) for [ReC_8argNO_2]^+−iNOS_(oxy) was determined to be 3.0 ± 0.1 μM, confirming that the sensitizer-wire binds with higher affinity than both L-arginine (K_d = 22 ± 5 μM) and imidazole (K_d = 14 ± 3 μM). Laser excitation (355 nm) of [ReC_8argNO_2]^+−iNOS_(oxy) triggers electron transfer to the active site of the enzyme, producing a ferroheme in less than ∼1 μs.",
}
@book_section {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/85770,
title ="P450 Electron Transfer Reactions",
author = "Udit, Andrew K. and Contakes, Stephen M.",
pages = "157-185",
month = "March",
year = "2007",
doi = "10.1002/9780470028155.ch6",
isbn = "9780470016725",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180411-160923595",
note = "© 2007 John Wiley & Sons, Ltd. \n\nPublished Online: 11 May 2007; Published Print: 23 March 2007.",
revision_no = "8",
abstract = "[no abstract]",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77706,
title ="α-Synuclein Tertiary Contact Dynamics",
author = "Lee, Jennifer C. and Lai, Bert T.",
journal = "Journal of Physical Chemistry B",
volume = "111",
number = "8",
pages = "2107-2112",
month = "March",
year = "2007",
doi = "10.1021/jp068604y",
issn = "1520-6106",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170524-101700076",
note = "© 2007 American Chemical Society. \n\nReceived: December 14, 2006. Publication Date (Web): February 6, 2007. \n\nThis work was supported by the National Institutes of Health (GM068461 to J.R.W.; DK19038 to H.B.G.), the Arnold and Mabel Beckman Foundation (Beckman Senior Research Fellowship to J.C.L.), and the Ellison Medical Foundation (Senior Scholar Award in Aging to H.B.G.).",
revision_no = "17",
abstract = "Tertiary contact formation rates in α-synuclein, an intrinsically disordered polypeptide implicated in Parkinson's disease, have been determined from measurements of diffusion-limited electron-transfer kinetics between triplet-excited tryptophan:3-nitrotyrosine pairs separated by 10, 12, 55, and 90 residues. Calculations based on a Markovian lattice model developed to describe intrachain diffusion dynamics for a disordered polypeptide give contact quenching rates for various loop sizes ranging from 6 to 48 that are in reasonable agreement with experimentally determined values for small loops (10−20 residues). Contrary to expectations, measured contact rates in α-synuclein do not continue to decrease as the loop size increases (≥35 residues), and substantial deviations from calculated rates are found for the pairs W4−Y94, Y39−W94, and W4−Y136. The contact rates for these large loops indicate much shorter average donor−acceptor separations than expected for a random polymer.",
}
@conference_item {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/46142,
title ="Sensitizer-modified proteins for solar-driven water splitting",
author = "Gray, H. B. and Dempsey, J. L.",
pages = "PHYS-111",
month = "March",
year = "2007",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140609-091548403",
note = "© 2007 American Chemical Society.",
revision_no = "12",
abstract = "Aerobic respiration and photosynthesis work in concert: Dioxygen liberated by photosynthetic organisms sustains life in aerobic\nmicrobes and animals; and, in turn, the products of aerobic respiratory metab., carbon dioxide and water, nourish\nphotosynthetic organisms. Electron flow through proteins and protein assemblies in the photosynthetic and respiratory\nmachinery commonly occurs between metal centers or other redox cofactors that are sepd. by relatively large mol. distances,\noften in the 10 to 20 angstrom range. Both theorists and experimentalists have worked long and hard in attempts to understand\nthe underlying physics and chem. of these electron transport processes. Lessons learned about the control of electron tunneling\nand hopping through org. and biol. mols. are now being used to design sensitizer-modified protein machines incorporating\ncatalysts that can generate hydrogen fuel from sunlight and water.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/76759,
title ="Bacterial Spore Detection by [Tb^(3+)(macrocycle)(dipicolinate)] Luminescence",
author = "Cable, Morgan L. and Kirby, James P.",
journal = "Journal of the American Chemical Society",
volume = "129",
number = "6",
pages = "1474-1475",
month = "February",
year = "2007",
doi = "10.1021/ja061831t",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170420-103945719",
note = "© 2007 American Chemical Society. \n\nReceived March 27, 2006; Revised Manuscript Received December 5, 2006. Publication Date (Web): January 23, 2007. \n\nWe thank Mike Day, Larry Henling, and Hannah Shafaat for assistance. This work was supported by NSF Grant CHE-518164 and NASA Grant JPL-0098901.",
revision_no = "16",
abstract = "Dipicolinic acid (DPA) is a unique constituent of bacterial spores, a dormant form of Bacillus and Clostridium, which can be detected using DPA-triggered Tb^(3+) luminescence. [Tb(DO2A)]^+ improves the sensitivity of bacterial spore detection over Tb^(3+)(aq) owing to the exclusion of coordinated water molecules and represents the first step toward construction of a DPA receptor site with enhanced binding selectivity. The title ternary [Tb(DO2A)(DPA)]- complex was structurally characterized and features two DO2A-DPA interligand hydrogen interactions that stabilize the complex.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/8434,
title ="Site-specific collapse dynamics guide the formation of the cytochrome c' four-helix bundle",
author = "Kimura, Tetsunari and Lee, Jennifer C.",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "104",
number = "1",
pages = "117-122",
month = "January",
year = "2007",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:KIMpnas07",
note = "© 2006 The National Academy of Sciences of the USA. \n\nContributed by Harry B. Gray, October 24, 2006 (received for review October 12, 2006). Published online before print December 19, 2006, 10.1073/pnas.0609413103 \n\nWe thank Dr. Linda Thöny-Meyer (Eidgenössiche Technische Hochschule, Zürich, Switzerland) for the ccm plasmid pEC86 and Ekaterina V. Pletneva for numerous discussions. This work was supported by National Institutes of Health Grant GM068461 (to J.R.W.), the Arnold and Mabel Beckman Foundation (Beckman Senior Research Fellowship to J.C.L.), and the Ellison Medical Foundation (Senior Scholar Award in Aging to H.B.G.). T.K. was supported by a Research Fellowship of the Japan Society for the Promotion of Science for Young Scientists. \n\nAuthor contributions: T.K. and J.R.W. designed research; T.K. and J.C.L. performed research; T.K. and J.C.L. analyzed data; and T.K., J.C.L., H.B.G., and J.R.W. wrote the paper. \n\nThe authors declare no conflict of interest. \n\nThis article contains supporting information online at www.pnas.org/cgi/content/full/0609413103/DC1.",
revision_no = "8",
abstract = "The evolution of tryptophan-to-heme (W/heme) distance distributions extracted from analysis of fluorescence energy transfer kinetics during the refolding of Rhodopseudomonas palustris cytochrome c' reveals dramatic differences between two variants [W32 (Q1A/F32W/W72F) and W72 (Q1A)]. Both W32/heme and W72/heme distance distributions measured at the earliest time point attainable with a continuous-flow mixer (150 µs) confirm that the polypeptide ensemble is not uniformly collapsed and that native structure is not formed. Time-resolved fluorescence spectra indicate that W32 is sequestered from the aqueous solution during the first 700 µs of folding, whereas W72 remains exposed to solvent. The first moment of the W32/heme distance distribution evolves to its native value faster than that of W72, suggesting that the approach of W32 to the heme precedes that of W72.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/20420,
title ="Amphiphilic aluminium(III) and gallium(III) corroles",
author = "Sorasaenee, Karn and Taqavi, Pouyan",
journal = "Journal of Porphyrins and Phthalocyanines",
volume = "11",
number = "3-4",
pages = "189-197",
month = "January",
year = "2007",
issn = "1088-4246",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20101013-121343470",
note = "© 2007 Society of Porphyrins & Phthalocyanines. \n\nReceived 12 November 2006; Accepted 10 February 2007.\nPublished on web 03/29/2007.\n\nWe thank NSF, BP (MC2), the US-Israel Binational\nFoundation (BSF 2005127), and the Caltech SURF program (PT) for support.",
revision_no = "17",
abstract = "The preparation and spectroscopic properties of a series of metallocorroles with polar head groups CHO and CH=C(CN)(COOH) are reported, as well as the X-ray crystal structure of 5,10,15-tris(pentafluorophenyl)corrolatoaluminium(III)bispyridine (triclinic space group (P-1) with unit cell parameters: a = 9.426(1) Å; b = 13.202(1) Å; c = 19.936(1) Å; α = 74.19(1)°; β = 78.47(1)°; γ = 75.75(1)°; V = 2289.57(8) Å^3). Amphiphilic aluminium(III) and gallium(III) corroles exhibit electronic absorption (Soret peaks between 410 and 448 nm; Q-bands between 584 and 638 nm) and fluorescence (band maxima between 634 and 706 nm) at lower energies than their hydrophobic analogs.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77833,
title ="Electrochemistry of Cytochrome P450 BM3 in Sodium Dodecyl Sulfate Films",
author = "Udit, Andrew K. and Hill, Michael G.",
journal = "Langmuir",
volume = "22",
number = "25",
pages = "10854-10857",
month = "December",
year = "2006",
doi = "10.1021/la061162x",
issn = "0743-7463",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170530-133240937",
note = "© 2006 American Chemical Society. \n\nReceived April 28, 2006. In Final Form: July 25, 2006. Publication Date (Web): September 2, 2006. \n\nWe thank C. E. Immoos for helpful discussions and P. C. Cirino for providing BM3 mutant 5H6. We acknowledge support from NIH (H.B.G.), NSERC (A.K.U.), HHMI (A.K.U.), and the Ellison Medical Foundation (Senior Scholar Award in Aging to H.B.G.).",
revision_no = "13",
abstract = "Direct electrochemistry of the cytochrome P450 BM3 heme domain (BM3) was achieved by confining the protein within sodium dodecyl sulfate (SDS) films on the surface of basal-plane graphite (BPG) electrodes. Cyclic voltammetry revealed the heme Fe^(III/II) redox couple at −330 mV (vs Ag/AgCl, pH 7.4). Up to 10 V/s, the peak current was linear with the scan rate, allowing us to treat the system as surface-confined within this regime. The standard heterogeneous rate constant determined at 10 V/s was estimated to be 10 s^(-1). Voltammograms obtained for the BM3−SDS−BPG system in the presence of dioxygen exhibited catalytic waves at the onset of Fe^(III) reduction. The altered heme reduction potential of the BM3−SDS−graphite system indicates that SDS is likely bound in the enzyme active-site region. Compared to other P450-surfactant systems, we find redox potentials and electron-transfer rates that differ by ∼100 mV and >10-fold, respectively, indicating that the nature of the surfactant environment has a significant effect on the observed heme redox properties.",
}
@book_section {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/98304,
title ="Conjugates of Heme-Thiolate Enzymes with Photoactive Metal-Diimine Wires",
author = "Contakes, Stephen M. and Nguyen, Yen Hoang Le",
number = "123",
pages = "177-203",
month = "September",
year = "2006",
doi = "10.1007/430_2006_039",
issn = "0081-5993",
isbn = "9783540368090",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20190828-102318186",
note = "© Springer-Verlag Berlin Heidelberg 2006. \n\nFigure 11 was adopted from a version prepared by Alex Dunn. We thank him and others in the Caltech molecular wires group (Ivan Dmochowski, Jon Wilker, Corinna Hess, Wendy Belliston-Bittner, Nick Halpern-Manners) for contributions that are summarized in this chapter. Our work is supported by NIH, NSF, the Ellison Medical Foundation Senior Scholar Award in Aging (to HBG), and the Arnold and Mabel Beckman Foundation.",
revision_no = "10",
abstract = "Heme-thiolate enzymes, notably cytochromes P450 and nitric oxide synthases, use dioxygen to oxygenatesubstrates. Photoactive metal-diimine molecular wires that are capable of effecting rapid redox state changesat buried active sites have been developed to generate intermediates in the catalytic cycles of these enzymes.Wires that feature a photoactive head group tethered to an active-site ligand bind P450CAM and induciblenitric oxide synthase (iNOS) primarily by hydrophobic interactions. The wire-binding specificity of eachenzyme is critically dependent on the structural flexibility of the protein. P450CAM:wire conjugates canadopt open or partially open conformations, thereby accommodating a wide range of wires, whereas onlylong wires with smaller [Re(CO)_3(bpy)Im]^+ head groupsare able to bind tightly in the rigid active-site channel of iNOS. Dansyl-terminated molecular wires functionas highly sensitive and isoform specific fluorescent sensors for P450CAM.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/47581,
title ="Probing mechanisms of cobalt-catalyzed dihydrogen production from acidic solutions",
author = "Dempsey, Jillian L. and Peters, Jonas C.",
journal = "Abstracts of Papers of the American Chemical Society",
volume = "232",
pages = "INOR 252",
month = "September",
year = "2006",
issn = "0065-7727",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20140730-081255229",
note = "© 2006 American Chemical Society.",
revision_no = "13",
abstract = "Cobalt macrocycles capable of catalyzing the evolution of dihydrogen from acidic acetonitrile solns. are\nbeing investigated as part of a collaborative solar energy initiative. These metal complexes mediate\nelectrocatalytic dihydrogen prodn. at relatively pos. potentials (up to -0.26 V vs. SCE). The catalysis is\nactivated by the redn. of Co(II) species to a Co(I) intermediate, which likely adds a proton to give a Co(III)\nhydride that reacts further to produce dihydrogen. We are employing laser flash-quench methods coupled\nwith time-resolved spectroscopic monitoring to identify key intermediates in the reaction cycle that leads to\ndihydrogen prodn.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/56978,
title ="Probing folded and unfolded states of outer membrane protein a with steady-state and time-resolved tryptophan fluorescence",
author = "Kim, Judy E. and Arjara, Gitrada",
journal = "Journal of Physical Chemistry B",
volume = "110",
number = "35",
pages = "17656-62",
month = "September",
year = "2006",
doi = "10.1021/jp061991r",
issn = "1520-6106",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150424-152416156",
note = "© 2006 American Chemical Society. \n\nReceiVed: March 30, 2006; In Final Form: June 17, 2006. Publication Date (Web): August 16, 2006. \n\nWe thank Lukas K. Tamm at the University of Virginia for providing us with plasmids pET1102 and pET1103; Dennis Rinehart (University of Virginia), Thomas Surrey (EMBL Heidelberg), and William Ja for assistance with OmpA isolation and purification; and Jennifer C. Lee and Kate Pletneva for helpful discussions. This work was supported by NIH (NRSA postdoctoral fellowship to J.E.K.; NRSA training grant to G.A.; GM-068461 to J.R.W.), the Department of Energy (J.R.W., DE-FG02-02ER15359), the Ellison Medical Foundation (Senior Scholar in Aging to H.B.G.), and the Arnold and Mabel Beckman Foundation.",
revision_no = "13",
abstract = "Steady-state and time-resolved fluorescence measurements on each of five native tryptophan residues in full-length and truncated variants of E. coli outer-membrane protein A (OmpA) have been made in folded and denatured states. Tryptophan singlet excited-state lifetimes are multiexponential and vary among the residues. In addition, substantial increases in excited-state lifetimes accompany OmpA folding, with longer lifetimes in micelles than in phospholipid bilayers. This finding suggests that the Trp environments of OmpA folded in micelles and phospholipid bilayers are different. Measurements of Trp fluorescence decay kinetics with full-length OmpA folded in brominated lipid vesicles reveal that W102 is the most distant fluorophore from the hydrocarbon core, while W7 is the closest. Steady-state and time-resolved polarized fluorescence measurements indicate reduced Trp mobility when OmpA is folded in a micelle, and even lower mobility when the protein is folded in a bilayer. The fluorescence properties of truncated OmpA, in which the soluble periplasmic domain is removed, only modestly differ from those of the full-length form, suggesting similar folded structures for the two forms under these conditions.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/73871,
title ="Stability and Folding Kinetics of Structurally Characterized Cytochrome c-b_(562)",
author = "Faraone-Mennella, Jasmin and Tezcan, F. Akif",
journal = "Biochemistry",
volume = "45",
number = "35",
pages = "10504-10511",
month = "September",
year = "2006",
doi = "10.1021/bi060242x",
issn = "0006-2960",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170131-102250205",
note = "© 2006 American Chemical Society. \n\nReceived 5 February 2006. Published online 10 August 2006. \nPublished in print 1 September 2006. \n\nThis work was supported by National Institutes of Health Grant GM068461 (J.R.W.) and the Ellison Medical Foundation (Senior Scholar Award in Aging to H.B.G.).",
revision_no = "11",
abstract = "The four-helix-bundle protein fold can be constructed from a wide variety of primary amino acid sequences. Proteins with this structure are excellent candidates for investigations of the relationship between folding mechanism and topology. The folding of cytochrome b_(562), a four-helix-bundle heme protein, is hampered by heme dissociation. To overcome this complication, we have engineered a variant of cytochrome b_(562) (cyt c-b_(562)) featuring a c-type linkage between the heme and the polypeptide chain. The replacement of the native cyt b_(562) leader sequence in this protein with that of a c-type cytochrome (cyt c_(556)) led to high yields of fully matured and correctly folded cyt c-b_(562). We have determined the X-ray crystal structure of cyt c-b_(562) at 2.25 Å and characterized its physical, chemical, and folding properties. These measurements reveal that the c-type linkage does not perturb the protein fold or reduction potential of the heme group. The covalent attachment of the porphyrin to the polypeptide does, however, produce a substantial change in protein stability and folding kinetics.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/76899,
title ="Electronic Excited States of Tetracyanonickelate(II)",
author = "Hummel, Patrick and Halpern-Manners, Nicholas W.",
journal = "Inorganic Chemistry",
volume = "45",
number = "18",
pages = "7397-7400",
month = "September",
year = "2006",
doi = "10.1021/ic060584r",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170425-075608625",
note = "© 2006 American Chemical Society. \n\nReceived 6 April 2006. Published online 10 August 2006. Published in print 1 September 2006. \n\nThis work was supported by the NSF and the Arnold and Mabel Beckman Foundation.",
revision_no = "8",
abstract = "We revisit the assignment of the absorption spectrum of tetracyanonickelate(II) by calculating energies of excitations with time-dependent density functional theory. Our results give strong evidence that the original assignment of the spectrum is only partially correct. We thus propose an alternative assignment consistent with our theoretical calculations and all available experimental evidence. In particular, we reassign the bands at 22\u2009400 and 32\u2009300 cm-1 to the ^1A_(1g) → ^3A_(2g) (b_(2g) → b_(1g)) and ^1A_(1g) → ^1A_(2g) (b_(2g) → b_(1g)) excitations.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77431,
title ="Spectroscopy and Electrochemistry of Cytochrome P450 BM3-Surfactant Film Assemblies",
author = "Udit, Andrew K. and Hagen, Katharine D.",
journal = "Journal of the American Chemical Society",
volume = "128",
number = "31",
pages = "10320-10325",
month = "August",
year = "2006",
doi = "10.1021/ja061896w",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170512-144736551",
note = "© 2006 American Chemical Society. \n\nReceived 20 March 2006. Published online 18 July 2006. Published in print 1 August 2006. \n\nWe thank C. E. Immoos, P. J. Farmer, and L. A. Waskell for helpful discussions. Supported by HHMI (A.K.U.), the Camile and Henry Dreyfus Foundation (M.G.H.), NIH (DK19038 to H.B.G.), and the Ellison Medical Foundation (Senior Scholar Award in Aging to H.B.G.).",
revision_no = "12",
abstract = "We report analyses of electrochemical and spectroscopic measurements on cytochrome P450 BM3 (BM3) in didodecyldimethylammonium bromide (DDAB) surfactant films. Electronic absorption spectra of BM3−DDAB films on silica slides reveal the characteristic low-spin Fe^(III) heme absorption maximum at 418 nm. A prominent peak in the absorption spectrum of BM3 Fe^(II)−CO in a DDAB dispersion is at 448 nm; in spectra of aged samples, a shoulder at ∼420 nm is present. Infrared absorption spectra of the BM3 Fe^(II)−CO complex in DDAB dispersions feature a time-dependent shift of the carbonyl stretching frequency from 1950 to 2080 cm^(-1). Voltammetry of BM3-DDAB films on graphite electrodes gave the following results:\u2009Fe^(III/II) E_(1/2) at −260 mV (vs SCE), ∼300 mV positive of the value measured in solution; ΔS°_(rc), ΔS°, and ΔH° values for water-ligated BM3 in DDAB are −98 J mol^(-1) K^(-1), −163 J mol^(-1) K^(-1), and −47 kJ mol^(-1), respectively; values for the imidazole-ligated enzyme are −8 J mol^(-1) K^(-1), −73 J mol^(-1) K^(-1), and −21 kJ mol^(-1). Taken together, the data suggest that BM3 adopts a compact conformation within DDAB that in turn strengthens hydrogen bonding interactions with the heme axial cysteine, producing a P420-like species with decreased electron density around the metal center.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/78041,
title ="α-Synuclein Structures Probed by 5-Fluorotryptophan Fluorescence and ^(19)F NMR Spectroscopy",
author = "Winkler, Gates R. and Harkins, Seth B.",
journal = "Journal of Physical Chemistry B",
volume = "110",
number = "13",
pages = "7058-7061",
month = "April",
year = "2006",
doi = "10.1021/jp060043n",
issn = "1520-6106",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170609-072919854",
note = "© 2006 American Chemical Society. \n\nReceived 3 January 2006. Published online 16 March 2006. Published in print 1 April 2006. \n\nThis work was supported by the Arnold and Mabel Beckman Foundation (Beckman Senior Research Fellowship to J.C.L.) and the Ellison Medical Foundation (Senior Scholar Award in Aging to H.B.G.).",
revision_no = "10",
abstract = "α-Synuclein, the main protein component of fibrillar deposits found in Parkinson's disease, is intrinsically disordered in vitro. Site-specific information on the protein conformation has been obtained by biosynthetic incorporation of an unnatural amino acid, 5-fluorotryptophan (5FW), into the recombinant protein. Using fluorescence and ^(19)F NMR spectroscopy, we have characterized three proteins with 5FW at positions 4, 39, and 94. Steady-state emission spectra (maxima at 353 nm; quantum yields ≈ 0.2) indicate that all three indole side chains are exposed to the aqueous medium. Virtually identical single-exponential excited-state decays (τ ≈ 3.4 ns) were observed in all three cases. Single ^(19)F NMR resonances were measured for W4, W39, and W94 at −49.0 ± 0.1 ppm. Our analysis of the spectroscopic data suggests that the protein conformations are very similar in the regions near the three sites.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/56972,
title ="Excited-State Dynamics of Structurally Characterized [Re^I(CO)_3(phen)(HisX)]^+ (X = 83, 109) Pseudomonas aeruginosa Azurins in Aqueous Solution",
author = "Blanco-Rodríguez, Ana María and Busby, Michael",
journal = "Journal of the American Chemical Society",
volume = "128",
number = "13",
pages = "4365-4370",
month = "April",
year = "2006",
doi = "10.1021/ja057451+",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150424-145943126",
note = "© 2006 American Chemical Society. \n\nReceived November 1, 2005; Publication Date (Web): March 16, 2006. \n\nThis work was supported by the NIH (DK19038), NSF (MCB:\u2009 0133564), EPSRC, CCLRC, and QMUL.",
revision_no = "14",
abstract = "The triplet metal-to-ligand charge transfer (^3MLCT) dynamics of two structurally characterized Re^I(CO)_3(phen)(HisX)-modified (phen = 1,10-phenanthroline; X = 83, 109) Pseudomonas aeruginosa azurins have been investigated by picosecond time-resolved infrared (TRIR) spectroscopy in aqueous (D_2O) solution. The ^3MLCT relaxation dynamics exhibited by the two Re^I−azurins are very different from those of the sensitizer [Re^I(CO)_3(phen)(im)]+ (im = imidazole). Whereas the Re^I(CO)_3 intramolecular vibrational relaxation in Re^I(CO)_3(phen)(HisX)Az (4 ps) is similar to that of [ReI(CO)3(phen)(im)]+ (2 ps), the medium relaxation is much slower (∼250 vs 9.5 ps); the 250-ps relaxation is attributable to reorientation of D_2O molecules as well as structural reorganization of the rhenium chromophore and nearby polar amino acids in each of the modified proteins.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/75747,
title ="Excited-State Dynamics of Structurally Characterized [Re^I(CO)_3(phen)(HisX)]^+(X = 83, 109) Pseudomonas aeruginosa Azurins in Aqueous Solution",
author = "Blanco-Rodríguez, Ana María and Busby, Michael",
journal = "Journal of the American Chemical Society",
volume = "128",
number = "13",
pages = "4365-4370",
month = "April",
year = "2006",
doi = "10.1021/ja057451+",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170405-145213550",
note = "© 2006 American Chemical Society. \n\nReceived November 1, 2005; Publication Date (Web): March 16, 2006. \n\nThis work was supported by the NIH (DK19038), NSF (MCB:\u2009 0133564), EPSRC, CCLRC, and QMUL.",
revision_no = "11",
abstract = "The triplet metal-to-ligand charge transfer (^3MLCT) dynamics of two structurally characterized Re^I(CO)_3(phen)(HisX)-modified (phen = 1,10-phenanthroline; X = 83, 109) Pseudomonas aeruginosa azurins have been investigated by picosecond time-resolved infrared (TRIR) spectroscopy in aqueous (D_2O) solution. The ^3MLCT relaxation dynamics exhibited by the two ReI−azurins are very different from those of the sensitizer [Re^I(CO)_3(phen)(im)]^+ (im = imidazole). Whereas the Re^I(CO)_3 intramolecular vibrational relaxation in Re^I(CO)_3(phen)(HisX)Az (4 ps) is similar to that of [Re^I(CO)_3(phen)(im)]^+ (2 ps), the medium relaxation is much slower (∼250 vs 9.5 ps); the 250-ps relaxation is attributable to reorientation of D_2O molecules as well as structural reorganization of the rhenium chromophore and nearby polar amino acids in each of the modified proteins.",
}
@book_section {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/85819,
title ="Protein Folding, Misfolding, and Disease",
author = "Lee, Jennifer C. and Kim, Judy E.",
pages = "9-60",
month = "March",
year = "2006",
doi = "10.1002/0470028114.ch2",
isbn = "9780470014882",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180413-092655452",
note = "© 2006 John Wiley & Sons, Ltd. \n\nPublished Online: 27 July 2006; Published Print: 24 March 2006.",
revision_no = "7",
abstract = "[no abstract]",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/6910,
title ="Pyrene-Wired Heme Domain Cytochrome P450 BM3 Electrodes",
author = "Udit, Andrew K. and Hill, Michael G.",
journal = "ECS Meeting Abstracts",
volume = "501",
number = "1",
pages = "Abstract 9",
month = "February",
year = "2006",
issn = "1091-8213",
url = "https://resolver.caltech.edu/CaltechAUTHORS:UDIescm06",
note = "© 2006 The Electrochemical Society \n\n207th ECS Meeting, MA2005-01 May 15-May 20, 2005, Quebec City, Canada \n\nWe thank NSERC (Canada) (AKU), NSF (HBG), and David and Lucile Packard Foundation (MGH) for research support.\n",
revision_no = "6",
abstract = "Cytochromes P450 (P450s) catalyze oxygenations of inert substrates under physiological conditions. Exploiting this activity in vitro would be greatly facilitated if reductants other than NADPH could be found. We are working on electrochemical methods for reduction of P450 from Bacillus megaterium (BM3), an attractive target for in vitro applications given its high turnover rates and broad substrate specificity [1].",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/5517,
title ="Cyclometalated iridium(III)-sensitized titanium dioxide solar cells",
author = "Mayo, Elizabeth I. and Kilså, Kristine",
journal = "Photochemical and Photobiological Sciences",
volume = "5",
number = "10",
pages = "871-873",
month = "January",
year = "2006",
issn = "1474-905X",
url = "https://resolver.caltech.edu/CaltechAUTHORS:MAYpps06",
note = "© The Royal Society of Chemistry and Owner Societies 2006 \n\nReceived 14th June 2006, Accepted 6th September 2006. First published on the web 20th September 2006 \n\nThis work was supported by the DOE, NREL, Global Photonic Energy Corp., the NSF, BP, the Carlsberg Foundation, and the Caltech Summer Undergraduate Research Program. \n\nThis paper was published as part of the special issue in honour of the late Professor George S. Hammond. Photochemical & Photobiological Sciences, volume 5, issue 10, 2006.",
revision_no = "12",
abstract = "Ir(III) dyes used as sensitizers in dye-sensitized solar cells produced quantum yields approaching unity for conversion of absorbed photons to current under simulated air mass 1.0 sunlight, with current production resulting from ligand-to-ligand charge-transfer states, rather than the typical metal-to-ligand charge-transfer states in ruthenium-based cells.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/6899,
title ="Electronic structures of trans-dioxometal complexes",
author = "Hummel, Patrick and Winkler, Jay R.",
journal = "Dalton Transactions",
volume = "2006",
number = "1",
pages = "168-171",
month = "January",
year = "2006",
issn = "1477-9226",
url = "https://resolver.caltech.edu/CaltechAUTHORS:HUMdt06",
note = "© The Royal Society of Chemistry 2005 \n\nReceived 30th August 2005, Accepted 10th October 2005. First published on the web 4th November 2005",
revision_no = "35",
abstract = "We have employed computational methods based on density functional theory to elucidate the effects of equatorial ligands on the electronic structures of trans-dioxometal complexes. In complexes with ammine (σ-only) equatorial donors, the 1A1 g(b2 g)^2 → Eg(b2 g)^1(eg)^1 excitation energy increases with metal oxidation state: Mo(IV) < Tc(V) < Ru(VI) and W(IV) < Re(V) < Os(VI). Increasing transition energies are attributed to enhanced oxometal π-donor interactions in the higher valent central metals. But in complexes with cyanide equatorial donors, the 1A1 g(b2 g)^2 →Eg(b2 g)^1(eg)^1 energy remains roughly independent of metal oxidation state, likely owing to the compensating increased π-donation from the π(CN) orbitals to the metal dxy orbitals as the oxidation state of the metal increases.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/4295,
title ="Snapshots of cytochrome c folding",
author = "Pletneva, Ekaterina V. and Gray, Harry B.",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "102",
number = "51",
pages = "18397-18402",
month = "December",
year = "2005",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:PLEpnas05",
note = "© 2005 by the National Academy of Sciences \n\nContributed by Harry B. Gray, October 17, 2005 \n\nWe acknowledge Yuling Sheng for her help with protein expression and purification during the final stages of this work. We also thank Jennifer C. Lee and Judy E. Kim for help with FET kinetics measurements and numerous discussions. This work was supported by National Institutes of Health Grant GM068461 (to J.R.W.) and an Ellison Medical Foundation Senior Scholar Award in Aging (to H.B.G.). \n\nAuthor contributions: E.V.P., H.B.G., and J.R.W. designed research; E.V.P. performed research; E.V.P. and J.R.W. analyzed data; and E.V.P., H.B.G., and J.R.W. wrote the paper. \n\nConflict of interest statement: No conflicts declared.",
revision_no = "8",
abstract = "Dansyl-to-heme distance distributions [P(r)] during folding have been determined in five variants of Saccharomyces cerevisiae iso-1 ferricytochrome c (labeled at mutant Cys residues 4, 39, 50, 66, and 99) by analysis of fluorescence energy-transfer kinetics. Moment analysis of the P(r) distributions clearly indicates that cytochrome c refolding is not a simple two-state process. After 1 ms of folding, the polypeptide ensemble is not uniformly collapsed and there are site variations in the relative populations of collapsed structures. P(r) distributions reveal structural features of the multiple intermediate species and evolution of the polypeptide ensemble.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77415,
title ="Tertiary Contact Formation in α-Synuclein Probed by Electron Transfer",
author = "Lee, Jennifer C. and Gray, Harry B.",
journal = "Journal of the American Chemical Society",
volume = "127",
number = "47",
pages = "16388-16389",
month = "November",
year = "2005",
doi = "10.1021/ja0561901",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170512-124549828",
note = "© 2005 American Chemical Society. \n\nReceived September 8, 2005. Publication Date (Web): November 3, 2005. \n\nSupported by the Parkinson's Disease Foundation (J.R.W.), the National Parkinson Foundation (J.R.W.), NIH (GM068461 to J.R.W.), DOE (DE-FG02-02ER15359 to J.R.W.), the Arnold and Mabel Beckman Foundation (Beckman Senior Research Fellowship to J.C.L.), the Beckman Macular Research Center (H.B.G.), and the Ellison Medical Foundation (Senior Scholar Award in Aging to H.B.G.). ",
revision_no = "15",
abstract = "To explore tertiary contact formation in α-synuclein, a natively unfolded protein implicated in Parkinson's disease, we have measured the rates of reaction between a powerful electron donor, the tryptophan (W) triplet excited state, and an acceptor, 3-nitro-tyrosine (Y(NO_2)) in six different variants, probing loop sizes between 15 and 132 residues. Electron transfer rates decrease with loop size with the fastest contact time of 140 ns for the N-terminal pair and the slowest of 1.2 μs for the N- to C-terminal pair. Diffusion coefficients ranging from ∼2 × 10^(-6) to ∼10^(-5) cm^2 s^(-1) were extracted from simultaneous fits of the W to Y(NO_2) electron (triplet excited state) and energy transfer (singlet excited state) kinetics.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77495,
title ="Picosecond Photoreduction of Inducible Nitric Oxide Synthase by Rhenium(I)−Diimine Wires",
author = "Belliston-Bittner, Wendy and Dunn, Alexander R.",
journal = "Journal of the American Chemical Society",
volume = "127",
number = "45",
pages = "15907-15915",
month = "November",
year = "2005",
doi = "10.1021/ja0543088",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170516-102144501",
note = "© 2005 American Chemical Society. \n\nReceived 29 June 2005. Published online 19 October 2005. Published in print 1 November 2005. \n\nThis research was supported by NIH (DK19038; GM070868), the Parsons Foundation (W.B.-B.), the Fannie and John Hertz Foundation (A.R.D.), the Ellison Medical Foundation (Senior Scholar Award in Aging to H.B.G.), and the Arnold and Mabel Beckman Foundation.",
revision_no = "15",
abstract = "In a continuing effort to unravel mechanistic questions associated with metalloenzymes, we are developing methods for rapid delivery of electrons to deeply buried active sites. Herein, we report picosecond reduction of the heme active site of inducible nitric oxide synthase bound to a series of rhenium−diimine electron-tunneling wires, [Re(CO)_3LL‘]^+, where L is 4,7-dimethylphenanthroline and L‘ is a perfluorinated biphenyl bridge connecting a rhenium-ligated imidazole or aminopropylimidazole to a distal imidazole (F_8bp-im (1) and C_3-F_8bp-im (2)) or F (F_9bp (3) and C_3-F_9bp (4)). All four wires bind tightly (K_d in the micromolar to nanomolar range) to the tetrahydrobiopterin-free oxidase domain of inducible nitric oxide synthase (iNOSoxy). The two fluorine-terminated wires displace water from the active site, and the two imidazole-terminated wires ligate the heme iron. Upon 355-nm excitation of iNOSoxy conjugates with 1 and 2, the active site Fe(III) is reduced to Fe(II) within 300 ps, almost 10 orders of magnitude faster than the naturally occurring reduction.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77492,
title ="Nature of the Cytochrome c Molten Globule",
author = "Pletneva, Ekaterina V. and Gray, Harry B.",
journal = "Journal of the American Chemical Society",
volume = "127",
number = "44",
pages = "15370-15371",
month = "November",
year = "2005",
doi = "10.1021/ja0555318",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170516-102143640",
note = "© 2005 American Chemical Society. \n\nReceived 12 August 2005. Published online 13 October 2005. Published in print 1 November 2005. \n\nThis work was supported by NIH GM068461 (J.R.W.) and the Ellison Medical Foundation (Senior Scholar Award in Aging to H.B.G.).",
revision_no = "14",
abstract = "We have employed fluorescence energy transfer (FET) kinetics to probe unfolded and molten globule states of five dansyl (Dns) variants of Saccharomyces cerevisiae iso-1 cytochrome c. The covalently bound Fe(III) heme group quenches Dns fluorescence by energy transfer; measurements of FET kinetics yielded distributions of D−A distances (P(r)) for these states. The P(r) distributions and corresponding mean force potentials (U(r)) show that the cytochrome c molten globule is a highly structured state with a substantial number of native interactions. Wide P(r) distributions directly reflect the dynamic nature and conformational diversity of this molten globule. P(r) distributions for the “burst-phase” refolding intermediate suggest that the equilibrium cytochrome c molten globule is not a suitable model for early intermediates formed during protein refolding.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/2132,
title ="Reversible inhibition of copper amine oxidase activity by channel-blocking ruthenium(II) and rhenium(I) molecular wires",
author = "Contakes, Stephen M. and Juda, Gregory A.",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "102",
number = "38",
pages = "13451-13456",
month = "September",
year = "2005",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:CONpnas05",
note = "© 2005 by the National Academy of Sciences. \n\nContributed by Harry B. Gray, July 27, 2005. Published online before print September 12, 2005, 10.1073/pnas.0506336102. \n\nThis work was supported by National Institutes of Health Grants GM65011 (to S.M.C.), DK19038 and GM070868 (both to H.B.G.), and GM27659 (to D.M.D.) and Australian Research Council Grant DP0208320 (to H.C.F. and J.M.G.). \n\nData deposition: The coordinates and structure factors of the complex have been deposited in the Protein Data Bank, www.pdb.org (PDB ID code 2BT3 [PDB]).",
revision_no = "8",
abstract = "Molecular wires comprising a Ru(II)- or Re(I)-complex head group, an aromatic tail group, and an alkane linker reversibly inhibit the activity of the copper amine oxidase from Arthrobacter globiformis (AGAO), with K-i values between 6 mu M and 37 nM. In the crystal structure of a Ru(II)-wire:AGAO conjugate, the wire occupies the AGAO active-site substrate access channel, the trihydroxyphenylalanine quinone cofactor is ordered in the \"off-Cu\" position with its reactive carbonyl oriented toward the inhibitor, and the \"gate\" residue, Tyr-296, is in the \"open\" position. Head groups, tail-group substituents, and linker lengths all influence wire-binding interactions with the enzyme.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/76830,
title ="Redox Couples of Inducible Nitric Oxide Synthase",
author = "Udit, Andrew K. and Belliston-Bittner, Wendy",
journal = "Journal of the American Chemical Society",
volume = "127",
number = "32",
pages = "11212-11213",
month = "August",
year = "2005",
doi = "10.1021/ja0520114",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170421-153121728",
note = "© 2005 American Chemical Society. \n\nReceived March 29, 2005. Publication Date (Web): July 20, 2005. \n\nSupported by NSERC (Canada) (A.K.U.), HHMI (A.K.U.), NIH (DK19038; GM070868), the Packard Foundation (M.G.H.), the Ellison Medical Foundation (Senior Scholar Award in Aging to H.B.G.), and the Parsons Foundation (W.B.B.); S. Luzzi (Berkeley) assisted with protein expression and purification.",
revision_no = "17",
abstract = "We report direct electrochemistry of the iNOS heme domain in a DDAB film on the surface of a basal plane graphite electrode. Cyclic voltammetry reveals Fe^(III/II) and Fe^(II/I) couples at −191 and −1049 mV (vs Ag/AgCl). Imidazole and carbon monoxide in solution shift the Fe^(III/II) potential by +20 and +62 mV, while the addition of dioxygen results in large catalytic waves at the onset of Fe^(III) reduction. Voltammetry at higher scan rates (with pH variations) reveals that the Fe^(III/II) cathodic peak can be resolved into two components, which are attributable to Fe^(III/II) couples of five- and six-coordinate hemes. Digital simulation of our experimental data implicates water dissociation from the heme as a gating mechanism for ET in iNOS.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/76933,
title ="Protein−Surfactant Film Voltammetry of Wild-Type and Mutant Cytochrome P450 BM3",
author = "Udit, Andrew K. and Hindoyan, Nareen",
journal = "Inorganic Chemistry",
volume = "44",
number = "12",
pages = "4109-4111",
month = "June",
year = "2005",
doi = "10.1021/ic0483747",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170426-070838205",
note = "© 2005 American Chemical Society. \n\nReceived 17 November 2004. Published online 11 May 2005. Published in print 1 June 2005. \n\nE. Blair and P. J. Farmer (UC Irvine) for assistance with film preparation; M. W. Peters and P. Meinhold (Caltech) for helpful discussions; and NSERC (Canada) (A.K.U.), NIH (H.B.G.), and the David and Lucille Packard Foundation (M.G.H.) for research support.",
revision_no = "12",
abstract = "We are investigating the redox chemistry of wild-type (WT) and mutant (1-12G) cytochrome P450 BM3. Absorption spectra in solution feature the FeIII Soret at 418 nm for WT and a split Soret for 1-12G at 390 and 418 nm. Voltammetry of the proteins within DDAPSS films on the surface of carbon electrodes reveal nearly identical Fe^(III/II) potentials (approximately −200 mV vs Ag/AgCl), but significant differences in k°, 250 vs 30 s^(-1), and Fe^(III/II)−CO potentials, −140 vs −115 mV, for WT vs 1-12G. Catalytic reduction of dioxygen by the proteins on rotating-disk electrodes was analyzed using Levich and Koutecky−Levich treatments. The data reveal 1-12G n and k_(obs) values that are, respectively, 1.7 and 0.07 times those of WT, suggesting that the two proteins differ strikingly in their reactions with dioxygen.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/990,
title ="Early events in the folding of four-helix-bundle heme proteins",
author = "Faraone-Mennella, Jasmin and Gray, Harry B.",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "102",
number = "18",
pages = "6315-6319",
month = "May",
year = "2005",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:FARpnas05",
note = "© 2005 by the National Academy of Sciences. \n\nContributed by Harry B. Gray, March 21, 2005. \n\nThis research was supported by National Institutes of Health Grant GM068461, Department of Energy Grant DE-FG02-02ER15359, and the Arnold and Mabel Beckman Foundation.",
revision_no = "8",
abstract = "Topologically homologous four-helix-bundle heme proteins exhibit striking diversity in their refolding kinetics. Cytochrome b(562) has been reported to fold on a submillisecond time scale, whereas cytochrome c' refolding requires 10 s or more to complete. Heme dissociation in cytochrome b(562) interferes with studies of folding kinetics, so a variant of cytochrome b(562) (cytochrome c-b(562)) with a covalent c-type linkage to the heme has been expressed in Escherichia coli. Early events in the electron transfer-triggered folding of Fe-II-cytochrome c-b(562), along with those of Fe-II-cytochrome c(556), have been examined by using time-resolved absorption spectroscopy. Coordination of S(Met) to Fe-II occurs within 10 mu(s) after reduction of the denatured Fe-III-cytochromes, and shortly thereafter (100 mu(s)) the heme spectra are indistinguishable from those of the folded proteins. Under denaturing conditions, carbon monoxide binds to the Fe-II-hemes in approximate to 15 ms. By contrast, CO binding cannot compete with refolding in the Fe-II-cytochromes, thereby confirming that the polypeptide encapsulates the heme in <10 ms. We suggest that Fe-S(Met) ligation facilitates refolding in these four-helix-bundle heme proteins by reducing the conformational freedom of the polypeptide chain.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/76768,
title ="Luminescent Ruthenium(II)− and Rhenium(I)−Diimine Wires Bind Nitric Oxide Synthase",
author = "Dunn, Alexander R. and Belliston-Bittner, Wendy",
journal = "Journal of the American Chemical Society",
volume = "127",
number = "14",
pages = "5169-5173",
month = "April",
year = "2005",
doi = "10.1021/ja046971m",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170420-115315543",
note = "© 2005 American Chemical Society. \n\nReceived 22 May 2004. Published online 17 March 2005. Published in print 1 April 2005. \n\nWe thank John Magyar for helpful discussions. This work was supported by the Fannie and John Hertz Foundation (A.R.D.), the National Institutes of Health (W.B., E.D.G.), and the National Science Foundation (H.B.G., J.R.W.).",
revision_no = "13",
abstract = "Ru(II)− and Re(I)−diimine wires bind to the oxygenase domain of inducible nitric oxide synthase (iNOSoxy). In the ruthenium wires, [Ru(L)_2L‘]^(2+), L‘ is a perfluorinated biphenyl bridge connecting 4,4‘-dimethylbipyridine to a bulky hydrophobic group (adamantane, 1), a heme ligand (imidazole, 2), or F (3). 2 binds in the active site of the murine iNOSoxy truncation mutants Δ65 and Δ114, as demonstrated by a shift in the heme Soret from 422 to 426 nm. 1 and 3 also bind Δ65 and Δ114, as evidenced by biphasic luminescence decay kinetics. However, the heme absorption spectrum is not altered in the presence of 1 or 3, and Ru−wire binding is not affected by the presence of tetrahydrobiopterin or arginine. These data suggest that 1 and 3 may instead bind to the distal side of the enzyme at the hydrophobic surface patch thought to interact with the NOS reductase module. Complexes with properties similar to those of the Ru−diimine wires may provide an effective means of NOS inhibition by preventing electron transfer from the reductase module to the oxygenase domain. Rhenium−diimine wires, [Re(CO)_3L_1L_1‘]+, where L_1 is 4,7-dimethylphenanthroline and L_1‘ is a perfluorinated biphenyl bridge connecting a rhenium-ligated imidazole to a distal imidazole (F_8bp-im) (4) or F (F_9bp) (5), also form complexes with Δ114. Binding of 4 shifts the Δ114 heme Soret to 426 nm, demonstrating that the terminal imidazole ligates the heme iron. Steady-state luminescence measurements establish that the 4:Δ114 dissociation constant is 100 ± 80 nM. Re−wire 5 binds Δ114 with a K_d of 5 ± 2 μM, causing partial displacement of water from the heme iron. Our finding that both 4 and 5 bind in the NOS active site suggests novel designs for NOS inhibitors. Importantly, we have demonstrated the power of time-resolved FET measurements in the characterization of small molecule:protein interactions that otherwise would be difficult to observe.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/75142,
title ="Ligand-Field Excited States of Metal Hexacarbonyls",
author = "Hummel, Patrick and Oxgaard, Jonas",
journal = "Inorganic Chemistry",
volume = "44",
number = "7",
pages = "2454-2458",
month = "April",
year = "2005",
doi = "10.1021/ic048215n",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170315-102857802",
note = "© 2005 American Chemical Society. \n\nReceived December 17, 2004. Publication Date (Web): March 3, 2005. \n\nWe thank the Caltech Summer Undergraduate Research Fellowship program as well as DARPA-PROM, ONR-DURIP, ARO-DURIP, Beckman Institute, and NSF-MRI for support.",
revision_no = "10",
abstract = "Over 35 years ago, the low-lying bands in the absorption spectra of metal hexacarbonyls were assigned to ligand-field (LF) excitations. Recent time-dependent density functional theory (TDDFT) calculations on M(CO)_6 (M = Cr, Mo, W) are not in accord with this interpretation. Here we extend TDDFT calculations to the isoelectronic series V(CO)_6^-, Cr(CO)_6, and Mn(CO)_6^+. By analyzing the trends in the energies of the various electronic excitations, we are able to fully assign the spectra of the complexes. In particular, we demonstrate that the LF excitation ^1A_(1g) → ^1T_(1g) is observed at 4.12 eV in the Mn(CO)_6^+ spectrum, but all LF features in the spectra of V(CO)_6^- and Cr(CO)_6 are obscured by intense metal-to-ligand charge-transfer absorptions. Our results suggest that use of B3LYP as the exchange-correlation functional and inclusion of solvation effects through a continuum solvation model lead to the most accurate calculated transition energies.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/998,
title ="Distant charge transport",
author = "Gray, Harry B. and Halpern, Jack",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "102",
number = "10",
pages = "3533-3533",
month = "March",
year = "2005",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:GRApnas05a",
note = "© 2005 by the National Academy of Sciences.",
revision_no = "7",
abstract = "Highlighting this issue of PNAS is a special feature comprising a Perspective and five research articles on the theme of long-range electron transfer. Distant electron transfers play key roles in aerobic respiration and photosynthesis, which work in concert: The oxygen that is evolved by photosynthetic organisms is the oxidant that sustains life in aerobic microbes and animals; and, in turn, the end products of aerobic respiratory metabolism, carbon dioxide and water, nourish photosynthetic organisms. Electron flow through proteins and protein assemblies in the respiratory and photosynthetic machinery commonly occurs between redox active cofactors that are separated by large molecular distances, often on the order of 10–25 Å. Although these cofactors are weakly coupled electronically, the reactions are remarkably rapid and specific. Understanding the underlying physics and chemistry of these distant electron transfer processes has been an overarching goal of theorists and experimentalists for many years.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/952,
title ="Long-range electron transfer",
author = "Gray, Harry B. and Winkler, Jay R.",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "102",
number = "10",
pages = "3534-3539",
month = "March",
year = "2005",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:GRApnas05b",
note = "© 2005 by the National Academy of Sciences. \n\nEdited by Jack Halpern, University of Chicago, Chicago, IL and accepted January 28, 2005 (received for review January 5, 2005). \n\nOur work is supported by the National Institutes of Health, the National Science Foundation, BP, and the Arnold and Mabel Beckman Foundation. \n\nThis paper was submitted directly (Track II) to the PNAS office.",
revision_no = "8",
abstract = "Recent investigations have shed much light on the nuclear and electronic factors that control the rates of long-range electron tunneling through molecules in aqueous and organic glasses as well as through bonds in donor-bridge-acceptor complexes. Couplings through covalent and hydrogen bonds are much stronger than those across van der Waals gaps, and these differences in coupling between bonded and nonbonded atoms account for the dependence of tunneling rates on the structure of the media between redox sites in Ru-modified proteins and protein-protein complexes.",
}
@book_section {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/85815,
title ="Electron Transfer through Proteins",
author = "Winkler, Jay R. and Gray, Harry B.",
pages = "15-33",
month = "January",
year = "2005",
doi = "10.1002/352760376X.ch2",
isbn = "9783527306909",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180413-090316338",
note = "© 2005 Wiley‐VCH Verlag GmbH & Co. KGaA. \n\nPublished Online: 23 May 2005; Published Print: 26 January 2005.",
revision_no = "9",
abstract = "[no abstract]",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/52054,
title ="Electron Tunneling Through Organic Molecules in Frozen Glasses",
author = "Wenger, Oliver S. and Leigh, Brian S.",
journal = "Science",
volume = "307",
number = "5706",
pages = "99-102",
month = "January",
year = "2005",
doi = "10.1126/science.1103818",
issn = "0036-8075",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20141121-140952473",
note = "© 2005 American Association for the Advancement of Science.\n\n9 August 2004; Accepted 23 November 2004.\n\nWe thank J. Kim, J. Lee, and J. Magyar for several helpful discussions. Supported by BP, the NSF (grant no. CHE-0078809), and the Arnold and Mabel Beckman Foundation. O.S.W. acknowledges a postdoctoral fellowship from the Swiss National Science Foundation and B.S.L., a graduate fellowship from the Parsons Foundation.",
revision_no = "11",
abstract = "Reaction rates extracted from measurements of donor luminescence quenching by randomly dispersed electron acceptors reveal an exponential decay constant of 1.23 per angstrom for electron tunneling through a frozen toluene glass (with a barrier to tunneling of 1.4 electron volts). The decay constant is 1.62 per angstrom (the barrier, 2.6 electron volts) in a frozen 2-methyl-tetrahydrofuran glass. Comparison to decay constants for tunneling across covalently linked xylyl (0.76 per angstrom) and alkyl (1.0 per angstrom) bridges leads to the conclusion that tunneling between solvent molecules separated by ∼2 angstroms (van der Waals contact) is 20 to 50 times slower than tunneling through a comparable length of a covalently bonded bridge. Our results provide experimental confirmation that covalently bonded pathways can facilitate electron flow through folded polypeptide structures.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/76721,
title ="Metalloprotein Folding",
author = "Bren, Kara L. and Pecoraro, Vincent L.",
journal = "Inorganic Chemistry",
volume = "43",
number = "25",
pages = "7894-7896",
month = "December",
year = "2004",
doi = "10.1021/ic040121q",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170419-154018328",
note = "© 2004 American Chemical Society. \n\nReceived November 3, 2004. Publication Date (Web): December 6, 2004.",
revision_no = "9",
abstract = "One of the most intriguing problems in the biological\nsciences is the question of how to predict protein structure\nand function based on knowledge of a gene sequence. While\nsignificant progress has been made toward this goal during\nthe past decade, fundamental challenges remain, such as\nunderstanding important post-translational modifications. One of the most critical post-translational modifications is the incorporation of a metal or metal cofactor into a catalytic or structural site in order to gain proper function. At the same time, some proteins function solely to recognize, transport, or sequester metals. When we consider how metals affect protein structure and function, we should not neglect their role in protein folding and stability as well as their participation in protein dynamics, as all are essential for optimal activity. Thus, workers in bioinorganic chemistry have an opportunity to be major contributors to the fields of protein folding and structure prediction.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/76896,
title ="Zinc-porphyrin Solvation in Folded and Unfolded States of Zn-cytochrome c",
author = "Kim, Judy E. and Pribisko, Melanie A.",
journal = "Inorganic Chemistry",
volume = "43",
number = "25",
pages = "7953-7960",
month = "December",
year = "2004",
doi = "10.1021/ic048972l",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170425-074119551",
note = "© 2004 American Chemical Society. \n\nReceived 29 July 2004. Published online 5 November 2004. Published in print 1 December 2004. \n\nWe thank Kate Pletneva for assistance with zinc incorporation into cytochrome c, and Jennifer Lee and John Magyar for helpful discussions. J.E.K. is supported by a Ruth L. Kirschstein National Research Service Award from the National Institutes of Health. This research was supported by the National Institutes of Health (GM068461) and the Arnold and Mabel Beckman Foundation.",
revision_no = "10",
abstract = "After a brief review of the use of photochemical triggers and heme metal substitution to probe the folding dynamics of cytochrome c, we present new results on the photophysics and photochemistry of folded and unfolded states of the zinc-substituted protein (Zn-cyt c). Our measurements of Zn-cyt c triplet state decay kinetics reveal a systematic isotope effect on lifetimes:\u2009 the decay in the folded protein (τ_H_2_O ∼ 10 ms) is only modestly affected by isotopically substituted buffers (k_H_2_O/k_D_2_O = 1.2), whereas a reduced triplet lifetime (∼1.3 ms) and greater isotope effect (1.4) were found for the chemically denatured, fully unfolded protein. The shortest lifetime (0.1−0.4 ms) and greatest isotope effect (1.5) were found for a fully exposed model compound, zinc-substituted N-acetyl-microperoxidase-8 (ZnAcMP8), implying that the unfolded protein provides some protection to the Zn-porphyrin group even under fully denaturing conditions. Further evidence for partial structure in unfolded Zn-cyt c comes from bimolecular quenching experiments using Ru(NH_3)_6^(3+) as an external Zn-porphyrin triplet state quencher. In the presence of quencher, partially unfolded protein at midpoint guanidinium chloride (GdmCl) and urea concentrations exhibits biphasic triplet decay kinetics, a fast component corresponding to an extended, solvent-exposed state (6.6 × 10^8 M^(-1) s^(-1) in GdmCl, 6.3 × 10^8 M^(-1) s^(-1) in urea) and a slow component attributable to a compact, relatively solvent-inaccessible, state (5.9 × 10^7 M^(-1) s^(-1) in GdmCl, 8.6 × 10^6 M^(-1) s^(-1) in urea). The variation in Zn-porphyrin solvation for the compact states in the two denaturants reveals that the cofactor in the partially unfolded protein is better protected in urea solutions.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/76895,
title ="Inner-Sphere Electron-Transfer Reorganization Energies of Zinc Porphyrins",
author = "Amashukeli, Xenia and Gruhn, Nadine E.",
journal = "Journal of the American Chemical Society",
volume = "126",
number = "47",
pages = "15566-15571",
month = "December",
year = "2004",
doi = "10.1021/ja0351037",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170425-073409553",
note = "© 2004 American Chemical Society. \n\nReceived March 11, 2003. Publication Date (Web): November 5, 2004. \n\nWe thank F. Ann Walker for providing the sample of Zn(oep). This work was supported by the NSF (CHE-0078809, H.B.G., J.R.W.; CHE-0078457, D.L.L.) and the DOE (DE-FG03-95ER14574, D.L.L.).",
revision_no = "11",
abstract = "Inner-sphere electron-transfer reorganization energies of Zn(protoporphyrin IX) and Zn(octaethylporphyrin) are determined from band-shape analyses of the first ionization obtained by gas-phase valence photoelectron spectroscopy. The experimentally determined total inner-sphere reorganization energies for self-exchange (120−140 meV) indicate that structural changes upon oxidation are largely confined to the porphyrin ring, and substituents on the ring or solvent and other environmental factors make smaller contributions. Computational estimates by different models vary over a wide range and are sensitive to numerical precision factors for these low reorganization energies. Of current computational models that are widely available and practical for molecules of this size, functionals that contain a mixture of Hartree−Fock exchange and DFT exchange-correlation appear to be the most applicable. ",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/954,
title ="α-Synuclein structures from fluorescence energy-transfer kinetics: Implications for the role of the protein in Parkinson's disease",
author = "Lee, Jennifer C. and Langen, Ralf",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "101",
number = "47",
pages = "16466-16471",
month = "November",
year = "2004",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:LEEpnas04",
note = "© 2004 by the National Academy of Sciences. \n\nContributed by Harry B. Gray, October 4, 2004. \n\nThis work was supported by the Parkinson’s Disease Foundation (J.R.W.), the National Parkinson Foundation (J.R.W.), the Beckman Macular Research Center (H.B.G. and R.L.), and the Arnold and Mabel Beckman Foundation (H.B.G. and J.R.W.), National Institutes of Health Grants GM068461 (to J.R.W.) and P50 AG05142 (to R.L.), and Department of Energy Grant DE-FG02-02ER15359 (to J.R.W.). J.C.L. thanks the Arnold and Mabel Beckman Foundation for a Beckman Senior Research Fellowship.",
revision_no = "9",
abstract = "Parkinson's disease is associated with the deposition and accumulation of alpha-synuclein fibrils in the brain. A30P and A53T mutations have been linked to the early-onset familial disease state. Time-resolved tryptophan fluorescence energy-transfer measurements have been used to probe the structures of pseudo-wild-type and mutant (A30P) alpha-synucleins at physiological pH (7.4), in acidic pH (4.4) solutions, and in the presence of SIDS micelles, a membrane mimic. Fluorescent donor-energy acceptor (DA) distance distributions for six different tryptophan/3-nitro-tyrosine pairs reveal the presence of compact, intermediate, and extended conformations of the protein. CID spectra indicate that the protein develops substantial helical structure in the presence of SIDS micelles. DA distributions show that micelles induce compaction in the N-terminal region and expansion of the acidic C terminus. In acidic solutions, there is an increased population of collapsed structures in the C-terminal region. Energy-transfer measurements demonstrate that the average DA distances for the W4-Y19 and Y19-W39 pairs are longer in one of the two disease-related mutants (A30P).",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/75942,
title ="Conformational States of Cytochrome P450cam Revealed by Trapping of Synthetic Molecular Wires",
author = "Hays, Anna-Maria A. and Dunn, Alexander R.",
journal = "Journal of Molecular Biology",
volume = "344",
number = "2",
pages = "455-469",
month = "November",
year = "2004",
doi = "10.1016/j.jmb.2004.09.046",
issn = "0022-2836",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170408-142602553",
note = "© 2004 Elsevier. \n\nReceived 14 June 2004, Revised 17 September 2004, Accepted 20 September 2004, Available online 5 October 2004. \n\nEdited by R. Huber. \n\nThe authors thank Dr Chris Putnam for discussion and critical reading of the manuscript. In addition, we thank Sophie Coon for providing support for PMV (TSRI). This work was supported by NSF (H.B.G.) and NIH grants GM41049 (to D.B.G.) and GM48495 (to D.B.G. and H.B.G.), and NIH NRSA postdoctoral fellowship GM20703-03 (to A.-M.A.H.). A.R.D. received support from the Fannie and John Hertz Foundation.",
revision_no = "7",
abstract = "Members of the ubiquitous cytochrome P450 family catalyze a vast range of biologically significant reactions in mammals, plants, fungi, and bacteria. Some P450s display a remarkable promiscuity in substrate recognition, while others are very specific with respect to substrate binding or regio and stereo-selective catalysis. Recent results have suggested that conformational flexibility in the substrate access channel of many P450s may play an important role in controlling these effects. Here, we report the X-ray crystal structures at 1.8 Å and 1.5 Å of cytochrome P450cam complexed with two synthetic molecular wires, D-4-Ad and D-8-Ad, consisting of a dansyl fluorophore linked to an adamantyl substrate analog via an α,ω-diaminoalkane chain of varying length. Both wires bind with the adamantyl moiety in similar positions at the camphor-binding site. However, each wire induces a distinct conformational response in the protein that differs from the camphor-bound structure. The changes involve significant movements of the F, G, and I helices, allowing the substrate access channel to adapt to the variable length of the probe. Wire-induced opening of the substrate channel also alters the I helix bulge and Thr252 at the active site with binding of water that has been proposed to assist in peroxy bond cleavage. The structures suggest that the coupling of substrate-induced conformational changes to active-site residues may be different in P450cam and recently described mammalian P450 structures. The wire-induced changes may be representative of the conformational intermediates that must exist transiently during substrate entry and product egress, providing a view of how substrates enter the deeply buried active site. They also support observed examples of conformational plasticity that are believed be responsible for the promiscuity of drug metabolizing P450s. Observation of such large changes in P450cam suggests that substrate channel plasticity is a general property inherent to all P450 structures.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/56980,
title ="Mimicking protein-protein electron transfer: voltammetry of Pseudomonas aeruginosa azurin and the Thermus thermophilus Cu_A domain at ω-derivatized self-assembled-monolayer gold electrodes",
author = "Fujita, Kyoko and Nakamura, Nobufumi",
journal = "Journal of the American Chemical Society",
volume = "126",
number = "43",
pages = "13954-61",
month = "November",
year = "2004",
doi = "10.1021/ja047875o",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150424-154505770",
note = "© 2004 American Chemical Society. \n\nReceived April 13, 2004. Publication Date (Web): October 7, 2004. \n\nDedicated to the memory of Katsumi Niki, who passed away on 4 May 2004, a few weeks after our manuscript was submitted. This work was supported by NIH DK19038, NSF, and the Arnold and Mabel Beckman Foundation. K.F. thanks the Japan Society for Promotion of Science (Research Fellowship for Young Scientists) for support; B.S.L. acknowledges the Parsons Foundation for a graduate fellowship.",
revision_no = "9",
abstract = "Well-defined voltammetric responses of redox proteins with acidic-to-neutral pI values have been obtained on pure alkanethiol as well as on mixed self-assembled-monolayer (SAM) ω-derivatized alkanethiol/gold bead electrodes. Both azurin (P. aeruginosa) (pI = 5.6) and subunit II (CuA domain) of ba_3-type cytochrome c oxidase (T. thermophilus) (pI = 6.0) exhibit optimal voltammetric responses on 1:1 mixtures of [H_3C(CH_2)_nSH + HO(CH_2)_nSH] SAMs. The electron transfer (ET) rate vs distance behavior of azurin and CuA is independent of the ω-derivatized alkanethiol SAM headgroups. Strikingly, only wild-type azurin and mutants containing Trp48 give voltammetric responses:\u2009 based on modeling, we suggest that electronic coupling with the SAM headgroup (H_3C− and/or HO−) occurs at the Asn47 side chain carbonyl oxygen and that an Asn47-Cys112 hydrogen bond promotes intramolecular ET to the copper. Inspection of models also indicates that the CuA domain of ba3-type cytochrome c oxidase is coupled to the SAM headgroup (H_3C− and/or HO−) near the main chain carbonyl oxygen of Cys153 and that Phe88 (analogous to Trp143 in subunit II of cytochrome c oxidase from R. sphaeroides) is not involved in the dominant tunneling pathway. Our work suggests that hydrogen bonds from hydroxyl or other proton-donor groups to carbonyl oxygens potentially can facilitate intermolecular ET between physiological redox partners.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/78016,
title ="Anchoring Group and Auxiliary Ligand Effects on the Binding of Ruthenium Complexes to Nanocrystalline TiO_2 Photoelectrodes",
author = "Kilså, Kristine and Mayo, Elizabeth I.",
journal = "Journal of Physical Chemistry B",
volume = "108",
number = "40",
pages = "15640-15651",
month = "October",
year = "2004",
doi = "10.1021/jp0369995",
issn = "1520-6106",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170607-151847856",
note = "© 2004 American Chemical Society. \n\nReceived: October 6, 2003; In Final Form: April 1, 2004.\nPublication Date (Web): September 11, 2004. \n\nThis work was supported by BP (H.B.G; J.R.W.) and DOE/NREL (N.S.L.). K.K. thanks the Carlsberg Foundation (Denmark) for a postdoctoral fellowship.",
revision_no = "13",
abstract = "The thermodynamics and kinetics of binding to nanocrystalline TiO_2 were investigated for five ruthenium complexes that differed structurally in the number of possible anchoring carboxy groups (one, two, four, or six) attached to coordinated bipyridyl ligands and in the number of auxiliary ligands (bipyridine, CN-, or SCN-). Diffuse reflectance infrared spectroscopic data indicated that the dyes predominantly bound to TiO_2 in a bridging mode in which the oxygen atoms of an attached carboxy group were bound to separate titanium atoms on the TiO_2 surface. Furthermore, in the dry state, complexes with only one monocarboxy or dicarboxy ligand used essentially all of their available carboxy groups to bind to the surface. However, complexes having two or three dicarboxy ligands used on average two carboxylato groups in binding to TiO_2. The structural differences between the complexes were manifested chemically in that the five dyes yielded similar maximum coverages (>100 nmol cm^(-2)) on nanocrystalline TiO_2 electrodes, but exhibited different binding constants (10^3−10^5 M^(-1)) and different adsorption and desorption kinetics (3−11) × 10^3 M^(-1) h^(-1) and 1−100 h, respectively). The binding constant for the monocarboxy dye was significantly lower than the binding constants for dyes with dicarboxy ligands, correlating primarily with an increase in the desorption rate of the monocarboxy complex. The adsorption rate constants were similar for all of the dyes, suggesting that formation of the first bond to TiO_2 was rate limiting. Binding of the dyes from an ethanolic solution that contained pyridine and pyridinium as an acidic proton activity buffer yielded lower coverages than binding from a nonbuffered ethanol solution, even though the binding constants were up to 100 times greater under buffered conditions. The lower equilibrium dye coverage in buffered ethanol did not correlate with changes in the protonation state of the dyes but rather indicated competition for, and/or deactivation of, TiO_2 active sites in buffered ethanol. The more weakly bound monocarboxy dye displayed the lowest short-circuit current density and open-circuit voltage under simulated solar illumination in a photoelectrochemical cell containing 0.50 M LiI, 0.040 M I_2, 0.020 M pyridine, and 0.020 M pyridinium triflate in acetonitrile. Additionally, even at constant coverage, the integrated quantum yield for photocurrent flow was lowest for TiO_2 sensitized with the monocarboxy dye. The potential required to drive 0.1 mA cm^(-2) of cathodic current density in the dark on dye-sensitized TiO_2 photoelectrodes was least negative for the monocarboxy dye, indicating more facile electron transfer between reduced TiO_2 and the solution redox couple. Hence, in this series of ruthenium carboxy-bipyridyl dyes, the most weakly bound species (i.e., the monocarboxy dye) yielded inferior photoelectrode properties, whereas differences between the dyes that contained at least one dicarboxy ligand resulted primarily from differences in the light absorption and energetic properties of the metal complexes. These observations suggest an important role for the linkage to the TiO_2 surface in achieving temporal stability as well as in tuning both the steady-state quantum yield and the magnitude of the predominant back-reaction rate in dye-sensitized TiO_2-based photoelectrochemical solar cells.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77837,
title ="α-Synuclein: Stable compact and extended monomeric structures and pH dependence of dimer formation",
author = "Bernstein, Summer L. and Liu, Dengfeng",
journal = "Journal of the American Society for Mass Spectrometry",
volume = "15",
number = "10",
pages = "1435-1443",
month = "October",
year = "2004",
doi = "10.1016/j.jasms.2004.08.003",
issn = "1044-0305",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170530-153130423",
note = "© 2004 American Society for Mass Spectrometry. \n\nReceived: 14 April 2004; Revised: 05 August 2004; Accepted: 09 August 2004; First Online: 01 October 2004. \n\nThis research was supported by a grant from the National Science Foundation, CHE-0140215 (MTB), Beckman Macular Research Center (HBG), Parkinson’s Disease Foundation and National Parkinson Foundation (JRW), and the Beckman Foundation for a Beckman Senior Research Fellowship (JCL).",
revision_no = "9",
abstract = "The protein α-synuclein, implicated in Parkinson’s disease, was studied by combining nano-electrospray ionization (N-ESI) mass spectrometry and ion mobility. It was found that both the charge-state distribution in the mass spectra and the average protein shape deduced from ion mobility data, depend on the pH of the spray solution. Negative-ion N-ESI of pH 7 solutions yielded a broad charge-state distribution from −6 to −16, centered at −11, and ion mobility data consistent with extended protein structures. Data obtained for pH 2.5 solutions, on the other hand, showed a narrow charge-state distribution from −6 to −11, centered at −8, and ion mobilities in agreement with compact α-synuclein structures. The data indicated that there are two distinct families of structures: one consisting of relatively compact proteins with eight or less negative charges and one consisting of relatively extended structures with nine or more charges. The average cross section of a-synuclein at pH 2.5 is 33% smaller than for the extended protein sprayed from pH 7 solution. Significant dimer formation was observed when sprayed from pH 7 solution but no dimers were observed from the low pH solution. A plausible mechanism for aggregate formation in solution is proposed.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/88996,
title ="Cobaltocene-mediated catalytic monooxygenation using holo and heme domain cytochrome P450 BM3",
author = "Udit, Andrew K. and Arnold, Frances H.",
journal = "Journal of Inorganic Biochemistry",
volume = "98",
number = "9",
pages = "1547-1550",
month = "September",
year = "2004",
doi = "10.1016/j.jinorgbio.2004.06.007",
issn = "0162-0134",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180821-155119382",
note = "© 2004 Elsevier Inc. \n\nReceived 4 May 2004, Revised 7 June 2004, Accepted 15 June 2004, Available online 5 August 2004. \n\nSusan Schofer (Caltech) for assistance with the chemical synthesis; Mike Hill (Occidental College) for helpful discussions; NSF (HBG) and NSERC (Canada) (AKU) for research support.",
revision_no = "12",
abstract = "The feasibility of replacing NADPH with 1,1′-dicarboxycobaltocene in the catalytic cycle of cytochrome P450 BM3 has been explored. Using the holoprotein, the surrogate mediator was observed to reduce both the FAD and FMN in the reductase domain, as well as the iron in the heme domain. In an electrochemical system, the mediator was able to support lauric acid hydroxylation at a rate of 16.5 nmol product/nmol enzyme/minute. Similar electron transfer and catalysis were observed for the heme domain alone in the presence of the metallocene; the turnover rate in this case was 1.8 nmol product/nmol enzyme/minute. Parallel studies under the same conditions using a previously reported cobalt sepulchrate mediator showed that the two systems give similar results for both the holoenzyme and the heme domain.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/76960,
title ="Reduction of Dioxygen Catalyzed by Pyrene-Wired Heme Domain Cytochrome P450 BM3 Electrodes",
author = "Udit, Andrew K. and Hill, Michael G.",
journal = "Journal of the American Chemical Society",
volume = "126",
number = "33",
pages = "10218-10219",
month = "August",
year = "2004",
doi = "10.1021/ja0466560",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170426-144912333",
note = "© 2004 American Chemical Society. \n\nReceived June 7, 2004. Publication Date (Web): August 3, 2004. \n\nWe thank J. S. Magyar and J. R. Winkler (Caltech), T. L. Poulos (U.C. Irvine), and E. M. Spain (Occidental College) for helpful discussions; C. P. Collier (Caltech) for assistance with the AFM; NSF (H.B.G.), NSERC (Canada) (A.K.U.), and David and Lucile Packard Foundation (M.G.H.) for research support.",
revision_no = "16",
abstract = "We have electronically wired the cytochrome P450 BM3 heme domain to a graphite electrode with the use of a pyrene-terminated tether. AFM images clearly reveal that pyrene-wired enzyme molecules are adsorbed to the electrode surface. The enzyme-electrode system undergoes rapid and reversible electron transfer, displaying a standard rate constant higher than that of any other P450-electrode system. We also show that the graphite-pyrene-BM3 system catalyzes the four-electron reduction of dioxygen to water.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/76893,
title ="Excited-State Dynamics offac-[Re^I(L)(CO)_3(phen)]^+ and fac-[Re^I(L)(CO)_3(5-NO_(2-)phen)]^+(L = Imidazole, 4-Ethylpyridine; Phen = 1,10-Phenanthroline) Complexes",
author = "Busby, Michael and Gabrielsson, Anders",
journal = "Inorganic Chemistry",
volume = "43",
number = "16",
pages = "4994-5002",
month = "August",
year = "2004",
doi = "10.1021/ic035471b",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170425-065431541",
note = "© 2004 American Chemical Society. \n\nReceived 20 December 2003. Published online 10 July 2004. Published in print 1 August 2004. \n\nMajid Motevalli (QMUL) determined the crystal structure of [Re^I(4-Etpy)(CO)_3(5-NO_(2-)phen)]PF_6. We thank Mona Shahgholi, David Jenkins, and Larry Henling for helpful discussions. Time-resolved visible absorption spectra were measured with the kind help of Mikhail Zimin and M. Groeneveld at the Institute of Molecular Chemistry, University of Amsterdam, The Netherlands. I. P. Clark assisted with resonance Raman experiments at the LSF Nanosecond Laboratory at RAL. This work was supported by the EPSRC, COST Action D14 European collaboration program and NIH (DK19038).",
revision_no = "13",
abstract = "The nature and dynamics of the lowest excited states of fac-[Re^I(L)(CO)_3(phen)]^+ and fac-[Re^I(L)(CO)_3(5-NO_2-phen)]^+ [L = Cl-, 4-ethyl-pyridine (4-Etpy), imidazole (imH); phen = 1,10-phenanthroline] have been investigated by picosecond visible and IR transient absorption spectroscopy in aqueous (L = imH), acetonitrile (L = 4-Etpy, imH), and MeOH (L = imH) solutions. The phen complexes have long-lived Re^I → phen ^3MLCT excited states, characterized by CO stretching frequencies that are upshifted relative to their ground-state values and by widely split IR bands due to the out-of-phase A‘(2) and A‘\u2009‘ ν(CO) vibrations. The lowest excited states of the 5-NO_(2-)phen complexes also have ^3MLCT character; the larger upward ν(CO) shifts accord with much more extensive charge transfer from the Re^I(CO)_3 unit to 5-NO_(2-)phen in these states. Transient visible absorption spectra indicate that the excited electron is delocalized over the 5-NO_(2-)phen ligand, which acquires radical anionic character. Similarly, involvement of the -NO_2 group in the Franck−Condon MLCT transition is manifested by the presence of an enhanced ν(NO_2) band in the preresonance Raman spectrum of [Re^I(4-Etpy)(CO)_3(5-NO_(2-)phen)]^+. The Re^I → 5-NO_(2-)phen ^3MLCT excited states are very short-lived:\u2009 7.6, 170, and 43 ps for L = Cl-, 4-Etpy, and imH, respectively, in CH_3CN solutions. The ^3MLCT excited state of [Re^I(imH)(CO)_3(5-NO_(2-)phen)]^+ is even shorter-lived in MeOH (15 ps) and H_2O (1.3 ps). In addition to ^3MLCT, excitation of [Re^I(imH)(CO)_3(5-NO_(2-)phen)]^+ populates a ^3LLCT (imH → 5-NO_(2-)phen) excited state. Most of the ^3LLCT population decays to the ground state (time constants of 19 (H_2O), 50 (MeOH), and 72 ps (CH_3CN)); in a small fraction, however, deprotonation of the imH^(•+) ligand occurs, producing a long-lived species, [Re^I(im^•)(CO)_3(5-NO_(2-)phen)^(•-)]^+.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/73706,
title ="Amphiphilic Corroles Bind Tightly to Human Serum Albumin",
author = "Mahammed, Atif and Gray, Harry B.",
journal = "Bioconjugate Chemistry",
volume = "15",
number = "4",
pages = "738-746",
month = "July",
year = "2004",
doi = "10.1021/bc034179p",
issn = "1043-1802",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170125-093851899",
note = "© 2004 American Chemical Society.\n\nReceived 30 September 2003;\nPublished online 19 June 2004;\nPublished in print 1 July 2004.\n\nWork at the Technion was supported by the STAR (Chicago) Foundation (Z.G.) and the Israel Science Foundation (Z.G.); work at Caltech was supported by JPL-NASA (K.S.) and the National Science Foundation (H.B.G., J.J.W.).",
revision_no = "12",
abstract = "Amphiphilic 2,17-bis-sulfonato-5,10,15(trispentafluorophenyl)corrole (2) and its Ga and Mn complexes (2-Ga and 2-Mn) form tightly bound noncovalent conjugates with human serum albumin (HSA). Protein-induced changes in the electronic absorption, emission, and circular dichroism spectra of these corroles, as well as results obtained from HPLC profiles of the conjugates and selective fluorescence quenching of the single HSA tryptophan, are interpreted in terms of multiple corrole:HSA binding sites. High-affinity binding sites, close to the unique tryptophan, are fully occupied at very low concentrations. At biologically relevant HSA concentrations (2−3 orders of magnitude larger than those employed in our studies), all corroles (2, 2-Ga, and 2-Mn) may be considered as fully conjugated.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/76894,
title ="Electron-Transfer Chemistry of Ru−Linker−(Heme)-Modified Myoglobin: Rapid Intraprotein Reduction of a Photogenerated Porphyrin Cation Radical",
author = "Immoos, Chad E. and Di Bilio, Angel J.",
journal = "Inorganic Chemistry",
volume = "43",
number = "12",
pages = "3593-3596",
month = "June",
year = "2004",
doi = "10.1021/ic049741h",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170425-071456736",
note = "© 2004 American Chemical Society. \n\nReceived 28 February 2004. Published online 29 April 2004. Published in print 1 June 2004. \n\nWe thank Kevin Heinrich, David Khandabi, and Greg Quishair for assistance with the synthesis of RuC7. C.E.I. thanks the UC TSR & TP for a graduate fellowship. M.S.C. thanks the Arnold and Mabel Beckman Undergraduate Scholarship Fund for support. This work was supported by the NSF (P.J.F., Grant CHE-0100774), UROP funding from UCI, and the NIH (H.B.G., Grant DK19038).",
revision_no = "12",
abstract = "We report the synthesis and characterization of RuC7, a complex in which a heme is covalently attached to a [Ru(bpy)_3]^(2+) complex through a −(CH_2)_7− linker. Insertion of RuC7 into horse heart apomyoglobin gives RuC7Mb, a Ru(heme)−protein conjugate in which [Ru(bpy)_3]^(2+) emission is highly quenched. The rate of photoinduced electron transfer (ET) from the resting (Ru^(2+)/Fe^(3+)) to the transient (Ru^(3+)/Fe^(2+)) state of RuC7Mb is >10^8 s^(-1); the back ET rate (to regenerate Ru^(2+)/Fe^(3+)) is 1.4 × 10^7 s^(-1). Irreversible oxidative quenching by [Co(NH_3)_5Cl]^(2+) generates Ru^(3+)/Fe^(3+):\u2009 the Ru^(3+) complex then oxidizes the porphyrin to a cation radical (P^(•+)); in a subsequent step, P^(•+) oxidizes both Fe^(3+) (to give Fe^(IV)═O) and an amino acid residue. The rate of intramolecular reduction of P^(•+) is 9.8 × 10^3 s^(-1); the rate of ferryl formation is 2.9 × 10^3 s^(-1). Strong EPR signals attributable to tyrosine and tryptophan radicals were recorded after RuC7MbM^(3+) (M = Fe, Mn) was flash-quenched/frozen.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/51798,
title ="Oxoiron(IV) in Chloroperoxidase Compound II Is Basic: Implications for P450 Chemistry",
author = "Green, Michael T. and Dawson, John H.",
journal = "Science",
volume = "304",
number = "5677",
pages = "1653-1656",
month = "June",
year = "2004",
doi = "10.1126/science.1096897",
issn = "0036-8075",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20141114-143753781",
note = "© 2004 American Association for the Advancement of Science.\n\n18 February 2004; Accepted 21 April 2004.\n\nWe thank M. Bollinger, I. Dmochowski, J. Labinger, M.\nMachczynski, M. McGuirl, A. Tezcan, and J. Winkler for\nhelpful discussions; G. George, I. Pickering, M. Latimer, B. Butler, A. Soo Hoo, S. Debeer George, D. Durkin, and other SSRL staff members for assistance with XAS measurements; and L. Hager for a CPO sample used in the initial experiments. Supported by NIH (GM26730 to J.H.D. and DK19038 to H.B.G.), NSF, and the Arnold and Mabel Beckman Foundation.",
revision_no = "9",
abstract = "With the use of x-ray absorption spectroscopy, we have found that the Fe-O bond in chloroperoxidase compound II (CPO-II) is much longer than expected for an oxoiron(IV) (ferryl) unit; notably, the experimentally determined bond length of 1.82(1) Å accords closely with density functional calculations on a protonated ferryl (Fe^(IV)-OH, 1.81 Å). The basicity of the CPO-II ferryl [pK_a > 8.2 (where K_a is the acid dissociation constant)] is attributable to strong electron donation by the axial thiolate. We suggest that the CPO-II protonated ferryl is a good model for the rebound intermediate in the P450 oxygenation cycle; with elevated pK_a values after one-electron reduction, thiolate-ligated ferryl radicals are competent to oxygenate saturated hydrocarbons at potentials that can be tolerated by folded polypeptide hosts.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/66782,
title ="Mechanism of Sequence-Specific Fluorescent Detection of DNA by N-Methyl-imidazole, N-Methyl-pyrrole, and β-Alanine Linked Polyamides",
author = "Rucker, Victor C. and Dunn, Alexander R.",
journal = "Journal of Physical Chemistry B",
volume = "108",
number = "22",
pages = "7490-7494",
month = "June",
year = "2004",
doi = "10.1021/jp037423i",
issn = "1520-6106",
url = "https://pubs.acs.org/doi/abs/10.1021/jp037423i",
note = "© 2004 American Chemical Society. \n\nReceiVed: NoVember 10, 2003; In Final Form: March 8, 2004. Publication Date (Web): May 4, 2004. \n\nWe wish to thank Dr. J. R. Winkler for assistance with data fitting and helpful discussions. This work was supported by the NSF (H.B.G.), National Institutes of Health (V.R.; training grant GM19789-02) and by the Fannie and John Hertz Foundation (A.R.D.).",
revision_no = "13",
abstract = "The fluorescence from the tetramethylrhodamine (TMR) moiety in hairpin polyamide−TMR conjugates is quenched in solution, but restored upon sequence-specific binding to doubled-stranded DNA. This fluorescence amplification when bound to the target DNA sequence makes polyamide−TMR conjugates potentially useful for the detection of specific DNA sequences in homogeneous solution. Time-resolved and steady-state spectroscopic measurements indicate that a ground-state complex forms between the TMR and polyamide functionalities in the absence of DNA. This intramolecular complex likely facilitates electron transfer from the polyamide N-methyl-pyrrole moieties to the TMR excited state, quenching fluorescence. Binding of the polyamide−TMR probe to the target DNA sequence disrupts the TMR−polyamide interaction, resulting in the observed fluorescence increase.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/76694,
title ="X-ray Magnetic Circular Dichroism of Pseudomonas aeruginosa Nickel(II) Azurin",
author = "Funk, Tobias and Kennepohl, Pierre",
journal = "Journal of the American Chemical Society",
volume = "126",
number = "18",
pages = "5859-5866",
month = "May",
year = "2004",
doi = "10.1021/ja036218d",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170419-130605884",
note = "© 2004 American Chemical Society. \n\nReceived 19 May 2003. Published online 20 April 2004. Published in print 1 May 2004. \n\nWe thank Rene Delano and the ALS staff for excellent technical support. We also thank Dr. Pieter Glatzel and Dr. Frank de Groot for helpful discussions. This work was supported by NIH (GM4430 and DK19038) and the U.S. Department of Energy (Office of Biological and Environmental Research).",
revision_no = "14",
abstract = "We show that X-ray magnetic circular dichroism (XMCD) can be employed to probe the oxidation states and other electronic structural features of nickel active sites in proteins. As a calibration standard, we have measured XMCD and X-ray absorption (XAS) spectra for the nickel(II) derivative of Pseudomonas aeruginosa azurin (NiAz). Our analysis of these spectra confirms that the electronic ground state of NiAz is high-spin (S = 1); we also find that the L3-centroid energy is 853.1(1) eV, the branching ratio is 0.722(4), and the magnetic moment is 1.9(4) μ_B. Density functional theory (DFT) calculations on model NiAz structures establish that orbitals 3d_x^2-y^2 and 3d_z^2 are the two valence holes in the high-spin Ni(II) ground state, and in accord with the experimentally determined orbital magnetic moment, the DFT results also demonstrate that both holes are highly delocalized, with 3d_x^2_(-y)^2 having much greater ligand character.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77846,
title ="Electron tunneling in rhenium-modified Pseudomonas aeruginosa azurins",
author = "Miller, Jeremiah E. and Di Bilio, Angel J.",
journal = "Biochimica et Biophysica Acta (BBA) - Bioenergetics",
volume = "1655",
pages = "59-63",
month = "April",
year = "2004",
doi = "10.1016/j.bbabio.2003.06.010",
issn = "0005-2728",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170531-085753394",
note = "© 2004 Elsevier B.V. \n\nReceived 24 April 2003, Revised 26 June 2003, Accepted 26 June 2003, Available online 7 January 2004. \n\nOur research on electron tunneling in proteins is supported by NIH grant DK19038.",
revision_no = "9",
abstract = "Laser flash-quench methods have been used to generate tyrosine and tryptophan radicals in structurally characterized rhenium-modified Pseudomonas aeruginosa azurins. Cu(I) to “Re(II)” electron tunneling in Re(H107) azurin occurs in the microsecond range. This reaction is much faster than that studied previously for Cu(I) to Ru(III) tunneling in Ru(H107) azurin, suggesting that a multistep (“hopping”) mechanism might be involved. Although a Y108 radical can be generated by flash-quenching a Re(H107)M(II) (M=Cu, Zn) protein, the evidence suggests that it is not an active intermediate in the enhanced Cu(I) oxidation. Rather, the likely explanation is rapid conversion of Re(II)(H107) to deprotonated Re(I)(H107 radical), followed by electron tunneling from Cu(I) to the hole in the imidazole ligand.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/76907,
title ="Photoswitchable Luminescence of Rhenium(I) Tricarbonyl Diimines",
author = "Wenger, Oliver S. and Henling, Lawrence M.",
journal = "Inorganic Chemistry",
volume = "43",
number = "6",
pages = "2043-2048",
month = "March",
year = "2004",
doi = "10.1021/ic030324zd",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170425-095907901",
note = "© 2004 American Chemical Society. \n\nReceived 17 November 2003. Published online 17 February 2004. Published in print 1 March 2004. \n\nThis work was supported by the National Science Foundation. O.S.W. acknowledges a postdoctoral fellowship from the Swiss National Science Foundation.",
revision_no = "12",
abstract = "The synthesis, characterization, and X-ray crystal structures of [Re(diimine)(CO)_3(dpe)](PF_6) (dpe = 1,2-di(4-pyridyl)ethylene) compounds are reported. The cis-dpe complexes exhibit yellow luminescence after UV excitation, whereas the trans-dpe counterparts are nonluminescent. The luminescence quantum yields of the cis-dpe complexes are strongly dependent on the identity of the diimine ligand. Irradiation (350 nm) of the trans-dpe complexes induces trans → cis dpe-ligand isomerization with quantum yields on the order of 0.2, and this process leads to an on-switching of yellow luminescence. After long 350-nm irradiation times, a steady state composed of roughly 70% cis- and 30% trans-dpe complexes is reached. The reverse cis → trans photoisomerization reaction is induced by irradiating the cis-dpe complexes at 250 nm, switching off the yellow luminescence. For 250-nm excitation, photodecomposition of the [Re(diimine)(CO)_3(dpe)]^+ complexes competes efficiently with photoisomerization.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/86302,
title ="Oxidations Catalyzed by Metallocorroles",
author = "Gross, Zeev and Gray, Harry B.",
journal = "Advanced Synthesis and Catalysis",
volume = "346",
number = "2-3",
pages = "165-170",
month = "February",
year = "2004",
doi = "10.1002/adsc.200303145",
issn = "1615-4150",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180509-074211376",
note = "© 2004 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim. \n\nIssue Online: 29 March 2004; Version of Record online: 29 March 2004; Manuscript accepted: 12 December 2003; Manuscript received: 17 September 2003. \n\nWork at the Technion was supported by the Petroleum Research Fund and the Israel National Science Foundation. Work at the California Institute of Technology was supported by the United States National Science Foundation. We acknowledge with thanks the many important contributions of Professor I. Goldberg from the TelAviv University (Israel) as well as those of our talented and highly devoted students and coworkers at the Technion (N. Galili, I. Saltsman, L. Simkhovich, A. Mahammed, G. Golubkov, E. Tkachenko, P. Iyer) and Caltech (A. E. Meier-Callahan, J. Bendix, A. J. Di Bilio).",
revision_no = "10",
abstract = "Metallocorroles, in particular those containing chromium, manganese, and iron, have been found to be efficient catalysts for oxidation reactions. This review deals with work on hydrocarbon oxidations after the 1999 advance made in corrole synthesis that sparked the Technion‐Caltech collaborative program.",
}
@book_section {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/98353,
title ="Electronic Structures and Reduction Potentials of Cu(II) Complexes of [N,N′-Alkyl-bis(ethyl-2-amino-1-cyclopentenecarbothioate)] (Alkyl=Ethyl, Propyl, and Butyl)",
author = "Contreras, Ricardo R. and Suárez, Trino",
number = "106",
pages = "71-79",
month = "January",
year = "2004",
doi = "10.1007/b11306",
issn = "0081-5993",
isbn = "9783540008538",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20190829-131534243",
note = "© Springer-Verlag Berlin Heidelberg 2004. \n\nThis work was supported by CDCHT-ULA (C-1108–01-A), the NSF, NIH, and the Arnold and Mabel Beckman Foundation.",
revision_no = "9",
abstract = "Copper(II) complexes of N,N’-alkyl-bis(ethyl-2-amino-1-cyclopentenecarbodithioate) [alkyl=ethyl (L2), propyl (L3), and butyl(L4)] ligands have been synthesized and characterized. Analytical data for all three complexes show 1:1 copper-ligand stoichiometry. Well-resolved EPR spectra were recorded in toluene, benzene, and methylene chloride solutions at room temperature and in glassy toluene or toluene-methylene chloride mixtures in the range 20–150 K. The superhyperfine pattern unambiguously demonstrates coordination of two nitrogen atoms to copper; and the spin-Hamiltonian parameters [CuL2, g_∥=2.115, A_∥=187×10^(–4) cm^(–1); CuL3, g_∥=2.128, A_∥=165×10^(–4) cm^(–1); CuL4, g_∥=2.138, A_∥=147×10^(–4) cm^(–1)] are as expected for a CuN_2S_2 coordination core. Quasi-reversible electrochemical behavior was observed in methylene chloride: the Cu(II)/Cu(I) reduction potentials increase from –1.17 V (E° vs Ag/AgNO_3) for CuL2 to –0.74 V for CuL4, indicating greater stabilization of Cu(I) in CuL4. Taken together, these data demonstrate that lengthening the N,N′-alkyl chain distorts the planar CuN_2S_2 core (CuL2) toward a flattened tetrahedral geometry (CuL4).",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/76695,
title ="Spectroscopy and Reactivity of a Photogenerated Tryptophan Radical in a Structurally Defined Protein Environment",
author = "Miller, Jeremiah E. and Grǎdinaru, Cristian",
journal = "Journal of the American Chemical Society",
volume = "125",
number = "47",
pages = "14220-14221",
month = "November",
year = "2003",
doi = "10.1021/ja037203i",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170419-130606164",
note = "© 2003 American Chemical Society. \n\nReceived 10 July 2003. Published online 1 November 2003. Published in print 1 November 2003. \n\nRandy Villahermosa assisted with the transient absorption measurements. J.E.M. thanks the Parsons Foundation for a graduate fellowship. Work at Cornell was supported by NSF (MCB0133546); work at Caltech was supported by NIH (DK19038).",
revision_no = "13",
abstract = "Near-UV irradiation of structurally characterized [Re(I)(CO)_3(1,10-phenanthroline)(Q107H)](W48F/Y72F/H83Q/Y108W)AzM(II) [Az = Pseudomonas aeruginosa azurin, M = Cu, Zn]/[Co(NH_3)_5Cl]Cl_2 produces a tryptophan radical (W108•) with unprecedented kinetic stability. After rapid formation (k = 2.8 × 10^6 s^(-1)), the radical persists for more than 5 h at room temperature in the folded ReAzM(II) structure. The absorption spectrum of ReAz(W108•)M(II) exhibits maxima at 512 and 536 nm. Oxidation of K_4[Mo(CN)_8] by ReAz(W108•)Zn(II) places the W108•/W108 reduction potential in the protein above 0.8 V vs NHE.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77478,
title ="Nanosecond Photoreduction of Cytochrome P450cam by Channel-Specific Ru-diimine Electron Tunneling Wires",
author = "Dunn, Alexander R. and Dmochowski, Ivan J.",
journal = "Journal of the American Chemical Society",
volume = "125",
number = "41",
pages = "12450-12456",
month = "October",
year = "2003",
doi = "10.1021/ja0294111",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170516-065837544",
note = "© 2003 American Chemical Society. \n\nReceived 19 November 2002. Published online 23 September 2003. Published in print 1 October 2003. \n\nThis work was supported by the Fannie and John Hertz Foundation (A.R.D.), the National Institutes of Health predoctoral program (I.J.D.), NSF CHE-0111416, and NIH DK19038.",
revision_no = "14",
abstract = "We report the synthesis and characterization of Ru-diimine complexes designed to bind to cytochrome P450cam (CYP101). The sensitizer core has the structure [Ru(L_2)L‘]^(2+), where L‘ is a perfluorinated biphenyl bridge (F_8bp) connecting 4,4‘-dimethylbipyridine to an enzyme substrate (adamantane, F_8bp-Ad), a heme ligand (imidazole, F_8bp-Im), or F (F_9bp). The electron-transfer (ET) driving force (−ΔG°) is varied by replacing the ancillary 2,2‘-bipyridine ligands with 4,4‘,5,5‘-tetramethylbipyridine (tmRu). The four complexes all bind P450cam tightly:\u2009 Ru−F_8bp-Ad (1, K_d = 0.077 μM); Ru−F_8bp-Im (2, K_d = 3.7 μM); tmRu−F_9bp (3, K_d = 2.1 μM); and tmRu−F_8bp-Im (4, Kd = 0.48 μM). Binding is predominantly driven by hydrophobic interactions between the Ru-diimine wires and the substrate access channel. With Ru−F_8bp wires, redox reactions can be triggered on the nanosecond time scale. Ru-wire 2, which ligates the heme iron, shows a small amount of transient heme photoreduction (ca. 30%), whereas the transient photoreduction yield for 4 is 76%. Forward ET with 4 occurs in roughly 40 ns (k_f = 2.8 × 10^7 s^(-1)), and back ET (Fe^(II) → Ru^(III), k_b ≈ 1.7 × 10^8 s^(-1)) is near the coupling-limited rate (k_(max)). Direct photoreduction was not observed for 1 or 3. The large variation in ET rates among the Ru-diimine:P450 conjugates strongly supports a through-bond model of Ru−heme electronic coupling.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/57055,
title ="Coupling to Lysine-13 Promotes Electron Tunneling through Carboxylate-Terminated Alkanethiol Self-Assembled Monolayers to Cytochrome c",
author = "Niki, Katsumi and Hardy, W. Reef",
journal = "Journal of Physical Chemistry B",
volume = "107",
number = "37",
pages = "9947-9949",
month = "September",
year = "2003",
doi = "10.1021/jp035392l",
issn = "1520-6106",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150428-140736351",
note = "© 2003 American Chemical Society.\n\nReceived: May 20, 2003.\n\nThe authors thank Dojindo Molecular Technology for providing carboxylic acid-terminated alkanethiols. Work at Occidental College was supported by the David and Lucille Packard Foundation’s Initiative for Interdisciplinary Research. Work at Caltech was supported by NIH DK19038, NSF, and the Arnold and Mabel Beckman Foundation. E.M., H.L., and JS acknowledge support from the Edward Mallinckrodt, Jr. Foundation. K.F. thanks the Japan Society for the Promotion of Science (Research Fellowships for Young Scientists) for support.",
revision_no = "13",
abstract = "Electrochemistry of surface-modified cytochrome c (cyt c) bound electrostatically to carboxylate-terminated alkanethiol self-assembled monolayers (SAM) reveals highly anisotropic electronic coupling across the protein/monolayer interface. Substitution of a lysine residue with alanine at position 13 in recombinant rat cyt c (RC9-K13A) lowers the interfacial electron transfer (ET) rate more than 5 orders of magnitude, whereas ET is only slightly affected by replacement of lysine-72 or lysine-79 with alanine. The results clearly show that lysine-13 is directly involved in coupling the protein to the SAM carboxylate terminus. Interfacial ET rates for both yeast iso-1 cyt c and the mutant RC9-K13R indicate that arginine-13 couples the protein to the carboxylate interface less well than lysine-13.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/20957,
title ="Chromium\n",
author = "Gray, Harry B.",
journal = "Chemical and Engineering News",
volume = "81",
number = "36",
pages = "74-74",
month = "September",
year = "2003",
issn = "0009-2347",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20101122-122037793",
note = "© 2003 American Chemical Society.",
revision_no = "13",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/76574,
title ="Gold Electrodes Wired for Coupling with the Deeply Buried Active Site of Arthrobacter globiformis Amine Oxidase",
author = "Hess, Corinna R. and Juda, Gregory A.",
journal = "Journal of the American Chemical Society",
volume = "125",
number = "24",
pages = "7156-7157",
month = "June",
year = "2003",
doi = "10.1021/ja029538q",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170414-134610908",
note = "© 2003 American Chemical Society. \n\nReceived 1 December 2002. Published online 22 May 2003. Published in print 1 June 2003. \n\nThis work is dedicated to the memory of Eraldo Antonini (per il ventesimo anniversario della sua morte, 19 Marzo 2003), a giant in metallobiochemistry. We thank R. Tanimura and K. Niki for assistance in the preparation of Au-bead electrodes and for helpful discussions. This work was supported by NIH (C.R.H., J.R.W., H.B.G., G.A.J., D.M.D.) and the David and Lucille Packard Foundation Initiative for Interdisciplinary Research (R.N.A., M.G.H.).",
revision_no = "11",
abstract = "Diethylaniline-terminated oligo(phenyl-ethynyl)-thiol (DEA-OPE-SH) wires on Au-bead electrodes facilitate electron tunneling to and from the deeply buried topaquinone (TPQ) cofactor in Arthrobacter globiformis amine oxidase (AGAO). Reversible cyclic voltammograms were observed when AGAO was adsorbed onto this DEA-OPE-SAu surface:\u2009 the 2e^-/2H^+ reduction potential is −140 mV versus SCE.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77840,
title ="^(15)N-^1H Residual Dipolar Coupling Analysis of Native and Alkaline-K79A Saccharomyces cerevisiae Cytochrome c",
author = "Assfalg, Michael and Bertini, Ivano",
journal = "Biophysical Journal",
volume = "84",
number = "6",
pages = "3917-3923",
month = "June",
year = "2003",
doi = "10.1016/S0006-3495(03)75119-4",
issn = "0006-3495",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170530-161349767",
note = "© 2003 The Biophysical Society. Published by Elsevier Inc. \n\nReceived 27 September 2002, Accepted 21 January 2003. \n\nWe thank Federico Rosell for providing samples of K79A cytochrome c. \n\nWe acknowledge support from the Ministero dell’Istruzione, dell’Università e della Ricerca, Cofinanziamento 2001 MIUR COFIN2001) and European Community Network (grant FMRX-CT98-0218 to I.B.); Italian Consiglio Nazionale delle Richerche (Progetto Finalizzato Biotecnologie grant 01.00359.PF49 to P.T.); operating grant MT-14021 from the Canadian Institutes of Health Research and a Canada Research Chair (to A.G.M.); United States National Institutes of Health grant DK19038 (to H.B.G.); and Department of Energy grant DE-FG03-02ER15359 (to J.R.W.).",
revision_no = "12",
abstract = "Residual dipolar couplings (RDCs) and pseudocontact shifts are experimentally accessible properties in nuclear magnetic resonance that are related to structural parameters and to the magnetic susceptibility anisotropy. We have determined RDCs due to field-induced orientation of oxidized-K79A and reduced cytochrome c at pH 7.0 and oxidized-K79A cytochrome c at pH 11.1 through measurements of amide ^(15)N-^1H ^1J couplings at 800 and 500 MHz. The pH 7.0 RDCs for Fe(III)- and Fe(II)-cytochrome c together with available nuclear Overhauser effects were used to recalculate solution structures that were consistent with both sets of constraints. Molecular magnetic susceptibility anisotropy values were calculated for both redox states of the protein. By subtracting the residual dipolar couplings (RDCs) of the reduced form from those of the oxidized form measured at the same magnetic field (800 MHz), we found the RDC contribution of the paramagnetic metal ion in the oxidized protein. The magnetic susceptibility anisotropy, which was calculated from the structure, was found to be the same as that of the paramagnetic metal ion obtained independently from pseudocontact shifts, thereby indicating that the elements of secondary structure either are rigid or display the same mobility in both oxidation states. The residual dipolar coupling values of the alkaline-K79A form are small with respect to those of oxidized native cytochrome, whereas the pseudocontact shifts are essentially of the same magnitude, indicating local mobility. Importantly, this is the first time that mobility has been found through comparison of RDCs with pseudocontact shifts.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77609,
title ="Effects of Bridging Ligands on the Current−Potential Behavior and Interfacial Kinetics of Ruthenium-Sensitized Nanocrystalline TiO_2 Photoelectrodes",
author = "Kilså, Kristine and Mayo, Elizabeth I.",
journal = "Journal of Physical Chemistry A",
volume = "107",
number = "18",
pages = "3379-3383",
month = "May",
year = "2003",
doi = "10.1021/jp021921u",
issn = "1089-5639",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170519-142727736",
note = "© 2003 American Chemical Society. \n\nReceived 21 August 2002. Published online 11 April 2003. Published in print 1 May 2003. \n\nK.K. thanks the Carlsberg Foundation, Denmark, for a postdoctoral fellowship, and R.V. acknowledges the Link Foundation for funding. This work is supported through NREL subcontract (ACQ-1-30619-09) under DOE contract (DE-AC36-99-G010337). Work on the synthesis and characterization of the Rux complexes was supported by the NSF (H.B.G. and J.R.W.) and by the Arnold and Mabel Beckman Foundation.",
revision_no = "11",
abstract = "We have shown that Ru^(II)(bpy)_2(bpy-4-(xylyl)_x-≡-phenyl-COOH)(PF_6)_2 (abbreviated Rux, where x = 0, 1 or 2 xylyl groups; bpy = 2,2‘-bipyridine) dyes can act as sensitizers for nanocrystalline TiO_2 in functional photoelectrochemical cells under simulated solar illumination, albeit with low efficiencies. Both the short-circuit photocurrent density and the open-circuit voltage decreased as x was increased. Electron injection (10^6−10^8 s^(-1)) was slightly faster for the x = 0 dye, but both recombination (10^(-15)−10^(-13) cm^3 s^(-1)) and regeneration (10^4−10^6 s^(-1) for 10 mM I^-) were slightly faster for the x = 2 dye. We suggest that the lack of distance dependence is due to the flexible one-carboxyl attachment to the surface resulting in the Ru−TiO_2 electron-tunneling distance being very similar for x = 0, 1, and 2. For all of the Rux sensitizers, a relatively small potential was needed for generation of current in the dark, indicating that the reaction between electrons in TiO_2 and the I_3^-/I^- electrolyte solution is as favorable for the Rux sensitizers as for unmodified TiO_2 electrodes.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/938,
title ="Biological inorganic chemistry at the beginning of the 21st century",
author = "Gray, Harry B.",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "100",
number = "7",
pages = "3563-3568",
month = "April",
year = "2003",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:GRApnas03",
note = "© 2003 by the National Academy of Sciences. \n\nMany thanks to Peter Brzezinski, Angelo Di Bilio, Alex Dunn, Jenn Lee, Ed Stiefel, Akif Tezcan, and Jay Winkler for assistance with references and figures as well as helpful discussions; and to the National Science Foundation, the National Institutes of Health, and the Arnold and Mabel Beckman Foundation for research support.",
revision_no = "7",
abstract = "Advances in bioinorganic chemistry since the 1970s have been driven by three factors: rapid determination of high-resolution structures of proteins and other biomolecules, utilization of powerful spectroscopic tools for studies of both structures and dynamics, and the widespread use of macromolecular engineering to create new biologically relevant structures. Today, very large molecules can be manipulated at will, with the result that certain proteins and nucleic acids themselves have become versatile model systems for elucidating biological function.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/626,
title ="The protein-folding speed limit: Intrachain diffusion times set by electron-transfer rates in denatured Ru(NH3)(5)(His-33)-Zn-cytochrome c",
author = "Chang, I-Jy and Lee, Jennifer C.",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "100",
number = "7",
pages = "3838-3840",
month = "April",
year = "2003",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:CHApnas03",
note = "© 2003 by the National Academy of Sciences. \n\nEdited by Jack Halpern, University of Chicago, Chicago, IL, and approved January 30, 2003 (received for review November 29, 2002). Published online before print March 19, 2003. \n\nI-J.C. gratefully acknowledges financial support from the National Taiwan Normal University and the National Science Council of the Republic of China. J.C.L. thanks the Ralph M. Parsons Foundation for a graduate fellowship. This work was supported by National Science Foundation Grant MCB 9974477 and the Arnold and Mabel Beckman Foundation.",
revision_no = "8",
abstract = "The kinetics of electron transfer from the triplet-excited Zn-porphyrin to a Ru(NH3)(5)(His-33)(3+) complex have been measured in Zn-substituted ruthenium-modified cytochrome c under denaturing conditions. In the folded protein, the electron-tunneling rate constant is 7.5 x 10(5) s(-1). As the protein is denatured with guanidine hydrochloride, a faster adiabatic electron-transfer reaction appears (4.0 x 10(6) s(-1), [guanidine hydrochloride] = 5.4 M) that is limited by the rate of intrachain diffusion to bring the Zn-porphyrin and Ru complex into contact. The 250-ns contact time for formation of a 15-residue loop in denatured cytochrome c is in accord with a statistical model developed by Camacho and Thirumalai [Camacho, C. J. & Thirumalai, D. (1995) Proc. Natl. Acad. Sci. USA 92, 1277-1281] that predicts that the most probable transient loops formed in denatured proteins are comprised of 10 amino acids. Extrapolation of the cytochrome c contact time to a 10-residue loop sets the folding speed limit at approximate to10(7) s(-1).",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/76575,
title ="Structural Model for an Alkaline Form of Ferricytochrome c",
author = "Assfalg, Michael and Bertini, Ivano",
journal = "Journal of the American Chemical Society",
volume = "125",
number = "10",
pages = "2913-2922",
month = "March",
year = "2003",
doi = "10.1021/ja027180s",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170414-134611221",
note = "© 2003 American Chemical Society. \n\nReceived 5 June 2002. Published online 14 February 2003. Published in print 1 March 2003. \n\nWe thank the MIUR COFIN2001 and EU TMR Network (FMRX-CT98-0218) (I.B.), Italian CNR (Progetto Finalizzato Biotecnologie 01.00359.PF49) (P.T.), Operating Grant MT-14021 from the Canadian Institutes of Health Research and a Canada Research Chair (A.G.M.), and the National Science Foundation (H.B.G.).",
revision_no = "14",
abstract = "An ^(15)N-enriched sample of the yeast iso-1-ferricytochrome c triple variant (Lys72Ala/Lys79Ala/Cys102Thr) in an alkaline conformation was examined by NMR spectroscopy. The mutations were planned to produce a cytochrome c with a single conformer. Despite suboptimal conditions for the collection of spectra (i.e., pH ≈ 11), NMR remains a suitable investigation technique capable of taking advantage of paramagnetism. 76% of amino acids and 49% of protons were assigned successfully. The assignment was in part achieved through standard methods, in part through the identification of groups maintaining the same conformation as in the native protein at pH 7 and, for a few other residues, through a tentative analysis of internuclear distance predictions. Lys73 was assigned as the axial ligand together with His18. In this manner, 838 meaningful NOEs for 108 amino acids, 50 backbone angle constraints, and 203 pseudocontact shifts permitted the convergence of randomly generated structures to a family of conformers with a backbone RMSD of 1.5 ± 0.2 Å. Most of the native cytochrome c conformation is maintained at high pH. The NOE pattern that involves His18 clearly indicates that the proximal side of the protein, including the 20s and 40s loops, remains essentially intact. Structural differences are concentrated in the 70−80 loop, because of the replacement of Met80 by Lys73 as an axial ligand, and in the 50s helix facing that loop; as a consequence, there is increased exposure of the heme group to solvent. Based on several spectral features, we conclude that the folded polypeptide is highly fluxional.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/76580,
title ="Aerobic Oxidations Catalyzed by Chromium Corroles",
author = "Mahammed, Atif and Gray, Harry B.",
journal = "Journal of the American Chemical Society",
volume = "125",
number = "5",
pages = "1162-1163",
month = "February",
year = "2003",
doi = "10.1021/ja028216j",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170417-064908538",
note = "© 2003 American Chemical Society. \n\nReceived 20 August 2002. Published online 14 January 2003. Published in print 1 February 2003. \n\nThis research was supported by the Israel Science Foundation under Grant 368/00 (Z.G.), the ACS Petroleum Research Fund (Z.G.), and NSF (H.B.G.).",
revision_no = "9",
abstract = "Oxochromium(V) complexes of 5,10,15-tris(pentafluorophenyl)corrole and brominated derivatives oxygenate substrates (triphenylphosphine and norbornene) with concomitant production of chromium(III). Regeneration of Cr^VO by reaction of dioxygen with Cr^(III) completes an aerobic catalytic cycle, with very large solvent effects; in acetonitrile, rapid initial turnovers observed initially are shut down by formation of Cr^(IV)O, while in toluene, THF, and methanol, relatively slow reactions are further inhibited by product formation.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77847,
title ="Trapping of peptide-based surrogates in an artificially created channel of cytochrome c peroxidase",
author = "Hays, Anna-Maria A. and Gray, Harry B.",
journal = "Protein Science",
volume = "12",
number = "2",
pages = "278-287",
month = "February",
year = "2003",
doi = "10.1110/ps.0228403",
issn = "0961-8368",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170531-090242293",
note = "© 2003 The Protein Society. Published by Cold Spring Harbor Laboratory Press. \n\nRECEIVED August 14, 2002; FINAL REVISION November 14, 2002; ACCEPTED November 15, 2002. \n\nWe thank Drs. Stefan Vetter, Alycen Nigro, and Laura Hunsicker-Wang as well as Alex Dunn for help and valuable discussions. This work was supported by NIH Grants GM41049 and GM48495 (to D.B.G and H.B.G.), and NIH NRSA Postdoctoral Fellowship GM20703-03 (to A-M.A.H.). \n\nThe publication costs of this article were defrayed in part by payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 USC section 1734 solely to indicate this fact.",
revision_no = "10",
abstract = "As recently described, the deliberate removal of the proposed electron transfer pathway from cytochrome c peroxidase resulted in the formation of an extended ligand-binding channel. The engineered channel formed a template for the removed peptide segment, suggesting that synthetic surrogates might be introduced to replace the native electron transfer pathway. This approach could be united with the recent development of sensitizer-linked substrates to initiate and study electron transfer, allowing access to unresolved issues about redox mechanism of the enzyme. Here, we present the design, synthesis, and screening of a peptide library containing natural and unnatural amino acids to identify the structural determinants for binding this channel mutant. Only one peptide, (benzimidazole-propionic acid)-Gly-Ala-Ala, appeared to interact, and gave evidence for both reversible and kinetically trapped binding, suggesting multiple conformations for the channel protein. Notably, this peptide was the most analogous to the removed electron transfer sequence, supporting the use of a cavity-template strategy for design of specific sensitizer-linked substrates as replacements for the native electron transfer pathway.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/56981,
title ="Cloning, heterologous expression, and characterization of recombinant class II cytochromes c from Rhodopseudomonas palustris",
author = "McGuirl, Michele A. and Lee, Jennifer C.",
journal = "Biochimica et Biophysica Acta - General Subjects",
volume = "1619",
number = "1",
pages = "23-8",
month = "January",
year = "2003",
doi = "10.1016/S0304-4165(02)00437-3",
issn = "0304-4165",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150424-155358251",
note = "© 2002 Elsevier. \n\nReceived 16 July 2002; received in revised form 9 September 2002; accepted 19 September 2002. \n\nThe authors thank Linda Thöny-Meyer for the gift of plasmid pEC86, and A. Grant Mauk for the gift of plasmid pBPCYC1. This work was supported by NSF (MCB 9974477), NIH (GM16424, J.H.R.; GM020316-03, M.A.M.; GM07616, J.G.L), the Ralph M. Parsons Foundation (J.C.L.), and the Arnold and Mabel Beckman Foundation.",
revision_no = "10",
abstract = "The cytochrome (cyt) c′, cyt c_(556), and cyt c_2 genes from Rhodopseudomonas palustris have been cloned; recombinant cyt c′ and cyt c_(556) have been expressed, purified, and characterized. Unlike mitochondrial cyt c, these two proteins are structurally similar to cyt b_(562), in which the heme is embedded in a four-helix bundle. The hemes in both recombinant proteins form covalent thioether links to two Cys residues. UV/vis spectra of the Fe^(II) and Fe^(III) states of the recombinant cyts are identical with those of the corresponding native proteins. Equilibrium unfolding measurements in guanidine hydrochloride solutions confirm that native Fe^(II)-cyt c_(556) is more stable than the corresponding state of Fe^(III)-cyt c_(556) (ΔΔG_f°=22 kJ/mol).",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/76578,
title ="Structural Features of the Cytochrome c Molten Globule Revealed by Fluorescence Energy Transfer Kinetics",
author = "Lyubovitsky, Julia G. and Gray, Harry B.",
journal = "Journal of the American Chemical Society",
volume = "124",
number = "50",
pages = "14840-14841",
month = "December",
year = "2002",
doi = "10.1021/ja028141j",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170414-144545941",
note = "© 2002 American Chemical Society. \n\nReceived 14 August 2002. Published online 20 November 2002. Published in print 1 December 2002. \n\nThis work was supported by the NSF (MCB-9974477, DBI-9876443), an NIH training grant (J.G.L.), and the Arnold and Mabel Beckman Foundation.",
revision_no = "13",
abstract = "Nonnative states of proteins are involved in a variety of cellular processes, including translocation of proteins across membranes and formation of amyloid fibrils. Probes that report on the structural heterogeneity of a polypeptide ensemble could resolve ambiguities in the classification of these states. Employing fluorescence energy transfer kinetics, we have shown that added anions shift the equilibrium between the compact and extended polypeptide structures that are present during refolding of Saccaromyces cerevisiae iso-1 cytochrome c. Specifically, at high salt concentrations (≥700 mM), all of the polypeptides are compact with a mean C-terminal fluorophore-heme separation quite close to that in the native protein (25 Å).",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/2998,
title ="Active Carboxylic Acid-Terminated Alkanethiol Self-Assembled Monolayers on Gold Bead Electrodes for Immobilization of Cytochromes c",
author = "Tanimura, Ryutaro and Hill, Michael G.",
journal = "Electrochemical and Solid-State Letters",
volume = "5",
number = "12",
pages = "E67-E70",
month = "December",
year = "2002",
issn = "1099-0062",
url = "https://resolver.caltech.edu/CaltechAUTHORS:TANessl02",
note = "©2002 The Electrochemical Society \n\nManuscript submitted June 12, 2002; revised manuscript received August 23, 2002. Available electronically October 7, 2002. \n\nWork at Caltech was supported by NIH, NSF, and the Arnold and Mabel Beckman Foundation. E.M. acknowledges support from the Edward Mallinckrodt, Jr., Foundation. Work at Occidental College was supported by the David and Lucille Packard Foundation’s Initiative for Interdisciplinary Research. The authors thank Dojindo Molecular Technology for providing carboxylic acid-terminated alkanethiols. California Institute of Technology assisted in meeting the publication costs of this article.",
revision_no = "5",
abstract = "It is extremely difficult to immobilize cytochrome c (cyt c) on carboxylic acid-terminated alkanethiol self-assembled monolayers (HOOC-SAM) on gold bead electrodes prepared in a hydrogen flame. We found that simple pretreatment of a HOOC-SAM/gold bead electrode by potential cycling in buffer solution in the range ±300 mV prior to immobilization of the protein facilitated stable cyt c binding to HOOC-SAMs. The stability of cyt c on the HOOC-SAMs is independent of the topology of the gold surface.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/988,
title ="Structural features of cytochrome c' folding intermediates revealed by fluorescence energy-transfer kinetics",
author = "Lee, Jennifer C. and Engman, K. Cecilia",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "99",
number = "23",
pages = "14778-14782",
month = "November",
year = "2002",
doi = "10.1073/pnas.192574099",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:LEEpnas02",
note = "© 2002 by the National Academy of Sciences. \n\nContributed by Harry B. Gray, September 22, 2002. Published online before print October 29, 2002, 10.1073/pnas.192574099 \n\nThis work was supported by National Science Foundation Grants MCB-9974477 and DBI-9876443 and the Arnold and Mabel Beckman Foundation. J.C.L. acknowledges the Parsons Foundation for a graduate fellowship, and K.C.E. acknowledges the Swedish Foundation for International Cooperation in Research and Higher Education (STINT) for a fellowship. \n\nData deposition: The atomic coordinates and structure factors have been deposited in the Protein Data Bank, www.rcsb.org (PDB ID code 1MQV).",
revision_no = "9",
abstract = "We employed fluorescence energy-transfer probes to investigate the polypeptide dynamics accompanying cytochrome c' folding. Analysis of fluorescence energy-transfer kinetics from wild-type Trp-72 or Trp-32 in a crystallographically characterized (1.78 Angstrom) Q1A/F32W/W72F mutant shows that there is structural heterogeneity in denatured cytochrome c'. Even at guanidine hydrochloride concentrations well beyond the unfolding transition, a substantial fraction of the polypeptides (approximate to 50%) adopts compact conformations (tryptophan-to-heme distance, approximate to 25 Angstrom) in both pseudo-wild-type (Q1A) and mutant proteins. A burst phase (less than or equal to 5 ms) is revealed when stopped flow-triggered refolding is probed by tryptophan intensity: measurements on the Q1A protein show that approximate to 75% of the Trp-72 fluorescence (83% for Trp-32) is quenched within the mixing deadtime, suggesting that most of the polypeptides have collapsed.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77464,
title ="Transient Absorption Spectroscopy of Ruthenium and Osmium Polypyridyl Complexes Adsorbed onto Nanocrystalline TiO_2 Photoelectrodes",
author = "Kuciauskas, Darius and Monat, Jeremy E.",
journal = "Journal of Physical Chemistry B",
volume = "106",
number = "36",
pages = "9347-9358",
month = "September",
year = "2002",
doi = "10.1021/jp014589f",
issn = "1520-6106",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170515-143505122",
note = "© 2002 American Chemical Society. \n\nReceived: December 18, 2001; In Final Form: April 8, 2002; Publication Date (Web): August 17, 2002. \n\nThis work was supported by the Department of Energy, Office of Basic Energy Sciences, Grants DE-FG03-88ER13932 (D.K., N.S.L.) and DE-FG03-96ER14665 (JKM); by the NSF (H.B.G.); by the University of California Energy Institute (JKM); by the Petroleum Research Fund administered by the American Chemical Society, grant 36108-AC6 (JKM); and by the Alfred P. Sloan Foundation (JKM). We also acknowledge a generous gift in support of work on TiO_2 photoelectrochemistry to Caltech by the DuPont Company. ",
revision_no = "13",
abstract = "Transient absorption spectroscopy has been used to probe the electron injection dynamics of transition metal polypyridyl complexes adsorbed onto nanocrystalline TiO_2 photoelectrodes. Experiments were performed on photoelectrodes coated with Ru(H_2L‘)_2(CN)_2, Os(H_2L‘)_2(CN)_2, Ru(H_2L‘)_2(NCS)_2, or Os(H_2L‘)_2(NCS)_2, where H_2L‘ is 4,4‘-dicarboxylic acid-2,2‘-bipyridine, to study how the excited-state energetics and the nature of the metal center affect the injection kinetics. All of these complexes exhibited electron injection dynamics on both the femtosecond and picosecond time scales. The femtosecond components were instrument-limited (<200 fs), whereas the picosecond components ranged from 3.3 ± 0.3 ps to 14 ± 4 ps (electron injection rate constants k_2‘ = (7.1−30) × 10^(10) s^(-1)). The picosecond decay component became more rapid as the formal excited-state reduction potential of the complex became more negative. Variable excitation wavelength studies suggest that femtosecond injection is characteristic of the nonthermalized singlet metal-to-ligand charge-transfer (^1MLCT) excited state, whereas picosecond injection originates from the lowest-energy ^3MLCT excited state. On the basis of these assignments, the smaller relative amplitude of the picosecond component for the Ru sensitizers suggests that electron injection from nonthermalized excited states competes more effectively with ^1MLCT → ^3MLCT conversion for the Ru sensitizers than for the Os sensitizers.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/76801,
title ="Fluorescent Probes for Cytochrome P450 Structural Characterization and Inhibitor Screening",
author = "Dunn, Alexander R. and Hays, Anna-Maria A.",
journal = "Journal of the American Chemical Society",
volume = "124",
number = "35",
pages = "10254-10255",
month = "September",
year = "2002",
doi = "10.1021/ja0271678",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170421-083018566",
note = "© 2002 American Chemical Society. \n\nReceived June 4, 2002. Publication Date (Web): August 10, 2002. \n\nThis work was supported by the Fannie and John Hertz Foundation (A.R.D.), the National Science Foundation, and the National Institutes of Health (Metalloprotein Program Project Grant P01 GM48495; NRSA fellowship GM20703 to A.-M.A.H.).",
revision_no = "16",
abstract = "We have synthesized two luminescent probes (D-4-Ad and D-8-Ad) that target cytochrome P450cam. D-4-Ad luminescence is quenched by Förster energy transfer upon binding (K_d = 0.83 μM) but is restored when the probe is displaced from the active site by camphor. In contrast, D-8-Ad (K_d ≈ 0.02 μM) is not displaced from the enzyme, even in the presence of a large excess of camphor. The 2.2 Å resolution crystal structure of the D-8-Ad:P450cam complex reveals extensive hydrophobic contacts between the probe and the enzyme, which result from the conformational flexibility of the B‘, F, and G helices. Probes with properties similar to those of D-4-Ad potentially could be useful for screening P450 inhibitors.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77597,
title ="Electron-Transfer Reorganization Energies of Isolated Organic Molecules",
author = "Amashukeli, Xenia and Winkler, Jay R.",
journal = "Journal of Physical Chemistry A",
volume = "106",
number = "33",
pages = "7593-7598",
month = "August",
year = "2002",
doi = "10.1021/jp014148w",
issn = "1089-5639",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170519-082618407",
note = "© 2002 American Chemical Society. \n\nReceived 13 November 2001. Published online 10 April 2002. Published in print 1 August 2002. \n\nThis work was supported by NSF (CHE-0078809:\u2009 H.B.G., J.R.W.; CHE-0078457:\u2009 D.L.L.) and DOE (DE-FG03-95ER14574:\u2009 D.L.L.).",
revision_no = "10",
abstract = "He I photoelectron spectra of phenanthrene (1), 1,10-phenanthroline (2), phenazine (3), dibenzo[a,c]anthracene (4), dibenzo[a,c]phenazine (5), and dipyrido[3,2-a;2‘3‘-c]phenazine (6) have been obtained. Assignment of the π ionization states was aided by electronic structure calculations:\u2009 the first ionization state of 1, ^2B_1(π_1), is observed at 7.888 ± 0.002 eV, ^2B_2(π_1) of 2 is at 8.342 ± 0.002 eV, and ^2B_(1g)(π_1) of 3 is at 8.314 ± 0.002 eV. Spectra of 4−6 are reported for the first time:\u2009^2A_2(π_1) of 4 is at 7.376 ± 0.002 eV, and both 5 (7.983 ± 0.002 eV) and 6 (8.289 ± 0.002 eV) exhibit quasi-degenerate first and second ionization states. Quantum-mechanical reorganization energies, λ^(QM), were extracted from analyses of vibrational structure:\u2009 values are 149 ± 5 (1), 167 ± 5 (2), 68 ± 2 (3), and 92 ± 4 (4) meV. Low-frequency modes were treated semiclassically:\u2009 values of λ^(SC) are estimated to be 21 ± 1 (1), 13 ± 1 (2), 22 ± 1 (3), 66 ± 1 (4), 27 ± 9 (5), and 16 ± 1 (6) meV. Reorganization energies (λ = λ^(QM) + λ^(SC)) of isolated molecules are 170 ± 5 (1), 180 ± 5 (2), 90 ± 2 (3), and 158 ± 4 (4) meV. Density functional calculations (B3LYP/6-311G++(d,p)) give λ values that are on average 63 meV lower than experimentally derived energies.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/987,
title ="Using deeply trapped intermediates to map the cytochrome c folding landscape",
author = "Tezcan, F. Akif and Findley, William M.",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "99",
number = "13",
pages = "8626-8630",
month = "June",
year = "2002",
doi = "10.1073/pnas.132254499",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:TEZpnas02",
note = "© 2002 by the National Academy of Sciences. \n\nContributed by Harry B. Gray, April 30, 2002. \n\nThis research was supported by the National Science Foundation (MCB 9974477; DBI 9876443) and the Arnold and Mabel Beckman Foundation. \n\nData deposition: The atomic coordinates have been deposited in the Protein Data Bank, www.rcsb.org (access code 015902) (PDB ID code 1LFM).",
revision_no = "9",
abstract = "Replacement of iron with cobalt(III) selectively introduces a deep trap in the folding-energy landscape of the heme protein cytochrome c. Remarkably, neither the protein structure nor the folding thermodynamics is perturbed by this metal-ion substitution, as shown by data from spectroscopic and x-ray diffraction experiments. Through kinetics measurements, we have found parallel folding pathways involving several different misligated Co(III) species, and, as these folding intermediates persist for several hours under certain conditions, we have been able to elucidate fully their spectroscopic properties. The results, along with an analysis of the fluorescence energy-transfer kinetics during refolding, show that rapidly equilibrating populations of compact and extended polypeptide conformations are present until all molecules have reached the native structure. These measurements provide direct evidence that collapsed denatured structures are not substantially more stable than extended conformations of cytochrome c.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/76516,
title ="Mapping the Cytochrome c Folding Landscape",
author = "Lyubovitsky, Julia G. and Gray, Harry B.",
journal = "Journal of the American Chemical Society",
volume = "124",
number = "19",
pages = "5481-5485",
month = "May",
year = "2002",
doi = "10.1021/ja017399r",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170411-132345490",
note = "© 2002 American Chemical Society. \n\nReceived 26 October 2001. Published online 20 April 2002. Published in print 1 May 2002. \n\nWe thank Jason Telford, Michael Machczynski, and I-Jy Chang for assistance during the initial stages of this project. This work was supported by the NSF (MCB-9974477, DBI-9876443), an NIH training grant and NSF graduate fellowship (J.G.L.), and the Arnold and Mabel Beckman Foundation.",
revision_no = "13",
abstract = "The solution to the riddle of how a protein folds is encoded in the conformational energy landscape for the constituent polypeptide. Employing fluorescence energy transfer kinetics, we have mapped the S. cerevisiae iso-1 cytochrome c landscape by monitoring the distance between a C-terminal fluorophore and the heme during folding. Within 1 ms after denaturant dilution to native conditions, unfolded protein molecules have evolved into two distinct and rapidly equilibrating populations:\u2009 a collection of collapsed structures with an average fluorophore−heme distance (r̄) of 27 Å and a roughly equal population of extended polypeptides with r̄ > 50 Å. Molecules with the native fold appear on a time scale regulated by heme ligation events (∼300 ms, pH 7). The experimentally derived landscape for folding has a narrow central funnel with a flat upper rim on which collapsed and extended polypeptides interchange rapidly in a search for the native structure.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/2889,
title ="Anisotropic valence-->core x-ray fluorescence from a [Rh(en)3][Mn(N)(CN)5]·H2O single crystal: Experimental results and density functional calculations",
author = "Bergmann, U. and Bendix, J.",
journal = "Journal of Chemical Physics",
volume = "116",
number = "5",
pages = "2011-2015",
month = "February",
year = "2002",
issn = "0021-9606",
url = "https://resolver.caltech.edu/CaltechAUTHORS:BERjcp02",
note = "©2002 American Institute of Physics. \n\n(Received 21 June 2001; accepted 28 September 2001) \n\nThe authors thank Hal Tompkins and the beamline 10-2 staff at SSRL for assistance in making these experiments possible. This work was supported by the National Institutes of Health Grants No. GM-44380 (S.P.C.), the DOE Office of Biological and Environmental Research (S.P.C.) and the National Science Foundation Grant No. CHE-0078809 (H.B.G.). Portions of this research were carried out at the Stanford Synchrotron Radiation Laboratory, a national user facility operated by Stanford University on behalf of the U.S. Department of Energy, Office of Basic Energy Sciences.",
revision_no = "5",
abstract = "High resolution x-ray fluorescence spectra have been recorded for emission in different directions from a single crystal of the compound [Rh(en)3][Mn(N)(CN)5]·H2O. The spectra are interpreted by comparison with density functional theory (DFT) electronic structure calculations. The Kbeta[double-prime] line, which is strongly polarized along the Mn–N axis, can be viewed as an N(2s)-->Mn(1s) transition, and the angular dependence is understood within the dipole approximation. The so-called Kbeta2,5 region has numerous contributions but is dominated by Mn(4p) and C(2s)-->Mn(1s) transitions. Transition energy splittings are found in agreement with those of calculated occupied molecular orbitals to within 1 eV. Computed relative transition probabilities reproduce experimentally observed trends.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/56982,
title ="An outer-sphere hydrogen-bond network constrains copper coordination in blue proteins",
author = "Machczynski, Michael C. and Gray, Harry B.",
journal = "Journal of Inorganic Biochemistry",
volume = "88",
number = "3-4",
pages = "375-80",
month = "February",
year = "2002",
doi = "10.1016/S0162-0134(02)00364-1",
issn = "0162-0134",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150424-155358996",
note = "© 2002 Elsevier. \n\nReceived 19 June 2001; received in revised form 1 January 2002; accepted 8 February 2002. \n\nThis work was supported by the NIH (DK19038 to H.B.G.; GM16424 to J.H.R.; NIH Training Fellowship in Cellular and Molecular Biology to M.C.M.). We thank Hans Freeman and Victor Davidson for very helpful comments on this work.",
revision_no = "8",
abstract = "In azurins and other blue copper proteins with relatively low reduction potentials (E^0 [Cu^(II)/Cu^I]<400 mV vs. normal hydrogen electrode), the folded polypeptide framework constrains both copper(II) and copper(I) in such a way as to tune the reduction potentials to values that differ greatly from those for most copper complexes. Largely conserved networks of hydrogen bonds organize and lock the rest of the folded protein structure to a loop that contains three of the ligands to copper. Changes in hydrogen bonds that allow copper(I) to revert more closely to its preferred geometry [relative to the copper(II) geometry] accordingly lead to an increase in E^0. This paper reports mutations in the ligand loop of amicyanin from P. denitrificans that relax the constraints on ligation for copper(I) and significantly raise E^0 for these mutants (for example 415±4 mV) relative to that of the native amicyanin (265±4 mV). These mutations also shift the pK_a of a ligand histidine to below 5 relative to 7.0 in the wild type.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/76852,
title ="Chromium Corroles in Four Oxidation States",
author = "Meier-Callahan, Alexandre E. and Di Bilio, Angel J.",
journal = "Inorganic Chemistry",
volume = "40",
number = "26",
pages = "6788-6793",
month = "December",
year = "2001",
doi = "10.1021/ic010723z",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170424-112811010",
note = "© 2001 American Chemical Society. \n\nReceived 9 July 2001. Published online 20 November 2001. Published in print 1 December 2001. \n\nThis work was supported by the NSF (H.B.G.), the Bayer Corporation, and the Israel Science Foundation (Z.G.).",
revision_no = "13",
abstract = "We have isolated and characterized chromium complexes of 5,10,15-tris(pentafluorophenyl)corrole [(tpfc)H_3] (1) in four oxidation states:\u2009 [(tpfc•)CrO][SbCl_6] (6); [(tpfc)CrO] (2); [(tpfc)CrO][Cp_2Co] (4); and [(tpfc)Cr(py)_2] (3). Complex 6 was prepared both by electrochemical and chemical oxidation of 2; its formulation as a Cr^VO ligand−radical species is based on UV−visible absorption as well as EPR measurements. Cobaltocene reduction of 2 gave 4; it was identified as a diamagnetic d^2 Cr^(IV)O complex from its sharp ^1H NMR spectrum. Reaction of 2 with triphenylphosphine yielded a chromium(III) corrole, [(tpfc)Cr(OPPh_3)_2] (5). Owing to its air sensitivity, 5 could not be isolated in the absence of excess OPPh_3. The structure of the Cr^(III) bis-pyridine complex (3) was determined by X-ray crystallography (Cr−N distances:\u2009 1.926−1.952 Å, pyrrole; 2.109, 2.129 Å, pyridine).",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/57196,
title ="Axial Ligand Modulation of the Electronic Structures of Binuclear Copper Sites:\u2009 Analysis of Paramagnetic ^1H NMR Spectra of Met160Gln Cu_A",
author = "Fernández, Claudio O. and Cricco, Julia A.",
journal = "Journal of the American Chemical Society",
volume = "123",
number = "47",
pages = "11678-11685",
month = "November",
year = "2001",
doi = "10.1021/ja0162515",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150504-115753848",
note = "© 2001 American Chemical Society. \n\nReceived May 22, 2001. Publication Date (Web): October 31, 2001. \n\nThis work was supported by NIH Grants R01-DK19038 to H.B.G. and R01-GM16424 to J.H.R. and FIRCA-NIH Grant R03-TW000985-01 to H.B.G. and A.J.V. C.O.F. and A.J.V. are staff members at CONICET. J.A.C. is recipient of a fellowship from CONICET. We thank Ramiro Rodríguez for help with protein purification and Sergio Dalosto for helpful discussions. C.O.F. and A.J.V. thank CERM (University of Florence) for allowing C.O.F. to record the 800 MHz spectra and for the hospitality offered to C.O.F. \n\nAccession Codes: \nPDB: 2cua\nPDB: file+2cua\nPDB: file+1ar1",
revision_no = "9",
abstract = "Cu_A is an electron-transfer copper center present in heme-copper oxidases and N_2O reductases. The center is a binuclear unit, with two cysteine ligands bridging the metal ions and two terminal histidine residues. A Met residue and a peptide carbonyl group are located on opposite sides of the Cu2S2 plane; these weaker ligands are fully conserved in all known Cu_A sites. The Met160Gln mutant of the soluble subunit II of Thermus thermophilus ba_3 oxidase has been studied by NMR spectroscopy. In its oxidized form, the binuclear copper is a fully delocalized mixed-valence pair, as are all natural Cu_A centers. The faster nuclear relaxation in this mutant suggests that a low-lying excited state has shifted to higher energies compared to that of the wild-type protein. The introduction of the Gln residue alters the coordination mode of His114 but does not affect His157, thereby confirming the proposal that the axial ligand-to-copper distances influence the copper−His interactions (Robinson, H.; Ang, M. C.; Gao, Y. G.; Hay, M. T.; Lu, Y.; Wang, A. H. Biochemistry 1999, 38, 5677). Changes in the hyperfine coupling constants of the Cys β-CH_2 groups are attributed to minor geometrical changes that affect the Cu−S−C_β−H_β dihedral angles. These changes, in addition, shift the thermally accessible excited states, thus influencing the spectral position of the Cys β-CH_2 resonances. The Cu−Cys bonds are not substantially altered by the Cu−Gln160 interaction, in contrast to the situation found in the evolutionarily related blue copper proteins. It is possible that regulatory subunits in the mitochondrial oxidases fix the relative positions of thermally accessible Cu_A excited states by tuning axial ligand interactions.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77466,
title ="Electron Tunneling in Single Crystals of Pseudomonas aeruginosa Azurins",
author = "Crane, Brian R. and Di Bilio, Angel J.",
journal = "Journal of the American Chemical Society",
volume = "123",
number = "47",
pages = "11623-11631",
month = "November",
year = "2001",
doi = "10.1021/ja0115870",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170515-150316333",
note = "© 2001 American Chemical Society. \n\nReceived 28 June 2001. Published online 1 November 2001. Published in print 1 November 2001. \n\nWe thank Mike Machczynski for experimental assistance, Doug Rees and Akif Tezcan for helpful discussions, and SSRL for access to data collection facilities. This research was supported by NIH (DK19038), the Helen Hay Whitney Foundation (fellowship to B.R.C.), and the Arnold and Mabel Beckman Foundation.",
revision_no = "12",
abstract = "Rates of reduction of Os(III), Ru(III), and Re(I)^* by Cu(I) in His83-modified Pseudomonas aeruginosa azurins (M−Cu distance ∼17 Å) have been measured in single crystals, where protein conformation and surface solvation are precisely defined by high-resolution X-ray structure determinations:\u2009 1.7(8) × 10^6 s^(-1) (298 K), 1.8(8) × 10^6 s^(-1) (140 K), [Ru(bpy)_2(im)^(3+)-]; 3.0(15) × 10^6 s^(-1) (298 K), [Ru(tpy)(bpy)^(3+)-]; 3.0(15) × 10^6 s^(-1) (298 K), [Ru(tpy)(phen)^(3+)-]; 9.0(50) × 10^2 s^(-1) (298 K), [Os(bpy)2(im)^(3+)-]; 4.4(20) × 10^6 s^(-1) (298 K), [Re(CO)_3(phen)^(+*)] (bpy = 2,2‘-bipyridine; im = imidazole; tpy = 2,2‘:6‘,2‘\u2009‘-terpyridine; phen = 1,10-phenanthroline). The time constants for electron tunneling in crystals are roughly the same as those measured in solution, indicating very similar protein structures in the two states. High-resolution structures of the oxidized (1.5 Å) and reduced (1.4 Å) states of Ru(II)(tpy)(phen)(His83)Az establish that very small changes in copper coordination accompany reduction but reveal a shorter axial interaction between copper and the Gly45 peptide carbonyl oxygen [2.6 Å for Cu(II)] than had been recognized previously. Although Ru(bpy)_2(im)(His83)Az is less solvated in the crystal, the reorganization energy for Cu(I) → Ru(III) electron transfer falls in the range (0.6−0.8 eV) determined experimentally for the reaction in solution. Our work suggests that outer-sphere protein reorganization is the dominant activation component required for electron tunneling.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/986,
title ="Probing the open state of cytochrome P450cam with ruthenium-linker substrates",
author = "Dunn, Alexander R. and Dmochowski, Ivan J.",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "98",
number = "22",
pages = "12420-12425",
month = "October",
year = "2001",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:DUNpnas01",
note = "© 2001 by the National Academy of Sciences. \n\nEdited by Stephen J. Benkovic, Pennsylvania State University, University Park, PA, and approved August 15, 2001 (received for review June 12, 2001). Published online before print October 16, 2001, 10.1073/pnas.221297998 \n\nWe thank Stanford Synchrotron Research Laboratory for access to data collection facilities and the staff of beamlines 9-1 and 9-2 for their assistance with data collection. This work was supported by the Fannie and John Hertz Foundation (to A.R.D.), the Helen Hay Whitney Foundation (to B.R.C.), the National Institutes of Health predoctoral program (to I.J.D.), the National Science Foundation, and the National Institutes of Health. \n\nThe publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. §1734 solely to indicate this fact.",
revision_no = "7",
abstract = "Cytochromes P450 play key roles in drug metabolism and disease by oxidizing a wide variety of natural and xenobiotic compounds. High-resolution crystal structures of P450cam bound to ruthenium sensitizer-linked substrates reveal an open conformation of the enzyme that allows substrates to access the active center via a 22-Angstrom deep channel. Interactions of alkyl and fluorinated biphenyl linkers with the channel demonstrate the importance of exploiting protein dynamics for specific inhibitor design. Large changes in peripheral enzyme structure (F and G helices) couple to conformational changes in active center residues (I helix) implicated in proton pumping and dioxygen activation. Common conformational states among P450cam and homologous enzymes indicate that static and dynamic variability in the F/G helix region allows the 54 human P450s to oxidize thousands of substrates.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/983,
title ="Cytochrome c' folding triggered by electron transfer: Fast and slow formation of four-helix bundles",
author = "Lee, Jennifer C. and Gray, Harry B.",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "98",
number = "14",
pages = "7760-7764",
month = "July",
year = "2001",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:LEEpnas01",
note = "© 2001 by the National Academy of Sciences. \n\nContributed by Harry B. Gray, May 11, 2001. \n\nWe thank Michael Cusanovich and Terry Meyer (University of Arizona) for assistance with protein isolation and purification, Brian Crane for help with protein structure modeling, and Akif Tezcan for discussions. J.C.L. thanks the Ralph M. Parsons Foundation for a graduate fellowship. This work was supported by National Science Foundation Grant MCB-9974477 and by the Arnold and Mabel Beckman Foundation. \n\nThe publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. §1734 solely to indicate this fact.",
revision_no = "8",
abstract = "Reduced (Fe-II) Rhodopseudomonas palustris cytochrome c' (Cyt c') is more stable toward unfolding ([GuHCl](1/2) = 2.9(1) M) than the oxidized (Fe-III protein ([GuHCl](1/2) = 1.9(1) M). The difference in folding free energies (Delta DeltaG(f)degrees = 70 meV) is less than half of the difference in reduction potentials of the folded protein (100 mV vs. NHE) and a free heme in aqueous solution (approximate to -150 mV). The spectroscopic features of unfolded Fe-II-Cyt c' indicate a low-spin heme that is axially coordinated to methionine sulfur (Met-15 or Met-25). Time-resolved absorption measurements after CO photodissociation from unfolded Fe-II(CO)-Cyt c' confirm that methionine can bind to the ferroheme on the microsecond time scale [k(obs) = 5(2) x 10(4) s(-1)]. Protein folding was initiated by photoreduction (two-photon laser excitation of NADH) of unfolded Fe-III-Cyt c' ([GuHCl] = 2.02-2.54 M). Folding kinetics monitored by heme absorption span a wide time range and are highly heterogeneous; there are fast-folding (approximate to 10(3) s(-1)), intermediate-folding (10(2)-10(1) s(-1)), and slow-folding (10(-1) s(-1)) populations, with the last two likely containing methionine-ligated (Met-15 or Met-25) ferrohemes. Kinetics after photoreduction of unfolded Fe-III-Cyt c' in the presence of CO are attributable to CO binding [1.4(6) x 10(3) s(-1)] and Fe-II(CO)-Cyt c' folding [2.8(9) s(-1)] processes; stopped-flow triggered folding of Fe-III-Cyt c' (which does not contain a protein-derived sixth ligand) is adequately described by a single kinetics phase with an estimated folding time constant of approximate to 4 ms [DeltaG(f)degrees = -33(3) kJ mol(-1)] at zero denaturant.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77928,
title ="High-Valent Manganese Corroles and the First Perhalogenated Metallocorrole Catalyst",
author = "Golubkov, Galina and Bendix, Jesper",
journal = "Angewandte Chemie International Edition in English",
volume = "40",
number = "11",
pages = "2132-2134",
month = "June",
year = "2001",
doi = "10.1002/1521-3773(20010601)40:11<2132::AID-ANIE2132>3.0.CO;2-5",
issn = "0570-0833",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170602-151432131",
note = "© 2001 WILEY-VCH Verlag GmbH, Weinheim, Fed. Rep. of Germany. \n\nIssue online: 28 May 2001. Version of Record online: 28 May 2001. Manuscript Received: 17 Jan 2001. \n\nThis research (No. 368/00) was supported by the Israel Science Foundation (Z.G.), the US National Science Foundation (H.B.G.), and the Fund for the Promotion of Research at the Technion (Z.G.).",
revision_no = "9",
abstract = "On pyrrole! The pyrrole-based corrole ligands can offer an alternative to porphyrin systems. The manganese corroles 1–4 are readily synthesized, undergo metal- not ligand-based redox chemistry, and 4 in particular shows impressive catalytic activity in the oxygenation of styrene with iodosylbenzene.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/940,
title ="Electron tunneling in protein crystals",
author = "Tezcan, F. Akif and Crane, Brian R.",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "98",
number = "9",
pages = "5002-5006",
month = "April",
year = "2001",
doi = "10.1073/pnas.081072898",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:TEZpnas01",
note = "© 2001 by the National Academy of Sciences. \n\nContributed by Harry B. Gray, February 13, 2001. \n\nWe thank D. C. Rees and the Stanford Synchrotron Research Laboratory for access to data collection facilities, and A. M. Bilwes for technical assistance and helpful discussions. B.R.C. acknowledges the Helen Hay Whitney Foundation for a postdoctoral fellowship. This work was supported by the National Science Foundation and the Arnold and Mabel Beckman Foundation. \n\nThe publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. §1734 solely to indicate this fact.",
revision_no = "9",
abstract = "The current understanding of electron tunneling through proteins has come from work on systems where donors and accepters are held at fixed distances and orientations. The factors that control electron flow between proteins are less well understood, owing to uncertainties in the relative orientations and structures of the reactants during the very short time that tunneling occurs. As we report here, the way around such structural ambiguity is to examine oxidation-reduction reactions in protein crystals. Accordingly, we have measured and analyzed the kinetics of electron transfer between native and Zn-substituted tuna cytochrome c (cyt c) molecules in crystals of known structure. Electron transfer rates [(320 s(-1) for *Zn-cyt c --> Fe(III)-cyt c; 2000 s(-1) for Fe(II)-cyt c --> Zn-cyt c(+))] over a Zn-Fe distance of 24.1 Angstrom closely match those for intraprotein electron tunneling over similar donor-acceptor separations. Our results indicate that van der Waals interactions and water-mediated hydrogen bonds are effective coupling elements for tunneling across a protein-protein interface.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/57058,
title ="Properties of Photogenerated Tryptophan and Tyrosyl Radicals in Structurally Characterized Proteins Containing Rhenium(I) Tricarbonyl Diimines",
author = "Di Bilio, Angel J. and Crane, Brian R.",
journal = "Journal of the American Chemical Society",
volume = "123",
number = "13",
pages = "3181-3182",
month = "April",
year = "2001",
doi = "10.1021/ja0043183",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150428-143033571",
note = "© 2001 American Chemical Society.\n\nReceived December 22, 2000.\n\nDedicated to the memory of Jerry Babcock (1946- 2000). Jerry was an enthusiastic colleague and dear friend who helped us in many different ways during the course of this work. He was a master teacher as well as a brilliant scholar, and we will forever be indebted to him for his guidance. Supported by NIH (DK19038 to H.B.G.; GM16424 to J.H.R.).",
revision_no = "16",
abstract = "Aromatic amino acid radicals are key intermediates in nucleic acid biosynthesis, DNA repair, dioxygen reduction by cytochrome oxidase, water oxidation by PSII, as well as other biological procesess. In our work on electron tunneling in proteins, we have developed laser flash/quench methods that potentially could facilitate the study of such highly reactive radicals. To test our methods, we are investigating two structurally characterized proteins, [Re(CO)_3(L)(H83)]^+AzM^(2+) and [Re(CO)_3(L)(H107)]^+AzM^(2+) (L ) 1,10-phenanthroline (phen) or 4,7-Me_2phen; Az ) Pseudomonas aeruginosa azurin; M ) Cu or Zn). Of special interest is that calculations and experiments on the H107 protein show that Cu^+ oxidation via electron transfer (ET) through an intervening tyrosine (Cu^+ → Y108^(./) → Re(2+)) is over 2 orders of magnitude faster than optimized (Cu^+ → Re^(2+)) electron tunneling.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/75672,
title ="Phototriggered Ru(II)−Dimethylsulfoxide Linkage Isomerization in Crystals and Films",
author = "Rack, Jeffrey J. and Winkler, Jay R.",
journal = "Journal of the American Chemical Society",
volume = "123",
number = "10",
pages = "2432-2433",
month = "March",
year = "2001",
doi = "10.1021/ja000179d",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170404-083716205",
note = "© 2001 American Chemical Society. \n\nReceived 18 January 2000. Published online 15 February 2001. Published in print 1 March 2001. \n\nWe thank Will Wehbi, Larry Henling, Mike Day, and Brian Crane for experimental assistance and helpful discussions. This work was supported by ARO (DAAH04−95−1−0125), NSF, and NIST (ATP) Award 70NANB5H1031.",
revision_no = "13",
abstract = "Photochromic materials are of interest because of their potential applications in optical information storage devices. Measurements on photochromic sodium nitroprusside (Na_2[Fe(CN)_5(NO)]) indicate that two metastable states are formed by irradiations of the crystalline solid:\u2009 the first is an isonitrosyl (O-bonded NO); the second is an η^2-NO (side-on) complex. Phototriggered linkage isomerizations also occur in dimethylsulfoxide (dmso) complexes:\u2009notably, both photochemical Ru−S → Ru−O and thermal Ru−O → Ru−S reactions are observed in dmso solutions of [Ru(bpy)_2(dmso)_2]^(2+) (bpy = 2,2‘-bipyridine); and, as reported here, we find photochromism attributable to Ru−S → Ru−O rearrangement upon visible excitation of [Ru(tpy)(bpy)(dmso)]^(2+) (tpy = 2,2‘:6‘,2‘\u2009‘-terpyridine) in single crystals and films as well as in solution.",
}
@book_section {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/85724,
title ="Electron Transfer in Metalloproteins",
author = "Gray, Harry B. and Winkler, Jay R.",
pages = "2-23",
month = "February",
year = "2001",
doi = "10.1002/9783527618248.ch33",
isbn = "9783527299126",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180410-103754665",
note = "© 2001 Wiley-VCH Verlag GmbH. \n\nPublished Print: 22 February 2001.",
revision_no = "9",
abstract = "[no abstract]",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/99036,
title ="Bo G. Malmström (1927–2000)",
author = "Gray, Harry B.",
journal = "Journal of Biological Inorganic Chemistry",
volume = "6",
number = "2",
pages = "119",
month = "February",
year = "2001",
doi = "10.1007/s007750100206",
issn = "0949-8257",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20191002-155926072",
note = "© 2001 SBIC. \n\nFirst Online: 25 January 2001.\n",
revision_no = "11",
abstract = "We lost one of the giants of biological inorganic chemistry on 9 February 2000 [Trends Biochem. Sci. 2000, 25, 351- 352]. His name no longer appears on the list of SBIC Honorary Members (p A2). Bo enthusiastically supported the Founding Editor in the early days of JBIC. He offered encouragement as well as sage advice (and manuscripts!) as the journal grew in stature. He will long be remembered for his seminal work on copper proteins and for many other scholarly contributions to our field.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/75156,
title ="Electron Transfer Dynamics in Nanocrystalline Titanium Dioxide Solar Cells Sensitized with Ruthenium or Osmium Polypyridyl Complexes",
author = "Kuciauskas, Darius and Freund, Michael S.",
journal = "Journal of Physical Chemistry B",
volume = "105",
number = "2",
pages = "392-403",
month = "January",
year = "2001",
doi = "10.1021/jp002545l",
issn = "1520-6106",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170315-151836987",
note = "© 2001 American Chemical Society. \n\nReceived: July 18, 2000; In Final Form: September 20, 2000. Publication Date (Web): December 19, 2000. \n\nWe acknowledge Dr. George Coia of Caltech for useful discussions. This work was supported by the Department of Energy, Office of Basic Energy Sciences (D.K., M.S.F., N.S.L.), and by the NSF (H.B.G., J.R.W.). We also acknowledge a generous gift in support of work on TiO2 photoelectrochemistry to Caltech by the DuPont Company. ",
revision_no = "16",
abstract = "The electron transfer dynamics in solar cells that utilize sensitized nanocrystalline titanium dioxide photoelectrodes and the iodide/triiodide redox couple have been studied on a nanosecond time scale. The ruthenium and osmium bipyridyl complexes Ru(H_2L‘)_2(CN)_2, Os(H_2L‘)_2(CN)_2, Ru(H_2L‘)_2(NCS)_2, and Os(H_2L‘)_2(NCS)_2, where H_2L‘ is 4,4‘-dicarboxylic acid 2,2‘-bipyridine, inject electrons into the semiconductor with a rate constant >10^8 s^(-1). The effects of excitation intensity, temperature, and applied potential on the recombination reaction were analyzed using a second-order kinetics model. The rates of charge recombination decrease with increasing driving force to the oxidized sensitizer, indicating that charge recombination occurs in the Marcus inverted region. The electronic coupling factors between the oxidized sensitizer and the injected electrons in TiO_2 and the reorganization energies for the recombination reaction vary significantly for the different metal complexes. The charge recombination rates are well described by semiclassical electron transfer theory with reorganization energies of 0.55−1.18 eV. Solar cells sensitized with Ru(H_2L‘)_2(CN)_2, Os(H_2L‘)_2(CN)_2, and Ru(H_2L‘)_2(NCS)_2 have favorable photoelectrochemical characteristics, and iodide is oxidized efficiently. In contrast, iodide oxidation limits the efficiency of cells based on sensitization of TiO_2 with Os(H_2L‘)_2(NCS)_2. The observation that charge recombination occurs in the Marcus inverted region has important implications for the design of molecular sensitizers in nanocrystalline solar cells operated under our experimental conditions.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/76938,
title ="Dynamic Ionic Strength Effects in Fast Bimolecular Electron Transfer between a Redox Metalloprotein of High Electrostatic Charge and an Inorganic Reaction Partner",
author = "Jensen, Thomas J. and Gray, Harry B.",
journal = "Journal of Physical Chemistry B",
volume = "104",
number = "48",
pages = "11556-11562",
month = "December",
year = "2000",
doi = "10.1021/jp001624u",
issn = "1520-6106",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170426-082835811",
note = "© 2000 American Chemical Society. \n\nReceived: April 27, 2000; In Final Form: September 28, 2000.\nPublication Date (Web): November 10, 2000. \n\nWe thank D. M. Kurtz, Jr., and M. K. Eidsness for protein samples and helpful discussions, and I. J. Dmochowski for the p-MDMA sample. T.J.J. thanks A. Tezcan for assistance with the laser spectroscopic measurements. This work was supported by the Technical University of Denmark, the Danish Technical Science Research Council, the National Institutes of Health (DK19038, Beckman Institute), and the Russian Foundation for Basic Research (A. N. Frumkin Institute).",
revision_no = "9",
abstract = "The ionic strength dependence of the bimolecular electron transfer (ET) reaction between Clostridium pasteurianum rubredoxin(III) and photochemically generated [Ru(bpy)_3]^+ has been investigated. The reaction is fast and close to the diffusion-controlled limit. Dynamic ionic strength effects on all kinetics parameters (work terms, driving force, and reorganization free energy) have been incorporated in the data analysis; the effects on the intermolecular work terms are large and dominate in the driving force region close to the activationless limit. The variation in ET rate constant over the 0.005−2.0 M ionic strength range is quantitatively consistent with the high negative charge (−9e where e is the unit electric charge) and size (crystallographic radius ≈ 12 Å) of rubredoxin(III). If low ionic strength (0.005−0.01 M) data are omitted, the variation in rates suggests a somewhat smaller charge on the protein (−4e to −5e).",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/57100,
title ="Resonance Raman Spectroscopy of Met121Glu Azurin",
author = "Webb, M. Adam and Kiser, Cynthia N.",
journal = "Journal of Physical Chemistry B",
volume = "104",
number = "46",
pages = "10915-10920",
month = "November",
year = "2000",
doi = "10.1021/jp000832j",
issn = "1520-6106",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150429-154244398",
note = "© 2000 American Chemical Society.\n\nReceived: March 2, 2000; In Final Form: September 11, 2000.\n\nWork at the University of Alberta was supported by NSERC; work at Caltech was supported by NIH DK19038.",
revision_no = "11",
abstract = "The resonance Raman spectra for Pseudomonas aeruginosa Met121Glu azurin have been measured at wavelengths throughout the 600-nm absorption band at low and high pH. The spectra of the mutant at pH 3.5 and 7.0 are identical. Analysis of the 600-nm absorption band and resulting resonance Raman excitation profiles under both pH conditions indicates that the excited-state distortions in this mutant are smaller than those in the native protein.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77949,
title ="Structural, Electrochemical, and Photophysical Properties of Gallium(III) 5,10,15-Tris(pentafluorophenyl)corrole",
author = "Bendix, Jesper and Dmochowski, Ivan J.",
journal = "Angewandte Chemie International Edition",
volume = "39",
number = "22",
pages = "4048-4051",
month = "November",
year = "2000",
doi = "10.1002/1521-3773(20001117)39:22<4048::AID-ANIE4048>3.0.CO;2-7",
issn = "1433-7851",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170605-154908814",
note = "© 2000 Wiley-VCH Verlag GmbH, Weinheim, Fed. Rep. of Germany. \n\nIssue online: 14 November 2000; Version of record online: 14 November 2000; Manuscript Received: 26 June 2000. \n\nWe acknowledge support of this research from the Fund for the Promotion of Research at the Technion (Z.G.), the National Science Foundation (H.B.G.), and the Danish Natural Science Research Council for financial support under grant No.\u20059800549 (J.B.). We also thank Dr.\u2005H. Weihe (University of Copenhagen) for access to computing facilities, and L.\u2005M. Henling (Beckman Institute) for assistance with the crystal structure determination.",
revision_no = "10",
abstract = "High quantum yields are found for the prototype metallocorrole 1, which is readily prepared from GaCl_3 and tris(pentafluorophenyl)corrole. The crystallographic and electronic structures of 1 are reported as well as the simple generation of its π-cation radical complex by chemical oxidation and the characteristic spectroscopic features of this ion.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/27937,
title ="High-field (high-frequency) EPR spectroscopy and structural characterization of a novel manganese(III) corrole",
author = "Bendix, Jesper and Gray, Harry B.",
journal = "Chemical Communications",
volume = "2000",
number = "19",
pages = "1957-1958",
month = "September",
year = "2000",
issn = "1359-7345",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20111123-083709397",
note = "© 2000 The Royal Society of Chemistry. Received 02 Aug 2000, Accepted 30 Aug 2000. First published on the web 21 Sep 2000. We thank Dr M. W. Day (Beckman Institute) for assistance with the crystal structure determination and Ms S. Mossin (University of Copenhagen) and Dr A.-L. Barra (CNRS, Grenoble) for recording the HF-EPR spectra. This research was supported by the Fund for the Promotion of Research at the Technion (Z. G.), the National Science Foundation (H. B. G.), and grant # 9800549 from the Danish Natural Science Research Council (J. B.). ",
revision_no = "12",
abstract = "The X-ray structure, magnetic susceptibility, and high-field (high-frequency) EPR spectrum of manganese 5,10,15-tris(pentafluorophenyl) corrole unambiguously establish that the complex contains an isolated, slightly rhombic, manganese(III) center.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/78896,
title ="Enantiomeric discrimination of Ru-substrates by cytochrome P450_(cam)",
author = "Dmochowski, Ivan J. and Winkler, Jay R.",
journal = "Journal of Inorganic Biochemistry",
volume = "81",
number = "3",
pages = "221-228",
month = "August",
year = "2000",
doi = "10.1016/S0162-0134(00)00111-2",
issn = "0162-0134",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170710-131410978",
note = "© 2000 Elsevier Science S.A. \n\nReceived 7 February 2000, Revised 6 June 2000, Accepted 12 June 2000, Available online 21 September 2000. \n\nWe thank J.J. Wilker for experimental work, J.H. Dawson, B.R. Crane, E.D.A. Stemp, and A.G. Lappin for helpful discussions, and S.G. Sligar for providing a P450_(cam) vector. I.J.D. is an NIH predoctoral trainee (GM08346). This work was supported by the NIH Metalloprotein Program Project Grant (P01 GM48495) and the National Science Foundation (CHE9807150).",
revision_no = "11",
abstract = "Molecules with photosensitizers attached to substrates (Wilker et al., Angew. Chem. Int. Ed. 38 (1999) 90–92) or cofactors (Hamachi et al., J. Am. Chem. Soc. 121 (1999) 5500–5506) can rapidly deliver redox equivalents to buried active sites. The structure of cytochrome P450_(cam) (P450) co-crystallized with a prototypal sensitizer-substrate, [Ru-C_9-Ad]Cl_2, has been determined (Dmochowski et al., Proc. Natl. Acad. Sci. USA 96 (1999) 12987–12990); and, in separate UV–vis absorption and time-resolved luminescence experiments, the binding of the Λ and Δ enantiomers of Ru-C_9-Ad to P450 has been measured. The results, K_D(Δ/Λ)∼2, indicate that the bipyridyl ligands of the Λ isomer interact more favorably with hydrophobic residues at the entrance to the substrate channel. We conclude that enantiospecific interactions may be exploited in the design of enzyme-metallosubstrate conjugates.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/75270,
title ="Electron Tunneling through Water: Oxidative Quenching of Electronically Excited Ru(tpy)_2^(2+)(tpy = 2,2‘:6,2‘ ‘-terpyridine) by Ferric Ions in Aqueous Glasses at 77 K",
author = "Ponce, Adrian and Gray, Harry B.",
journal = "Journal of the American Chemical Society",
volume = "122",
number = "34",
pages = "8187-8191",
month = "August",
year = "2000",
doi = "10.1021/ja000017h",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170321-101627546",
note = "© 2000 American Chemical Society. \n\nReceived January 3, 2000. Publication Date (Web): August 8, 2000. \n\nWe thank D. N. Beratan, R. J. Cave, N. S. Lewis, R. A. Marcus, J. R. Miller, and M. D. Newton for helpful discussions. This research was supported by NSF Grant CHE9610164 and the Arnold and Mabel Beckman Foundation.",
revision_no = "15",
abstract = "The luminescence lifetime of Ru(tpy)_2^(2+) (tpy = 2,2‘:6,2‘\u2009‘-terpyridine) is 8.0 μs in H_2SO_4/H_2O and HSO_3F/H_2O glasses (25% v/v) at 77 K, and 10.2 μs in D_2SO_4/D_2O (25% v/v). Addition of moderate concentrations of the powerfully oxidizing Fe(OH_2)_6^(3+) ion to the glasses leads to accelerated and highly nonexponential *Ru(tpy)_2^(2+) decay kinetics. The quenching is attributed to electron transfer from *Ru(tpy)_2^(2+) to randomly dispersed Fe(OH_2)_6^(3+) complexes. The luminescence decay kinetics and quantum yields in the three aqueous glasses indicate that the electron-transfer rate constants decrease from ∼10^(13) s^(-1) at van der Waals contact with an exponential distance decay constant of 1.68 ± 0.07 Å^(-1).",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/75140,
title ="Stabilization of High-Valent Metals by Corroles: Oxo[tris(pentafluorophenyl)corrolato]chromium(V)",
author = "Meier-Callahan, Alexandre E. and Gray, Harry B.",
journal = "Inorganic Chemistry",
volume = "39",
number = "16",
pages = "3605-3607",
month = "August",
year = "2000",
doi = "10.1021/ic000180d",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170315-100316955",
note = "© 2000 American Chemical Society. \n\nReceived February 18, 2000; Publication Date (Web): July 21, 2000. \n\nWe thank Dr. M. Day for assistance with the crystal structure determination. This work was supported by the Bayer Corp. the NSF, and the Arnold and Mabel Beckman Foundation.",
revision_no = "13",
abstract = "The aerobic reaction of Cr(CO)_6 with tris(pentafluorophenyl)corrole (H_3(TpFPC)) in toluene gives the dark red oxochromium(V) compound (TpFPC)Cr(O), which has been characterized by X-ray crystallography, electrochemistry, and EPR spectroscopy. Short Cr−N (1.927−1.943 Å) bonds as well as relatively large ^(14)N and small ^(53)Cr coupling constants suggest that σ(N → Cr) donation is responsible for the unusual stability of chromium(V) in this complex. The Cr^(V/IV) reduction potential (0.11 V vs Ag/AgCl) is 0.65 V below that of oxo(tetramesitylporphinato)chromium(V).",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/77948,
title ="Bo G. Malmström (1927–2000)",
author = "Gray, Harry B.",
journal = "Trends in Biochemical Sciences",
volume = "25",
number = "8",
pages = "351-352",
month = "August",
year = "2000",
doi = "10.1016/S0968-0004(00)01618-2",
issn = "0968-0004",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170605-154429261",
note = "© 2000 Elsevier Science Ltd. \n\nAvailable online 2 August 2000.",
revision_no = "9",
abstract = "We lost a great scientist and a dear friend on 9 February this year. Bo Malmström (see Photograph) was a very special person: he was passionate about everything he did, and he did many things. I can only cover a few of his activities in this tribute. Note that Bo himself wrote a much more thorough account in his article ‘A Life with the Metals of Life’ – it is a good read.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/79923,
title ="Lowest Electronic Excited States of Platinum(II) Diimine Complexes",
author = "Connick, William B. and Miskowski, Vincent M.",
journal = "Inorganic Chemistry",
volume = "39",
number = "12",
pages = "2585-2592",
month = "June",
year = "2000",
doi = "10.1021/ic991369w",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170808-095512740",
note = "© 2000 American Chemical Society. \n\nReceived November 29, 1999. Publication Date (Web): May 19, 2000. \n\nWe thank J. A. Bailey, A. J. DiBilio, and J. R. Winkler for many helpful discussions and expert technical assistance. This work was supported by NSF.",
revision_no = "9",
abstract = "Absorption and emission spectra of Pt(diimine)L_2 complexes (diimine = 2,2‘-bipyridine (bpy) or 4,4‘-dimethyl-2,2‘-bipyridine (dmbpy); L = pyrazolate (pz-), 3,5-dimethylpyrazolate (dmpz-), or 3,4,5-trimethylpyrazolate (tmpz-)) have been measured. Solvent-sensitive absorption bands (370−440 nm) are attributed to spin-allowed metal-to-ligand charge-transfer (^1MLCT) transitions. As solids and in 77 K glassy solution, Pt(bpy)(pz)_2 and Pt(dmbpy)(pz)_2 exhibit highly structured emission systems (λ_(max)≈ 494 nm) similar to those of the diprotonated forms of these complexes. The highly structured bands (spacings 1000−1400 cm^(-1)) indicate that the transition originates in a diimine-centered ^3(π→π*) (^3LL) excited state. The intense solid-state and 77 K glassy solution emissions from ^3MLCT[d(Pt)→π*(bpy)] excited states of complexes with dmpz- and tmpz- ligands occur at longer wavelengths (λ_(max) = 500−610 nm), with much broader vibronic structure. These findings are consistent with increasing electron donation of the pyrazolate ligands, leading to a distinct crossover from a lowest ^3LL to a ^3MLCT excited state.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/76809,
title ="Bond-Mediated Electron Tunneling in Ruthenium-Modified High-Potential Iron−Sulfur Protein",
author = "Babini, Elena and Bertini, Ivano",
journal = "Journal of the American Chemical Society",
volume = "122",
number = "18",
pages = "4532-4533",
month = "May",
year = "2000",
doi = "10.1021/ja994472t",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170421-092308907",
note = "© 2000 American Chemical Society. \n\nReceived December 22, 1999. Publication Date (Web): April 22, 2000. \n\nWe thank Brian Crane for helpful discussions. This research was supported by NIH (DK19038 to H.B.G.; GM48043 to D.N.B.), the Howard Hughes Medical Institute (summer undergraduate research fellowship to X.Z.), and CAPES-Brazil (graduate fellowship to G.L.C.M.).",
revision_no = "15",
abstract = "High-potential iron−sulfur proteins (HiPIPs) are found in photosynthetic purple nonsulfur bacteria. The three-dimensional structure of Chromatium vinosum HiPIP features two short segments of α-helix, three strands of antiparallel β-pleated sheet, and a small helix near the N-terminus. The cubane [Fe_4S_4] cluster is attached covalently to the polypeptide matrix through Fe−S^γ bonds to cysteines 43, 46, 63, and 77. The side chains of Tyr19, Phe48, Trp60, Phe66, Trp76, Trp80, and other nonpolar residues encapsulate the cluster in a hydrophobic cavity that is inaccessible to solvent. Tyr19, which contacts the [Fe_4S_4] core, has been suggested to play a particularly important structural role. In both oxidation states, the cysteinyl and core inorganic sulfur atoms are involved in H-bonding interactions with peptide NH protons.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/75324,
title ="Probing Protein Folding with Substitution-Inert Metal Ions. Folding Kinetics of Cobalt(III)-Cytochrome c",
author = "Tezcan, F. Akif and Winkler, Jay R.",
journal = "Journal of the American Chemical Society",
volume = "121",
number = "50",
pages = "11918-11919",
month = "December",
year = "1999",
doi = "10.1021/ja993447k",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170322-152801776",
note = "© 1999 American Chemical Society. \n\nReceived September 23, 1999. Publication Date (Web): December 3, 1999. \n\nWe thank Ivano Bertini, Kara Bren, and Paola Turano for helpful discussions. This work was supported by NSF (MCB-9974477) and the Arnold and Mabel Beckman Foundation.",
revision_no = "14",
abstract = "Ligand-substitution processes at the heme strongly influence peptide backbone dynamics during the folding of cytochrome c (cyt c). When cyt c is unfolded with guanidine hydrochloride (GuHCl) at pH 7, one of the axial ligands (Met 80) is replaced by a nitrogenous base from an amino acid residue; this misligation introduces an energy barrier with an associated folding time of several hundred milliseconds. A great deal of evidence points to His 26 or His 33 as the ligand in unfolded horse heart cyt c. Nevertheless, recent studies indicate that other bases (Lys or N-terminus in yeast cyt c) can act as ligands as well. We have found that the substitution-inert heme in the Co(III) derivative of cyt c (Co-cyt c) allows a closer look at the folding kinetics and the ligands in the unfolded form of this protein.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/733,
title ="Optical detection of cytochrome P450 by sensitizer-linked substrates",
author = "Dmochowski, Ivan J. and Crane, Brian R.",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "96",
number = "23",
pages = "12987-12990",
month = "November",
year = "1999",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:DMOpnas99",
note = "© 1999 by The National Academy of Sciences \n\nContributed by Harry B. Gray, September 14, 1999. \n\nWe thank A. M. Bilwes for assistance with protein expression and crystallization, D. C. Rees for use of facilities and comments, S. G. Sligar for providing a P450cam vector, J. H. Dawson for several discussions, M. Machczynski for computational assistance, and the Stanford Synchrotron Research Laboratory for use of data collection facilities. I.J.D. is a National Institutes of Health predoctoral trainee (Grant GM08346). B.R.C. is a Helen Hay Whitney Postdoctoral Fellow. This work was supported by National Science Foundation Grant CHE9807150. \n\nData deposition: The atomic coordinates of the P450:Ru-C9-Ad structure have been deposited in the Protein Data Bank, www.rcsb.org (PDB ID code 1qmq). \n\nThe publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. §1734 solely to indicate this fact.",
revision_no = "8",
abstract = "The ability to detect, characterize, and manipulate specific biomolecules in complex media is critical for understanding metabolic processes. Particularly important targets are oxygenases (cytochromes P450) involved in drug metabolism and many disease states, including liver and kidney dysfunction, neurological disorders, and cancer. We have found that Ru photosensitizers linked to P450 substrates specifically recognize submicromolar cytochrome P450cam in the presence of other heme proteins. In the P450:Ru-substrate conjugates, energy transfer to the heme dramatically accelerates the Ru-luminescence decay. The crystal structure of a P450cam:Ru-adamantyl complex reveals access to the active center via a channel whose depth (Ru-Fe distance is 21 Å) is virtually the same as that extracted from an analysis of the energy-transfer kinetics. Suitably constructed libraries of sensitizer-linked substrates could be employed to probe the steric and electronic properties of buried active sites.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/57041,
title ="Electron tunneling in biological molecules",
author = "Winkler, Jay R. and Di Bilio, Angel J.",
journal = "Pure and Applied Chemistry",
volume = "71",
number = "9",
pages = "1753-1764",
month = "September",
year = "1999",
doi = "10.1351/pac199971091753",
issn = "0033-4545",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150428-092352002",
note = "© 1999 IUPAC.\n\nOur work on protein electron transfer is supported by the National Institutes of Health, the National Science Foundation, and the Arnold and Mabel Beckman Foundation. ",
revision_no = "13",
abstract = "Electron transfers in photosynthesis and respiration commonly occur between protein-bound prosthetic groups that are separated by large molecular distances (often greater\nthan 10Å). Although the electron donors and acceptors are expected to be weakly coupled, the reactions are remarkably fast and proceed with high specificity. Tunneling timetables based on analyses of Fe^(2+)/Cu^+ to Ru^(3+) electron-transfer rates for Ru-modified heme and copper\nproteins reveal that the structure of the intervening polypeptide can control these distant donor-acceptor couplings. Multistep tunneling can account for the relatively rapid Cu^+ to Re^(2+) electron transfer observed in Re-modified azurin.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/943,
title ="Cytochrome b562 folding triggered by electron transfer: Approaching the speed limit for formation of a four-helix-bundle protein",
author = "Wittung-Stafshede, Pernilla and Lee, Jennifer C.",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "96",
number = "12",
pages = "6587-6590",
month = "June",
year = "1999",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:WITpnas99",
note = "© 1999 by the National Academy of Sciences. \n\nContributed by Harry B. Gray, April 6, 1999. \n\nWe thank Kevin Plaxco and Peter Wolynes for communication of unpublished results as well as several stimulating discussions. P.W.-S. acknowledges a postdoctoral fellowship from the Swedish Technical Research Council. J.C.L. acknowledges a graduate fellowship from the Ralph M. Parsons Foundation. This work was supported by the National Science Foundation (Grant MCB 9630465). \n\nThe publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked \"advertisement\" in accordance with 18 U.S.C. §1734 solely to indicate this fact.",
revision_no = "9",
abstract = "Ferrocytochrome b(562) [Fe(II)cyt b(562)] folding can be triggered by photoinduced electron transfer to unfolded Fe (III)cyt b(562) in 2-3 M guanidine hydrochloride solutions. The folding rates increase with decreasing guanidine hydrochloride; the extrapolated time constant for this folding process in the absence of denaturant (5 mu s) is near the predicted value for intrachain diffusion. The relatively smooth energy landscape indicated for Fe(II)cyt b(562) folding accords with the helical, highly symmetrical structure of the protein.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/75327,
title ="The red form of [Re(phen)(CO)_3(H_2O)]CF_3SO_3•H_2O",
author = "Connick, William B. and Di Bilio, Angel J.",
journal = "Acta Crystallographica Section C",
volume = "55",
number = "6",
pages = "913-916",
month = "June",
year = "1999",
doi = "10.1107/S0108270199001432",
issn = "0108-2701",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170322-160013568",
note = "© 1999 International Union of Crystallography. \n\n(Received 14 September 1998; accepted 26 January 1999) \n\nWe thank L. M. Henling for expert assistance and helpful discussions. This work was supported by the National Science Foundation and the National Institutes of Health.",
revision_no = "13",
abstract = "The coordination geometry of the cations in the red form of aquatricarbonyl(1,10-phenanthroline-N, N')rhenium(I) trifluoromethanesulfonate hydrate, [Re(C_(12)H_8N_2)(CO)_3-\n(H_2O)]CF_3SO_3•H_2O, is approximately octahedral, with a facial arrangement of the linearly coordinated carbonyl ligands. The phenanthroline (phen) ligands interleave to form a columnar r-stacked structure.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/79933,
title ="Inhibition of thermolysin and human α-thrombin by cobalt(III) Schiff base complexes",
author = "Takeuchi, Toshihiko and Böttcher, Arnd",
journal = "Bioorganic and Medicinal Chemistry",
volume = "7",
number = "5",
pages = "815-819",
month = "May",
year = "1999",
doi = "10.1016/S0968-0896(98)00272-7",
issn = "0968-0896",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170808-111051171",
note = "© 1999 Elsevier Science Ltd. \n\nReceived 25 August 1998, Accepted 21 October 1998, Available online 28 May 1999. \n\nA. B. thanks the Alexander von Humboldt foundation for a postdoctoral fellowship. This work was supported by NSF and Redox Pharmaceutical Corporation.",
revision_no = "9",
abstract = "Cobalt(III) Schiff base complexes have been shown to inhibit the replication of the ocular herpes virus. It is well known that these complexes have a high affinity for nitrogenous donors such as histidine residues, and it is possible that they bind to (and inhibit) an enzyme that is crucial to viral replication. In model studies, we have found that [Co(acacen)(NH_3)_2]+ is an effective irreversible inhibitor of thermolysin at millimolar concentrations; it also inhibits human α-thrombin. Axial ligand exchange with an active-site histidine is the proposed mechanism of inhibition. The activity of thermolysin and thrombin can be protected by binding a reversible inhibitor to the active site before addition of the cobalt(III) complex.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/86600,
title ="Role of Ligand Substitution in Ferrocytochrome c Folding",
author = "Telford, Jason R. and Tezcan, F. Akif",
journal = "Biochemistry",
volume = "38",
number = "6",
pages = "1944-1949",
month = "February",
year = "1999",
doi = "10.1021/bi981933z",
issn = "0006-2960",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180524-152940000",
note = "© 1999 American Chemical Society. \n\nReceived August 11, 1998; Revised Manuscript Received October 21, 1998. \n\nSupported by the National Science Foundation (MCB 9630465) and the National Institutes of Health (GM18660 to J.R.T.). \n\nWe thank Gary Mines and Torbjörn Pascher for assistance with certain experiments and for helpful discussions.",
revision_no = "11",
abstract = "The ligand substitutions that occur during the folding of ferrocytochrome c [Fe(II)cyt c] have been monitored by transient absorption spectroscopy. The folding reaction was triggered by photoinduced electron transfer to unfolded Fe(III)cyt c in guanidine hydrochloride (GuHCl) solutions. Assignments of ligation states were made by reference to the spectra of the imidazole and methionine adducts of N-acetylated microperoxidase 8. At pH 7, the heme in unfolded Fe(II)cyt c is ligated by native His18 and HisX (X = 26, 33) residues. The native Met80 ligand displaces HisX only in the last stages of folding. The ferroheme is predominantly five-coordinate in acidic solution; it remains five-coordinate until the native methionine binds the heme to give the folded protein (the rate of the methionine binding step is 16 ± 5 s^(-1) at pH 5, 3.2 M GuHCl). The evidence suggests that the substitution of histidine by methionine is strongly coupled to backbone folding.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/56983,
title ="X-ray Absorption Spectra of the Oxidized and Reduced Forms of C112D Azurin from Pseudomonas aeruginosa",
author = "DeBeer, Serena and Kiser, Cynthia N.",
journal = "Inorganic Chemistry",
volume = "38",
number = "3",
pages = "433-438",
month = "February",
year = "1999",
doi = "10.1021/ic9804622",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150424-155359723",
note = "© 1999 American Chemical Society. \n\nReceived April 23, 1998. \n\nThis research was supported by the NSF [CHE-9217628 (E.I.S.); CHE-9423181 (K.O.H.)] and the NIH [RR-01209 (K.O.H.); DK-19038 (H.B.G.)]. SSRL operations are funded by the Department of Energy, Office of Basic Energy Sciences. The Biotechnology Program is supported by the National Institutes of Health, National Center for Research Resources, Biomedical Technology Program and by the Department of Energy, Office of Biological and Environmental Research.",
revision_no = "11",
abstract = "The oxidized and reduced forms of a mutant of Pseudomonas aeruginosa azurin, in which the Cys112 has been replaced by an aspartate, have been studied by X-ray absorption spectroscopy. It is well established that the characteristic ∼600 nm absorption feature of blue copper proteins is due to the S(Cys112) 3pπ → Cu 3d_(x^2-y^2) charge-transfer transition. While other mutagenesis studies have involved the creation of an artificial blue copper site, the present work involves a mutant in which the native blue copper site has been destroyed, thus serving as a direct probe of the importance of the copper−thiolate bond to the spectroscopy, active site structure, and electron-transfer function of azurin. Of particular interest is the dramatic decrease in electron-transfer rates, both electron self-exchange (k_(ese) ≈ 10^5 M^(-1) s^(-1) wild-type azurin vs k_(ese) ≈ 20 M^(-1) s^(-1) C112D azurin) and intramolecular electron transfer to ruthenium-labeled sites (k_(et) ≈ 10^6 s^(-1) wild-type azurin vs k_(et) ≤ 10^3 s^(-1) C112D azurin), which is observed in the mutant. These changes may be a reflection of significant differences in electronic coupling into the protein matrix (HAB) and/or in the reorganization energy (λ). These effects can be probed by the use of Cu K-edge X-ray absorption spectroscopy, the results of which indicate both a decrease in the covalency of the active site and an expansion of ∼0.2 Å in the Cu coordination sphere trigonal plane upon reduction of the C112D mutant.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/53427,
title ="Structures of Ruthenium-modified Pseudomonas aeruginosa Azurin and [Ru(2,2’-bipyridine)_2(imidazole)_2)]SO_4•10H_2O",
author = "Faham, Salem and Day, Michael W.",
journal = "Acta Crystallographica Section D: Biological Crystallography",
volume = "55",
number = "2",
pages = "379-385",
month = "February",
year = "1999",
doi = "10.1107/S0907444998010464 ",
issn = "0907-4449",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150108-160523362",
note = "© 1999 International Union of Crystallography.\n\nReceived 29 January 1998;\nAccepted 27 July 1998.\n\nWe thank Michael Harrington, Jack Mizoguchi, Larry\nHenling and Jack Richards for helpful discussions. This work\nwas supported by NIH (DK19038 to HBG; GM45162 to\nDCR).",
revision_no = "8",
abstract = "The crystal structure of Ru(2,2'-bipyridine)_2(imidazole)(His83)azurin (RuAz) has been determined to 2.3 Å ¬resolution by X-ray crystallography. The spectroscopic and thermodynamic properties of both the native protein and [Ru(2,2'-bipyridine)_2(imidazole)_2]^(2+) are maintained in the modified protein. Dark-green RuAz crystals grown from PEG 4000, LiNO_3, CuCl_2 and Tris buffer are monoclinic, belong to the space group C2 and have cell parameters a = 100.6, b = 35.4, c = 74.7 Å and β = 106.5°. In addition, [Ru(2,2'-bipyridine)_2(imidazole)_2]SO_4•10H_2O was synthesized, crystallized and structurally characterized by X-ray crystallography. Red-brown crystals of this complex are monoclinic, space group P2_1/n, unit-cell parameters a = 13.230 (2), b = 18.197 (4), c = 16.126 (4) Å, β = 108.65 (2)°. Stereochemical parameters for the refinement of Ru(2,2'-bipyridine)_2(imidazole)(His83) were taken from the atomic coordinates of [Ru(2,2'-bipyridine)_2(imidazole)_2]^(2+). The structure of RuAz confirms that His83 is the only site of chemical modification and that the native azurin structure is not perturbed significantly by the ruthenium label.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/86638,
title ="Spectroscopy and Electrochemistry of mer-[RuCl_3(dmso)(tmen)]. Dimethylsulfoxide Is Sulfur-Bonded to Ru(II), Ru(III), and Ru(IV)",
author = "Rack, Jeffrey J. and Gray, Harry B.",
journal = "Inorganic Chemistry",
volume = "38",
number = "1",
pages = "2-3",
month = "January",
year = "1999",
doi = "10.1021/ic981029v",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180525-135926367",
note = "© 1999 American Chemical Society. \n\nReceived August 25, 1998. \n\nWe thank Mike Day, Larry Henling, Akif Tezcan, and Jay Winkler for experimental assistance and helpful discussions. This work was supported by ARO (DAAH04-95-1-0125), NSF, and NIST (ATP) Award 70NANB5H1031.",
revision_no = "11",
abstract = "The discovery that halo−ruthenium(sulfoxide) complexes exhibit anticancer activity has stimulated interest in the nature of bonding of metal ions to dimethylsulfoxide (dmso). Both M−S and M−O bonds are observed in metal complexes containing dmso, with the former mode prevalent with “soft” metal centers. The importance of dπ-S back-bonding in S-bonded complexes has been addressed by several investigators. Especially revealing was the finding by Taube and co-workers that S to O linkage isomerism can be induced by oxidation of pentaammineruthenium(II) to ruthenium(III), thereby suggesting that dπ-S bonding is a stabilizing factor only in the lower oxidation state. However, the observation that other Ru(III)(chloro)(dmso) complexes are S-bonded led Alessio and Calligaris to propose a role for dπ-S bonding in Ru(III) as well. In the course of our work on a related complex, mer-[RuCl_3(dmso)(tmen)] (dmso is dimethylsulfoxide; tmen is N,N,N‘,N‘-tetramethylethylenediamine), we have found that dmso also can be S-bonded to Ru(IV). Our findings suggest that S(dmso) σ-donation to Ru is extensive in the Ru(III) and Ru(IV) states.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/81181,
title ="Histidine-Tailed Microperoxidase-10: A pH-Dependent Ligand Switch",
author = "Cheek, Jennifer and Low, Donald W.",
journal = "Biochemical and Biophysical Research Communications",
volume = "253",
number = "2",
pages = "195-198",
month = "December",
year = "1998",
doi = "10.1006/bbrc.1998.9778",
issn = "0006-291X",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170906-092356727",
note = "© 1998 Academic Press. \n\nReceived 6 November 1998. \n\nWe thank Drs. Edmund W. Svastits and John J. Rux for assembling the MCD software and Alycen Pond for helpful discussions. Support for this study was provided by NIH Grant GM 26730 (J.H.D.) and NSF Grant CHE-9807150 (H.B.G.).",
revision_no = "9",
abstract = "The electronic absorption and magnetic circular dichroism (MCD) spectra of ferric histidine-tailed microperoxidase-10 (His-MP10) change dramatically as the pH is raised from 1.8 to 11.8. Two distinct species are observed (pK_a= 4.4). The spectra of acidic ferric His-MP10 nearly match those of ferric mesoporphyrin-reconstituted myoglobin and so the axial ligands are assigned to be histidine and water. The retention of histidine ligation below pH 4 contrasts to the behavior of myoglobin and horseradish peroxidase which convert to five-coordinate water ligated and then lose the heme prosthetic group at even lower pH. Neutral and alkaline ferric His-MP10 have spectra that are very similar to those of the imidazole complex of ferric mesoporphyrin-reconstituted myoglobin. Thus, we conclude that it is bis-histidine ligated with the C-terminal histidine bound as the sixth ligand. Thus, ferric His-MP10 exhibits a pH-dependent ligand switch with a change in axial ligation from water and histidine at low pH to bis-histidine at neutral and alkaline pH.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/80944,
title ="High-potential states of blue and purple copper proteins",
author = "Wittung-Stafshede, Pernilla and Gomez, Ester",
journal = "Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology",
volume = "1388",
number = "2",
pages = "437-443",
month = "November",
year = "1998",
doi = "10.1016/S0167-4838(98)00205-2",
issn = "0167-4838",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170830-081553147",
note = "© 1998 Elsevier Science B.V. \n\nReceived 27 April 1998, Revised 30 July 1998, Accepted 19 August 1998, Available online 20 April 1999. \n\nP.W.-S. thanks the Swedish Technical Research Council for a postdoctoral fellowship. This investigation was supported by NSF, NIH, the Arnold and Mabel Beckman Foundation, the Nobel Committee for Chemistry (B.G.M.), the Swedish Natural Science Research Council (B.G.K.), and the Research Corporation (Cottrell Science Award to M.G.H.).",
revision_no = "12",
abstract = "Electrochemical measurements show that there are high-potential states of two copper proteins, Pseudomonas aeruginosa azurin and Thermus thermophilus Cu_A domain; these perturbed states are formed in guanidine hydrochloride (GuHCl) solution in which the proteins are still blue (azurin) and purple (Cu_A). In each case, the high-potential state forms reversibly. Absorption (azurin, Cu_A), visible circular dichroism (azurin, Cu_A), resonance-Raman (Cu_A), and EPR (Cu_A) spectra indicate that the structure of the oxidized copper site of each high-potential form is very similar to that of the native protein. It is proposed that GuHCl perturbs one or more H-bonds in the blue or purple copper active site, thereby allowing Cu(I) to adopt a more favorable coordination structure than that in the rigid cavity of the native protein.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/81483,
title ="Protein Folding Triggered by Electron Transfer",
author = "Telford, Jason R. and Wittung-Stafshede, Pernilla",
journal = "Accounts of Chemical Research",
volume = "31",
number = "11",
pages = "755-763",
month = "November",
year = "1998",
doi = "10.1021/ar970078t",
issn = "0001-4842",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170915-091501815",
note = "© 1998 American Chemical Society. \n\nReceived January 16, 1998. Publication Date (Web): October 28, 1998. \n\nThis work was supported by the NSF (Grant MCB-9630465 to J.R.W.; Grant CHE-9508533 to H.B.G.). Postdoctoral fellowships from the NIH (J.R.T.) and TFR-Sweden (P.W.-S.) are acknowledged with thanks. Important contributions to our ET-triggered folding studies have been made by Gary Mines, John Chesick, Sonny Lee, Don Low, Bo Malmström, Torbjörn Pascher, and F. Akif Tezcan. We also thank Bill Eaton, George McLendon, José Onuchic, and Peter Wolynes for helpful discussions. H.B.G. thanks Balliol College and the Inorganic Chemistry Laboratory, University of Oxford, for providing a stimulating intellectual environment during 1997−98.",
revision_no = "11",
abstract = "Proteins do not fold by randomly searching a large\nnumber of nearly degenerate configurations; instead, an\nensemble of unfolded molecules must traverse a complicated\nenergy landscape to reach a thermodynamically stable structure. The fastest nuclear motions in proteins,\nrotations about single bonds, occur on the picosecond\ntime scale and accompany both secondary- and\ntertiary-structure-forming processes. Short segments of\nsecondary structure (e.g., α-helices) can be formed in\nnanoseconds, whereas the large-scale, collective motions\nassociated with the development of tertiary structure fall\nin the microsecond to millisecond range. Misfolded\nstructures or traps are frequently encountered in folding\nprocesses; escape from these traps (e.g., proline isomerization) can take seconds or even minutes. Understanding the key events in folding and identifying any partially folded intermediates are major goals of theoretical and experimental work.\n",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/86411,
title ="Time-Resolved Resonance Raman Spectroscopy at Low Temperature. The Excited-State Metal−Metal Stretching Frequency of Rh_2(TMB)_4^(2+)(TMB = 2,5-Dimethyl-2,5-diisocyanohexane)",
author = "Dallinger, Richard F. and Carlson, Matt J.",
journal = "Inorganic Chemistry",
volume = "37",
number = "19",
pages = "5011-5013",
month = "September",
year = "1998",
doi = "10.1021/ic980130x",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180515-133335193",
note = "© 1998 American Chemical Society. \n\nReceived February 3, 1998. Publication Date (Web): September 3, 1998. \n\nWe thank Jay Winkler for assistance with several experiments. This work was supported by the NSF, the Caltech SURF program (M.J.C.), and the Arnold and Mabel Beckman Foundation.",
revision_no = "9",
abstract = "The excited-state metal−metal stretching frequency of the bridged binuclear complex Rh_2(TMB)_4^(2+) (TMB = 2,5-dimethyl-2,5-diisocyanohexane) obtained from time-resolved resonance Raman spectra is 151 cm^(-1), as compared to 50 cm^(-1) in the ground state, indicating a much stronger Rh−Rh bond in the excited state than in the ground state. The key experimental innovation was lowering the solution sample temperature to just above the glass transition to increase the excited triplet state lifetime relative to the laser pulse width.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/85293,
title ="Folding of Deoxymyoglobin Triggered by Electron Transfer",
author = "Wittung-Stafshede, Pernilla and Malmström, Bo G.",
journal = "Journal of Physical Chemistry A",
volume = "102",
number = "28",
pages = "5599-5601",
month = "July",
year = "1998",
doi = "10.1021/jp9802228",
issn = "1089-5639",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180313-160333459",
note = "© 1998 American Chemical Society.\n\nReceived: November 17, 1997; In Final Form: April 1, 1998.\nPublication Date (Web): May 23, 1998.\n\nP.W.-S. thanks the Swedish Technical Research Council for a postdoctoral fellowship and Ivan Dmochowski for assistance with the diode array measurements. This work was supported by the National Science Foundation (H.B.G., J.R.W.), the Nobel Institute for Chemistry (B.G.M.), and the Arnold and Mabel Beckman Foundation.\n",
revision_no = "10",
abstract = "The met and deoxy forms of sperm whale myoglobin (Mb) can be unfolded by guanidine hydrochloride (GuHCl). Electronic absorption and circular dichroism spectroscopic measurements show that folded deoxyMb is more stable than the folded met protein. Laser excitation of NADH generates species that rapidly reduce unfolded metMb, triggering the formation of folded deoxyMb in less than 10 ms (pH 7.0, 2.5 to 3 M GuHCl, 20 °C). At comparable reaction driving forces (∼10 kJ/mol), deoxyMb folds much faster than reduced cytochrome c.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/57025,
title ="Electron tunneling in Ru-modified His46Asp azurin. Coupling through the Cu ligands",
author = "Regan, J. J. and Di Bilio, A. J.",
journal = "Inorganica Chimica Acta",
volume = "275-276",
number = "1-2",
pages = "470-480",
month = "July",
year = "1998",
doi = "10.1016/S0020-1693(98)00066-8",
issn = "0020-1693",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150427-151804934",
note = "© 1998 Elsevier Science S.A.\n\nReceived 2 June 1997: accepted 26 September 1997.\n\nWe thank Claire Slulter and Jack Mizoguchi for helpful discussions. This work was supported by the National Institutes of Health (DK19038 to H.B.G.; GM16424 to J.H.R.) and the Department of Energy (DE-FG03-96ER62219 to\nJ.J.R.).",
revision_no = "11",
abstract = "We compare electron transfer (ET) rates in two chemically modified Pseudomonas aeruginosa azurins, to examine the role of the Cu ligands in the ET coupling. In both cases, ET proceeded from Cu^+ to a Ru(bpy)_2(im)^(3+) attached to the native His83. In this otherwise native system, the Cu^+ Ru^(3+) → Cu^(2+)Ru^(2+) rate is 1.2(1) × 10^6 s^(−1) (−ΔG° = 0.76 eV) (J.J. Regan, A.J. Di Bilio, R. Langen, L.K. Skov, J.R. Winkler, H.B. Gray and J.N. Onuchic, Chem. Biol., 2 (1995) 489 [1]; A.J. Di Bilio, M.G. Hill, N. Bonander, B.G. Karlsson, R.M. Villahermosa, B.G. Malmström, J.R. Winkler and H.B. Gray, J. Am. Chem. Soc., 119 (1997) 9921 [2]). In the His46Asp mutant (46 being one of the Cu ligands), the rate drops to 3.2(4) × 10^4 s^(−1) (−ΔG° ∼ 0.78 eV). Analysis suggests that this drop is primarily due to a disruption of electronic tube coupling, rather than to just a change in the driving force and/or reorganization energy of the reaction.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/86659,
title ="Electronic Structures of Nitridomanganese(V) Complexes",
author = "Chang, Christopher J. and Connick, William B.",
journal = "Inorganic Chemistry",
volume = "37",
number = "12",
pages = "3107-3110",
month = "June",
year = "1998",
doi = "10.1021/ic970598k",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180529-105625319",
note = "© 1998 American Chemical Society. \n\nReceived May 19, 1997. \n\nWe thank J. Du Bois, L. Henling, J. Hong, G. Rossman, and T. Takeuchi for expert technical assistance as well as several helpful discussions. C.J.C. thanks the A. A. Noyes Foundation for a Caltech SURF award. D.W.L. acknowledges the Parsons Foundation for a fellowship. This work was supported by the National Science Foundation.",
revision_no = "11",
abstract = "The single-crystal polarized absorption and circular dichroism spectra of the nitridomanganese(V) complexes (salen)Mn⋮N (1), (1S,2S-(−)-saldpen)Mn⋮N (2), and (1R,2R-(+)-saldpen)Mn⋮N (3) have been measured [salen = N,N‘-ethylenebis(salicylideneaminato) dianion, 1S,2S-(−)-saldpen = N,N‘-(1S,2S-(−)-diphenyl)ethylenebis(salicylideneaminato) dianion, and 1R,2R-(+)-saldpen = N,N‘-(1R,2R-(+)-diphenyl)ethylenebis(salicylideneaminato) dianion]. As revealed by X-ray crystal structure analyses, these molecules have a distorted square-pyramidal geometry with a short Mn⋮N bond distance (1.52(3) Å for 2). The Cs compounds have a low-spin^ 1A‘[a‘(x^2 − y^2)]^2 ground state. The lowest absorption system (∼600 nm) consists of two components that are separated by approximately 4000 cm^(-1); these are assigned to ^1A‘ → ^1A‘[a‘(x^2 − y^2)a‘(yz)] (14\u2009900 cm^(-1)) and ^1A‘ → ^1A‘‘[a‘(x^2 − y^2)a‘‘(xz)] (18\u2009900 cm^(-1)) transitions.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/603,
title ="Isolation of a myoglobin molten globule by selective cobalt(III)-induced unfolding",
author = "Blum, Ofer and Haiek, Abed",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "95",
number = "12",
pages = "6659-6662",
month = "June",
year = "1998",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:BLUpnas98",
note = "© 1998 by The National Academy of Sciences. \n\nContributed by Harry B. Gray, April 6, 1998. \n\nWe thank Drs. Bassil Dahiyat and Michel E. Goldberg for discussions. O.B. acknowledges Rothchild and Fulbright postdoctoral fellowships. This work was supported by the National Science Foundation, the Arnold and Mabel Beckman Foundation, and the Redox Pharmaceutical Corporation.",
revision_no = "7",
abstract = "Reaction of the Schiff-base complex [Co(acetylacetonate-ethylenediimine)(NH3)(2)](+) with metmyoglobin at pH 6.5 yields a partially folded protein containing six Co(III) complexes. Although half of its a-helical secondary structure is retained, absorption and Co spectra indicate that the tertiary structure in both B-F and AGH domains is disrupted in the partially folded protein. In analogy to proton-induced unfolding, it is likely that the loss of tertiary structure is triggered by metal-ion binding to histidines. Cobalt(III)-induced unfolding of myoglobin is unique in its selectivity (other proteins are unaffected) and in allowing the isolation of the partially folded macromolecule (the protein does not refold or aggregate upon removal of free denaturant). ",
}
@book_section {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/85677,
title ="Spectroscopic Studies of Ferrocytochrome c Folding",
author = "Mines, Gary A. and Winkler, Jay R.",
number = "692",
pages = "198-211",
month = "June",
year = "1998",
doi = "10.1021/bk-1998-0692.ch010",
issn = "1947-5918",
isbn = "9780841235601",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180406-091535617",
note = "© 1998 American Chemical Society. \n\nPublished in print 9 June 1998. \n\nThis work was supported by the National Science Foundation (MCB-9630465), the National Institutes of Health, and the Arnold and Mabel Beckman Foundation.",
revision_no = "11",
abstract = "Electron-transfer triggering has been employed in a comparison of the folding energetics and kinetics of cytochrome c from horse and Saccharomyces cerevisiae. These two proteins, with just 60% sequence identity but very similar backbone structures, fold at very different rates at a given denaturant concentration, but at nearly the same rate when their folding free energies are the same. Differences in the amino-acid sequences shift the position of the folding/unfolding equilibrium, but do not appear to alter the location of the transition state along the folding coordinate.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/86640,
title ="Manganese Microperoxidase-8",
author = "Low, Donald W. and Abedin, Sakena",
journal = "Inorganic Chemistry",
volume = "37",
number = "8",
pages = "1841-1843",
month = "April",
year = "1998",
doi = "10.1021/ic971166c",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180525-140834681",
note = "© 1998 American Chemical Society. \n\nReceiVed September 13, 1997. \n\nWe thank Jane Saunders, Gary Hathaway, and Peter Green for assistance with mass spectrometry. S.A. was a participant in the Caltech SURF program. D.W.L. acknowledges a fellowship from the Parsons Foundation. This work was supported by the NSF.",
revision_no = "11",
abstract = "Demetalation of Fe(III) microperoxidase-8 (MP8) by anhydrous HF gives metal-free MP8, a convenient starting material for a wide variety of metal-substituted MP8 derivatives, including Mn(III)MP8. Mn(III)MP8 was produced by treatment of metal-free MP8 with manganous acetate in aerated aqueous solution; it was characterized by mass spectrometry and UV−visible absorption spectroscopy. Resonance Raman spectra suggest that Mn(III)MP8 contains histidine and water axial ligands at neutral pH. The Mn(IV)=O derivative is readily prepared by oxidation of Mn(III)MP8 with hydrogen peroxide or Ru(bpy)_3^(3+) (bpy = 2,2‘-bipyridine).",
}
@book_section {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/85675,
title ="Electron Tunneling in Engineered Proteins",
author = "Mines, Gary A. and Ramirez, Benjamin E.",
number = "254",
pages = "51-63",
month = "April",
year = "1998",
doi = "10.1021/ba-1998-0254.ch004",
issn = "0065-2393",
isbn = "9780841234994",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180406-080327489",
note = "© 1998 American Chemical Society. \n\nPublished in print 17 April 1998. \n\nOur work on electron transfer in proteins is supported by the National Science Foundation, the National Institutes of Health, and the Arnold and Mabel Beckman Foundation.",
revision_no = "11",
abstract = "Semiclassical theory predicts that the rates of electron transfer (ET) reactions depend on the reaction driving force (-ΔG°), a nuclear reorganization parameter (λ), and the electronic-coupling strength (H_(AB)) between reactants and products at the transition state. ET rates reach their maximum values (k°_(ET)) when the nuclear factor is optimized (-ΔG° = λ); these k°_(ET) values are limited only by the strength (H^2_(AB)) of the electronic interaction between the donor (D) and acceptor (A). The dependence of the rates of Ru(His33)cytochrome c ET reactions on -ΔG° (0.59-1.4 eV) accords closely with semiclassical predictions. The anomalously high rates of highly exergonic (-ΔG° ≥ 1.4 eV) ET reactions suggest initial formation of an electronically excited ferroheme in these cases. Coupling-limited Cu^+ to Ru^(3+) and Fe^(2+) to Ru^(3+) ET rates for several Ru-modified proteins are in good agreement with the predictions of a tunneling-pathway model. In azurin, a blue copper protein, the distant D-A pairs are relatively well coupled (k°_(ET) decreases exponentially with Cu-Ru distance; the decay constant is 1.1 Å^(-1)). In contrast to the extended peptides found in azurin and other β-sheet proteins, helical structures have torturous covalent pathways owing to the curvature of the peptide backbone. The decay constants estimated from ET rates for D-A pairs separated by long sections of α helix in myoglobin and the photosynthetic reaction center are between 1.25 and 1.6 Å^(-1).",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/83359,
title ="Effect of Redox State on the Folding Free Energy of a Thermostable Electron-Transfer Metalloprotein: The Cu_A Domain of Cytochrome Oxidase from Thermus thermophilus",
author = "Wittung-Stafshede, Pernilla and Malmström, Bo G.",
journal = "Biochemistry",
volume = "37",
number = "9",
pages = "3172-3177",
month = "March",
year = "1998",
doi = "10.1021/bi972901z",
issn = "0006-2960",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20171120-144202285",
note = "© 1998 American Chemical Society. \n\nReceived November 26, 1997. Publication Date (Web): February 14, 1998. \n\nThis work was supported by the National Institutes of Health (Grant DK19038), the National Science Foundation (Grant MCB9630465), and the Swedish Natural Science Research Council. P.W.-S. is the recipient of a postdoctoral fellowship from Swedish Technical Research Council.\n\nWe thank Dr. Stephen L. Mayo for the use of the Aviv spectropolarimeter.",
revision_no = "13",
abstract = "The unfolding of the Cu_A domain of cytochrome oxidase from the thermophilic bacterium Thermus thermophilus, induced by guanidine hydrochloride (GuHCl)^1 at different temperatures, has been monitored by CD as well by electronic absorption (with the oxidized protein) and by fluorescence (with the reduced protein). The same unfolding curves were obtained with the different methods, providing evidence for a two-state model for the unfolding equilibrium. This was also supported by the shape of the unfolding equilibrium curves and by the observed refolding of the unfolded, oxidized protein on dilution of the denaturant. The oxidized protein cannot be unfolded by GuHCl at room temperature, and it was found to be thermally very stable as well, since, even in the presence of 7 M GuHCl, it is not fully unfolded until above 80 °C. For the reduced protein at room temperature, the unfolding equilibrium curve yielded a folding free energy of −65 kJ/mol. The corresponding value for the oxidized protein (−85 kJ/mol) could be estimated indirectly from a thermodynamic cycle connecting the folded and unfolded forms in both oxidation states and the known reduction potentials of the metal site in the folded and unfolded states; the potential is increased on unfolding, consistent with the higher folding stability of the oxidized form. The difference in folding stability between the oxidized and reduced proteins (20 kJ/mol) is exceptionally high, and this is ascribed to the unique structure of the dinuclear CuA site. The unfolded, reduced protein was found to refold partially on oxidation with ferricyanide.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/85271,
title ="Aerobic Epoxidation of Olefins Catalyzed by Electronegative Vanadyl Salen Complexes",
author = "Chang, Christopher J. and Labinger, Jay A.",
journal = "Inorganic Chemistry",
volume = "36",
number = "25",
pages = "5927-5930",
month = "December",
year = "1997",
doi = "10.1021/ic970824q",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180313-091844236",
note = "© 1997 American Chemical Society. \n\nReceived July 2, 1997; Publication Date (Web): December 3, 1997. \n\nWe thank Don Low, Mahdi Abu-Omar, and Jeff Rack for helpful discussions. C.J.C. thanks the Caltech SURF program and the A. A. Noyes Foundation for an award. This work was supported by the Bayer Foundation and the National Science Foundation.",
revision_no = "12",
abstract = "Vanadyl salen complexes bearing electron-withdrawing substituents have been prepared and characterized. Systematic substitutions on the ancillary ligand have allowed V^(5+)/V^(4+) reduction potentials to be tuned over a range of approximately 500 mV. The complexes are catalysts for the aerobic epoxidation of cyclohexene; catalytic activity roughly increases with increasing V^(5+)/V^(4+) reduction potential. The mechanism likely involves oxygen transfer from intermediate hydroperoxides that are formed by radical-chain autoxidation.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/86499,
title ="Photooxidation of Platinum(II) Diimine Dithiolates",
author = "Connick, William B. and Gray, Harry B.",
journal = "Journal of the American Chemical Society",
volume = "119",
number = "48",
pages = "11620-11627",
month = "December",
year = "1997",
doi = "10.1021/ja9723803",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180521-110903590",
note = "© 1997 American Chemical Society. \n\nReceived July 16, 1997. \n\nWe thank A. J. Di Bilio, M. G. Hill, L. M. Henling, V. M. Miskowski, and J. R. Winkler for expert technical assistance and helpful discussions. This work was supported by the National Science Foundation.",
revision_no = "12",
abstract = "The violet color of Pt(bpy)(bdt) (bpy = 2,2‘-bipyridine; bdt = 1,2-benzenedithiolate) is due to a Pt/S → diimine charge-transfer transition; the emission originates from the corresponding triplet state (τ = 460 ns). Photochemical oxidation of Pt(bpy)(bdt) occurs in the presence of oxygen in N,N-dimethylformamide, acetonitrile, or dimethyl sulfoxide solution; the reaction has been investigated by ^1H NMR and UV−visible absorption spectroscopy. Singlet oxygen produced by energy transfer from the excited complex is implicated as the active oxygen species, in sequential formation of sulfinate, Pt(bpy)(bdtO_2), and disulfinate, Pt(bpy)(bdtO_4), products. Both products have been characterized by X-ray crystallography. The rate of photooxygenation is strongly dependent on water concentration, and transient absorption spectra are consistent with the formation of at least one intermediate. As a whole, our data suggest that the photooxidation chemistry of platinum(II) diimine dithiolates is similar to that of organic sulfides.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/81241,
title ="Electron tunneling in structurally engineered proteins",
author = "Gray, Harry B. and Winkler, Jay R.",
journal = "Journal of Electroanalytical Chemistry",
volume = "438",
number = "1-2",
pages = "43-47",
month = "November",
year = "1997",
doi = "10.1016/S0022-0728(96)05024-3",
issn = "1572-6657",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170907-102343386",
note = "© 1997 Elsevier Science. \n\nReceived 1 August 1996. \n\nOur work on electron transfer in proteins is supported by the National Science foundation, the National Institutes of Health, and the Arnold and Mabel Beckman Foundation.",
revision_no = "9",
abstract = "Photosynthesis, respiration, nitrogen fixation, drug metabolism, DNA synthesis, and immune response are among the scores of biological processes that rely heavily on long-range (10 to 25 Å) protein electron-transfer (ET) reactions. Semiclassical theory predicts that the rates of these reactions depend on the reaction driving force −ΔG°, a nuclear reorganization parameter λ, and the electronic-coupling strength H_(AB) between reactants and products at the transition state: ET rates (k°_(ET)) reach their maximum values when the nuclear factor is optimized (−ΔG° = λ); these k_(ET)° values are limited only by the strength (H_(AB)^2) of the electronic interaction between the donor (D) and acceptor (A). Coupling-limited Cu^+ to Ru^(3+) and Fe^(2+) to Ru^(3+) ET rates have been extracted from kinetic studies on several Ru-modified proteins. In azurin, a blue copper protein, the distant D/A pairs are relatively well coupled (k°_(ET) decreases exponentially with R(Cu\ue5f8Ru); the decay constant is 1.1 Å^(−1)). In contrast to the extended peptides found in azurin and other β-sheet proteins, helical structures have tortuous covalent pathways owing to the curvature of the peptide backbone. The decay constants estimated from ET rates for D/A pairs separated by long sections of the α helix in myoglobin and the photosynthetic reaction center are between 1.25 and 1.6 Å^(−1).",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/86442,
title ="Rapid Formation of a Four-Helix Bundle. Cytochrome b_(562) Folding Triggered by Electron Transfer",
author = "Wittung-Stafshede, Pernilla and Gray, Harry B.",
journal = "Journal of the American Chemical Society",
volume = "119",
number = "40",
pages = "9562-9563",
month = "October",
year = "1997",
doi = "10.1021/ja971855n",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180517-150025275",
note = "© 1997 American Chemical Society. \n\nReceived June 5, 1997. Publication Date (Web): October 8, 1997. \n\nDedicated to Bo Malmström on the occasion of his 70th birthday. We thank S. Sligar (University of Illinois) for a generous gift of the plasmid containing the cytochrome b_(562) gene; N. Farrow for E. coli cells containing the plasmid as well as helpful discussions regarding purification; and J. Telford for assistance with the laser experiments. This work was supported by the Swedish Technical Research Council (PW-S) and the National Science Foundation (MCB-9630465).",
revision_no = "10",
abstract = "Understanding how the secondary and tertiary structures of\nproteins are formed from non-native conformations is a continuing challenge for both theory and experiment. This complex process involves dynamics on time scales that range from picoseconds to minutes. We have shown previously that the folding of redox-active proteins can be triggered by electron transfer (ET), thereby opening the way for investigations of early events in the folding process. Since it is important that the redox-active cofactor remains bound to the unfolded protein (eliminating the possibility that the rate-limiting step will be\nbimolecular capture of the cofactor), we initially thought that only redox proteins with covalently attached cofactors would be amenable to study by this method. Indeed, thus far we have restricted our work on folding dynamics to ferrocytochrome c, a protein with a covalently attached heme.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/57051,
title ="Paramagnetic NMR Spectroscopy of Cobalt(II) and Copper(II) Derivatives of Pseudomonas aeruginosa His46Asp Azurin",
author = "Vila, A. J. and Ramirez, B. E.",
journal = "Inorganic Chemistry",
volume = "36",
number = "20",
pages = "4567-4570",
month = "September",
year = "1997",
doi = "10.1021/ic9703282 ",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150428-132741371",
note = "© 1997 American Chemical Society.\n\nReceived March 19, 1997.\n\nA.J.V. thanks the Fundacion Antorchas and TWAS for research funds, ACS for a travel grant, and IQUIOS for use of an ACE 200 spectrometer. This research was supported by the NIH (DK19038 to H.B.G.; GM16424 to J.H.R.).",
revision_no = "14",
abstract = "NMR spectra of paramagnetic Co(II) and Cu(II) derivatives of Pseudomonas aeruginosa His46Asp azurin have\nbeen investigated. In each derivative, assignment of hyperfine-shifted resonances outside the diamagnetic envelope\nof spectra recorded at 200 and 500 MHz confirms that the Asp carboxylate is coordinated to the paramagnetic\nmetal center. The reduced paramagnetic shifts of the Cys112 proton resonances in Cu(II) and Co(II) His46Asp\nazurins compared to those of the corresponding wild type proteins indicate that metal-S(Cys) bonding is weakened\nin this mutant. The downfield shifts of the γ-CH_2 of Met121 suggest a stronger interaction between the metal\nand the Met thioether group than is present in the wild type protein. Molecular modeling of the metal site structure\nindicates a distorted tetrahedral geometry with Asp46 (monodentate carboxylate), Cys112, and His117 equatorial\nligands. In this structure, the metal ion is shifted 0.3 Å out of the O(Asp)S(Cys)N(His) trigonal plane toward\nMet121.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/81589,
title ="Solution Structure of Oxidized Horse Heart Cytochrome c",
author = "Banci, Lucia and Bertini, Ivano",
journal = "Biochemistry",
volume = "36",
number = "32",
pages = "9867-9877",
month = "August",
year = "1997",
doi = "10.1021/bi970724w",
issn = "0006-2960",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170919-152344788",
note = "© 1997 American Chemical Society. \n\nReceived March 27, 1997; Revised Manuscript Received May 27, 1997. Publication Date (Web): August 12, 1997. \n\nThis work was supported by the EC BIOMED program (contract\nCT BMH4-CT96-1492) and by Italian CNR (Tecnologie Chimiche\nInnovative; contract 96.00802CT03). \n\nWe thank Peter Güntert for the helpful discussions on the DYANA program.",
revision_no = "12",
abstract = "The solution structure of oxidized horse heart cytochrome c was obtained at pH 7.0 in 100 mM phosphate buffer from 2278 NOEs and 241 pseudocontact shift constraints. The final structure was refined through restrained energy minimization. A 35-member family, with RMSD values with respect to the average structure of 0.70 ± 0.11 Å and 1.21 ± 0.14 Å for the backbone and all heavy atoms, respectively, and with an average penalty function of 130 ± 4.0 kJ/mol and 84 ± 3.7 kJ/mol for NOE and pseudocontact shift constraints, respectively (corresponding to a target function of 0.9 Å^2 and 0.2 Å^2), was obtained. The solution structure is somewhat different from that recently reported (Qi et al., 1996) and appears to be similar to the X-ray structure of the same oxidation state (Bushnell et al., 1990). A noticeable difference is a rotation of 17 ± 8° of the imidazole plane between solid and solution structure. Detailed and accurate structural determinations are important within the frame of the current debate of the structural rearrangements occurring upon oxidation or reduction. From the obtained magnetic susceptibility tensor a separation of the hyperfine shifts into their contact and pseudocontact contributions is derived and compared to that of the analogous isoenzyme from S. cerevisiae and to previous results.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/54431,
title ="Role of the active-site cysteine of Pseudomonas aeruginosa azurin. Crystal structure analysis of the Cu^(II(Cys112Asp) protein",
author = "Faham, Salem and Mizoguchi, Tadashi J.",
journal = "Journal of Biological Inorganic Chemistry",
volume = "2",
number = "4",
pages = "464-469",
month = "August",
year = "1997",
doi = "10.1007/s007750050157 ",
issn = "0949-8257",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150205-135731010",
note = "© 1997 SBIC.\n\nReceived: 30 December 1996; Accepted: 8 May 1997.\n\nWe thank Mike Hill for assistance with several electrochemical experiments, and Xiaotian Zhu, Art Chirino and Barbara Hsu for their help with the crystallographic analysis. S.F. and T.J.M. contributed equally to this work; supported by the NIH (DK19038 to H.B.G., GM16424 to J.H.R., and GM45162 to D.C.R.).",
revision_no = "7",
abstract = "Replacement of the cysteine at position 112 of Pseudomonas aeruginosa azurin with an aspartic acid residue results in a mutant (Cys112Asp) protein that retains a strong copper-binding site. Cu^(II)(Cys112Asp) azurin can be reduced by excess [Ru^(II)(NH_3)_6]^(2+), resulting in a Cu^I protein with an electronic absorption spectrum very similar to that of wild-type Cu^I azurin. Cys112Asp azurin exhibits reversible interprotein electron-transfer reactivity with P. aeruginosa cytochrome c_(551) (μ\u2009=\u20090.1\u2009M sodium phosphate (pH\u20097.0);E°(Cu^(II/I))\u2009=\u2009180 mV vs NHE); this redox activity indicates that electrons can still enter and exit the protein through the partially solvent-exposed imidazole ring of His117. The structure of Cu^(II)(Cys112Asp) azurin at 2.4-Å resolution shows that the active-site copper is five coordinate: the pseudo-square base of the distorted square-pyramidal structure is defined by the imidazole N^δ atoms of His46 and His117 and the oxygen atoms of an asymmetrically-bound bidentate carboxylate group of Asp112; the apical position is occupied by the oxygen atom of the backbone carbonyl group of Gly45. The Cu^(II)–Asp112 interaction is distinguished by an approximately 1.2-Å displacement of the metal center from the plane defined by the Asp112 carboxylate group.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/56855,
title ="Source of Image Contrast in STM Images of Functionalized Alkanes on Graphite:\u2009 A Systematic Functional Group Approach",
author = "Claypool, Christopher L. and Faglioni, Francesco",
journal = "Journal of Physical Chemistry B",
volume = "101",
number = "31",
pages = "5978-5995",
month = "July",
year = "1997",
doi = "10.1021/jp9701799 ",
issn = "1520-6106",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150422-091143996",
note = "© 1997 American Chemical Society.\n\nReceived: January 7, 1997; In Final Form: April 16, 1997.\n\nWe acknowledge the NSF, grants CHE-9634152 (N.S.L.), CHE-9522179 (W.A.G.), CHE-9610164 (H.B.G.), and ASC-9217368 (W.A.G.), for partial support of this work. C.C. acknowledges the NIH for a training grant, and we also acknowledge helpful discussions with Dr. J. Miller of Argonne National Laboratory regarding orbital coupling issues.",
revision_no = "10",
abstract = "A series of functionalized alkanes and/or alkyl alcohols have been prepared and imaged by scanning tunneling microscopy (STM) methods on graphite surfaces. The stability of these ordered overlayers has facilitated reproducible collection of STM images at room temperature with submolecular resolution, in most cases allowing identification of individual hydrogen atoms in the alkane chains, but in all cases allowing identification of molecular length features and other aspects of the image that can be unequivocally related to the presence of functional groups in the various molecules of concern. Functional groups imaged in this study include halides (X = F, Cl, Br, I), amines, alcohols, nitriles, alkenes, alkynes, ethers, thioethers, and disulfides. Except for −Cl and −OH, all of the other functional groups could be distinguished from each other and from −Cl or −OH through an analysis of their STM metrics and image contrast behavior. The dominance of molecular topography in producing the STM images of alkanes and alkanols was established experimentally and also was consistent with quantum chemistry calculations. Unlike the contrast of the methylene regions of the alkyl chains, the STM contrast produced by the various functional groups was not dominated by topographic effects, indicating that variations in local electronic coupling were important in producing the observed STM images of these regions of the molecules. For molecules in which electronic effects overwhelmed topographic effects in determining the image contrast, a simple model is presented to explain the variation in the electronic coupling component that produces the contrast between the various functional groups observed in the STM images. Additionally, the bias dependence of these STM images has been investigated and the contrast vs bias behavior is related to factors involving electron transfer and hole transfer that have been identified as potentially being important in dominating the electronic coupling in molecular electron transfer processes.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/84800,
title ="Solution Structure of Oxidized Saccharomyces cerevisiae Iso-1-cytochrome c",
author = "Banci, Lucia and Bertini, Ivano",
journal = "Biochemistry",
volume = "36",
number = "29",
pages = "8992-9001",
month = "July",
year = "1997",
doi = "10.1021/bi963025c",
issn = "0006-2960",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180213-072130274",
note = "© 1997 American Chemical Society. \n\nReceived 10 December 1996. Published online 22 July 1997. \n\nThis work was supported by EC Biotechnology Program BIO2-\nCT94-2052 (DG 12 SSMA), the Italian CNR, and the United States NSF. \n\nExperiments were performed with the instrumentation of the Florence Laboratory of Relaxometry and Magnetic Resonance on Paramagnetic Metalloproteins, Large Scale Facility of the European Union.",
revision_no = "13",
abstract = "The solution structure of oxidized Saccharomyces cerevisiae Cys102Ser iso-1-cytochrome c has been determined using 1361 meaningful NOEs (of 1676 total) after extending the published proton assignment [Gao, Y., et al. (1990) Biochemistry 29, 6994−7003] to 77% of all proton resonances. The NOE patterns indicate that secondary structure elements are maintained upon oxidation in solution with respect to the solid state and solution structures of the reduced species. Constraints derived from the pseudocontact shifts [diamagnetic reference shift values are those of the reduced protein [Baistrocchi, P., et al. (1996) Biochemistry 35, 13788−13796]] were used in the final stages of structure calculations. After restrained energy minimization with constraints from NOEs and pseudocontact shifts, a family of 20 structures with rmsd values of 0.58 ± 0.08 and 1.05 ± 0.10 Å (relative to the average structure) for the backbone and all heavy atoms, respectively, was obtained. The solution structure is compared with the crystal structure and the structures of related systems. Twenty-six amide protons were detected in the NMR spectrum 6 days after the oxidized lyophilized protein was dissolved in D_2O (pH 7.0 and 303 K); in an analogous experiment, 47 protons were observed in the spectrum of the reduced protein. The decrease in the number of nonexchanging amide protons, which mainly are found in the loop regions 14−26 and 75−82, confirms the greater flexibility of the structure of oxidized cytochrome c in solution. Our finding of increased solvent accessibility in these loop regions is consistent with proposals that an early step in unfolding the oxidized protein is the opening of the 70−85 loop coupled with dissociation of the Met80−iron bond.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/86665,
title ="Spectroscopy and Electrochemistry of Cobalt(III) Schiff Base Complexes",
author = "Böttcher, Arnd and Takeuchi, Toshihiko",
journal = "Inorganic Chemistry",
volume = "36",
number = "12",
pages = "2498-2504",
month = "June",
year = "1997",
doi = "10.1021/ic961146v",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180529-112353490",
note = "© 1997 American Chemical Society. \n\nReceived September 18, 1996. \n\nA.B. thanks the Alexander von Humboldt Foundation for a postdoctoral fellowship. This work was supported by NSF, the Arnold and Mabel Beckman Foundation, and Redox Pharmaceutical Corp.",
revision_no = "11",
abstract = "The structural, spectroscopic, and electrochemical properties of cobalt(III) derivatives of acacen (H_2acacen = bis(acetylacetone) ethylenediimine) and related ligands have been investigated. Electronic structure calculations indicate that the absorption between 340 and 378 nm in Co^(III)(acacen) spectra is attributable to the lowest π−π* intraligand charge-transfer transition. Equatorial ligand substitutions affect reduction potentials less than axial ligand changes, consistent with an electronic structural model in which d_(z^2) is populated in forming cobalt(II). The crystal structure of [Co(3-Cl-acacen)(NH_3)_2]BPh_4 has been determined:\u2009 The compound crystallizes in the monoclinic space group (P2_1)/m (No. 11) with a = 9.720(2) Å, b = 18.142(4) Å, c = 10.046(2) Å, β = 100.11(3)°, D_c = 1.339 g cm^(-3), and Z = 2; the complex cation, [Co(3-Cl-acacen)(NH_3)_2]^+, exhibits a slightly distorted octahedral coordination geometry. The distances between the cobalt atom and the two axial nitrogen donor atoms differ only slightly (1.960(6) and 1.951(6) Å) and are similar to Co−N distances found in cobalt−ammine complexes as well as the axial Co−N distances in [Co(acacen)(4-MeIm)_2]Br·1.5H_2O; the latter compound crystallizes in the triclinic space group P1̄ (No. 2) with a = 18.466(9) Å, b = 14.936(7) Å, c = 10.111(5)Å, α = 96.27(5)°, β = 94.12(5)°, γ = 112.78(5)°, D_c = 1.447 g cm^(-3), and Z = 4.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/86445,
title ="Modification of Heme Peptides by Reverse Proteolysis:\u2009 Spectroscopy of Microperoxidase-10 with C-Terminal Histidine, Tyrosine, and Methionine Residues",
author = "Low, Donald W. and Yang, Grace",
journal = "Journal of the American Chemical Society",
volume = "119",
number = "17",
pages = "4094-4095",
month = "April",
year = "1997",
doi = "10.1021/ja970103q",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180517-161822956",
note = "© 1997 American Chemical Society. \n\nReceived January 15, 1997. Publication Date (Web): April 30, 1997. \n\nWe thank Adrian Ponce for technical assistance and John Dawson for helpful discussions. D.W.L. acknowledges a fellowship from the Parsons Foundation. This work was supported by the NSF.",
revision_no = "13",
abstract = "Small-molecule analogs of the active sites of heme proteins\nare under investigation in many laboratories. Covalent\nattachment of ligands to the porphyrins is often desirable as it reduces complications due to axial ligand dissociation and scrambling in cases involving mixed axial ligation. The preparation of ligand-linked (tailed) porphyrin systems, however, often involves complex multistep syntheses. We have found that trypsin-catalyzed reverse proteolysis provides a simple preparative route to a novel class of water-soluble tailed porphyrins based on the well-characterized microperoxidase (MP) framework. Using reverse proteolysis reactions, we have obtained mutant microperoxidase decapeptides (MP10s) with C-terminal histidine (H23MP10), tyrosine (Y23MP10), and methionine (M23MP10) residues. In addition, we have investigated\nthe electronic absorption and resonance Raman spectra\nof these MP10 mutants.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/985,
title ="Effects of folding on metalloprotein active sites",
author = "Winkler, Jay R. and Wittung-Stafshede, Pernilla",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "94",
number = "9",
pages = "4246-4249",
month = "April",
year = "1997",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:WINpnas97",
note = "© 1997 by the National Academy of Sciences. \n\nContributed by Harry B. Gray, February 28, 1997. \n\nWe thank N. Sutin and E. I. Solomon for helpful comments. This work was supported by the National Science Foundation (MCB9630465), National Institutes of Health (DK19038), and Natural Science Research Council (Sweden). \n\nThe publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked \"advertisement\" in accordance with 18 U.S.C. §1734 solely to indicate this fact.",
revision_no = "10",
abstract = "Experimental data for the unfolding of cytochrome c and azurin by quanidinium chloride (GuHCl) are used to construct free-energy diagrams for the folding of the oxidized and reduced proteins. With cytochrome c, the driving force for folding the reduced protein is larger than that for the oxidized form. Both the oxidized and the reduced folded forms of yeast cytochrome c are less stable than the corresponding states of the horse protein. Due to the covalent attachment of the heme and is fixed tetragonal coordination geometry, cytochrome c folding can be described by a two-state model. A thermodynamic cycle leads to an expression for the difference in self-exchange reorganization energies for the folded and unfolded proteins. The reorganization energy for electron exchange in the folded protein is approximately 0.5 eV smaller than that for a heme in aqueous solution. The finding that reduced azurin unfolds at lower GuHCl concentrations than the oxidized protein suggests that the coordination structure of copper is different in oxidized and reduced unfolded states: it is likely that the geometry of Cu-I in the unfolded protein is linear or trigonal, whereas Cu-II prefers to be tetragonal. The evidence indicates that protein folding lowers the azurin reorganization energy by roughly 1.7 eV relative to an aqueous Cu(1,10-phenanthroline)(2)(2+/+) reference system.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/73673,
title ="Linear-Chain Structures of Platinum(II) Diimine Complexes",
author = "Connick, William B. and Marsh, Richard E.",
journal = "Inorganic Chemistry",
volume = "36",
number = "5",
pages = "913-922",
month = "February",
year = "1997",
doi = "10.1021/ic961232v",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170124-142112656",
note = "© 1997 American Chemical Society. \n\nReceived October 10, 1996; Publication Date (Web): February 26, 1997. \n\nWe thank L. M. Henling and V. M. Miskowski for many helpful discussions and expert technical assistance. This work was supported by the NSF.",
revision_no = "13",
abstract = "The structures of three linear-chain platinum(II) diimine complexes have been determined [Pt···Pt, Å]:\u2009 Pt(bpm)Cl_2·0.5(nmp) (3) [3.411(1), 3.371(1)], Pt(phen)(CN)_2 (6) [3.338(1), 3.332(1)], and Pt(bpy)(NCS)_2 (7) [3.299(2)] (bpm = 2,2‘-bipyrimidine, phen = 1,10-phenanthroline, bpy = 2,2‘-bipyridine, nmp = 1-methyl-2-pyrrolidinone). The Pt···Pt distances in these and in seven related compounds range from 3.24 to 3.49 Å. While we find evidence of interligand interactions influencing these structures, the Pt···Pt bonds are the most important of the stacking forces. The metal−metal distances are generally consistent with an electronic structural model in which σ-donor/π-acceptor ligands strengthen Pt···Pt bonding interactions (for example, the Pt···Pt distances in 3 are 0.04 and 0.08 Å shorter than in the bpy analogue). We have also found that the yellow form of Pt(dmbpy)(NCO)_2 (1b) (4,4‘-dimethyl-2,2‘-bipyridine) has a columnar structure; however, in contrast to the linear-chain form (1), which is orange, the Pt atoms are well separated (>4.9 Å). Interestingly, the yellow form is 7% denser than the orange form; this result is consistent with the concept that directed intermolecular interactions give rise to lower density polymorphs. Crystal data:\u2009 (3) monoclinic, C2/m (No. 12), a = 12.668(4) Å, b = 15.618(6) Å, c = 6.704(3) Å, β = 93.43(3)°, Z = 4; (6) orthorhombic, Pbca (No. 61), a = 38.731(13) Å, b = 18.569(3) Å, c = 6.628(1) Å, Z = 16; (7) orthorhombic, Pbcm (No. 57), a = 10.349(3) Å, b = 19.927(5) Å, c = 6.572(3) Å, Z = 4; (1b) monoclinic, C2/c (No. 15), a = 17.313(4) Å, b = 12.263(3) Å, c = 14.291(4) Å, β = 114.00(2)°, Z = 8.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/86666,
title ="Reversible Nitrogen Atom Transfer between Nitridomanganese(V) and Manganese(III) Schiff-Base Complexes",
author = "Chang, Christopher J. and Low, Donald W.",
journal = "Inorganic Chemistry",
volume = "36",
number = "3",
pages = "270-271",
month = "January",
year = "1997",
doi = "10.1021/ic961023a",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180529-113212317",
note = "© 1997 American Chemical Society. \n\nReceived August 22, 1996. \n\nWe thank John Bercaw, Justin DuBois, and Jay Winkler for helpful discussions and Fred Anson for the loan of a thermostatable cell holder. C.J.C. participated in the Summer Undergraduate Research Fellowship (SURF) program at Caltech during 1995 and 1996. D.W.L. acknowledges a fellowship from the Parsons Foundation. This work was supported by the NSF.",
revision_no = "9",
abstract = "Nitrogen atom transfer from salen-derived nitridomanganese(V) to manganese(III) Schiff-base complexes occurs under aerobic conditions in solution at room temperature. A mechanism involving chloride dissociation followed by the formation and decay of a binuclear μ-nitrido-activated complex accounts satisfactorily for the observed kinetics data.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/57024,
title ="Electrochemistry of the Cu_A domain of Thermus thermophilus cytochrome ba _3",
author = "Immoos, Chad and Hill, Michael G.",
journal = "Journal of Biological Inorganic Chemistry",
volume = "1",
number = "6",
pages = "529-531",
month = "December",
year = "1996",
doi = "10.1007/s007750050088",
issn = "0949-8257",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150427-150735788",
note = "© 1996 SBIC.\n\nReceived: 3 June 1996; Accepted: 26 August 1996.\n\nThis work was supported by the NIH (DK19038 to H.B.G.; GM35342 to J.A.F.; GM16424 to J.H.R.; GM07616 to C.E.S.), the Research Corporation (M.G.H.), the Camille and Henry Dreyfus Foundation (Faculty Start-up Grant to M.G.H.), and the NSF (DUE-9551647).",
revision_no = "11",
abstract = "The electrochemistry of a water-soluble fragment from the Cu_A domain of Thermus thermophilus cytochrome ba _3 has been investigated. At 25\u200a\u200a°C, Cu_A exhibits a reversible reduction at a pyridine-4-aldehydesemicarbazone-modified gold electrode (0.1\u2009M Tris, pH\u20098) with E°\u2009=\u20090.24\u2009V vs NHE. Thermodynamic parameters for the [Cu(Cys)_2Cu]^(+/0) electrode reaction were determined by variable-temperature electrochemistry (ΔS°_(rc)\u2009=\u2009–5.4(12)\u2009eu, ΔS°\u2009=\u2009–21.0(12)\u2009eu, ΔH°\u2009=\u2009–11.9(4)\u2009kcal/mol;ΔG°\u2009=\u2009–5.6 (11)\u2009kcal/mol). The relatively small reaction entropy is consistent with a low reorganization energy for [Cu(Cys)_2Cu]^(+/0) electron transfer. An irreversible oxidation of [Cu(Cys)_2Cu]^+ at 1\u2009V vs NHE confirms that the Cu^(II):Cu^(II) state of Cu_A is significantly destabilized relative to the Cu^(II) state of analogous blue-copper proteins.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/57197,
title ="The Cu_A Center of a Soluble Domain from Thermus Cytochrome ba_3. An NMR Investigation of the Paramagnetic Protein",
author = "Bertini, Ivano and Bren, Kara L.",
journal = "Journal of the American Chemical Society",
volume = "118",
number = "46",
pages = "11658-11659",
month = "November",
year = "1996",
doi = "10.1021/ja9621410",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150504-120953603",
note = "© 1996 American Chemical Society. \n\nReceived June 25, 1996. Publication Date (Web): November 20, 1996. \n\nSupport from NIH (J.A.F., GM 35342; H.B.G., DK 19038; J.H.R., GM 16424) is acknowledged. B.G.M. is grateful to the FLORMARPARM Large Scale Facility of the EU, which supported his stay in Florence. The University of Florence is acknowledged for partially supporting C.E.S. and J.H.R. in Florence. \n\nSupporting Information Available: A 4 ms 2D NOESY spectrum at pH 4.5 and 278 K (2 pages).",
revision_no = "18",
abstract = "The Cu_A center in subunit II of cytochrome c oxidase, the terminal enzyme of aerobic respiration, transfers electrons from cytochrome c to the proton-pumping machinery in subunit I. The unique electronic absorption and EPR spectra of Cu_A exclude it from classification with the well-studied biological copper centers. High-resolution X-ray structures of Cu_A-containing proteins reveal two copper atoms approximately 2.5 Å apart, bridged by two cysteine sulfurs. Each Cu has a terminal histidine ligand and a weak ligand, methionine for one and a main chain carbonyl for the other. These structures are consistent with earlier EPR measurements and theoretical calculations, which predicted a highly delocalized mixed-valence [Cu(II),Cu(I)] Cu_A site. Here we report ^1H NMR measurements at 600 MHz on a soluble Cu_A domain from Thermus thermophilus cytochrome ba_3.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/84790,
title ="Three-Dimensional Solution Structure of Saccharomyces cerevisiae Reduced Iso-l-cytochromec",
author = "Baistrocchi, Paolo and Banci, Lucia",
journal = "Biochemistry",
volume = "35",
number = "43",
pages = "13788-13796",
month = "October",
year = "1996",
doi = "10.1021/bi961110e",
issn = "0006-2960",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180212-114157704",
note = "© 1996 American Chemical Society. \n\nReceived 8 May 1996. Published online 29 October 1996. \n\nThis work was supported by CNR (Italy) and NSF (U.S.A.); it\nwas performed with the instrumentation of the Florence Laboratory of Relaxometry and Magnetic Resonance on Paramagnetic Metalloproteins, Large Scale Facility of the European Community (Contract No. ERBCHGECT940060).",
revision_no = "12",
abstract = "Two-dimensional ^1H NMR spectra of Saccharomyces cerevisiae reduced iso-1-cytochrome c have been used to confirm and slightly extend the assignment available in the literature. 1702 NOESY cross-peaks have been assigned, and their intensities have been measured. Through the program DIANA and related protocols (Güntert, 1992), a solution structure has been obtained by using 1442 meaningful NOEs and 13 hydrogen-bond constraints. The RMSD values with respect to the mean structure for the backbone and all heavy atoms for a family of 20 structures are 0.61 ± 0.09 and 0.98 ± 0.09 Å, the average target function value being as small as 0.57 Å^2. The larger number of slowly exchanging amide NHs observed in this system compared to that observed in the cyanide derivative of oxidized Ala 80 cytochrome c suggests that the oxidized form is much more flexible and that the backbone protons are more solvent accessible. Comparison of the present structure with the crystal structures of reduced yeast cytochrome c and of the complex between cytochrome c peroxidase and oxidized yeast cytochrome c reveals substantial similarity among the backbone conformations but differences in the residues located in the region of protein−protein interaction. Interestingly, in solution the peripheral residues involved in the interaction with cytochrome c peroxidase are on average closer to the position found in the crystal structure of the complex than to the solid state structure of the isolated reduced form.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/52463,
title ="Optical Triggers of Protein Folding",
author = "Chan, Chi-Kin and Hofrichter, James",
journal = "Science",
volume = "274",
number = "5287",
pages = "629-629",
month = "October",
year = "1996",
doi = "10.1126/science.274.5287.628",
issn = "0036-8075",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20141208-101657088",
note = "© 1996 American Association for the Advancement of Science.\n\nReceived 15 August 1996; accepted 10 September 1996.",
revision_no = "13",
abstract = "In our report about the electron-transfer\n(ET)-initiated folding of ferrocytochrome c\n(cyt c^(II)) (1), we noted rapid changes\nin the visible absorption spectrum corresponding to a process with a time constant of\n~40 µs. We indicated that this observation\nwas consistent with studies of cyt c^(ll) folding\ninitiated by CO dissociation where the fast\ndynamics were attributed to changes in heme\nligation (2). We also suggested that these\ndynamics might correspond to the collapse of\nthe protein into a compact denatured state, as\nhas been proposed for apomyoglobinon the\nbasis of laser-temperature-jump measurements\n(3). Our transient absorption data could not\ndistinguish between the two possibilities, and\nthese fast folding dynamics were a relatively\nminor component of the study described in\nour report. Chan et al., with the use of tryptophan (Trp) fluorescence as a probe, found\nno significant collapse of the protein on the\nsubmillisecond time scale following dissociation\nof CO from unfolded cyt c^(II). Clearly,\nmultiples pectroscopic probes must be employed\nto study protein folding; accordingly,\nwe are currently developing time-resolved Trp\nfluorescence as a probe for ET-initiated folding\nof cyt c^(II).",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/73672,
title ="Emission Spectroscopic Properties of the Red Form of Dichloro(2,2‘-bipyridine)platinum(II). Role of Intermolecular Stacking Interactions",
author = "Connick, William B. and Henling, Lawrence M.",
journal = "Inorganic Chemistry",
volume = "35",
number = "21",
pages = "6261-6265",
month = "October",
year = "1996",
doi = "10.1021/ic960511f",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170124-140126469",
note = "© 1996 American Chemical Society. \n\nReceived May 9, 1996; Publication Date (Web): October 9, 1996. \n\nWe thank K. I. Hardcastle, V. M. Miskowski, and V. Schomaker for helpful discussions and expert technical assistance. This work was supported by the NSF.",
revision_no = "13",
abstract = "The structure of the red form of Pt(bpy)Cl_2 (bpy = 2,2‘-bipyridine) has been studied by variable-temperature X-ray crystallography. The stack of square-planar Pt(bpy)Cl_2 units in the linear-chain material contracts with decreasing temperature; in the interval between 294 and 20 K, the platinum−platinum distance shortens from 3.449(1) to 3.370(2) Å. Both absorption and emission spectra of the red compound depend strikingly on temperature; as previously found for tetracyanoplatinate salts, the emission maximum red-shifts as the temperature drops (613 nm at 300 K; 651 nm at 10 K), with the peak energy decreasing linearly with the inverse cube of the metal−metal separation.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/86670,
title ="Spectroelectrochemistry and Dimerization Equilibria of Chloro(terpyridine)platinum(II). Nature of the Reduced Complexes",
author = "Hill, Michael G. and Bailey, James A.",
journal = "Inorganic Chemistry",
volume = "35",
number = "16",
pages = "4585-4590",
month = "July",
year = "1996",
doi = "10.1021/ic960137j",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180529-115403468",
note = "© 1996 American Chemical Society. \n\nReceived February 8, 1996. \n\nJ.A.B. acknowledges an NSERC (Canada) Postdoctoral Fellowship. This work was supported by the National Science Foundation.",
revision_no = "9",
abstract = "[Pt(tpy)Cl]^+ (tpy is 2,2‘:6‘,2‘‘-terpyridine) undergoes reversible one-electron reductions in 0.1 M TBAH/DMF (TBAH is tetrabutylammonium hexafluorophosphate) at E°\u2009‘_(+/0) = −0.74 V and E°\u2009‘_(0/-) = −1.30 V (vs AgCl (1.0 M KCl)/Ag). The first reduction couple is substantially positive of those observed for other M(II)−tpy complexes (for example, E°\u2009‘_(0/-) = −1.36 V for [Zn(tpy)Cl_2]), a finding that suggests there is coupling between the empty 6p_z orbital of square planar Pt(II) and the π* orbital of tpy, stabilizing the (π*)^1 radical state. The dimerization constants of both [Pt(tpy)Cl]^+ and [Pt(tpy)Cl] in 0.1 M TBAH/DMF were determined spectroelectrochemically and found to be 8(1) × 10 and 10(4) × 10 M^(-1), respectively. On the basis of variable-concentration studies, a species observed at an intermediate level of reduction is formulated as the mixed-valence dimer [(Pt(tpy)Cl)_2]^+, with K_(mix) = [(Pt(tpy)Cl)_2^+]/([Pt(tpy)Cl^+][Pt(tpy)Cl]) = 18(4) × 10 M^(-1). Analysis of variable-temperature EPR spectra indicates that the first reduction is ligand-centered (^2B_2) with substantial contributions from Pt(II) 5d_(yz) (4−6%) and 6p_z (3−4%). The second reduction is tentatively assigned as metal-centered; 5d_(x^2 - y^2) is the likely acceptor orbital.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/1394,
title ="Electron Transfer in Proteins",
author = "Gray, Harry B. and Winkler, Jay R.",
journal = "Annual Review of Biochemistry",
volume = "65",
pages = "537-561",
month = "July",
year = "1996",
issn = "0066-4154",
url = "https://resolver.caltech.edu/CaltechAUTHORS:GRAarb96",
note = "\"Reprinted, with permission, from the Annual Review of Biochemistry, Volume 65 copyright 1996 by Annual Reviews, www.annualreviews.org\" \n\nWe thank BG Malmstrom, JN Onuchic, JJ Regan, MJ Therien, and K Warncke for helpful discussions. Our work on protein electron transfer is supported by the National Institutes of Health, the National Science Foundation, and the Arnold and Mabel Beckman Foundation.",
revision_no = "6",
abstract = "Electron-transfer (ET) reactions are key steps in a diverse array of biological transformations ranging from photosynthesis to aerobic respiration. A powerful theoretical formalism has been developed that describes ET rates in terms of two parameters: the nuclear reorganization [lambda] energy (1) and the electronic-coupling strength (HAB). Studies of ET reactions in ruthenium-modified proteins have probed [lambda] and HAB in several metalloproteins (cytochrome c, myoglobin, azurin). This work has shown that protein reorganization energies are sensitive to the medium surrounding the redox sites and that an aqueous environment, in particular, leads to large reorganization energies. Analyses of electronic-coupling strengths suggest that the efficiency of long-range ET depends on the protein secondary structure: [beta]sheets appear to mediate coupling more efficiently than [alpha]-helical structures, and hydrogen bonds play a critical role in both.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/56984,
title ="Electronic Spectroscopy of Gold(I) Pseudomonasaeruginosa Azurin Derivatives",
author = "McCleskey, T. Mark and Mizoguchi, Tadashi J.",
journal = "Inorganic Chemistry",
volume = "35",
number = "11",
pages = "3434-3435",
month = "May",
year = "1996",
doi = "10.1021/ic951055i",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150424-155400474",
note = "© 1996 American Chemical Society. \n\nReceived August 9, 1995. \n\nWe thank Angelo Di Bilio, Bo Malmström, Vinny Miskowski, and Jay Winkler for helpful discussions. This work was supported by the National Institutes of Health (DK19038).",
revision_no = "12",
abstract = "The trigonal (His_2Cys) coordination of blue copper sites in proteins favors Cu(I) over Cu(II), as reflected in the relatively high Cu^(II/I) reduction potentials; and the rigid polypeptide environment minimizes Cu^(II/I) nuclear reorganization, thereby facilitating long-range electron-transfer reactions with donor and acceptor molecules. Although blue Cu(II) sites exhibit rich spectroscopic and magnetic properties, the corresponding Cu(I) proteins do not; indeed, the methods that can be employed to investigate d^(10) metal sites are very limited. Because recent work has shown that Au(I) has geometry-sensitive d-p absorptions and emissions, we are using this 5d^(10) ion to probe ligand interactions in the Cu(I) sites of proteins. Here we report the electronic spectroscopy of Au(I)-substituted wild-type (WT) Pseudomonas aeruginosa azurin as well as the Au(I) derivative of a mutant in which the methionine at position 121 has been replaced with glycine (Met121Gly).",
}
@book_section {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/85673,
title ="Donor—Acceptor Electronic Coupling in Ruthenium-Modified Heme Proteins",
author = "Casimiro, Danilo R. and Beratan, David N.",
number = "246",
pages = "471-485",
month = "May",
year = "1996",
doi = "10.1021/ba-1995-0246.ch018",
issn = "0065-2393",
isbn = "9780841230620",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180406-080326896",
note = "© 1995 American Chemical Society. \n\nReceived for review July 19, 1993. Accepted revised manuscript December 10, 1993. Published in print 5 May 1996. \n\nWe thank A. Kuki and R. A. Marcus for preprints of references 13 and 43, respectively. This research was supported by the National Science Foundation, the National Institutes of Health, the Department of Energy, and the Arnold and Mabel Beckman Foundation.",
revision_no = "10",
abstract = "The rates of electron transfer (ET) in six Ru-modified cytochrome c derivatives were analyzed in terms of four theoretical models describing donor-acceptor electronic coupling. The simplest model, which treats the protein as a homogeneous medium, fails to describe the variations in ET rates with changes in donor-acceptor separation. The three other models explicitly account for the inhomogeneity of the polypeptide matrix and are more successful in describing the electronic couplings. Calculations of relative coupling strengths give results within an order of magnitude of experimentally determined values for cytochrome c. The homogeneousmedium model is more successful in describing ET in Ru-modified myoglobin, and two of the inhomogeneous-medium models suggest that multiple pathways are important in mediating the electronic coupling.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/57199,
title ="Water-Soluble, Recombinant Cu_A-Domain of the Cytochrome ba_3 Subunit II from Thermus thermophilus",
author = "Slutter, Claire E. and Sanders, Donita",
journal = "Biochemistry",
volume = "35",
number = "11",
pages = "3387-3395",
month = "March",
year = "1996",
doi = "10.1021/bi9525839",
issn = "0006-2960",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150504-122517025",
note = "© 1996 American Chemical Society. \n\nReceived October 31, 1995; Revised Manuscript Received January 16, 1996. \n\nThis work was supported by NIH Grants GM35342 (J.A.F.), GM16424 (J.H.R.), and DK19038 (H.B.G.), predoctoral training Grant GM07616 (C.E.S.), and the Swedish Natural Science Research Council (B.G.M.). \n\nWe are grateful for the following assistance:\u2009 The synthesis of PCR probes was done by Dr. Nicole Levy of the Biopolymer Synthesis and Analysis Resource Center at CalTech. The electrospray mass spectrometry was carried out by Dr. Gary Suizdak in the Mass Spectroscopy Facility at the Scripps Research Institute with support from the Lucille P. Markey Charitable Trust and a NIH Shared Instrumentation Grant RR07273-01. Dr. Andrew Thomson provided a manuscript prior to publication. Dr. Matthias Wilmanns provided structural coordinates of CyoA prior to publication. Dr. David B. Goodin recorded some of the EPR spectra and provided essential advice on obtaining the mass spectra. Dr. Andresz Pastuszyn carried out the quantitative amino acid analyses and the N-terminal amino acid sequencing. Mr. Ron LaBorde carried out the ICP-MS analyses. Mr. Patrik Pettersson carried out the TXRF analyses. Mr. Harold Kochounian carried out the DNA sequencing. Dr. Stephen Mayo and Mr. J. Luo assisted with obtaining the CD data. Portions of this work were done while J.A.F. was a Visiting Scientist at Göteborgs Universitet in April 1995, and he thanks T.V., R.A., and B.G.M. for their generous hospitality during that time.",
revision_no = "11",
abstract = "Recently, the genes of cytochrome ba_3 from Thermus thermophilus [Keightley, J. A., et al. (1995) J. Biol. Chem. 270, 20345−20358], a homolog of the heme-copper oxidase family, have been cloned. We report here expression of a truncated gene, encoding the copper A (Cu_A) domain of cytochrome ba_3, that is regulated by a T7 RNA polymerase promoter in Escherichia coli. The Cu_A-containing domain is purified in high yields as a water-soluble, thermostable, purple-colored protein. Copper analysis by chemical assay, mass spectrometry, X-ray fluorescence, and EPR spin quantification show that this protein contains two copper ions bound in a mixed-valence state, indicating that the Cu_A site in cytochrome ba_3 is a binuclear center. The absorption spectrum of the Cu_A site, free of the heme interference in cytochrome ba_3, is similar to the spectra of other soluble fragments from the aa_3-type oxidase of Paracoccus denitrificans [Lappalainen, P., et al. (1993) J. Biol. Chem. 268, 26416−26421] and the caa_3-type oxidase of Bacillus subtilis [von Wachenfeldt, C., et al. (1994) FEBS Lett. 340, 109−113]. There are intense bands at 480 nm (3100 M^(-1) cm^(-1)) and 530 nm (3200 M^(-1) cm^(-1)), a band in the near-IR centered at 790 nm (1900 M^(-1) cm^(-1)), and a weaker band at 363 nm (1300 M^(-1) cm^(-1)). The visible CD spectrum shows a positive-going band at 460 nm and a negative-going band at 527 nm, the opposite signs of which may result from the binuclear nature of the site. The secondary structure prediction from the far-UV CD spectrum indicates that this domain is predominantly β-sheet, in agreement with the recent X-ray structure reported for the complete P. denitrificans cytochrome aa_3 molecule [Iwata, S., et al. (1995) Nature 376, 660−669] and the engineered, purple CyoA protein [Wilmanns, M., et al. (1996) Proc. Natl. Acad. Sci. U.S.A. 92, 11955−11959]. However, the thermostability of the fragment described here (T_m ≈ 80 °C) and the stable binding of copper over a broad pH range (pH 3−9) suggest this protein may be uniquely suitable for detailed physical-chemical study.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/53902,
title ="Protein Folding Triggered by Electron Transfer",
author = "Pascher, Torbjörn and Chesick, John P.",
journal = "Science",
volume = "271",
number = "5255",
pages = "1558-1560",
month = "March",
year = "1996",
doi = "10.1126/science.271.5255.1558",
issn = "0036-8075",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150120-160536302",
note = "© 1996 American Association for the Advancement of Science.\n\n5 December 1995; Accepted 29 January 1996.\n\nWe thank G. Mines and S. Lee for technical assistance, M. Gruebele for a preprint of his paper on apomyoglobin, and P. Wolynes for helpful discussions. Supported by the Swedish Natural Science Research Council (T.P.), NIH, NSF, and the Arnold and Mabel Beckman Foundation.",
revision_no = "11",
abstract = "Rapid photochemical electron injection into unfolded ferricytochrome c titrated with 2.3 to 4.6 M guanidine hydrochloride (GuHCl) at pH 7 and 40°C produced unfolded ferrocytochrome, which then converted to the folded protein. Two folding phases were observed: a fast process with a time constant of 40 microseconds (4.6 M GuHCl), and a slower phase with a rate constant of 90 ± 20 per second (2.3 M GuHCl). The activation free energy for the slow step varied linearly with GuHCl concentration; the rate constant, extrapolated to aqueous solution, was 7600 per second. Electron-transfer methods can bridge the nanosecond to millisecond measurement time gap for protein folding.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/86482,
title ="Transition Metal Diazoalkane Complexes. Synthesis, Structure, and Photochemistry of Rh[C(N_2)SiMe_3](PEt_3)_3",
author = "Deydier, Eric and Menu, Marie-Joëlle",
journal = "Organometallics",
volume = "15",
number = "4",
pages = "1166-1175",
month = "February",
year = "1996",
doi = "10.1021/om950490h",
issn = "0276-7333",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180518-163458007",
note = "© 1996 American Chemical Society. \n\nReceived June 26, 1995. \n\nM.J.M thanks the Ministère des Affaires Etrangères, the Ministère de l'Education du Québec (Projet Intégré FranceQuébec), and the Université de Montréal (Canada) for financial support (postdoctoral fellowship). This work was made possible by travel grants in the framework of the NATO Research Program for International Cooperation between M.D. and H.B.G. (890109). Material support through the Centre National de la Recherche Scientifique, the Université P. Sabatier, and the Natural Sciences and Engineering Reseach Council of Canada is also gratefully acknowledged. Research at Caltech was supported by the National Science Foundation. Contribution 8773 from the Division of Chemistry and Chemical Engineering, California Institute of Technology.",
revision_no = "11",
abstract = "Reaction of RhCl(PR_3)_n (R = Me (n = 4), Et (n = 3)) and RhCl(CO)(PEt_3)_2 with (trimethylsilyl)diazomethyl lithium at −78 °C in ether yields the three complexes Rh[C(N_2)SiMe_3](PEt_3)_3 (1), Rh[C(N_2)SiMe_3](PMe_3)_4 (2), and Rh[C(N_2)SiMe_3](CO)(PEt_3)_2 (3). 2 could not be isolated as a solid at room temperature but 1 was precipitated as red crystals that were stable enough to be handled under argon. X-ray work on 1 reveals a tetrahedrally distorted square-planar geometry with the planar (trimethylsilyl)diazomethyl ligand roughly perpendicular to the P3RhC coordination plane. This distortion makes the PEt3 ligands nonequivalent in the crystal and produces an ABB‘X pattern in the solid-state ^(31)P NMR spectrum. Photolysis of Rh[C(N_2)SiMe_3](PEt_3)_3 leads quantitatively to the dimer [Rh{C(SiMe_3)(PEt_3)}(PEt_3)_2]_2 (4). The presence of the two ylide bridges and terminal phosphines is deduced from the COSY ^(31)P−^(31)P NMR spectrum. This photochemical reactivity suggests that the transient carbene (PEt_3)_3RhC̈(SiMe_3) is electrophilic, which is typical of a singlet carbene. We believe the singlet state is stabilized by the presence of the electron-rich low-spin Rh(PEt3)3 fragment. Reaction with ^nBuNC and ^tBuNC leads to stereo- and regioselective formation of a triazole that is σ bonded to the rhodium center. The X-ray structure of the ^tBuNC derivative Rh[CC(SiMe_3)N_2N^tBu](^tBuNC)_2(PEt_3) (5) shows a distorted square-planar geometry around Rh with the planar triazolato ligand roughly orthogonal to this plane. The probable reaction mechanism involves addition and substitution reactions of isocyanides at Rh followed by insertion into the Rh−C bond.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/86636,
title ="Structures of [M_2(dimen)_4](Y)_2 (M = Rh, Ir; dimen = 1,8-Diisocyanomenthane; Y = PF_6, Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, B(C_6H_5)_4) Crystals Featuring an Exceptionally Wide Range of Metal−Metal Distances and Dihedral Twist Angles",
author = "Exstrom, Christopher L. and Britton, Doyle",
journal = "Inorganic Chemistry",
volume = "35",
number = "3",
pages = "549-550",
month = "January",
year = "1996",
doi = "10.1021/ic9508637",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180525-134636164",
note = "© 1996 American Chemical Society. \n\nReceived July 7, 1995. \n\nWork at the University of Minnesota and the California Institute of Technology was supported by the National Science Foundation. We thank Johnson Matthey for generous loans of rhodium trichloride and iridium trichloride.",
revision_no = "20",
abstract = "The binuclear complexes [M_2(dimen)_4](Y)_2 (M = Rh, Ir; dimen = 1,8-diisocyanomenthane; Y = PF_6, tetrakis[3,5-bis(trifluoromethyl)phenyl]borate), and B(C_6H_5)_4) have face-to-face structures with M−M distances between 3.60 and 4.48 Å, and square-planar unit twist angles between 0 and 17.2°. Ligand flexing and out-of-plane bending of the metal centers accommodate M−M distances longer than 3.9 Å; addition of a torsional deformation produces a twisted conformation for shorter M−M distances (<3.9 Å). Spectroscopic data indicate that there are two or more deformational isomers of Ir_2(dimen)_4^(2+) in solution.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/982,
title ="The currents of life: The terminal electron-transfer complex of respiration",
author = "Ramirez, Benjamin E. and Malmström, Bo G.",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "92",
number = "26",
pages = "11949-11951",
month = "December",
year = "1995",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:RAMpnas95",
note = "© 1995 by the National Academy of Sciences. \n\nOur work is supported by the National Institutes of Health, the National Science Foundation, and the Swedish Natural Science Research Council.",
revision_no = "8",
abstract = "Aerobic organisms derive most of the energy needed for life processes by the burning of foodstuffs with the molecular oxygen in air, as first suggested in 1789 (1) by Antoine Lavoisier (1743-1794). In the first part of the respiratory process, hydrogen atoms are extracted from organic molecules. The hydrogen carriers are later regenerated in the respiratory chain located in cell organelles, mitochondria, or, in bacteria, in the cell membrane. These chains consist of a series of membrane-bound protein complexes in which the hydrogen atoms are split into protons and electrons. The electrons are passed down the chain and reduce molecular oxygen to water, whereas the protons are left behind on one specific side of the membrane. In addition, the electron transfer (ET) or \"current\" through the chain is coupled to a pumping of additional protons from water to the same membrane side. Thus, the two proton currents lead to an increased positive charge and decreased pH on this side-i.e., an electrochemical potential across the membrane, analogous to a storage battery. This potential drives the synthesis of ATP, the universal energy currency in living cells, by a chemiosmotic mechanism formulated by Peter Mitchell (2), who was awarded the Nobel Prize in Chemistry in 1978.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/84680,
title ="Three-Dimensional Solution Structure of the Cyanide Adduct of a Variant of Saccharomyces cerevisiae Iso-1-cytochrome c Containing the Met80Ala Mutation. Identification of Ligand-Residue Interactions in the Distal Heme Cavity",
author = "Banci, Lucia and Bertini, Ivano",
journal = "Biochemistry",
volume = "34",
number = "36",
pages = "11385-11398",
month = "September",
year = "1995",
doi = "10.1021/bi00036a011",
issn = "0006-2960",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180206-065819564",
note = "© 1995 American Chemical Society. \n\nPublished in print 12 September 1995. \n\nWe thank Yi Lu for helpful discussions. K.L.B. acknowledges\na Kodak graduate fellowship. P.S. acknowledges the Italian Ministry of Foreign Affairs for a Ph.D. grant. This work was supported by the EC Biotechnology Program BI02-CT94-2052 (DG12SSMA), the CNR (Italy), and the National Science Foundation (United States). This work has been performed with the instrumentation of the Florence Laboratory of Relaxometry and Magnetic Resonance on Paramagnetic Metalloproteins, Large Scale Facility of the European Community.",
revision_no = "12",
abstract = "The ^1H NMR spectrum of the the cyanide adduct of a triply mutated Saccharomyces cerevisiae iso-1-cytochrome c (His39Gln/Met80Ala/CyslO2Seri)n the oxidized form has been assigned through 1D NOE and 2D COSY, TOCSY, NOESY, and NOE-NOESY experiments; 562 protons out of a total of 683 have been assigned. The solution structure, the first of a paramagnetic heme protein, was determined using 1426 meaningful NOE constraints out of a total of 1842 measured NOES. The RMSD values at the stage of restrained energy minimization of 17 structures obtained from distance geometry calculations are 0.68 ± 0.11 and 1.32 ± 0.14 Å for the backbone and all heavy atoms, respectively. The quality, in terms of RMSD, of the present structure is the same as that obtained for the solution structure of the diamagnetic horse heart ferrocytochrome c [Qi, P. X., et al. (1994) Biochemistry 33, 6408-64191. The secondary\nstructure elements and the overall folding in the variant are observed to be the same as those of the wild-type protein for which the X-ray structure is available. However, the replacement of the methionine axial ligand with an alanine residue creates a ligand-binding “distal cavity.” The properties of the distal cavity seen in this solution structure are compared to those of other heme proteins.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/73655,
title ="Electronic Spectroscopy of Chloro(terpyridine)platinum(II)",
author = "Bailey, James A. and Hill, Michael G.",
journal = "Inorganic Chemistry",
volume = "34",
number = "18",
pages = "4591-4599",
month = "August",
year = "1995",
doi = "10.1021/ic00122a015",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170124-084350725",
note = "© 1995 American Chemical Society. \n\nWe thank C.-M. Che, N. S. Lewis, and G. R. Rossman for experimental assistance and helpful discussions. This work was supported by the National Science Foundation and the Office of Naval Research.",
revision_no = "15",
abstract = "The electronic spectrum of [Pt(tpy)Cl]^+ (tpy = 2,2':6',2\"-terpyridine) is influenced dramatically by intermolecular stacking interactions in solution and in the solid state. The crystal structure of [Pt(tpy)Cl]ClO_4 (monoclinic, P2_1/c (No. 14); a = 7.085(2), b = 17.064(5), c = 26.905(8) Å; β = 90.0(1) °; Z = 8) consists of discrete Pt_2 units (Pt-Pt = 3.269(1) Å) arranged along an infinite tpy-π stack (spacing ~ 3.35 Å). Variable-temperature and\nconcentration studies of the absorption and emission spectra of [Pt(tpy)Cl]^+ suggest that similar metal-metal\nand ligand-ligand interactions persist in the solution phase. The high concentration, low-temperature emission\nspectrum (5:5:1 ethanol:methanol:DMF) reveals a 740-nm band indicative of M-M oligomerization, a 650-nm band attributable to tpy π-π interactions, and a 470-nm band characteristic of mononuclear [Pt(tpy)Cl]^+ π-π*\nemission. Concentration-dependent absorption spectra were fit to a \"two-dimer\" model, yielding equilibrium\nconstants for the formation of Pt-Pt-, and tpy-tpy-bound dimers of 1.3(1) x 10^3 and 1.0(1) x 10^3 M^(-1), respectively, in 0.1 M aqueous NaCl. The low temperature solid-state luminescence of [Pt(tpy)Cl]^+ is assigned to a ^3(MMLCT) (MMLCT = metal-metal-to-ligand charge transfer) transition. The energy of this band is highly dependent on the counterion (PF_6^-, ClO_4^- , C1^-, CF_3SO_3^-), in line with the different colors of these various salts. In contrast, the room-temperature solid-state emission spectra are more difficult to interpret. While the red perchlorate salt exhibits a relatively narrow emission band at 725 nm (red-shifted from the 77-K maximum at 695 nm), consistent\nwith a 3(MMLCT) transition, the orange (Cl^-, ClO_4^-, CF_3SO_3^-) and yellow (PF6^-) salts have extremely broad\nroom-temperature emission bands that all appear at nearly the same energy (λ_(max) ~ 640 nm). We assign this\nluminescence to an eximeric intraligand transition resulting from π- π interactions and propose that the temperature dependent emissions from the orange and yellow solid materials originate from multiple electronic states.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/53841,
title ="Electron Tunneling in Proteins: Coupling Through a β Strand",
author = "Langen, Ralf and Chang, I-Jy",
journal = "Science",
volume = "268",
number = "5218",
pages = "1733-1735",
month = "June",
year = "1995",
doi = "10.1126/science.7792598 ",
issn = "0036-8075",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150116-145929070",
note = "© 1995 American Association for the Advancement of Science.\n\n17 January 1995; accepted 23 March 1995.\n\nWe thank D. R. Casimiro, K. Warncke, J. J. Regan, and J. N. Onuchic for helpful comments. Supported by NIH and NSF.",
revision_no = "11",
abstract = "Electron coupling through a beta strand has been investigated by measurement of the intramolecular electron-transfer (ET) rates in ruthenium-modified derivatives of the beta barrel blue copper protein Pseudomonas aeruginosa azurin. Surface histidines, introduced on the methionine-121 beta strand by mutagenesis, were modified with a Ru(2,2'-bipyridine)2(imidazole)^2+ complex. The Cu+ to Ru^3+ rate constants yielded a distance-decay constant of 1.1 per angstrom, a value close to the distance-decay constant of 1.0 per angstrom predicted for electron tunneling through an idealized beta strand. Activationless ET rate constants in combination with a tunneling-pathway analysis of the structures of azurin and cytochrome c confirm that there is a generally efficient network for coupling the internal (native) redox center to the surface of both proteins.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/57238,
title ="Paramagnetic NMR spectroscopy and coordination structure of cobalt(II) Cys112Asp azurin",
author = "Piccioli, Mario and Luchinat, Claudio",
journal = "Inorganic Chemistry",
volume = "34",
number = "3",
pages = "737-742",
month = "February",
year = "1995",
doi = "10.1021/ic00107a027",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150505-131303284",
note = "© 1995 American Chemical Society.\n\nReceived October 6, 1994.\n\nWe thank Ivano Bertini for many helpful discussions. This work was supported by the National Institutes of Health.",
revision_no = "10",
abstract = "Paramagnetic ^1H-NMR spectra of Co(II)-substituted Cys112Asp azurin from Pseudomonas aeruginosa have been\nanalyzed and compared with those of the Co(II) wild-type (WT) protein. Hyperfine-shifted signals (including\nAsp112 β-CH_2 signals in the mutant as well as previously unobserved Cys112 β-CH_2 signals in WT) from all the\nmetal-coordinated residues have been detected and unambiguously assigned. Notably, the spectra indicate that\nvery little if any unpaired spin density is located on the Met121 protons in the Cys112Asp protein. A computer-generated\nmodel of the mutant Co(II) structure consistent with electronic absorption as well as the NMR data\nincludes a Gly45 carbonyl, His46, an unusually coordinated Asp112, and His117 in the ligation sphere.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/86762,
title ="Mononuclear and Binuclear Palladium(II)/Rhenium(I) Complexes Containing a Sterically Hindered Trinucleating Ligand: 2,3,8,9,14,15-Hexamethyl-5,6,11,12,17,18-hexaazatrinaphthalene (hhtn)",
author = "Catalano, Vincent J. and Larson, Wayne E.",
journal = "Inorganic Chemistry",
volume = "33",
number = "20",
pages = "4502-4509",
month = "September",
year = "1994",
doi = "10.1021/ic00098a016",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180601-154849530",
note = "© 1994 American Chemical Society. \n\nReceived March 2, 1994. \n\nWe thank Mike Hill for assistance with the electrochemistry. This work was supported by the National Science Foundation (Grant CHE-9311587 to H.B.G.; postdoctoral fellowship CHE-9101931 to V.J.C.).",
revision_no = "11",
abstract = "The trinucleating ligand 2,3,8,9,14,15-hexamethyl-5,6,11,12,17,18-hexaazatrinaphthalene (hhtn), 1, has been\nobtained in an efficient one-pot synthesis. The reaction of a yellow-green solution of 1 with 1 equiv of Pd-(NCPh)_2Cl_2 gives orange PdCl_2(hhtn), 2, which crystallizes with two independent PdCl_2(hhtn) molecules, a molecule of chlorobenzene, and two molecules of methanol in the triclinic space group P1 with a = 12.949(3) Å, b = 16.625(4) Å, c = 17.062(4) Å, α = 63.00(2)°, β = 71.39(2)°, and γ = 79.78(2)° at 130 K with Z = 4. Refinement of 5551 reflections and 387 parameters yielded R = 0.059 and R_w = 0.060. The structure consists of a nearly square planar PdCl_2(N_2) complex in a highly-distorted hhtn framework. Unfavorable Cl•••H interactions force the PdCl_2 unit out of the hhtn plane by 28.1°. The structure indicates that there are π-π (ligand-ligand) interactions. Reaction of 2 with another equivalent of Pd(NCPh)_2Cl_2 produces the binuclear species (PdCl_2)_2(hhtn), 5. Addition of Re(CO)_5Cl to 1 in refluxing toluene affords deep red crystals of fac-Re(CO)_3Cl(hhtn), 3. Dark red needles of Re(CO)_3Cl(hhtn)•CH_3OH form in the monoclinic space group P2/n with a = 10.515(2) Å, b = 27.123(6) Å, c = 11.385(2) Å, and β = 110.95(2)° at 130 K with Z = 4. Refinement of 5451 reflections and 415 parameters yielded R = 0.052 and R_w = 0.052. The structure features a nearly octahedral Re center that is deflected from the hhtn plane by 19.5°. The hhtn in 3 is less distorted than in 2. Reaction of a dichloromethane solution of 3 with 1 equiv of Pd(NCPh)_2Cl_2 produces the heterobinuclear (Re(CO)_3Cl)(PdCl_2)(hhtn), 4 . Red-brown blocks of 4 cocrystallize with 2.6 molecules of 1,2-dichlorobenzene in the triclinic space group P1 with a = 14.540(4) Å, b = 14.558(3) Å, c = 14.671(4) Å, α = 64.72(2)°, β = 66.00(2)°, and γ = 63.30(2)° at 130 K with Z = 2. Refinement based on full-matrix least squares on F^2 using 8481 reflections and 513 parameters yielded R = 0.061 and R2 = 0.135. The structure includes a nearly octahedral Re and a square planar Pd coordinated to a highly distorted hhtn ligand. The PdCl_2 fragment is bent out of the ligand plane by 40.2°, whereas the Re unit is distorted by only 10.4°. Complex 4 forms π-π stacks exclusively with the 1,2-dichlorobenzene solvate molecules.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/86595,
title ="(Bipyridyl-N,N')diiodoplatinum(II)",
author = "Connick, William B. and Gray, Harry B.",
journal = "Acta Crystallographica Section C",
volume = "C50",
number = "7",
pages = "1040-1042",
month = "July",
year = "1994",
doi = "10.1107/S0108270193012648",
issn = "0108-2701",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180524-150509080",
note = "© 1994 International Union of Crystallography. \n\n(Received 20 July 1993; accepted 11 November 1993) \n\nWe thank L. M. Henling, R. E. Marsh, V. M. Miskowski and W. P. Schaefer for expert assistance and helpful discussions. This work was supported by the National Science Foundation and the Office of Naval Research.",
revision_no = "12",
abstract = "Square-planar (bipyridyl-N,N')diiodoplatinum(II), [PtI_2(C_(10)H_8N_2)], has normal Pt--N(bipyridyl) [2.029 (7) Å] and Pt--I bonds [2.589 (2) Å]. The bipyridyl ligand exhibits normal distances and angles. Because of steric effects, the intramolecular I...I separation [3.587 (1) Å] and the corresponding I--Pt--I angle [87.7 (1)°] are significantly smaller than those observed for other cis-bis(iodo)bis(N-donor) complexes. The parallel square-planar units stack to form a chain structure. Relative lateral displacement of consecutive molecules along a chain results in a Pt..-Pt distance [5.291 (1) Å] considerably longer than the interplanar spacing [3.510 (11) Å].",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/52532,
title ="Mechanism of catalytic oxygenation of alkanes by halogenated iron porphyrins",
author = "Grinstaff, Mark W. and Hill, Michael G.",
journal = "Science",
volume = "264",
number = "5163",
pages = "1311-1313",
month = "May",
year = "1994",
doi = "10.1126/science.8191283 ",
issn = "0036-8075",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20141210-090711278",
note = "© 1994 American Association for the Advancement of Science.\n\nReceived 28 December 1993; accepted 1 April 1994.\n\nWe thank J. E. Lyons, P. E. Ellis, W. P. Schaefer, E.\nR. Birnbaum, and T. Takeuchi for helpful discussions.\nSupported by the U.S. Department of Energy,\nMorgantown Energy Technology Center,\nand the Sun Company. M.W.G. acknowledges an\nNIH postdoctoral fellowship.",
revision_no = "12",
abstract = "Halogenation of an iron porphyrin causes severe saddling of the macrocyclic structure and a large positive shift in the iron(III)/(II) redox couple. Although pre-halogenated iron(II) porphyrins such as Fe(TFPPBr_8) [H2TFPPBr_8, β-octabromo-tetrakis(pentafluorophenyl)-porphyrin] are relatively resistant to autoxidation, they rapidly reduce alkyl hydroperoxides. These and related reactivity studies suggest that catalysis of alkane oxygenation by Fe(TFPPBr_8)Cl occurs through a radical-chain mechanism in which the radicals are generated by oxidation and reduction of alkyl hydroperoxides.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/86693,
title ="Photoinduced Electron Transfer in Iridium(spacer)pyridinium Complexes",
author = "Farid, Ramy S. and Chang, I-Jy",
journal = "Journal of Physical Chemistry",
volume = "98",
number = "20",
pages = "5176-5179",
month = "May",
year = "1994",
doi = "10.1021/j100071a001",
issn = "0022-3654",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180529-161428891",
note = "© 1994 American Chemical Society. \n\nReceived: December 17, 1993; In Final Form: March 30, 1994. \n\nResearch at the California Institute of Technology was supported by NSF Grants CHE-8922067 and CHE-9311587. Research carried out at Brookhaven National Laboratory was under contract DE-AC02-76CH00016 with the US. Department of Energy and supported by its Division of Chemical Sciences, Office of Basic Research. R.S.F. thanks the US. Department of Education for a graduate fellowship.",
revision_no = "11",
abstract = "Photoinduced electron-transfer (ET) reactions in a series of iridium(spacer)pyridinium complexes, [Ir(µ-pz*)-(CO)Ph_2POC_6H_4(CH_2)_n-A^+]_2 (pz* = 3,5-dimethylpyrazolyI; Ph = C_6H_5; C_6H_4 = phenylene; A^+ = pyridinium (py^+) or substituted py^+; n = 0-3), have been studied in acetonitrile solution at room temperature. The rates\nof singlet (^1Irz* → A^+: ^1ET) reactions were determined for each complex, and for n = 1 and 2 species, the rates of thermal charge recombination (ET^b) also were measured. The ET rates for the n = 1 system display a Gaussian free-energy dependence ( λ = 1.0 eV, H_(AB) = 5 cm^(-1)). With one exception, maximum ET rates exhibit an exponential dependence upon the number of carbon atoms (α_c) in the spacer. The exception is the n = 1 (α_c = 5) system; k_(max) is almost a factor of 100 slower than predicted by the exponential dependence on α_c, indicating that donor-acceptor electronic coupling through a single methylene link is unusually weak.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/86685,
title ="Environment of the Heme in Myoglobins. NMRD and EPR Spectroscopy of Val68X (X = Asn, Asp, and Glu) Mutants of Human Myoglobin",
author = "Zewert, Thomas E. and Gray, Harry B.",
journal = "Journal of the American Chemical Society",
volume = "116",
number = "4",
pages = "1169-1173",
month = "February",
year = "1994",
doi = "10.1021/ja00083a001",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180529-152346680",
note = "© 1994 American Chemical Society. \n\nReceived August 23, 1993. \n\nWe thank Seymour Koenig and Rodney Brown of the IBM Thomas J. Watson Research Center for allowing us access to their facilities and for assistance with many of the experiments. During the course of the work, we enjoyed several discussions with Claudio Luchinat, Lucia Banci, and Paul Smith. Research at Caltech was supported by the National Science Foundation, the National Institutes of Health, and the Arnold and Mabel Beckman Foundation.",
revision_no = "9",
abstract = "Analyses of the temperature dependences and shapes of nuclear magnetic relaxation dispersion (NMRD) signals of site-directed mutants of human myoglobin indicate that a water molecule is bound to the sixth coordination site of the ferric heme in proteins in which the valine at position 68 is changed to either aspartate (Val68Asp) or asparagine (Val68Asn). Both NMRD data and electron paramagetic resonance (EPR) spectra show that carboxylate is axially ligated to Fe(III) in the Va168Glu mutant. The EPR spectra of the Va168Asp and Va168Asn derivatives show much smaller rhombic splittings than the spectrum of the Va168Glu protein.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/86684,
title ="Pressure Effects on the Rates of Intramolecular Electron Transfer in Ruthenium-Modified Cytochrome c. Role of the Intervening Medium in Tuning Distant Fe^(2+):Ru^(3+) Electronic Couplings",
author = "Meier, Martin and van Eldik, Rudi",
journal = "Journal of the American Chemical Society",
volume = "116",
number = "4",
pages = "1577-1578",
month = "February",
year = "1994",
doi = "10.1021/ja00083a056",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180529-151821595",
note = "© 1994 American Chemical Society. \n\nReceived October 18, 1993. Revised Manuscript Received December 30, 1993. \n\nWe thank David Beratan, Danny Casimiro, Rudy Marcus, Jost Onuchic, and Prabha Siddarth for helpful discussions. This work was supported by the Deutsche Forschungsgemeinschaft, the Volkswagen Foundation, the National Science Foundation, the National Institutes of Health, and the Arnold and Mabel Beckman Foundation. Fellowships from the NSF (G.A.M., D.S.W.) and the Parsons Foundation (D.S.W.) are acknowledged.",
revision_no = "11",
abstract = "[no abstract]",
}
@book {CaltechBOOK_https://authors.library.caltech.edu/id/eprint/25052,
title ="Bioinorganic Chemistry",
author = "Bertini, Ivano and Gray, Harry B.",
month = "January",
year = "1994",
isbn = "0-935702-57-1",
url = "https://resolver.caltech.edu/CaltechBOOK:1994.002",
note = "Copyright © 1994 by University Science Books. Reprinted with permission.",
revision_no = "27",
abstract = "This book covers material that could be included in a one-quarter or one-semester course in bioinorganic chemistry for graduate students and advanced undergraduate students in chemistry or biochemistry. We believe that such a course should provide students with the background required to follow the research literature in the field. The topics were chosen to represent those areas of bioinorganic chemistry that are mature enough for textbook presentation. Although each chapter presents material at a more advanced level than that of bioinorganic textbooks published previously, the chapters are not specialized review articles. What we have attempted to do in each chapter is to teach the underlying principles of bioinorganic chemistry as well as outlining the state of knowledge in selected areas. \n\nWe have chosen not to include abbreviated summaries of the inorganic chemistry, biochemistry, and spectroscopy that students may need as background in order to master the material presented. We instead assume that the instructor using this book will assign reading from relevant sources that is appropriate to the background of the students taking the course. \n\nFor the convenience of the instructors, students, and other readers of this book, we have included an appendix that lists references to reviews of the research literature that we have found to be particularly useful in our courses on bioinorganic chemistry.",
}
@book {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/105209,
title ="Chemical Bonds: An Introduction to Atomic and Molecular Structure",
author = "Gray, Harry B.",
month = "January",
year = "1994",
doi = "10.7907/rt7h-8t44",
isbn = "9781600490125",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20200902-084538354",
note = "© Harry B. Gray. \n\nWith this edition, University Science Books becomes the publisher of Chemi\u00adcal Bonds: An Introduction to Atomic and Molecular Structure. We thank the publisher, Bruce Armbruster, for his interest in chemistry and chemical education. \n\nI should like to thank especially Dr. James L. Hall and Mr. John R. Nelson, who edited the manuscript and made helpful critical comments on each of the several drafts of the manuscript. I am also grateful to Mr. Michael Bertolucci, who read the final draft and offered additional comments and verified the latest values of physical data from several literature sources. At this point an author usually says he must, of course, take responsibility for any remaining errors and impossibly incoherent sections. With all due respect, I should like to share this responsibility with Jim, John, and Mike. So, students and other readers, write and let us know what you think of the book.",
revision_no = "33",
abstract = "This book is intended to provide a reasonably complete introduction to atomic and molecular structure and bonding for science students. Parts of the book are revised and expanded versions of appropriate sections from Basic Principles of Chemistry, which I coauthored with Gilbert P. Haight, Jr. The basic approach of using illustrations profusely in presenting concepts has been retained in this monograph. \n\nThe material on molecular structure is organized roughly in order of molecular size, proceeding from diatomic molecules in Chapter 3 to the \"infinitely large\" atomic clusters in Chapter 6, which deals with the structures of solids. Although Chapter 3 is loaded with \"teaching molecules\" (simple molecules observed only at high temperatures and low pressures), the emphasis in the rest of the book is on \"real molecules.\" Each chapter concludes with a large selection of questions and problems.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/57122,
title ="Electron Transfer in Ruthenium-Modified Cytochromes c. σ-Tunneling Pathways through Aromatic Residues",
author = "Casimiro, Danilo R. and Richards, John H.",
journal = "Journal of Physical Chemistry",
volume = "97",
number = "50",
pages = "13073-13077",
month = "December",
year = "1993",
doi = "10.1021/j100152a007",
issn = "0022-3654",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150430-135530174",
note = "© 1993 American Chemical Society.\n\nReceived: June 3, 1993; in final form: July 22, 1993.\n\nWe thank Prabha Siddarth, Rudy Marcus, David Beratan, and Jos6 Onuchic for helpful discussions; Bill Durham for a preprint of reference IC; Albert Berghuis, Terence Lo, and Gary Brayer for information about the crystal structure of reduced yeast iso- 1-cytochrome c and the Tyr67 - Phevariant; and Michael Smith for the gift of the cytochrome c expression system. The assistance of I-Jy Chang, Bruce Bowler, Thomas Sutherland, John Racs, and Keith Herman in some of the experimental work is acknowledged. This work was supported by the National Science Foundation, the National Institutes of Health, and the Arnold and Mabel Beckman Foundation (this is contribution no. 8678 from the Beckman Institute).",
revision_no = "11",
abstract = "The rates of intramolecular electron-transfer (ET) reactions from the ferroheme to bis(2,2'-bipyridine)(imidazole)-ruthenium(II1) complexes bound to genetically engineered histidines (58 and 66) on the surface of yeast iso-1-cytochrome c (cyt c) have been measured by using a laser flashquench technique. The crystal structure of\nthe wild-type protein indicates that the ET pathways involve aromatic side chains: Ru(His58)cyt c includes\na bridging tryptophan at position 59, and Ru(His66)cyt c has a tyrosine at 67. A variant in which the bridging\nTyr67 in the His66 mutant had been replaced with a phenylalanine also was examined. The Fe^2+ → Ru^(3+)ET\nrate constants (25 °C, pH 7.0) are as follows: 5.2(5) × l0^4 (ΔE° = 0.69(5)), Ru(His58)cyt c; 1.0(1) × 10^6\n(ΔE° = 0.72(5)), Ru(His66)cyt c; and 3.1(3) × l0^6 s^-1 (ΔE° = 0.77(5) eV), Ru(His66Phe67)cyt c. The experimentally derived electronic coupling constants [H_AB(His66)= 0.014; H_AB(HiS66)= 0.060 cm-1 are in closer agreement with the lengths of a-tunneling pathways than with the direct donor-acceptor distances, and there is no indication that the u orbitals of intervening groups enhance any of these couplings. Maximum ET rates in the modified cytochromes drop by 2 orders of magnitude for every 6.3-A increase in the a-tunneling length. Analysis of the results also suggests that an internal water molecule in Ru(His66Phe67)cyt c plays a role in linking the Ru(His66) group to the heme.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/931,
title ="Structurally engineered cytochromes with unusual ligand-binding properties: Expression of Saccharomyces cerevisiae Met-80 --> Ala iso-1-cytochrome c",
author = "Lu, Yi and Casimiro, Danilo R.",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "90",
number = "24",
pages = "11456-11459",
month = "December",
year = "1993",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:LUYpnas93",
note = "© 1993 by the National Academy of Sciences. \n\nContributed by Harry B. Gray, August 23, 1993. \n\nWe thank Michael Smith for the yeast iso-1-cytochrome c expression system, Frances Arnold for the metal-chelating cytochrome c gene, Torbjdorn Pascher for providing purified cytochrome P450(cam), and Lynn Williams for the sequence analyses. K.L.B. acknowledges a Kodak fellowship. This work was supported by the National Science Foundation, the National Institutes of Health, and the Arnold and Mabel Beckman Foundation. \n\nThe publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked \"advertisement\" in accordance with 18 U.S.C. §1734 solely to indicate this fact.",
revision_no = "9",
abstract = "A strategy has been developed to express and purify a recombinant, nonfunctional axial-ligand mutant of iso-1-cytochrome c (Met-80 --> Ala) in Saccharomyces cerevisiae in quantities necessary for extensive biophysical characterization. It involves coexpressing in the same plasmid (YEp213) the nonfunctional gene with a functional gene copy for complementation in a selective medium. The functional gene encodes a product with an engineered metal-chelating dihistidine site (His-39 and Leu-58 --> His) that enables efficient separation of the two isoforms by immobilized metal-affinity chromatography. The purified Met-80 --> Ala protein possesses a binding site for dioxygen and other exogenous ligands. Absorption spectra of several derivatives of this mutant show striking similarities to those of corresponding derivatives of horse-radish peroxidase, myoglobin, and cytochrome P450. The use of a dual-gene vector for cytochrome c expression together with metal-affinity separation opens the way for the engineering of variants with dramatically altered structural and catalytic properties.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/70446,
title ="Copper(II) and Nickel(II) Octabromo-tetrakis(pentafluorophenyl)Porphyrin Complexes",
author = "Henling, Lawrence M. and Schaefer, William P.",
journal = "Acta Crystallographica Section C",
volume = "49",
number = "10",
pages = "1743-1747",
month = "October",
year = "1993",
doi = "10.1107/S0108270193003051",
issn = "0108-2701",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160920-071508932",
note = "© 1993 International Union of Crystallography. \n\nReceived 6 May 1992; accepted 23 March 1993. \n\nThis work was supported by the US Department of Energy, Morgantown Energy Technology Center, the Gas Research Institute and Sun Company, Inc.",
revision_no = "14",
abstract = "The copper and nickel complexes of 2,3,7,8,12,13,17, 18-octabromo-5,10,15,20-tetrakis(pentaftuorophenyl)\nporphyrin ({4,5,9,10,14,15,19,20-octabromo-2,7,12,17-tetrakis(pentaftuorophenyl)-21,22,23,24-tetraazapentacyclo[l6.2.1.1^(3,6).l^(8,11).l^(13,16)]tetracosa-l,3-(22),4,6,8(23),9,11,13(24),14,16,18(21),19-dodecaene\n}copper(II) 0.5-dichloromethane solvate and {4,5,9,10,14,15,19,20-octabromo-2,7,12,17-tetrakis(pentaftuorophenyl)-21,22,23,24-tetraazapentacyclo(\n16.2.1.1^(3,6).l^(8,11).l^(13,16)]tetracosa-l,3(22),4,6,8(23),9,ll,13(24),14,16,18(21),19-dodecaene} nickel(II)0.5-dichloromethane solvate) form isostructural crystals. There is significant distortion from planarity of the porphyrin ring caused by the octabromo substituents\ninteracting with the meso-pentafluorophenyl groups\nand with each other, with departures of the Br atoms\nfrom the plane defined by the four N atoms of up to\n2.36 A. This tetrahedral distortion of the molecule\ndoes not result in any significant changes in bond\ndistances from those in non-halogenated tetraphenylporphyrin\ncomplexes.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/70448,
title ="A Monodentate 1,3-Diphenyl-2-triazeno Terpyridineplatinum(II) Complex",
author = "Bailey, James A. and Catalano, Vincent J.",
journal = "Acta Crystallographica Section C",
volume = "49",
number = "9",
pages = "1598-1602",
month = "September",
year = "1993",
doi = "10.1107/S0108270193002215",
issn = "0108-2701",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160920-073747901",
note = "© 1993 International Union of Crystallography. \n\nReceived 30 September 1992; accepted 1 March 1993. \n\nWe thank Marilyn M. Olmstead for assistance. This work was supported by an NSERC (Canada) postdoctoral fellowship to JAB, a 1991 NSF postdoctoral research fellowship in chemistry (No. CHE-9101931) to VJC, and grants from the National Science Foundation and the Office of Naval Research.",
revision_no = "10",
abstract = "The compound (l,3-diphenyl-2-triazeno )(2,2',2\"-\nterpyridine)platinum(II) perchlorate dimethylformamide\nsolvate (1) is formed by reaction of dpt (dptH = 1,3-diphenyltriazene) and [Pt(tpy)Cl]Cl (tpy =\nterpyridine) in the presence of excess base (NEt3). There are two independent cations in the asymmetric unit. The platinum centers have a monodentate triazeno ligand with the remaining coordination sites occupied by the terpyridine group. The crystal packing is dominated by π-π stacking interactions, and metal-metal interactions are conspicuously absent.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/57128,
title ="Site saturation of the histidine-46 position in Pseudomonas aeruginosa azurin: Characterization of the His46Asp copper and cobalt proteins",
author = "Germanas, Juris P. and Di Bilio, Angel J.",
journal = "Biochemistry",
volume = "32",
number = "30",
pages = "7698-7702",
month = "August",
year = "1993",
doi = "10.1021/bi00081a014",
issn = "0006-2960",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150430-160127576",
note = "© 1993 American Chemical Society.\n\nReceived February 15, 1993; Revised Manuscript Received May 24, 1993.\n\nThe authors thank William B. Connick, Deborah S. Wuttke, Tadashi J. Mizoguchi, Cindy D. Strong, and Yi Lu for helpful discussions. We are grateful to Sam Kim of the Caltech Jet Propulsion Laboratory (JPL) for assistance with the EPR measurements.\n\nThis research was supported by the National Institutes of Health (GM16424 to J.H.R.; DK19038 to H.B.G.) and the National Science Foundation. J.P.G. thanks the NIH for a postdoctoral fellowship.",
revision_no = "10",
abstract = "Cassette mutagenesis has been used to replace the copper ligand His46 of Pseudomonas aeruginosa azurin with 19 other amino acids and a stop codon. Several mutant proteins were expressed in Escherichia coli and isolated; however, only the variant in which His was replaced by Asp exhibited the spectral characteristics of a blue (type 1) center. The spectroscopic and electrochemical properties of this mutant\nprotein show that the copper site is perturbed relative to wild-type azurin. The absorption spectrum of Cu(II)(His46Asp) azurin exhibits a S(Cys)-Cu(II) band at 612 nm, as well as weaker features at ~300, 454, and ~850 nm; its EPR spectrum is rhombic (g|| = 2.327(1), g_x ≈ 2.03, and g_y, ≈ 2.07; A|| ≈ 22(2) X 10^(-4), A_x, ≈ 46 X 10^(-4), and A_y, ≈ 22 X 10^(-4) cm^(-l)). The reduction potential of the mutant (260 mV us NHE at pH 8.5; 297 mV at pH 5.0) is lower than that of wild-type azurin (288 mV at pH 8.5; 349 mV at pH 5.0). The S(Cys)-Co(II) absorption bands (~300 and 362 nm) in Co(II)(His46Asp) azurin are strongly blue-shifted relative to those (330 and 375 nm) in the spectrum of the Co(II)(His46) protein, whereas the intensities of the ligand-field bands in the 500-650-nm region (∈ ≈ 100 M^(-1) cm^(-l)) indicate a five-coordinate Co(I1) environment.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/73591,
title ="A highly solvated zinc(II) tetrakis(pentafluorophenyl)-β-octabromoporphyrin",
author = "Marsh, Richard E. and Schaefer, William P.",
journal = "Acta Crystallographica Section C",
volume = "49",
number = "7",
pages = "1339-1342",
month = "July",
year = "1993",
doi = "10.1107/S0108270193000642",
issn = "0108-2701",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170120-134251529",
note = "© 1993 International Union of Crystallography. \n\nReceived 6 May 1992; accepted 18 January 1993. \n\nThis work was supported by the US Department of Energy, Morgantown Energy Technology Center, the Gas Research Institute, and the Sun Company, Inc.",
revision_no = "13",
abstract = "The title compound, {4,5,9,10,14,15,19,20-octabromo-2,7,12,17-tetrakis(pentafluorophenyl)-21,22,23,-\n24-tetraazapentacyclo[16.2.1.1^(3,6).1^(8,11).1^(13,16)]tetracosa-1,3(21),4,6,8(22),9,11,13(23),14,16,18(24),19-dodecaene\n}zinc(II) (carbon tetrachloride, o-dichlorobenzene,\nacetone, methanol, water solvate) has a large\ntetrahedral distortion, with the Br atoms as much as\n1.83 Å from the plane of the N atoms. The distortion affects primarily bond angles and bond torsion angles; bond distances in the molecule are normal. Several different solvents are incorporated into the\ncrystal, providing a close (2.16 Å) O atom as an axial\nneighbor to Zn and a more distant (3.16 Å) Cl atom,\nin the opposite axial site.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/70439,
title ="Copper(II) tetrakis(pentafluorophenyl)-β-octachloroporphyrin",
author = "Schaefer, William P. and Hodge, Julia A.",
journal = "Acta Crystallographica Section C",
volume = "49",
number = "7",
pages = "1342-1345",
month = "July",
year = "1993",
doi = "10.1107/S0108270193000587",
issn = "0108-2701",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160919-153000293",
note = "© 1993 International Union of Crystallography. \n\nReceived 6 May 1992; accepted 15 January 1993. \n\nThis work was supported by the US Department of Energy, Morgantown Energy Technology Center, the Gas Research Institute, and the Sun Company, Inc.",
revision_no = "13",
abstract = "The title compound, {4,5,9,10,14,15,19,20-octachloro-2,7,12, 17-tetrakis(pentafluorophenyl)-20,22,23,24-\ntetraazapentacyclo[l6.2.l.1^(3·6).l^(8·11).l^(13·16)]tetracosa-1,3(21),4,6,8(22),9,11, 13(23), 14, 16, 18(24), 19-dodecaene}copper(II)(CuTFPPC1_8)dichloromethane solvate,\nshows a large tetrahedral distortion or ruffling, with pairs of Cl atoms alternately averaging + 1.20 and -1.18 Å out of the plane of the four N atoms; the Cu atom is 0.01 Å out of the plane and the N atoms show a slight (±0.12 Å) tetrahedral distortion. A Cl atom of the solvent, at 3.515 (6) Å in an approximately axial position, is the closest non-bonded neighbor of the Cu atom.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/70344,
title ="Structure of dicarbonylbis-(μ-3,5-dimethylpyrazolyl)-bis(4-tolyl diphenylphosphinite)diiridium(I)–dichloromethane (1/1)",
author = "Farid, Ramy S. and Henling, Lawrence M.",
journal = "Acta Crystallographica Section C",
volume = "49",
number = "7",
pages = "1363-1365",
month = "July",
year = "1993",
doi = "10.1107/S010827019201299X",
issn = "0108-2701",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160914-104244122",
note = "© 1993 International Union of Crystallography. \n\nReceived 18 June 1992; accepted 9 December 1992.",
revision_no = "16",
abstract = "In bis(μ-3,5-dimethylpyrazolyl-N:N')-bis[carbonyl( 4-tolyl diphenylphosphinite-P)iridium(I)] dichloromethane solvate, two Ir^I atoms are joined by two 3,5-dimethylpyrazolyl bridges with one carbonyl and one 4-tolyl\ndiphenylphosphinite ligand completing the square-planar\ngeometry about each Ir atom. The Ir· · ·Ir distance of\n3.307 (1) Å is greater than the distance of 3.22 Å found in a similar pyrazolyl-bridged iridium(I) dimer [Fox (1989). PhD dissertation, California Institute of Technology, USA].",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/86171,
title ="Excited-state decay processes of binuclear rhodium(I) isocyanide complexes",
author = "Miskowski, Vincent M. and Rice, Steven F.",
journal = "Journal of Physical Chemistry",
volume = "97",
number = "17",
pages = "4277-4283",
month = "April",
year = "1993",
doi = "10.1021/j100119a007",
issn = "0022-3654",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180501-151530016",
note = "© 1993 American Chemical Society. \n\nReceived: November 18, 1992; In Final Form: January 22, 1993. \n\nWe thank David Smith for helpful discussions. This work was supported by National Science Foundation Grant CHE-8922067. Work at Brookhaven National Laboratory was performed under Contract DE-AC02-76CH00016 with the US. Department of Energy and supported by its Division of Chemical Sciences, Office of Basic Energy Sciences.",
revision_no = "9",
abstract = "Emission lifetimes, quantum yields, and polarized excitation spectra of Rh_2b_4^(2+) and Rh_2(TMB)_4^(2+) (b = 1,3-diisocyanopropane; TMB = 2,5-diisocyano-2,5-dimethylhexane) have been determined. The singlet and triplet dσ* → pσ(^(1,3)A_(2u) excited states are luminescent with radiative rates of ca. 10^8 and 10^ s^(-1), respectively, consistent with values obtained from Strickler-Berg calculations based on the corresponding absorption bands. Both singlet and triplet upper excited states (dπ → pσ and metal-to-metal charge transfer, E_u symmetry) undergo nonradiative decay primarily to ^3A_(2u), bypassing ^1A_(2u), and the branching ratios for decay through several intermediate states have been estimated. The temperature dependences of the lifetimes of the ^1A_(2u), and ^3A_(2u) states of Rh_2(TMB)_4^(2+) are interpreted in terms of a model in which potential-surface crossings with the ^3B_(2u)\n(dσ* - d_(x^2 - y^2)) state facilitate nonradiative decay.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/70343,
title ="A diphenylformamidinate-bridged terpyridineplatinum(II) dimer",
author = "Bailey, James A. and Miskowski, Vincent M.",
journal = "Acta Crystallographica Section C",
volume = "49",
number = "4",
pages = "793-796",
month = "April",
year = "1993",
doi = "10.1107/S0108270192010229",
issn = "0108-2701",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160914-102216766",
note = "© 1993 International Union of Crystallography. \n\nReceived 3 June 1992; accepted 29 September 1992. \n\nWe thank William Schaefer for assistance. This work was supported by an NSERC (Canada) Postdoctoral Fellowship to JAB and a grant from the Office of Naval Research.",
revision_no = "13",
abstract = "The compound μ-N,N' -diphenylformamidinatobis[\n2,2',2\"-terpyridineplatinum(II)] perchlorate\nmono hydrate (1) is formed by reaction of diphenylformamidine\nand [Pt(tpy)Cl]Cl (tpy = terpyridine) in\nthe presence of excess base. The two platinum\ncenters are bridged by a single diphenylformamidinato\nligand with the remaining coordination geometry\ncompleted by the terpyridine group. The\nplatinum-platinum separation is 3.049 (1) Å.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/57120,
title ="Electron Transfer in Ruthenium/Zinc Porphyrin Derivatives of\nRecombinant Human Myoglobins. Analysis of Tunneling Pathways in Myoglobin and Cytochrome c",
author = "Casimiro, Danilo R. and Wong, Luet-L.",
journal = "Journal of the American Chemical Society",
volume = "115",
number = "4",
pages = "1485-1489",
month = "February",
year = "1993",
doi = "10.1021/ja00057a037",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150430-135323908",
note = "© 1993 American Chemical Society.\n\nReceived August 28, 1992.\n\nWe thank David N. Beratan for helpful discussions, Atsuo Kuki for a preprint of ref 9b, Steven G. Boxer for the HuMb gene, and David G. Lambright, Steve R. Hubbard, and Wayne A. Hendrickson for providing us with the coordinates\nof a mutant human myoglobin. We are indebted to Thomas\nSutherland for performing the large cell growth. J.L.C. acknowledges support from an NSF postdoctoral fellowship\n(CHE-9002195) and L.-L.W. thanks SERC (United Kingdom)\nfor a NATO postdoctoral fellowship. This research was supported by the National Science Foundation, the National Institutes of Health, and the Arnold and Mabel Beckman Foundation.",
revision_no = "23",
abstract = "Site-directed mutants of human myoglobin have been prepared and characterized; each protein has a single\nsurface-modifiable histidine (at position 48, 70, or 83). The proteins were modified by covalent attachment of pentaammineruthenium (a_5Ru) to the surface histidine and substitution of zinc mesoporphyrin IX diacid (ZnP) for the heme. Donor-acceptor separations (edge-edge distances d) in the modified proteins are 9.5 Å, His70; 12.7 Å, His48; and 15.5 Å, His83. Rates of photoinduced electron transfer in these ruthenium-modified myoglobins were measured by transient absorption spectroscopy. The ^(3)ZnP* → Ru^3+ rate constants are 1.6 × 10^7 (His70), 7.2 × 10^4 (His48), and 4.0 × 10^2 s^-1 (His83) (-ΔG°= 0.82 eV); charge-recombination (Ru^2+ → ZnP^+) rates are 1.1 × 10^5 (His48) and 7.3 × 10^2 s^-1 (His83) (-ΔG° = 0.96 eV). Activationless (maximum) rates assuming h = 1.3 eV are 7.2 X lo7 (His70), 3.3 × 10^5 (His48) and 1.8 × 10^3 s^-1 (His83). Distant electronic couplings, which limit the maximum rates in the modified myoglobins, have been analyzed along with data from Ru-modified cytochromes c in terms of a tunneling pathway model. Single dominant pathways adequately describe the electronic couplings in cytochrome c but do not satisfactorily account for the myoglobin couplings. The correlation of electronic coupling with tunneling length for myoglobin is improved significantly by the inclusion of multiple pathways.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/76128,
title ="Spectroscopic and structural properties of binuclear platinum-terpyridine complexes",
author = "Bailey, James A. and Miskowski, Vincent M.",
journal = "Inorganic Chemistry",
volume = "32",
number = "4",
pages = "369-370",
month = "February",
year = "1993",
doi = "10.1021/ic00056a001",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20170408-160639375",
note = "© 1993 American Chemical Society. \n\nReceived August 11, 1992. \n\nWe thank Virginia Houlding for measuring the solid-state lifetimes of compound 4 (Table I) and Chi-Ming Che for helpful discussions. J.A.B. acknowledges an NSERC (Canada) Postdoctoral Fellowship. \n\nThis work was supported by the National Science Foundation and the Office of Naval Research.",
revision_no = "10",
abstract = "[No abstract]",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/52434,
title ="Electron-tunneling pathways in proteins",
author = "Beratan, David N. and Onuchic, José Nelson",
journal = "Science",
volume = "258",
number = "5089",
pages = "1740-1741",
month = "December",
year = "1992",
doi = "10.1126/science.1334572",
issn = "0036-8075",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20141205-110550464",
note = "© 1992 American Association for the Advancement of Science.\n\nWe thank J. Regan for assistance in the pathway\ncalculations and preparation of Fig. 2. Supported\nby the National Science Foundation, the National\nInstitutes of Health, the Department of Energy, and\nthe Arnold and Mabel Beckman Foundation.",
revision_no = "11",
abstract = "Electron-transfer (ET) reactions\nare key steps in photosynthesis,\nrespiration, drug metabolism, and\nmany other biochemical processes.\nThese ET processes commonly occur\nbetween protein-bound prosthetic\ngroups that are separated by\nlarge molecular distances (often\ngreater than 10 Å. Although the\nelectron donors and acceptors in\nthese reactions are expected to be\nweakly coupled, the ETs are remarkably\nfast and proceed with high\nspecificity. On page 1748 of this\nissue, Pelletier and Kraut (1) present\nwork on the crystal structures of\ncytochrome c-cytochrome c peroxidase\ncomplexes that could lead\nto a much deeper understanding of\nhow the intervening medium controls\ninterprotein ET reactions.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/57194,
title ="Blue to type 2 binding. Copper(II) and cobalt(II) derivatives of a Cys112Asp mutant of Pseudomonas aeruginosa azurin",
author = "Mizoguchi, Tadashi J. and Di Bilio, Angel J.",
journal = "Journal of the American Chemical Society",
volume = "114",
number = "25",
pages = "10076-10078",
month = "December",
year = "1992",
doi = "10.1021/ja00051a059",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150504-113949666",
note = "© 1992 American Chemical Society. \n\nReceived June 29, 1992. \n\nWe thank Dr. David B. Goodin of the Scripps Research Institute for assistance with the EPR measurements. This work was supported by grants from the National Institutes of Health (DK19038 to H.B.G.; GM16424 to J.H.R.; GM07616 traineeship to T.J.M.).",
revision_no = "10",
abstract = "Of the five invariant residues that surround the copper in azurins, the ligand cysteine at position 112 (Cys112) is believed to be especially important in the bonding interactions responsible for the unusual blue copper absorption and electron paramagnetic resonance (EPR) spectra. It is striking that mutagenesis studies of Met121, His46, and His174 ave shown that these ligands are not required for a blue copper center, thereby reinforcing the feeling that Cys112 is absolutely essential. To address this issue directly, we have replaced Cys112 with Asp by site-directed mutagenesis.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/70352,
title ="A Bis(pyrazolyl)(bipyridyl)platinum Complex",
author = "Schaefer, William P. and Connick, William B.",
journal = "Acta Crystallographica Section C",
volume = "48",
number = "10",
pages = "1776-1778",
month = "October",
year = "1992",
doi = "10.1107/S0108270192002026",
issn = "0108-2701",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160914-141706072",
note = "© 1992 International Union of Crystallography. \n\nReceived 26 December 1991; accepted 11 February 1992. \n\nThis research was supported by the Office of Naval Research.",
revision_no = "12",
abstract = "(4,4' -Dimethyl-2,2'-bipyridyl)bis(3,5-dimethylpyrazolium)\nplatinum(II) 0.5-tetrahydrofuran solvate monohydrate, [Pt(C_5H_7N_2MC_(12)H_(12)-N2)].0.5C_4H_80.H_2O, M_r = 623.65, monoclinic, P2_1/n, ɑ = 8.625 (2), b = 20.593 (8), c = 14.451(4) Å, β = 90.32 (2)°, v = 2566.7 (14) Å^3, Z = 4, D_x = 1.61 g cm^(-3), λ(Mo Kɑ)= 0.71073 Å, μ = 55.50 cm^(-1), F(000) = 1232, room temperature, R = 0.0387 for 2874 reflections with F_o^2 > 3σ(F_o^2). The square-planar Pt complex has normal Pt-N(bipyridyl) bonds [2.009 (8) Å] and slightly short\nPt-N(pyrazolyl) bonds [1.983 (7) Å]. The ligand molecules have normal distances and angles; the planes of the pyrazolyl ligands are twisted by about 60° to the bipyridyl-Pt plane, with the closest contacts between the pyrazolyls being -3.3 Å (Cl4···N5\nand C19···N3).",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/88655,
title ="Photoinduced electron transfer in ruthenium-modified cytochrome c",
author = "Gray, Harry B. and Winkler, Jay R.",
journal = "Pure and Applied Chemistry",
volume = "64",
number = "9",
pages = "1257-1262",
month = "September",
year = "1992",
doi = "10.1351/pac199264091257",
issn = "0033-4545",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180808-101753428",
note = "© 1992 IUPAC.",
revision_no = "8",
abstract = "Distant heme-Ru electronic couplings have been extracted from intramolecular electron-transfer rates in Ru(histidine-X) (X=33,39,62) derivatives of cytochrome c. The rates (and the couplings) correlate with the lengths of σ-tunneling pathways comprised of covalent bonds, hydrogen bonds, and through-space jumps from the histidines to the heme group.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/70336,
title ="A μ-Bis(phosphino)ethane Gold(I) Dimer",
author = "Schaefer, William P. and McCleskey, T. Mark",
journal = "Acta Crystallographica Section C",
volume = "48",
number = "8",
pages = "1397-1399",
month = "August",
year = "1992",
doi = "10.1107/S010827019101507X",
issn = "0108-2701",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160914-100609791",
note = "© 1992 International Union of Crystallography. \n\nReceived 30 August 1991; accepted 24 December 1991. \n\nThis work was supported by NSF Grant CHE89-22067.",
revision_no = "12",
abstract = "Bis(bromo,cyano )-μ-[bis( dicyclohexylphosphino))ethane-P,P']-digold, [Au_2( C_(26)H_(48)P_2){Br_(1.16)(CN)_(0.84)}], M_r= 931.09, monoclinic, P2_1/n, ɑ = 9.772 (3), b = 15.366 (4), c = 20.973 (5) Å, β = 102.53(2)º, V = 3074.2 (15) Å^3, Z = 4, D_x = 2.01 g cm^(-3), λ(Mo Kɑ)= 0.71073 Å, μ = 111.2 cm^(-1), F(000) = 1774, room temperature\n(297 K), R = 0.029 for 2255 reflections with F_o > 3σ(f_o^2).\nA bis(dicyclohexylphosphino)ethane ligand bonds one Au atom at each P atom. The Au atoms are further bonded to Br^- or CN^- ions in a disordered manner, with the bromide populations being 0.532 (5) on Aul and 0.628 (5) on Au2.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/70339,
title ="A μ-pyrazolyl terpyridineplatinum(II) dimer",
author = "Bailey, James A. and Gray, Harry B.",
journal = "Acta Crystallographica Section C",
volume = "48",
number = "8",
pages = "1420-1422",
month = "August",
year = "1992",
doi = "10.1107/S010827019200074X",
issn = "0108-2701",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160914-100610831",
note = "© 1992 International Union of Crystallography. \n\nReceived 16 September 1991; accepted 14 January 1992. \n\nWe thank Larry Henling for his assistance. This work was supported by an NSERC (Canada) Postdoctoral Fellowship to JAB and a grant from the Office of Naval Research (N00014-89-J-3198).",
revision_no = "13",
abstract = "μ-(Pyrazolyl-N:N')-bis[(2,2',2\"-terpyridine) platinum(II)] perchlorate acetonitrile solvate, [Pt_2(C_(15)H_(11)N_3)_2 {C_3H_3N_2)](ClO_4)_3.CH_3CN, M_r = 1263.18, orthorhombic, Pnma, ɑ = 18.172 (2), b = 17.950 (3), c = 12.086 (4) Å, V= 3942.3 (15) Å^3, Z = 4, D_x = 2.128 g cm^(-3), λ(Mo Kɑ)= 0.71073 Å, μ = 74.41 cm^(-1), F(000) = 2416, room temperature (297 K), R = 0.0337 for 2510 reflections with F_o^2 > 3σ(F_o^2). A single pyrazolyl unit bridges two Pt centres. The square-planar coordination around each\nPt atom is completed by a tridentate terpyridine ligand. The Pt•••Pt separation is 3.432 (1) Å with an inclination of 47.7 (12)º between the two Pt square planes.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/29805,
title ="Pathway Analysis of Protein Electron-Transfer Reactions",
author = "Onuchic, José Nelson and Beratan, David N.",
journal = "Annual Review of Biophysics and Biomolecular Structure",
volume = "21",
pages = "349-377",
month = "June",
year = "1992",
doi = "10.1146/annurev.biophys.21.1.349 ",
issn = "1056-8700",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20120322-085550897",
note = "© 1992 Annual Reviews.\n\nWork in San Diego was funded by the National Science Foundation (Grant\nNo. DMB-9018768) and a research contract from the Jet Propulsion\nLaboratory, supported by the Department of Energy’s Catalysis/Biocatalysis Program. This work was performed in part at the Jet Propulsion\nLaboratory, California Institute of Technology, and was sponsored\nby the Department of Energy’s Catalysis/Biocatalysis Program\n(Advanced Industrial Concepts Division), through an agreement with the\nNational Aeronautics and Space Administration. Experimental work at\nthe Beckman Institute was supported by the National Science Foundation\nand the National Institutes of Health.",
revision_no = "13",
abstract = "One of the central challenges in molecular biophysics is to understand how\nproteins control biochemical reactions in living organisms. In their folded\nstates, proteins exhibit a variety of structural fluctuations. The question\nbefore us is; how do protein structure and dynamics control biological\nfunction? Our goal is to develop tools that allow us to simulate and\nunderstand those aspects of biomolecular structure and dynamics that\nestablish the unique capabilities of these molecules. Our hope is to arrive\nat a deeper understanding of the mechanisms that control biochemical\nreactions and to establish design criteria for new proteins that will perform\nspecific tasks.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/86673,
title ="Fluorescence excitation spectra of quadruply bonded M_2X_4L_4 complexes",
author = "Miskowski, Vincent M. and Gray, Harry B.",
journal = "Inorganic Chemistry",
volume = "31",
number = "11",
pages = "2085-2091",
month = "May",
year = "1992",
doi = "10.1021/ic00037a020",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180529-121842960",
note = "© 1992 American Chemical Society. \n\nReceived August 19, 1991. \n\nWe thank Bill Schneider and Bruce Bursten for several helpful discussions and for providing us the results of their calculations prior to publication. This research was supported by National Science Foundation Grants CHE89-22067 (H.B.G.) and CHE86-57422 (M.D.H.).",
revision_no = "9",
abstract = "Fluorescence excitation spectra have been obtained by monitoring the emissive ^1(δδ*) excited states of Mo_2X_4(PMe_3)_4 (X= CI, Br, I), Mo_2CI_4(AsMe_3)_4), and W_2Cl_4(PMe_3)_4 in solution at 300 and 77 K. The polarization ratios of these transitions, and their shifts in energy arising from substitution of the metal and ligand, have been correlated with predictions derived from available theoretical calculations and photoelectron spectroscopic data to yield self-consistent assignments of all observed bands in the UV region. These bands, with the exception of a poorly characterized one at the edge of the vacuum-UV region, are assigned to singlet excitations from metal-metal (δ, σ, π) and ligand (σ(MP), σ(MX), π(X)) orbitals to the δ* orbital.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/53928,
title ="Electron-Tunneling Pathways in Cytochrome c",
author = "Wuttke, Deborah S. and Bjerrum, Morten J.",
journal = "Science",
volume = "256",
number = "5029",
pages = "1007-1009",
month = "May",
year = "1992",
doi = "10.1126/science.256.5059.1007 ",
issn = "0036-8075",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150121-092819858",
note = "© 1992 American Association for the Advancement of Science.\n\n27 December 1991; accepted 10 March 1992.\n\nWe thank D. N. Beratan for assistance with the pathway analyses and for many helpful discussions. D.S.W. acknowledges an NSF predoctoral fellowship and a fellowship from the Parsons Foundation. M.J.B. was the Carlsberg Foundation Scholar in the Beckman Institute during 1990-91.\nSupported by National Science Foundation grants CHE-8822988 and CHE-9119992.",
revision_no = "11",
abstract = "Distant Fe2+-Ru3+ electronic couplings have been extracted from intramolecular electron-transfer rates in Ru(histidine^x) (where X = 33, 39, 62, and 72) derivatives of cytochrome c. The couplings increase according to 62 (0.0060) < 72 (0.057) < 33 (0.097) < 39 (0.11 per wave numbers); however, this order is out of line with the histidine to heme edge-edge distances [62 (14.8) > 39 (12.3) > 33 (11.1) > 72 (8.4 angstroms)]. The rates (and the couplings) correlate with the lengths of σ-tunneling pathways comprised of covalent bonds, hydrogen bonds, and through-space jumps from the histidines to the heme group. Space jumps greatly decrease couplings: One from Pro71 to Met80 extends the σ-tunneling length of the His^72 pathway by roughly 10 covalent-bond units.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/83364,
title ="Electron transfer in ruthenium-modified proteins",
author = "Winkler, Jay R. and Gray, Harry B.",
journal = "Chemical Reviews",
volume = "92",
number = "3",
pages = "369-379",
month = "May",
year = "1992",
doi = "10.1021/cr00011a001",
issn = "0009-2665",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20171120-153658117",
note = "© 1992 American Chemical Society. \n\nReceived September 16, 1991 (Revised Manuscript Received February 26, 1992). \n\nResearch on Ru-modified proteins in the Beckman Institute (Contribution No. 8506) at the California Institute of Technology has been supported by grants from the National Science Foundation and the National Institutes of Health.",
revision_no = "9",
abstract = "The electron-transfer (ET) reactions of metalloproteins\nare potentially far more complex than those of small molecules. The structural intricacies of proteins are largely responsible for the added complexity. Reactive centers are surrounded by polypeptide matrices that shield these sites from solvent and separate them from their redox partners. The nonuniform charge distributions on the protein surfaces create anisotropic interactions between redox partners, confounding the interpretation of bimolecular reactions. Covalent or electrostatic coupling of redox partners can be exploited to simplify the problem but does not eliminate all of the complicating factors in metalloprotein ET reactions. The energetics and dynamics\nof nuclear reorientations accompanying protein ET reactions continue to be a source of inquiry. Multiple conformational states in the polymer surrounding the redox sites create the potential for \"gating\" and directional electron transfer. The peptide matrix also separates the redox sites, leading to questions of how protein ET can be efficient over such long (> 10 Å) distances. One line of research aimed at addressing many of the fundamental issues in protein ET involves the use of proteins modified by the coordination of Ru complexes to surface amino acid residues.",
}
@book_section {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/86027,
title ="Nitrido and Oxo Complexes of Rhenium(V)",
author = "Sullivan, B. Patrick and Brewer, John C.",
volume = "29",
pages = "146-150",
month = "January",
year = "1992",
doi = "10.1002/9780470132609.ch35",
issn = "19344716",
isbn = "9780471544708",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180424-151505941",
note = "© 1992 by Inorganic Syntheses, Inc. \n\nPublished Online: 05 January 2007; Published Print: 01 January 1992.",
revision_no = "10",
abstract = "This chapter contains sections titled:\nDichloronirtridobis(triphenylphosphine)rhenium(V),RenCl_2(PPh_3)_2;\ntrans‐Ethyxodiiodooxobis(triphenylphosphine)rhenium(V),ReOl_2(OEt)(PPh_3)_2;\nIododioxobis(triphenylphospphine)rhenium(V),ReO_2I(PPh_3)_2.",
}
@book_section {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/57218,
title ="Long-Range Electron Transfer in Ruthenium-Modified Cytochromes c. σ-Tunneling Pathways through Aromatic Residues",
author = "Casimiro, Danilo R. and Winkler, Jay R.",
volume = "2",
pages = "829-832",
month = "January",
year = "1992",
isbn = "9780792320913",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150505-090548164",
note = "© 1992 Kluwer Academic Publishers.",
revision_no = "12",
abstract = "Studies of intramolecular electron transfer (ET) in chemically-modified\nmetalloproteins have suggested that the long-range donor-acceptor coupling is\ndetermined by the structure of the bridging polypeptide medium. One issue that\nremains largely unclear is whether aromatic side chains in the intervening medium\nenhance these electronic couplings to a significant extent To address this issue, we\nhave prepared site-directed mutants of Saccharomyces cerevisiae iso-1-cytchrome c,\nwhere in each case a surface histidine for ruthenium labeling is introduced at either\nposition 58 or 66. Based on the crystal structure of the protein, a tryptophan (at\nposition 59) or a tyrosine (67) is found along the ET path between the Ru-modified\nhistidine and the heme. In order to probe the role of the bridging Tyr67 in the His66\nvariant, this internal residue has been replaced with a phenylalanine.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/70327,
title ="A luminescent gold complex: bis-μ-[bis(dicyclohexylphosphino)ethane-P,P']-digold bis(hexafluorophosphate)",
author = "Schaefer, W. P. and Marsh, R. E.",
journal = "Acta Crystallographica Section C",
volume = "47",
number = "12",
pages = "2553-2556",
month = "December",
year = "1991",
doi = "10.1107/S0108270191007618",
issn = "0108-2701",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20160914-072746184",
note = "© 1991 International Union of Crystallography. \n\nReceived 26 February 1991; accepted 25 June 1991. \n\nThis work was supported in part by National Science Foundation Grant CHE 89-22067.",
revision_no = "13",
abstract = "[Au_2(C_(26)H_(48)P_2h](PF_6)_2, M_r = 1529·1, tetragonal, P4n2, ɑ= 15·917 (5), c = 12-448 (1) A, V = 3154 (1) A3\n, Z = 2, Dx = 1·61 g cm^(-3), λ(Mo Ka) = 0·71073 A, μ = 50·1 cm^(-1), F(000) = 1528, room temperature (297 K), R = 0·064 for 3525 reflections with F/_o^2 > 0,0·038 for 2440 with F/_o^2 > 3σ(F/_o^2). This [Au_2(C_26)H_(48)P_2)_2] (PF_6)_2 compound shows a strong luminescence in the solid state at 77 K. The cation consists of two Au atoms joined by two bis (dicyclohexylphosphino )ethane links, with one Au atom and one half of a link being the asymmetric unit. The Au-Au distance [2·936 (1) Å] is only slightly longer than the 2·884 Å found in gold metal, indicative of substantial metal-metal bonding.",
}
@book_section {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/85643,
title ="Long-Range Electron Transfer in Heme Proteins Porphyrin-Ruthenium Electronic Couplings in Three Ru(His)Cytochromes c",
author = "Therien, Michael J. and Bowler, Bruce E.",
number = "228",
pages = "191-199",
month = "May",
year = "1991",
doi = "10.1021/ba-1991-0228.ch012",
issn = "0065-2393",
isbn = "9780841218468",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180405-131938655",
note = "© 1991 American Chemical Society. \n\nReceived for review April 27, 1990. Accepted revised manuscript August 29, 1990. Published in print 5 May 1991.\n\nWe thank David Beratan for helpful discussions. Both M. J. Therien (National Institutes of Health) and Β. E. Bowler (Medical Research Council of Canada) acknowledge postdoctoral fellowships. Research at the California Institute of Technology was suported by the National Science Foundation (CHE88-22988) and the National Institutes of Health (DK19038). Research performed at Brookhaven National Laboratory was carried out under Contract DE-AC02-CH00016 with the U.S. Department of Energy and supported by its Division of Chemical Sciences, Office of Basic Energy Sciences.",
revision_no = "10",
abstract = "The kinetics of long-range electron transfer (ET) have been measured in Ru(NH_3)_4L(His 39) derivatives (L is NH_3, pyridine, or isonicotinamide) of Zn-substituted Candida krusei cytochrome c and Ru(NH_3)_4L(His 62) derivatives (L is NH_3 or pyridine) of Zn-substituted Saccharomyces cerevisiae cytochrome c. The rates of both excited-state electron transfer and thermal recombination are approximately 3 times greater in Ru(His 39)cytochrome c (Zn) than the rates of the corresponding reactions in Ru(His 33)cytochrome c (Zn), but analogous ET reactions in Ru(His 62)cytochrome c (Zn) are roughly 2 orders of magnitude slower than in the His 33-modified protein. Analysis of driving-force dependences establishes that the large variations in the ET rates are due to differences in donor-acceptor electronic couplings. Examination of potential ET pathways indicates that hydrogen bonds could be responsible for the enhanced electronic couplings in the Ru(His 39) and Ru(His 33) proteins.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/54066,
title ="Gaussian Free-Energy Dependence of Electron-Transfer Rates in Iridium Complexes",
author = "Fox, Lucius S. and Kozik, Mariusz",
journal = "Science",
volume = "247",
number = "4946",
pages = "1069-1071",
month = "March",
year = "1990",
doi = "10.1126/science.247.4946.1069",
issn = "0036-8075",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150126-094014828",
note = "© 1990 American Association for the Advancement of Science.\n\n7 September 1989; accepted 4 December 1989.\n\nWe thank B. S. Brunschwig for assistance with the λ_OUT calculation. The work of L.S.F.w as supported by a graduate research fellowship from British Petroleum America. Research at the California Institute of Technology was supported by National Science Foundation grant CHE84-19828 (contribution 7977 from the Arthur Amos Noyes Laboratory). Research at Brookhaven National Laboratory was carried out under contract DE-AC02-76CH00016 with the U.S. Department of Energy and supported by its Division of Chemical Sciences, Office of Basic Energy Sciences.",
revision_no = "10",
abstract = "The kinetics of photoinduced electron-transfer (ET) reactions have been measured in a series of synthetic donor-acceptor complexes. The electron donors are singlet or triplet excited iridium(I) dimers (Ir_2), and the acceptors are N-alkylpyridinium groups covalently bound to phosphinite ligands on the Ir_2 core. Rate constants for excited-state ET range from 3.5 x 10^6 to 1.1 x 10^(11) per second, and thermal back ET (pyridinium radical to Ir_(2)^+) rates vary from 2.0 x 10^(10) to 6.7 x 10^7 per second. The variation of these rates with driving force is in remarkably good agreement with the Marcus theory prediction of a Gaussian free-energy dependence.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/83043,
title ="Synthesis and Characterization of [Ir_2(TMB)_4H_2][B(C_6H_5)_4]_2·CH_3C_6H_5",
author = "Smith, David C. and Marsh, Richard E.",
journal = "Inorganic Chemistry",
volume = "29",
number = "3",
pages = "534-538",
month = "February",
year = "1990",
doi = "10.1021/ic00328a039",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20171107-152617829",
note = "© 1990 American Chemical Society. \n\nReceived June 28, 1989. \n\nD.C.S. thanks the Sun Co. for a graduate fellowship. This research was supported by National Science Foundation Grant CHE84-19828.",
revision_no = "14",
abstract = "The ^3(dσ *pσ) excited state of Ir_2(TMB)_4^(2+) (TMB = 2,5-diisocyano-2,5-dimethylhexane) reacts with hydrogen atom donors to give Ir_2(TMB)_4H_2^(2+) (Ir_2H_2). This d^7-d^7 dihydride has been isolated as a tetraphenylborate salt: v(Ir-H) 1940 cm^(-1), v(Ir-Ir) 136 cm^(-1). [Ir_2(TMB)_4H_2] [B(C_6H_5) _4]_2·CH_3C_6H_5, Ir_2C_(95)H_(114)N_8B_2, crystallizes in the monoclipic system, space group P2_1/c (No. 14), with a = 10.54 (2) Å, b = 31.02 (4) Å, and c = 27.05 (4) Å, β = 91.57 (3)°, V = 8841 (3) Å^3, and Z = 4. The Ir-Ir separation is 2.920 (2) Å, approximately 0.3 Å shorter than Ir-Ir in the d^8 dimer (lr_2) but ~0.1 Å longer than in the diiodide, Ir_2(TMB)_4I_2^(2+). The reaction of Ir_2H_2 with styrene gives Ir_2 and ethylbenzene.\n",
}
@book_section {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/85786,
title ="Long-Range Electron Transfer in Donor (Spacer) Acceptor Molecules and Proteins",
author = "Bowler, Bruce E. and Raphael, Adrienne L.",
pages = "259-322",
month = "January",
year = "1990",
doi = "10.1002/9780470166390.ch5",
issn = "1934483X",
isbn = "9780471503972",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180412-125552522",
note = "© 1990 by John Wiley & Sons, Inc.",
revision_no = "9",
abstract = "[no abstract]",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/24124,
title ="Long-range electron transfer in structurally engineered pentaammineruthenium (histidine-62) cytochrome c",
author = "Bowler, Bruce E. and Meade, Thomas J.",
journal = "Journal of the American Chemical Society",
volume = "111",
number = "23",
pages = "8757-8759",
month = "November",
year = "1989",
doi = "10.1021/ja00205a049 ",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20110620-160433811",
note = "© 1989 American Chemical Society.\n\nReceived July 19, 1989.\n\nWe thank Professor Judith L. Campbell, Dr. Guy Guillemette, Dr. Alfred Gartner, and Professor A. G. Mauk for helpful discussions and Dr. Adrienne Raphael for assistance with the electrochemical (differential pulse polarography) measurements. Large-scale fermentations were done with the aid of Dr. Tom Sutherland at the UCLA Molecular Biology Institute. B.E.B. acknowledges the Medical Research Council (Canada) for a postdoctoral fellowship. This research was supported by National Science Foundation Grant CHE88-14222",
revision_no = "16",
abstract = "In many biological processes, long-range electron transfer (ET) plays a key role. When the three-dimensional structures of proteins are accurately known, use of modified proteins and protein-protein complexes provides an experimental approach to study ET rates between two metal centers. For Ru(His)- modified proteins, the introduction of histidine residues at any desired surface location by site-directed mutagenesis opens the way for systematic investigations of ET pathways.",
}
@book_section {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/85633,
title ="Atom-Transfer Reactivity of Binuclear d^8 Complexes",
author = "Smith, David C. and Gray, Harry B.",
number = "394",
pages = "356-365",
month = "June",
year = "1989",
doi = "10.1021/bk-1989-0394.ch025",
issn = "1947-5918",
isbn = "9780841216280",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180405-103147632",
note = "© 1989 American Chemical Society. \n\nReceived March 8, 1989. Published in print 8 June 1989. \n\nOur research on binuclear complexes has been supported by the Sun Company and by National Science Foundation Grant\nCHE84-19828. This is contribution no. 7897 from the Arthur Amos Noyes Laboratory.",
revision_no = "10",
abstract = "The long-lived ^3(dσ^*pσ) state of binuclear d8 complexes undergoes a variety of reactions. One prominent reaction, photooxidative addition of halocarbons, apparently proceeds by halogen atom transfer rather than outersphere electron transfer. Excited-state hydrogen atom transfer occurs in reactions between several binuclear d^8 complexes and a number of organic and organometallic substrates. Specific results for Pt_2(P_2O_5H_2)_4^(4-) and Ir_2(TMB)_4^(2+) (TMB = 2,5-diisocyano-2,5-dimethylhexane) are discussed. Production of a hole in the dσ* orbital is believed to be an important factor in these photochemical atom-transfer reactions. Electrochemical generation of such a hole produces a highly reactive intermediate that can undergo atom abstraction, thereby yielding net oxidation of an organic substrate. The net reaction is electrocatalytic in metal complex.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/71476,
title ="Pyrophosphito-bridged diplatinum chemistry",
author = "Roundhill, D. Max and Gray, Harry B.",
journal = "Accounts of Chemical Research",
volume = "22",
number = "2",
pages = "55-61",
month = "February",
year = "1989",
doi = "10.1021/ar00158a002",
issn = "0001-4842",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20161025-155913429",
note = "© 1989 American Chemical Society. \n\nReceived April 25, 1988 (Revised Manuscript Received October 24, 1988) \n\nWe thank M. H. Zietlow, E. L. Harvey, D. C. Smith, P. J. Sadler, J. K. Nagle, and E. A. Boudreaux for providing information prior to publication and for many helpful discussions. Our research has been supported by the National Science Foundation (H.B.G.), the Sun Company (H.B.G.), the Petroleum Research Fund, administered by the American Chemical Society (D.M.R.), the Louisiana Board of Regents (D.M.R.), the Croucher Foundation (C.-M.C.), and the University of Hong Kong (C.-M.C.).",
revision_no = "11",
abstract = "[No abstract]",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/54187,
title ="Effects of buried ionizable amino acids on the reduction potential of recombinant myoglobin",
author = "Varadarajan, Raghavan and Zewert, Thomas E.",
journal = "Science",
volume = "243",
number = "4887",
pages = "69-72",
month = "January",
year = "1989",
doi = "10.1126/science.2563171",
issn = "0036-8075",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150128-121300760",
note = "© 1989 American Association for the Advancement of Science.\n\n1 September 1988; Accepted 1 November 1988.\n\nWe thank W. R. Ellis, Jr., and H. C. Andersen for helpful discussions. Supported in part by NIH grant GM 27738 (S.G.B.), a Presidential Young Investigator Award to S.G.B. (matching funds from Monsanto Corp.), and NIH grant DK 19038 (H.B.G.). This is contribution No. 7853 from the Arthur Amos Noyes Laboratory.",
revision_no = "9",
abstract = "The temperature dependences of the reduction potentials (E°') of wild-type human myoglobin (Mb) and three site-directed mutants have been measured by the use of thin-layer spectroelectrochemistry. Residue Val68, which is in van der Waals contact with the heme in Mb, has been replaced by Glu, Asp, and Asn. The changes in E degrees' and the standard entropy (ΔS°') and enthalpy (ΔH°') of reduction in the mutant proteins were determined relative to values for wild type; the change in E°' at 25 °C was about -200 millivolts for the Glu and Asp mutants, and about -80 millivolts for the Asn mutant. At pH 7.0, reduction of Fe(III) to Fe(II) in the Glu and Asp mutants is accompanied by uptake of a proton by the protein. These studies demonstrate that Mb can tolerate substitution of a buried hydrophobic group by potentially charged and polar residues and that such amino acid replacements can lead to substantial changes in the redox thermodynamics of the protein.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/24137,
title ="Distance dependence of photoinduced long-range electron transfer in zinc/ruthenium-modified myoglobins",
author = "Axup, Andrew W. and Albin, Michael",
journal = "Journal of the American Chemical Society",
volume = "110",
number = "2",
pages = "435-439",
month = "January",
year = "1988",
issn = "0002-7863",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20110620-160435945",
note = "© 1988 American Chemical Society.\nReceived May 8, 1987.\nPublication Date: January 1988.\nContribution No. 7588 from the Arthur Amos Noyes Laboratory, California Institute of\nTechnology, Pasadena, California 91125.\nWe thank Charlie Lieber, Jenny Karas,\nWalther Ellis, Lome Reid, Jose Onuchic, David Beratan, A. Kuki,\nHarvey Schugar, R. A. Marcus, and Jay Winkler for helpful\ndiscussions. A.W.A. acknowledges a fellowship from the Fannie\nand John Hertz Foundation. S.L.M. acknowledges a fellowship\nfrom AT&T Bell Laboratories. This research was supported by\nNational Science Foundation Grants CHE85-18793 and\nCHE85-09637.\n",
revision_no = "16",
abstract = "An experimental investigation of the distance dependence of long-range electron transfer in zinc/ruthenium-modified myoglobins has been performed. The modified proteins were prepared by substitution of zinc mesoporphyrin IX diacid (ZnP) for the heme in each of four previously characterized pentaammineruthenium(III) (a_5Ru;a = NH_3) derivatives of sperm whale myoglobin (Mb): a_5Ru(His-48)Mb, a_5Ru(His-12)Mb, a_5Ru(His-116)Mb, a_5Ru(His-81)Mb. Electron transfer from the ZnP triplet excited state (^3ZnP*) to Ru^3+, ^3ZnP*-Ru^3+ → ZnP^+-Ru^2+ (ΔE° ~ 0.8V) was measured by time-resolved transient absorption spectroscopy: rate constants (k_f) are 7.0 × 10^4 (His-48), 1.0 × 10^2 (His-12), 8.9 × 10^1 (His-116), and 8.5 × 10^1 (His-81) s^-1 at 25 °C. Activation enthalpies calculated from the temperature dependences of the electron-transfer rates over the range 5-40 °C are 1.7 ± 1.6 (His-48), 4.7 ± 0.9 (His-12), 5.4 ± 0.4 (His-116), and 5.6 ± 2.5 (His-81) kcal mol^-1. Electron-transfer distances (d = closest ZnP edge to a_5Ru(His) edge; angstroms) were calculated to fall in the following ranges: His-48, 11.8-16.6; His-12, 21.5-22.3; His-116, 19.8-20.4; His-81, 18.8-19.3. The rate-distance equation is k_f = 7.8 × 10^8 exp[-0.9l(d - 3)] s^-1 . The data indicate that the ^3ZnP*-Ru(His-12)^3+ electronic coupling may be enhanced by an intervening tryptophan (Trp-14). ",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/32135,
title ="Metal-Oxo Photo-oxidants, Photochemistry and Photophysics of trans-[Os^(VI)(tmc)(O)_2]^(2+)(tmc = 1,4,8,11-tetramethyl-1,4,8,11-tetra-azacyclotetradecane) and trans-[Os^(VI)(CN)_4(O)_2]^(2-)",
author = "Che, Chi-Ming and Yam, Vivian Wing-Wah",
journal = "Journal of the Chemical Society. Chemical Communications",
volume = "1987",
number = "12",
pages = "948-949",
month = "January",
year = "1987",
doi = "10.1039/C39870000948 ",
issn = "0022-4936",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20120627-100742357",
note = "© 1987 Royal Society of Chemistry.\n\nReceived 11th February 1987; Com. 183.\nWe thank Dr. Janet L. Marshall for experimental assistance.\nSupport from the Croucher Foundation (C. M. C. and V. W.-W. Y.) and National Science Foundation Grant\nCHE84-19828 (H. B. G.) is gratefully acknowledged. This is\ncontribution No. 7573 from the Arthur Amos Noyes Laboratory.\nV. W.-W. Y. is a Croucher Foundation and Li Po Chun\nScholar.\n",
revision_no = "17",
abstract = "trans-[Os^(VI)(tmc)(O)_2]^(2+)(tmc = 1,4,8,11-tetramethyl-1,4,8,11-tetra-azacyclotetradecane) and trans-[Os^(VI)(CN)_4(O)_2]^(2-) are emissive in the solid state and in fluid solutions at room temperature (τ~ 1.0–1.5 µs); the (^3)E_g state of trans-[Os^(VI)(tmc)(O)_2]^(2+) is a powerful one-electron oxidant {[Os^(VI)(O)_2]^(2+) + e^– → [Os^V (O)_2]+, E^0_f > 2.0 V vs. normal hydrogen electrode} in aqueous solution, reacting with PPh3 and ((PhCH_2)_2)S to give O=PPh_3 and ((PhCH_2)_2)S=O, respectively.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/24127,
title ="Long-range electron transfer in heme proteins",
author = "Mayo, Stephen L. and Ellis, Walther R., Jr.",
journal = "Science",
volume = "233",
number = "4767",
pages = "948-952",
month = "August",
year = "1986",
doi = "10.1126/science.3016897",
issn = "0036-8075",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20110620-160434289",
note = "© 1986 American Association for the Advancement of Science. \n\n Supported by grants from the National Science Foundation (CHE85-09637 and CHE85-18793). S.L.M. is an AT&T Bell Laboratories predoctoral fellow (1983 to the present). R.J.C. held a postdoctoral fellowship from the Natural Sciences and Engineering Research Council of Canada during 1982-84. H.B.G. was Visiting Miller Research Professor at the Department of Chemistry, University of California, Berkeley, when the manuscript was completed. We thank the following colleagues for helpful discussion: K. M. Yocom, J. R. Winkler, E. Bordignon, D. G. Nocera, J. B. Shelton, J. R. Shelton, W. A. Schroeder, J. N. Onuchic, G. Worosila, S. S. Isied, B. M. Hoffman, G. L. McLendon, R. A. Scott, A. G. Mauk, M. R. Mauk, N. S. Hush, R. A. Marcus, N. Sutin, J. J. Hopfield, D. N. Beratan, G. L. Closs, M. Smith, G. Pielak, B. D. Olafson, J. L. Campbell, J. H. Richards, W. A. Goddard III, I. Pecht, A. W. Axup, A. A. da Gama, M. Albin, J. H. Dawson, H. Taube, J. R. Miller, B. G. Malmstrom, W. R. Scheidt, and S. Larsson. Contribution 7334 from the Arthur Amos Noyes Laboratory.",
revision_no = "18",
abstract = "Kinetic experiments have conclusively shown that electron transfer can take place over large distances (greater than 10 angstroms) through protein interiors. Current research focuses on the elucidation of the factors that determine the rates of long-range electron-transfer reactions in modified proteins and protein complexes. Factors receiving experimental and theoretical attention include the donor-acceptor distance, changes in geometry of the donor and acceptor upon electron transfer, and the thermodynamic driving force. Recent experimental work on heme proteins indicates that the electron-transfer rate falls off exponentially with donor-acceptor distance at long range. The rate is greatly enhanced in proteins in which the structural changes accompanying electron transfer are very small.",
}
@book_section {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/85623,
title ="Photochemistry of Dinuclear d^8-d^8 Iridium and Platinum Complexes",
author = "Marshall, Janet L. and Stiegman, Albert E.",
number = "307",
pages = "166-176",
month = "April",
year = "1986",
doi = "10.1021/bk-1986-0307.ch012",
issn = "1947-5918",
isbn = "9780841209718",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180405-071623282",
note = "© 1986 American Chemical Society. \n\nReceived November 8, 1985. Published in print 30 April 1986.\n\nJ. L. M. thanks the Sun Co. for a graduate fellowship. This research was supported by National Science Foundation\nGrant CHE84-19828.",
revision_no = "10",
abstract = "The long-lived (^3B_2 and ^3A_(2u)) excited states of the d8-d8 dimers [Ir(μ-pz)(COD)]_2 and Pt_2(pop)_4^(4-), respectively, undergo a variety of photochemical reactions (pzH is pyrazole; COD is 1,5-cyclooctadiene; pop is P_2O_5H_2^(2-), bridging pyrophosphite). Electron transfer reactions to one-electron acceptors such as pyridinium cations or substituted benzophenones are quite facile with acceptors that have reduction potentials as negative as -2.0 V vs. NHE. With halocarbon acceptors, d^7-d^7 oxidative addition products are obtained. Several organic substrates with relatively weak C-H bonds react with the triplet (dσ^*pσ) excited state of Pt_2(pop)_4^(4-) by H-atom transfer.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/11073,
title ="Long-range electron-transfer in blue copper proteins\n",
author = "Gray, Harry B.",
journal = "Chemical Society Reviews",
volume = "15",
number = "1",
pages = "17-30",
month = "March",
year = "1986",
issn = "0306-0012",
url = "https://resolver.caltech.edu/CaltechAUTHORS:GRAcsr86",
note = "© 1986 Royal Society of Chemistry. \n\nDelivered at a Symposium of the Dalton Division of the Royal Society of Chemistry, Scientific Societies’ Lecture Theatre, London, on 14th March, 1985. \n\nI acknowledge with thanks the hospitality of the Department of Chemistry, University of California, Berkeley, where my Centenary Lecture manuscript was completed. Thanks also are due to my co-workers, especially N.M. Kostic, R. Margalit, C.-M. Che, D.F. Blair, H.-J. Chiang, I. Pecht, J.B. Shelton, J.R. Shelton, W.A. Schroeder, B.S. Brunschwig, P.J. DeLaive, A.M. English, M. Goldberg, S.L. Mayo, N. Sutin, B.G. Malmstrom, and W.R. Ellis, Jr., for their many contributions to the work I discussed in the lecture. Research on copper proteins at the California Institute of Technology is supported by National Institutes of Health Grant AM19038; this is Contribution No. 7313 from the Arthur Amos Noyes Laboratory.",
revision_no = "15",
abstract = "It is widely recognized that blue copper proteins function as electron-transfer agents in biological systems.(1-10) Plastocyanin, for example, which is one of the most thoroughly studied of all the blue copper proteins, is a key component of the electron-transfer apparatus in the chloroplasts of green leaves. In its oxidized form, here referred to as the Cu2 + state, it is intensely blue, because of 600 nm absorption attributable to charge transfer from a cysteine sulphur to the copper. The review by Sykes,(9) based on his Tilden Lecture, is an excellent place to read about the structure and properties of plastocyanin.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/24120,
title ="Kinetics and mechanisms of electron transfer between blue copper proteins and electronically excited chromium and ruthenium polypyridine complexes",
author = "Brunschwig, Bruce S. and DeLaive, Patricia J.",
journal = "Inorganic Chemistry",
volume = "24",
number = "23",
pages = "3743-3749",
month = "November",
year = "1985",
doi = "10.1021/ic00217a010 ",
issn = "0020-1669",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20110620-160433152",
note = "© 1985 American Chemical Society. \n\nReceived January 28, 1985. Publication Date: November 1985. \n\nResearch at the California Institute of Technology was supported by National Institutes of Health Grant AM19038, and research at Brookhaven National Laboratory was carried out under contract DE-AC02-76CH00016 with the U.S. Department of Energy and supported by its Division of Chemical Sciences and Office of Basic Energy Sciences. A.M.E. acknowledges a postdoctoral fellowship from the NSERC (1980-1981). S.L.M. thanks AT&T Bell Laboratories for a predoctoral fellowship (1983-present). We wish to acknowledge helpful discussions with Dr. C. Creutz and the assistance of J. Horwitz of the University of California at Santa Cruz and Dr. R. Humphry-Baker of L'Ecole Polytechnique Fiderale de Lausanne during the early stages of this work.",
revision_no = "16",
abstract = "The kinetics of the quenching of the long-lived excited states of CrL_3^(3+) and RuL_3^(2+) complexes (L is 1,10-phenanthroline and 2,2’-bipyridine or substituted derivatives) by the copper proteins plastocyanin, azurin, and stellacyanin have been studied in aqueous solution. The rate constants for quenching by the Cu(I) proteins approach a limiting value of ~10^(6) s^(-1) at high protein concentration. The kinetic behavior for plastocyanin is discussed in terms of a model in which the metal complex binds at a remote site 10-12 Å from the copper center. The model allows for electron transfer both from this remote site and by attack of the metal complex adjacent to the copper center. The results show that at low protein concentration the adjacent pathway is about 10 times faster than the remote pathway. The rate constant for the intramolecular electron transfer from the remote site is consistent with the value expected on the basis of theoretical calculations.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/955,
title ="Preparation and characterization of pentaammineruthenium-(histidine-83)azurin: Thermodynamics of intramolecular electron transfer from ruthenium to copper",
author = "Margalit, Ruth and Kostić, Nenad M.",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
volume = "81",
number = "20",
pages = "6554-6558",
month = "October",
year = "1984",
doi = "10.1073/pnas.81.20.6554",
issn = "0027-8424",
url = "https://resolver.caltech.edu/CaltechAUTHORS:MARpnas84",
note = "© 1984 by the National Academy of Sciences. \n\nContributed by Harry B. Gray, May 29, 1984. \n\nWe thank Stephen Mayo for Fig. 3, Vance Morgan for help with the CD measurements, Tin Wu Tang for assistance with cyclic voltammetry, and Ting Lin Kao for a sample of Na[Co(EDTA)]. Helpful comments were provided by Walther Ellis, Karl Freed, Michel Goldberg, Brian Hoffman, John Hopfield, Noel Hush, Sven Larsson, George McLendon, Bo Malmstrom, and Rudy Marcus. This research was supported by National Institutes of Health Grants AM19038 (H.B.G.) and HL02558 (W.A.S.). This is contribution no. 7033 from the Arthur Amos Noyes Laboratory. \n\nThe publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked \"advertisement\" in accordance with 18 U.S.C. §1734 solely to indicate this fact.",
revision_no = "11",
abstract = "The reaction between a5RuH2O2+ (a is NH3) and Pseudomonas aeruginosa azurin at pH 7, followed by oxidation, yields a5Ru(His-83)3+-azurin(Cu2+) as the major product. Spectroscopic measurements (UV-visible, CD, EPR, and resonance Raman) indicate that the native structure is maintained in the modified protein. The site of ruthenium binding (His-83) was identified by peptide mapping. The a5RuHis/Cu ratio in the modified protein, determined from the EPR spectrum, is 1:1, and the reduction potentials (vs. normal hydrogen electrode, pH 7.0, 25 degrees C) are blue copper (Cu2+/1+), 320 ± 2 mV; a5Ru(His-83)3+/2+, 50 ± 10 mV. From measurements of the reduction potentials at several temperatures in the 5-40 degrees C range, delta-H degrees for intramolecular Ru2+ --> Cu2+ electron transfer was estimated to be -12.4 kcal mol(-1) (1 cal = 4.184 J). Analysis of kinetic data in light of the electron transfer exothermicity indicates that the reorganizational enthalpy of the blue copper site can be no larger than 7.1 kcal mol(-1).",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/53837,
title ="The 1983 Nobel Prize in Chemistry",
author = "Gray, Harry B. and Collman, James P.",
journal = "Science",
volume = "222",
number = "4627",
pages = "986-987",
month = "December",
year = "1983",
doi = "10.1126/science.222.4627.986",
issn = "0036-8075",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150116-140936041",
note = "© 1983 American Association for the Advancement of Science.",
revision_no = "11",
abstract = "Henry Taube has been selected to\nreceive the 1983 Nobel Prize in Chemistry\nfor his pioneering work on the mechanisms\nof inorganic oxidation-reduction\n(redox) reactions. Taube was born in\nNeudorf, Saskatchewan, on 30 November\n1915, and he received B.S. (1935)\nand M.S. (1937) degrees at the University\nin Saskatoon. He moved to Berkeley\nto do his doctoral research (Ph.D., 1940)\nwith W. C. Bray, and he became a U.S.\ncitizen in 1941. He has held academic\nappointments at Cornell (1941 to 1946),\nChicago (1946 to 1961), and Stanford\n(since 1962) and is now the Marguerite\nBlake Wilbur Professor of Chemistry at\nStanford.",
}
@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/54522,
title ="Heme-Heme Orientation and Electron Transfer Kinetic Behavior of Multisite Oxidation-Reduction Enzymes",
author = "Makinen, Marvin W. and Schichman, Steven A.",
journal = "Science",
volume = "222",
number = "4626",
pages = "929-931",
month = "November",
year = "1983",
doi = "10.1126/science.6415814 ",
issn = "0036-8075",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20150209-090647293",
note = "© 1983 American Association for the Advancement of Science.\n13 June 1983; accepted 21 September 1983.\n\nWe thank Dr. T. Takano for providing crystals of cytochrome cd_1. Supported by NSF grant PCM 77-13479 (M.W.M.), American Heart Association grant-in-aid 77378 (M.W.M.), NSF grant CHE 82-18502 (H.B.G.), and NIH training grant 1-T32-HD-07009 (S.A.S.). This is contribution No. 6774 from the Arthur Amos Noyes Laboratory.",
revision_no = "12",
abstract = "Analysis of the polarized single-crystal absorption spectra of cytochrome cd1 of Pseudomonas aeruginosa shows that the heme c and heme d_1 groups in each subunit are oriented perpendicularly to each other in both oxidized and reduced forms of the enzyme. These results, together with those of previous kinetic studies, indicate that a perpendicular heme-heme orientation may be an important factor in specifying kinetically slow steps in a sequential series of electron transfer reactions.",
}
@book_section {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/85615,
title ="Oxidation-Reduction Photochemistry of Polynuclear Complexes in Solution",
author = "Nocera, Daniel G. and Maverick, Andrew W.",
number = "211",
pages = "21-33",
month = "March",
year = "1983",
doi = "10.1021/bk-1983-0211.ch002",
issn = "1947-5918",
isbn = "9780841207639",
url = "https://resolver.caltech.edu/CaltechAUTHORS:20180404-144801568",
note = "© 1983 American Chemical Society. \n\nReceived September 24, 1982. Published in print 3 March 1983. \n\nD. MacKenzie assisted with the (Bu_4N)_2M_6X_(14) emission lifetime measurements. Research at the California Institute of Technology was supported by National Science Foundation Grants CHE78-10530 and CHE81-20419. This is Contribution No. 6703 from the Arthur Amos Noyes Laboratory.",
revision_no = "11",
abstract = "Three classes of polynuclear complexes containing metal-metal bonds possess emissive excited states that undergo oxidation-reduction reactions in solution: the prototypes are Re_2Cl^(2-)_8(d^4·d^4), Pt_2(P_2O_5H_2)^(4-)_4 (d^8·d^8), and Mo_6Cl^(2-)_(14)(d^4)6. Two-electron oxidations of Re_2Cl^(2-)_8 and Pt_2(P_2O_5H_2)^(4-)_4 have been achieved by one-electron acceptor quenching of the excited complexes in the presence of Cl^-, followed by one-electron oxidation of the Cl^--trapped mixed-valence species. T