[ { "id": "authors:m44b8-d8074", "collection": "authors", "collection_id": "m44b8-d8074", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:UNGrsi98", "type": "article", "title": "Etched chalcogenide fibers for near-field infrared scanning microscopy", "author": [ { "family_name": "Unger", "given_name": "M. A.", "clpid": "Unger-M-A" }, { "family_name": "Kossakovski", "given_name": "D. A.", "clpid": "Kossakovski-D-A" }, { "family_name": "Kongovi", "given_name": "R.", "clpid": "Kongovi-R" }, { "family_name": "Beauchamp", "given_name": "J. L.", "orcid": "0000-0001-8839-4822", "clpid": "Beauchamp-J-L" }, { "family_name": "Baldeschwieler", "given_name": "J. D.", "clpid": "Baldeschwieler-J-D" }, { "family_name": "Palanker", "given_name": "D. V.", "clpid": "Palanker-D-V" } ], "abstract": "Typical infrared transmitting fibers comprise a chalcogenide core surrounded by a sulfur-selenide cladding, which is in turn coated with a polymer such as polyamide. For use in a near-field scanning infrared microscope (NSIM), such infrared-transmitting fibers must be tapered to a sharp point. Sharper points allow smaller apertures, which allow higher resolution. The light throughput of the probe depends on the length of the taper region: the longer the taper length, the further the infrared radiation must propagate through a waveguide smaller than its wavelength. Thus, shorter taper lengths should give higher light throughput. We describe a method for etching chalcogenide fibers to submicron points by simple chemical means. Methods are described for removal of the polyamide coating, stripping of the SSe cladding surrounding the core, and etching the chalcogenide fiber core to a sharp point. Removal of the polyamide coating is most easily accomplished by dissolution in 4-Chloro-1-butanol. The SSe cladding is removed by soaking the fiber in 0.1 M NaOH overnight. The chalcogenide core is tapered to a sharp point by immersion in a two-phase etching system, where the top phase is an inert organic solvent, and the bottom phase is a strong oxidant. Fibers both with and without cladding have been tapered. The resulting fibers have a taper length on the order of the core diameter, and terminate with a submicron end radius of curvature. The potential for use in a NSIM, as well as other uses, is discussed.", "doi": "10.1063/1.1149045", "issn": "0034-6748", "publisher": "American Institute of Physics", "publication": "Review of Scientific Instruments", "publication_date": "1998-08", "series_number": "8", "volume": "69", "issue": "8", "pages": "2988-2993" }, { "id": "authors:vnz13-nje82", "collection": "authors", "collection_id": "vnz13-nje82", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:MISpnas96", "type": "article", "title": "Evidence for the role of proteoglycans in cation-mediated gene transfer", "author": [ { "family_name": "Mislick", "given_name": "Kimberly A.", "clpid": "Mislick-K-A" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "We report evidence that gene complexes, consisting of polycations and plasmid DNA enter cells via binding to membrane-associated proteoglycans. Treatment of HeLa cells with sodium chlorate, a potent inhibitor of proteoglycan sulfation, reduced luciferase expression by 69%. Cellular treatment with heparinase and chondroitinase ABC inhibited expression by 78% and 20% with respect to control cells. Transfection was dramatically inhibited by heparin and heparan sulfate and to a smaller extent by chondroitan sulfate B. Transfection of mutant, proteoglycan deficient Chinese hamster ovary cells was 53 x lower than of wild-type cells. For each of these assays, the intracellular uptake of DNA at 37 degrees C and the binding of DNA to the cell membrane at 4 degrees C was impaired. Preliminary transfection experiments conducted in mutant and wild-type Chinese hamster ovary cells suggest that transfection by some cationic lipids is also proteoglycan dependent. The variable distribution of proteoglycans among tissues may explain why some cell types are more susceptible to transfection than others.", "doi": "10.1073/pnas.93.22.12349", "pmcid": "PMC37994", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "1996-10-29", "series_number": "22", "volume": "93", "issue": "22", "pages": "12349-12354" }, { "id": "authors:jgg8q-y8p40", "collection": "authors", "collection_id": "jgg8q-y8p40", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:LAMjmr96", "type": "article", "title": "Surface microstructure of Zr41.25Ti13.75Cu12.5Ni10.0Be22.5, a\n bulk metallic glass", "author": [ { "family_name": "LaMadrid", "given_name": "M. A.", "clpid": "LaMadrid-M-A" }, { "family_name": "O'Connor", "given_name": "S. D.", "clpid": "O'Connor-S-D" }, { "family_name": "Peker", "given_name": "A.", "clpid": "Peker-A" }, { "family_name": "Johnson", "given_name": "W. L.", "clpid": "Johnson-W-L" }, { "family_name": "Baldeschwieler", "given_name": "J. D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "The surface of Zr41.25Ti13.75Cu12.5Ni10.0Be22.5, a bulk metallic glass prepared by RF induction melting, has been imaged using atomic force microscopy. The untreated surfaces were very smooth; features were no higher than 3 nm over a 10 x 10 \u00b5m region, comparable to many polished surfaces. Two types of microstructure were also observed; periodic striations forming either a striped or a checkered structure were present, with wavelengths between 1 and 2 \u00b5m, and amplitude of approximately 2 nm; in other cases, \"cracked mud\"-like patterns were observed. These microstructures could be related to strain-induced surface roughening; preliminary calculations are presented that are consistent with this hypothesis.", "issn": "0884-2914", "publisher": "Journal of Materials Research", "publication": "Journal of Materials Research", "publication_date": "1996-06-01", "series_number": "6", "volume": "11", "issue": "6", "pages": "1494-1499" }, { "id": "authors:m3jhq-8va12", "collection": "authors", "collection_id": "m3jhq-8va12", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:UNGjvstb96", "type": "article", "title": "Tip\u2013sample interactions: Extraction of single molecular pair potentials from force curves", "author": [ { "family_name": "Unger", "given_name": "Marc A.", "clpid": "Unger-M-A" }, { "family_name": "O'Connor", "given_name": "Stephen D.", "clpid": "O'Connor-S-D" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "This article describes a method for extracting the true tip\u2013sample potential from an experimental force curve in atomic force microscopy. This potential is not the negative integral of the force curve. Rather, the potential is a more complicated function of the force curve and cantilever spring constant. If information about the shape of the tip is known, a decorrelation may be performed to extract molecular pair potentials from the total tip\u2013sample potential. Applications and limitations of this method are discussed.", "doi": "10.1116/1.589085", "issn": "1071-1023", "publisher": "American Vacuum Society", "publication": "Journal of Vacuum Science and Technology B", "publication_date": "1996-03", "series_number": "2", "volume": "14", "issue": "2", "pages": "1302-1307" }, { "id": "authors:b1chv-smf33", "collection": "authors", "collection_id": "b1chv-smf33", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:OCOjvstb96", "type": "article", "title": "Gamble mode: Resonance contact mode in atomic force microscopy", "author": [ { "family_name": "O'Connor", "given_name": "S. D.", "clpid": "O'Connor-S-D" }, { "family_name": "Gamble", "given_name": "R. C.", "clpid": "Gamble-R-C" }, { "family_name": "Eby", "given_name": "R. K.", "clpid": "Eby-R-K" }, { "family_name": "Baldeschwieler", "given_name": "J. D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "Active noise reduction has been accomplished in atomic force microscopy by applying a high frequency, low amplitude vibration to the cantilever while it is in contact with a surface. The applied excitation (>~ 200 kHz; ~ 1 nm) is acoustically coupled to the tip and dampens the resonance Q factors of the system. The applied frequency is well above the bandwidth of the acquisition system (50 kHz). We call this mode \"gamble mode\" or \"resonance contact.\"", "doi": "10.1116/1.588729", "issn": "1071-1023", "publisher": "American Vacuum Society", "publication": "Journal of Vacuum Science and Technology B", "publication_date": "1996-03", "series_number": "2", "volume": "14", "issue": "2", "pages": "852-855" }, { "id": "authors:3gker-frd42", "collection": "authors", "collection_id": "3gker-frd42", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:OCOrsi96", "type": "article", "title": "Noise reduction in atomic force microscopy: Resonance contact mode", "author": [ { "family_name": "O'Connor", "given_name": "S. D.", "clpid": "O'Connor-S-D" }, { "family_name": "Gamble", "given_name": "R. C.", "clpid": "Gamble-R-C" }, { "family_name": "Eby", "given_name": "R. K.", "clpid": "Eby-R-K" }, { "family_name": "Baldeschwieler", "given_name": "J. D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "Noise reduction has been accomplished in atomic force microscopy by applying a high frequency, low amplitude vibration to the cantilever while it is in contact with a surface. The applied excitation (>~200 kHz; ~1 nm) is acoustically coupled to the tip and dampens the resonance Q factors of the system. The applied frequency is well above the bandwidth of the acquisition system (50 kHz). We call this mode \"resonance contact\" mode. The nonlinear behavior of the tip\u2013sample interaction allows the high frequency excitation to effectively broaden the frequency response of the system resonances.", "doi": "10.1063/1.1146602", "issn": "0034-6748", "publisher": "Review of Scientific Instruments", "publication": "Review of Scientific Instruments", "publication_date": "1996-02-01", "series_number": "2", "volume": "67", "issue": "2", "pages": "393-396" }, { "id": "authors:pp38a-93x40", "collection": "authors", "collection_id": "pp38a-93x40", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170905-095408869", "type": "article", "title": "Transfection of Folate-Polylysine DNA Complexes: Evidence for Lysosomal Delivery", "author": [ { "family_name": "Mislick", "given_name": "Kimberly A.", "clpid": "Mislick-K-A" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" }, { "family_name": "Kayyem", "given_name": "Jon F.", "clpid": "Kayyem-J-F" }, { "family_name": "Meade", "given_name": "Thomas J.", "clpid": "Meade-T-J" } ], "abstract": "We are utilizing the folate receptor for the intracellular delivery of DNA. In this study, a folate-poly-L-lysine (FPLL) conjugate was synthesized and equilibrated with plasmid DNA encoding the firefly luciferase gene. The FPLL-DN_A complexes were added to KB cells treated with chloroquine. Luciferase activity of cells incubated with FPLL-DNA was 6-fold higher than of cells exposed to poly-L-lysine. (PLL)-DNA. The addition of free folic acid competitively inhibited the enhancement of gene\nexpression. Removal of chloroquine from the media significantly inhibited transfection efficiency of\nFPLL-DNA complexes. We conclude that FPLL-DNA complexes are delivered into KB cells via folate receptor-mediated endocytosis and likely follow a lysosomal pathway into the cytoplasm.", "doi": "10.1021/bc00035a002", "issn": "1043-1802", "publisher": "American Chemical Society", "publication": "Bioconjugate Chemistry", "publication_date": "1995-09-01", "series_number": "5", "volume": "6", "issue": "5", "pages": "512-515" }, { "id": "authors:072tw-jxw12", "collection": "authors", "collection_id": "072tw-jxw12", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:STIpnas95", "type": "article", "title": "Real-time detection of DNA hybridization and melting on oligonucleotide arrays by using optical wave guides", "author": [ { "family_name": "Stimpson", "given_name": "Don I.", "clpid": "Stimpson-D-I" }, { "family_name": "Hoijer", "given_name": "Joanell V.", "clpid": "Hoijer-J-V" }, { "family_name": "Hsieh", "given_name": "Wangting", "clpid": "Hsieh-Wangting" }, { "family_name": "Jou", "given_name": "Cynthia", "clpid": "Jou-Cynthia" }, { "family_name": "Gordon", "given_name": "Julian", "clpid": "Gordon-J" }, { "family_name": "Theriault", "given_name": "Tomas", "clpid": "Theriault-T" }, { "family_name": "Gamble", "given_name": "Ronald", "clpid": "Gamble-R-C" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "The challenge of the Human Genome Project is to increase the rate of DNA sequence acquisition by two orders of magnitude to complete sequencing of the human genome by the year 2000. The present work describes a rapid detection method using a two-dimensional optical wave guide that allows measurement of real-time binding or melting of a light-scattering label on a DNA array. A particulate label on the target DNA acts as a light-scattering source when illuminated by the evanescent wave of the wave guide and only the label bound to the surface generates a signal. Imaging/visual examination of the scattered light permits interrogation of the entire array simultaneously. Hybridization specificity is equivalent to that obtained with a conventional system using autoradiography. Wave guide melting curves are consistent with those obtained in the liquid phase and single-base discrimination is facile. Dilution experiments showed an apparent lower limit of detection at 0.4 nM oligonucleotide. This performance is comparable to the best currently known fluorescence-based systems. In addition, wave guide detection allows manipulation of hybridization stringency during detection and thereby reduces DNA chip complexity. It is anticipated that this methodology will provide a powerful tool for diagnostic applications that require rapid cost-effective detection of variations from known sequences.", "doi": "10.1073/pnas.92.14.6379", "pmcid": "PMC41521", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "1995-07-04", "series_number": "14", "volume": "92", "issue": "14", "pages": "6379-6383" }, { "id": "authors:tm3x5-8cy84", "collection": "authors", "collection_id": "tm3x5-8cy84", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:BASjap94", "type": "article", "title": "Imaging spectroscopy with the atomic force microscope", "author": [ { "family_name": "Baselt", "given_name": "David R.", "clpid": "Baselt-D-R" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "Force curve imaging spectroscopy involves acquiring a force-distance curve at each pixel of an atomic force microscope image. Processing of the resulting data yields images of sample hardness and tip-sample adhesion. These images resemble Z modulation images and the sum of forward and reverse friction images, respectively, and like them exhibit a number of potentially misleading contrast mechanisms. In particular, XY tip motion has a pronounced effect on hardness images and the meniscus force on adhesion images.", "doi": "10.1063/1.357150", "issn": "0021-8979", "publisher": "Journal of Applied Physics", "publication": "Journal of Applied Physics", "publication_date": "1994-07-01", "series_number": "1", "volume": "76", "issue": "1", "pages": "33-38" }, { "id": "authors:scg81-s4c24", "collection": "authors", "collection_id": "scg81-s4c24", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130502-074554974", "type": "article", "title": "Topology of synthetic, boron-doped diamond by scanning tunneling microscopy", "author": [ { "family_name": "Baker", "given_name": "Shenda M.", "clpid": "Baker-S-M" }, { "family_name": "Rossman", "given_name": "George R.", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "Scanning tunneling microscopy (STM) studies were performed on a large, boron-doped, synthetic diamond crystal in order to examine its surface morphology and growth characteristics. This single crystal synthetic diamond should better mimic naturally grown diamonds than thin diamond films which may be affected by the substrate or the deposition technique used. The synthetic diamond is shown to exhibit microscopic features similar to the macroscopic features observed on natural diamonds indicating similar growth and/or defect properties. The ability to obtain adequate current for this STM study is a result of the high boron content in the synthetic diamond, which is much higher than that of natural diamonds.", "doi": "10.1016/0925-9635(94)90037-X", "issn": "0925-9635", "publisher": "Elsevier", "publication": "Diamond and Related Materials", "publication_date": "1994-01", "series_number": "1-2", "volume": "3", "issue": "1-2", "pages": "94-97" }, { "id": "authors:30fyw-zfm72", "collection": "authors", "collection_id": "30fyw-zfm72", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:BAKjap93", "type": "article", "title": "Observation of surface charge screening and Fermi level pinning on a synthetic, boron-doped diamond", "author": [ { "family_name": "Baker", "given_name": "Shenda M.", "clpid": "Baker-S-M" }, { "family_name": "Rossman", "given_name": "George R.", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "Spectroscopic current-voltage (I-V) curves taken with a scanning tunneling microscope on a synthetic, boron-doped diamond single crystal indicate that the diamond, boiled in acid and baked to 500 \u00b0C in vacuum, does not exhibit ideal Schottky characteristics. These I-V curves taken in ultrahigh vacuum do not fit the traditional theory of thermionic emission; however, the deviation from ideal can be accounted for by charge screening at the diamond surface. At ambient pressure, the I-V curves have a sharp threshold voltage at 1.7 eV above the valence band edge indicating pinning of the Fermi energy. This measurement is in excellent agreement with the 1/3 band gap rule of Mead and Spitzer [Phys. Rev. 134, A713 (1964)].", "doi": "10.1063/1.354445", "issn": "0021-8979", "publisher": "Journal of Applied Physics", "publication": "Journal of Applied Physics", "publication_date": "1993-09-15", "series_number": "6", "volume": "74", "issue": "6", "pages": "4015-4019" }, { "id": "authors:cqyn0-m2116", "collection": "authors", "collection_id": "cqyn0-m2116", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:BASrsi93b", "type": "article", "title": "Digital signal processor control of scanned probe microscopes", "author": [ { "family_name": "Baselt", "given_name": "David R.", "clpid": "Baselt-D-R" }, { "family_name": "Clark", "given_name": "Steven M.", "clpid": "Clark-S-M" }, { "family_name": "Youngquist", "given_name": "Michael G.", "clpid": "Youngquist-M-G" }, { "family_name": "Spence", "given_name": "Charles F.", "clpid": "Spence-C-F" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "Digital signal processors have made it possible to control scanned probe microscopes using straightforward software emulations of analog circuits. Using a system consisting of a commercially available digital signal processor board interfaced to analog I/O, we have developed algorithms for self-optimizing feedback, raster generation (with hysteresis correction, sample tilt compensation, and scan rotation), lock-in detection, and automatic tip-sample approach. We also discuss an instruction parser that takes advantage of the digital architecture to allow automatic operation for extended periods.", "doi": "10.1063/1.1144462", "issn": "0034-6748", "publisher": "American Institute of Physics", "publication": "Review of Scientific Instruments", "publication_date": "1993-07", "series_number": "7", "volume": "64", "issue": "7", "pages": "1874-1882" }, { "id": "authors:ymhz4-eas27", "collection": "authors", "collection_id": "ymhz4-eas27", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:CLArsi93", "type": "article", "title": "A high performance scanning force microscope head design", "author": [ { "family_name": "Clark", "given_name": "Steven M.", "clpid": "Clark-S-M" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "A stable and highly sensitive scanning force microscope head design is presented. The head provides an implementation of the optical lever detection method in which mechanical vibration noise has been minimized.", "doi": "10.1063/1.1144141", "issn": "0034-6748", "publisher": "Review of Scientific Instruments", "publication": "Review of Scientific Instruments", "publication_date": "1993-04-01", "series_number": "4", "volume": "64", "issue": "4", "pages": "904-907" }, { "id": "authors:v6hhj-gha13", "collection": "authors", "collection_id": "v6hhj-gha13", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:BASrsi93a", "type": "article", "title": "Scanned-cantilever atomic force microscope", "author": [ { "family_name": "Baselt", "given_name": "David R.", "clpid": "Baselt-D-R" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "We have developed a 3.6 \u00b5m scan range atomic force microscope that scans the cantilever instead of the sample, while the optical-lever detection apparatus remains stationary. The design permits simpler, more adaptable sample mounting, and generally improves ease of use. Software workarounds alleviate the minor effects of spurious signal variations that arise as a result of scanning the cantilever. The performance of the microscope matches that of scanned-sample instruments.", "doi": "10.1063/1.1144142", "issn": "0034-6748", "publisher": "American Institute of Physics", "publication": "Review of Scientific Instruments", "publication_date": "1993-04", "series_number": "4", "volume": "64", "issue": "4", "pages": "908-911" }, { "id": "authors:hn3zc-k3b42", "collection": "authors", "collection_id": "hn3zc-k3b42", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:CLArsi92", "type": "article", "title": "Hardware for digitally controlled scanned probe microscopes", "author": [ { "family_name": "Clark", "given_name": "S. M.", "clpid": "Clark-S-M" }, { "family_name": "Baselt", "given_name": "D. R.", "clpid": "Baselt-D-R" }, { "family_name": "Spence", "given_name": "C. F.", "clpid": "Spence-C-F" }, { "family_name": "Youngquist", "given_name": "M. G.", "clpid": "Youngquist-M-G" }, { "family_name": "Baldeschwieler", "given_name": "J. D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "The design and implementation of a flexible and modular digital control and data acquisition system for scanned probe microscopes (SPMs) is presented. The measured performance of the system shows it to be capable of 14-bit data acquisition at a 100-kHz rate and a full 18-bit output resolution resulting in less than 0.02-\u00c5 rms position noise while maintaining a scan range in excess of 1 \u00b5m in both the X and Y dimensions. This level of performance achieves the goal of making the noise of the microscope control system an insignificant factor for most experiments. The adaptation of the system to various types of SPM experiments is discussed. Advances in audio electronics and digital signal processors have made the construction of such high performance systems possible at low cost.", "doi": "10.1063/1.1143728", "issn": "0034-6748", "publisher": "Review of Scientific Instruments", "publication": "Review of Scientific Instruments", "publication_date": "1992-10-01", "series_number": "10", "volume": "63", "issue": "10", "pages": "4296-4307" }, { "id": "authors:gdtgs-e4q67", "collection": "authors", "collection_id": "gdtgs-e4q67", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:MALpnas92", "type": "article", "title": "Phagocytosis of liposomes by human platelets", "author": [ { "family_name": "Male", "given_name": "Roxanne", "clpid": "Male-R" }, { "family_name": "Vannier", "given_name": "Wilton E.", "clpid": "Vannier-W-E" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "We have shown that platelets are capable of phagocytosing liposomes rather than simply sequestering particles as previously postulated. Incubation of human platelets with small neutral unilamellar liposomes (almost-equal-to 74 nm) resulted in uptake of the liposomes and retention of the lipid with rapid release of the aqueous-phase components. The lipid label [H-3]-cholesterylhexadecyl ether and water-soluble [H-3]inulin were used to study the fate of the liposome components. Uptake of liposomes was proportional to the number of liposomes added and to the incubation time. Approximately 250 liposomes per platelet were taken up within a 5-hr incubation period. Uptake of the liposomes occurred through the open-channel system, as evidenced by thin-section electron microscopy, and was followed by accumulation and degradation in acid- and esterase-containing vesicles, as determined by changes in fluorescence of the pH-sensitive probe, pyranine (1-hydroxypyrene-3,6,8-trisulfonic acid), and hydrolysis of the cholesteryl [C-14]oleate membrane marker. Uptake was inhibited by the addition of EDTA, cytochalasin B, or 2,4-dinitrophenol and iodoacetate to the medium. Results from the serotonin release assay, microaggregation assay, fluorescein diacetate membrane integrity assay, and electron microscopy indicate that neither the conditions for loading nor phagocytosis of liposomes significantly alter platelet function or morphology.", "doi": "10.1073/pnas.89.19.9191", "pmcid": "PMC50091", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "1992-10-01", "series_number": "19", "volume": "89", "issue": "19", "pages": "9191-9195" }, { "id": "authors:cpb3x-9yt37", "collection": "authors", "collection_id": "cpb3x-9yt37", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:BASjvstb92", "type": "article", "title": "Lateral forces during atomic force microscopy of graphite in air", "author": [ { "family_name": "Baselt", "given_name": "David R.", "clpid": "Baselt-D-R" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "Highly oriented pyrolytic graphite and boronated pyrolytic graphite were imaged in air by simultaneous normal and lateral force microscopy. A number of effects occurred when scanning over steps, including an increase in attractive forces from surface contamination which could be detrimental to the imaging of soft or weakly bonded samples. Contamination may also give rise to regions of high lateral force which do not seem to be associated with any topographic features. Finally, in atomic resolution images of graphite, atomic corrugation was clearer in the lateral cantilever deflection images than in the simultaneous topography and normal cantilever deflection images, demonstrating the high sensitivity of lateral force detection to topographic features.", "doi": "10.1116/1.586061", "issn": "1071-1023", "publisher": "American Vacuum Society", "publication": "Journal of Vacuum Science and Technology B", "publication_date": "1992-09", "series_number": "5", "volume": "10", "issue": "5", "pages": "2316-2322" }, { "id": "authors:6vqsj-fdq65", "collection": "authors", "collection_id": "6vqsj-fdq65", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180212-100837449", "type": "article", "title": "Alterations in membrane surfaces induced by attachment of carbohydrates", "author": [ { "family_name": "Goodrich", "given_name": "Raymond P.", "clpid": "Goodrich-R-P" }, { "family_name": "Crowe", "given_name": "John H.", "clpid": "Crowe-J-H" }, { "family_name": "Crowe", "given_name": "Lois M.", "clpid": "Crowe-L-M" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "We have examined the behavior of the dry phospholipid dipalmitoylphosphatidylcholine (DPPC) in the presence of several carbohydrate derivatives. These carbohydrate derivatives possess a hydrophobic portion which is incorporated directly into the DPPC membrane and a hydrophilic portion which places the carbohydrate structure at the membrane interface with the surrounding matrix. In the presence of these derivatives, the physical properties of the membrane are altered. These alterations are evident in changes observed in the phosphate and carbonyl vibrational modes of the phospholipid portion of the membrane. In addition, the phase transition behavior of the lipid is significantly altered as evidenced by a reduction\nin the gel to liquid-crystalline phase transition temperature. These results are consistent with those Previously reported for free carbohydrates interacting with membranes in which a water replacement hypothesis has been used to explain the behavior. The attachment of carbohydrates to the membrane enhances these effects by localizing the agent responsible for these alterations at the membrane interface.", "doi": "10.1021/bi00235a026", "issn": "0006-2960", "publisher": "American Chemical Society", "publication": "Biochemistry", "publication_date": "1991-05-28", "series_number": "21", "volume": "30", "issue": "21", "pages": "5313-5318" }, { "id": "authors:erqed-q5e53", "collection": "authors", "collection_id": "erqed-q5e53", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:YOUjvstb91b", "type": "article", "title": "Scanning tunneling microscopy of DNA: Atom-resolved imaging, general observations and possible contrast mechanism", "author": [ { "family_name": "Youngquist", "given_name": "M. G.", "clpid": "Youngquist-M-G" }, { "family_name": "Driscoll", "given_name": "R. J.", "clpid": "Driscoll-R-J" }, { "family_name": "Coley", "given_name": "T. R.", "clpid": "Coley-T-R" }, { "family_name": "Goddard", "given_name": "W. A.", "orcid": "0000-0003-0097-5716", "clpid": "Goddard-W-A-III" }, { "family_name": "Baldeschwieler", "given_name": "J. D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "We have shown that it is possible to image DNA with atomic resolution using scanning tunneling microscopy (STM), [R. J. Driscoll, M. G. Youngquist, and J. D. Baldeschwieler, Nature 346, 294 (1990)]. Here we describe that data together with our general observations on STM of DNA in ultrahigh vacuum. We also suggest a possible contrast mechanism for DNA imaging by STM based on wave function orthogonality requirements between a molecule and its substrate. Topographic images are presented which resolve atomic features in addition to the double helical structure and nucleotide pairs of the DNA molecule. Comparisons of experimental STM profiles and modeled contours of the van der Waals surface of A-DNA show excellent correlation. Successive scans show that the imaging is nondestructive and reproducible. For this study, double-stranded DNA was deposited on highly oriented pyrolitic graphite without coating, shadowing, or chemical modification.", "doi": "10.1116/1.585226", "issn": "1071-1023", "publisher": "American Vacuum Society", "publication": "Journal of Vacuum Science and Technology B", "publication_date": "1991-03", "series_number": "2", "volume": "9", "issue": "2", "pages": "1304-1308" }, { "id": "authors:e0rta-2yh43", "collection": "authors", "collection_id": "e0rta-2yh43", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:YOUjvstb91a", "type": "article", "title": "Observation of negative differential resistance in tunneling spectroscopy of MoS2 with a scanning tunneling microscope", "author": [ { "family_name": "Youngquist", "given_name": "M. G.", "clpid": "Youngquist-M-G" }, { "family_name": "Baldeschwieler", "given_name": "J. D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "A scanning tunneling microscope has been used for imaging and tunneling spectroscopy of 2Hb\u2013MoS2 in ultrahigh vacuum. Atom-resolved images obtained in three distinct imaging modes\u2013measuring z at constant current, barrier height at constant current, and current at constant z\u2013are presented. Current\u2013voltage (I\u2013V) tunneling spectra reveal the occasional presence of negative differential resistance. Possible origins of the effect are discussed. Convolution of the sample energy density of states (DOS) with a contamination-induced peak in the tip DOS is the probable cause. Other mechanisms that may be active include charging of electron traps in the barrier or on the tip, and resonant tunneling in a double-barrier quantum well structure resulting from layer separation in the MoS2 crystal.", "doi": "10.1116/1.585265", "issn": "1071-1023", "publisher": "American Vacuum Society", "publication": "Journal of Vacuum Science and Technology B", "publication_date": "1991-03", "series_number": "2", "volume": "9", "issue": "2", "pages": "1083-1087" }, { "id": "authors:0d8kk-1qp17", "collection": "authors", "collection_id": "0d8kk-1qp17", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120418-154021664", "type": "article", "title": "Theoretical interpretation of scanning tunneling microscopy images: Application to the molybdenum disulfide family of transition metal dichalcogenides", "author": [ { "family_name": "Coley", "given_name": "Terry R.", "clpid": "Coley-T-R" }, { "family_name": "Goddard", "given_name": "William A., III", "orcid": "0000-0003-0097-5716", "clpid": "Goddard-W-A-III" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "We have performed ab initio quantum mechanical calculations to describe scanning tunneling microscopy (STM) images of MoS_2 and MoTe_2. These results indicate that the interpretation of the STM images of these and related materials depends sensitively on experimental conditions. For example, determining whether the maximum tunneling current correlates to the top atom (S or Te) or to the second\u2010layer atom (Mo) requires information on the tip\u2010sample separation. Based on these results we discuss some STM experimental procedures which would allow assignment of the chemical identity of STM spots with greater certainty.", "doi": "10.1116/1.585591", "issn": "1071-1023", "publisher": "American Vacuum Society", "publication": "Journal of Vacuum Science and Technology B", "publication_date": "1991-03", "series_number": "2", "volume": "9", "issue": "2", "pages": "470-474" }, { "id": "authors:62j36-q0f03", "collection": "authors", "collection_id": "62j36-q0f03", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150513-085838877", "type": "article", "title": "Atomic-scale imaging of DNA using scanning tunnelling microscopy", "author": [ { "family_name": "Driscoll", "given_name": "Robert J.", "clpid": "Driscoll-R-J" }, { "family_name": "Youngquist", "given_name": "Michael G.", "clpid": "Youngquist-M-G" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "THE scanning tunnelling microscope (STM) has been used to visualize DNA under water, under oil and in air. Images of single-stranded DNA have shown that submolecular resolution is possible. Here we describe atomic-resolution imaging of duplex DNA. Topographic STM images of uncoated duplex DNA on a graphite substrate obtained in ultra-high vacuum are presented that show double-helical structure, base pairs, and atomic-scale substructure. Experimental STM profiles show excellent correlation with atomic contours of the van der Waals surface of A-form DNA derived from X-ray crystallography. A comparison of variations in the barrier to quantum mechanical tunnelling (barrier-height) with atomic-scale topography shows correlation over the phosphate-sugar backbone but anticorrelation over the base pairs. This relationship may be due to the different chemical characteristics of parts of the molecule. Further investigation of this phenomenon should lead to a better understanding of the physics of imaging adsorbates with the STM and may prove useful in sequencing DNA. The improved resolution compared with previously published STM images of DNA may be attributable to ultra-high vacuum, high data-pixel density, slow scan rate, a fortuitously clean and sharp tip and/or a relatively dilute and extremely clean sample solution. This work demonstrates the potential of the STM for characterization of large biomolecular structures, but additional development will be required to make such high resolution imaging of DNA and other large molecules routine.", "doi": "10.1038/346294a0", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "1990-07-19", "series_number": "6281", "volume": "346", "issue": "6281", "pages": "294-296" }, { "id": "authors:npsjh-ejd75", "collection": "authors", "collection_id": "npsjh-ejd75", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:LUOjvsta90", "type": "article", "title": "Scanning tunneling microscopy of the phosphatidylcholine bilayers", "author": [ { "family_name": "Luo", "given_name": "Changhong", "clpid": "Luo-Changhong" }, { "family_name": "Zhu", "given_name": "Chuanfeng", "clpid": "Zhu-Chuanfeng" }, { "family_name": "Ruan", "given_name": "Like", "clpid": "Ruan-Like" }, { "family_name": "Huang", "given_name": "Guizhen", "clpid": "Huang-Guizhen" }, { "family_name": "Dai", "given_name": "Changchun", "clpid": "Dai-Changchun" }, { "family_name": "Cheng", "given_name": "Zhengbo", "clpid": "Cheng-Zhengbo" }, { "family_name": "Bai", "given_name": "Chunli", "clpid": "Bai-Chunli" }, { "family_name": "Su", "given_name": "Yaxian", "clpid": "Su-Yaxian" }, { "family_name": "Xu", "given_name": "Sanduo", "clpid": "Xu-Sanduo" }, { "family_name": "Lin", "given_name": "Kechun", "clpid": "Lin-Kechun" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "The bare surface of the egg-PC bilayers after being dried at room temperature was observed by the STM and images with angstrom resolution were obtained. Results indicate that the lipid heads form islands of an average of 210 \u00c5 in diameter and 40 \u00c5 in separation on the bilayers and that each island contains about 170 lipid heads of 7.5 \u00c5 in diameter. The size of the lipid heads is correspondent with that calculated from the standard bond distances and the bond angles. The ordered distribution of the lipid heads in some areas may correspond to the ordered arrangement of the lipid heads on the egg-PC bilayers before being dried. The STM results also show that there exists the ripple phase in the egg-PC bilayers below its phase transition temperature.", "doi": "10.1116/1.576981", "issn": "0734-2101", "publisher": "American Vacuum Society", "publication": "Journal of Vacuum Science and Technology A", "publication_date": "1990-01", "series_number": "1", "volume": "8", "issue": "1", "pages": "684-686" }, { "id": "authors:jv9eh-c6681", "collection": "authors", "collection_id": "jv9eh-c6681", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:BAIjvsta90", "type": "article", "title": "Scanning tunneling microscopy of silver containing salt of bis(ethylenedithio)tetrathiafulvalene", "author": [ { "family_name": "Bai", "given_name": "C.", "clpid": "Bai-Chunli" }, { "family_name": "Dai", "given_name": "C.", "clpid": "Dai-Changchun" }, { "family_name": "Zhu", "given_name": "C.", "clpid": "Zhu-Chuanfeng" }, { "family_name": "Chen", "given_name": "Z.", "clpid": "Cheng-Zhengbo" }, { "family_name": "Huang", "given_name": "G.", "clpid": "Huang-Guizhen" }, { "family_name": "Wu", "given_name": "X.", "clpid": "Wu-X" }, { "family_name": "Zhu", "given_name": "D.", "clpid": "Zhu-D" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "The surface of silver containing salt of bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) was studied with the computer-controlled scanning tunneling microscope developed in our laboratory. The crystal surface of the charge-transfer complex is well ordered and a regular array of corrugations is clearly visible. The prominent feature of the experimental scanning tunneling microscopy images is in agreement with the bulk crystal structure obtained by x-ray diffraction method.", "doi": "10.1116/1.577024", "issn": "0734-2101", "publisher": "American Vacuum Society", "publication": "Journal of Vacuum Science and Technology A", "publication_date": "1990-01", "series_number": "1", "volume": "8", "issue": "1", "pages": "484-487" }, { "id": "authors:84xm5-0gm06", "collection": "authors", "collection_id": "84xm5-0gm06", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:WEIprb89", "type": "article", "title": "Band bending and the apparent barrier height in scanning tunneling microscopy", "author": [ { "family_name": "Weimer", "given_name": "M.", "clpid": "Weimer-M" }, { "family_name": "Kramar", "given_name": "J.", "clpid": "Kramar-J" }, { "family_name": "Baldeschwieler", "given_name": "J. D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "We consider the influence of tip-induced band bending on the apparent barrier height deduced from scanning tunneling microscopy (STM) experiments at unpinned semiconductor surfaces. Any voltage applied to a probe tip appears partly in the vacuum gap as an electric field at the semiconductor surface and partly in the semiconductor interior as band bending. The fraction appearing in each region is a function of gap spacing so that modulation of the tip-sample separation inevitably modulates the induced surface potential in the semiconductor. At finite temperature, the height and shape of this barrier determine the probability that an electron will reach the semiconductor surface where it can subsequently tunnel through the vacuum gap. Since the surface potential decreases with increasing tip-sample separation, STM measurements of the tunneling barrier at unpinned semiconductor surfaces will yield unusually low values. Detailed numerical calculations of the effect for passivated n-type Si(111) show it to be of observable magnitude. This mechanism may be distinguished from other recently proposed barrier-lowering mechanisms in that it is doping dependent, potentially long range, and possesses a unique voltage signature.", "doi": "10.1103/PhysRevB.39.5572", "issn": "0163-1829", "publisher": "Physical Review B", "publication": "Physical Review B", "publication_date": "1989-03-15", "series_number": "8", "volume": "39", "issue": "8", "pages": "5572-5575" }, { "id": "authors:qgpae-qp448", "collection": "authors", "collection_id": "qgpae-qp448", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:DERpnas88", "type": "article", "title": "In vivo stability of ester- and ether-linked phospholipid-containing liposomes as measured by perturbed angular correlation spectroscopy", "author": [ { "family_name": "Derksen", "given_name": "Johannes T. P.", "clpid": "Derksen-J-T-P" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" }, { "family_name": "Scherphof", "given_name": "Gerrit L.", "clpid": "Scherphof-G-L" } ], "abstract": "To evaluate liposome formulations for use as intracellular sustained-release drug depots, we have compared the uptake and degradation in rat liver and spleen of liposomes of various compositions, containing as their bulk phospholipid an ether-linked phospholipid or one of several ester-linked phospholipids, by perturbed angular correlation spectroscopy. Multilamellar and small unilamellar vesicles (MLVs and SUVs), composed of egg phosphatidylcholine, sphingomyelin, distearoyl phosphatidylcholine (DSPC), dipalmitoyl phosphatidylcholine (DPPC) or its analog dihexadecylglycerophosphorylcholine (DHPC), and cholesterol plus phosphatidylserine, and containing (111)In complexed to nitrilotriacetic acid, were injected intravenously in rats. Recovery of (111)In-labeled liposomes in blood, liver, and spleen was assessed at specific time points after injection and the percentage of liposomes still intact in liver and spleen was determined by measurement of the time-integrated angular perturbation factor ([G22(\u221e)] of the (111)In label. We found that MLVs but not SUVs, having DHPC as their bulk phospholipid, showed an increased resistance against lysosomal degradation as compared to other phospholipid-containing liposomes. The use of diacyl phospholipids with a high gel/liquid-crystalline phase-transition temperature, such as DPPC and DSPC, also retarded degradation of MLV, but not of SUV in the dose range tested, while the rate of uptake of these liposomes by the liver was lower.", "doi": "10.1073/pnas.85.24.9768", "pmcid": "PMC282862", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "1988-12-15", "series_number": "24", "volume": "85", "issue": "24", "pages": "9768-9772" }, { "id": "authors:8txse-1b154", "collection": "authors", "collection_id": "8txse-1b154", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:WEIprb88.993", "type": "article", "title": "Tunneling microscopy of 2H-MoS2: A compound semiconductor surface", "author": [ { "family_name": "Weimer", "given_name": "M.", "clpid": "Weimer-M" }, { "family_name": "Kramar", "given_name": "J.", "clpid": "Kramar-J" }, { "family_name": "Bai", "given_name": "C.", "clpid": "Bai-C" }, { "family_name": "Baldeschwieler", "given_name": "J. D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "Molybdenum disulfide, a layered semiconductor, is an interesting material to study with the tunneling microscope because two structurally and electronically different atomic species may be probed at its surface. We report on a vacuum scanning tunneling microscopy study of 2H-MoS2. Atomic resolution topographs and current images show the symmetry of the surface unit cell and clearly reveal two distinct atomic sites in agreement with the well-known x-ray crystal structure.", "doi": "10.1103/PhysRevB.37.4292", "issn": "0163-1829", "publisher": "Physical Review B", "publication": "Physical Review B", "publication_date": "1988-03-15", "series_number": "8", "volume": "37", "issue": "8", "pages": "4292-4295" }, { "id": "authors:b044w-twp03", "collection": "authors", "collection_id": "b044w-twp03", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120601-094704348", "type": "article", "title": "Imaging graphite in air by scanning tunneling microscopy: Role of the tip", "author": [ { "family_name": "Colton", "given_name": "R. J.", "clpid": "Colton-R-J" }, { "family_name": "Baker", "given_name": "S. M.", "clpid": "Baker-S-M" }, { "family_name": "Driscoll", "given_name": "R. J.", "clpid": "Driscoll-R-J" }, { "family_name": "Youngquist", "given_name": "M. G.", "clpid": "Youngquist-M-G" }, { "family_name": "Baldeschwieler", "given_name": "J. D.", "clpid": "Baldeschwieler-J-D" }, { "family_name": "Kaiser", "given_name": "W. J.", "clpid": "Kaiser-W-J" } ], "abstract": "We have been successful in obtaining atomically resolved images of highly oriented pyrolytic graphite (HOPG) in air at point contact. Direct contact between tip and sample or contact through a contamination layer provides a conduction mechanism in addition to the exponential tunneling mechanism responsible for scanning tunneling microscopy (STM) imaging. Current\u2013voltage (I\u2013V) spectra were obtained while scanning in the current imaging mode with the feedback circuit interrupted in order to study the graphite imaging mechanism. Multiple tunneling tips are probably responsible for images without the expected hexagonal or trigonal symmetry. Our observations indicate that the use of HOPG for testing and calibration of STM instrumentation may be misleading.", "doi": "10.1116/1.575411", "issn": "0734-2101", "publisher": "American Vacuum Society", "publication": "Journal of Vacuum Science and Technology A", "publication_date": "1988-03", "series_number": "2", "volume": "6", "issue": "2", "pages": "349-353" }, { "id": "authors:b6nch-q8760", "collection": "authors", "collection_id": "b6nch-q8760", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120531-132132319", "type": "article", "title": "Scanning tunneling microscopy investigation of 2H-MoS_2: A layered semiconducting transition\u2010metal dichalcogenide", "author": [ { "family_name": "Weimer", "given_name": "M.", "clpid": "Weimer-M" }, { "family_name": "Kramar", "given_name": "J.", "clpid": "Kramar-J" }, { "family_name": "Bai", "given_name": "C.", "clpid": "Bai-C" }, { "family_name": "Baldeschwieler", "given_name": "J. D.", "clpid": "Baldeschwieler-J-D" }, { "family_name": "Kaiser", "given_name": "W. J.", "clpid": "Kaiser-W-J" } ], "abstract": "Scanning tunneling microscopy (STM) has been enormously\nsuccessful in solving several important problems in the geometric and electronic structure of homogeneous metallic and semiconducting surfaces. A central question which remains to be answered with respect to the study of\ncompound surfaces, however, is the extent to which the\nchemical identity of constituent atoms may be established.\nRecently, progress in this area was made by Feenstra et al.\nwho succeeded in selectively imaging either Ga or As atoms\non the GaAs (110) surface. So far this is the only case where such selectivity has been achieved. In an effort to add to our understanding of compound surface imaging we have undertaken a vacuum STM study of 2H-MoS_2, a material which has two structurally and electronically different atomic species at its surface.", "doi": "10.1116/1.575408", "issn": "0734-2101", "publisher": "American Vacuum Society", "publication": "Journal of Vacuum Science and Technology A", "publication_date": "1988-03", "series_number": "2", "volume": "6", "issue": "2", "pages": "336-337" }, { "id": "authors:m9rfp-4bh47", "collection": "authors", "collection_id": "m9rfp-4bh47", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:COLapl87", "type": "article", "title": "\"Oxide-free\" tip for scanning tunneling microscopy", "author": [ { "family_name": "Colton", "given_name": "R. J.", "clpid": "Colton-R-J" }, { "family_name": "Baker", "given_name": "S. M.", "clpid": "Baker-S-M" }, { "family_name": "Baldeschwieler", "given_name": "J. D.", "clpid": "Baldeschwieler-J-D" }, { "family_name": "Kaiser", "given_name": "W. J.", "clpid": "Kaiser-W-J" } ], "abstract": "We report a new tip for scanning tunneling microscopy and a tip repair procedure that allows one to reproducibly obtain atomic images of highly oriented pyrolytic graphite with previously inoperable tips. The tips are shown to be relatively oxide-free and highly resistant to oxidation. The tips are fabricated with graphite by two distinct methods.", "doi": "10.1063/1.98451", "issn": "0003-6951", "publisher": "Applied Physics Letters", "publication": "Applied Physics Letters", "publication_date": "1987-08-03", "series_number": "5", "volume": "51", "issue": "5", "pages": "305-307" }, { "id": "authors:xwevw-hv352", "collection": "authors", "collection_id": "xwevw-hv352", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120629-130908919", "type": "article", "title": "The effect of thermal vibrations on extended x-ray absorption\n fine structure. II", "author": [ { "family_name": "Boland", "given_name": "John J.", "clpid": "Boland-J-J" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "A formalism is introduced to describe the dependence of the EXAFS amplitude and phase on thermally excited vibrations. The EXAFS expression for a general three\u2010atom system of C_s symmetry is discussed in detail. To lowest order, thermal vibrations induce a change only in the scattering path length and give rise to the standard EXAFS expression for each scattering path damped by the appropriate Debye\u2010Waller factor. A change in scattering angle, however, is a higher order effect and gives rise to additional EXAFS terms called modification factors. There is a modification factor associated with each multiple scattering path. Within this formalism, the correlation which exists between a change in scattering path length and a change in scattering angle is explicitly calculated. The normal modes which contribute to the modification factors are discussed, and shown to be dependent on the symmetry of the system. The nature and temperature dependence of the Debye\u2013Waller and modification factors for the three\u2010atom system Br_2O are discussed as a function of bridging angle. The modification factors are shown to make a small contribution to the total EXAFS of the system. The magnitude of this contribution is dependent on the degree of correlation that exists between changes in scattering path length and scattering angle.", "doi": "10.1063/1.447807", "issn": "0021-9606", "publisher": "American Institute of Physics", "publication": "Journal of Chemical Physics", "publication_date": "1984-08-01", "series_number": "3", "volume": "81", "issue": "3", "pages": "1145-1159" }, { "id": "authors:r8f0x-bwt19", "collection": "authors", "collection_id": "r8f0x-bwt19", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120629-114413977", "type": "article", "title": "The effect of thermal vibrations on extended x-ray absorption fine structure. I", "author": [ { "family_name": "Boland", "given_name": "John J.", "clpid": "Boland-J-J" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "The form of the Debye\u2013Waller factor in EXAFS is discussed in detail, and an expression is obtained for this factor in a general three\u2010atom system of C_s symmetry. The normal modes which contribute to the Debye\u2013Waller factors for each scattering path are dependent on the symmetry of the system. A series of model three\u2010atom systems with C_(2v) symmetry are studied and the Debye\u2013Waller factors as a function of the bridging angle are discussed for each of these systems. The temperature dependence of the Debye\u2010Waller factor for each scattering path is also studied. In a system of C_(2v) symmetry, approximating the double and triple scattering Debye\u2013Waller factors by the second shell single scattering factor is shown to be strictly valid only for a system close to linearity. The error due to this approximation is dependent upon the amplitude of the individual scattering paths and is shown to increase with temperature. When the single scattering contribution is unimportant, there is shown to exist a temperature where the above approximation is exact.", "doi": "10.1063/1.447135", "issn": "0021-9606", "publisher": "American Institute of Physics", "publication": "Journal of Chemical Physics", "publication_date": "1984-04-01", "series_number": "7", "volume": "80", "issue": "7", "pages": "3005-3015" }, { "id": "authors:q0scs-ee372", "collection": "authors", "collection_id": "q0scs-ee372", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:PATpnas83", "type": "article", "title": "Suppression of liver uptake of liposomes by dextran sulfate 500", "author": [ { "family_name": "Patel", "given_name": "Kanaiyalal R.", "clpid": "Patel-Kanaiyalal-R" }, { "family_name": "Li", "given_name": "Ming P.", "clpid": "Li-Ming-P" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "The effect of dextran sulfate (DS, 500,000 Mr) and multilamellar vesicles (MLV) as liver blockade agents has been investigated in mice. Intravenous injection of unlabeled MLV prior to radioactive MLV caused moderate reduction in the liver uptake and increased tibia, lung, and spleen uptake. More drastic differences were observed with intraperitoneal injection of DS. When tested in the range of 0-50 mg of DS per kg of body weight, maximal liver blockade occurred at a dose of 50 mg. By using 50 mg of DS per kg, maximal liver blockade occurred at 12 hr after DS injection. The liver blockade was temporary, ending within 48 hr. The intraperitoneal route of injection for DS was more effective for liver blockade than the intravenous route.", "doi": "10.1073/pnas.80.21.6518", "pmcid": "PMC390384", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "1983-11-01", "series_number": "21", "volume": "80", "issue": "21", "pages": "6518-6522" }, { "id": "authors:0k0d3-p6p50", "collection": "authors", "collection_id": "0k0d3-p6p50", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120706-142629255", "type": "article", "title": "Data analysis in extended x-ray-absorption fine structure: Determination of the background absorption and the threshold energy", "author": [ { "family_name": "Boland", "given_name": "John J.", "clpid": "Boland-J-J" }, { "family_name": "Halaka", "given_name": "Folim G.", "clpid": "Halaka-F-G" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "Two approaches for the determination of the background absorption (\u03bc_0) in the extended x-ray-absorption fine structure (EXAFS) are presented. Both methods, experimental and computational, take advantage of the damping of the EXAFS amplitude resulting from the convolution with Gaussian functions of different widths. In the experimental method two or more spectra are collected with the use of different spectrometer slit widths, resulting in spectra of different resolutions for the same sample. In the computational approach the convolution is accomplished via a convolution algorithm. The intersection points of the resulting spectra are used to generate \u03bc_0. At the absorption edge, the spectra intersect at a unique point, which is shown to be a measure of the threshold energy, E_0. Illustration of the two methods for background removal is given for a copper-foil sample. The computational approach is superior to the experimental method of damping the EXAFS spectra to give \u03bc_0.", "doi": "10.1103/PhysRevB.28.2921", "issn": "1098-0121", "publisher": "American Physical Society", "publication": "Physical Review B", "publication_date": "1983-09-15", "series_number": "6", "volume": "28", "issue": "6", "pages": "2921-2926" }, { "id": "authors:4wfad-wf630", "collection": "authors", "collection_id": "4wfad-wf630", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:KRUpnas83", "type": "article", "title": "Stability of erythrocyte ghosts: A \u03b3-ray perturbed angular correlation study", "author": [ { "family_name": "Kruse", "given_name": "Carol A.", "clpid": "Kruse-C-A" }, { "family_name": "Tin", "given_name": "George W.", "clpid": "Tin-G-W" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "The structural integrity of erythrocyte ghosts made by the preswell and slow-dialysis techniques has been studied in vitro by use of \u03b3-ray perturbed angular correlation (PAC) techniques and also by standard in vitro leakage methods employing sequestered labeled markers. Complexes of (111)In(3+) and nitrilotriacetate were encapsulated in ghosts made from human, rabbit, rat, and mouse erythrocytes, and their leakage was monitored by both methods. In addition, (125)I-labeled bovine serum albumin was encapsulated, and ghost integrity was monitored by conventional leakage measurements. With the PAC technique the percentage of material released from human ghosts was determined quantitatively, and the results were equivalent to those obtained by the conventional method. In addition, at various times after intravenous injection, tissue distribution of the ghosts in the mouse was studied. The percent injected dose per gram of tissue of the labeled surface proteins of erythrocyte ghosts in circulation approximated that of the entrapped labeled albumin. This suggests that the ghost membrane and contents are strongly associated in vivo. Large (125)I-labeled bovine serum albumin molecules and small (111)In(3+)-nitrilotriacetate complexes were delivered in high quantities to the lung initially, and to the liver and spleen. Because erythrocyte ghosts have the ability to entrap a wide range of substances and deliver them to specific organs, ghosts may be preferable to other drug carriers or drug therapy for treatment of certain disorders.", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "1983-03-01", "series_number": "5", "volume": "80", "issue": "5", "pages": "1212-1216" }, { "id": "authors:m1fns-zct28", "collection": "authors", "collection_id": "m1fns-zct28", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:WUPpnas82", "type": "article", "title": "Stability of carbohydrate-modified vesicles in vivo: Comparative effects of ceramide and cholesterol glycoconjugates", "author": [ { "family_name": "Wu", "given_name": "Po-Shun", "clpid": "Wu-P-S" }, { "family_name": "Wu", "given_name": "Hsiu-Mei", "clpid": "Wu-H-M" }, { "family_name": "Tin", "given_name": "George W.", "clpid": "Tin-G-W" }, { "family_name": "Schuh", "given_name": "Joseph R.", "clpid": "Schuh-J-R" }, { "family_name": "Croasmun", "given_name": "William R.", "clpid": "Croasmun-W-R" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" }, { "family_name": "Shen", "given_name": "T. Y.", "clpid": "Shen-T-Y" }, { "family_name": "Ponpipom", "given_name": "M. M.", "clpid": "Ponpipom-M-M" } ], "abstract": "The stability and tissue distribution of lipid vesicles modified at the surface by the incorporation of either a galactosyl ceramide (GalCer) or a galactosyl cholesterol (GalChol) glycoconjugate have been studied in mice by measuring the release of vesicle-entrapped (111)In. Although the tissue distributions of both vesicle types were similar, the GalCer-containing vesicles were markedly less stable than those prepared with GalChol, whether administered orally or by intraperitoneal injection. Physical characterization of the vesicles in vitro suggests that the increased disruption rate for GalCer vesicles in vivo is related to structural instabilities induced by the cerebroside, which can then result in either an increased rate of vesicle uptake by tissues or a greater susceptibility to lysis. These studies demonstrate the importance of the nonpolar anchoring groups in determining the fate of surface-modified vesicles in vivo.", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "1982-09-15", "series_number": "18", "volume": "79", "issue": "18", "pages": "5490-5493" }, { "id": "authors:8dd9c-am852", "collection": "authors", "collection_id": "8dd9c-am852", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:BOLjcp82", "type": "article", "title": "Theory of extended x-ray absorption fine structure: Single and multiple scattering formalisms", "author": [ { "family_name": "Boland", "given_name": "John J.", "clpid": "Boland-J-J" }, { "family_name": "Crane", "given_name": "Stepohen E.", "clpid": "Crane-S-E" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "A generalized formalism for the EXAFS effect is presented. The full T operator in the Lippmann\u2013Schwinger equation is expanded and the first term and part of the second term are seen to effectively correspond to single scattering EXAFS processes. The latter term includes secondary scattering by the absorber, and within this formalism it is this term that introduces the central atom phase shift. The expression obtained for the single scattering problem is identical with that found by other investigators. A solution to the general EXAFS problem involving an absorbing atom and two neighboring atoms is also presented. The expression differs from that previously reported [B. K. Teo, J. Am. Chem. Soc. 103, 3990 (1981)]. Multiple scattering is seen to contribute increasingly to the EXAFS as the three atoms approach colinearity. Both the amplitude and frequency of the multiple scattering components are functions of the geometry of the system. The model systems studied indicate that, in many cases, multiple scattering effects must be considered in the analysis of non-nearest-neighbor shells. The theory may readily be extended to systems and scattering paths of arbitrary complexity.", "doi": "10.1063/1.443662", "issn": "0021-9606", "publisher": "American Institute of Physics", "publication": "Journal of Chemical Physics", "publication_date": "1982-07-01", "series_number": "1", "volume": "77", "issue": "1", "pages": "142-153" }, { "id": "authors:er1gx-92t68", "collection": "authors", "collection_id": "er1gx-92t68", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:WUPpnas81b", "type": "article", "title": "Effect of surface modification on aggregation of phospholipid vesicles", "author": [ { "family_name": "Wu", "given_name": "Po-Shun", "clpid": "Wu-P-S" }, { "family_name": "Tin", "given_name": "George W.", "clpid": "Tin-G-W" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" }, { "family_name": "Shen", "given_name": "T. Y.", "clpid": "Shen-T-Y" }, { "family_name": "Ponpipom", "given_name": "M. M.", "clpid": "Ponpipom-M-M" } ], "abstract": "Phospholipid vesicles have been extensively investigated because of their usefulness as models for biological membranes and their potential application as carriers for drug delivery. However, preparations of small sonicated vesicles tend to aggregate and fuse (on storage at room temperature and at 4 degrees C), resulting in significant changes in turbidity, rate of uptake by macrophage, and proton NMR linewidths. By modification of the surface of phospholipid vesicles with charged groups such as \u00df - aminogalactose that extend significantly from the vesicle surface, it is possible to obtain preparations that are stable for >7 days.", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "1981-10-01", "series_number": "10", "volume": "78", "issue": "10", "pages": "6211-6215" }, { "id": "authors:470x6-43t71", "collection": "authors", "collection_id": "470x6-43t71", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:WUPpnas81a", "type": "article", "title": "Phagocytosis of carbohydrate-modified phospholipid vesicles by macrophage", "author": [ { "family_name": "Wu", "given_name": "Po-shun", "clpid": "Wu-P-S" }, { "family_name": "Tin", "given_name": "George W.", "clpid": "Tin-G-W" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "Modification of the surface of distearoyl phosphatidylcholine vesicles with synthetic glycolipids dramatically affects the rate of uptake of these vesicles by mouse peritoneal macrophage. The high rate of uptake of 6-aminomannose-modified vesicles is effectively inhibited by cytochalasin B and chloroquine but not by colchicine, indicating that the mechanism of vesicle uptake is phagocytosis. Other modified vesicles appear to have some effect on the rate of uptake of 6-aminomannose-modified vesicles suggesting that the various vesicle types compete for the same initial binding sites. Analysis of 6-aminomannose-modified vesicles by \u03b3-ray perturbed angular correlation spectroscopy shows that the rotational correlation time of the encapsulated (111)In(3+) does not change when the vesicles associate with macrophage. This result is consistent with transmission electron microscopy, which indicates that the aminomannose-modified vesicles remain intact after phagocytosis as aggregates of fused and intact vesicles surrounded by a single bilayer membrane structure.", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "1981-04-01", "series_number": "4", "volume": "78", "issue": "4", "pages": "2033-2037" }, { "id": "authors:f63w3-t1d81", "collection": "authors", "collection_id": "f63w3-t1d81", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:MAUpnas80", "type": "article", "title": "Targeting of lipid vesicles: Specificity of carbohydrate receptor analogues for leukocytes in mice", "author": [ { "family_name": "Mauk", "given_name": "Marcia R.", "clpid": "Mauk-M-R" }, { "family_name": "Gamble", "given_name": "Ronald C.", "clpid": "Gamble-R-C" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "The presence of particular surface carbohydrate modifications is shown to affect dramatically the stability and tissue specificity of unilamellar distearoyl phosphatidylcholine vesicles in mice. Use of the \u03b3-ray probe (111)In(3+) permits analysis of tissue distributions by standard \u03b3 counting techniques and determination of the structural integrity of the vesicles by perturbed angular correlation spectroscopy. Addition of a 6-aminomannose derivative of cholesterol to the lipid bilayer produces initial retention of high levels of intact vesicles in the lung after intravenous injection followed by concentration of intact vesicles in the liver and spleen. Vesicles bearing 6-aminosugar residues are found to concentrate in the axillary space in aggregates of polymorphonuclear leukocytes when administered subcutaneously. The in vivo stability of 6-aminomannose-labeled vesicles is substantially greater after intravenous or subcutaneous administration than that observed for any other system examined. The dose-response effects observed with surface modifications indicate that a particular receptor topography is important in the mechanism leading to transport and destruction of these vesicles.", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "1980-08-01", "series_number": "8", "volume": "77", "issue": "8", "pages": "4430-4434" }, { "id": "authors:9byvr-y9780", "collection": "authors", "collection_id": "9byvr-y9780", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150204-113150029", "type": "article", "title": "Vesicle Targeting: Timed Release and Specificity for Leukocytes in Mice by Subcutaneous Injection", "author": [ { "family_name": "Mauk", "given_name": "Marcia R.", "clpid": "Mauk-M-R" }, { "family_name": "Gamble", "given_name": "Ronald C.", "clpid": "Gamble-R-C" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "When unilamellar vesicles were administered subcutaneously in mice, the half-time for the destruction of the vesicles varied from 12 to 600 hours, depending on their composition. The vesicles tested consisted of distearoyl phosphatidylcholine, cholesterol, and certain sugar and amino-sugar derivatives of cholesterol. Vesicles with amino-sugar derivatives showed the greatest longevity and became localized with high specificity in aggregates of polymorphonuclear leukocytes. A substantial delay between the time that the vesicles broke open and the time that labels contained in the vesicles were excreted suggests that the vesicles undergo endocytosis before destruction.", "doi": "10.1126/science.7350660", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "1980-01-18", "series_number": "4428", "volume": "207", "issue": "4428", "pages": "309-311" }, { "id": "authors:ngw8p-8td80", "collection": "authors", "collection_id": "ngw8p-8td80", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:GAMrsi79", "type": "article", "title": "Linear position-sensitive x-ray detector incorporating a self-scanning photodiode array", "author": [ { "family_name": "Gamble", "given_name": "Ronald C.", "clpid": "Gamble-R-C" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" }, { "family_name": "Giffin", "given_name": "Charles E.", "clpid": "Giffin-C-E" } ], "abstract": "A linear position-sensitive x-ray detector for x-ray spectroscopy and diffraction applications has been tested which can provide excellent spatial resolution, wide dynamic range and good sensitivity. The heart of the system is a self-scanning, photosensitive silicon diode array. It is interfaced via fiber optics to a thin layer of ZnS which fluoresces visible light upon absorption of x-radiation. The conversion to visible light and optical coupling provide several-fold gain in the efficiency of detection as compared to the direct detection of x-ray by the diode array. Equally important is that the array is protected from irreversible damage by high energy radiation, a limitation which previously hindered this application of silicon diode technology.", "doi": "10.1063/1.1135730", "issn": "0034-6748", "publisher": "Review of Scientific Instruments", "publication": "Review of Scientific Instruments", "publication_date": "1979-11-01", "series_number": "11", "volume": "50", "issue": "11", "pages": "1416-1420" }, { "id": "authors:xv4fv-bjd22", "collection": "authors", "collection_id": "xv4fv-bjd22", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120802-145502429", "type": "article", "title": "Remotely controlled mirror of variable geometry for small angle x-ray diffraction with synchrotron radiation", "author": [ { "family_name": "Webb", "given_name": "N. G.", "clpid": "Webb-N-G" }, { "family_name": "Samson", "given_name": "S.", "clpid": "Samson-S" }, { "family_name": "Stroud", "given_name": "R. M.", "orcid": "0000-0003-2083-5665", "clpid": "Stroud-Robert-M" }, { "family_name": "Gamble", "given_name": "R. C.", "clpid": "Gamble-Ronald-C" }, { "family_name": "Baldeschwieler", "given_name": "J. D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "A total-reflecting mirror of 120-cm length was designed and built to focus synchrotron radiation emanating from the electron-positron storage ring at the Stanford Linear Accelerator Center (SPEAR). The reflecting surface is of\nunpolished float glass. The bending and tilt mechanism allows very fine control of the curvature and selectability of the critical angle for wavelengths ranging from 0.5 to 3.0 \u00c5. Elliptical curvature is used to minimize aberrations. The mirror is placed asymmetrically onto the ellipse so as to achieve a tenfold demagnification of the source. The bending mechanism reduces nonelastic\ndeformation (flow) and minimizes strains and stresses in the glass despite its length. Special design features assure stability of the focused image. The mirror\nreduces the intensity of shorter wavelength harmonics by a factor of approximately 100.", "doi": "10.1063/1.1134749", "issn": "0034-6748", "publisher": "American Institute of Physics", "publication": "Review of Scientific Instruments", "publication_date": "1976-07", "series_number": "7", "volume": "47", "issue": "7", "pages": "836-839" }, { "id": "authors:1pymp-qqn45", "collection": "authors", "collection_id": "1pymp-qqn45", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:MEApnas72", "type": "article", "title": "Perturbed angular correlation study of a haptenic molecule", "author": [ { "family_name": "Meares", "given_name": "Claude F.", "clpid": "Meares-C-F" }, { "family_name": "Sundberg", "given_name": "Michael W.", "clpid": "Sundberg-M-W" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "The angular correlation of the 173-247 keV gamma-ray cascade after the electron-capture decay of (111)In is strongly perturbed when the I-p-nitrophenylethylenediaminetetraacetate chelate of (111)In(3+) is added to a solution containing rabbit antibody to dinitrophenyl groups. The radioactive chelate can be displaced by the addition of dinitrophenyllysine or unlabeled chelate. The average association constant between the antibody and the labeled chelate has been estimated from perturbed angular correlation measurements; this value is compared to the results of equilibrium dialysis. These experiments provide good evidence that information concerning macromolecular behavior can be obtained from perturbed angular correlation experiments that use chemically specific labels.", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "1972-12-01", "series_number": "12", "volume": "69", "issue": "12", "pages": "3718-3722" }, { "id": "authors:fpmhg-79s27", "collection": "authors", "collection_id": "fpmhg-79s27", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:MEApnas69", "type": "article", "title": "Study of carbonic anhydrase using perturbed angular correlations of gamma radiation", "author": [ { "family_name": "Meares", "given_name": "Claude F.", "clpid": "Meares-C-F" }, { "family_name": "Bryant", "given_name": "Robert G.", "clpid": "Bryant-R-G" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" }, { "family_name": "Shirley", "given_name": "David A.", "clpid": "Shirley-D-A" } ], "abstract": "The angular correlation of the 150-247 kev gamma-ray cascade of (111m)Cd is strongly perturbed when this nucleus is bound to the enzyme carbonic anhydrase. A comparison of the perturbed angular correlation for the apoenzyme with that for native carbonic anhydrase confirms that the (111m)Cd binds at the active region of the enzyme. These results provide good evidence that the perturbed angular correlation reflects the effective molecular rotational correlation time at the metal binding site, and that this radioactive nucleus can be used as a rotational tracer to label biological macromolecules. The qualitative dependence of the perturbed angular correlation of the (111m)Cd cascade on the molecular rotational correlation time at the metal binding site is illustrated using a cadmium-complex solution at various temperatures.", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "1969-12-01", "series_number": "4", "volume": "64", "issue": "4", "pages": "1155-1161" }, { "id": "authors:fmhy2-d6742", "collection": "authors", "collection_id": "fmhy2-d6742", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:ANDjcp66", "type": "article", "title": "Ion-Cyclotron Double Resonance", "author": [ { "family_name": "Anders", "given_name": "L. R.", "clpid": "Anders-L-R" }, { "family_name": "Beauchamp", "given_name": "J. L.", "orcid": "0000-0001-8839-4822", "clpid": "Beauchamp-J-L" }, { "family_name": "Dunbar", "given_name": "R. C.", "clpid": "Dunbar-R-C" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "A charged particle in a uniform moving magnetic field H describes a circular orbit in a plance perpendicular to H with an angular frequency or \"cyclotron frequency\" omagae. When an alternating electric field E(t) is applied normal to H at omegae, the ions absorb energy from the alternating electric field, and are accelerated to larger velocities and orbital radii. [1] The absorption of energy from E(t) at the cyclotron resonance frequency can be conveniently detected using a marginal oscillator detector. When the ions accelerated by E(t) collide with other particles, they lose some of their excess energy. A mixture of ions and neutral molecules in the presence of H and E(t) then reaches a steady-state condition in which the energy gained by the ions from E(t) between collisions is lost to the neutral molecules in collisions.", "doi": "10.1063/1.1727658", "issn": "0021-9606", "publisher": "American Institute of Physics", "publication": "Journal of Chemical Physics", "publication_date": "1966-08-01", "series_number": "3", "volume": "45", "issue": "3", "pages": "1062-1063" }, { "id": "authors:c04ss-daa68", "collection": "authors", "collection_id": "c04ss-daa68", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:STEpnas66", "type": "article", "title": "Halide ions as chemical probes for NMR studies of proteins", "author": [ { "family_name": "Stengle", "given_name": "Thomas R.", "clpid": "Stengle-T-R" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "abstract": "There has been considerable recent interest in the application of nuclear magnetic resonance techniques to the study of biological macromolecules.(1) NMR is in general not sufficiently sensitive for the direct study of biomolecules in solution at realistic concentrations. Some of the most promising developments have therefore involved the use of nuclear relaxation effects to probe gross molecular structural features.(2) These techniques frequently rely on the effects of small concentrations of paramagnetic atoms on the relaxation times of solvent nuclei,(3-5) or on the binding and exchange of small molecules with proteins.(6) Although paramagnetic relaxation effects have been widely exploited to yield structural information on relatively simple inorganic complexes in solution,(7-9) these techniques usually suffer from the inherent complexity of the relaxation process.(2) The observed effects on nuclear relaxation are usually the result of several competing mechanisms of comparable significance, which makes interpretation of line shapes in terms of molecular events hazardous.", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "1966-05-01", "series_number": "5", "volume": "55", "issue": "5", "pages": "1020-1025" }, { "id": "authors:gdyk7-typ60", "collection": "authors", "collection_id": "gdyk7-typ60", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:NAGpr65b", "type": "article", "title": "Nuclear magnetic double-resonance spectrum of a strongly coupled two-spin system", "author": [ { "family_name": "Nageswara Rao", "given_name": "B. D.", "clpid": "Nageswara-Rao-B-D" }, { "family_name": "Baldeschwieler", "given_name": "J. D.", "clpid": "Baldeschwieler-J-D" }, { "family_name": "Anderson", "given_name": "J. M.", "clpid": "Anderson-J-M" } ], "abstract": "The density-matrix theory of double resonance is applied for a detailed analysis of the frequency-sweep nuclear magnetic double-resonance spectra of the strongly coupled two-proton system in 2-bromo-5-chlorothiophene under various conditions of irradiation. These spectra show significant relaxation and coherence effects. The results of the theory are very sensitive to the relaxation mechanisms assumed for the system, indicating the possibility of deriving significant information about the relaxation of the system by this method. Comparison of the observed and theoretical double-resonance spectra shows that the proton relaxation in this molecule is due, in large measure, to external interactions with a high degree of correlation between the interactions with the two protons. An approximation proposed by Bloch for simplifying the calculations is found to be applicable even when the irradiation frequency is close to some single-resonance transition frequencies.", "doi": "10.1103/PhysRev.137.A1477", "issn": "0031-899X", "publisher": "American Physical Society", "publication": "Physical Review", "publication_date": "1965-03-01", "series_number": "5A", "volume": "137", "issue": "5A", "pages": "A1477-A1482" }, { "id": "authors:25gvp-7pb98", "collection": "authors", "collection_id": "25gvp-7pb98", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:ANDjcp63", "type": "article", "title": "Long-Range N14 Coupling in Ethyl Ammonium Ions", "author": [ { "family_name": "Anderson", "given_name": "J. M.", "clpid": "Anderson-J-M" }, { "family_name": "Baldeschwieler", "given_name": "J. D.", "clpid": "Baldeschwieler-J-D" }, { "family_name": "Dittmer", "given_name": "D. C.", "clpid": "Dittmer-D-C" }, { "family_name": "Phillips", "given_name": "W. D.", "clpid": "Phillips-W-D" } ], "abstract": "There has been considerable interest recently in the magnitudes and relative signs of CH3-X and CH2-X coupling constants in compounds of the type (CH3CH2)nX [2-6]. We wish to report the analysis of the spectra of N(CH2CH3)4+ and N(C2H5)3(CH2SCH3)+ and the confirmation of the assignments of these spectra by H1-{N14} [1] double resonance and by the temperature dependence of the proton spectra.", "doi": "10.1063/1.1733840", "issn": "0021-9606", "publisher": "Journal of Chemical Physics", "publication": "Journal of Chemical Physics", "publication_date": "1963-03-01", "series_number": "5", "volume": "38", "issue": "5", "pages": "1260-1261" } ]