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Chemistry Faculty Publications

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Articles 961 - 990 of 1129

Full-Text Articles in Chemistry

Measurement Of The Anti-Cancer Agent Gemcitabine In Human Plasma By High-Performance Liquid Chromatography, Bruce Keith, Yan Xu, Jean L. Grem Feb 2003

Measurement Of The Anti-Cancer Agent Gemcitabine In Human Plasma By High-Performance Liquid Chromatography, Bruce Keith, Yan Xu, Jean L. Grem

Chemistry Faculty Publications

A reversed-phase HPLC assay has been developed to determine the concentration of the anti-metabolite 2′,2′-difluorodeoxycytidine (gemcitabine, dFdC) in human plasma over the concentration range of 0.5–150 μM (0.13–39.44 μg/ml), and 2′,2′-difluorodeoxyuridine (dFdU), the deaminated, inactive metabolite, over the range of 1.0–227 μM (0.26–60 μg/ml). After the addition of 20 nmol 2′-fluorodeoxycytidine (FdC) as an internal standard, 0.5-ml samples of plasma were subjected to acetonitrile precipitation, followed by analysis using a gradient reversed-phase HPLC assay with UV detection. A Phenomenex Columbus™ C18 column, 5 μm, 150×4.6 mm, and a Waters C18, 4 μm, Nova-Pak Sentry guard column were used to achieve …

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Particle Growth In Urban And Industrial Plumes In Texas, Charles A. Brock, Michael Trainer, Thomas B. Ryerson, J. Andrew Neuman, David D. Parrish, John S. Holloway, Dennis K. Nicks, Gregory J. Frost, Gerhard Hübler, Fred C. Fehsenfeld, J. Charles Wilson, J. Michael Reeves, Bernard G. Lafleur, Henrike Hilbert, Elliot L. Atlas, Stephen G. Donnelly Ph.D., Sue M. Schauffler, Verity R. Stroud, Christine Wiedinmyer Feb 2003

Particle Growth In Urban And Industrial Plumes In Texas, Charles A. Brock, Michael Trainer, Thomas B. Ryerson, J. Andrew Neuman, David D. Parrish, John S. Holloway, Dennis K. Nicks, Gregory J. Frost, Gerhard Hübler, Fred C. Fehsenfeld, J. Charles Wilson, J. Michael Reeves, Bernard G. Lafleur, Henrike Hilbert, Elliot L. Atlas, Stephen G. Donnelly Ph.D., Sue M. Schauffler, Verity R. Stroud, Christine Wiedinmyer

Chemistry Faculty Publications

Particle size distributions and gas-phase particle precursors and tracer species were measured aboard an aircraft in the plumes downwind from industrial and urban sources in the vicinity of Houston, TX during the daytime in late August and early September 2000. Plumes originating from the Parish gas-fired and coal-fired power plant, petrochemical industries along the Houston ship channel, the petrochemical facilities near the Gulf coast, and the urban center of Houston were studied. Most of the particle mass flux advected downwind of Houston came from the industries and electrical utilities at the periphery of the city rather than from sources in …

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Examination Of The Role Of The Clamp-Loader And Atp Hydrolysis In The Formation Of The Bacteriophage T4 Polymerase Holoenzyme, Michael A. Trakselis, Anthony J. Berdis, Stephen J. Benkovic Feb 2003

Examination Of The Role Of The Clamp-Loader And Atp Hydrolysis In The Formation Of The Bacteriophage T4 Polymerase Holoenzyme, Michael A. Trakselis, Anthony J. Berdis, Stephen J. Benkovic

Chemistry Faculty Publications

Transient kinetic analyses further support the role of the clamp-loader in bacteriophage T4 as a catalyst which loads the clamp onto DNA through the sequential hydrolysis of two molecules of ATP before and after addition of DNA. Additional rapid-quench and pulse-chase experiments have documented this stoichiometry. The events of ATP hydrolysis have been related to the opening/closing of the clamp protein through fluorescence resonance energy transfer (FRET). In the absence of a hydrolysable form of ATP, the distance across the subunit interface of the clamp does not increase as measured by intramolecular FRET, suggesting gp45 cannot be loaded onto DNA. …

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Synthesis And Potential Antimetastatic Activity Of Monovalent And Divalent Β-D-Galactopyranosyl-(1→4)-2-Acetamido-2-Deoxy-D-Glucopyranosides, Qin Li, Bin Su, Hui Li, Xiang Bao Meng, Meng Shen Cai, Zhong Jun Li, Rou Li Zhou, Ta Lin Suo Jan 2003

Synthesis And Potential Antimetastatic Activity Of Monovalent And Divalent Β-D-Galactopyranosyl-(1→4)-2-Acetamido-2-Deoxy-D-Glucopyranosides, Qin Li, Bin Su, Hui Li, Xiang Bao Meng, Meng Shen Cai, Zhong Jun Li, Rou Li Zhou, Ta Lin Suo

Chemistry Faculty Publications

Anomers of monovalent and divalent β-d-galactopyranosyl-(1→4)-2-acetamido-2-deoxy-d-gluco-pyranosides were synthesized under different glycosylation conditions, and evaluated for in vitro antimetastatic activity. Three compounds showed promising inhibitory effects on cancer cell attachment, spreading, migration, and invasion. Six divalent O-β-d-galactopyranosyl-(1→4)-2-acetamido-2-deoxy-d-glucopyranosides (29–34) were synthesized and their antimetastatic activities were studied.

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Liquid Chromatography–Mass Spectrometry Method For The Analysis Of The Anti-Cancer Agent Capecitabine And Its Nucleoside Metabolites In Human Plasma, Yan Xu, Jean L. Grem Jan 2003

Liquid Chromatography–Mass Spectrometry Method For The Analysis Of The Anti-Cancer Agent Capecitabine And Its Nucleoside Metabolites In Human Plasma, Yan Xu, Jean L. Grem

Chemistry Faculty Publications

A reversed-phase high-performance liquid chromatography method with electrospray ionization and mass spectral detection is described for the determination of capecitabine, 5′-deoxy-5-fluorocytidine and 5′-deoxy-5-fluorouridine in human plasma with 5-chloro-2′-deoxyuridine as the internal standard. An on-line sample clean-up procedure allows dilution of the plasma sample with the initial mobile phase. The linear dynamic range is 0.0500–10.0 μg/ml for capecitabine, and 0.0500–25.0 μg/ml for the metabolites, 5′-deoxy-5-fluorocytidine and 5′-deoxy-5-fluorouridine, respectively. This method has been used to analyze plasma samples from patients receiving capecitabine in combination with oxaliplatin.

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Anion Photoelectron Spectroscopy Of Solvated Transition State Precursors, Harry Gomez, Giovanni Meloni, James Madrid, D M. Neumark Jan 2003

Anion Photoelectron Spectroscopy Of Solvated Transition State Precursors, Harry Gomez, Giovanni Meloni, James Madrid, D M. Neumark

Chemistry Faculty Publications

Photoelectron (PE) spectra have been collected for the clustered bihalide anions XHX−∙(M) (X=Br, I) and BrHI−∙(M), where M=H2O, HBr, and HI, in order to probe the effects of strongly solvating species on the PE spectra of transition state precursor anions. The PE spectra of the XHX−∙(H2O) ions show similar vibrational progressions as the spectra of the bare BrHBr− and IHI− anions, indicating that photodetachment of the bare and hydrated ions accesses similar XHX transition state geometries on the X+HX reactionpotential energy surfaces. These results are consistent with electronic structure calculations that predict a double hydrogen-bonded XHX−∙(H2O) structure in which the …

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Response To “Comment On ‘Atomization Energies And Enthalpies Of Formation Of The Snbi[Sub N] (N=1–3) Gaseous Molecules By Knudsen Cell Mass Spectrometry’ ” [J. Chem. Phys. 118, 4766 (2003)], Giovanni Meloni, Karl A. Gingerich Jan 2003

Response To “Comment On ‘Atomization Energies And Enthalpies Of Formation Of The Snbi[Sub N] (N=1–3) Gaseous Molecules By Knudsen Cell Mass Spectrometry’ ” [J. Chem. Phys. 118, 4766 (2003)], Giovanni Meloni, Karl A. Gingerich

Chemistry Faculty Publications

Discusses atomization energies and enthalpies of formation of gaseous molecules of compounds containing tin and bismuth by Knudsen cell mass spectrometry. Procedure followed to evaluate the mass spectrometric equilibrium data regarding these molecules; Statistics of atomization energies and enthalpies calculated; Factors contributing to the necessity of high level of calculations to obtain these figures.

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Self-Aggregates Of Cationic Meso-Tetratolylporphyrins In Aqueous Solutions, Pavel Kubat, Kamil Lang, Kristina Prochazkova, Pavel Anzenbacher Jr. Jan 2003

Self-Aggregates Of Cationic Meso-Tetratolylporphyrins In Aqueous Solutions, Pavel Kubat, Kamil Lang, Kristina Prochazkova, Pavel Anzenbacher Jr.

Chemistry Faculty Publications

Aggregation properties of meso-tetratolylporphyrins bearing cationic substituents of a lipophilic nature such as ammonium, pyridinium, phosphonium, sulfonium, and isothiouronium were studied by UV/vis and resonance light scattering spectroscopy. The exciton point-dipole approximation was used to predict the structural alignment of the porphyrin units within the aggregate. The contribution of various types of aggregates depends on the porphyrin substitution, ionic strength, and temperature of aqueous solution of the porphyrin. In general, the preferred structure of an aggregate formed by temperature-induced aggregation is the J-aggregate exhibiting the characteristically narrow, red-shifted Soret band indicating a parallel "side-by-side" arrangement of the porphyrin units. The …

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Photoinduced Electron-Transfer Along Α-Helical And Coiled-Coil Metallopeptides, Anna Fedorova, Anita Chaudhari, Michael Y. Ogawa Jan 2003

Photoinduced Electron-Transfer Along Α-Helical And Coiled-Coil Metallopeptides, Anna Fedorova, Anita Chaudhari, Michael Y. Ogawa

Chemistry Faculty Publications

A peptide-based electron-transfer system has been designed in which the specific positions of redox-active metal complexes appended to either an a-helix, or an a-helical coiled-coil, can be reversed to test the effect of the helix dipole in controlling photoinduced electron-transfer rates. Two 30-residue apopeptides were prepared having the following sequences: (1) Ac-K-(IEALEGK)(ICALEGK)(IEALEHK)-(IEALEGK)-G-amide, and (II) Ac-K-(IEALEGK)(IHALEGK)-(IEALECK)(IEALEGK)-G-amide. Each apopeptide was reacted first with [Ru(bpy)(2)(phen-ClAc)](2+), where bpy = 2,2'-bipyridine and phen-ClAc = 5-chloroacetamido-1,10-phenanthroline, to attach the ruthenium polypyridyl center to the cysteine side-chain of the polypeptide. The isolated products were then reacted with [Ru(NH3)(5)(H2O)](2+) to yield the binuclear electron-transfer metallopeptides ET-I and ET-II. …

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A Phase I And Pharmacologic Study Of Weekly Gemcitabine In Combination With Infusional 5-Fluorodeoxyuridine And Oral Calcium Leucovorin, Jean L. Grem, Mary G. Quinn, Bruce Keith, Brian P. Monahan, J. Michael Hamilton, Yan Xu, Nancy Harold, Dat Nguyen, Chris H. Takimoto, Anthony Rowedder, Janet Pang, Geraldine Morrison, Alice Chen Jan 2003

A Phase I And Pharmacologic Study Of Weekly Gemcitabine In Combination With Infusional 5-Fluorodeoxyuridine And Oral Calcium Leucovorin, Jean L. Grem, Mary G. Quinn, Bruce Keith, Brian P. Monahan, J. Michael Hamilton, Yan Xu, Nancy Harold, Dat Nguyen, Chris H. Takimoto, Anthony Rowedder, Janet Pang, Geraldine Morrison, Alice Chen

Chemistry Faculty Publications

Purpose: Since preclinical studies have shown more than additive cytotoxicity and DNA damage with the combination of gemcitabine and 5-fluoro-2′-deoxyuridine (FUDR), we studied this combination in a phase I trial. Methods: Gemcitabine alone was given in cycle 1 as a 24-h, 2-h or 1-h i.v. infusion weekly for 3 of 4 weeks; if tolerated, a 24-h i.v. infusion of FUDR was added with oral leucovorin. The cycle was aborted for grade 3 thrombocytopenia, grade 4 neutropenia, and grade 2 or worse nonhematologic toxicity. Results: During cycle 1, six of eight patients who received 150 or 100 mg/m2 over 24 h …

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Utilizing Structure Property Correlations To Predict And Analyze Two Derivatives Of An Ampicillin Homologous Series, C. Malesa, J. Stoddard, Ronald Bartzatt Jan 2003

Utilizing Structure Property Correlations To Predict And Analyze Two Derivatives Of An Ampicillin Homologous Series, C. Malesa, J. Stoddard, Ronald Bartzatt

Chemistry Faculty Publications

Structure Property Correlation methods such as regression analysis and pattern recognition are applied to predict the molecular properties of two members of an ampicillin homologous series. The pentyl and hexyl esters of ampicillin are also evaluated for their similarity to other penicillins by use of multiple regression, contingency tables, cluster analysis, correspondence analysis, self organizing tree algorithms, factor analysis, principal component analysis, box plots, and other graphing methods. Other members of the homologous series include methyl, ethyl, propyl, and butyl esters of ampicillin which have been previously synthesized and tested in tissue culture against Escherichia coli. All of the tested …

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Possible Cobalt-Cobalt Bridging By A Hemiacetal In The Dinuclear Cobalt Complex Bearing The Ligand Bis(3-(2-Pyridylmethyleneamino)Phenyl) Sulfone, Armando M. Guidote Jr, Tomoko Imajo, Yasuhiko Kurusu, Yoshiro Masuyama Jan 2003

Possible Cobalt-Cobalt Bridging By A Hemiacetal In The Dinuclear Cobalt Complex Bearing The Ligand Bis(3-(2-Pyridylmethyleneamino)Phenyl) Sulfone, Armando M. Guidote Jr, Tomoko Imajo, Yasuhiko Kurusu, Yoshiro Masuyama

Chemistry Faculty Publications

A dinuclear cobalt complex bearing the ligand bis(3-(2-pyridylmethyleneamino)phenyl) sulfone (BPMAPS) was prepared. It is proposed that the structure of this is [Coz(BPMAPS)(m-0AcMhemi-Et)]PF6 wherein the cobalt centers are bridged by two carboxylato groups in m-fashion and a hemiacetal with an ethoxy group (hemi-Et). This proposal is based on the similarity of the FT-IR, UV-Vis, and FAB-MS results with the crystallographically characterized dinuclear manganese complex [Mn2(BPMAPS)(m-OAcMhemi-Me)]PF6, and elemental analysis results.

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Simulations Of Quantized Double Layer Charging Voltammetry Of Poly Disperse And Mono-Disperse Monolayer Protected Clusters, Deon T. Miles, Michael C. Leopold, Jocelyn F. Hicks, Royce W. Murray Jan 2003

Simulations Of Quantized Double Layer Charging Voltammetry Of Poly Disperse And Mono-Disperse Monolayer Protected Clusters, Deon T. Miles, Michael C. Leopold, Jocelyn F. Hicks, Royce W. Murray

Chemistry Faculty Publications

This paper describes simulated differential pulse voltammetry (DPV) of quantized double-layer charging (QDL) in poly-disperse monolayer-protected gold cluster (MPC) solutions. The simulation accounts for the voltage spacing between QDL peaks with a concentric sphere capacitor model, in which core sizes, and the relative proportion of each size, are input using transmission electron microscopy (TEM) data. MPC diffusion coefficients are estimated from hydrodynamic radii, and peaks are broadened to account for DPV pulse height effects. The smallest MPCs are omitted from the simulation because electrochemical HOMO/LUMO gap information is uncertain. The largest ones are shown to produce the underlying DPV current …

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Urer, The Transcriptional Activator Of The Proteus Mirabilis Urease Gene Cluster, Is Required For Urease Activity And Virulence In Experimental Urinary Tract Infections, Jonathan D. Dattelbaum, C. Virginia Lockatell, David E. Johnson, Harry L.T. Mobley Jan 2003

Urer, The Transcriptional Activator Of The Proteus Mirabilis Urease Gene Cluster, Is Required For Urease Activity And Virulence In Experimental Urinary Tract Infections, Jonathan D. Dattelbaum, C. Virginia Lockatell, David E. Johnson, Harry L.T. Mobley

Chemistry Faculty Publications

Proteus mirabilis, a cause of complicated urinary tract infection, produces urease, an essential virulence factor for this species. UreR, a member of the AraC/XylS family of transcriptional regulators, positively activates expression of the ure gene cluster in the presence of urea. To specifically evaluate the contribution of UreR to urease activity and virulence in the urinary tract, a ureR mutation was introduced into P. mirabilis HI4320 by homologous recombination. The isogenic ureR::aphA mutant, deficient in UreR production, lacked measurable urease activity. Expression was not detected in the UreR-deficient strain by Western blotting with monoclonal antibodies raised against UreD. Urease …

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Hplc Of Monolayer-Protected Gold Nanoclusters, Victoria L. Jimenez,, Michael C. Leopold, Carolyn Mazzitelli, James W. Jorgenson, Royce W. Murray Dec 2002

Hplc Of Monolayer-Protected Gold Nanoclusters, Victoria L. Jimenez,, Michael C. Leopold, Carolyn Mazzitelli, James W. Jorgenson, Royce W. Murray

Chemistry Faculty Publications

Polydisperse samples of Au nanoparticles protected with monolayers of hexanethiolate ligands (C6 MPCs) and with mixed monolayers of hexanethiolate and mercaptounde- canoic acid (C6/MUA MPCs) have been chromatographically separated using C8 120-Å columns and acetone/toluene mobile phase. The spectral details of eluted peaks and of quantized double-layer charging features in the differential pulse voltammetry of collected fractions were used to show that the elution orders of C6 MPC mixtures and of C6/MUA MPC mixtures were different. For C6 MPCs, the smallest MPCs were eluted first, whereas the smallest C6/MUA MPCs were eluted last. The reversal of order of elution was …

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Synthesis Of A Spacer-Armed Disulfated Tetrasaccharide Of Sb1a, A Carbohydrate Hapten Associated With Human Hepatocellular Carcinoma, Qin Li, Hui Li, Qing Li, Qing Hua Lou, Bin Su, Meng Shen Cai, Zhong Jun Li Nov 2002

Synthesis Of A Spacer-Armed Disulfated Tetrasaccharide Of Sb1a, A Carbohydrate Hapten Associated With Human Hepatocellular Carcinoma, Qin Li, Hui Li, Qing Li, Qing Hua Lou, Bin Su, Meng Shen Cai, Zhong Jun Li

Chemistry Faculty Publications

A disulfated tetrasaccharide fragment with a spacer arm of human hepatocellular carcinoma carbohydrate antigen SB1a, namely, 2-aminoethyl 3-O-sulfo-β-d-galactopyranosyl-(1→3)-2-acetamido-2-deoxy-β-d-galactopyranosyl-(1→4)-3-O-sulfo-β-d-galactopyranosyl-(1→4)-β-d-glucopyranoside was synthesized via a [2+1+1] block building mode. In the last coupling step toward the trisaccharide acceptor 8, benzoyl protected galactosyl bromide donor 14 was found to be much more reactive than the acetyl-protected donors. A disulfated tetrasaccharide fragment with a spacer arm of human hepatocellular carcinoma carbohydrate antigen SB1a was synthesized via a [2+1+1] block building mode.

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Rapid Determination Of Serum Melatonin By Esi–Ms–Ms With Direct Sample Injection, Shuming Yang, Xiaohui Zheng, Yan Xu, Xiang Zhou Oct 2002

Rapid Determination Of Serum Melatonin By Esi–Ms–Ms With Direct Sample Injection, Shuming Yang, Xiaohui Zheng, Yan Xu, Xiang Zhou

Chemistry Faculty Publications

This paper describes a rapid, simple and sensitive analytical method for the quantitative determination of melatonin in human serum by ESI–MS–MS with direct serum sample injection and on-line extraction. The method uses N-acetyltryptamine as the internal standard. It has high specificity and sensitivity for serum melatonin analysis. The internal calibration curve shows a wide linear range from 0.500 to 200 ng/ml with a correlation coefficient, R2>0.999. The limit of quantitation is 0.500 ng/ml and the limit of detection is 0.100 ng/ml with 10-μl sample injection. The recoveries of serum melatonin at three levels are approximately 70%. The intra-assay precision …

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A Comparison Of The Low Mode And Monte Carlo Conformational Search Methods, Carol A. Parish, Rosina Lombardi, Kent Sinclair, Emelyn Smith, Alla Goldberg, Melissa Rappleye, Myrianne Dure Oct 2002

A Comparison Of The Low Mode And Monte Carlo Conformational Search Methods, Carol A. Parish, Rosina Lombardi, Kent Sinclair, Emelyn Smith, Alla Goldberg, Melissa Rappleye, Myrianne Dure

Chemistry Faculty Publications

The Low Mode (LM) and Monte Carlo (MC) conformational search methods were compared on three diverse molecular systems; (4R, 5S, 6S, 7R)-hexahydro-5,6-dihydroxy-1,3,4,7-tetrakis(phenylmethyl)-2H-1,3-diazapin-2-one (1), 2-methoxy-2-phenyl-2-triflouromethyl-N-α-methyl benzyl propanamide (2) and a trimeric 39-membered polyazamacrolide (3). We find that either method, or a combination of the methods, is equally efficient at searching the conformational space of the smaller molecular systems while a 50:50 hybrid of Low Mode and Monte Carlo is most efficient at searching the space of the larger molecular system.

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Monte Carlo Simulation On The Indirect Exchange Interactions Of Co-Doped Zno Film, Scott Whittenburg Sep 2002

Monte Carlo Simulation On The Indirect Exchange Interactions Of Co-Doped Zno Film, Scott Whittenburg

Chemistry Faculty Publications

Monte Carlo simulations using a three-dimensional lattice model studied the Ruderman–Kittel–Kasuya–Yosida (RKKY) indirect exchange interaction of doped magnetic Co ions in ZnO films. The results of the calculations show that the RKKY interaction in Co-doped ZnO is long ranged and its magnitude is proportional to R−1 (inverse of the distance R from a central Co2+ ion). The sign oscillates with a frequency that depends on the concentration of the carrier. The long-distance sum of the RKKY indirect exchange energies is positive indicating that these materials are ferromagnetic, in direct correlation with previously reported results

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Determination Of Barbituric Acid, Utilizing A Rapid And Simple Colorimetric Assay, Ronald Bartzatt Jul 2002

Determination Of Barbituric Acid, Utilizing A Rapid And Simple Colorimetric Assay, Ronald Bartzatt

Chemistry Faculty Publications

Barbituric acid is widely used in the manufacturing of plastics, textiles, polymers, and pharmaceuticals. Three assay methods are presented, which can utilize either aqueous or solid samples. The detection of as little as 10 μg of barbituric acid can be accomplished, either as an aqueous or solid sample, when using micro reaction tubes. The red–violet endpoint is easily discerned and results upon the formation of a violuric acid derivative. A Spot Test protocol is described which allows for a positive/negative indication of barbituric acid presence. The Spot Test is sensitive to as little as 18.75 μg/ml of barbituric acid. The …

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Preprogramming Of Porphyrin−Nucleic Acid Assemblies Via Variation Of The Alkyl/Aryl Substituents Of Phosphonium Tetratolylporphyrins, Pavel Kubat, Kamil Lang, Vladimir Kral, Pavel Anzenbacher Jr. Jul 2002

Preprogramming Of Porphyrin−Nucleic Acid Assemblies Via Variation Of The Alkyl/Aryl Substituents Of Phosphonium Tetratolylporphyrins, Pavel Kubat, Kamil Lang, Vladimir Kral, Pavel Anzenbacher Jr.

Chemistry Faculty Publications

Cationic alkyl/arylphosphonium meso-tetratolylporphyrins aggregate in an aqueous solution to form H-aggregates, J-aggregates, and long-range assemblies. The ratio between the monomer and various types of aggregates can be controlled by the substitution in the phosphonium units and by the ionic strength. A trimethylphosphonium derivative is predominantly monomeric, dimethylphenylphosphonium forms monomers as well as low-molecular-weight H- and J-aggregates, triphenylphosphonium forms mainly H- and J-aggregates, and tri(n-butyl)phosphonium forms mainly long-range assemblies. Porphyrin monomers associate with calf thymus DNA (binding constant Kb approximate to 10(7) M-1) and oligonucleotides (K-b approximate to 10(5-)10(6) M-1). The large size of the meso-substituents prevents the intercalation between base …

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Electron Hopping Conductivity And Vapor Sensing Properties Of Flexible Network Polymer Films Of Metal Nanoparticles, Francis P. Zamborini, Michael C. Leopold, Jocelyn F. Hicks, Pawel J. Kulesza, Marcin A. Malik, Royce W. Murray Jun 2002

Electron Hopping Conductivity And Vapor Sensing Properties Of Flexible Network Polymer Films Of Metal Nanoparticles, Francis P. Zamborini, Michael C. Leopold, Jocelyn F. Hicks, Pawel J. Kulesza, Marcin A. Malik, Royce W. Murray

Chemistry Faculty Publications

Films of monolayer protected Au clusters (MPCs) with mixed alkanethiolate and ω-carboxylate alkanethiolate monolayers, linked together in a network polymer by carboxylate-Cu2+-carboxylate bridges, exhibit electronic conductivities (σEL) that vary with both the numbers of methylene segments in the ligands and the bathing medium (N2, liquid or vapor). A chainlength-dependent swelling/contraction of the film's internal structure is shown to account for changes in σEL. The linker chains appear to have sufficient flexibility to collapse and fold with varied degrees of film swelling or dryness. Conductivity is most influenced (exponentially dependent) by the chainlength of the nonlinker (alkanethiolate) ligands, a result consistent …

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Computational Simulation Of The Docking Of Prochlorothrix Hollandica Plastocyanin To Photosystem I: Modeling The Electron Transfer Complex, Neocles B. Leontis, Eugene Myshkin, George S. Bullerjahn Jun 2002

Computational Simulation Of The Docking Of Prochlorothrix Hollandica Plastocyanin To Photosystem I: Modeling The Electron Transfer Complex, Neocles B. Leontis, Eugene Myshkin, George S. Bullerjahn

Chemistry Faculty Publications

We have used several docking algorithms (GRAMM, FTDOCK, DOT, AUTODOCK) to examine protein-protein interactions between plastocyanin (Pc)/photosystem I (PSI) in the electron transfer reaction. Because of the large size and complexity of this system, it is faster and easier to use computer simulations than conduct x-ray crystallography or nuclear magnetic resonance experiments. The main criterion for complex selection was the distance between the copper ion of Pc and the P700 chlorophyll special pair. Additionally, the unique tyrosine residue (Tyr(12)) of the hydrophobic docking surface of Prochlorothrix hollandica Pc yields a specific interaction with the lumenal surface of PSI, thus providing …

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Luminescence Lifetime-Based Sensor For Cyanide And Related Anions, Pavel Anzenbacher Jr., Daniel S. Tyson, Karolina Jursı´Kova, Felix N. Castellano Jun 2002

Luminescence Lifetime-Based Sensor For Cyanide And Related Anions, Pavel Anzenbacher Jr., Daniel S. Tyson, Karolina Jursı´Kova, Felix N. Castellano

Chemistry Faculty Publications

A new Ru(II) complex is described which serves as a luminescence lifetime-based sensor for fluoride and cyanide anions (KF = 640 000 mol-1, KCN = 430 000 mol-1). This chromophore displays observable changes in its UV-vis and steady-state luminescence spectra upon cyanide binding. Prior to cyanide addition, this complex exhibits a single-exponential lifetime (tau = 377 +/- 20 ns). With increasing cyanide concentrations, the intensity decays are composed of two exponentials: long tau (320-370 ns) and short tau (13-17 ns). The average lifetimes shorten as a function of cyanide concentration since the fractional intensity shifts from an initial dominant long …

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Rnaml: A Standard Syntax For Exchanging Rna Information, Neocles B. Leontis, Allison Waugh, Patrick Gendron, Russ Altman, James W. Brown, David Case, Daniel Gautheret, Stephen C. Harvey, John Westbrook, Eric Westhof, Michael Zuker, François Major May 2002

Rnaml: A Standard Syntax For Exchanging Rna Information, Neocles B. Leontis, Allison Waugh, Patrick Gendron, Russ Altman, James W. Brown, David Case, Daniel Gautheret, Stephen C. Harvey, John Westbrook, Eric Westhof, Michael Zuker, François Major

Chemistry Faculty Publications

Analyzing a single data set using multiple RNA informatics programs often requires a file format conversion between each pair of programs, significantly hampering productivity. To facilitate the interoperation of these programs, we propose a syntax to exchange basic RNA molecular information. This RNAML syntax allows for the storage and the exchange of information about RNA sequence and secondary and tertiary structures. The syntax permits the description of higher level information about the data including, but not restricted to, base pairs, base triples, and pseudoknots. A class-oriented approach allows us to represent data common to a given set of RNA molecules, …

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Chemical Imaging Comes Of Age, John F. Turner Ii May 2002

Chemical Imaging Comes Of Age, John F. Turner Ii

Chemistry Faculty Publications

Sophisticated analysis techniques allow researchers to extract meaningful results from spectral imaging data.

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Magnetization Reversal Of Elliptical Co/Cu/Co Pseudo-Spin Valve Dots, Scott Whittenburg May 2002

Magnetization Reversal Of Elliptical Co/Cu/Co Pseudo-Spin Valve Dots, Scott Whittenburg

Chemistry Faculty Publications

We present our recent simulated results on Cr (5 nm)/ Cu (5 nm)/ Co (5 nm)/ Cu (3 nm)/ Co (2 nm) pseudo-spin valve dots. The simulated results agree qualitatively with the experimental results. Three different sizes of elliptical dots, 150 nm3105 nm, 175 nm370 nm, and 200 nm360 nm, were simulated. Our simulations show that in these types of dots magnetization reversal occurs by the formation of domain walls: 90° for 175 nm370 nm and 360° for 200 nm360 nm. No domain wall was observed in the reversal of the 150 nm3105 nm dots. For such dots, the simulated …

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Molecular Dynamics Simulations Of Phase Transition In Agno3, Jianjun Liu, Chun-Gang Duan, M. M. Ossowski, Wai-Ning Mei, Robert W. Smith, J. R. Hardy Mar 2002

Molecular Dynamics Simulations Of Phase Transition In Agno3, Jianjun Liu, Chun-Gang Duan, M. M. Ossowski, Wai-Ning Mei, Robert W. Smith, J. R. Hardy

Chemistry Faculty Publications

Structural phase transition in AgNO3 at high temperature is simulated by molecular dynamics. The simulations are based on the potentials calculated from the Gordon–Kim modified electron-gas formalism extended to molecular ionic crystals. AgNO3 transforms into rhombohedral structure at high temperature and the phase transition is associated with the rotations of the NO3 ions and displacements of the NO3 and Ag ions.

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The Influence Of Gold Substrate Topography On The Voltammetry Of Cytochrome C Adsorbed On Carboxylic Acid Terminated Self-Assembled Monolayers, Michael C. Leopold, Edmond F. Bowden Feb 2002

The Influence Of Gold Substrate Topography On The Voltammetry Of Cytochrome C Adsorbed On Carboxylic Acid Terminated Self-Assembled Monolayers, Michael C. Leopold, Edmond F. Bowden

Chemistry Faculty Publications

Interfacial investigations of a protein monolayer electrochemical system, equine cytochrome c (cyt c) adsorbed to carboxylic acid terminated self-assembled monolayer (COOH SAM) modified gold electrodes, were performed. Electrochemical, spectroscopic, and scanning probe microscopy techniques were utilized to explore the influence of gold topography in the cyt c/COOH SAM/gold system. COOH SAMs were prepared from 14-mercaptotetradecanoic acid and 11-mercaptoundecanoic acid on a variety of substrates including evaporated, bulk, single crystal, and epitaxially grown gold on mica. These substrates encompassed a wide range of surface roughness. As the topography of the gold became smoother, SAMs exhibited an increased ability to …

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Photoelectron Spectroscopy Of Clh2 - And Cld2 -: A Probe Of The Cl+H2 Van Der Waals Well And Spin-Orbit Excited States, Michael J. Ferguson, Giovanni Meloni, Harry Gomez, D M. Neumark Jan 2002

Photoelectron Spectroscopy Of Clh2 - And Cld2 -: A Probe Of The Cl+H2 Van Der Waals Well And Spin-Orbit Excited States, Michael J. Ferguson, Giovanni Meloni, Harry Gomez, D M. Neumark

Chemistry Faculty Publications

Photoelectron (PE) spectra of ClH−2 and ClD−2 were measured at 299 nm (4.154 eV). Photodetachment of these anions accesses the prereactive van der Waals well on the ground stateCl+H2potential energy surface, as well as the low-lying spin–orbit excited states resulting from the interaction of Cl and Cl* with H2. The PE spectra are dominated by two relatively narrow peaks corresponding to transitions to the neutral Cl⋅H2 and Cl*⋅H2 complexes. The energetics and widths of these features are interpreted in terms of the properties of the anion and neutral potential energy surfaces.

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