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Articles 631 - 660 of 962

Full-Text Articles in Chemistry

Supporting Information For "The Molecular Basis Of High-Altitude Adaptation In Deer Mice", Jay F. Storz, Stephen J. Sabatino, Federico G. Hoffmann, Eben J. Gering, Hideaki Moriyama, Nuno Ferrand, Bruno Monteiro, Michael W. Nachman Mar 2007

Supporting Information For "The Molecular Basis Of High-Altitude Adaptation In Deer Mice", Jay F. Storz, Stephen J. Sabatino, Federico G. Hoffmann, Eben J. Gering, Hideaki Moriyama, Nuno Ferrand, Bruno Monteiro, Michael W. Nachman

Hideaki Moriyama Publications

Figure S1: Variation in Site-Specific Levels of Altitudinal Differentiation across the 5′ α- Globin Gene of P. maniculatus

Figure S2: Relationship between Pairwise Linkage Disequilibrium and Distance in bp

Genbank Accession Numbers

Table S1: Amino Acid Variation in the α-Globin Genes of High- and Low-Altitude Deer Mice: Amino acid replacement polymorphisms in deer mice where the derived variant is present at a frequency of >0.100 in the high-altitude sample.

Table S2: Additional Information on Sequenced Loci: Primer sequences for nuclear loci in P. maniculatus.

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The Molecular Basis Of High-Altitude Adaptation In Deer Mice, Jay F. Storz, Stephen J. Sabatino, Federico G. Hoffmann, Eben J. Gering, Hideaki Moriyama, Nuno Ferrand, Bruno Monteiro, Michael W. Nachman Mar 2007

The Molecular Basis Of High-Altitude Adaptation In Deer Mice, Jay F. Storz, Stephen J. Sabatino, Federico G. Hoffmann, Eben J. Gering, Hideaki Moriyama, Nuno Ferrand, Bruno Monteiro, Michael W. Nachman

Hideaki Moriyama Publications

Elucidating genetic mechanisms of adaptation is a goal of central importance in evolutionary biology, yet few empirical studies have succeeded in documenting causal links between molecular variation and organismal fitness in natural populations. Here we report a population genetic analysis of a two-locus a-globin polymorphism that underlies physiological adaptation to high-altitude hypoxia in natural populations of deer mice, Peromyscus maniculatus. This system provides a rare opportunity to examine the molecular underpinnings of fitness-related variation in protein function that can be related to a well-defined selection pressure. We surveyed DNA sequence variation in the duplicated α -globin genes of P. maniculatus …

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Surface Properties Of Licoo2, Linio2 And Lini1-XCoXO2, Anthony W. Moses, Harry G. Garcia Flores, Jong-Gyu Kim, Marjorie Langell Mar 2007

Surface Properties Of Licoo2, Linio2 And Lini1-XCoXO2, Anthony W. Moses, Harry G. Garcia Flores, Jong-Gyu Kim, Marjorie Langell

Marjorie A. Langell Publications

The surface composition and chemical environment of LiCoO2, hexagonal LiNiO2, cubic LiNiO2, and the mixed transition metal oxide LiNi0.5Co0.5O2 have been determined by Auger electron and X-ray photoelectron spectroscopies. While the LiCoO2 surface properties can easily be extrapolated from bulk composition, the nickel-containing materials are less straightforward. Their surface concentration tends to be depleted in lithium relative to that of the bulk and shows an atypical chemical environment for the constituent elements. The Ni 2p XPS photoemission suggests a near “ NiO-like” selvedge through the XPS binding energies …

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Quantized Magnetoresistance In Atomic-Size Contacts, Andrei Sokolov, Chunjuan Zhang, Evgeny Y. Tsymbal, Jody G. Redepenning, Bernard Doudin Feb 2007

Quantized Magnetoresistance In Atomic-Size Contacts, Andrei Sokolov, Chunjuan Zhang, Evgeny Y. Tsymbal, Jody G. Redepenning, Bernard Doudin

Jody Redepenning Publications

When the dimensions of a metallic conductor are reduced so that they become comparable to the de Broglie wavelengths of the conduction electrons, the absence of scattering results in ballistic electron transport and the conductance becomes quantized. In ferromagnetic metals, the spin angular momentum of the electrons results in spin-dependent conductance quantization and various unusual magnetoresistive phenomena. Theorists have predicted a related phenomenon known as ballistic anisotropic magnetoresistance (BAMR). Here we report the first experimental evidence for BAMR by observing a stepwise variation in the ballistic conductance of cobalt nanocontacts as the direction of an applied magnetic field is varied. …

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Effect Of Surrounding Point Charges On The Density Functional Calculations Of NiXOX Clusters (X = 4–12), Evgueni B. Kadossov, Karen J. Gaskell, Marjorie Langell Feb 2007

Effect Of Surrounding Point Charges On The Density Functional Calculations Of NiXOX Clusters (X = 4–12), Evgueni B. Kadossov, Karen J. Gaskell, Marjorie Langell

Marjorie A. Langell Publications

Embedded NixOx clusters (x = 4–12) have been studied by the density-functional method using compensating point charges of variable magnitude to calculate the ionic charge, bulk modulus, and lattice binding energy. The computations were found to be strongly dependent on the value of the surrounding point charge array and an optimum value could be found by choosing the point charge to reproduce the experimentally observed Ni–O lattice parameter. This simple, empirical method yields a good match between computed and experimental data, and even small variation from the optimum point charge value produces significant deviation between computed …

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Examination Of The New Α-(2′Z-Fluoro)Vinyl Trigger With Lysine Decarboxylase: The Absolute Stereochemistry Dictates The Reaction Course, Kannan R. Karukurichi, Roberto De La Salud-Bea, Wan Jin Jahng, David B. Berkowitz Jan 2007

Examination Of The New Α-(2′Z-Fluoro)Vinyl Trigger With Lysine Decarboxylase: The Absolute Stereochemistry Dictates The Reaction Course, Kannan R. Karukurichi, Roberto De La Salud-Bea, Wan Jin Jahng, David B. Berkowitz

David Berkowitz Publications

The first examination of a terminal α-fluorovinyl trigger in an amino acid decarboxylase active site is reported. To investigate the enantiospecifity of inactivation with this new AADC trigger, an enantioselective synthesis of L-α-(2′Z-fluoro)vinyllysine and its D-antipode has been developed. Control of stereochemistry is achieved through introduction of the amino acid side chain via alkylation of a chiral vinylglycine-derived dienolate. Facial selectivity is conferred by a trans-2′(β- naphthyl)-2′-propylcyclohexyl ester auxiliary, available in both antipodal forms (Comins protocol). The alkylation employs a new electrophile, N-p-methoxybenzyl-N-(2′- trimethylsilylethanesulfonyl)-4-iodobutylamine, for convergent installation of the lysine side chain. Vinyl to 2′-fluorovinyl interconversion then provides L- …

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Searching For Smart Durable Coatings To Promote Bone Marrow Stromal Cell Growth While Preventing Biofilm Formation, Fereydoon Namavar, John D. Jackson, J. Graham Sharp, Ethan E. Mann, Kenneth W. Bayles, Chin Li Cheung, Connie A. Feschuk, Shailaja Varma, Hani Haider, Kevin L. Garvin Jan 2007

Searching For Smart Durable Coatings To Promote Bone Marrow Stromal Cell Growth While Preventing Biofilm Formation, Fereydoon Namavar, John D. Jackson, J. Graham Sharp, Ethan E. Mann, Kenneth W. Bayles, Chin Li Cheung, Connie A. Feschuk, Shailaja Varma, Hani Haider, Kevin L. Garvin

Barry Chin Li Cheung Publications

There is a great need to develop methods to regulate cellular growth in order to enhance or prevent cell proliferation, as needed, to either improve health or prevent disease. In this work we evaluated the adhesion, survival and growth of bone marrow stromal cells on the surface of several new ion beam engineered nano-crystals of ceramic hard coatings such as zirconium, titanium, tantalum and cerium oxides. Cell adhesion and growth on the ceramic coatings were compared to adhesion and growth on a nano-crystalline silver coating which is known to possess antibacterial properties. The initial results of a study to determine …

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Apparatus And Method For Growing Crystal, And Apparatus And Method For Analyzing Crystal: United States Patent No. 7,156,917 B2, Hideaki Moriyama, Norio Sugi, Kazunori Kawasaki, Shoji Muramatsu Jan 2007

Apparatus And Method For Growing Crystal, And Apparatus And Method For Analyzing Crystal: United States Patent No. 7,156,917 B2, Hideaki Moriyama, Norio Sugi, Kazunori Kawasaki, Shoji Muramatsu

Hideaki Moriyama Publications

An apparatus for growing a biological macromolecular crystal by vaporizing biological macromolecular solution into an oversaturated state. The apparatus includes a first sealed room that receives first crystallizing agent solution, and a communicating tube that communicates with the first sealed room and has a small sectional area for suppressing convection of air. A plurality of droplets of solution dissolving a biological macromolecule and a crystallizing agent therein are held in the communicating tube with the plurality of droplets being separated from each other.

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Structure And Biosynthesis Of Heat-Stable Antifungal Factor (Hsaf), A Broad-Spectrum Antimycotic With A Novel Mode Of Action, Fengan Yu, Kathia Zaleta-River, Xiangcheng Zhu, Justin Huffman, Jeffrey C. Millet, Steven D. Harris, Gary Y. Yuen, Xing-Cong Li, Liangcheng Du Jan 2007

Structure And Biosynthesis Of Heat-Stable Antifungal Factor (Hsaf), A Broad-Spectrum Antimycotic With A Novel Mode Of Action, Fengan Yu, Kathia Zaleta-River, Xiangcheng Zhu, Justin Huffman, Jeffrey C. Millet, Steven D. Harris, Gary Y. Yuen, Xing-Cong Li, Liangcheng Du

Department of Chemistry: Faculty Publications

A screen for antifungal compounds from Lysobacter enzymogenes strain C3, a bacterial biological control agent of fungal diseases, has previously led to the isolation of heat-stable antifungal factor (HSAF). HSAF exhibits inhibitory activities against a wide range of fungal species and shows a novel mode of antifungal action by disrupting the biosynthesis of a distinct group of sphingolipids. We have now determined the chemical structure of HSAF, which is identical to that of dihydromaltophilin, an antifungal metabolite with a unique macrocyclic lactam system containing a tetramic acid moiety and a 5,5,6-tricyclic skeleton. We have also identified the genetic locus responsible …

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Corrosion Studies On The Uss Arizona With Application To A Japanese Midget Submarine, Brent M. Wilson, Donald L. Johnson, Hans Vantilburg, Matthew A. Russell, Larry E. Murphy, James D. Carr, Robert J. De Angelis, David L. Conlin Jan 2007

Corrosion Studies On The Uss Arizona With Application To A Japanese Midget Submarine, Brent M. Wilson, Donald L. Johnson, Hans Vantilburg, Matthew A. Russell, Larry E. Murphy, James D. Carr, Robert J. De Angelis, David L. Conlin

Department of Chemistry: Faculty Publications

The assessment of corrosion on the USS Arizona included the pioneering development of a minimum-impact cost-effective technique to determine the corrosion rate of steel-hulled shipwrecks in seawater. The technique, with potential application worldwide, is illustrated in this paper with the application to a World War II Japanese midget submarine submerged in deep waters off the Oahu, Hawaii, coast.

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Multiwalled Ice Helixes And Ice Nanotubes, Jaeil Bai, Jun Wang, Xiao Cheng Zeng Nov 2006

Multiwalled Ice Helixes And Ice Nanotubes, Jaeil Bai, Jun Wang, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

We report six phases of high-density nano-ice predicted to form within carbon nanotubes (CNTs) at high pressure. High-density nano-ice self-assembled within smaller-diameter CNT (17,0) exhibits a double-walled helical structure where the outer wall consists of four double- stranded helixes, which resemble a DNA double helix, and the inner wall is a quadruple-stranded helix. Four other double-walled nano-ices, self-assembled respectively in two larger-diameter CNTs (20,0 and 22,0), display tubular structure. Within CNT (24,0), the confined water can freeze spontaneously into a triple-walled helical nanoice where the outer wall is an 18-stranded helix and the middle and inner walls are hextuple-stranded helixes.

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Α,Ω-Dithiol Oligo(Phenylene Vinylene)S For The Preparation Of High-Quality Π-Conjugated Self-Assembled Monolayers And Nanoparticle-Functionalized Electrodes, Dwight S. Seferos, Rebecca Lai, Kevin W. Plaxco, Guillermo C. Bazan Nov 2006

Α,Ω-Dithiol Oligo(Phenylene Vinylene)S For The Preparation Of High-Quality Π-Conjugated Self-Assembled Monolayers And Nanoparticle-Functionalized Electrodes, Dwight S. Seferos, Rebecca Lai, Kevin W. Plaxco, Guillermo C. Bazan

Rebecca Lai Publications

While thioacetate-terminated oligo(phenylene vinylene)s (OPVs) have been synthesized and employed in applications involving the formation of metal–molecule–metal junctions, the synthesis and application of potentially more versatile α,ω-dithiol OPVs have not previously been described. Here, a thiomethyl-precursor route to the synthesis of α,ω-dithiol OPVs is reported and their ability to form well-ordered self-assembled monolayers (SAMs) without the addition of exogenous deprotection reagents is described. α,ω-Dithiol OPV monolayers exhibit thicknesses consistent with molecular length and are nearly defect-free, as assayed by electrochemical measurements. To demonstrate the ease with which SAMs containing these bifunctional OPVs can, in contrast to thioacetate functionalized OPVs, be …

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Acrosome Reaction Is Subfamily Specific In Sea Star Fertilization, Mia Nakachi, Hideaki Moriyama, Motonori Hoshi, Midori Matsumoto Oct 2006

Acrosome Reaction Is Subfamily Specific In Sea Star Fertilization, Mia Nakachi, Hideaki Moriyama, Motonori Hoshi, Midori Matsumoto

Hideaki Moriyama Publications

In the fertilization process of sea stars, sperm is activated to go through the acrosome reaction before cell fusion. We focused on induction of the acrosome reaction as a key process in fertilization. Six species of sea stars were used in this study: Asterias amurensis, Asterias rubens, Asterias forbesi, Aphelasterias japonica, Distolasterias nipon, and Asterina pectinifera. Acrosome reaction assays indicate that the acrosome reaction can be induced across species within Asteriinae subfamily. However, cross-fertilization assays indicate that sea stars have species specificity in fertilization. Therefore, steps after the acrosome reaction are responsible for the …

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Structures And Relative Stability Of Neutral Gold Clusters: AuN (N=15–19), Satya S. Bulusu, Xiao Cheng Zeng Oct 2006

Structures And Relative Stability Of Neutral Gold Clusters: AuN (N=15–19), Satya S. Bulusu, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

We performed a global-minimum search for low-lying neutral clusters (Aun) in the size range of n=15–19 by means of basin-hopping method coupled with density functional theory calculation. Leading candidates for the lowest-energy clusters are identified, including four for Au15, two for Au16, three for Au17, five for Au18, and one for Au19. For Au15 and Au16 we find that the shell-like flat-cage structures dominate the population of low-lying clusters, while for Au17 and Au18 spherical-like hollow-cage structures dominate the low-lying population. The transition …

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Homogeneous Nucleation At High Supersaturation And Heterogeneous Nucleation On Microscopic Wettable Particles: A Hybrid Thermodynamic/Density-Functional Theory, T. V. Bykov, Xiao Cheng Zeng Oct 2006

Homogeneous Nucleation At High Supersaturation And Heterogeneous Nucleation On Microscopic Wettable Particles: A Hybrid Thermodynamic/Density-Functional Theory, T. V. Bykov, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Homogeneous nucleation at high supersaturation of vapor and heterogeneous nucleation on microscopic wettable particles are studied on the basis of Lennard-Jones model system. A hybrid classical thermodynamics and density-functional theory (DFT) approach is undertaken to treat the nucleation problems. Local-density approximation and weighted-density approximation are employed within the framework of DFT. Special attention is given to the disjoining pressure of small liquid droplets, which is dependent on the thickness of wetting film and radius of the wettable particle. Different contributions to the disjoining pressure are examined using both analytical estimations and numerical DFT calculation. It is shown that van der …

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Novel Mesoscale Defect Structure On Nio(1 0 0) Surfaces By Atomic Force Microscopy, S. C. Petitto, Cindy L. Berrie, Marjorie Langell Sep 2006

Novel Mesoscale Defect Structure On Nio(1 0 0) Surfaces By Atomic Force Microscopy, S. C. Petitto, Cindy L. Berrie, Marjorie Langell

Marjorie A. Langell Publications

Cleaved NiO(1 0 0) surfaces were imaged with atomic force microscopy (AFM) to determine defect concentrations and morphology. Random (0 1 0) and (0 0 1) oriented steps, which have been previously characterized, were the most common defect observed on the cleaved surface and formed with step heights in multiples of 2.1 Å, the Ni–O nearest-neighbor distance, and terrace widths in the range of 25–100 nm. In addition, the surface showed novel mesoscale (~0.5–2 μm) square pyramidal defects with the pyramid base oriented along (1 0 0) symmetry related directions. Upon etching, the pyramidal defects converted to more stable cubic …

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Tau-Tubulin Kinase 1 (Ttbk1), A Neuron-Specific Tau Kinase Candidate, Is Involved In Tau Phosphorylation And Aggregation, Shinji Sato, Ronald Cerny, James L. Buescher, Tsuneya Ikezu Sep 2006

Tau-Tubulin Kinase 1 (Ttbk1), A Neuron-Specific Tau Kinase Candidate, Is Involved In Tau Phosphorylation And Aggregation, Shinji Sato, Ronald Cerny, James L. Buescher, Tsuneya Ikezu

Ronald Cerny Publications

Neurofibrillary tangles, which are major pathological hallmarks of Alzheimer’s disease (AD), are composed of paired helical filaments (PHFs) containing hyperphosphorylated tau. Specific kinases regulate tau phosphorylation and are closely linked to the pathogenesis of AD. We have characterized a human tau-tubulin kinase 1 (TTBK1) gene located on chromosome 6p21.1. TTBK1 is a serine/threonine/tyrosine kinase that is conserved among species and belongs to the casein kinase 1 superfamily. It is specifically expressed in the brain, especially in the cytoplasm of cortical and hippocampal neurons. TTBK1 phosphorylates tau proteins in both a Mg2+- and a Mn2+-dependent manner. Phosphopeptide …

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Single-Crystal, Polarized, Raman Scattering Study Of The Molecular And Lattice Vibrations For The Energetic Material Cyclotrimethylene Trinitramine, James C. Haycraft, Lewis L. Stevens, Craig J. Eckhardt Sep 2006

Single-Crystal, Polarized, Raman Scattering Study Of The Molecular And Lattice Vibrations For The Energetic Material Cyclotrimethylene Trinitramine, James C. Haycraft, Lewis L. Stevens, Craig J. Eckhardt

Craig J. Eckhardt Publications

The single-crystal, polarized, Raman spectra for cyclotrimethylene trinitramine (RDX) have been studied at room temperature and pressure over the region of 5–3400 cm-1. While the observed Raman bands agree well with a previous Raman study, this work provides a consistent interpretation of the Raman spectra by assignment of fundamental modes, overtones, and combination bands. A total of 56 internal vibrations were observed, 36 of which were labeled as fundamental molecular vibrations. In addition, all 24 lattice optical phonons are identified. All six possible polarizations were probed to obtain the Ag, B1g, B2 …

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“Reductive Ozonolysis” Via A New Fragmentation Of Carbonyl Oxides, Chris Schwartz, Joseph Raible, Kyle Mott, Patrick Dussault Sep 2006

“Reductive Ozonolysis” Via A New Fragmentation Of Carbonyl Oxides, Chris Schwartz, Joseph Raible, Kyle Mott, Patrick Dussault

Patrick Dussault Publications

This account describes the development of methodologies for ‘reductive’ ozonolysis, the direct ozonolytic conversion of alkenes into carbonyl groups without the intermediacy of 1,2,4-trioxolanes (ozonides). Ozonolysis of alkenes in the presence of DMSO produces a mixture of aldehyde and ozonide. The combination of DMSO and Et3N results in improved yields of carbonyls but still leaves unacceptable levels of residual ozonides; similar results are obtained using secondary or tertiary amines in the absence of DMSO. The influence of amines is believed to result from conversion to the corresponding N-oxides; ozonolysis in the presence of amine N-oxides efficiently …

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List Of Publications: Robert Powers Aug 2006

List Of Publications: Robert Powers

Robert Powers Publications

Chronological list of 57 published articles and chapters in chemistry. Current through August 2006.

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Hybrid Atomistic-Coarse-Grained Treatment Of Multiscale Processes In Heterogeneous Materials: A Self-Consistent-Field Approach, Dennis J. Diestler, H. Zhou, Ruqiang Feng, Xiao Cheng Zeng Aug 2006

Hybrid Atomistic-Coarse-Grained Treatment Of Multiscale Processes In Heterogeneous Materials: A Self-Consistent-Field Approach, Dennis J. Diestler, H. Zhou, Ruqiang Feng, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

A treatment of multiscale quasistatic processes that combines an atomistic description of microscopic heterogeneous (“near”) regions of a material with a coarse-grained (quasicontinuum) description of macroscopic homogeneous (“far”) regions is presented. The hybrid description yields a reduced system consisting of the original atoms of the near regions plus pseudoatoms (nodes of the coarse-graining mesh) of the far regions, which interact through an effective many-body potential energy Veff that depends on the thermodynamic state. The approximate nature of Veff gives rise to “ghost forces,” which are reflected in spurious heterogeneities close to interfaces between near and far regions. The …

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Comparison Of Protein Active Site Structures For Functional Annotation Of Proteins And Drug Design, Robert Powers, Jennifer C. Copeland, Katherine Germer, Kelly A. Mercier, Viswanathan Ramanathan, Peter Revesz Jul 2006

Comparison Of Protein Active Site Structures For Functional Annotation Of Proteins And Drug Design, Robert Powers, Jennifer C. Copeland, Katherine Germer, Kelly A. Mercier, Viswanathan Ramanathan, Peter Revesz

Robert Powers Publications

Rapid and accurate functional assignment of novel proteins is increasing in importance, given the completion of numerous genome sequencing projects and the vastly expanding list of unannotated proteins. Traditionally, global primary-sequence and structure comparisons have been used to determine putative function. These approaches, however, do not emphasize similarities in active site configurations that are fundamental to a protein’s activity and highly conserved relative to the global and more variable structural features. The Comparison of Protein Active Site Structures (CPASS) database and software enable the comparison of experimentally identified ligand-binding sites to infer biological function and aid in drug discovery. The …

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Shape-Persistent Macrocyclic Aromatic Tetrasulfonamides: Molecules With Nanosized Cavities And Their Nanotubular Assemblies In Solid State, Lan He, Yu An, Lihua Yuan, Wen Feng, Minfeng Li, Dechun Zhang, Kazuhiro Yamato, Chong Zheng, Xiao Cheng Zeng, Bing Gong Jul 2006

Shape-Persistent Macrocyclic Aromatic Tetrasulfonamides: Molecules With Nanosized Cavities And Their Nanotubular Assemblies In Solid State, Lan He, Yu An, Lihua Yuan, Wen Feng, Minfeng Li, Dechun Zhang, Kazuhiro Yamato, Chong Zheng, Xiao Cheng Zeng, Bing Gong

Xiao Cheng Zeng Publications

Alkoxy side-chain-flanked diarylsulfonamide serves as a reliable structural motif for constructing macrocyclic aromatic tetrasulfonamides. This 90° structural motif is persistent both in solution and in the solid state, which allows the one-step formation of tetrasulfonamide macrocycles. These macrocycles adopt a cone-shaped conformation in solution and in the solid state. For each molecule, an interior cavity surrounded by the aromatic residues is formed. The cavity sizes of the macrocycles can be tuned by incorporating aromatic residues of proper sizes. Guest (solvent) molecules are found in the cavities and bound by side chains. In solution, 1H NMR shows that the cone …

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Structural And Electronic Properties Of Gd@C60: All-Electron Relativistic Total-Energy Study, Jing Lu, Wai-Ning Mei, Yi Gao, Xiao Cheng Zeng, Mingwei Jing, Guangping Li, Renat F. Sabirianov, Zhengxiang Gao, Liping You, Jun Xu, Dapeng Yu, Hengqiang Ye Jul 2006

Structural And Electronic Properties Of Gd@C60: All-Electron Relativistic Total-Energy Study, Jing Lu, Wai-Ning Mei, Yi Gao, Xiao Cheng Zeng, Mingwei Jing, Guangping Li, Renat F. Sabirianov, Zhengxiang Gao, Liping You, Jun Xu, Dapeng Yu, Hengqiang Ye

Xiao Cheng Zeng Publications

Water soluble Gd-based metallofullerenes have potential application as magnetic resonance imaging contrast agent due to its higher proton relaxivities and lower toxicity. In this letter, we have investigated the structural and electronic properties of Gd@ C60, which is the most abundantly produced Gd-based metallofullerene in carbon arc process, by using all-electron relativistic density functional theory. It is found that the Gd3+ ion is bonded to a hexagonal ring of C60 by electrostatic interaction. The total spin multiplicity of Gd@C60 is S = 7. The Gd atomic orbitals are hybridized with the C60 molecular orbitals.

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Adsorption Of Transition-Metal Atoms On Boron Nitride Nanotube: A Density-Functional Study, Xiaojun Wu, Xiao Cheng Zeng Jul 2006

Adsorption Of Transition-Metal Atoms On Boron Nitride Nanotube: A Density-Functional Study, Xiaojun Wu, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Adsorption of transition atoms on a (8,0) zigzag single-walled boron nitride (BN) nanotube has been investigated using density-functional theory methods. Main focuses have been placed on configurations corresponding to the located minima of the adsorbates, the corresponding binding energies, and the modified electronic properties of the BN nanotubes due to the adsorbates.We have systemically studied a series of metal adsorbates including all 3d transition-metal elements (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) and two group-VIIIA transition-metal elements (Pd and Pt). We found that many transition-metal atoms can be chemically adsorbed on the outer surface of the …

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Adsorption Of Hydrogen Molecules On The Platinum-Doped Boron Nitride Nanotubes, Xiaojun Wu, J.L. Yang, Xiao Cheng Zeng Jul 2006

Adsorption Of Hydrogen Molecules On The Platinum-Doped Boron Nitride Nanotubes, Xiaojun Wu, J.L. Yang, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Adsorption of hydrogen molecules on platinum-doped single-walled zigzag (8,0) boron nitride (BN) nanotube is investigated using the density-functional theory. The Pt atom tends to occupy the axial bridge site of the BN tube with the highest binding energy of −0.91 eV. Upon Pt doping, several occupied and unoccupied impurity states are induced, which reduces the band gap of the pristine BN nanotube. Upon hydrogen adsorption on Pt-doped BN nanotube, the first hydrogen molecule can be chemically adsorbed on the Pt-doped BN nanotube without crossing any energy barrier, whereas the second hydrogen molecule has to overcome a small energy barrier of …

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Staphylococcus Aureus Helicase But Not Escherichia Coli Helicase Stimulates S. Aureus Primase Activity And Maintains Initiation Specificity, Scott A. Koepsell, Marilynn A. Larson, Mark A. Griep, Steven H. Hinrichs Jul 2006

Staphylococcus Aureus Helicase But Not Escherichia Coli Helicase Stimulates S. Aureus Primase Activity And Maintains Initiation Specificity, Scott A. Koepsell, Marilynn A. Larson, Mark A. Griep, Steven H. Hinrichs

Mark A. Griep Publications

Bacterial primases are essential for DNA replication due to their role in polymerizing the formation of short RNA primers repeatedly on the lagging-strand template and at least once on the leading-strand template. The ability of recombinant Staphylococcus aureus DnaG primase to utilize different single-stranded DNA templates was tested using oligonucleotides of the sequence 5’-CAGA (CA) 5 XYZ (CA) 3-3’, where XYZ represented the variable trinucleotide. These experiments demonstrated that S. aureus primase synthesized RNA primers predominately on templates containing 5’-d(CTA)-3’ or TTA and to a much lesser degree on GTA-containing templates, in contrast to results seen with the Escherichia …

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The Importance Of The Strictly Conserved, C-Terminal Glycine Residue In Phosphoenolpyruvate Carboxylase For Overall Catalysis: Mutagenesis And Truncation Of Gly-961 In The Sorghum C4 Leaf Isoform, Wenxin Xu, Shaheen Ahmed, Hideaki Moriyama, Raymond Chollet Jun 2006

The Importance Of The Strictly Conserved, C-Terminal Glycine Residue In Phosphoenolpyruvate Carboxylase For Overall Catalysis: Mutagenesis And Truncation Of Gly-961 In The Sorghum C4 Leaf Isoform, Wenxin Xu, Shaheen Ahmed, Hideaki Moriyama, Raymond Chollet

Hideaki Moriyama Publications

Phosphoenolpyruvate carboxylase (PEPC) is a “multifaceted,” allosteric enzyme involved in C4 acid metabolism in green plants/microalgae and prokaryotes. Before the elucidation of the three-dimensional structures of maize C4 leaf and Escherichia coli PEPC, our truncation analysis of the sorghum C4 homologue revealed important roles for the enzyme’s C-terminal α-helix and its appended QNTG961 tetrapeptide in polypeptide stability and overall catalysis, respectively. Collectively, these functional and structural observations implicate the importance of the PEPC C-terminal tetrapeptide for both catalysis and negative allosteric regulation. We have now more finely dissected this element of PEPC structure-function by modification of the absolutely conserved …

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Chromatographic Analysis Of Carbamazepine Binding To Human Serum Albumin: Ii. Comparison Of The Schiff Base And N-Hydroxysuccinimide Immobilization Methods, Hee Seung Kim, Rangan Mallik, David S. Hage Jun 2006

Chromatographic Analysis Of Carbamazepine Binding To Human Serum Albumin: Ii. Comparison Of The Schiff Base And N-Hydroxysuccinimide Immobilization Methods, Hee Seung Kim, Rangan Mallik, David S. Hage

David Hage Publications

Recent studies with carbamazepine on human serum albumin (HSA) columns have noted an appreciable degree of non-specific binding on supports prepared by the Schiff base immobilization method. This work examines an alternative immobilization method for HSA based on N-hydroxysuccinimide (NHS)-activated silica. This support was prepared by reacting HPLC-grade silica directly with disuccinimidyl carbonate. The resulting material was compared to an HSA support prepared by the Schiff base method in terms of its activity for carbamazepine and non-specific interactions with this drug. When examined by frontal analysis, both supports gave comparable association equilibrium constants for carbamazepine interactions with HSA ((0.53–0.55) …

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Molecular Simulations Of Solid-Liquid Interfacial Tension Of Silicon, Yuk Wai Tang, Jun Wang, Xiao Cheng Zeng Jun 2006

Molecular Simulations Of Solid-Liquid Interfacial Tension Of Silicon, Yuk Wai Tang, Jun Wang, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

Silicon is an important semiconductor for manufacturing of microelectronic chips used in computers and other electronic devices. During the manufacturing process, liquid silicon is being solidified to make high-grade solid semiconductors. Thus, improved data of the solid-liquid interfacial properties of silicon will be useful towards optimizing the experiment condition for making better quality electronics. Yet it is difficult to perform experiments of liquid silicon due to its high melting point. Thus far, most experimental measurements of the solid-liquid interfacial tension are based on the measurement of rate of homogeneous crystal nucleation at a given undercooling. The first measurement of solidliquid …

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