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A Carboxylate Oxygen of the Substrate Bridges the Magnesium Ions at the Active Site of Enolase: Structure of the Yeast Enzyme Complexed with the Equilibrium Mixture of 2-Phosphoglycerate and Phosphoenolpyruvate at 1.8 Å Resolution,

Todd M. Larsen、Joseph E. Wedekind、Ivan Rayment 等 4 位作者1996-01-01Biochemistry

The equilibrium mixture of yeast enolase with substrate, 2-phospho-D-glycerate (2-PGA), and product, phosphoenolpyruvate (P-enolpyruvate), has been crystallized from solutions of poly(ethylene glycol) (PEG) at pH 8.0. Crystals belong to the space group C2 and have unit cell dimensions a = 121.9 A, b = 73.2 A, c = 93.9…

Enzyme Structure and FunctionMetal-Catalyzed Oxygenation MechanismsS100 Proteins and Annexins

Deactivation of Methylrhenium Trioxide−Peroxide Catalysts by Diverse and Competing Pathways

Mahdi M. Abu‐Omar、Peter J. Hansen、James H. Espenson1996-01-01Journal of the American Chemical Society

The peroxides from methylrhenium trioxide (MTO) and hydrogen peroxide, CH 3 ReO 2 (η 2 -O 2 ), A, and CH 3 Re(O)(η 2 -O 2 ) 2 (H 2 O), B, have been fully characterized in both organic and aqueous media by spectroscopic means (NMR and UV−vis). In aqueous solution, the equilibrium constants for their formation are K 1 =…

Polyoxometalates: Synthesis and ApplicationsChemical Synthesis and ReactionsOxidative Organic Chemistry Reactions

Separation of 2(3),9(10),16(17),23(24)-Tetrasubstituted Phthalocyanines with Newly Developed HPLC Phases

Michael Sommerauer、Christine Rager、Michael Hanack1996-01-01Journal of the American Chemical Society

The synthesis of 2(3),9(10),16(17),23(24)-tetrasubstituted phthalocyanines from 1,2-dicyano-4-alkoxybenzenes or the corresponding isoindolines is reported. In each case, four isomers with D 2 h, C 4 h, C 2 v, and C s symmetry are obtained in the statistical expected yield. The separation of the C 4 h and the D 2 h iso…

Porphyrin and Phthalocyanine ChemistryPhotodynamic Therapy Research StudiesOxidative Organic Chemistry Reactions

Enzymatic Synthesis of Fluorescent Naphthol-Based Polymers

R.S. Premachandran、Soumitro Banerjee、X.-K. Wu 等 8 位作者1996-01-01Macromolecules

A fluorescent polymer of 2-naphthol is prepared using the oxidative enzyme horseradish peroxidase encapsulated in the microstructured system of AOT/isooctane reversed micelles. The monomer, being amphiphilic, partitions to the oil−water interface with the hydroxyl moieties directed toward the microaqueous core. The en…

Conducting polymers and applicationsLuminescence and Fluorescent MaterialsAnalytical Chemistry and Sensors

Crystal Structure of the Trigonal Modification (α Form) of Syndiotactic Polystyrene

Claudio De Rosa1996-01-01Macromolecules

A model of packing for the ordered modification of the α form of syndiotactic polystyrene is suggested, through comparisons between calculated structure factors and experimental intensities observed in the X-ray fiber and electron diffraction patterns. The present analysis improves the preliminary model proposed in pr…

Polymer crystallization and propertiesPolymer Nanocomposites and Propertiesbiodegradable polymer synthesis and properties

Surface Modification via Chain End Segregation in Polymer Blends

Thomas Schaub、G. J. Kellogg、Anne M. Mayes 等 6 位作者1996-01-01Macromolecules

We have explored the use of chain end segregation as a means of controlling the properties of a polymer surface. Thin film blends of homopolystyrene (PS) and PS synthesized with low-energy oligotetrafluoroethylene chain ends (PS-TFE) were studied using neutron reflectivity. The fraction of PS-TFE that localizes near t…

Surface Modification and SuperhydrophobicityAdhesion, Friction, and Surface InteractionsSurface Roughness and Optical Measurements

Tetranuclear and Octanuclear Manganese Carboxylate Clusters: Preparation and Reactivity of (NBun4)[Mn4O2(O2CPh)9(H2O)] and Synthesis of (NBun4)2[Mn8O4(O2CPh)12(Et2mal)2(H2O)2] with a “Linked-Butterfly” Structure

Michael W. Wemple、Hui-Lien Tsai、Sheyi Wang 等 8 位作者1996-01-01Inorganic Chemistry

The reaction of Mn(O(2)CPh)(2).2H(2)O and PhCO(2)H in EtOH/MeCN with NBu(n)(4)MnO(4) gives (NBu(n)(4))[Mn(4)O(2)(O(2)CPh)(9)(H(2)O)] (4) in high yield (85-95%). Complex 4 crystallizes in monoclinic space group P2(1)/c with the following unit cell parameters at -129 degrees C: a = 17.394(3) Å, b = 19.040(3) Å, c = 25.6…

Metal-Organic Frameworks: Synthesis and ApplicationsMagnetism in coordination complexesLanthanide and Transition Metal Complexes

Crystal Structures of the Oxidized and Reduced Forms of UDP-galactose 4-Epimerase Isolated from Escherichia coli,

James B. Thoden、Perry A. Frey、Hazel M. Holden1996-01-01Biochemistry

UDP-galactose 4-epimerase catalyzes the conversion of UDP-galactose to UDP-glucose through a mechanism involving the transient reduction of NAD+. Here we describe the X-ray structures for epimerase complexed with NADH/UDP, and NAD+/UDP, refined to 1.8 and 2.0 angstrom, respectively. The alpha-carbon positions for the…

Protein Structure and DynamicsEnzyme Structure and FunctionDiet, Metabolism, and Disease

Space-charge electrets

R. Kressmann、G. M. Sessler、P. Günther1996-01-01IEEE Transactions on Dielectrics and Electrical Insulation

A literature review on space-charge electrets, covering the time period 1987 to 1996, is presented. The review starts out with a discussion of new inorganic and organic electret materials which also includes silicon based single and double layers. This is followed by a review of recent work on methods for measuring ch…

Semiconductor materials and devicesHigh voltage insulation and dielectric phenomenaPower Transformer Diagnostics and Insulation

Comb-Branched Polymers: Monte Carlo Simulation and Scaling

Yannick Rouault、Oleg V. Borisov1996-01-01Macromolecules

The Monte Carlo simulation technique (the bond fluctuation model) has been used for the study of the equilibrium conformations of comb-branched polymers consisting of a long flexible main chain and side chains grafted at a regular separation onto the main chain. The solvent has been supposed to be good (athermal) for…

Surface Modification and SuperhydrophobicityAdvanced Polymer Synthesis and CharacterizationPolymer Surface Interaction Studies

An ab Initio Hartree−Fock Study of the Cubic and Tetragonal Phases of Bulk Tungsten Trioxide

Furio Corà、A. B. Patel、N. M. Harrison 等 5 位作者1996-01-01Journal of the American Chemical Society

The structural and electronic properties of bulk cubic and tetragonal tungsten trioxide are investigated using a periodic boundary condition ab initio Hartree−Fock method; a posteriori density functional corrections are used to estimate the effect of electron correlation on the energy. The forces involved in the bondi…

Transition Metal Oxide NanomaterialsHeusler alloys: electronic and magnetic propertiesThermal Expansion and Ionic Conductivity

Conformational Flexibility in Dodecasubstituted Porphyrins

Daniel J. Nurco、Craig J. Medforth、Timothy P. Forsyth 等 5 位作者1996-01-01Journal of the American Chemical Society

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTConformational Flexibility in Dodecasubstituted PorphyrinsDaniel J. Nurco, Craig J. Medforth, Timothy P. Forsyth, Marilyn M. Olmstead, and Kevin M. SmithView Author Information Department of Chemistry University of California Davis, California 95616-5295 Cite this: J.…

Porphyrin and Phthalocyanine ChemistrySurface Chemistry and CatalysisPorphyrin Metabolism and Disorders

[Co(en)3]CoSb4S8: A Novel Non-Centrosymmetric Lamellar Heterometallic Sulfide with Large-Framework Holes

H. Stephan、Mercouri G. Kanatzidis1996-01-01Journal of the American Chemical Society

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXT[Co(en)3]CoSb4S8: A Novel Non-Centrosymmetric Lamellar Heterometallic Sulfide with Large-Framework HolesHans-Oscar Stephan and Mercouri G. KanatzidisView Author Information Department of Chemistry and Center of Fundamental Materials Research, Michigan State University…

Quantum Dots Synthesis And PropertiesChalcogenide Semiconductor Thin FilmsCrystal Structures and Properties

Synthesis of Hybrid Organo−Mineral Materials: Anionic Tetraphenylporphyrins in Layered Double Hydroxides

S. Bonnet、Claude Forano、Avijit Roy 等 6 位作者1996-01-01Chemistry of Materials

meso -Tetrakis( p -carboxyphenyl)porphyrin ( p TCPP), the atropoisomer (αααα) of meso -tetrakis( o -carboxyphenyl)porphyrin ( o TCPP), and the ammonium salt of the meso -tetrakis( p -sulfonatophenyl)porphyrin (noted p TSPP) were intercalated into [Zn−Al] layered double hydroxide (LDH) using different preparative metho…

Metal-Organic Frameworks: Synthesis and ApplicationsPorphyrin and Phthalocyanine ChemistryCovalent Organic Framework Applications

Control of the Size and Composition of Three Dimensionally Diluted Magnetic Semiconductor Clusters

Laurent Lévy、Jean‐François Hochepied、M. P. Piléni1996-01-01The Journal of Physical Chemistry

Syntheses of diluted magnetic semiconductor Cd 1- y Mn y S nanoparticles varying in size from 1.9 to 3.5 nm and composition, y, from 0 to 0.3 have been performed in reverse micelles. Size and composition, y, of the particles are controlled independently. The particles are characterized by TEM, EDS, and EPR. Manganese…

Semiconductor Quantum Structures and DevicesQuantum Dots Synthesis And PropertiesChalcogenide Semiconductor Thin Films

Particle wettability and line tension

Robert Aveyard、John H. Clint1996-01-01Journal of the Chemical Society Faraday Transactions

For a spherical solid particle with a uniform surface at rest in a fluid/fluid interface, it is shown that if the line tension associated with the three-phase contact line around the particle is increased (conceptually), the contact angle between the particle and interface does not change continuously to 0 or 180°. Ra…

Material Dynamics and PropertiesSurfactants and Colloidal SystemsPickering emulsions and particle stabilization

Complexation of Proteins with a Strong Polyanion in an Aqueous Salt-free System

Atsushi Tsuboi、Tsuyoshi Izumi、Mitsuo Hirata 等 6 位作者1996-01-01Langmuir

We studied the formation in a salt-free solution of complexes between potassium poly(vinyl alcohol) sulfate (KPVS), a strong polyelectrolyte, and proteins with known amino-acid sequences: papain, human serum albumin, lysozyme, ribonuclease, trypsin, and pepsin. Turbidimetric titration, together with quasi-elastic ligh…

Lipid Membrane Structure and BehaviorMicrofluidic and Capillary Electrophoresis ApplicationsPolymer Surface Interaction Studies

Miscible Blends of Two Crystalline Polymers. 2. Crystallization Kinetics and Morphology in Blends of Poly(vinylidene fluoride) and Poly(1,4-butylene adipate)

Jan Penning、R. St. John Manley1996-01-01Macromolecules

The crystallization kinetics and morphology in miscible blends of poly(vinylidene fluoride) (PVF 2 ) and poly(1,4-butylene adipate) (PBA) have been investigated using optical microscopy and differential scanning calorimetry. Blends of PVF 2 and PBA are unique in the sense that both components are capable of crystalliz…

Polymer crystallization and propertiesPolymer Nanocomposites and Propertiesbiodegradable polymer synthesis and properties

Analysis of the Thermochemistry of NOx Decomposition over CuZSM-5 Based on Quantum Chemical and Statistical Mechanical Calculations

Bernhardt L. Trout、Arup K. Chakraborty、Alexis T. Bell1996-01-01The Journal of Physical Chemistry

CuZSM-5 is the most active catalyst known for the direct decomposition of NO x . We have performed first-principles quantum mechanical calculations to evaluate the electronic and structural properties of species adsorbed to Cu sites that might be involved in NO x decomposition. Using statistical mechanics, we have cal…

Catalytic Processes in Materials ScienceGas Sensing Nanomaterials and SensorsCatalysis and Oxidation Reactions

Photochromism of Spirooxazine-Doped Gels

John Biteau、Fréderic Chaput、Jean‐Pierre Boilot1996-01-01The Journal of Physical Chemistry

Spirooxazine photochromic dyes were trapped in gel thin films. Organically modified doped gels showed normal photochromism. The kinetics of the photochromism in these gels was quantified using both Gaussian and simple biexponential models in order to take into account the inhomogeneous distribution of free volume in t…

Surfactants and Colloidal SystemsPhotochemistry and Electron Transfer StudiesPhotochromic and Fluorescence Chemistry