Investigation on a Small Oscillogram

Oscillographic chronopotentiometry is a type of current-controlled electroanalytical technique founded by J.Heyrovsky in19411and developed by Hung Kao after19632-5.In this technique,a constant-amplitude of alternating current j=j0sin(ωt)as well as a less direct current,passed through the electrolytic cell and the change of potential of the polarizable electrode exhibited on the oscillograph directly as a function of time during a continuous potential scan from zero to–2V.Generally,quantita…     

Desorption Behaviour of HF,HCFC-133a and HFC-134a on a Catalyst Supported on γ-AlF3

The desorption behaviour (desorption temperature and extent of desorption) of HF,HCFC-133a (CF₃CH₂Cl) and HFC-134a (CF₃CH₂F) on γ-AlF₃ or catalyst supported on γ-AlF₃ was studied using an adsorption apparatus and TG, DTA and DSC methods. On the basis of the results a reaction mechanism was proposed for the preparation of HFC-134a. The γ-AlF₃ employed for preparing the catalyst was expected to be stable below 550°C based on the crystalline phase transition temperature of γ-AlF₃. This revised version was published online in August 2006 with corrections to the Cover Date.     

Comparative studies on a mesophilic and a thermophilic α-amylase

A comparative study was performed on thermal stability of mesophilic and thermophilic α-amylases, and the effects of various denaturing agents, organic solvents, and stabilizers were investigated. As expected, the thermophilic enzyme showed higher resistance toward denaturation in water as its natural medium, but such a difference could not be detected in nonaqueous environments. Furthermore, stability of these molecules was improved by including various stabilizing agents. Of the compounds tested, sorbitol provided the highest degree of protection, which was found to be owing to its effect on increasing T _m and its ability in totally preventing deamidation of amino acid residues in the protein molecules.     

Biophysical Studies on the Site-Selective Binding of a Synthesized Selenium–Quercetin Complex on a Protein

A selenium?Cquercetin complex (SEQC) was synthesized and its structure was identified by IR, LC-MS and ¹H-NMR. Its biochemical effects on bovine serum albumin (BSA) were studied by measuring its molecular spectra including three-dimensional fluorescence, ultraviolet and circular dichroism (CD) spectra. The interaction of SEQC and BSA is discussed in terns of fluorescence quenching and F?rster??s non-radiation energy transfer theory. The thermodynamic parameters $\Delta H^{\uptheta}$ , $\Delta G^{\uptheta}$ , and $\Delta S^{\uptheta}$ were calculated at different temperatures and the results indicate that the interaction is an endothermic as well as an entropy generating process. The binding site was explored by the fluorescence probe technique using warfarin and ibuprofen as markers. It was found that around body temperature hydrophobic forces maintained the average distance from the tryptophan residue in domain?II of BSA (donor) to SEQC (acceptor) at 3.76 nm. The conformational changes of BSA were investigated by three-dimensional fluorescence and circular dichroism spectra.     

Fluorescence Switch Based on a Porphyrin-perylene Dyad

Upon excitation of porphyrin or perylene subunit, the porphyrin-perylene dyad exhibits reversible fluorescence emitting and quenching by formation and neutralization of the protonated porphyrin subunit, thereby providing a prototype of molecular fluorescence switch working in an expanded spectral range.     

Voltammetry at a liquid–liquid interface supported on a metallic electrode

A liquid–liquid interface supported on a metallic electrode has been used to study ion transfer (IT) and electron transfer (ET) reactions by cyclic voltammetry. The system is composed of an aqueous droplet supported on a platinum disc electrode and immersed into an organic electrolyte solution. Depending on the nature of the dissolved species present in the aqueous solution, and in the organic electrolyte solution, different electrochemical coupled reactions can be observed. This method enables a fast and convenient method to measure standard transfer potentials for example of ionised drug molecules.     

Study on a New Type of All-Solid-StateReference Electrode

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Spillover on a Platinum Electrode Modified by MWNTs

The spillover phenomenon is observed on the platinum (Pt) disk electrode modified by multi-wall carbon nanotubes (MWNTs). The rate of the spillover of oxygen-containing species produced on Pt surface to and from MWNTs is fast. However for hydrogen-adatoms, the spillover is very weak. The selective spillover on the Pt/MWNTs electrode may provide a novel way to design catalysts.     

TOF-SIMS investigations on thermally treated copper–molybdenum films on a carbon substrate

Metal-matrix composites are made of materials with different physical and chemical properties. It is possible to change the mechanical, thermal and electrical properties by variation of the mass ratio of the components; therefore, metal-matrix composites have great value for industrial and technological applications. Copper–carbon composites have a good chance to be used as heat sinks for electronic components, which can be explained by their high thermal conductivity, low density and an adjustable coefficient of thermal expansion. On the other hand, the mechanical adhesion of copper and carbon is extremely weak because of their immiscibility and weak chemical interactions. In order to compensate for the low wettability of carbon by copper, a thin molybdenum intermediate layer is used as an adhesion promoter. In this work a time of flight secondary ion mass spectrometry technique was primarily used to detect the carbide formation in the molybdenum and copper layers, depending on different temperature conditions during sputter deposition and annealing afterwards. The CuMo layers were deposited by magnetron sputtering. The adhesion of the samples was determined by a destructive pull-off test. We found that heat treatment mainly modifies the carbide formation in the molybdenum and copper layers.     

Studies on the Crystal Structure and Photoluminescence of a Mercury(Ⅱ)Complex Based on a Novel Pyridine Ligand

<正>A novel mercury(n)complex HgL_2Br_2 was prepared from HgBr_2 and the organic ligand 2-(N-methyl-N-(4-((E)-2-(pyridine-4-yl)vinyl)phenyl)amino)ethanol(L).The ligand was synthesized and then characterized by FT-IR spectroscopy,~1H NMR,mass spectrum and elemental analysis,while the single-crystal diffraction data of the complex were collected on a Siemens Smart CCD diffractometer.The complex crystallizes in triclinic space group P_1~-with a=5.367(5),b= 12.466(5),c=23.945(5)(?),α=90.812(5),β=96.318(4),γ=96.093(5)°,Z=2,D_c=1.817g·cm~(-3),μ=7.395 mm~(-1),S=0.825,and the final R=0.0396.The Hg(Ⅱ)ion in the distorted tetrahedral mercury(Ⅱ)complex C_(32)H_(36)HgBr_2N_4O_2 is coordinated by two N atoms from the two ligands together with two bromide ions.Solid-state emission of the ligand and its complex has been investigated at room temperature.     

Amphiphilic α-helix mimetics based on a benzoylurea scaffold

The design and synthesis of amphiphilic benzoylurea α-helix mimetics is described. These conformationally constrained molecules allow for the correct angular and spatial projection of hydrophobic and hydrophilic groups and thus the reproduction of side-chains on both faces of an α-helix.     

Gramicidin A interaction at a dioleoyl phosphatidylcholine monolayer on a mercury drop electrode

A biosensor where the sensing surface is a fluid dioleyl phosphatidylcholine monolayer (DOPC) deposited on a mercury drop was used. The lipid monolayer was held in 0.1 M NaCl and a concentration of gramicidin A in the range 0-12 nM was used. Electrochemical impedance spectroscopy in the frequency range 0.1-65 kHz was employed to investigate how the defect-free monolayer responds to interactions of gramicidin A in solution.The data was analyzed both with multivariate data analysis and classical electrochemical methods. The principal component analysis of the resulting impedance spectra gave a linear dependence on the concentration of gramicidin A. An increasing permittivity was observed in the low-frequency regime with increasing concentration of gramicidin A in solution.     

Oxygen photoevolution on a tantalum oxynitride photocatalyst under visible-light irradiation: how does water photooxidation proceed on a metal-oxynitride surface?

The mechanism of water photooxidation (oxygen photoevolution) on a TaON photocatalyst was studied on the basis of our previous studies on the mechanism of this reaction on TiO(2) and N-doped TiO(2). We have confirmed that photocatalytic O(2) evolution occurs from an aqueous TaON suspension in the presence of Fe(3+), as reported. In-situ MIR-IR experiments have indicated that the TaON surface is slightly oxidized under visible-light irradiation, indicating that the oxygen photoevolution on TaON actually occurs on a thin Ta-oxide overlayer. The in-situ MIR-IR experiments have also shown that a certain surface peroxo species, tentatively assigned to adsorbed HOOH, is formed as an intermediate of the O(2) photoevolution reaction. Studies on the effect of addition of reductants to the electrolyte on the IPCE have shown that photogenerated holes at the TaON surface cannot oxidize reductants such as SCN(-), Br(-), methanol, ethanol, 2-propanol, and acetic acid, though they can oxidize H(2)O into O(2). Detailed considerations of these results have strongly suggested that the water photooxidation reaction on TaON proceeds by our recently proposed new mechanism, that is, the reaction is initiated by a nucleophilic attack of a water molecule (Lewis base) on a surface-trapped hole (Lewis acid).     

Study on a Pyruvate Oxidase Biosensor Based on β-Cyclodextrin with Ferrocene as Electron-Transfer Mediator

Abstract

A pyruvic acid biosensor was constructed by the use of ferrocene, which was included in the β-cyclodextrin as electron-transfer mediator, as well as glutaraldehyde cross-linked membrane of egg white and β-cyclodextrin as matrix of enzyme immobilization. Because of the excellent electron-transfer efficiency of ferrocene, the microenvironment from β-cyclodextrin, and also the inclusion complexation between them, the biosensor has quite good properties. The linear detection limiting of this biosensor decreased to 5.68 × 10^?7 mol/L with excellent stability for 2.58% of relative standard deviation (RSD) during six individual detections.     

Studies on Synthesis of a Cycloheptapeptide and Effects of Different Metal Ions on the Cyclization

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Locating a double vacancy or Stone–Wales point defect on a hexagonal quantum grid

Journal of Mathematical Chemistry - A graphene nano-ribbon structure can be modelled by a 3-regular hexagonal grid. We convert this to a rectangular coordinate system in order to identify uniquely...     

Metallacycle-based complexes based on a flexible pyridyl–benzimidazole derivative

Three new coordination complexes, {Cd(pbmb)(NO₃)₂} _n (1), {Ag(pbmb)(NO₃)(C₃H₆O)} _n (2), and {Hg₂(pbmb)₂Cl₄} _n (3), have been synthesized under solvothermal or solution reactions based on a flexible N-heterocyclic ligand 1-((2-(pyridin-4-yl)-1H-benzoimidazol-1-yl)methyl)-1H-benzotriazole (pbmb) and structurally characterized by single-crystal X-ray diffraction, IR spectrum, and elemental analyses. Both 1 and 2 display a 1-D chain structure with metallacycle unit while 3 shows a binuclear cycle motif. The aromatic rings are directing groups for π?···?π stacking interactions. The π?···?π interactions and hydrogen bonds extend the simple chain structure and binuclear structure to 3-D supramolecular architectures. Complexes 1 and 3 exhibit strong luminescence in the solid state at room temperature whereas 2 shows fluorescence quenching.     

Molecular recognition of a self-assembled monolayer of a polydithiocarbamate derivative of β-cyclodextrin on silver

The synthesis and molecular recognition properties of a new sulfur containing β-cyclodextrin (β-CD) derivative chemisorbed on a silver surface are described. Hepta-6-amino-6-deoxy-β-CD was allowed to react with CS₂ in the presence of ammonia to give a mixture of partially substituted dithiocarbamate derivatives with an average degree of substitution of 4.5. A modified silver electrode with this derivative is capable of discriminating between the three positional isomers of nitrobenzoate ion and nitrophenol, as determined by cyclic voltammetry. Only the meta- and para-isomers give a signal corresponding to the reduction of the nitro group. This is attributed to the different orientations of the nitro group with respect to the silver surface after inclusion in the CD cavity. Experiments in the presence of cyclohexanol showed a decrease in signal intensity of the meta- and para-isomers which is associated with the competitive complexation of this guest, suggesting that the electroactive probe is complexed to the cavity.