Ascorbate oxidase

Ascorbate oxidase fromCucurbita sp. was isolated by ammonium sulfate precipitation and DEAE-dextran-silochrome column chromatography. The thermal and pH stabilities of the purified enzyme were investigated. TheK _M forl-ascorbic acid (1.5 mM) and chlorohydroquinone (0.37 mM) was determined. Substrate specificity of ascorbate oxidase was investigated and compared with those of laccases fromCoriolus hirsutus andCerrena maxima. Ascorbate oxidase was covalently bound to a polymeric membrane and used in an enzyme electrode for ascorbic acid.     

Study on the anodic reaction of Ni in an alkaline solution by transient pH detection based on scanning electrochemical microscopy (SECM)

The anodic reaction of Ni in an alkaline solution was studied by the tip–substrate voltammetry mode of scanning electrochemical microscopy (SECM) and cyclic voltammetry (CV). A platinum microdisc electrode was selected as the tip electrode, which functioned as a pH sensor with transient response capability. The pH value of the solution near the Ni electrode surface varied while the Ni substrate oxidation reaction occurred, and the pH variation could be detected by the tip faradic current. The cyclic voltammogram results showed that two types of hydroxides: i.e. α‐Ni(OH)₂ and β‐Ni(OH)₂ were formed during Ni oxidation in the lower potential region. In the proceedings of α‐Ni(OH)₂ → γ‐NiOOH and β‐Ni(OH)₂ → β‐NiOOH, the process of OH^? concentration decrease in the solution was ahead and behind of electron transfer in the solid phase, respectively. These results indicate that the OH^? adsorption process occurs as an elementary step in the former reaction and the H⁺ diffusion process from the inner to the outer layer of the solid phase occurs as a subsequent step in the latter reaction. The results also revealed that the oxide film on the Ni surface has a two‐layer structure. The real potential of the oxygen evolution reaction (OER) on the Ni surface with different cycles is also analyzed in the paper. Copyright © 2007 John Wiley & Sons, Ltd.     

Hydrolytic and transglycosylation reactions of N-acyl modified substrates catalysed by β-N-acetylhexosaminidases

The hydrolytic and transglycosylation capabilities of 35 fungal β-N-acetylhexosaminidases with p-nitrophenyl 2-amino-2-deoxy-β-d-glucopyranoside and its four N-acyl derivatives (CHO, COCH₂OH, COCH₂CH₃, COCF₃) as substrates were tested. The preparation of four novel p-nitrophenyl disaccharides from these unnatural substrates catalysed by enzymes from Aspergillus oryzae, Penicillium oxalicum and Talaromyces flavus represents a considerable extension of the synthetic potential of glycosidases.     

Coating and water permeation properties of SiO2 thin films prepared by the sol-gel method on nylon-6 substrates

Nylon-6 substrates were coated with SiO₂ thin films by the sol-gel method and their water permeability coefficient was evaluated. Methyltriethoxysilane (MTES) and tetraethoxysilane (TEOS) were used as starting materials. The addition of MTES to TEOS has enabled the formation of crack-free thin films on the substrates. The thin films strongly adhered to the substrates. The water permeability coefficients of nylon-6 substrates coated with these thin films decreased with the increase in the ratio of TEOS to the total alkoxides. The pretreatment of the nylon-6 substrates with -aminopropyltriethoxysilane was found to be effective to suppress the water permeability. The water permeability was suppressed by about 40% under the optimal condition.     

Preparation and partial characterization of a soluble site-to-site directed enzyme complex composed of alcohol dehydrogenase and lactate dehydrogenase

A soluble, bifunctional enzyme complex has been prepared by crosslinking lactate dehydrogenase and alcohol dehydrogenase with glutaraldehyde. The crosslinking was performed on a solid phase while the active sites of alcohol dehydrogenase and lactate dehydrogenase were held adjacent to one another with the aid of a bis-NAD analog. Subsequently, the enzyme complex was released from the solid phase. The soluble enzyme complex was then purified by using NAD-Sepharose as an affinity adsorbent. Based on gel filtration experiments, the complex was estimated to consist of one of each dehydrogenase. By using a third enzyme, lipoamide dehydrogenase, which competes with lactate dehydrogenase for NADH produced by alcohol dehydrogenase, the effect of site-to-site orientation was studied. It was found that about 83% of the NADH produced by alcohol dehydrogenase was oxidized by site-to-site oriented lactate dehydrogenase compared to a figure of only about 61% obtained in an identical system of separate enzymes. This indicates that given two alternative routes, the preference for the one to lactate dehydrogenase over the one to lipoamide dehydrogenase is enhanced when lactate dehydrogenase and alcohol dehydrogenase are site-to-site oriented.     

~3Δ、~3Π、~3Σ~＋Ni—CO分子簇的从头算研究

用从头算研究了ｄ空穴位置不同对Ｎｉ—ＣＯ成键机制的影响。结果表明，Ｎｉ—ＣＯ键中σ／π接受作用的相对强弱，取决于Ｎｉ—ＣＯ簇所处的能态。σ空间电子云较π空间电子云弥散，因而Ｎｉ—ＣＯ簇的稳定性与σ空间电子云的排斥密切相关。随着Ｎｉ４ｐσ轨道上电子占据数的增加，Ｎｉ—ＣＯ稳定性减弱。比较了分子簇Ｎｉ—ＣＯ与ＮｉＣＯ分子及ＣＯ／Ｎｉ化学吸附体系之间的性质。     

Printed plastic electronics and paperlike displays

Plastic electronic materials and high‐resolution printing methods may be important technologies for new classes of consumer electronic devices that are lightweight, mechanically flexible and bendable, and that can cover large areas at low cost. This article summarizes some of our recent work in this area. It focuses on the materials and patterning techniques that we used to produce plastic active‐matrix backplane circuits for a type of paperlike display. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3327–3334, 2002     

W／O型微乳液中超氧化物阴离子的产生——微环境中SOD酶活性测定方法 …

分别在水溶液中和W／O型CTAB／正戊醇／异辛烷／水微乳液体系中研究了测定SOD酶活性的邻苯三酚法,发现在反向微乳液中,"小水池"的低介电常数和pH抑制了底物超氧化物阴离子O2-·的产生．只有提高外加缓冲液的pH或"小水池"的水化度,才能得到所需浓度的O2-·,从而初步解决了在微乳液中SOD作用底物的产生问题,为在微乳液中准确测定SOD酶活性创造了条件．     

Characterization of the Converging Jet Region in a Triple Torch Plasma Reactor

Enthalpy probe measurements were taken of the converging plasma plume in a triple torch plasma reactor and related to substrate heat flux measurements. Results show excellent entrainment of process gases injected into the converging plasma plume by way of the central injection probe. At lower pressures (40 kPa), the plasma volume is equivalent to at least a 3 cm diameter, 4 cm long cylinder, with relatively uniform temperature, velocity, and substrate heat flux profiles when compared to a typical dc arc jet. Converging plasma plume size, substrate heat flux, and enthalpy profiles are also shown to be a strong function of applied system power. Substrate heat flux measurements show smaller radial gradients than enthalpy probe measurements, because of the high radial velocity component of gases above the substrate boundary layer. Enthalpy probe measurements were also conducted for diamond deposition conditions and approximate temperature and velocity profiles obtained. Problems with the uniform gas mixture assumption prohibited more accurate measurements. Reproducibility of enthalpy measurement results was shown with an average standard deviation of 11.8% for the velocity and 7.6% for the temperature measurements.