辣根过氧化物酶在Au-Gemini纳米复合物修饰玻碳电极上的直接电化学

将辣根过氧化物酶(HRP)固定在Au-Gemini纳米复合物修饰的玻碳(GC)电极表面,制备了HRP修饰电极(HRP/Au-Gemini/GC),研究了HRP在Au-Gemini纳米复合膜中的直接电化学,考察了其对H_2O_2的电催化还原作用.研究表明,HRP在Au-Gemini纳米复合膜中发生了准可逆的电化学反应,其氧化峰峰电位(E_(pa))和还原峰峰电位(E_(pc))分别为-0.236 V和-0.273 V.HRP/Au-Gemini/GC修饰电极对H_2O_2具有良好的电催化还原响应,其表观米氏常数K_m=2.0×10~(-5)mol/L,H_2O_2浓度在1.0～7.0μmol/L范围内与催化电流呈线性关系.该研究为实现氧化还原酶的直接电子传递和生物传感器的构制提供了一种有效途径.     

辣根过氧化物酶修饰电极的电化学研究

制备了考马斯亮蓝和多壁碳纳米管混合物修饰玻碳电极（CBB G-250/MWNT/GC）,考察了固定在该修饰电极上的辣根过氧化物酶的电子转移情况。结果表明,辣根过氧化物酶在该电极上实现了稳定的直接电子转移反应,循环伏安图上出现了一对对称性良好的氧化还原峰。直接电子转移反应的表观速率常数k_s=4.68s^-1,式量电位E^0′几乎不随扫速（至少在20～270mV/s的扫速范围内）而变化,平均值为（-0.333±0.002）V（参比Ag/AgCl pH 7.0）。式量电位和pH的良好的线性关系表明该修饰电极上辣根过氧化物酶的直接电化学反应是有质子参与的。实验结果还证实了该修饰电极上酶对底物H₂O₂有良好的电催化活性。该方法可为生物传感器和生物燃料电池酶电极的制备提供基础数据。     

锇聚合物修饰丝网印刷电极的辣根过氧化物酶传感器

酶生物传感器检测环境污染应用前景良好。该文采用戊二醛-牛血清白蛋白交联法将锇-聚乙烯基吡啶(Os(bpy)2(PVP)10Cl2,Os-PVP)与辣根过氧化物酶(HRP)依次固定在丝网印刷电极上,制备电流型过氧化氢生物传感器。通过循环伏安法对修饰电极的氧化还原性质进行研究,并采用计时-电流法对传感器的固定化和工作参数进行了研究,以便提高信号响应的灵敏度和稳定性。在最适合条件下,底物在修饰电极表面进行催化反应的表观Michaelis-Menten常数kampp为1.79mmol/L,并确定以HRP酶为标记物的免疫传感器所采用的底物浓度宜大于20倍的kmapp。     

锇聚合物修饰丝网印刷电极的辣根过氧化物酶传感器

酶生物传感器检测环境污染应用前景良好。该文采用戊二醛-牛血清白蛋白交联法将锇-聚乙烯基吡啶(Os(bpy)2(PVP)10Cl2,Os-PVP)与辣根过氧化物酶(HRP)依次固定在丝网印刷电极上,制备电流型过氧化氢生物传感器。通过循环伏安法对修饰电极的氧化还原性质进行研究,并采用计时-电流法对传感器的固定化和工作参数进行了研究,以便提高信号响应的灵敏度和稳定性。在最适合条件下,底物在修饰电极表面进行催化反应的表观Michaelis-Menten常数kampp为1.79 mmol/L,并确定以HRP酶为标记物的免疫传感器所采用的底物浓度宜大于20倍的kmapp。     

Structural snapshots along the reaction pathway of ferredoxin-thioredoxin reductase

Oxygen-evolving photosynthetic organisms regulate carbon metabolism through a light-dependent redox signalling pathway. Electrons are shuttled from photosystem I by means of ferredoxin (Fdx) to ferredoxin-thioredoxin reductase (FTR), which catalyses the two-electron-reduction of chloroplast thioredoxins (Trxs). These modify target enzyme activities by reduction, regulating carbon flow. FTR is unique in its use of a [4Fe-4S] cluster and a proximal disulphide bridge in the conversion of a light signal into a thiol signal. We determined the structures of FTR in both its one- and its two-electron-reduced intermediate states and of four complexes in the pathway, including the ternary Fdx-FTR-Trx complex. Here we show that, in the first complex (Fdx-FTR) of the pathway, the Fdx [2Fe-2S] cluster is positioned suitably for electron transfer to the FTR [4Fe-4S] centre. After the transfer of one electron, an intermediate is formed in which one sulphur atom of the FTR active site is free to attack a disulphide bridge in Trx and the other sulphur atom forms a fifth ligand for an iron atom in the FTR [4Fe-4S] centre--a unique structure in biology. Fdx then delivers a second electron that cleaves the FTR-Trx heterodisulphide bond, which occurs in the Fdx-FTR-Trx complex. In this structure, the redox centres of the three proteins are aligned to maximize the efficiency of electron transfer from the Fdx [2Fe-2S] cluster to the active-site disulphide of Trxs. These results provide a structural framework for understanding the mechanism of disulphide reduction by an iron-sulphur enzyme and describe previously unknown interaction networks for both Fdx and Trx (refs 4-6).     

硫氧还蛋白f介导的烟草Rubisco活化酶的氧化还原调控

利用菠菜和烟草的硫氧还蛋白f(Trx-f)在不同氧化还原状态下测定了菠菜、拟南芥、烟草和番茄Rubisco活化酶(RCA)活化其Rubisco的活力,实验结果显示菠菜Trx-f只能介导调控菠菜和拟南芥RCA的氧化还原状态,从而改变其活力,而烟草Trx-f介导也只能改变烟草和番茄RCA的氧化还原状态.上述结果表明烟草等物种的单亚型RCA也能受Trx-f介导的氧化还原调控,而且Trx-f介导的RCA氧化还原状态的改变具有种属专一性.     

Natural engineering principles of electron tunnelling in biological oxidation-reduction

We have surveyed proteins with known atomic structure whose function involves electron transfer; in these, electrons can travel up to 14 A between redox centres through the protein medium. Transfer over longer distances always involves a chain of cofactors. This redox centre proximity alone is sufficient to allow tunnelling of electrons at rates far faster than the substrate redox reactions it supports. Consequently, there has been no necessity for proteins to evolve optimized routes between redox centres. Instead, simple geometry enables rapid tunnelling to high-energy intermediate states. This greatly simplifies any analysis of redox protein mechanisms and challenges the need to postulate mechanisms of superexchange through redox centres or the maintenance of charge neutrality when investigating electron-transfer reactions. Such tunnelling also allows sequential electron transfer in catalytic sites to surmount radical transition states without involving the movement of hydride ions, as is generally assumed. The 14 A or less spacing of redox centres provides highly robust engineering for electron transfer, and may reflect selection against designs that have proved more vulnerable to mutations during the course of evolution.     

Direct electrochemistry and electrocatalysis of horseradish peroxidase in MnO2 nanosheet film

A novel material MnO2 nanosheet has been used as the support matrix for the immobilization of horseradish peroxidase （HRP）. HRP entrapped in MnO2 nanosheet film exhibits facile direct electron transfer with the electron transfer rate constant of 6.86 s^-1. The HRP/MnO2 nanosheet film gives a reversible redox couple with the apparent formal peak potential （E^0＇） of -0.315 V （vs. Ag/AgCl） in pH 6.5 phosphate buffer solution （PBS）. The formal potential E^0＇ of HRP shifts linearly with pH with a slope of -53.75 mV.pH^-1, denoting that an electron transfer accompanies single-proton transportation. The immobilized HRP shows an electrocatslytic activity to the reduction of H2O2. The response time of the biosensor for H2O2 is less than 3 s, and the detection limit is 0.21 μmol · L^-1 based on signal/noise = 3.     

半导体／液结费米能级钉着的理论分析

在半导体/金属接触的肖脱基结理论和半导体/溶液界面结构的 Gerischer-Nozik模型的基础上,推导出半导体/液结势垒高度的关系式,并定量地分析无表面态和高密度表面态两种极限情形中的势垒高度。结果表明前者决定于半导体的亲合能和氧化还原对的电位,后者不随氧化还原对的电位和外加电位而变化,费米能级钉着在表面态。n-GaAs 电极的光电效应和电反射效应的实验结果证明理论分析的合理性。     

正电子素探测多孔材料内表面特性

本文讨论了以正电子素为探针探测不同相结构的氧化铝和HY分子筛等多孔材料内表面的一些物理和化学性质.发现在α、θ混合桐的氧化铝中存在着孔径为不到1纳米的小孔和几个纳米的大孔,随着温度升高,小孔向着大孔方向扩胀.也发现在非活性的氧化铝中表面正电子素强度与孔的比表面积存在着线性关系,在活性氧化铝中却有明显的偏离.还发现正电子素在HY分子筛内表面和笼内与质子酸发生了氧化还原反应,并求出了反应速率常数。     

死路删除语义下的WS-BPEL流程的建模

提出一种新的模型——DPE网,用于描述死路删除语义下的WS-BPEL流程。DPE网中引入了颜色集CTRL和STAT以表示活动执行的状态和并发活动内链接的状态。这在一定程度上降低了模型的规模,从而得到更为直观的模型。基于DPE网,不仅描述了WS-BPEL流程的基本控制流,包括基本活动和各种结构化活动,而且描述了WS-BPEL流程的死路删除语义和较完整的link语义,包括join condition和transition condition。最后,通过一个实例说明了使用DPE网建模WS-BPEL流程,有助于得到更为准确的分析结果。     

Crystal structures of a multidrug transporter reveal a functionally rotating mechanism

AcrB is a principal multidrug efflux transporter in Escherichia coli that cooperates with an outer-membrane channel, TolC, and a membrane-fusion protein, AcrA. Here we describe crystal structures of AcrB with and without substrates. The AcrB-drug complex consists of three protomers, each of which has a different conformation corresponding to one of the three functional states of the transport cycle. Bound substrate was found in the periplasmic domain of one of the three protomers. The voluminous binding pocket is aromatic and allows multi-site binding. The structures indicate that drugs are exported by a three-step functionally rotating mechanism in which substrates undergo ordered binding change.     

Ⅲ-Ⅴ族半导体化合物(311)A表面的电子结构特征

在考虑最近邻、次近邻相互作用的SP3模型基础上,采用形式散射理论的格林函数方法计算了Ⅲ-Ⅴ族半导体化合物GaAs、InSb、InAs和GaP的(311)A表面的电子结构,给出了以上半导体材料体能带的表面投影能带结构,并给出了GaAs的(311)A表面的层态密度函数,分析了各表面态沿表面布里渊区高对称线的色散特性和(311)A表面的共同电子结构特征,计算结果与实验结果基本一致.     

Computed redox potentials and the design of bioreductive agents

Anti-cancer agents that have been made selective for tumour cells by exploiting the known differences in the availability of oxygen between normal and transformed cells are a promising development in cancer chemotherapy. We have recently suggested a new type of bioreductive activity which would depend on a two-electron reduction. For rational design of such compounds, it is essential to be able to predict the redox potentials and the chemical modifications needed to produce the optimum redox value. Calculating redox potentials is a daunting task for the theoretician, however, as the effect of water solvation is clearly of major significance. Recent successful calculations of differences in the free energies of biologically important molecules in aqueous solution using the free-energy perturbation method prompted us to apply the technique to the computation of two-electron redox potentials. The results are accurate to within 20 mV, suggesting that we should be able to manipulate redox potentials by successfully predicting structures with the appropriate value.     

磁性HRP的酶学研究

以磁性壳聚糖微球作载体对HRP进行固定化研究,同时为了便于比较,还用壳聚糖微球固定HRP.结果表明:磁性壳聚糖微球固定的HRP的理化性质优于壳聚糖微球固定的HRP,磁性酶因具有磁响应性,可方便、快速地从反应体系中分离.     

酶催化合成聚酚树脂的研究进展

概述了酶催化合成聚酚树脂用酶的种类、底物的结构、反应介质;比较了该树脂和传统酚醛树脂的生产、结构及性能特点;指出了其不仅具有良好的耐热性能,可作传统酚醛树脂的替代品,而且具有导电、发光等功能,在光电材料方面显示了极强的应用潜力,但降低HRP催化合成聚酚树脂的成本是其实现工业化亟待解决的问题。     

基于组件的软件系统的接口测试

软件测试在整个软件开发过程中占有非常重要的地位，现代软件系统越来越复杂，基于组件的软件工程方法为开发者提供了一个设计软件的方法。利用有限状态自动机可以描述组件各状态及状态间转换，程序执行状态图（PESC）及各种覆盖准则可用来描述程序执行状态及其变化，对于展开的状态图，由它来产生一棵测试树，该树包含了所有的测试路径。     

共价修饰的辣根过氧化物酶及其在酶传感器中的应用

将介体对甲酰苯基二茂铁（ＦＰＦ）与辣根过氧化物酶（ＨＲＰ）共价结合,然后同单体吡咯一起电聚合到铂电极上,再通过戊二醛将葡萄糖氧化酶（ＧＯＤ）交联固定在电极上,制成共价修饰的ＨＲＰ／ＧＯＤ介体酶传感器。共价修饰的酶传感器响应电流增大,底物测试范围０～４０ｍｍｏｌ／Ｌ,电极稳定性增强。     

应用EQCM研究含有二苯基联苯胺和二亚酰胺官能团的电活性聚合物的氧化还原过程

运用电化学石英晶体微天平技术(EQCM)联合循环伏安法(CV)和计时安培分析法对3种含有二苯基联苯胺和二亚酰胺的电活性聚合物薄膜进行了研究.这些聚合物薄膜具有多个氧化和还原状态.中性聚合物薄膜可以在二苯基联苯胺连接处被电化学氧化或在二亚酰胺处被电化学还原.在氧化还原转化过程期间,聚合物薄膜的电子转移、离子补偿和溶剂运输的动力学取决于聚合物的类型、其所处的氧化还原状态、电位扫描速率和氧化还原转换的方向.确定了包含二苯基联苯胺聚合物在不同电化学条件的氧化还原转化的机理.动力学控制步骤也许与聚合物薄膜在每个氧化还原状态的特定几何结构有关,并受到不同电解质和溶剂的影响.研究了含有二苯基联苯胺和二亚酰胺的电活性聚合物薄膜电子转移反应的级数、反离子补偿和溶剂传输,并定量地测定了氧化还原过程中离子和溶剂进出电活性膜的流量.     

固定化辣根过氧化物酶催化去除五氯酚

采用辣根过氧化物酶催化去除模拟废水中的五氯酚,使其形成沉淀;并探讨了影响反应的因素如溶液酸度、酶浓度、五氯酚起始浓度、过氧化氢起始浓度以及温度等。结果表明辣根过氧化物酶去除五氯酚的最佳 pH 为 5～6;去除率随酶浓度增加而增加,在所采用的最高酶浓度 0.05u/mL,五氯酚初始浓度为 12.6mg/L 的情况下,去除率可达 70％ 左右;五氯酚起始浓度对去除率也有一定影响,起始浓度为 13.0mg/L 时,去除率可达 73.7％,而当起始浓度为 0.7mg/L 时,去除率只有 35.7％;过氧化氢与五氯酚反应的摩尔数之比为 1∶2。此外还采用化学键合法将辣根过氧化物酶固定在聚丙烯酰胺载体上,发现酶活性可保持较长时间,并可反复用于催化去除五氯酚。固定酶去除五氯酚最适 pH 值与自由酶类似,并且在 pH＝5.15条件下,1h 内将五氯酚从 13.4mg/L 去除到4.9mg/L并达到平衡;将固定酶装入反应柱制成酶柱,可多次反复催化五氯酚的反应。