A photovoltage-based integrated sensor for extracellular redox potential measurement and acidification detection

In this study,photovoltage technique is applied in the development of a monolithically integrated sensor for redox(reduction–oxidation)potential and pH measurement.The sensor employs the electrolyte–insulator–semiconductor structure,with deposition of a layer of gold metal on partial surface of insulator silicon dioxide.Silicon dioxide and gold layer on a single chip form two distinct sensing sites,by sharing the same measuring system,the detection of redox potential and pH variation can be realized.In this work,the sensor characteristics is tested,and the sensitivity for redox potential and pH measurement is53.8 mV/log([Fe(II)]/[Fe(III)])and 44.3 mV/pH respectively.To demonstrate the validity of the sensor in extracellular detection,neonatal rat kidney cells are cultured on the sensor surface and then packaged in a flow chamber,thus the acidification rate of metabolites and the redox potential variation in extracellular microenvironment can be continuously monitored.Experimental results indicate increasing acidification and reducing potentials under physiological conditions.The synthesis parameters have potentials in detail revelation of cell metabolism.     

酪氨酸酶和漆酶的直接电化学研究

首次报道了吸附在活性炭表面的酪氨酸酶(Tyr)和漆酶(Lac)能进行准可逆的直接电化学反应，并保持对氧还原的电催化作用．本文所用的固定酶的方法具有简单、易于操作和酶活性保持良好等优点，可用于研究氧化还原蛋白质和酶的直接电化学和用于制备生物燃料电池的催化剂．     

两电子量子环的磁场效应

使用矩阵对角化方法,研究了磁场中两电子量子环自旋单态和三重态的电学和光学性质,发现磁场强度对两电子量子环的能谱和光吸收有强烈的影响.计算结果显示两电子量子环的光吸收系数可以达到107/m,这个结果要比两电子量子点高一个数量级.通过引入磁场和改变量子环半径可以获得较大的吸收系数.     

Reversible redox energy coupling in electron transfer chains

Reversibility is a common theme in respiratory and photosynthetic systems that couple electron transfer with a transmembrane proton gradient driving ATP production. This includes the intensely studied cytochrome bc1, which catalyses electron transfer between quinone and cytochrome c. To understand how efficient reversible energy coupling works, here we have progressively inactivated individual cofactors comprising cytochrome bc1. We have resolved millisecond reversibility in all electron-tunnelling steps and coupled proton exchanges, including charge-separating hydroquinone-quinone catalysis at the Q(o) site, which shows that redox equilibria are relevant on a catalytic timescale. Such rapid reversibility renders popular models based on a semiquinone in Q(o) site catalysis prone to short-circuit failure. Two mechanisms allow reversible function and safely relegate short-circuits to long-distance electron tunnelling on a timescale of seconds: conformational gating of semiquinone for both forward and reverse electron transfer, or concerted two-electron quinone redox chemistry that avoids the semiquinone intermediate altogether.     

多壁碳纳米管修饰电极对儿茶素的电催化作用

用循环伏安法研究了儿茶素在玻碳电极(GCE)和多壁碳纳米管修饰玻碳电极(MWCNT/GCE)上的电化学行为,探讨了电极反应机理。结果表明:MWCNT/GCE对儿茶素具有显著的电催化作用,儿茶素在MWCNT/GCE上的氧化还原峰电位差比在GCE上明显减小,且峰电流显著增加。电极反应为2电子、2质子转移的准可逆反应过程。     

类超电容活性炭的电容去离子除盐性能

采用类超电容活性炭作为电极材料,通过涂层的方法制备了活性炭电极,并构造了简易的电容去离子(CDI)反应装置.通过BET和DFT法测定了电极材料的比表面积、孔容及孔径分布,分析了电极的SEM图像.测定不同电压下溶液电导率、出水pH值,研究了电极的吸、脱附性能及电极反应情况.结果表明类超电容活性炭具有发达的微孔和一定数量中孔;电压范围在08~18V时,随着电压的升高,吸附脱盐效率也升高,并且30min内离子可完全脱附,电极再生性较好.吸附时不同电极电压下溶液pH值的升高或降低,表明阴阳两极不同的电化学氧化还原反应.     

The crystal structure of an oxygen-tolerant hydrogenase uncovers a novel iron-sulphur centre

Hydrogenases are abundant enzymes that catalyse the reversible interconversion of H(2) into protons and electrons at high rates. Those hydrogenases maintaining their activity in the presence of O(2) are considered to be central to H(2)-based technologies, such as enzymatic fuel cells and for light-driven H(2) production. Despite comprehensive genetic, biochemical, electrochemical and spectroscopic investigations, the molecular background allowing a structural interpretation of how the catalytic centre is protected from irreversible inactivation by O(2) has remained unclear. Here we present the crystal structure of an O(2)-tolerant [NiFe]-hydrogenase from the aerobic H(2) oxidizer Ralstonia eutropha H16 at 1.5?? resolution. The heterodimeric enzyme consists of a large subunit harbouring the catalytic centre in the H(2)-reduced state and a small subunit containing an electron relay consisting of three different iron-sulphur clusters. The cluster proximal to the active site displays an unprecedented [4Fe-3S] structure and is coordinated by six cysteines. According to the current model, this cofactor operates as an electronic switch depending on the nature of the gas molecule approaching the active site. It serves as an electron acceptor in the course of H(2) oxidation and as an electron-delivering device upon O(2) attack at the active site. This dual function is supported by the capability of the novel iron-sulphur cluster to adopt three redox states at physiological redox potentials. The second structural feature is a network of extended water cavities that may act as a channel facilitating the removal of water produced at the [NiFe] active site. These discoveries will have an impact on the design of biological and chemical H(2)-converting catalysts that are capable of cycling H(2) in air.     

三价铜的化学

通过70篇文献的考察对三价铜的发展在下列方面进行了论述:结构及各种存在形式;UV-VIS光谱及电极电位;三价铜做氧化剂在分析化学中的应用;氧化还原体系的反应动力学及机理,指出了某些问题应进一步研究,揭示了一些尚未开发的课题。     

Dual-component NMDA receptor currents at a single central synapse

Present thinking about the way that the NMDA (N-methyl-D-aspartate) class of glutamate receptor operates at central synapses relies mainly on information obtained from single-channel and whole-cell recordings from cultured neurons stimulated by exogenous NMDA receptor agonists. The mechanisms that operate in the postsynaptic membrane of a normal neuron following release of the natural transmitter are far less clear. An important problem is that most normal neurons receive many excitatory synapses (10(3)-10(5) per cell) and these synapses are located on slender dendritic elements far away from the somatic recording site, making the study of discrete synaptic events difficult. Typically, when populations of synapses are activated, NMDA receptor-mediated synaptic potentials appear as slowly rising, long-lasting waves superimposed on faster, non-NMDA-receptor potentials. Although believed to be critical for NMDA receptor function, this slow time-course would not be predicted from single-channel kinetics and its origin remains puzzling. We have now analysed the events occurring at the level of a single excitatory synapse using a simple, small, neuron--the cerebellar granule cell--which has an unusually simple glutamatergic input. By applying high-resolution whole-cell recording techniques to these cells in situ, we were able to study the nature of elementary NMDA receptor-mediated synaptic currents. Contrary to expectations, the prominent currents are fast but are followed by slow ones. Both types of current are strongly voltage-dependent but differ subtly in this respect. Furthermore, the currents are absent unless glycine is provided.     

钒电池充放电测试系统及测试方法研究

为了检测钒电池的充放电性能,根据全钒液流电池的特点,标称出钒电池的额定参数。在不同电流密度下对单体钒电池进行充放电容量测试实验。比较了不同电流密度下的充电曲线,从理论上分析充电差异的原因,总结充电电流与钒电池容量的关系。实验表明,对钒电池进行充放电时采用的电流密度为60~80 m A/cm2之间的值,钒电池电学性能参数最佳。     

水溶液中I~-I_2-X~-(X=F、Cl、Br)体系的循环伏安研究

测定了室温下(20±1℃),H_2SO_4水溶液中I~-及I_2分别在F~-、C1~-、Br~-存在时,在Pt电极上的循环伏安图.I~-C1~-及I~-Br~-体系在0.2—1.0V(vs.SCE)范围内,都有两对基本可逆的氧化还原峰.第一对氧化还原峰的位置和峰高不随C1~-或Br~-.的浓度而变化,对应于反应:2I~-(?)I_2+2e;第二对氧化还原峰的位置随Cl~-或Br~-的浓度增加而负移,但峰高不变,浓度增大10倍,峰电势分别负移88±2mV和113±2mV,与由I_2-C1~-及I_2-Br~-体系在0.6-1.0V范围内得到的规律一致,对应的反应分别为I_2C1+3C1~-(?)2C1_2+2e和I_2+4Br_-(?)2IBr_2-+2e.F~-在该电势范围内不参与反应.     

SiW11O39Fe(Ⅲ)(H2O)5-的电化学性质及电催化还原过氧化氢

 用循环伏安和交流阻抗等方法详细研究了SiW₁₁O₃₉Fe(Ⅲ)(H₂O)^5- (SiW₁₁Fe)的电化学性质和对H₂O₂ 还原的间接电催化作用,并与PW₁₁O₃₉Fe(Ⅲ)(H₂O)_4- (PW₁₁Fe)进行了比较,同时提出了电催化反应的机理。实验结果表明,与PW₁₁Fe 类似,SiW₁₁Fe在酸性水溶液中也有3对还原氧化伏安响应,分别归属于Fe(Ⅲ)/Fe(Ⅱ)电对和W-O骨架的还原氧化反应。但SiW₁₁Fe的3对还原氧化波的峰电位与PW₁₁Fe)相比明显负移,且均受溶液pH的影响。SiW₁₁Fe中Fe(Ⅲ)/Fe(Ⅱ)电对传递电子的可逆性比PW₁₁Fe的差,但同样对H₂O₂ 的还原具有明显的电催化作用,并受溶液pH的影响。随着溶液pH的增加,Fe波和W-O骨架波的还原氧化峰电位均负移,Fe波对H₂O₂ 还原的电催化活性降低甚至被完全抑制,相反,第一个W-O骨架波对H₂O₂ 的还原却有明显的电催化作用。     

Redox evolution of a degassing magma rising to the surface

Volatiles carried by magmas, either dissolved or exsolved, have a fundamental effect on a variety of geological phenomena, such as magma dynamics and the composition of the Earth's atmosphere. In particular, the redox state of volcanic gases emanating at the Earth's surface is widely believed to mirror that of the magma source, and is thought to have exerted a first-order control on the secular evolution of atmospheric oxygen. Oxygen fugacity (f(O2) estimated from lava or related gas chemistry, however, may vary by as much as one log unit, and the reason for such differences remains obscure. Here we use a coupled chemical-physical model of conduit flow to show that the redox state evolution of an ascending magma, and thus of its coexisting gas phase, is strongly dependent on both the composition and the amount of gas in the reservoir. Magmas with no sulphur show a systematic f(O2) increase during ascent, by as much as 2 log units. Magmas with sulphur show also a change of redox state during ascent, but the direction of change depends on the initial f(O2) in the reservoir. Our calculations closely reproduce the H2S/SO2 ratios of volcanic gases observed at convergent settings, yet the difference between f(O2) in the reservoir and that at the exit of the volcanic conduit may be as much as 1.5 log units. Thus, the redox state of erupted magmas is not necessarily a good proxy of the redox state of the gases they emit. Our findings may require re-evaluation of models aimed at quantifying the role of magmatic volatiles in geological processes.     

Lectin-like polypeptides of P. falciparum bind to red cell sialoglycoproteins

Attempts to control human malaria by immunological means could be compromised by antigenic variability within and between different strains of malarial parasites1. A useful alternative approach might be to block parasite antigens which are important in the mechanisms of invasion of red cells. As the major human parasite Plasmodium falciparum is highly specific for human red cells, isolation of the proteins involved in the recognition of red cells by this parasite might be of particular value. Recent studies suggest that the major red cell sialoglycoproteins (SGPs), glycophorins A, B and possibly C, may carry the sites recognized by the parasite2-4. Furthermore, because certain carbohydrates present on SGPs such as N-acetylglucosamine are able to block invasion by the parasite5, they may be involved in the initial interaction between parasite and red cell. We have now identified parasite proteins which bind to SGP or N-acetylglucosamine on Sepharose 4B columns. Three proteins, of molecular weights (MWs) 140,000 (140K), 70K and 35K, seem to be specifically bound by N-acetylglucosamine.     

Aerobic anoxygenic phototrophic bacteria and their roles in marine ecosystems

Aerobic anoxygenic phototrophic bacteria(AAPB) are characterized by the following physiological and ecological features. A mother AAPB cell can unusually divide into 3 daughter cells and looks like a “Y” during the division. AAPB cells sometimes adhere together forming a free-floating population. Most of the known AAPB species are obligately aerobic. Bacteriochlorophyll a (BChl a) is the only photosynthetic pigment in AAPB, and the number of BChl a molecules in an AAPB cell is much less than that in an anaerobic phototrophic bacterial cell, while the accessorial pigments carotenoids in AAPB are abundant in concentration and diverse in species. In addition to the common magnesium containing BChl a, a zinc-containing BChla was also seen in AAPB. AAPB have light harvesting complex I but usually lack light harvesting complex II. Although AAPB featur in photosynthesis, their growth is not necessarily lightdependent. There is a mechanism controlling the photosynthesis approach. AAPB are widely distributed in marine environments especially in oligotrophic oceans accounting for a substantial portion of the total biomass and playing a unique role in the cycle of carbon and other biogenic elements. Besides the contribution to primary production, AAPB also have great potentials in bioremediation of polluted environments. Studies on AAPB would be of great value in understanding the evolution of photosynthesis and the structure and function of marine ecosystems.     

Mechanosensitivity of mammalian auditory hair cells in vitro

Intracellular responses recorded in vitro from the cochleas of anaesthetized mammals have shown that the mechanoreceptive inner and outer hair cells are sharply tuned, accounting for many of the properties of the afferent fibres in the auditory nerve. However, in vivo it has not been possible to measure directly the excitatory mechanical input to these cells (the displacement of their mechanosensitive stereocilia) and thus to determine the relationship between the receptor potentials and displacement of their stereocilia. As a means of circumventing this technical difficulty, we have developed an organ culture of the mouse cochlea and here we describe the receptor potentials generated by the hair cells in response to direct displacement of their stereocilia.     

全钒氧化还原流体电池的电化学行为

本文介绍了全钒氧化还原流体电池及其结构和充放电机理。该电池是一种新型储能材料。它用ＶＯＳＯ４溶液作电极活性材料。一系列充放电试验结果表明,该电池具有良好的电化学性能。     

硫在二甲基亚砜介质中的电化学平衡图

本文在综合实验数据的基础上,计算了硫—二甲基亚砜体系中各种形态的分子、阴离子及阴离子自由基的标准化学势,并给出了该体系的二种电化学平衡图-电位-pS图和电位-logK_1图.在此基础上,探讨了该体系在电化学氧化还原过程中的电极行为和均相转化过程,为进一步研究该体系的平衡性质和电化学行为提供了热力学依据.     

Ni(Ⅳ)引发苯乙烯在纤维素上接枝共聚合反应

以超常价态过渡金属二羟基二过碘酸合镍(Ⅳ)酸钾(简称Ni(Ⅳ))为氧化剂、纤维素为还原剂,组成氧化还原引发体系,于碱性介质中,在纤维素表面引发苯乙烯接枝共聚合反应,测定了不同的Ni(Ⅳ)浓度、单体与纤维素质量比、反应温度、反应时间和pH值对接枝参数的影响,获得了接枝共聚合反应的最佳实验条件,得到了高接枝参数的接枝共聚物.用红外光谱(IR)、电镜等方法对共聚物结构进行了表征,探讨了引发机理.