【作者】 张会娜；

【导师】 郭智勇；

【作者基本信息】 宁波大学 ， 物理化学， 2010， 硕士

【摘要】 利用电化学手段研究氧化还原蛋白质在电极上的电化学行为和电催化性能,可以理解和认识它们在生命体内的电子转移机制和生理作用,对于构建生物传感器和生物反应器具有重要的理论意义和实际意义。构成生物体新陈代谢的几乎全部化学反应都是在活性蛋白质―酶的催化下进行的,生物体中最基本的运动便是电荷的运动。细胞色素c(cyt-c)是生物体电子传递链中的一个组成部分,位于线粒体的内膜上,由于其在生命体内的氧化还原反应被认为是生物电化学氧化还原反应的典型例子,故cyt-c的电化学性质研究引起了人们广泛的关注。本论文对蛋白膜伏安法(PFV)进行了较为详细的综述,并用PFV对cyt-c直接电化学展开了一系列的研究和探索。具体包括如下内容:将cyt-c通过静电吸附作用直接固定在处理好的棱面热解石墨电极(EPPGE)上,用PFV研究了cyt-c氧化还原电位与pH和扫描速度的关系,考察了直接吸附在EPPGE电极表面的cyt-c耦合质子的电子传递行为,实验结果提示,高铁cyt-c还原为亚铁cyt-c时与质子传递没有关系,但亚铁cyt-c氧化为高铁cyt-c时耦合一个质子。由于cyt-c在EPPGE电极表面的直接吸附不牢固,水强力冲洗电极表面或在溶液中浸泡五分钟则观察不到cyt-c的电化学信号。故用海藻酸钠水凝胶(SA hydrogel)和琼脂糖(agarose)水凝胶将cyt-c固定在EPPGE表面,形成稳定的hydrogel-cyt-c/EPPGE电极,研究了cyt-c与电极表面之间的直接电化学,和离子强度、pH、外加金属离子对其电化学行为的影响以及其电催化性能。结果表明:cyt-c中血红素辅基Fe(III)/Fe(II)电对表现出准可逆行为,外加金属离子则有抑制作用,该电极可催化还原氧,有可能发展成为一种溶解氧的生物传感器。离子液体可作为一些生物催化过程的理想介质,蛋白质在离子液体中不仅不会失活,而且其在离子液体中的稳定性也比在有机溶剂中的稳定性好。本文开展了两种离子液体中金电极(Au)、EPPGE和玻碳电极(GC)上固载在agarose水凝胶中的cyt-c的直接电化学的研究,考察了agarose-cyt-c膜中DMF加与不加、离子液体中含水量、蛋白质溶液中加入金属离子对cyt-c电化学行为的影响及cyt-c的电催化性能。结果表明:agarose-cyt-c膜中加入DMF后,cyt-c则表现出好的准可逆氧化还原过程,电极连续扫描50圈峰型无变化。在非水的亲水性离子液体中,必须加入少量的水分,才能保持cyt-c的电化学活性,cyt-c在[Bmim][Br]和[Bmim][BF4]含水量分别为5.2%和5.8%时电化学活性最好。外加金属离子对cyt-c电化学行为有抑制作用。固载在GC和EPPGE电极上的cyt-c在[Bmim][BF4]中对三氯乙酸、叔丁基过氧化氢有电催化还原作用,而在[Bmim][Br]中则无。初步探讨了cyt-c在不同电极、不同离子液体中的电化学性质差异的原因。更多还原

【Abstract】 By studying the electrochemical behavior and electrocatalytic properties of redox proteins on electrodes with electrochemical methods, we could understand the electron transfer mechanism and biological function in vivo, which are significant for theory and practice to construct biosensors and bioreactors. In fact, most chemical reactions during the metabolism are catalyzed by active protein-enzymes, and the basal movement in human body is charge movement. Cytochrome c (cyt-c) is located on the inner mitochondrion membranes of living cell, and is a part of the electron transport chain. As its redox reaction in vivo may be considered as a model and test system for bioelectrochemical redox ones, its electrochemical properties have been studied extensively. In this work, protein film voltammetry (PFV) was reviewed detailedly, and then a series of research and exploration on direct electrochemistry of cyt-c were carried out by PFV. The details are as follows:Cyt-c was electrostatically adsorbed on the surface of the edge plane pyrolytic graphite electrode (EPPGE). Then, the relationship between redox potential of cyt-c and pH and the scan rate was studied by PFV, thus to investigate proton-coupled electron transfer of cyt-c directly adsorbed on EPPGE surface. Results suggested that the reduction of ferricytochrome c is independent of proton, but the oxidation of ferrocytochrome c is coupled by a slow one-proton transfer process.Because direct adsorption of cyt-c on the EPPGE surface is not firm, electrochemical signals of cyt-c would not be monitored any longer if the electrode was rinsed strongly or immersed in solution for more than five minutes. Therefore, cyt-c entrapped in sodium alginate (SA) and agarose hydrogel was electrostatically bound to EPPGE, thus to prepare stable hydrogel-cyt-c/EPPGE. Then, direct electrochemistry between cyt-c and the electrodes, effects of ionic strength, pH and exterior substances on the direct electrochemistry, and electrocatalytic properties of cyt-c were monitored by PFV. Results showed that the electrochemical behavior of Heme Fe(III)/Fe(II) in cyt-c is quasi-reversible, and the peak currents are inhibited by exterior metal ions. Catalytic reduction of oxygen could be achieved by the hydrogel-cyt-c/EPPGE, which means that it could be developed into a kind of biological sensor for dissolved oxygen possibly.Ionic liquids can be used as ideal mediums for some bio-catalytic processes, in which proteins are not inactivated but more stable than in other organic solvents. In this paper, direct electrochemistry of cyt-c entrapped in agarose hydrogel on gold electrode (Au), EPPGE and glassy carbon electrode (GC) in two room temperature ionic liquids was investigated. The effects of the addition of DMF in the agarose-cyt-c film, water concentration in ionic liquids and exterior metal ions on the electrochemical behavior of cyt-c were monitored, and electrocatalytic properties of cyt-c were also done. Results showed that a good quasi-reversible redox behavior of cyt-c could be found after adding DMF in agarose-cyt-c film, and peak shape would not change after continuously scanning for 50 cycles. In addition, a certain amount of water in hydrophilic ionic liquids is necessary to maintain electrochemical activities of cyt-c, electrochemical performance of cyt-c is the best when the water content is 5.2% and 5.8% for [Bmim][Br] and [Bmim][BF4] respectively. However, electrochemical activities of cyt-c are inhibited by exterior metal ions. Interestingly, Cyt-c entrapped in agarose hydrogel on EPPGE and GC could catalyze the electroreduction of trichloroacetic acid and t-BuOOH in [Bmim][BF4], but could not in [Bmim][Br]. Reasons for above-mentioned differences of electrochemical properties of cyt-c in different ionic liquids were preliminarily discussed.更多还原