漫透射光谱电化学研究活菌细胞色素c蛋白介导的胞外电子传递过程  

Examination of extracellular electron transfer process mediated by c-type cytochrome in intact cells using a diffuse-transmittance spectro-electrochemical method

作　　者：吴云当 刘同旭 李芳柏 WU YunDang;LIU TongXu;LI FangBai(Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management,Guangdong Institute of Ecoenvironmental Science&Technology,Guangzhou 510650,China)

机构地区：[1]广东省生态环境技术研究所广东省农业环境综合治理重点实验室

出　　处：《中国科学：技术科学》2019年第12期1473-1482,共10页Scientia Sinica(Technologica)

基　　金：国家自然科学基金(批准号:41701305,41522105);珠江三角洲水质安全与保护教育部重点实验室开放课题(编号:201705)资助项目

摘　　要：微生物膜蛋白(细胞色素c)介导的微生物胞外电子传递过程,是元素生物地球化学循环、微生物修复、微生物燃料电池等领域的研究热点与重要科学问题.阐明细胞色素c的氧化还原变化规律是从分子层面解析该过程的基础.然而,由于技术手段限制,活菌细胞色素c氧化态和还原态的含量及其电位难以同时测定,其氧化还原状态的变化规律仍知之甚少.本文构建了漫透射光谱电化学联用装置,原位测试了活菌细胞色素c及电子受体的氧化态和还原态含量变化,并同时在线监测了反应体系的氧化还原电位值,从而实现了实测电位与各反应物计算电位之间相互关系的系统研究.结合动力学与热力学的分析,定量阐明了细胞色素c所处的氧化还原状态因电子受体的电位不同而发生变化的规律;解释了不同电子受体存在时,细胞色素c所处的平衡状态截然不同的原因.该技术手段在活菌层面实现了细胞色素c蛋白的动力学与热力学分析,可为胞外电子传递微观机制的研究提供新的方法与理论基础.Microbial extracellular electron transfer(EET) is a research hot spot in the fields of elemental biogeochemical cycling, microbial remediation, and microbial fuel cells. The key process of EET is c-type-cytochrome-mediated electron transfer from the inner to the outer membrane of the cell. Therefore, an understanding of the redox behavior of c-type cytochrome in intact cells is essential for elucidating the EET process at the molecular level. However, owing to technical limitations, the redox dynamics of cytochrome in intact cells are still poorly understood. In this study, a diffuse-transmittance spectro-electrochemical device was constructed, the redox changes in cytochrome and electron acceptors were in situ tested, and the redox potential of the system was monitored simultaneously.Based on the Nernst equation, the potential changes in the c-type cytochrome and acceptor were calculated, and the relationship between the calculated and measured potential was discussed. Results showed that the c-type cytochrome remained at an oxidized state when fumarate was presented as an electron acceptor. This was because the rate of c-type cytochrome oxidized by the electron acceptor was much higher than that of c-type cytochrome reduced by the electron donor. However, when flavin mononucleotide(FMN), an electron shuttle with lower potential, acted as the electron acceptor, the c-type cytochrome remained at a reduced state.Meanwhile, the potential of cytochrome dropped sharply and was then stabilized at a potential lower than that of FMN. From the thermodynamic analysis, regardless of the kinetic limitation, the reaction occurred spontaneously only when the potential of the c-type cytochrome was lower than that of the electron acceptor. Because the redox potential was determined by the redox state, the redox state of cytochrome was completely different in the presence of the electron acceptors with different potentials. This quantitative spectro-electrochemical study on the kinetics and thermodynamics of c-type cytochrome in

关 键 词：胞外电子传递 光谱电化学 细胞色素C 热力学与动力学 

分 类 号：O657[理学—分析化学] Q935[理学—化学]