High performance EQCM technique for analysis of ocidoreducetase

来自脱硫弧菌的细胞色素c3每个分子有四个血红素，血红素的氧化还原变化改变了蛋白质的构象，导致细胞色素C3与氧化还原配偶体相互作用的氧化还原依赖性变化这种相互作用中氧化还原依赖的变化由高性能电化学石英晶体微天平（EQCM）直接监测。该技术已得到改进，在溶液中具有高灵敏度。在该方法中，溶液中的细胞色素c3分子与固定有紫精的石英晶体电极静电缔合为单层，并且缔合的细胞色素c3的氧化还原由固定的紫精控制。该技术使得可以测量细胞色素c3对电极的接近或来自电极的排斥，并且因此监测随着电位扫描的质量变化的细胞色素c3和紫精上的静电络合物和电子转移络合物之间的相互转换。此外，同时测量侄女变化和电位阶跃揭示了当四种血红素被还原时细胞色素c3存储电子（电子池效应），即，氧化的细胞色素c3促进从固定的紫精分子接受电子，但是还原的细胞色素c3难以将接受的电子提供给紫精。

Cytochrome c3 from Desulfovibrio vulgaris has four hemes per molecule, and a redox change at the hemes alters the conformation of the protein, leading to a redox-dependent change in the interaction of cytochrome c3 with redox partners (an electron acceptor or an electron donor) .The redox-dependent change in this interaction was directly monitored by the high-performance electrochemical quartz crystal microbalance (EQCM) technique that has been improved to give high sensitivity in solution. In this method, cytochrome c3 molecules in solution associate electrostatically with a viologen-immobilized quartz crystal electrode as a monolayer, and redox of the associating cytochrome c3 is controlled by the immobilized viologen. This technique makes it possible to measure the access of cytochrome c3 to the electrode or repulsion from the electrode, and hence interconversion between an electrostatic complex and an electron transfer complex on the cytochrome c3 and the viologen as a mass change accompanying a potential sweep is monitored. In addition, simultaneous measurement of a niece change and a potential step reveals that the cytochrome c3 stores electrons when the four hemes are reduced (an electron pool effect), that is, the oxidized cytochrome c3 facilitates acceptance of electrons from the immobilized viologen molecule, but the reduced cytochrome c3 donates the accepted electrons to the viologen with difficulty.