The Q cycle mechanism proposed by Peter Mitchell in the 1970's explicitly considered the modification of ubiquinone two-electron redox properties upon binding to Complex III to match the thermodynamics of the other single-electron redox cofactors in the complex, and guide electron transfer to support the generation of a proton electro-chemical gradient across native membranes. A better understanding of the engineering of Complex III is coming from a now moderately well defined thermodynamic description of the redox components as a function of pH, including the Qi/heme b(H) cluster. The redox properties of the most obscure component, Qo, is finally beginning to be resolved.

中文翻译：

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复合物III中的醌和非醌氧化还原对。

彼得·米切尔（Peter Mitchell）在1970年代提出的Q循环机制明确考虑了与复合物III结合后对泛醌二电子氧化还原性质的修饰，以匹配复合物中其他单电子氧化还原辅因子的热力学，并指导电子转移以支持跨天然膜产生质子电化学梯度 对复合物III工程的更好理解来自对氧化还原成分随pH的函数的一个适度定义的热力学描述，其中包括Qi /血红素b（H）团簇。最模糊的成分Qo的氧化还原特性终于开始得到解决。