生物醌分子伏安响应的多电子转移辨析

电化学反应中，一个基元电子转移反应仅对应一个电子交换，实际上多电子转移反应也涉及对应数目的单电子转移步骤，分离、辨析每个电子基元反应的氧化还原峰电位十分重要. 本文以辅酶Q₀（CoQ₀）、亚甲基桥连双辅酶Q₀（Bis-CoQ₀）为模型，采用循环伏安和方波伏安技术研究其电化学特性，提出了一种应用于多电子转移体系、分析单个电子转移电位的方法. 实验表明，CoQ₀经历两步单电子还原反应；Bis-CoQ₀中两个醌单元发生强电子相互作用，电极过程为4电子多步转移. 对于表观上的4电子“三步”转移反应，拟用Lorentzian-Gaussian分峰拟合CoQ₀和Bis-CoQ₀体系方波伏安响应曲线，分别获取每个电子转移步骤的电位，进一步证明Bis-CoQ₀经历四分步单电子转移反应，为热力学研究提供更多信息.

Resolve Mono-Electronic Process in the Voltammetric Behaviors of Multi-Redox Bis-Coenzyme Q0

A widely held concept in electrochemistry is that truly elementary electron-transfer reactions always involve the exchange of one electron, therefore, an overall process involving a change of n electrons must involve n distinct electron-transfer steps. It is highly desirable to resolve multiple-step electron transfer reactions into each electron transfer step. The electrochemical behaviors of coenzyme Q₀ and methylene-bridged Bis-coenzyme Q₀ were investigated by cyclic voltammetry and square wave voltammetry in nonaqueous dichloromethane containing 0.15 mol·L^-1 Bu₄NClO₄ as the supporting electrolyte. The redox reaction of coenzyme Q₀ is well described as two chemically reversible one-electron reduction processes. Bis-coenzyme Q₀ exhibits three redox waves in voltammetric experiment, as two bridged coenzyme Q₀ units show strong intramolecular electron communication. Experimental data were curve fitted with a Gaussian and Lorentzian mixed product function after subtracting the Shirley background. Results show that four-electron reduction of Bis-coenzyme Q₀ is preceded by stepwise pathways, defining as four successive, mono-electronic electron-transfer steps.