REDOX CHEMISTRY OF VITAMIN B12 DERIVATIVES

本研究项目的目标是将电化学技术应用于 钴皮质类固醇化合物的体外有序研究技术 了解酶反应中Co-C键的活化情况。 我们的长期目标之一是研究氧化还原化学。 维生素B12的种类，以期了解它们的参与 在生化过程中。考虑到这一目标，我们计划研究两个 机制方案：(I)有机-B12物种的还原裂解和 (Ii)B12催化的还原反应。第一个项目，(I)将是 烷基钴胺、烷基钴酰胺类化合物还原过程的研究 并使用电化学技术对系统进行建模，以便了解 详细介绍了碳-钴的还原解理机理。 电子转移反应使键断裂。我们的目标是获得 关于取代基结构如何影响(A)还原的信息 有机B12物种的势能和(B)电子的速率常数 转移和Co-C键裂变。这些结果可能有助于 了解Co-C键在酶反应中是如何被激活的。在……里面 在大多数情况下，Co-C键在电子之后断裂的速度非常快 转移事件和用于跟随这些事件的电化学技术 已经发展了毫秒和纳秒时间域中的反应 来研究这些过程。实验考察了溶剂、pH、 并且反应步骤的温度依赖性也是必要的 机制的完整图景。 待研究的第二类电化学过程，(Ii)是 维生素B12催化的还原，例如有氧的氧气还原 系统。这种反应需要形成一种还原的维生素B12 物种，Co(II)，B12r，或Co(I)，B12s，然后可以反应 迅速地与氧气或其他底物一起。在这里，速度和产品 该过程将通过伏安法和光谱电化学进行研究。 在不同的电极。我们还计划使用表面增强拉曼 光谱(SERS)以阐明这些化合物中B12中间体的性质 反应。

The goals of this research project are to apply electrochemical techniques to the study of the Co corrinoid compounds in vitro in order to understand the activation of the Co-C bond in enzymatic reactions. One of our long term objectives has been the study of the redox chemistry of vitamin B12 species with a view toward understanding their involvement in biochemical processes. With this goal in mind, we plan to study two mechanistic schemes: (i) the reductive cleavage of organo-B12 species and (ii) B12 catalyzed reduction reactions. The first project, (i) will be a study of the reduction process of alkylcobalamins, alkylcobinamides, and model systems using electrochemical techniques in order to understand in detail the reductive cleavage mechanism in which the carbon-cobalt bond is cleaved by an electron transfer reaction. Our aim is to obtain information on how substituent group structure affects (a) the reduction potentials of organo-B12 species and (b) the rate constants for electron transfer and for Co-C bond fission. These results could help in understanding how the Co-C bond is activated in enzymatic reactions. In most cases, Co-C bond breaking is exceptional fast following an electron transfer event and electrochemical techniques for following such reactions in the musecond and nanosecond time domain have been developed to study these processes. Experiments to investigate the solvent, pH, and temperature dependence of the reaction steps are also necessary for a complete picture of the mechanisms. The second type electrochemical process to be investigated, (ii), is vitamin B12 catalyzed reductions, e.g., oxygen reduction for aerobic systems. This reaction requires the formation of a reduced vitamin B12 species, the Co(II), B12r, or the Co(I), B12s, which then can react rapidly with oxygen or other substrates. Here the rate and products of the process will be studied by voltammetry and spectroelectrochemistry at various electrodes. We also plan to use surface enhanced Raman spectroscopy (SERS) to elucidate the nature of B12 intermediates in these reactions.