Ascidians use a class of cysteine-rich proteins generally referred to as vanabins to reduce vanadium ions, one of the many biological processes that involve the redox conversion between disulfide and dithiolate mediated by transition-metal ions. To further understand the nature of disulfide/dithiolate exchange facilitated by a vanadium center, we report herein a six-coordinate non-oxido V^IV complex containing an unbound disulfide moiety, [V^IV(PS3″)(PS1″^S–S)] (1) (PS3″ = [P(C₆H₃-3-Me₃Si-2-S)₃]^3–, where PS1″^S–S is a disulfide form of PS3″). Complex 1 is obtained from a reaction of previously reported [V^V(PS3″)(PS2″S^H)] (2) (PS2″S^H = [P(C₆H₃-3-Me₃Si-2-SH)(C₆H₃-3-Me₃Si-2-S)₂] with TEMPO (TEMPO = 2,2,6,6-tetramethylpiperidin-1-yl)oxyl) via hydrogen atom transfer. Importantly, complex 1 can be reduced by two electrons to form an eight-coordinate V^IV complex, [V^IV(PS3″)₂]^2– (4). The reaction can be reversed through a two-electron oxidation process to regenerate complex 1. The redox pathways both proceed through a common intermediate, [V(PS3″)₂]⁻ (3), that has been previously reported as a resonance form of V^V-dithiolate and a V^IV-(thiolate)(thiyl-radical) species. This work demonstrates an unprecedented example of reversible disulfide/dithiolate interconversion mediated by a V^IV center, as well as provides insights into understanding the function of V^V reductases in vanabins.

中文翻译：

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在钒 (IV) 中心发生的二硫化物/二硫醇盐的可逆转化：Vanabin 中氧化还原交换的仿生系统

海鞘使用一类通常称为 vanabins 的富含半胱氨酸的蛋白质来减少钒离子，这是涉及由过渡金属离子介导的二硫化物和二硫醇盐之间的氧化还原转化的许多生物过程之一。为了进一步了解钒中心促进的二硫化物/二硫醇交换的性质，我们在此报告了一种六配位非氧化 V ^IV复合物，其中包含一个未结合的二硫化物部分，[V ^IV (PS3″)(PS1″ ^S–S )] ( 1 ) (PS3″ = [P(C ₆ H ₃ -3-Me ₃ Si-2-S) ₃ ] ^3–，其中 PS1″ ^S–S是 PS3″ 的二硫化物形式)。综合楼1从先前报道的 [V ^V (PS3″)(PS2″S ^H )] ( 2 ) (PS2″S ^H = [P(C ₆ H ₃ -3-Me ₃ Si-2-SH)( C ₆ H ₃ -3-Me ₃ Si-2-S) ₂ ] 与TEMPO (TEMPO = 2,2,6,6-四甲基哌啶-1-基)氧基)通过氢原子转移。重要的是，配合物1可以被两个电子还原形成八配位 V ^IV配合物，[V ^IV (PS3″) ₂ ] ^2– ( 4). 该反应可以通过双电子氧化过程逆转以再生复合物1。氧化还原途径均通过一个共同的中间体 [V(PS3″) ₂ ] ⁻ ( 3 )，之前曾报道过它是 V ^V -二硫醇盐和 V ^IV -(硫醇盐)(硫基自由基)的共振形式物种。这项工作展示了一个前所未有的由 V ^IV中心介导的可逆二硫化物/二硫醇盐相互转化的例子，并提供了理解vanabins中 V ^{V还原酶功能的见解。}