IRON AND MOLYBDENUM COMPLEXES--ENZYME ACTIVE SITES

合成，结构，光谱性质，电化学性质 特定Fe/M/S簇合物（M=Mo，W，V）的性质和反应性， Fe/S团簇和Mo/S/O复合物将是本研究的具体目标 提议 Fe/M/S团簇有望作为合成类似物 固氮酶和交替固氮酶中的Fe/M/S中心 用钒或铁代替钼 一种Fe/S 将合成簇作为亚硫酸盐中活性位点的模型， 亚硝酸还原酶 其他人工合成的Fe/S簇将是“混合”的。 末端配体Fe 6S 6“prismanes”预计将作为新的模型 铁氧还蛋白含有Fe 6S 6金属核心。 大量的Mo 含酶（氧转移酶） 通过氧代转移反应催化有机底物的氧化 涉及特定的Mo[VI]=O单元。 这些单位是一个共同的 发现总是与蝶呤结合的 二硫杂环戊烯配体 目前这种“非无辜”配体的功能 是不被理解的，我们将进行研究。 生物体系中的电子转移与氧化还原 生物体中各种基质的合成具有根本的重要性 to life sustaining维持processes流程. 多电子转移过程较少 在自然界中是常见的，但同样重要。 列入 它们是：光合作用中2 H2O到O2的4 e-氧化， 固氮酶中N2还原为氨， 在亚硫酸盐和亚硝酸盐中，亚硫酸盐转化为硫化物，亚硝酸盐转化为氨 还原酶分别。 一个似乎与 与涉及生物学的多电子氧化还原过程的位点， 一种复杂的超分子结构，由桥接的氧化还原活性 亚单位。 影响多电子氧化还原过程的因素 这种超结构还不清楚，适当的合成 可用作模型的群集并不容易获得。 这 建议是关于综合和研究模型， 固氮酶和亚硫酸盐还原酶以及 含有氧化还原活性亚基。 桥连配体的作用 亚基之间，对氧化还原电位和能力的 影响基质特定氧化或还原的组件 分子，将被评估。

The synthesis, structures, spectroscopic properties, electrochemical properties and reactivities of specific Fe/M/S clusters (M=Mo, W, V), Fe/S clusters and Mo/S/O complexes will be the specific aims of this proposal. The Fe/M/S clusters are expected to serve as synthetic analogs for the Fe/M/S centers in the nitrogenases and alternate nitrogenases that contain vanadium or iron in place of molybdenum. One type of Fe/S clusters will be synthesized as models for the active site in sulfite and nitrite reductase. Other synthetic Fe/S clusters will be the "mixed" terminal ligand Fe6S6 "prismanes" expected to serve as models for the new ferredoxins that contain the Fe6S6 metal cores. A great number of Mo containing enzymes (oxotransferases) catalyze the oxidation of organic substrates by oxo-transfer reactions that involve specific Mo[VI]=O units. These units are part of a common Mo-cofactor that invariably is found coordinated to a pterin-bound dithiolene ligand. The function of this "non-innocent" ligand at present is not understood and will be subject to our studies. Electron transfer in biological systems and the oxidation and reduction of various substrates in living organisms are of fundamental importance to life sustaining processes. Multi-electron transfer processes are less frequent in nature but are of equally great importance. Included among these are: The 4e- oxidation of 2H20 to 02 in photosynthesis, the 6e- reductions of N2 to ammonia in nitrogenase, and the 6e- reduction of sulfite to sulfide and of nitrite to ammonia in sulfite and nitrite reductases respectively. A general feature that appears to be associated with the sites involved in biological, multielectron redox processes, is a complex supermolecular structure that consists of bridged, redox active subunits. The factors that affect multielectron redox processes within such superstructures are not understood, and appropriate synthetic clusters that may be used as models are not readily available. This proposal is concerned with the synthesis and study of models for nitrogenase and sulfite reductase and of super-molecular assemblies that contain redox-active subunits. The effects of the bridging ligands between subunits, on the redox potentials and the competency of the assemblies to affect specific oxidations or reductions of substrate molecules, will be evaluated.