SPECTROSCOPIC STUDIES OF MOLYBDOENZYMES AND MODELS

描述：(申请人摘要)含单核蝶呤 钼酶存在于真核生物和原核生物中， 催化简单氧原子转移反应的功能(二甲基亚砜 还原酶和亚硫酸盐氧化酶家族)和氧化羟化 醛和杂环底物(黄嘌呤氧化酶家族)，长 拟议研究的长期目标是了解 几何和电子结构之间的三个主要特征 含蝶呤的钼酶家族。这一点很重要，因为它是 这些活性中心的独特电子结构使特定的 对它们的反应性的贡献，从而确定它们在催化中的作用。 最近的X射线结晶学研究提供了详细的结构 定义起点的每个主要家族的酶的信息 用于将几何结构与酶功能相关联。这些 结晶学结果允许提出以下假设 第四：i)吡喃喋呤二硫烯键C=C的饱和度， SPP轨道的取向和S…S的成键性质是 决定氰基蝶呤二硫杂环戊烯能力的关键因素 与Mo中心的氧化还原活性轨道(Dxy)相互作用，II) 吡喃喋呤吡嗪环的氧化态对电子密度的调节 在二硫杂环内，影响SPP-Mo DXY轨道相互作用 三)氧供体配体主导钼配位体领域，导致 与二氧杂环连接的成键描述截然不同 单氧连接和IV)在黄嘌呤氧化酶家族中的存在 Mo=S基团顺式到Mo=O基团对电子的影响很大 末端硫化物的结构，调节其有效性 电性/亲核性。拟议的研究在很大程度上依赖于详细的 相关模型化合物和含蝶呤钼的光谱研究 酵素。研究计划将采用综合光谱方法。 利用低温电子吸收、磁圆二向色性 和共振拉曼光谱，以将光谱特征与 几何结构并最终决定电子结构 对反应性的贡献。拟议研究的结果应该是 导致对选通电子发展详细的机械洞察力 氧原子转移与C-H键的氧化活化 通过[MoOS]单元进行羟基化。

DESCRIPTION: (applicant's abstract) Mononuclear pterin-containing molybdenum enzymes are found in eucaryotic and procaryotic organisms and function to catalyze simple oxo-atom transfer reactions (dimethylsulfoxide reductase and sulfite oxidase families) and the oxidative hydroxylation of aldehyde and heterocyclic substrates (xanthine oxidase family), The long term objectives of the proposed research are to understand the relationship between geometric and electronic structural features of the three main pterin-containing Mo enzyme families. This is important since it is the unique electronic structures of these active sites which make specific contributions to their reactivity thus defining their role in catalysis. Recent X-ray crystallographic studies have provided detailed structural information for enzymes from each main family defining the starting point for correlating geometric structure with enzyme function. These crystallographic results have allowed for the following hypotheses to be put forth: i) the degree of saturation of the pyranopterin dithiolene C=C bond, orientation of Spp orbitals and the degree of S...S bonding character are critical factors in determining how the cyanopterin dithiolene is capable of interacting with the redox active orbital (dxy) on the Mo center, ii) the oxidation state of the pyranopterin pyrazine ring modulates electron density within the dithiolene chelate, affecting the Spp-Mo dxy orbital interaction iii) the oxo donor ligands dominate the Mo ligand field resulting in radically different bonding descriptions for dioxo ligation compared to monooxo ligation and iv) in the xanthine oxidase enzyme family the presence of a Mo=S group cis to a Mo=O group substantially affects the electronic structure of the terminal sulfido , modulating its effective electro/nucleophilicity. The proposed research relies heavily on detailed spectroscopic studies of relevant model compounds and pterin-containing Mo enzymes. The research plan will employ a combined spectroscopic approach utilizing low temperature electronic absorption, magnetic circular dichroism and resonance Raman spectroscopies to correlate spectroscopic features with geometric structure and eventually determine electronic structure contributions to reactivity. The results of the proposed research should lead to developing detailed mechanistic insight into gated electron transfer, oxygen atom transfer and the activation of C-H bonds for oxidative hydroxylation by [MoOS] units.