Spectroscopic Definition of Electronic Structure and Contributions to Reactivity in Binuclear Non-Heme Iron and Manganese Enzymes

双核非血红素铁和锰酶电子结构的光谱定义及其对反应性的贡献

• 批准号: 9816051
• 负责人: Edward Solomon
• 金额: $ 71万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-03-01 至 2004-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9816051&HistoricalAwards=false
• 关键词: Spectroscopic; Definition; Electronic; Structure; Contributions

SolomonMCB 98160511. TechnicalBinuclear non-heme iron active sites are present in a wide variety of proteins and enzymes, which perform different biological functions.These include oxygen binding, activation for hydroxylation, oxidation, desaturation and phosphate ester hydrolysis. All react with dioxygen from the binuclear ferrous state except the purple acid phosphatases, which are active at the mixed valent level. Crystal structures are now available for at least one oxidation state of each enzyme and define structural differences, which could relate to differences in reactivity. Peroxo and high valent oxo intermediates have been trapped for several of these enzymes and a number of relevant model systems are now available. Binuclear manganese sites are present in manganese catalase and manganese ribonucleotide reductase which are thought to have similar m-oxo, m-carboxylato bridged structures to the binuclear non-heme iron enzymes, and a Mn202 unit appears to be present in the tetra manganese cluster of the OEC. An excited state spectroscopic approach employing absorption, circular dichroism, magnetic circular dichroism and resonance Raman spectroscopies to define the excited states, variable temperature variable field magnetic circular dichroism analyzed using an exchange plus zero field splitting Hamiltonian to probe the ground state and electronic structure calculations is being utilized to study these proteins and relevant model complexes. These studies are directed toward obtaining detailed insight into: electronic and geometric structural contributions to the reactivity of these sites, geometric and electronic structural differences which relate to differences in function, the electronic structure of oxygen intermediates which promote the formation of high valent bridging oxo intermediates and the properties of these intermediates which contribute to reactivity, the relation of the binuclear manganese enzymes to the binuclear non-heme iron enzymes, and the properties of the Mn202 unit and interactions between these units which promote 0-0 bond formation.2 Non-TechnicalBinuclear non-heme iron active sites are present in a wide variety of proteins and enzymes, which perform different biological functions. These include oxygen binding, activation for hydroxylation, oxidation, desaturation and phosphate ester hydrolysis. Binuclear mangnese sites are present in enzymes which are involved in peroxide disproportionation and ribonucleotide reduction, and are thought to have similar structures to the binuclear non-heme iron enzymes. A related tetranuclear mangnese cluster is present in the oxygen-evolving center in photosynthesis. Detailed chemical and spectroscopic studies of these protein active sites, intermediates in their reactions with dioxygen and related small molecule inorganic complexes which model these binuclear sites are presented. These studies should contribute significantly toward defining general structure/function correlations for dioxygen binding and activation by binuclear non-heme iron enzymes, their relation to binuclear manganese enzymes and factors which contribute to dioxygen activation versus 0-O bond formation. The enzymes studied are important in catalytic processes (alkane oxidation technology, etc.), biotechnology (oxidoreductases, etc.), environmental regulation (CH4, etc.), oxygen evolution, detoxification, and DNA and fatty acid biosynthesis. Further, the spectroscopic methodology developed as part of this study has applications in understanding the structures and reactivities of a variety of important classes of metal sites in biology and catalysis.

SolomonMCB 98160511技术上，双核非血红素铁活性部位存在于多种蛋白质和酶中，它们执行不同的生物学功能，包括氧结合、羟化活化、氧化、脱饱和和磷酸酯水解。除了紫色酸性磷酸酶外，所有的酶都与来自双核亚铁状态的氧气反应，紫色酸性磷酸酶在混合价水平上是活跃的。现在可以获得每种酶至少一种氧化状态的晶体结构，并定义结构差异，这可能与反应活性的差异有关。过氧基和高价氧基中间体已经被捕获到其中的几种酶上，现在已经有了一些相关的模型系统。在锰过氧化氢酶和锰核苷酸还原酶中存在双核锰位点，这两种酶被认为具有与双核非血红素铁酶相似的间氧、间羧基桥联结构，并且在OEC的四重锰簇中似乎存在一个Mn202单位。用吸收光谱、圆二色谱、磁圆二色谱和共振拉曼光谱确定了激发态，用交换加零场分裂哈密顿量探测基态和电子结构计算分析了变温变场磁圆二色谱，并对这些蛋白质及其模型化合物进行了研究。这些研究旨在详细了解：电子和几何结构对这些位置的反应性的贡献，与功能差异有关的几何和电子结构差异，促进高价桥氧中间体形成的氧中间体的电子结构和有助于反应的中间体的性质，双核锰酶与双核非血红素铁酶的关系，以及Mn202单元的性质和这些单元之间促进0-0键形成的相互作用。2非技术性双核非血红素铁活性中心存在于各种具有不同生物功能的蛋白质和酶中。这些过程包括氧结合、羟化活化、氧化、脱饱和度和磷酸酯水解。双核甘露糖酶存在于参与过氧化氢歧化和核苷酸还原的酶中，被认为具有与双核非血红素铁酶相似的结构。在光合作用的放氧中心存在一个相关的四核甘露糖簇。详细的化学和光谱研究了这些蛋白质的活性中心、它们与氧气反应的中间体以及模拟这些双核中心的相关小分子无机络合物。这些研究将有助于确定双核非血红素铁酶与氧结合和激活的一般结构/功能相关性，它们与双核锰酶的关系，以及有助于氧激活与O-O键形成的因素。所研究的酶在催化过程(烷烃氧化技术等)、生物技术(氧化还原酶等)、环境调节(CH4等)、放氧、解毒以及DNA和脂肪酸的生物合成中具有重要作用。此外，作为这项研究的一部分开发的光谱方法在了解生物和催化中各种重要金属中心的结构和反应活性方面有应用。