Spectroscopic and Magnetic Studies of Metalloprotein Active Sites

9316768所罗门许多金属酶表现出不同寻常的光谱特征，这些特征反映了新的电子结构，可以对催化做出重大贡献。本研究项目的重点是了解磁偶联双核非血红素铁锰簇酶活性位点的特殊电子和几何结构。氰菊酯、甲烷单加氧酶和核糖核苷酸还原酶具有FE（II）、FE（II）位点，分别结合、激活和还原O2，而紫色酸性磷酸酶在其混合价FE（II）、FE（III）状态下具有催化活性。这些蛋白的活性位点通常可以在Fe(III)Fe（III）、Fe(III)Fe（II）和Fe(II)Fe（II）态得到，并且这些氧化态都存在模型配合物。氧中间体或类似物现在可用于许多这些蛋白质和非血红素铁模型复合物在过氧和氧铁水平。所研究的锰氧簇酶包括锰过氧化氢酶、锰核糖核苷酸还原酶、锰取代铁核糖核苷酸还原酶和光系统II中的水氧化催化剂。同样，模型配合物可用于从Mn(II)Mn（II）到Mn(IV)Mn（IV）的所有生物相关氧化态。提出了一种光谱学方法，强调应用吸收、圆二色、磁圆二色和共振拉曼方法来研究这些酶和模型配合物的激发态，并利用变温变场磁圆二色来探测与桥接连接有关的基态亚能级分裂。这些光谱结果与配体场和自洽场x散射波计算相结合，确定了这些活性位点的电子结构。这些研究旨在确定与非血红素铁酶功能差异相关的活性位点几何和电子结构差异，确定双核非血红素铁酶和锰酶之间活性位点的异同，并了解与双氧活化和o -o键形成相关的金属-氧中间体和金属-氧键的电子结构。许多蛋白质和酶含有金属离子活性位点，它们在生物功能中起着关键作用。通常这些表现出不同寻常的光谱特征，反映了新的电子结构，可以对分析做出重大贡献。本研究项目的重点是了解磁偶联双核非血红素铁锰簇酶活性位点的异常电子和几何结构。这些团簇存在于光氰菊酯（可逆氧结合）、核糖核苷酸还原酶（DNA合成中将核糖核苷酸转化为脱氧核糖核苷酸）、甲烷单加氧酶（催化甲烷转化为甲醇）、过氧化氢酶（过氧化氢解毒）和光系统II中的水氧化催化剂（绿色植物产生氧气）中。这些研究旨在确定与非血红素铁酶的功能差异相关的活性位点几何和电子结构差异，确定相应的双核非血红素铁酶和锰酶之间活性位点的异同，以及了解参与双氧活化和O-O键形成的金属-氧中间体的电子结构。这项研究将为几何和电子结构对生物学功能的贡献提供基本的见解，并为设计和开发新的催化系统奠定基础。＊＊＊

9316768 Solomon Many metalloenzymes exhibit ususual spectral features which reflect novel electronic structures that can make significant contributions to catalysis. This research program focuses on understanding the unusal electronic and geometric structures of active sites in magnetically coupled binuclear non-heme iron and manganese cluster enzymes. Hemerythrin, methane monooxygenase and ribonucleotide reductase have FE(II)Fe(II) sites which bind, activate and reduce O2, respectively, while purple acid phosphatase is active in catalysis in its mixed valent Fe(II)Fe(III) state. The active sites in these proteins can generally be obtained in the Fe(III)Fe(III) , Fe(III)Fe(II) and Fe(II)Fe(II) states and model complexes exist for all of these oxidation states. Oxy- intermediates or analogues are now available for a number of these proteins and for non-heme iron model complexes at the peroxy and oxo-ferryl levels. The manganese-oxo cluster enzymes of interest include manganese catalase, manganese ribonucleotide reductase, manganese substituted iron ribonucleotide reductase and the water oxidation catalyst in Photosystem II. Again, model complexes are available for all the biologically relevant oxidation states from Mn(II)Mn(II) to Mn(IV)Mn(IV) . A spectroscopic approach is presented which emphasizes the application of absorption, circular dichroism,magnetic circular dichroism and resonance Raman methods to study the excited states in these enzymes and model complexes and variable temperature variable field magnetic circular dichroism to probe the ground state sublevel splittings which relate to the bridging ligation responsible for the coupling. The results from these spectroscopies are combined with ligand field and self consistent field-X-scattered wave calculations to determine the electronic structures of these active sites. These studies are directed toward defining active site geometric and electron structure differences which relate t o differences in function in the non-heme iron enzymes, determining active site similarities and differences between the binuclear non-heme iron and manganese enzymes, and understanding the electronic structures of the metal-oxy intermediatesand metal-oxo bonds as related to dioxygen activation and O-O bond formation. %%% Many proteins and enzymes contain metal ion active sites which play a key role in biological function. Often these exhibit ususual spectral features which reflect novel electronic structures that can make significant contributions to calalysis. This research program focuses on understanding the unusual electronic and geometric structures of active sites in magnetically coupled binuclear non-heme iron and manganese cluster enzymes. These clusters are found in hemerythrin (reversible oxygen binding), ribonucleotide reductase (conversion of ribonucleotides to deoxyribonucleotides in DNA synthesis), methane monooxygenase (catalytic conversion of methane to methanol), catalase (detoxification of peroxide), and the water oxidation catalyst in photosystem II (generation of oxygen by green plants). These studies are directed toward defining active site geometric and electronic structure differences which relate to differences in function in the non-heme iron enzymes, determining active site similarities and differences between the corresponding binuclear non-heme iron and manganese enzymes, and understanding the electronic structures of the metal-oxygen intermediates involved in dioxygen activation and O-O bond formation. This research will provide fundamental insight into geometric and electronic structural contributions to function in biology and lay the groundwork for the design and development of new catalytic systems. ***