Mossbauer Spectroscopy of Nitrogenase Components

该项目由分子与细胞生物科学部分子生物物理学和化学部无机、生物无机和有机金属化学项目共同资助，将利用57Fe穆斯堡尔光谱、电子顺磁共振（EPR）和密度泛函理论研究含铁蛋白质和合成模型配合物的活性位点。虽然[2Fe-2S]蛋白已经被研究了30多年，但关于其电子结构的许多问题仍未得到解答。这包括对观测到的EPR g值和57Fe磁超精细相互作用的修正。此外，正如最近在这个实验室所显示的，反对称交换可以对这些蛋白质的光谱特征产生深远的影响。该项目将解决包括Rieske蛋白在内的各种[2Fe-2S]铁氧化还原蛋白的这些问题。将尝试用镓和铁重建铁硫中心，以获得含[GaFe-2S]簇的铁氧化还原蛋白；这种铁氧化还原蛋白将允许确定许多目前无法直接获得的参数。含二氯胺酸盐的铁配合物具有类似生物固氮系统辅助因子的特性。因此，双氯胺酸铁配合物已被证明含有活化的二氮，理论研究表明，双氯胺酸配体的电子性质与生物系统中发现的硫基非常相似。将研究一系列结构表征的含铁氧化态从Fe（III）到Fe(0)的二氯酸盐配合物。在生物系统中，二氮和氢被认为与铁钼辅助因子的三角-锥体铁位点结合，因此将对现有的与氮、氢化物和氨结合的二氯盐配合物进行研究。对辅酶a合成酶/一氧化碳脱氢酶a -簇的研究也将继续进行。该项目将导致对铁硫团簇和与固氮相关的合成配合物的磁性和电子结构有更基本的了解。PI先前的研究导致了新的铁硫团簇和团簇组合的发现，开创了全细胞的穆斯堡尔研究，并将双交换引入化学文献。这项研究是在化学，物理，生物化学和生物学的界面，因此为学生提供了一个独特的机会，以发展跨学科的研究视角。

In this project, jointly funded by Molecular Biophysics in the Division of Molecular and Cellular Biosciences and the Inorganic, Bioinorganic and Organometallic Chemistry Program in the Chemistry Division, 57Fe Mossbauer spectroscopy, Electron Paramagnetic Resonance (EPR) and density functional theory will be used to study the active sites of iron-containing proteins and synthetic model complexes. Although [2Fe-2S] proteins have been investigated for more than 30 years, many issues regarding their electronic structure have remained unanswered. These include corrections to the observed EPR g-values and 57Fe magnetic hyperfine interactions. Moreover, as shown recently in this laboratory antisymmetric exchange can have a profound influence on the spectroscopic signatures of these proteins. This project will address these questions for a variety of [2Fe-2S] ferredoxins, including Rieske proteins. Attempts will be made to reconstitute the iron-sulfur centers with gallium and iron to obtain ferredoxins containing [GaFe-2S] clusters; such ferredoxins would allow determination of many parameters currently not directly accessible. Iron complexes involving diketiminates have properties resembling features of the cofactor of the biological nitrogen fixation system. Thus, diketiminate iron complexes have been shown to contain activated dinitrogen, and theoretical studies have shown that electronic properties of the diketiminate ligand are quite similar to those of sulfido groups found in the biological system. A series of structurally characterized diketiminate complexes containing iron in oxidation states ranging from Fe(III) to Fe(0) will be studied. In the biological system, dinitrogen and hydrogen are thought to bind to trigonal-pyramidal iron sites of the iron-molybdenum cofactor, and therefore studies of existing diketiminate complexes with bound nitrogen, hydride and ammonia will be carried out. Research on the A-clusters of CoA synthase/carbon monoxide dehydrogenase will also be continued.This project will lead to a more fundamental understanding of the magnetic properties and electronic structure of iron-sulfur clusters and synthetic complexes relevant for nitrogen fixation. The PI's prior research has led to the discovery of new iron sulfur clusters and cluster assemblies, pioneering Mossbauer studies of whole cells, and the introduction of double exchange into the chemical literature. This research is at the interface of chemistry, physics, biochemistry, and biology and thus offers a unique opportunity for students to develop an interdisciplinary perspective in research.