Mossbauer Spectroscopy of Nitrogenase Components

本项目由分子和细胞生物科学系的分子生物物理学和化学系的无机、生物无机和有机金属化学项目共同资助，将利用~(57)Fe穆斯堡尔谱、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化合物的活性中心。尽管[2Fe-2S]蛋白质已经被研究了30多年，但关于它们的电子结构的许多问题仍然没有答案。其中包括对观测到的EPR g值和57Fe磁性超精细相互作用的修正。此外，正如本实验室最近显示的那样，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。这个项目将为包括Rieske蛋白质在内的各种[2Fe-2S]铁氧还蛋白解决这些问题。将尝试用镓和铁重建铁-硫中心，以获得含有[GaFe-2S]簇的铁氧还蛋白；这种铁氧还蛋白将允许确定目前无法直接获得的许多参数。含硫闪石的铁络合物具有与生物固氮系统的辅因子相似的特性。因此，二酮基铁络合物已被证明含有活化的氮，理论研究表明，二酮基铁配体的电子性质与生物体系中发现的硫基非常相似。我们将研究一系列氧化态从Fe(III)到Fe(0)的含铁双酮配合物的结构特征。在生物系统中，氮和氢被认为与铁-钼辅助因子的三角-锥体铁中心结合，因此将对现有的与氮、氢和氨结合的双酮配合物进行研究。对CoA合成酶/一氧化碳脱氢酶的A-簇的研究也将继续进行。这一项目将使人们对铁-硫簇和合成的与固氮有关的络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簇和簇组合的发现，开创了全细胞穆斯堡尔研究的先河，并在化学文献中引入了双重交换。这项研究介于化学、物理、生物化学和生物学之间，因此为学生提供了一个独特的机会来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.