Mossbauer Spectroscopy of Nitrogenase Components

穆斯堡尔光谱、电子顺磁共振（EPR）和磁化学将用于研究各种含铁酶、电子转移蛋白和合成模型配合物的活性位点。待研究的体系包括氮酶、氢化酶以及2Fe-2S铁氧化还原蛋白。对于氮酶，研究的重点将是进一步阐明p -簇和FeMo辅因子中心的电子结构。这些研究将包括使用MoFe蛋白的同位素杂交，其中两个簇中的一个被选择性地富集了57-Fe穆斯堡尔同位素。对相关铁蛋白的研究将继续进行，特别强调探索新发现的全铁形式的生物学相关性。除了表征全铁[4Fe-4S]团簇的电子结构外，还将研究迄今尚未用穆斯堡尔光谱表征的[2Fe-2S]和[3Fe-4S]团簇的全铁态。对氢化酶的研究主要集中在[NiFe]氢化酶的NiFe位点的性质和纯铁氢化酶的h簇（6个铁原子）上。这些实验研究将得到理论工作的补充，以解决h -团簇的特殊性质。穆斯堡尔光谱与电子顺磁共振结合使用是研究多种蛋白质和酶中含铁团簇的有力工具。这两种技术经常被用来发现生物系统中存在的新结构，或描述新的磁化学性质。该项目旨在获得对目前处于生物无机化学前沿的簇的电子特性的新见解。待研究的簇包括将大气氮固定到氨的生物系统中含钼和含铁蛋白质中的两个新结构。这两种技术还将应用于研究微生物酶中涉及氢的摄取或生产的两种新型簇组装。这些研究的目的是阐明这些酶的催化机制，并表征金属中心的磁化学性质。

MunckMCB 9904421Mossbauer spectroscopy, Electron Paramagnetic Resonance (EPR) and magnetochemistry will be used to study the active sites of a variety of iron-containing enzymes, electron transfer proteins, and synthetic model complexes. The systems to be studied include nitrogenase, hydrogenases as well as 2Fe-2S ferredoxins. For nitrogenase, the studies will focus on further clarifying the electronic structure of the P-clusters and the FeMo cofactor centers. These studies will include the use of isotopic hybrids of MoFe protein for which one of the two clusters is selectively enriched with the 57-Fe Mossbauer isotope. Studies of the associated Fe-protein will be continued with particular emphasis on exploring the biological relevance of the newly discovered all-ferrous form. In addition to characterizing the electronic structure of the all-ferrous [4Fe-4S] clusters, the all-ferrous states of [2Fe-2S] and [3Fe-4S] clusters, hitherto uncharacterized with Mossbauer spectroscopy, will be investigated. The studies of hydrogenases will focus on the properties of the NiFe site of [NiFe] hydrogenases and on the H-cluster (6 iron atoms) of Fe-only hydrogenases. These experimental studies will be complemented by theoretical work that addresses the peculiar properties of the H-cluster.Mossbauer spectroscopy used in combination with electron paramagnetic resonance is a very powerful tool to study iron-containing clusters found in a variety of proteins and enzymes. The two techniques have frequently been used to discover new structures present in biological systems, or delineate novel magnetochemical properties. This project is designed to obtain new insight into the electronic properties of clusters which are currently at the forefront of bio-inorganic chemistry. The clusters to be studied include two novel structures in the molybdenum and iron containing protein of the biological system that fixes atmospheric nitrogen to ammonia. The two techniques will also be applied to study two novel cluster assemblies in microbial enzymes involved in the uptake or production of hydrogen. The goal of these studies is to elucidate the catalytic mechanisms of these enzymes and to characterize the magnetochemical properties of the metal centers.