Mossbauer Spectroscopy on Nitrogenase Components

9406224 Munck Mossbauer和EPR光谱将用于研究各种铁硫蛋白质和模拟这些蛋白质活性部位的合成络合物。拟议研究的主要焦点将是固氮酶，特别强调催化反应的中间体的特征。对于这些研究，可以获得含有一种富含穆斯堡尔同位素57Fe的簇类型(辅因子中心或P-簇)的蛋白质，而另一种簇类型包含穆斯堡尔沉默的56Fe。这种蛋白质的可获得性将大大促进数据分析；此外，它将使我们能够更详细地探索这两个簇的电子结构。还建议对一氧化碳脱氢酶和两种氢酶进行研究。其中一个氢酶含有所谓的H-簇，到目前为止，还没有在任何研究的系统中确定其化学计量比。最后，将继续对蛋白质和合成化合物中存在的3Fe团簇进行理论和实验研究。生物系统每年将超过1000万吨的大气氮转化为氨，然后将氨结合到其他细胞成分中。由于这一过程是农业的基础，许多生物化学家、生物物理学家和遗传学家都致力于从分子水平上理解这一过程。本实验室的研究为阐明固氮酶金属中心的结构做出了重大贡献。虽然我们过去的研究已经解决了该酶中两个新的金属簇的结构方面，但未来的活动将主要针对了解这一过程的机制，即在定义了所涉及的结构后，我们希望阐明在固氮过程中发生的一系列事件。此外，我们希望为无机化学家设计模拟生物过程的催化剂提供结构信息。我们与固氮酶的斗争涉及到补充性研究，这些研究导致了新的团簇的发现，并从根本上对磁化学有了新的见解。该提案研究将涉及固氮酶的生物化学以及各种其他相关蛋白质的研究。我们对生物化合物的研究将得到适当的化学模型和理论模型的研究的补充。***

9406224 Munck Mossbauer and EPR spectroscopy will be used to study a variety of iron-sulfur proteins and synthetic complexes that mimic the active sites of these proteins. The major focus of the proposed studies will be nitrogenase, with particular emphasis on characterizing intermediates of the catalytic reaction. For these studies protein is available that contains one cluster type (either the cofactor centers or the P-clusters) enriched with the Mossbauer isotope 57Fe whereas the other cluster type contains the Mossbauer-silent 56Fe. The availability of such protein will facilitate the data analyses substantially; moreover, it will allow us to probe the electronic structure of both clusters in considerably more detail. It is also proposed to study carbonmonoxide dehydrogenase and two types of hydrogenases. One of the hydrogenases contains the so-called H- cluster, the stoichiometry of which has not yet been determined in any system studied thus far. Finally, theoretical and experimental studies of 3Fe clusters that occur in proteins and synthetic compounds will be continued. %%% The biological system converts annually in excess of 10 million tons of atmospheric nitrogen into ammonia, which is subsequently incorporated into other cell constituents. Since this process is fundamental to agriculture, many biochemists, biophysicists and geneticists have directed much effort to understand this process on the molecular level. The research of our laboratory has provided a major contribution to the clarification of the structure of the metal centers of nitrogenase. While our past research has addressed the structural aspects of two novel metal clusters in this enzyme, future activities will be directed mostly towards understanding the mechanism of the process, i.e. after having defined the structure involved we wish to elucidate the sequential events occurring during nitrogen fixation. Moreover, we wish to provide structural information to inorganic chemists for the design of catalysts that mimic the biological process. Our struggles with nitrogenase have involved complementary studies that lead to the discovery of new clusters and to fundamentally new insights into magnetochemistry. The proposal studies will address the biochemistry of nitrogenase as well as research of a variety of other related proteins. Our studies of the biological compounds will be complemented by studies of suitable chemical models and theoretical modelling. ***