X-Ray Raman and Vibrational Mossbauer of Metalloproteins

描述(申请人提供)：我们的长期目标是更好 了解含有金属的酶的重要作用。在这份提案中， 我们关注的是同时含有铁和一种不同金属(镍、钼、 V)在活动现场。三个酶活性部位(NiFe氢酶、CO 脱氢酶和乙酰辅酶A合成酶)含有铁和镍的组合。这个 另一种酶，固氮酶，在MFe7S8簇的一端使用V或Mo。 尽管x射线衍射(或电子显微镜)技术取得了进步，但许多 关于分子和电子结构的问题需要解决。这个 催化机理仍然知之甚少。 将用扩展x射线研究镍中心的分子结构。 过氧化氢酶和乙二醛的吸收精细结构(EXAFS)分析 只包含CO氧化(C-簇)和ACS(A-簇)中心的样品 还将接受检查。尽管这些酶已经被 EXAFS，建议的样品和范围扩展的分析技术应该会产生 更多关于镍遗址的详细信息。 Ni和V位的电子结构将用x射线进行探测 共振拉曼光谱(XRRS或RIXS)。对这些光谱的分析将 揭示了Ni和V的氧化和自旋态在 条件多种多样。铁心和镍心振动态密度 将使用振动穆斯堡尔谱学进行研究。这种方法 将有助于确定重要的M-H和金属-衬底相互作用的位置。 将建造一台仪器，允许在校园内进行实验。 上述酶对维持我们的环境很重要。铁蛋白 在人类健康和疾病方面也起着关键作用。拟议的工作将加强 我们对铁生物化学的知识，以及在 开发将应用于广泛的生物无机物问题。

DESCRIPTION (provided by applicant): Our long-term goal is a better understanding of how important metal containing enzymes work. In this proposal, we focus on metalloenzymes that contain both Fe and a different metal (Ni, Mo, V) at the active site. Three of the enzyme active sites (NiFe hydrogenase, CO dehydrogenase, and acetyl-CoA synthase) contain combinations of Fe and Ni. The other enzyme, nitrogenase, employs V or Mo at one end of a MFe7S8 cluster. Despite progress by x-ray diffraction (or electron microscopy) techniques, many questions about the molecular and electronic structure need to be resolved. The catalytic mechanisms are still poorly understood. The molecular structure of the Ni sites will be studied using extended x-ray absorption fine structure (EXAFS) analysis of crystals of H2ase and CODH. Samples containing only the CO oxidation (C-cluster) and ACS (A-cluster) sites will also be examined. Although these enzymes have already been studied by EXAFS, the proposed samples and range-extended analysis techniques should yield more details about the Ni sites. The electronic structure of the Ni and V sites will be probed using x-ray resonance Raman spectroscopy (XRRS or RIXS). Analysis of these spectra will reveal the best description of the Ni and V oxidation and spin states under a variety of conditions. The Fe- and Ni-centered vibrational density of states will be studied using the vibrational Mossbauer spectroscopy. This approach will help identify the sites of important M-H and metal-substrate interactions. An instrument will be built to allow on-campus experiments. The above enzymes are important for maintaining our environment. Fe proteins also play key roles in human health and disease. The proposed work will enhance our knowledge of Fe biochemistry, and the spectroscopic techniques under development will have applications to a wide range of bioinorganic problems.