IRON AND MOLYBDENUM COMPLEXES: ENZYME ACTIVE SITES

这项研究计划涉及到合成，结构， 特定铁和钼的光谱和反应性性质 复合体。将合成新的Fe/S团簇，有望 用作某些3Fe中Fe3S3或Fe3S4位的合成类似物 这些蛋白质包括乌头酸酶、D.gias FdII、A、Vinelandii fDi等 新的Fe/S团簇将从[Fe6S6L6]2-，3-团簇中获得 最近在我们的实验室中发现并表征了它。后者将 被各种末端配体完全表征(L)及其 结构将由X射线结晶学确定。的目标之一 本方案是以Fe：Mo：S的比例合成Fe/Mo/S骨料 接近6：1：8或9。这一比例目前被接受为可能的比例 对于固氮酶中的Fe/Mo/S位。一款成功的模拟软件 固氮酶活性部位应允许理解催化 在生物系统中将氮素转化(还原)为氨。 这一反应也可能有助于我们理解Small 一般情况下，通过含有金属的催化中心来激活分子。 这项建议的另一个具体目标是综合和完成 混合末端铁氧还蛋白活性中心类似物的表征 [Fe4S4LnLprime4-n]2-，3-和[Fe2S2LnLprime4-n]-2，-3 L=RS-、RO-等非负单齿配体和L‘-双齿配体 或具有0个或N个给体原子的三齿酶螯合配体。这些集群是 有望作为固氮酶中P-簇的模型和 乌头酸酶中有柠檬酸结合的Fe4S4簇。试图稳定[Fe4S4]3+ 将通过替换1或2个生物型配体来制备核心 (PHS-，Ph-)来自已知的合成类似物与“有机金属” 配体C5H5-及其衍生物。这些新的混合末端配体簇是 预计会发生双电子氧化还原反应，因此可能会 对于减少小底物分子很重要。

This research proposal is concerned with the synthesis, structures, spectroscopic and reactivity properties of specific iron and molybdenum complexes. New Fe/S clusters will be synthesized, that are expected to serve as synthetic analogues of the Fe3S3 or Fe3S4 sites in certain 3Fe proteins such as aconitase, D. gigas FdII, A, vinelandii FdI, etc. These new Fe/S clusters will be obtained from the [Fe6S6L6]2-,3- clusters recently discovered and characterized in our laboratories. The latter will be completely characterized with various terminal ligands (L) and their structures will be determined by X-ray crystallography. One of the aims of this proposal is to synthesize Fe/Mo/S aggregates with a Fe:Mo:S ratio approaching 6:1:8 or 9. This ratio is presently accepted as possible ratio for the Fe/Mo/S site in nitrogenase. A successful analog for the nitrogenase active site should allow for an understanding of the catalytic conversion (reduction) of dinitrogen to ammonia in biological systems. This reaction also is potentially useful for our understanding of small molecule activation by catalytic metal containing sites in general. Another specific goal of this proposal is the synthesis and complete characterization of mixed-terminal ligand ferredoxin active site analog complexes such as [Fe4S4LnLprime4-n]2-,3- and [Fe2S2LnLprime4-n]-2,-3 with L = RS-, RO- and other uninegative monodentate ligands and L' - bidentate or tridentase chelate ligands with 0 or N donor atoms. These clusters are expected to serve as models for the P-clusters in nitrogenase and the citrate bound Fe4S4 cluster in aconitase. Attempts to stabilize [Fe4S4]3+ cores will be made by replacing 1 or 2 of the biological type ligands (PhS-, Ph0-) from known synthetic analogues with the "organometallic" ligand C5H5- and derivatives. These new mixed terminal ligand clusters are expected to undergo two-electron redox reactions and as such may be important for the reduction of small substrate molecules.