MODEL STUDIES OF HYDROPORPHYRIN-CONTAINING ENZYMES

这项研究计划的目标是开发一种 对结构、电子和机械原理的理解 含氢卟啉的酶的特性。这些催化剂可以 关键代谢过程中的重要步骤，包括无机 碳、氮、硫循环和许多主要能源 微生物的产生途径。该计划有三个 具体目标：(1)确定不同性别之间的显著差异 氢化卟啉、卟啉和氢化卟啉配合物的性质 其他四聚吡咯，(2)合成和表征 连结的Siroheme-Fe4S4活性中心的结构模型 亚硝酸盐和亚硫酸盐还原酶，以及(3)发展反应性 S甲基F430依赖的还原裂解模型 辅酶M转化为甲烷。人工合成的小分子类似物 酶活性部位和假体基团将用于这些 调查。第一个目标将通过测试 假设卟啉、氢卟啉、科林斯和其他 通过最佳的孔大小和范围来区分四个角色 在他们的建筑群中容易接近的孔大小，并且 取代基立体化学可以很容易地调节范围 可接近的孔大小。假说将通过检验来检验。 化学变化需要较大的金属离子半径变化。 Ni(II)四吡咯的配体结合/自旋态平衡 Ni(I)氧化态的可及性之间的相关性 以及分子的饱和水平和取代基立体化学 除其他外，还将研究氢卟啉大环。 第三个目标将通过探索 NiI(OEiBC)-，除F430外，唯一已报道的Ni(I)四吡咯。 反应的机理(S)将被确定。烷基- Ni(OEiBC)络合物将被合成并评估为 潜在的反应中间体。

The objective of this research program is to develop an understanding of the structural, electronic, and mechanistic features of hydroporphyrin-containing enzymes. These catalyze important steps in key metabolic processes including the inorganic carbon, nitrogen, and sulfur cycles and many of the main energy producing pathways of microorganisms. The program has three specific aims: (1) to determine the significant differences in the properties of the complexes of hydroporphyrins, porphyrins, and other tetrapyrroles, (2) to synthesize and characterize a structural model of the linked siroheme-Fe4S4 active site of nitrite and sulfite reductases, and (3) to develop a reactivity model for the F430 dependent reductive cleavage of S-methyl coenzyme M to methane. Synthetic, small molecule analogues of enzyme active sites and prosthetic groups will be used in these investigations. The first aim will be addressed by testing the hypotheses that porphyrin, hydroporphyrins, corrins, and other tetrapyrroles are distinguished by the optimal hole size and range of hole sizes readily accessible in their complexes and that the substituent stereochemistry can modulate the range of readily accessible hole sizes. The hypotheses will be tested by examining chemical changes that require large changes in metal ion radius. Ligand binding/spin state equilibria of Ni(II) tetrapyrroles and the correlation between the accessibility of the Ni(I) oxidation state and the saturation level and substituent stereochemistry of the hydroporphyrin macrocycle will be investigated, among others. The third aim will be achieved by exploring the reactions of NiI(OEiBC)-, the only reported Ni(I) tetrapyrrole except for F430. The mechanism(s) of the reactions will be determined. Alkyl- Ni(OEiBC) complexes will be synthesized and evaluated as potential reaction intermediates.