MODEL STUDIES OF HYDROPORPHYRIN-CONTAINING ENZYMES

该研究项目的目标是开发一种 了解结构，电子和机械 含氢卟啉酶的特征。 这些催化剂 关键代谢过程中的重要步骤，包括无机 碳、氮和硫的循环以及许多主要的能源 产生微生物的途径。 该计划有三个 具体目标：（1）确定 氢化卟啉、卟啉和 其他四吡咯类化合物;（2）合成并表征了一种 的连接siroheme-Fe_4S_4活性中心的结构模型 亚硝酸盐和亚硫酸盐还原酶，和（3）产生反应性 F430依赖的S-甲基还原裂解模型 辅酶M转化为甲烷。 合成的小分子类似物 酶活性位点和辅基将用于这些 调查事务所 第一个目标将通过测试 假设卟啉、氢化卟啉、咕啉和其他 四吡咯通过最佳孔尺寸和范围来区分 的孔大小容易在他们的复合体， 取代基立体化学可以容易地调节 可访问的孔大小。 这些假设将通过检查 化学变化需要金属离子半径的巨大变化。 Ni（II）四吡咯的配体结合/自旋态平衡及 Ni（I）氧化态的可及性之间的关系 和饱和度和取代基立体化学的 将研究氢化卟啉大环化合物等。 第三个目标将通过探索以下反应来实现： NiI（OEiBC）-，除了F430之外唯一报道的Ni（I）四吡咯。 将确定反应的机制。 烷基 Ni（OEiBC）络合物将被合成并评价为 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.