NI K-EDGE AND EXAFS STUDIES ON THE CATALYTICALLY RELEVANT NI(I) AND NI(III) FORM

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 产甲烷菌每年产生约10亿吨甲烷，这是一种清洁的可再生能源，但作为一种强有力的温室气体，也会对环境造成危害。甲基COM还原酶(MCR)催化辅酶B(CoB)和甲基辅酶M转化为甲烷和COMB(一种杂二硫化物)的最终产甲烷步骤。该酶含有一个镍卟啉F430活性中心，该活性中心在Ni(I)(D9)氧化态下具有活性。对MCR进行了广泛的光谱和理论研究，表明催化循环涉及有机金属NiIII-Me物种。然而，无论是Ni(I)，还是Ni(III)-Me形式都没有得到结晶学表征。虽然非活性Ni(II)晶型的晶体结构已被解决，但阐明Ni(I)和Ni(III)晶型的几何结构和电子结构是理解甲烷生成催化机理的关键。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Methanogens produce approximately one billion tonnes of methane every year, which is a clean source of renewable energy, but also poses environmental hazards as a potent greenhouse gas. Methyl CoM reductase (MCR) catalyzes the terminal step of methanogenesis in which coenzyme B(CoB) and methyl coenzyme M are converted to methane and CoMS-SCoB (a heterodisulfide). The enzyme contains a Ni porphinoid F430 active site, which is active in the Ni(I) (d9) oxidation state. Extensive spectroscopic and theoretical studies have been performed on MCR, which indicate that the catalytic cycle involves an organometallic NiIII-Me species. However, neither the Ni(I), nor the Ni(III)-Me forms have been crystallographically characterized. Although, crystal structures of the inactive Ni(II) forms have been solved, elucidating the geometric and electronic structures of the Ni(I) and Ni(III) forms is key in understanding the catalytic mechanism of methane formation.