Molecular Models for H2-Activating Metalloenzymes

无机化学、生物无机化学和金属有机化学项目的这一奖项支持德克萨斯农工大学化学系的Marcetta Darensburg博士对金属酶的研究。研究的重点是(NiFe)氢酶的反应化学反应，这是一种促进二氢的形成、固定和感觉的酶。该酶的活性中心为异双核(Fe，Ni)，铁中心似乎与氰基和羰基有关。在这项工作中，将研究已知的有机金属阴离子CPFe(CN)2(CO)，其中Fe=Fe(I)，Fe(II)，因为它们能够发出由氢键或溶剂相互作用引起的CP取代基上电子密度变化的信号。振动光谱将被用来监测伴随着氧化还原和酶活性水平的电子密度变化。此外，新设计的二硫酸盐配体将被用来将镍配合物配位到铁单元，这可能会作为酶的结构模型。关于催化过程的假说是，要么铁单元通过一个吸电子的铁单元提供稳定，该铁单元通过硫酸盐调节电荷，从而使催化活性的Ni(I)更容易获得；或者二氢生成催化涉及Fe(II)中心，二硫代镍作为双齿配体，可以通过改变氧化还原状态或连接来进行电子调节。氢酶具有重要的生物功能，为细胞提供能量。这些酶已被发现在活性反应部位含有铁和镍两种金属，但这些金属如何在反应中协同作用尚不清楚。过去的许多研究都研究了镍的作用，但这项研究将阐明铁的作用，以及铁-镍结合的作用。这一结果也可能与混合金属工业催化剂的功能有关，这些催化剂的功能尚不清楚。

This award in the Inorganic, Bioinorganic, and Organometallic Chemistry Program supports research on metalloenzymes by Dr. Marcetta Darensbourg of the Chemistry Department, Texas A&M University. The focus of the investigation is the reaction chemistry of (NiFe)hydrogenase, an enzyme that promotes the formation, fixation, and sensing of dihydrogen. The active site of the Desulfovibrio gigas hydrogenase is heterobinuclear (Fe, Ni) and the iron center appears to be associated with cyano and carbonyl groups. In this work, the known organometallic anions CpFe(CN)2(CO) where Fe = Fe(I), Fe(II) will be studied for their ability to signal electron density changes at Cp substitutents caused by hydrogen-bonding or solvent interaction. Vibrational spectroscopy will be used to monitor the electron density changes accompanying redox and enzyme activity levels. In addition, newly designed dithiolate ligands will be used to coordinate nickel complexes to the iron unit which may serve as a structural model for the enzyme. The hypothesis concerning the catalysis process is that either the iron unit provides stabilization via an electron-withdrawing iron site that mediates charge through the thiolates, thus easing accessibility to catalytically active Ni(I); or the dihydrogen production catalysis involves the Fe(II) site, with the nickel dithiolate serving as a bidentate ligand that is electronically tunable by changes in redox state or ligation. Hydrogenase enzymes perform important biological functions that provide energy to cells. These enzymes have been found to contain two metals, iron and nickel, at the active reaction site, but how these metals cooperate in the reaction is unknown. Many past studies have investigated the role of nickel, but this research will elucidate the role of iron, and of the iron-nickel combination. The results may also be relevant to the functioning of mixed metal industrial catalysts whose functioning is not well understood.