Molecular Models for H2-Activating Metalloenzymes

这个无机、生物无机和有机金属化学项目的奖项支持德克萨斯农工大学化学系Marcetta Darensbourg博士对金属酶的研究。研究的重点是（NiFe）氢化酶的反应化学，一种促进二氢的形成、固定和感知的酶。脱硫弧菌氢化酶的活性位点是异双核的（Fe, Ni），铁中心似乎与氰基和羰基有关。在这项工作中，已知的有机金属阴离子CpFe(CN)2(CO)，其中Fe = Fe(I), Fe(II)，将研究它们在Cp取代基上由氢键或溶剂相互作用引起的电子密度变化的信号能力。振动光谱学将用于监测电子密度随氧化还原和酶活性水平的变化。此外，新设计的二硫代酸盐配体将用于将镍配合物配位到铁单元上，这可能作为酶的结构模型。关于催化过程的假设是，要么铁单元通过吸电子铁位点提供稳定性，通过硫代酸盐介导电荷，从而使催化活性Ni(I)易于接近；或者二氢生成催化涉及铁（II）位点，二硫代酸镍作为双齿配体，可通过氧化还原状态或连接的变化进行电子调节。氢化酶发挥重要的生物功能，为细胞提供能量。这些酶被发现在活性反应位点含有两种金属，铁和镍，但这些金属如何在反应中协同作用尚不清楚。许多过去的研究已经调查了镍的作用，但这项研究将阐明铁的作用，以及铁-镍的组合。该结果也可能与功能尚不清楚的混合金属工业催化剂的功能有关。

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.