The goal of this project is to prepare and characterize functional and spectroscopic models for the active sites of the two main metalloenzymes that process hydrogen, the [FeFe]- and [NiFe]-hydrogenases. Such models will provide mechanistic insights into these enzymes and will underpin other advances: (i) define the roles for reduced iron in biological systems, (ii) opportunities for combating diseases caused by organisms that utilize hydrogen in their metabolism, and (ii) lead to new reagents and catalysts for using hydrogen, relevant to the synthesis of many pharmaceuticals. The work focuses mainly on the [FeFe]-hydrogenases, exploiting advances in our modeling both the reduced and oxidized states of this enzyme. An emerging effort builds on a recent breakthrough relevant to the [NiFe]-hydrogenases, which are particularly widespread. Much of the work focuses on the mixed valence Hox state of [FeFe]-hydrogenases, beginning with a recent discovery that H2 is activated by a biomimetic Hox model. The key to this advance is the incorporation of the azadithiolate cofactor into the synthetic analogues. These functionally competent models will be characterized spectroscopically and through isotopical labeling. For the other direction of this enzyme's action - H2 production - we will examine the protonation of reduced biomimetic systems, elucidating factors that control the regiochemistry and redox of the hydrides. Finally, a building block approach is described in the assembly of biomimetic models for the [NiFe]-hydrogenases. Preliminary studies demonstrate the assembly and characterization of a nearly complete active site model. Overall the work promises to clarify the pathways by which nature uses and produces hydrogen. The biochemistry and the underlying inorganic chemistry are highly unusual. Many of these questions cannot be fully addressed with the protein due to the invisibility of hydrogen to crystallography and the presence of interfering chromophores. The work underpins new bioinorganic chemistry involving H2 and hydride ligands.
An H2-based metabolism supports the pathogen H. pylori, estimated to be responsible for 80-90% of all gastric and duodenal cancers. This bacterium infects half of the world's population and 50M Americans. Hydrogen is a constituent of the atmosphere in the human gut.
|Huynh, Mioy T; Wang, Wenguang; Rauchfuss, Thomas B et al. (2014) Computational investigation of [FeFe]-hydrogenase models: characterization of singly and doubly protonated intermediates and mechanistic insights. Inorg Chem 53:10301-11|
|Huynh, Mioy T; Schilter, David; Hammes-Schiffer, Sharon et al. (2014) Protonation of nickel-iron hydrogenase models proceeds after isomerization at nickel. J Am Chem Soc 136:12385-95|
|Schilter, David; Pelmenschikov, Vladimir; Wang, Hongxin et al. (2014) Synthesis and vibrational spectroscopy of (57)Fe-labeled models of [NiFe] hydrogenase: first direct observation of a nickel-iron interaction. Chem Commun (Camb) 50:13469-72|
|Kamali, Saeed; Wang, Hongxin; Mitra, Devrani et al. (2013) Observation of the Fe-CN and Fe-CO vibrations in the active site of [NiFe] hydrogenase by nuclear resonance vibrational spectroscopy. Angew Chem Int Ed Engl 52:724-8|
|Schilter, David; Nilges, Mark J; Chakrabarti, Mrinmoy et al. (2012) Mixed-valence nickel-iron dithiolate models of the [NiFe]-hydrogenase active site. Inorg Chem 51:2338-48|
|Pelmenschikov, Vladimir; Guo, Yisong; Wang, Hongxin et al. (2011) Fe-H/D stretching and bending modes in nuclear resonant vibrational, Raman and infrared spectroscopies: comparisons of density functional theory and experiment. Faraday Discuss 148:409-20; discussion 421-41|
|Barton, Bryan E; Olsen, Matthew T; Rauchfuss, Thomas B (2010) Artificial hydrogenases. Curr Opin Biotechnol 21:292-7|
|Galinato, Mary Grace I; Whaley, C Matthew; Lehnert, Nicolai (2010) Vibrational analysis of the model complex (mu-edt)[Fe(CO)(3)](2) and comparison to iron-only hydrogenase: the activation scale of hydrogenase model systems. Inorg Chem 49:3201-15|
|Barton, Bryan E; Rauchfuss, Thomas B (2010) Hydride-Containing Models for the Active Site of the Nickel-Iron Hydrogenases. J Am Chem Soc :|
|Whaley, C Matthew; Rauchfuss, Thomas B; Wilson, Scott R (2009) Coordination chemistry of [HFe(CN)(2)(CO)(3)](-) and its derivatives: toward a model for the iron subsite of the [NiFe]-hydrogenases. Inorg Chem 48:4462-9|
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