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.
|Pelmenschikov, Vladimir; Birrell, James A; Pham, Cindy C et al. (2017) Reaction Coordinate Leading to H2 Production in [FeFe]-Hydrogenase Identified by Nuclear Resonance Vibrational Spectroscopy and Density Functional Theory. J Am Chem Soc 139:16894-16902|
|Yu, Xin; Tung, Chen-Ho; Wang, Wenguang et al. (2017) Interplay between Terminal and Bridging Diiron Hydrides in Neutral and Oxidized States. Organometallics 36:2245-2253|
|Lalaoui, Noémie; Woods, Toby; Rauchfuss, Thomas B et al. (2017) Characterization of a Borane ? Complex of a Diiron Dithiolate: Model for an Elusive Dihydrogen Adduct. Organometallics 36:2054-2057|
|Schilter, David; Gray, Danielle L; Fuller, Amy L et al. (2017) Synthetic Models for Nickel-Iron Hydrogenase Featuring Redox-Active Ligands. Aust J Chem 70:505-515|
|Reijerse, Edward J; Pham, Cindy C; Pelmenschikov, Vladimir et al. (2017) Direct Observation of an Iron-Bound Terminal Hydride in [FeFe]-Hydrogenase by Nuclear Resonance Vibrational Spectroscopy. J Am Chem Soc 139:4306-4309|
|Carlson, Michaela R; Gilbert-Wilson, Ryan; Gray, Danielle R et al. (2017) Diiron Dithiolate Hydrides Complemented with Proton-Responsive Phosphine-Amine Ligands. Eur J Inorg Chem 2017:3169-3173|
|Zhao, Peihua; Gray, Danielle L; Rauchfuss, Thomas B (2016) Rational Synthesis of the Carbonyl(perthiolato)diiron [Fe2(S3CPh2)(CO)6] and Related Complexes. Eur J Inorg Chem 2016:2681-2683|
|Ulloa, Olbelina A; Huynh, Mioy T; Richers, Casseday P et al. (2016) Mechanism of H2 Production by Models for the [NiFe]-Hydrogenases: Role of Reduced Hydrides. J Am Chem Soc 138:9234-45|
|Li, Yulong; Rauchfuss, Thomas B (2016) Synthesis of Diiron(I) Dithiolato Carbonyl Complexes. Chem Rev 116:7043-77|
|Chambers, Geoffrey M; Huynh, Mioy T; Li, Yulong et al. (2016) Models of the Ni-L and Ni-SIa States of the [NiFe]-Hydrogenase Active Site. Inorg Chem 55:419-31|
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