Scaffold-based Synthetic Models of Mono-Iron Hydrogenase: Structure and Dynamics

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With this award, the Chemistry of Life Processes Program in the Chemistry Division is funding Prof. Michael Rose at the University of Texas at Austin to investigate the role of the iron center in an enzyme called mono-iron hydrogenase. This enzyme is molecule important for the capture of carbon dioxide (CO2) in methanogens, which are single cell microorganisms that can be found for example in the human gut and in wetlands. These organisms are very efficient at transforming dihydrogen (H2) and CO2 from the environment in which they live into methane. In contrast, artificial way to capture and transform H2 and CO2 are much less efficient. Furthermore while the enzymes, in particular mono-iron hydrogenase, utilize earth abundant metals like iron and nickel, many synthetic analogues of the enzymes utilize precious metals like platinum, iridium or palladium. The research of Professor Rose focuses on understanding how the mono-iron hydrogenase catalyzes the chemical transformation in the methanogens and applying this understanding to developing artificial catalysts as efficient as the enzyme. Professor Rose also participates in the outreach program called H2fromH2O. He interacts with high school students in the central Texas region to demonstrate the fundamental science, environmental impact and possible applications for splitting water into hydrogen and oxygen and derive energy from this process. The students who participate in the outreach program further disseminate such lessons to their families and communities. This serves to raise awareness about the importance of developing renewable energy technologies. UT Austin undergraduates directly participate in the outreach efforts, become motivate to do research, and pursue job opportunities and graduate education in energy-related fields.The available, iron-based synthetic (artificial) systems of a molecular nature do not replicate the speed and efficiency of the naturally occurring system. This research seeks to understand how components of the natural system can be incorporated to provide for enhanced reactivity. There are three technical approaches to understanding the H2-activating and hydride transfer activity of the enzyme mono-iron hydrogenase. First, synthetic model complexes are hybridized with protein hosts to determine the effect of the protein environment on the spectroscopic properties and functional reactivity of the model complexes (versus stand-alone metal complexes). Second, the "anthracene scaffold" strategy for assembling the biomimetic fac-CNS motif is modified with more flexible "anthranoid" scaffolds to investigate the role of protein-like flexibility of the donor arms on the reactivity of the model complexes. Third, the complexes contain a biomimetic pyridine moiety, which is hypothesized to assist in H2 heterolysis as a pendant base.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.