Oxygen Sensitivity and Functional Models of Nitrile Hydratase

University Of Louisville Research Foundation Inc, Louisville KY

Investigators

Abstract

This award in the Inorganic, Bioinorganic and Organometallic Chemistry program supports research by Professor Craig Grapperhaus at the University of Louisville that focuses on functional model complexes of nitrile hydratase (NHase) and the related oxygen sensitivity of iron thiolates. The project includes the synthesis and spectroscopic characterization of target complexes coupled with reactivity studies and computational methods to develop an understanding of the relationship between electronic structure and reactivity. The first specific aim is to test the hypothesis that functional NHase models mimic S-oxygenation effects including tuning of Lewis acidity and substrate activation/intermediate stabilization via a second coordination sphere. To meet this objective, substrate binding and activity assays with electronic mimics of NHase that lack S-oxygenated ligands will be investigated. Further, Ru model complexes that incorporate S-oxygenation will be developed to probe their second coordination sphere effects and new ligands with alternate second coordination sphere moieties will be prepared and evaluated. The second specific aim will probe the NHase oxygen-sensitivity of iron-thiolates. The hypothesis that oxygen sensitivity of Fe-thiolates is spin-state dependent with low-spin Fe yielding S-oxygenates and high-spin Fe forming disulfides and Fe-oxo clusters will be evaluated via reactivity studies on a series of Fe complexes with varying spin-states. Complimentary density functional theory investigations to elucidate the electronic structure effects will be conducted. Additionally, the hypothesis that chelate ring size can enforce S-coordination of Fe S-oxygenates will be evaluated through the design and synthesis of new ligand motifs. The broader impacts of this study focus on promoting teaching, training and learning and broadening the participation of students in an underrepresented region. This project will provide training for post-doctoral fellows and graduate students working alongside undergraduate researchers and high school students in the fields of synthesis, spectroscopy, reactivity, and computation. Undergraduate students will be recruited locally and from regional undergraduate institutions. Additionally, collaborative efforts with a faculty member and students at a primarily undergraduate institution (PUI) are in place. The annual, regional undergraduate research symposium initiated by the PI as a mechanism for students and faculty at PUIs to present research will be continued with the aim of including industrial participation to bridge the gap between industry and undergraduate students. This symposium has been successful at attracting female and underrepresented minorities, including participants from a historically black university.