Time Resoved Vibration Spectrocopy of Functioning Substrate-Bound Nitrogenase

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This award in the Inorganic, Bioinorganic and Organometallic Chemistry program supports Professor Stephen P. Cramer at the University of California at Riverside to elucidate the atomic-level mechanism of the nitrogenase enzyme by using time-resolved infra-red (TR-IR) spectroscopy with related techniques. Recent advances in nitrogenase biochemistry and TR-IR spectroscopy offer the prospect of determining the chemistry underpinning biological reduction of nitrogen gas in the atmosphere to ammonia available in soils for plant growth. Specific aims are to use: 1) TR-IR spectroscopy to speciate substrate bound forms of MoFe nitrogenase under turnover conditions. 2) IR kinetics to probe the mechanism of MoFe nitrogenase, particularly with regard to changes in key amino-acid residues and homocitrate during turnover. 3) Terahertz (Far-IR) spectroscopy to study the conformation modes associated with MoFe:Fe protein complex formation. IR kinetics of functioning nitrogenase will be used to probe mechanistic aspects such as proton translocation, changes in the protein conformational concomitant with the energy consuming ATP hydrolysis, and formation and dissociation of the nitrogenase protein complex during enzyme turnover. The broader impacts of this research include: 1) Promoting teaching, training and learning by using state of the art facilities at the University of California Davis, Utah State University, the University of Central Florida and Lawrence Berkeley National Laboratory as well as synchrotron radiation instrumentation at the ALS, Berkeley and Jefferson Laboratory. 2) Establishing a program to involve underrepresented groups (ethnic and disabled) at the high school level through summer internships. 3) The establishment of infrastructure for research and education through both the establishment of unique scientific instrumentation (the TR-IR low volume apparatus) and wide ranging collaborations.