Many biochemical processes involve the coupled transfer of electrons and protons. This is a key step, for instance, for a range of enzymes (e.g., cytochrome c oxidase, photosystems I and II, cytochromes P450) and in the trapping of reactive oxygen species (e.g., by vitamin E and superoxide dismutases). The goal of the proposed research is to develop a fundamental and predictive understanding of these processes. This understanding will be valuable in a range of biochemical systems, much as the current knowledge of pure electron transfer has been very valuable. The proposed work encompasses a variety of compounds, reactions, and techniques to uncover the essential features of the chemistry. Hydrogen atom transfer reactions are a primary focus of the proposal, building on the recent discovery that a range of H-atom transfer reactions follow the Marcus cross relation. The Marcus approach enables prediction of reaction rates and provides a new fundamental intuition for these reactions, based on driving force and intrinsic barriers. The intrinsic barriers can be measured through studies of self-exchange rates, which will be determined for a number of compounds. The relationship between the intrinsic barriers for electron, proton, and hydrogen atom transfer will be examined. Extensions to hydride transfer reactions are discussed, including possible application of the Marcus approach. New chemical systems will be developed in which an intramolecular proton transfer is coupled to intermolecular electron transfer. Such proton-coupled electron transfer (PCET) processes are very common, as in the oxidation of the tyrosine Z-histidine unit in photosystem II. It will be determined whether proton transfer precedes, succeeds, or is concerted with electron transfer in such systems. The reasons for adopting one mechanism or another will be probed, using the intrinsic barriers and thermodynamics of the reactions. Chemical reactions that involve metal peroxide complexes will also be examined, both reactions of isolated peroxides and reactions that could form O-O bonds. The proposed work takes a broad view - studying iron, cobalt, manganese, ruthenium and osmium systems and a variety of types of reactions - in order to provide new and valuable insights into the various kinds of proton-coupled electron transfer that occur in biology.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM050422-12
Application #
7035853
Study Section
Metallobiochemistry Study Section (BMT)
Program Officer
Preusch, Peter C
Project Start
1995-02-01
Project End
2007-08-31
Budget Start
2006-04-01
Budget End
2007-08-31
Support Year
12
Fiscal Year
2006
Total Cost
$288,566
Indirect Cost
Name
University of Washington
Department
Chemistry
Type
Schools of Arts and Sciences
DUNS #
605799469
City
Seattle
State
WA
Country
United States
Zip Code
98195
Markle, Todd F; Darcy, Julia W; Mayer, James M (2018) A new strategy to efficiently cleave and form C-H bonds using proton-coupled electron transfer. Sci Adv 4:eaat5776
Saouma, Caroline T; Richard, Sarah; Smolders, Simon et al. (2018) Bulk-to-Surface Proton-Coupled Electron Transfer Reactivity of the Metal-Organic Framework MIL-125. J Am Chem Soc 140:16184-16189
Bowring, Miriam A; Bradshaw, Liam R; Parada, Giovanny A et al. (2018) Activationless Multiple-Site Concerted Proton-Electron Tunneling. J Am Chem Soc 140:7449-7452
Heimann, Jessica E; Bernskoetter, Wesley H; Hazari, Nilay et al. (2018) Acceleration of CO2 insertion into metal hydrides: ligand, Lewis acid, and solvent effects on reaction kinetics. Chem Sci 9:6629-6638
Darcy, Julia W; Koronkiewicz, Brian; Parada, Giovanny A et al. (2018) A Continuum of Proton-Coupled Electron Transfer Reactivity. Acc Chem Res 51:2391-2399
Dhar, Debanjan; Yee, Gereon M; Markle, Todd F et al. (2017) Reactivity of the copper(iii)-hydroxide unit with phenols. Chem Sci 8:1075-1085
Porter, Thomas R; Hayes, Ellen C; Kaminsky, Werner et al. (2017) Sterically directed nitronate complexes of 2,6-di-tert-butyl-4-nitrophenoxide with Cu(ii) and Zn(ii) and their H-atom transfer reactivity. Dalton Trans 46:2551-2558
Wang, Yu-Heng; Pegis, Michael L; Mayer, James M et al. (2017) Molecular Cobalt Catalysts for O2 Reduction: Low-Overpotential Production of H2O2 and Comparison with Iron-Based Catalysts. J Am Chem Soc 139:16458-16461
Kolmar, Scott S; Mayer, James M (2017) SmI2(H2O)n Reduction of Electron Rich Enamines by Proton-Coupled Electron Transfer. J Am Chem Soc 139:10687-10692
Kim, Byoungmoo; Storch, Golo; Banerjee, Gourab et al. (2017) Stereodynamic Quinone-Hydroquinone Molecules That Enantiomerize at sp3-Carbon via Redox-Interconversion. J Am Chem Soc 139:15239-15244

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