Proton Coupled Electron Transfer. Redox Cofactors, Catalysis, and Photochemistry

Project: Research project

Description

The importance that proton coupled electron transfer (PCET) plays in chemistry and biology, with its significant implications for catalysis and energy conversion in both and on biological function and disease, are only beginning to be fully appreciated. Full understanding of elementary processes remains to be achieved and application of that knowledge to real world problems is only beginning.

This project moves past previous NSF supported research in this area to focus on two important themes. In one, an assessment of the role of PCET in the key redox cofactors of biology will be investigated with an eye toward elucidating their roles in the larger sweep of enzymatic reactivity. In the other, recently uncovered roles for PCET in excited state chemistry will be extended to map out this important reactivity, its role in molecular photochemistry, and, potentially, its role in chemical synthesis.

2) Statement on Intellectual Merit:
In previous NSF-funded research we investigated oxidation of the redox active amino acids cysteine, tyrosine, and tryptophan and the redox interconversion between 1,4-quinone and its hydroquinone. Stopped flow and cyclic voltammetry measurements were used to measure rates and elucidate the role of PCET and concerted electron-proton transfer (EPT) by the reversible metal polypyridyl complex couples M(bpy)33+/2+ (M = Fe, Ru, Os).

Here we propose to move these studies to a new dimension, the role of PCET in redox cofactors and pathways and mechanisms that help dictate biological function. PCET mechanism will be explored in concert with functional analysis of oxido-reductase protein structures with application of a computational protocol based on the Rosetta energy function.

PCET and EPT will be investigated in quinone/hydroquinone interconversion and in the isoalloxazine functional group of flavins and the dihydropyridine/pyridinium functional group of nictotinamides. Investigations on redox cofactors will be extended to modified electrodes to explore PCET/EPT at electrode interfaces with possible applications in analysis and electrocatalysis.

Finally, excited state PCET will be extended to H-atom and photoEPT reactivity in solution and on the surfaces of mesoscopic, nanostructured oxide films with an eye toward photoelectrochemical organic synthesis.

3) Statement on Broader Impacts:

Professor Meyer lectures extensively on Proton Coupled Electron Transfer at conferences and in scientific visits both in the US and internationally. PCET will be the major theme of a conference that he is helping to organize in Upsala, Sweden in June, 2014. The meeting will feature contributions from junior researchers with significant participation by graduate students and postdoctoral research fellows.

Graduate students and postdoctoral research fellows at UNC are active in presenting in educational venues at UNC-CH and at schools in the Research Triangle area including participation in a summer program for underrepresented minority students, “Climate LEAP”. and a summer undergraduate research program sponsored by the UNC Environmental Program.
Students and postdocs have contributed to local education through lectures at the NC School of Science and Mathematics in Durham, N.C.
StatusFinished
Effective start/end date7/15/146/30/17

Funding

  • National Science Foundation (NSF)

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Photochemical reactions
Catalysis
Protons
Electrons
Proton transfer
Students
Oxidation-Reduction
Excited states
Functional groups
Flavins
Electrocatalysis
Functional analysis
Electrodes
Metal complexes
Energy conversion
Tryptophan
Cyclic voltammetry
Oxide films
Cysteine
Tyrosine