Proton coupled electron transfer and structural dynamics in biomimetic beta hairpins
McCaslin, Tyler Grantt
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Several crucial proteins required for the maintenance of life on earth utilize the potent oxidant of tyrosyl radical in their catalytic mechanism. This free radical species can have devastating effects, yet nature has crafted ways to control its reactivity. The means by which the thermodynamics and kinetics of proton-coupled electron transfer reactions of tyrosine and tryptophan are tuned is of profound importance. By utilizing biologically-inspired peptide-based model systems, or maquettes, one can measure the effect of the surrounding protein environment on the reactivity of tyrosyl radicals and redox-linked conformational changes that result from electron transfer and proton-coupled electron transfer. This work utilizes a wide variety of spectroscopic, electrochemical, and computational tools to characterize these reactions in a library of biomimetic peptide models. Factors of control of tyrosine-mediated electron transfer (including electronic coupling to the peptide backbone, proton coupling, aromatic-aromatic interactions, and metal-ion effects) will be investigated. Elucidating the mechanisms of controlling these radicals will inform the design of catalytic devices towards the goal of artificial solar energy conversion.