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Justine Roth
Inorganic, Bioinorganic & Biophysical Chemistry Phone: 410.516.7835 PhD - University of Washington The Roth group performs research at the interface of chemistry and biology with focus on the mechanisms of redox reactions in proteins. Specifically we are interested in: (i) C–H and O–H bond oxidations, (ii) transition-metal mediated O2 activation and (iii) processing of reactive oxygen species (e.g. O2–, ONO2–, OCl–). Proton-coupled electron transfer (PCET) occurs widely in enzymes that perform selective oxidations of C–H and O–H bonds. In one type of PCET, the proton and the electron(s) move together in a single step between different donor and acceptor sites. We are investigating how this mechanism may explain site-specific protein oxidation, repair of damaged amino acid residues and the involvement of amino acid radicals in enzyme catalysis. An initial focus is prostaglandin H synthase (PGHS), a bifunctional peroxidase-oxygenase responsible for the first step in the biosynthesis of effector molecules associated with inflammation mediated by the autoimmune response. New mechanistic probes are being developed in our laboratories to study reactions of transition metal complexes with O2 and reactive oxygen species. One approach involves analyzing oxygen-18 isotope effects on rates and equilibria. The measurements are carried out using natural abundance reagents, high-vacuum techniques and stable isotope mass spectrometry. We have shown that oxygen-18 kinetic isotope effects can provide unique information about structures of transition states and high-energy intermediates that could not be obtained using conventional spectroscopic techniques. A major objective of our work is to understand origins of catalytic rate acceleration by redox enzymes. To this end, we compare reactions in the active site to those occurring by the same mechanisms in solution. Through the application of Marcus theory we evaluate the relative importance of thermodynamics, electrostatics and quantum mechanical effects to determining reaction rates. |
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