Date of Award

2009

Degree Type

Dissertation

Department

Chemistry

First Advisor

Bayachou, Mekki

Subject Headings

Electrochemistry, Ionic solutions, Heme, Hemoproteins, Nitric-oxide synthase, Electrochemistry, Hemeproteins, Nitric oxide synthase, NOS, Myoglobin, Proton transfer, Ionic liquids, Isotopic effects

Abstract

We investigate the changing behaviors of myoglobin and nitric oxide synthase (NOS) in the near-absence of bulk water and/or protons by using ionic liquid butyl methyl imidazolium tetrafluoroborate as a non-aqueous milieu. Through direct charge transfer and metalloprotein-mediated catalytic reduction of oxygen and nitric oxide, we shed light on diverging aspects on how the two hemeproteins face the scarcity of water and/or protons in bulk. Isotopic effect investigations using D2O further elucidates kinetic aspects of proton transfer. Finally, in the case of NOS oxygenase, pterin cofactor binding and NOS-mediated catalytic oxidation of L-arginine in ionic liquids interrogates proton and water availability as a modulating factor affecting electrochemically-driven production of nitric oxide. Overall, our results indicate that the catalytic and redox properties of NOS and other heme-proteins change in a unique way as a function of available water. The redox and catalytic behavior of each metalloprotein is rationalized in terms of its inherent structural aspects

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