Electrochemistry of amphiphilic ferrocene alcohols and oxidative electro-enzymology with myoglobin and cytochrome P450

Date of Completion

January 1998

Keywords

Chemistry, Analytical|Chemistry, Biochemistry|Chemistry, Organic

Degree

Ph.D.

Abstract

This thesis consists of two parts. In the first part, 2-ferrocenyl-2-decanol, 2-ferrocenyl-2-tetradecanol and 2-ferroceneyl-2-octadecanol were synthesized and evaluated as electrochemical probes for the behavior of alcohols in micellar solutions and microemulsions. One-electron oxidations of the ferrocene moieties were nearly reversible and controlled by diffusion in microemulsions. The electrode reactions were more complex in micellar solutions, and were influenced by diffusion, adsorption onto the electrode, and possibly chemical reactions coupled to electron transfer. Amphiphilic ferrocene alcohols were reasonably informative electrochemical probes in bicontinuous microemulsions made with cationic and anionic surfactants. Apparent diffusion coefficients suggested that the alcohols were distributed between the oil-water interfaces and the oil phase of the microemulsions, with increase in chain length favoring binding at the interface.^ In the second part of this thesis, the activation of cytochrome P450 enzymes was studied by electrochemically-driven oxidation of styrene and cis-$\beta$-methylstyrene catalyzed by cytochrome P450cam. These enzymes can activate organic pollutants to induce DNA damage. Myoglobin, with properties similar to cytochrome P450cam, also can act as an oxidation catalyst. Myoglobin was first evaluated as a model oxidation catalyst to mimic catalysis by cytochrome P450cam. Myoglobin and cytochrome P450cam were used to catalyze electrochemically-driven oxidations of styrene and cis-$\beta$-methylstyrene in solution, and in protein-lipid and protein-polyion films. Styrene was oxidized to styrene oxide, and cis-$\beta$-methylstyrene was oxidized to cis-$\beta$-methylstyrene oxide and trans-$\beta$-methylstyrene oxide. Control experiments gave much smaller amounts of products if proteins were not present. Electrodes coated with a layered protein-lipid and protein-polyion films also catalyzed the oxidations with higher turnover numbers than with these proteins in solution. Chemical oxidations catalyzed by these proteins were also done to make a comparison. The ratio of cis- and trans-methylstyrene oxides from oxidation by protein films was smaller than that observed from oxidations by proteins in solution. Low levels of oxygen favored production of the cis-isomer, which probably reflects a stereospecific reaction similar to that in the natural enzyme system. ^

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