| Metalloproteins regulate and catalyze many biologically important redox transformations. Electrochemistry is a powerful means in which to probe such chemistry to understand how structure influences reactivity and how thermodynamic properties affect kinetics. Several electrochemical methodologies used with proteins are described including direct, mediated, and thin film techniques.; Cytochrome P450, CYP119, is electrochemically active in thermostable surfactant films (DDAPSS) up to temperatures exceeding 90°C. CYP119 is capable of reducing carbon tetrachloride, and other chlorinated C1 substrates, to methane; at elevated temperatures the efficiency and turnover rate increases while the apparent activation energy decreases.; The effect of temperature, pH, and applied potential on CYP119 reduction of C2 chloro-carbons is examined. The reduction of 1,1,1-trichloroethane under various environments suggests strict control of the reduction pathway, yielding similar products regardless of whether catalysis occurs at the Fe III/II or FeII/I couple. Observed differences in product distributions are attributed to the lifetime of key intermediates.; The dynamic protein film environment is examined for effects on electrochemical behavior. The surfactant films used to immobilize heme proteins, DDAB, undergo a liquid crystal to gel phase transition at -360 mV as determined using EQCM. The change in the film's viscosity alters the redox properties of proteins but not small molecules.; The final part of this work describes the first electrochemical examination of the catalytic domain of wt MoFe and DeltanifB precursor proteins of nitrogenase. Protein adsorption is achieved by repeated electrochemical cycling. An unusual two electron/one proton dependence is observed which correlates to a structural reorganization of the protein's P cluster and different ligation of the oxidized versus reduced states. While electrochemically driven catalysis has yet to be achieved, this new method of probing nitrogenase may still be used to further understand the protein's activity and structure. |
