Ferrous form of myoglobin and other heme-proteins can catalyze reductive dehalogenation of vicinal dihalides. We investigated electrochemical reduction of dibromocyclohexane (DBCH) and other dihalides using microemulsion as solvents. Microemulsions are clear mixtures of water, oil, surfactant and alcohol that have advantages in low toxicity, low cost and pathway control. Dihalide reductions to olefins catalyzed by surfactant-myoglobin film (SF-Mb) adsorbed on the electrode surface or by myoglobin-Poly-lysine film (PLL-Mb) covalently linked to the electrode surface were investigated. DBCH catalysis at myoglobin film electrodes was dependent on surfactant type. QCM studies revealed electrostatic interaction between cationic poly-lysine film and surfactant charges which influenced substrate localization in PLL-Mb film. Electrostatic interaction of myoglobin amino acid residues and surfactant charges dictated substrate localization on myoglobin at SF-Mb film; thus reaction site and catalytic reaction pathway. Fluorescence studies with pyrene to probe substrate environment in Mb film indicated organic substrate experiences polar environment in cationic CTAB bicontinuous microemulsion where as a non-polar environment in anionic SDS bicontinuous microemulsion.
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