Electrochemical Generation and Reactions of Ferrylmyoglobins in Water and Microemulsions

作者：Anthony C. Onuoha, Xiaolin Zu, James F. Rusling · 发表于：Journal of the American Chemical Society · 年份：1997 · DOI：10.1021/ja964007l · 被引用次数：78 · 研究领域：Hemoglobin structure and function、Heme Oxygenase-1 and Carbon Monoxide、Porphyrin and Phthalocyanine Chemistry

Ferrylmyoglobin species, which are active oxidant forms of the protein myoglobin, were obtained by electrochemical reduction of metmyoglobin [MbFe III ] in the presence of oxygen in aqueous neutral buffer and in microemulsions of oil, water, and cationic surfactant. Reduction of myoglobin at −0.4 V vs SCE catalyzed the reduction of oxygen to hydrogen peroxide at the electrode. Hydrogen peroxide oxidizes metmyoglobin in solution to give the radical ferrylmyoglobin • X−MbFe IV O, which is known to decay rapidly to the non-radical MbFe IV O. This complex reduction−oxidation process converted nearly all of the 30 μM myoglobin in a spectroelectrochemical cell to ferrylmyoglobins in 15 min in pH 7.3 buffer and in 18 min in microemulsions. Characteristic ferryl heme absorbance bands near 421, 548, and 584 nm were used to identify products. Confirmation of ferrylmyoglobins was provided by reductions to metmyoglobin with ascorbate and by myoglobin-mediated electrochemical epoxidation of styrene. Fiftyfold higher yields of styrene oxide and benzaldehyde were achieved in a microemulsion compared to electrochemical or chemical methods in pH 7.4 buffer. The electrochemical approach described may also prove useful for investigating active catalytic species of heme enzymes such as cytochrome P450.