ELECTRON-TRANSFER BETWEEN MYOGLOBIN AND ELECTRODES IN THIN-FILMS OF PHOSPHATIDYLCHOLINES AND DIHEXADECYLPHOSPHATE

Myoglobin (Mb) in thin films of phosphatidyl cholines (PC) or dihexade cyl phosphate (DHP) gave direct, reversible electron transfer between pyrolytic graphite electrodes and the heme Fe(III)/Fe(II) redox couple of the protein. PC films incorporated much more Mb than DHP films. A model assuming several classes of electroactive sites in the films on the electrode with a dispersion of standard potentials successfully fi t square-wave voltammetric data at pulse heights >50 mV. Electron tran sfer rate constants in PC and DHP films were significantly larger than for Mb in thin films of an insoluble cationic surfactant. The pH depe ndence of the formal potential of Mb in the PC films suggested that pr otonation, possibly inducing conformational change, accompanies electr on transfer to MbFe(III) between pH 5 and 11. Mb in PC films was used for catalysis of the reduction of trichloroacetic acid.