Abstract: Mb-DDAB-clay film electrodes were made by casting aqueous dispersions of didodecyldimethylammonium bromide(DDAB)-clay composite and the protein myoglobin(Mb) on pyrolytic graphite(PG) electrodes. Cyclic voltammetry of Mb-DDAB-clay films showed a pair of well defined and nearly reversible peaks at about -0.25 Vvs. SCEin pH5.5 buffers, being the characteristic peaks of the Mb heme Fe(Ⅲ)/Fe(Ⅱ) redox couples. In the microenvironment of DDABclay films, the electron transfer between Mb and PGwas greatly enhanced, and showed a good stability during storage. Soret absorption band positions suggested that Mb retained its native conformation in these films at medium pH. The interlayer clay spacing estimated by X-ray diffraction suggested that the incorporated Mb did not disturb the ordered multilayer structure of the films. The average formal potential of Mb heme Fe(Ⅲ)/Fe(Ⅱ) couples in DDAB-clay films shifted linearly from pH4.5 to 11 with a slope of -53 mV/pH, suggesting that one proton was coupled with each electron transfer. The dissolved oxygen and trichloroacetic acid was catalytically reduced by Mb-DDAB-clay film electrodes.

Key words: Myoglobin, Surfactant-clay composite, Multibilayer composite film electrodes, Electrochemistry, Electrochemical catalysis