Abstract: Myoglobin(Mb)-chitosan-colloidal gold films were made by casting a solution of Mb, chitosan and colloidal gold on glass carbon electrodes. Mb incorporated in chitosancolloidal gold films gave a pair of stable, welldefined, and quasireversible cyclic voltammetric peaks at about -0.20 V(vs.Ag/AgCl) in 0.1 mol/L NaAcHAc buffer (pH=5.4), being the characteristic peaks of the Mb heme Fe(Ⅱ)/Fe(Ⅲ) redox couple. The effects of scan rate, pH and concentration of buffer solutions on the electrochemical behavior of Mb were studied in detail. Position of the Soret absorbance band suggests that Mb in chitosan colloidalgold kept its secondary structure similar to the native states. Oxygen was cata lytically reduced by Mb in chitosancolloidal gold films.

Key words: myoglobin, chitosan, colloidal gold, direct electrochemistry, electrochemical catalysis