Direct electron transfer reaction of hemoglobin at the bare silver electrode

Abstract

Most blologlcal macromolecules exhlblt rather low rates of electron transfer so that the resultmg currents are observed with difficulty at conventlonal electrodes, even when applymg relatively large overpotentlals Indeed, for many years it was thought that direct electron transfer between electrodes and redox protems was not possible for the reasons ascribed either to their extended three-dlmenslonal structure and the resulting maccesslblhty of the electroactlve center or to their adsorption onto and subsequent passlvatlon of the electrode surface Only relatively recently has the feaslblhty of studymg the electron transfer reactions of redox proteins at an electrode surface been viewed with any real optlmlsm Essentially, three different approaches have been tried to achieve direct electrode responses of the redox proteins The group of Hill and coworkers [1,2] has been at the forefront of developmg efficient and, possibly, speclflc promoters of bloelectrochemistry Baldwm 131, Dong [41 and other workers have devoted themselves to the fmdmg of the medlators which will catalyze the redox reactions of the proteins However, Hagen [Sl, Hawkrldge [61 and others have taken the approach to do without promoters or mediators by developing special pretreatment procedures and experlmental protocol for the use of bare electrodes Obviously, the last method may be the most appropriate, though unpromoted or unmediated bloelectrochemistry on bare electrodes 1s usually more difficult to obtam, because the data mterpretatlon may be hampered when the responses are determined speclflcally by the properties mtrmslc to the promoters