Poly(ester-sulfonic acid): modified carbon electrodes for the electrochemical study of c-type cytochromes

Various mono- and polyheme c-type cytochromes are able to spontaneously inc orporate within thin films made from the ionomer poly(ester-sulfonic acid) Eastman AQ-29D acting as cation-exchange films cast on carbon electrodes. A Q-films as evidenced from scanning electron microscopy are uniform. The ele ctron transfer within this cation-exchange film is strongly affected by the film thickness. The performances of the AQ-films to incorporate cytochrome s by varying pH are examined on the basis of electrostatic interactions whi ch principally govern the incorporation process. From film-transfer experim ents, a model consisting of a two-phase ionomer coating has been developed for cytochrome c, An indirect approach based on the study of the incorporat ion of nonelectroactive proteins and peptides is reported. The respective a bilities of AQ-29D and Nafion films to incorporate/not to incorporate c-typ e cytochromes and other 'low molar mass' species are explained by the forma tion of hydrated gellike AQ-films. (C) 1999 Elsevier Science Ltd. All right s reserved.