ELECTROCHEMISTRY AND CATALYSIS WITH MYOGLOBIN IN HYDRATED POLY(ESTER SULFONIC-ACID) IONOMER FILMS

Thin films made from the ionomer poly(ester sulfonic acid) Eastman AQ3 8 and the protein myoglobin (Mb) on pyrolytic graphite (PG) electrodes formed stable hydrated gels in water. While interactions between Mb a nd the ionomer undoubtedly control retention of the protein, Soret abs orbance band positions suggest that Mb retains a conformation similar to the native state in the medium pH range. Cyclic voltammograms were reproducible for several months when Mb-AQ38 films were stored dry or immersed in aqueous buffer. The formal potential of Mb heme Fe(III)/Fe (II) in AQ films shifted -50 mV/pH between pH 4 and, 10, suggesting th at one electron and one proton are involved in the electrochemical rea ction. Square wave voltammograms of Mb in the AQ films were fit by non linear regression analysis using a model featuring dispersion of forma l potentials. The effective electron transfer rate between PG electrod es and the iron heme of Mb in AQ38 films was comparable to those in su rfactant films, but much faster than on bare PG in Mb solutions. Oxyge n and trichloroacetic acid were catalytically reduced by Mb in AQ film s with significant decreases in the electrode potential required.