COMPOSITE FILMS OF SURFACTANTS, NATION, AND PROTEINS WITH ELECTROCHEMICAL AND ENZYME-ACTIVITY

Stable, functional composite films were made from the ionomer Nafion, water-insoluble surfactants, and heme proteins or the enzyme alcohol d ehydrogenase. Rates of electron transfer between myoglobin (Mb) and. h emoglobin (Hb) and edge plane pyrolytic graphite (PG) electrodes in th ese composite films were much larger than those for Hb and Mb in solut ion on Nafion-coated or bare PG electrodes. Films containing Nafion, d idodecydimethylammanium bromide (DDAB), and hemoglobin or myoglobin re tained about 90% of the initial redox activity during 4 weeks of stora ge at 4 degrees C. DDAB is arranged in lamellar Liquid crystal bilayer s in these films at 25 degrees C, which were more stable than films of the proteins and DDAB alone. Films of Nafion-lecithin-Cyt c on edge p lane PG also had good electrochemical properties but were much less st able. Electronic and vibrational spectra indicate that the heme protei ns are not denatured in the composite films, but conformational differ ences from the native state may exist. Linear dichroism suggests that the proteins are specifically oriented in these films. After treatment with a cross-linking agent, Nafion-lipid films containing the enzyme alcohol dehydrogenase retained twice the activity of the enzyme in sol ution (4 degrees C) when stored for 2 days at room temperature.