Electrochemistry and electrocatalysis with myoglobin in biomembrane-like surfactant-polymer 2C(12)N(+)PA(-)composite films

Biomembrane-like polyionic complex, 2C(12)N(+)PA(-), was prepared by reacti ng sodium polyacrylate (Na(+)PA(-)) with didodecyldimethylammonium bromide (2C(12)N(+)Br(-)). Stable thin films made from 2C(12)N(+)PA(-), with incorp orated myoglobin (Mb), on pyrolytic graphite (PG) electrodes were then char acterized by electrochemistry and other techniques. Cyclic voltammetry of M b-2C(12)N(+)PA(-) films showed a pair of well-defined quasi reversible peak s for MbFe(III)/Fe(II) couple at about - 0.19 V versus SCE in pH 5.5 buffer s. The electron transfer rate between Mb and PG electrodes was greatly faci litated in the microenvironment of 2C(12)N(+)PA(-) films. Square wave volta mmetry data were used to estimate the apparent heterogeneous electron trans fer rate constants by nonlinear regression analysis using a model featuring dispersion of formal potentials. Positions of Soret absorption bands sugge sted that Mb keeps its secondary structure similar to its native state in 2 C(12)N(+)PA(-) films at the medium pH. The results of differential scanning calorimetry and X-ray diffraction suggest that synthesized 2C(12)N(+)PA(-) lipid films have an ordered multibilayer structure and the incorporated Mb does not disturb this structure. Oxygen was catalytically reduced by Mb-2C (12)N(+)PA(-) films with a significant decrease in the electrode potential. MbFe(I), a highly reduced form of Mb, was also produced in Mb-2C(12)N(+)PA (-) films at about -1.09 V, and could be used to catalytically reduce organ ohalide pollutants such as perchloroethylene (PCE) and trichloroethylene (T CE). The catalytic reduction peak currents had linear relationships with co ncentrations of PCE and TCE in a range of 10-100 mu M. The potential applic ations of the film electrode as a sensor for detecting organohalides are di scussed. (C) 2000 Elsevier Science B.V. All rights reserved.