A comparison of the higher order harmonic components derived from large-amplitude fourier transformed ac voltammetry of myoglobin and heme in DDAB films at a pyrolytic graphite electrode

A debate as to whether heme remains bound or is released in myoglobin molecules incorporated into a didodecyldimethylammonium bromide (DDAB) film adhered to a pyrolytic graphite electrode has prompted a comparison of their electrochemistry by the highly sensitive large-amplitude Fourier transformed ac voltammetric method. The accessibility of third, fourth, and higher harmonic components that are devoid of background current and the enhanced resolution relative to that available in do voltammetry have allowed a detailed comparison of the Fe-III/Fe-II and Fe-II/Fe-I redox processes of myoglobin and heme molecules to be undertaken as a function of buffer composition and pH and in the presence and absence of NaBr in the buffer and/or film. Under most conditions examined, only very subtle differences, in the Fe-III/Fe-II process were found. implying this process cannot be used to indicate the intactness or otherwise of myoglobin in myoglobin-DDAB films.