The mechanisms of conduction in proteins

Theoretical calculations have already shown that the electronic properties of biopolymers may be described in terms of conduction and valence energy bands in which electrons are delocalized to a significant degree. Because these bands are separated by a large energy gap, it is concluded that electronic conduction in such systems must be by 'holes' in the valence band. The mechanism of this conduction is discussed with special reference to dry proteins where the charge-transfer role of appropriate acceptor molecules and the modulating influence of amino acid residues will encourage localized and delocalized hole production at the valence band edge. It is suggested that there are close similarities, which have shown up in measurements, in the electrical behaviour of proteins and other non-biological semi-crystalline solids. The significance of such long-range conduction and attendant polarization is considered briefly in the light of evidence for the existence of proteins in cell membranes and in the skeleton of the cytoplasm