Theoretical investigations on the intramolecular electron transfer between the intermediate residues of different secondary structures of an oligopeptide have been carried out. Density functional theory calculations have been performed to calculate the charge transfer integral, spatial overlap integral and site-energies for the optimized secondary structures of the glycine oligopeptide by varying the dihedral angles (phi and psi) along the alpha-carbon atom of amino acid subgroups. The reorganization energy has been calculated in the presence of an excess negative charge. The electron transfer rates for the model peptide have been estimated and the dependence of the rate on secondary structures is discussed. (c) 2007 Elsevier B.V. All rights reserved.