Electronic structure and transport properties of polypeptides: Anab initiocrystal orbital study of a periodic polyglycine chain

The electronic structure of an infinite periodic polyglycine chain is studied in its β conformation with the aid of the ab initio Hartree-Fock self-consistent-field crystal-orbital method. The calculated large forbidden band gap indicates absence of intrinsic semiconduction. The calculated wave function, charge-carrier mean free path, and their mobility are consistent with an impurity semiconduction mechanism with delocalized holes, but not electrons. The mobility on the basis of this theory is expected to be very low. Furthermore, a critical comparison with earlier semiempirical band-structure calculations is provided.