Polarizability tensor theory based upon a Bayley–Nielsen–Schellman-type model Hamiltonian: Circular dichroism calculations of polypeptides

Abstract

In our previous article based upon the usual Fano–DeVoe model Hamiltonian, the partial polymer polarizability tensor equation for describing visible and ultraviolet (VIS/UV) absorption and circular dichroism (CD) spectra was represented in terms of transition moments and a partial polymer Green’s function matrix equation, which is constructed from partial monomer Green’s matrix elements and inter(sub)molecular interaction energies. Here, on the basis of the extended Fano–DeVoe model Hamiltonian similar to the Bayley–Nielsen–Schellman secular Hamiltonian matrix, we represent a partial polymer polarizability tensor matrix equation in terms of transition moments and a partial polymer Green’s function matrix equation, which is constructed from partial monomer Green’s matrix elements, inter(sub)molecular interaction energies, and inter(sub)molecular electrostatic interaction energies. The last ones are newly taken into account. Computing the amide monomer spectroscopic parameters by the CNDO/S method and substituting them into the polymer polarizability tensor matrix equation derived, we have successfully carried out the CD band shape calculations on polypeptides having α-helix and β-sheet structures and on a tripeptide, N-acetyl-Pro-Gly-Leu-OH having a type II β-turn conformation.