Secondary Structure Conformations and Long Range Electronic Interactions in Oligopeptides

Abstract

Combined quantum mechanical coupling calculations and molecular dynamics simulations were performed to examine the role of modest geometrical fluctuations of peptide secondary structures on long range electronic interactions in oligopeptides. Molecular dynamics simulations were performed to obtain typical relevant conformations of oligopeptides, and self-consistent Hartree−Fock calculations at the semiempirical quantum theory level were performed to extract the long range electronic propagation. Initial α-helical oligopeptides show dominant hole-mediated coupling over a large tunneling energy range, while the initial extended conformation oligopeptides have more nearly equal contributions from both hole and electron mechanisms. Modest geometrical fluctuations lead to changes in the character of long range electronic interactions. The computations highlight the danger of drawing conclusions from electronic structure calculations of electronic coupling in peptide model systems on the basis of computations on single geometries.