Conformational energy map for a pair of peptide units using the bond polarisability method

A method recently developed for the calculation of intramolecular nonbonded interactions based on experimental bond polarisabilities and atomic charges and transition π-charges obtained from MO calculations has been applied to the alanyl dipeptide. The potential energy contours in the ?, ψ plane obtained by this method compare favourably with those derived from the frequency of occurrence of conformations in globular proteins. An analysis of the various components of the nonbonded interaction energy indicates that the fairly frequent occurrence of conformations around ? = ?80°, ψ=0° is presumably due to a favourable interaction of the π-polarisation.