Molecular orbital calculations on polypeptides and proteins. Part I. Extended Hückel theory calculations on trans-dipeptides

Abstract

By use of extended Hückel theory (EHT), the energies for different conformations of trans-dipeptides have been calculated. The results have been compared with those obtained from ‘contact’ criteria and potential energy formulae. The molecular orbital treatment appears to be superior to the classical approches for predicting the regions of stability on the conformational (ϕ,ψ) map. The present calculations predict that alanine residues favour helix formation while glycyl residues lead to random chains.