Conformational aspects of polypeptides. XXIV. Conformational energies of poly‐N‐methyl‐L‐alanine chains

Conformational energies of the poly‐ N ‐methyl‐ L ‐alanine chain have been calculated as a function of the rotational angles of its skeletal bonds, taking into account torsional potentials, van der Waals repulsions, and London attractions. Four pronounced minima in the energy were found; the relative magnitudes of the energies at these minima suggest that the preferred conformation of this chain is either a right‐handed, approximately threefold helix, or a slightly distorted, left‐handed α‐helix. Inclusion of an estimate of the dipolar contribution to the total conformational energy does not significantly affect this conclusion.