Polymerization dependence of the entropy of homo-oligomer peptides

Statistical mechanical principles are used to derive the approximate relationship of c1 + c2ln(n) + c3n for the entropy of homo-oligo peptides with n residues, where c1, c2 and c3 are constants for a specific polypeptide chain. The relationship is tested in the range 1 ⩽ n ⩽ 34 against entropy data derived from electron structure calculations completed both at the Hartree-Fock and the density functional levels of theory. We have found that the above equation provides a good representation of the entropy of oligoglycine and oligoalanine model systems when they fold from an extended-like to a helical conformation.