Strength of hydrogen bonds in ? helices

The intramolecular helix backbone >C(DOUBLE BOND)O---H—N< hydrogen bonding energies in poly(L-alanine) α helices have been estimated both in vacuum and in an aqueous environment using the parameter sets of five of the most commonly used force fields for modeling biomolecules, namely AMBER, CHARMM, ECEPP, GROMOS, and OPLS. The relative capabilities of these force fields in describing the H-bonding interactions with different dielectric continuum models have been assessed. A modified Hingerty–Lavery function is proposed for the treatment of electrostatic interactions of biomolecules in an aqueous environment. The helix backbone H-bonding energies predicted by this function (∼−1 kcal/mol) correspond closely with the experiment.