An analytic potential energy function for the amide-amide and amide-water intermolecular hydrogen bonds in peptides

An analytic potential energy function is proposed and applied to evaluate the amide-amide and amide-water hydrogen-bonding interaction energies in peptides. The parameters in the analytic function are derived from fitting to the potential energy curves of 10 hydrogen-bonded training dimers. The analytic potential energy function is then employed to calculate the N-H...O=C, C-H...O=C, N-H...OH2, and C=O...HOH hydrogen-bonding interaction energies in amide-amide and amide-water dimers containing N-methylacetamide, acetamide, glycine dipeptide, alanine dipeptide, N-methylformamide, N-methylpropanamide, N-ethylacetamide and/or water molecules. The potential energy curves of these systems are therefore obtained, including the equilibrium hydrogen bond distances R(O...H) and the hydrogen-bonding energies. The function is also applied to calculate the binding energies in models of beta-sheets. The calculation results show that the potential energy curves obtained from the analytic function are in good agreement with those obtained from MP2/6-31+G** calculations by including the BSSE correction, which demonstrate that the analytic function proposed in this work can be used to predict the hydrogen-bonding interaction energies in peptides quickly and accurately.