A Peptide Potential Based on a Bond Dipole Representation of Electrostatics

A potential based on a bond dipole representation of electrostatics is reported for peptides. Different from those popular force fields using atom-centered point-charge or point-multipole to express the electrostatics, our peptide potential uses the chemical bond dipole-dipole interactions to express the electrostatic interactions. The parameters for permanent and induced bond dipoles are derived from fitting to the MP2 three-body interaction energy curves. The parameters for van der Waals are taken from AMBER99sb and further refined from fitting to the MP2 stacking interaction energy curve. The parameters for bonded terms are taken from AMBER99sb without any modification. The scale factors for intramolecular dipole-dipole interactions are determined from reproducing the highly qualified ab initio conformational energies of dipeptides and tetrapeptides. The resulting potential is validated by use to evaluate the conformational energies of polypeptides containing up to 15 amino acid residues. The calculation results show that our peptide potential produces the conformational energies much closer to the famous density functional theory M06-2X/cc-pVTZ results than the famous AMBER99sb and AMOEBAbio18 force fields. Our potential also produces accurate intermolecular interaction energies for hydrogen-bonded and stacked dimers. We anticipate the peptide potential proposed here could be helpful in computer simulations of polypeptides and proteins.