Universal short-range ab initio atom-atom potentials for interaction energy contributions with an optimal repulsion functional form

The repulsion term in conventional force fields constitutes a major source of error. Assuming that this could originate from a too simple analytical functional form, we analyzed various analytical functions using ab initio exchange component values as a reference and obtained (alpha + beta R-1) exp(-gamma R) as the optimal form to represent the repulsion term. Universal exchange, delocalization, and electrostatic penetration potentials approximating the corresponding interaction energy components defined within hybrid variation-perturbation theory (HVPT) were derived using as a reference a training set of 660 biomolecular complexes. The electrostatic multipole term was calculated using cumulative atomic multipole moments, whereas correlation contribution including dispersion term and first-order correlation correction was estimated from non-empirical D-as functions derived by Pernal et al. The resulting non-empirical atom-atom potentials (NEAAP) were tested for several urokinase-inhibitor complexes yielding improved docking results.