Interaction between aromatic residues. Molecular dynamics and ab initio exploration of the potential energy surface of the tryptophan-histidine pair

Empirical force fields for minimum searching in the tryptophan-histidine intermolecular energy surface were used. Fourteen principal minima were identified. For each of these structures the intermolecular energies were computed by using single point correlated ab initio calculation with a split valence and a correlation consistent valence double-zeta basis set. The force field determined complexes have much larger correlated ab initio stabilization energy than those reported in previous studies where a purely ab initio search method was used. The largest stabilization energy was found for a T-shaped complex stabilized by a NH ... N hydrogen bond. Stacked structures with superimposed and parallel-displaced imidazole rings were also found to be very stable.