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-ζ 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.