Table 5.

The hydrogen-π interaction energies between His and aromatic amino acids in gas phase

	B3LYP/6-31+G(d,p)		CCSD/6-31+G(d,p)
a His	Energy b	Length c	Energy b	Length c
Imid-Phe	−2.735	2.594	−5.663	2.594
Imid-Tyr	−2.599	2.578	−5.637	2.578
Imid-Trp	−3.679	2.548	−7.907	2.548

^a Histidine (His) is simplified as the aromatic motif imidazole (Imid).

^b Energies are in kcal/mol, calculated by using CCSD/6-31+G(d,p) method.

^c The distance between two π-planes, in angstrom (Ǻ ).