Table 5.

The delocalization energies of the amino acid analog pairs involved in n→σ^* interactions^*

Analog Pairs	Edeloc (kcal/mol)				ns				np
	ns→σ*	np→σ*	Total	Occup.	s (%)	p (%)	d (%)	Occup.	s (%)	p (%)	d (%)
Asp_Phe_1	1.45	3.58	5.03	1.97640	61.70	38.28	0.02	1.91797	0.31	99.64	0.06
Asp_Trp_3	1.94	3.44	5.38	1.97585	61.76	38.22	0.02	1.91707	0.29	99.66	0.06
Asp_Tyr_4	3.55	0.29	3.84	1.97385	61.89	38.09	0.02	1.92029	0.00	99.94	0.06
Glu_Phe_5	3.00	4.14	7.14	1.97522	61.20	38.78	0.02	1.91665	0.76	99.18	0.06
Glu_Tyr_3	1.55	3.59	5.08	1.97642	61.76	38.22	0.02	1.91695	0.14	99.80	0.06
Ser_Glu_2	6.74	22.8	29.54	1.96815	55.53	44.45	0.02	1.90472	6.75	93.21	0.04
Ser_Asn_1 (O-H···O)	1.63	5.50	7.13	1.97611	59.15	40.83	0.02	1.90207	0.22	99.71	0.07
Ser_Asn_1 (N-H···O)	1.92	1.91	3.83	1.98275	44.82	55.16	0.03	1.96724	1.60	98.37	0.03
Ser_Asn_2	4.90	0.00	4.9	1.98104	48.20	51.78	0.02

^*E_deloc is calculated through NBO analysis. n_s and n_p are the degenerated orbitals of lone pairs of the carboxyl oxygen, σ^* is the antibonding orbital of H-D (D is the hydrogen bond donor). For each lone pair degenerated orbital, the occupancy and the s, p and d components are shown. All energies are in kcal/mol.