Table 2.

Summary of molecular orbital calculations^a

NBO donor (LP)	NBO acceptor (π*)	Interaction energy (kcal/mol) for EFdA conformation
		North	South
O4	4′-CC	1.63	1.25
3′-O	4′-CC	0.71	0.0
Total energy		2.34	1.25

^aLP, lone pair; π*, antibonding orbital.