Table 4.

Interaction energies, in kcal/mol, of the base pairs X–Y, X–Z and Y–Z that can be obtained by fragmentation of the base triplets X–Y–Z

Triplet	Pair	Isolated pair	Pair in the optimized triplet	Pair in the X-ray triplet
U8–A14–A21	8–14	−15.0	−14.6	−15.8
	8–21		0.6	−2.4
	14–21		−8.5	−1.2
A9–U12–A23	9–12		−0.3	−1.3
	9–23	−11.1	−10.7	−8.8
	12–23	−13.8	−13.8	−14.3
m2G10–C25–G45	10–25	−27.1	−26.7	−30.8
	10–45		−5.8	−7.3
	25–45		−1.0	−0.4
G13–G22–m7G46	13–22	−26.8	−25.6	−30.7
	13–46		4.0	1.5
	22–46	−34.2	−32.5	−36.8

The ‘Isolated Pair’ column reports the interaction energy of the isolated and optimized base pair. These calculations have been performed for base pairs with at least two H-bonds. The ‘Optimized Triplet’ column reports the interaction energy between base pairs in the geometry they have in the optimized triplet. The ‘X-ray Triplet’ column reports the interaction energy between base pairs in the geometry they have in the X-ray structure.