Table 2.

Relative energy (ΔE/kcal.mol⁻¹) and equilibrium constants (K_eq) at 298 K calculated for the H1+H4 and H1+H4′ tautomeric equilibria of undamaged-DNA, O₂N–C8(G) and ONO–C8(G) adducts.

Adduct	Undamaged-DNA		ONO–C8(G)		O2N–C8(G)
	ΔE	Keq	ΔE	Keq	ΔE	Keq
Canonic	0.00		0.00		0.00
H1+H4	11.23	5.75 × 10−09	12.96	3.11 × 10−10	9.73	7.27 × 10−08
H1+H4′	17.37	1.80 × 10−13	20.71	6.50 × 10−16	17.48	1.52 × 10−13