The effect of oxidation on the stability of G:C base pair: a MP2 study

The base-pairing energies of eleven oxidized G:C base pairs were characterized by Møller–Plesset perturbation theory. The analysis was focused on the base pairs consisting of guanine and one of the following cytosine derivatives: G:C1 (5-hydroxycytosine); G:C2 (5-hydroxyuracil); G:C3 (5,6-dihydroxy-cytosine); G:C4 (5,6-dihydroxy-uracil); G:C5 (cytosine glycol);G:C6 (isodialuric acid); G:C7 (uracil glycol), and the base pairs between cytosine and one of the following guanine derivatives: G8:C (8-oxo-guanine); G9:C (6-enol-8-keto-guanine); G10:C (xantho-sine); and G11:C (8-hydroxy-guanine). Full geometry optimizations have been performed for the studied complexes by MP2 method. The interaction energies were corrected for the basis-set superposition error (BSSE), using the full Boys-Bernardi counterpoise correction scheme. The results obtained show that the interaction energies of the base pairs decrease in the following order: G8:C > G:C5 ~ G:C1 > G:C3 ~ G:C ~ G11:C > G:C2 > G:C4 > G:C7 > G:C6 > G10:C > G9:C.