Tautomeric equilibrium, stability, and hydrogen bonding in 2 '-deoxyguanosine monophosphate complexed with Mg2+

Publikace: JOURNAL OF PHYSICAL CHEMISTRY B 112, 150-157 Autoři: Kosenkov, D., Gorb, L., Shishkin, OV., Sponer, J., Leszczynski, J. Rok: 2008

Abstrakt

The tautomeric equilibrium and hydrogen bonding in nucleotide 2'-deoxyguanosine monophosphate that interacts with hydrated Mg2+ cation (4H(2)O center dot Mg[dGMP]) were studied at the MP2/cc-pVDZ//B3LYP/cc-pVDZ and B3LYP/aug-cc-pVTZ//B3LYP/cc-pVDZ levels of theory. The Mg2+ ion forms two inner-shell contacts with the nucleotide, similar to small phosphorylated molecules under physiological conditions. The presence of the phosphate group and the hydrated magnesium cation leads to a change in guanine tautomeric equilibrium of 4H(2)O center dot Mg[dGMP] in comparison to free guanine. The influence of the phosphate group and the magnesium cation on tautomeric equilibrium is larger in the anti conformation where the P=O -> Mg and Mg <- N7 coordinate bonds are formed. The canonical oxo form of guanine is more stable (by 6-8 kcal/mol) than the 06-hydroxo form in anti conformation. Thus, the interaction with Mg2+ ion is capable of further suppressing the likelihood of a spontaneous transient formation of the rare tautomer. In the syn conformation of 4H(2)O center dot Mg[dGMP], the interaction of the guanine nucleobase with the phosphate group and the magnesium cation is not as strong as in the anti conformation, and the relative stability of guanine tautomers is close to those in free guanine.