O. O. Brovarets’

Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine, Kyiv;
Research and Educational Center “State Key Laboratory of Molecular and Cell Biology”, Kyiv, Ukraine;
Institute of High Technologies, Taras Shevchenko National University of Kyiv, Ukraine;
e-mail: brovarets@list.ru

At the MP2/6-311++G(2df,pd)//B3LYP/6-311++G(d,p) level of theory it was established for the first time, that the Löwdin’s G*·C* DNA base pair formed by the mutagenic tautomers can acquire, as the A·T Watson-Crick DNA base pair, four biologically important configurations, namely: Watson-Crick, reverse Watson-Crick, Hoogsteen and reverse Hoogsteen. This fact demonstrates rather unexpected role of the tautomerisation of the one of the Watson-Crick DNA base pairs, in particular, via double proton transfer: exactly the G·C→G*·C* tautomerisation allows to overcome steric hindrances for the implementation of the above mentioned configurations. Geometric, electron-topological and energetic properties of the H-bonds that stabilise the studied pairs, as well as the energetic characteristics of the latters are presented.