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;
Using the methods of non-empirical quantum chemistry 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 Hoogsteen, reverse Hoogsteen, Watson-Crick and reverse Watson-Crick configurations of the A·T and G·C DNA base pairs are isoelectronic and isomorphic structures with similar dynamic properties. Based on these results, non-ionisation mechanism of the Hoogsteen «breathing» of the G·C DNA base pair, namely transformation of the tautomerised (L?wdin’s) G*·C* base pair with Watson-Crick geometry into the Hoogsteen electroneutral G*·C* H base pair stabilized by the three O6H…N4, N3H…N7 and C8H…O2 H-bonds, was postulated. It is suggested that such scenario activates only in those cases, when DNA is not located in aqueous solution, but works together with proteins and cytosine protonation at the N3 atom is precluded.
Key words: Watson-Crick, reverse Watson-Crick, Hoogsteen and reverse Hoogsteen A·T DNA base pairs; Hoogsteen “breathing” of the G·C DNA base pair; intermolecular hydrogen bonds; quantum-chemical calculations; topological analysis of the electron density.
The original article in Ukrainian is available for download in PDF format.
© The Ukrainian Biochemical Journal