Journal archive  2010  #3 May-June

QUANTUM-CHEMICAL INVESTIGATION OF TAUTOMERIZATION WAYS

OF WATSON-CRICK DNA BASE PAIR GUANINE?CYTOSINE
 

O. O. Brovarets’, D. M. Hovorun

Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine, Kyiv;

 Institute of High Technologies of Taras Shevchenko Kyiv National University, Ukraine;

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Summary


A novel physico-chemical mechanism of the Watson-Crick DNA base pair Gua·Cyt tautomerization Gua·Cyt*?Gua·Cyt?Gua*·Cyt (mutagenic tautomers of bases are marked by asterisks) have been revealed and realized in a pathway of sing­le proton transfer through two mutual isoener­getic transition states with Gibbs free energy of activation 30.4 and 30.6 kcal/mol and they are ion pairs stabilized by three (N2H…N3, N1H…N4 and O6+H…N4) and five (N2H…O2, N1H…O2, N1H…N3, O6+H…N4 and O6+H…N4) H-bonds accordingly. Stable base pairs Gua·Cyt* and Gua*·Cyt which dissociate comparably easy into monomers have acceptab­le relative Gibbs energies – 12.9 and 14.3 kcal/mol – for the explanation of the nature of the spontaneous transitions of DNA replication. Results are obtained at the MP2/6-311++G(2df,pd)//B3LYP/6-311++G(d,p) level of theory in vacuum approach.

Key words: spontaneous point mutations of DNA replication, transitions, mutagenic tautomers of DNA bases, mispairs, transition state, intermolecular hydrogen bonds, analysis of the electron density topology, DFT.

The original article in Ukrainian is available for download in PDF format.