Geometrical structures of the stationary points on the discovered pathways of the tautomerizations <i>via</i> the sequential proton transfer in the four biologically important A·Т DNA base pairs through the TSs with quasi-orthogonal oriented bases.

<p>Electronic ΔE_int (contribution of the total energy of the intermolecular specific contacts) and Gibbs free ΔG_int energies of the interaction (MP2/6-311++G(2df,pd)//B3LYP/6-311++G(d,p) level of theory, in kcal∙mol^-1), relative Gibbs free energies ΔG and electronic energies ΔE (in kcal∙mol^-1), imaginary frequencies <i>ν</i>_<i>i</i> at the TSs of the conformational transitions (MP2/aug-cc-pVDZ//B3LYP/6-311++G(d,p) level of theory in the continuum with ε = 1 at T = 298.15 К) are presented below complexes in brackets. Dotted lines indicate AH···B H-bonds and attractive A···B van der Waals contacts—their lengths H···B and A···B are presented in angstroms (for their more detailed physico-chemical characteristics see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0199044#pone.0199044.t002" target="_blank">Table 2</a>); carbon atoms are in light-blue, nitrogen—in dark-blue, hydrogen—in grey and oxygen—in red.