Does the G center dot G(syn)(*) DNA mismatch containing canonical and rare tautomers of the guanine tautomerise through the DPT? A QM/QTAIM microstructural study

作者：Brovarets' Ol'ha O; Hovorun Dmytro M^*

来源：Molecular Physics, 2014, 112(23): 3033-3046.

DOI：10.1080/00268976.2014.927079

• sweeps of the energetic, electron-topological, geometric, polar and NBO parameters along the IRC
• the double proton transfer
• B3LYP and MP2
• syn- and anti-conformations
• QTAIM
• cooperativity of the H-bonds
• canonical and rare tautomers of the guanine

We have established that the asynchronous concerted double proton transfer (DPT), moving with a time gap and without stable intermediates, is the underlying mechanism for the tautomerisation of the G center dot G(syn)(*) DNA base mispair (C-1 symmetry), formed by the keto and enol tautomers of the guanine in the anti- and syn-configurations, into the G(*)center dot G(syn)(*) base mispair (C-1), formed by the enol and imino tautomers of the G base, using quantum-mechanical calculations and Bader's quantum theory of atoms in molecules. By constructing the sweeps of the geometric, electron-topological, energetic, polar and natural bond orbital properties along the intrinsic reaction coordinate of the G center dot G(syn)(*)<-> G(*)center dot G(syn)(*) DPT tautomerisation, the nine key points, that are critical for the atomistic understanding of the tautomerisation reaction, were set and comprehensively analysed. It was found that the G center dot G(syn)(*) mismatch possesses pairing scheme with the formation of the O6 center dot center dot center dot HO6 (7.01) and N1H center dot center dot center dot N7 (6.77) H-bonds, whereas the G(*)center dot G(syn)(*) mismatch - of the O6H center dot center dot center dot O6 (10.68) and N1 center dot center dot center dot HN7 (9.59 kcal mol(-1)) H-bonds. Our results highlight that these H-bonds are significantly cooperative and mutually reinforce each other in both mismatches. The deformation energy necessary to apply for the G center dot G(syn)(*) base mispair to acquire the Watson-Crick sizes has been calculated. We have shown that the thermodynamically stable G(*)center dot G(syn)(*) base mispair is dynamically unstable structure with a lifetime of 4.1 x 10(-15) s and any of its six low-lying intermolecular vibrations can develop during this period of time. These data exclude the possibility to change the tautomeric status of the bases under the dissociation of the G center dot G(syn)(*) mispair into the monomers during DNA replication. Finally, it has been made an attempt to draw from the physico-chemical properties of all four incorrect purine-purine DNA base pairs a general conclusion, which claims the role of the transversions in spontaneous point mutagenesis.

• 出版日期2014-12-2