DPT tautomerisation of the wobble guanine·thymine DNA base mispair is not mutagenic: QM and QTAIM arguments.

We have shown for the first time, connecting QM methods with QTAIM analysis and using the methodology of the sweeps of the energetical, electron-topological and geometrical parameters, that the tautomerisation of the wobble guanine·thymine (wG·T) DNA base mispair into the wG()·T() base mispair induced by the double proton transfer (DPT), which undergoes a concerted asynchronous pathway, is not mutagenic. The wG·T → wG()·T() DPT tautomerisation does not result in the transition of the G base into its mutagenic tautomeric form G() able to mispair with the T base within the Watson-Crick base pairing scheme. This observation is explained by the so-called quantum protection of the wG·T DNA base mispair from its mutagenic tautomerisation - the dynamical non-stability of the tautomerised wG()·T() base mispair and significantly negative value of the Gibbs free energy of activation for the reverse reaction of the wG·T → wG()·T(*) DPT tautomerisation.