By how many tautomerisation routes the Watson-Crick-like A•C* DNA base mispair is linked with the wobble mismatches? A QM/QTAIM vision from a biological point of view

Here for the first time we present four novel routes of the tautomerisation via the sequential DPT that links biologically important A center dot C*(WC) DNA base mispair with Watson-Crick (WC) geometry and wobble (w) A*center dot C*(w), A center dot C*(O2)(w), A*center dot C*(w (1)) and A center dot C(w (aSyen)) mismatches, pursuing the goal of estimation of their contribution into the transition mutations during DNA biosynthesis. These processes occur without opening of the pairs and are accompanied by the substantial changes in their geometry. A detailed analysis of these pathways leads to an identification of the A center dot C*(WC)a dagger"A*center dot C*(w) tautomerisation route as the most suitable among these processes from the point of view of the spontaneous point mutagenesis, since it proceeds via the time that is significantly less than the time used by the replicative DNA-polymerase for the incorporation of one incoming nucleotide into the synthesised DNA double helix. This non-dissociative transition occurs through the planar, highly stable, zwitterionic transition state and dynamically unstable intermediate A(+)center dot C-(w) ion pair and is accompanied by the consistent rearrangement of the 10 unique patterns of the specific intermolecular interactions, among which there are from 2 to 4 AH center dot center dot center dot B H-bonds and 2 loosened A-H-B covalent bridges. Basic physico-chemical properties of this mutual tautomeric transformation, which is internally inherent to the A center dot C*(WC) and A*center dot C*(w) base mispairs, are documented, and its possible biological assignment is discussed here.