“…However, up until recently it was considered that only a few unusual tautomers existed for the G·C Watson-Crick nucleobase pair (Pous et al, 2008 ; Alvey et al, 2014 ; Brovarets' and Hovorun, 2014a ; Nikolova et al, 2014 ; Poltev et al, 2016 ; Szabat and Kierzek, 2017 ; Brovarets' et al, 2019a , b ; Srivastava, 2019 ). In particular, tautomerization via the double proton transfer (DPT) has been carefully investigated in the reverse Löwdin G * ·C * (rWC), Hoogsteen (H) G * ′·C * (H), and reverse Hoogsteen G * ′·C * (rH) base pairs (Brovarets' et al, 2019b ), leading to the novel structures: G· (rWC), C(rWC), G *′ N2 ·C(rWC), C(H), and G *′ N7 ·C(rH).…”