Cytosine, computational studies Watson-Crick pair with guanine

At the ambient temperature barrier of that size is easily overcome and, therefore, attachment of excess electron to the GC base pair (incorporated in DNA as the Watson-Crick configuration) should end up with the neutral radical of hydrogenated cytosine solvated by the anion of deprotonated guanine. Proton transfer induced by electron attachment has already been suggested in the past by the group of Sevilla within their computational [76] and experimental studies [77],... 

In this section, we present the results of computational studies of the five nucleic acid bases cytosine 13, guanine 14, adenine 15, thymine 16, and uracil 17. The canonical structures, those that are involved in the Watson-Crick base pairing within DNA, are drawn below. Other tautomers for each base can be energetically competitive with the canonical structure, and these other tautomers are invoked in some models of DNA mutations and anomalous DNA structures. The ensuing discussion focuses on the relative energies of the tautomers, in both the gas and solution phases. Structural changes that accompany this phase change are also noted. 

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