Tautomeric shifts in DNA
and rare enol forms of T
& G [left and right] differ by a
spontaneous proton shift between the adjacent
O and N atoms. The molecular formula
does not change, only the configuration of bonds among
atoms: the keto and enol
forms are therefore tautomers
of each other.
The standard amino and rare imino
forms of A [middle] also differ by a
spontaneous tautomeric shift between the the adjacent N molecules. Standard amino
and rare imino forms of C
[not shown] differ in the same way.