Deprotonated carboxylic group of amino acids transforms adenine into its rare prototropic tautomers.

By UV spectroscopic data for anhydrous DMSO solutions and ab initio HF/6-31G** calculations in vacuum it was shown for the first time that deprotonated amino acid carboxylic group is able to change tautomeric state of a nucleotide base, exactly to convert the N9H ground-state prototropic tautomer of adenine into the N7H and N1H rare ones.