The prototropic tautomerism of nitrogen bases: a new insight into the old problem.

The summary is made of the series of theoretical calculations performed by the semiempirical quantum-chemical AM1 method of physico-chemical features of prototropic tautomerism of nucleotide bases with full optimization of all parameters. Applying of nontraditional approach based on the view that the highest possible number of prototropic tautomers of bases are determined by an overall quantity of protons and electron lone pairs of proton acceptor atoms, the success was achieved in ascertaining that, as regards prototropic tautomerism, nucleotide bases are more mobile structures (prototropic tautomerism of nucleotide bases has a molecular-zwitterionic character involving carboprotons as well) than it was assumed earlier. A biological significance of the data obtained, which are generalized and may be extended from the authors point of view to more wide range of objects, amino acids included.