An interconversion of canonical nucleotide bases adenine, guanine and cytosine, exactly an inversion about a plane, and anisotropic inner rotation around exocyclic C-N bonds, and structural perturbations and the bases' profanation as well, have AMI and MNDO/H methods with an optimization of full structural parameters and agradient norm < 0.01.An mutually coordinated relaxational behaviour of essential structural parameters which describe valence bond configurations of amino group N atoms and neighbouring double C–N bonds were analysed. It was found that pπ-conjugation of an electron lone pair of an amino group nitrogen atom with a ring π-electron system is a main factor to determine structural-dynamical properties of exocyclic amino groups of canonical nucleotide bases, and moreover, of the bases themselves. Besides appreciable effects of other intramolecular interactions, namely intramolecular H-bonds (first of all of NH...N type), steric factors, and an electrostatic repulsion of electron lone pairs of neighbouring (endo- and exocyclic) nitrogen atoms as well, were estimated. They determine both nonequivalence of amino group NH bonds (as well as amino group ground-state orientation about a ring plane) and an anisotropy ofamino group inner rotation.