[Interaction of nucleic acid bases with water molecules and formation of mismatched nucleotide pairs].

The possibility of the inclusion of water molecules in the formation of mismatched nucleotide pairs was considered in relation to the mechanisms of point errors in template directed biosynthesis. Calculations of the intermolecular interaction energy for systems containing two bases and one water molecule were carried out by the method of atom-atom potential functions. There exist energy minima for each base pair, corresponding to a single N--H...O or N--H...N H-bond between the bases and H-bonding of the water molecule with both bases. The relative positions of glycosyl bonds in some of these minima are closer to those for Watson--Crick pairs, than the positions of minima for these pairs without water. For other minima, the H-bond formation between the water molecule and the two bases additionally stabilizes the relative base position in wobble-pairs with two H-bonds between the bases. The base and water positions in energy minima are compared with the positions in some pairs proposed on the basis of NMR and X-ray data for double helical oligonucleotides.