A quantum chemical study of the effect of Na+ on the hydrogen bonds in the adenine-thymine base-pair.

It is shown, by quantum chemical calculations, that an Na+ located in the neighborhood of the adenine thymine base-pair can dissociate the hydrogen bonds in it. However, a water molecule placed between Na+ and the base-pair would provide perfect protection for the hydrogen bonds. The suggestion is put forward that a hydrophobic carcinogen (for example) could perturb sufficiently the water structure around DNA to allow Na+ to penetrate to molecular distance from the base-pair. This could result in the 'breaking' of hydrogen bonds and, eventually, irregular cell division.