THE A-FORM OF DNA - IN SEARCH OF BIOLOGICAL ROLE (A REVIEW)

The first direct data on the A-DNA involvement in biological processes and structures have appeared only recently. Over the past four decade s, numerous investigations revealed the fine molecular structure of th is DNA conformation, the most important after B-form. The conditions p roviding for DNA transition in vitro from B-form to its A-form. were f ound and the effect of nucleotide sequence on the ability for such tra nsition became clear. By the present time the cooperative B-transition has been as well studied as the better known helix-to-coil transition . These physicochemical studies force one to think about the ''biology '' of A-conformation, and at the same time they provide experimental p ossibilities for detecting it in biological processes and living syste ms.