PMR study of N6, N6-dimethyladenosine conformations under high pressure.

High hydrostatic pressure affects in various ways the reactivity and the stability of biogenic macromolecules [ 11. Pressures of several hundred bars reduce or increase enzymic activity [2-41. Proteins are usually irreversibly denaturated by pressures in excess of 1 kbar. On the other hand, calf thymus DNA is stabilized by increased pressure [5]. In general, an increase in pressure shifts an equilibrium in the direction reducing the sum of the partial molar volumes. In a macromolecule, such volume changes result from several interactions acting toward or again each other. It is, therefore, necessary to study the influence of pressure on the conformational equilibria of smaller molecules. In continuation of our studies on the conformations of the common purine@)-nucleosides [6-81 and their analogs [9-l 1 J, we have analysed the pressure dependence of the conformational equilibria of I@fl-dimethyladenosine.