The role of water structure in conformational changes of nucleic acids in ambient and high-pressure conditions

This review describes and summarizes data on the structure and properties o f water under normal conditions, at high salt concentration and under high pressure. We correlate the observed conformational changes in nucleic acids with changes in water structure and activity, and suggest a mechanism of c onformational transitions of nucleic acids which accounts for changes in th e water structure. From the biophysical, biochemical and crystallographic d ata we conclude that the Z-DNA form can be induced only at low water activi ty produced by high salt concentrations or high pressure, and accompanied b y the stabilizing conjugative effect of the cytidine O4' electrons of the C G base pairs.