Water and Nucleic Acids

Abstract

Throughout this text, the importance of water surrounding nucleic acids has been emphasized. Water is not just a medium to keep the solutes dissolved. It interacts and, in the case of macromolecules, is mainly responsible for the stabilization of secondary and tertiary structure (525,1146–1148). This holds for proteins and even more so for nucleic acids because phosphate ⋯ phosphate electrostatic repulsion is diminished by the high dielectric constant of water and hydrated counterions. Moreover, the bases self-assemble into ordered structures, and this is partly due to hydrophobic forces which again involve the active participation of water molecules. The degree of hydration of DNA plays a key role in its conformation; high relative humidity favors the B form and reduced humidity or increased ionic strength leads to a transition from the B form to C-, A-, and, if sequence permits, D- and Z-DNA.