The role of ionic hydration in the conformations of DNA in electrolytic solutions

The circular dichroism (CD) spectra of calf thymus deoxyribonucleic acid have been examined at 25°C over the wavelength range (215÷300) nm in aqueus solutions of LiCl, NaCl, KCl, and CsCl. The CD changes observed as the electrolyte concentration is varied have been correlated quantitatively with the magnitude of the hydration of the ions in these solutions (see a preceding paper). It is shown that specific cation effects present in this process correspond consistently to simple hydration properties of these same cations.