[B-A transition of DNA in aqueous solutions of nonelectrolytes]

Circular dichroism spectra of DNA in ternary water-nonelectrolyte solutions (water--ethanol--isopropanol and water--ethanol--dioxane) show that the decrease in water content at various nonelectrolyte ratios leads to the transition of DNA from B- to A-form. Water activity values in B-A transition region were calculated. The transition takes place within the range of water activity and DNA conformations have been plotted on triangular diagrams.