MEAN AND SINGLE-ION ACTIVITY COEFFICIENTS AND TRANSFERENCE DATA OF SODIUM SALT OF A DEOXYRIBONUCLEIC ACID IN AQUEOUS SOLUTION

The mean activity coefficient of the sodium salt of a deoxyribonucleic acid, NaDNA, in two- and three-component systems, i.e., NaDNA + H2O, and NaDNA + NaCl + H2O, was investigated by the emf method. The transference and related measurements were also carried out for the determination of the net valency and the transference number of DNA anions. The polymer charge fraction, f2p, was concentration insensitive, decreased with increasing concentration of added salt, and was larger in the denatured state than in the native one. The transference number of DNA anions in the NaDNA + H2O system was about 0.5, being insensitive toward the polymer concentration. The mean activity coefficient of NaDNA increased sharply with polymer concentration (0.0007 ~ 0.003 equiv 1.-1), indicating the presence of the strong short-range interactions between DNA molecule and solvent water. A similar tendency was also noticed for the single-ion activity coefficient of DNA anions. The single-ion activity coefficient of gegenions slightly decreased with polymer concentration. © 1969, American Chemical Society. All rights reserved.