Viscosity of sodium thymonucleate

The viscosity of sodium thymonucleate solutions shows some peculiar characteristics. There is considerable reduction in viscosity of a dilute solution of sodium thymonucleate in presence of neutral salts and alkali. Greenstein and Jenrette, as also Tennent and Vilbrandt, have postulated the reversible depolymerization of the nucleic acid molecule in presence of neutral salt and alkali. From the measurement of dissymmetry by the light-scattering method, Smith and Sheffer have shown that the nucleic acid molecules coil up in solution in presence of neutral salts. The peculiar viscosity effect may similarly be attributed to coiling and uncoiling of the molecules rather than to reversible depolymerization in presence of salt. Since nucleic acid is a long-chain molecule with the acid groups distributed along the chain, it is to be expected that the sodium salt of the acid will behave as a polyelectrolyte, according to Fuoss's contention, in solution, and the peculiar viscosity characteristics may be explained on the assumption of a coiling-uncoiling effect with the extent of dissociation. Viscosity measurements of sodium thymonucleate solution have been under-taken in this laboratory, and it will be evident from the accompanying graph that the reduced viscosity (ηsp/c) increases as the solution is diluted, a result contrary to that for neutral polymers and similar to that of polyelectrolytes