[Effect of solvent structure on amide reaction with native DNA molecules. I. Aqueous mixtures of N,N-dimethylformamide and urea].

The influence of N,N-dimethylformamid (DMF) and urea (U) on the conformation of the native DNA molecule has been studied by methods of flow birefringence and viscometry. The investigations have been performed over a wide range of amides and supporting electrolyte concentrations. An essentially different influence of small additions of DMF and U on the macromolecule's dimensions was observed.