[Conformation of the DNA molecule in alcohol-water solvents]

The influence of different alcohol-water solvents on the conformation of the native DNA molecule has been studied by the methods of flow birefringence and viscometry. The experiments have shown, that a certain content of the organic component induces a cooperative transition in the tertiary structure of the DNA molecule. The conformational transitions in the tertiary structure of DNA have been observed at low alcohol concentrations, corresponding to the desruption of the ordered spatial water structure and are caused by the alteration of the intermolecular interactions between the DNA and solvent molecules. The alcohol concentrations, corresponding to the observed transition, as well, as relative decrease of the intrinsic viscosity of DNA, depend on the chain length and branching of the hydrocarbon portion of the alcohols. The data on the optical anisotropy of the DNA molecule testify that the secondary structure of the latter doesn't change in a wide range of the alcohol concentrations.