[Hydrodynamic and optical behavior of DNA molecule in the range of high ionic strength]

The hydrodynamic and optical properties (intrinsic viscosity and optical anisotropy of DNA) have been studied at the high ionic strength mu greater than or equal to 1 M. It has been shown that the effective volume of DNA molecule doesn't depend of mu when mu greater than or equal to 1 M. In these conditions the electrostatical interactions in DNA disappear. But thermodynamic excluded volume effects do not depend on mu and play also an important role in this range of mu (mu greater than or equal to 1 M). It has been concluded that the condensation of DNA in solutions of high salt concentration is the result of local denaturation of DNA. It has been shown that the optical anisotropy of DNA increases drastically at mu congruent to 2 M but the persistence length of DNA does not change under these conditions.