Viscosity of chromatin solutions increases with increasing ionic strength.

Increasing the ionic strength of rat liver chromatin solutions above 0.4 M causes increasing viscosity. This indicates transformation of the compact chromatin molecules to more elongated forms. In the range of 0.4-0.5 M ionic strength histone H1 is dissociating continuously from the chromatin and the quaternary structure chromatin unravels. At ionic strength higher than 0.5 M the viscosities of chromatin solutions are furthermore increasing due to structural deformation. Near 0.7 M ionic strength the core histones H2A and H2B begin to dissociate from the chromatin, and the opening of the nucleosome cores leads to increasing elongation of the chromatin molecules.