The effect of various conditions of chromatin isolation on the nucleosomal structure of the isolated chromatin.

Chromatin from calf thymus isolated under hypotonic conditions in the presence of various agents was investigated by methods of electron microscopy prior to and after EDTA treatment. It is shown that the presence of chelating agents and, especially, the application of considerable mechanical forces in the course of isolation may cause damage to the nucleosomal structure of the chromatin. Moreover, sufficiently great mechanical forces are liable to destroy the structure of the chromatin nucleosomal fibres even when they are packed in structures of a higher order of organization of the chromatin.