Dissociation of the protein components from chromatin by reversible modification with dimethylmaleic anhydride.

Modification of calf thymus chromatin with the protein reagent dimethylmaleic anhydride is accompanied by dissociation of histones and non-histone proteins. Gel electrophoresis of the released proteins and of those bound to the residual chromatin showed that histone H1 is dissociated more easily than the core histones (H2A, H2B, H3 and H4). These are apparently released in the proportion in which they are present in chromatin. After regeneration of the modified amino groups by incubation at pH 6.0, the released proteins are able to bind to the residual chromatin, under two different sets of reconstitution conditions, to form nucleosome-like structures.