Native and reconstituted chromosome fiber fragments.

The structure of hen erythrocyte chromatin fibers was studied with the electron microscope. Chromatin fiber fragments with a length of about 5,000 A and an average diameter of 320 A are composed of 13 globular subunits (superbeads) which contain different numbers of nucleosomes. Their number average corresponds to 17 nucleosomes. - The interaction of lysine-rich histones with nucleosome chains was investigated by reconstitution experiments and was found to be semi-cooperative.