In this paper we describe a detailed investigation of the reconstitution of nucleosome cores from poly (dA-dT) and the octamer of histones. We also attempted the reconstitution from the copolymers poly dA.poly dT, poly dG.poly dC and poly (dG-dC). The repeat of the reconstituted chromatin fibre is discussed. The micrococcal nuclease released poly (dA-dT) core particle is found to contain a considerably narrower DNA size distribution that of the native random DNA nucleosome core (12). In addition we have succeeded in obtaining small crystals of the poly (dA-dT) nucleosome core. The DNAase I digestion pattern of the poly (dA-dT) containing nucleosome core is presented. The periodicity of DNAase I cutting sites is found to be about 10.5 bases and is similar to that of the native nucleosome core (12, 13).
