Structure of nucleosome core particles of chromatin

Abstract
Crystals have been obtained of nucleosome cores and analysed by X-ray diffraction and electron microscopy. The core is a flat particle of dimensions about 110 × 110 × 57 Å, somewhat wedge shaped, and strongly divided into two ‘layers’, consistent with the DNA being wound into about 1¾ turns of a fiat superhelix of a pitch about 28 Å. The organisation of the DNA can be correlated with the results of enzyme digestion studies. A change in the screw of the DNA double helix on nucleosome formation can be deduced.