X-ray studies on “Native” chromatin

Abstract

X-ray diffraction photographs have been obtained of unoriented gels of chromatin prepared by brief digestions of rat liver nuclei with micrococcal nuclease. At low concentration (20%, w/w) this material gives a sharp pattern of peaks at apparent orders of about 110 Å, separated by clear spaces; the sharpness and relative intensities of the different peaks distinguish it from the diffraction patterns obtained from chromatin prepared by older methods involving shear. The structure which gives rise to this sharp diffraction pattern is correlated with solenoidal structures described in a recent electron microscope study (Finch & Klug, 1976), and it is proposed that the X-ray reflections arise from the 110 Å spacing between turns of the solenoids, rather than from the spacing of nucleosomes along the nucleofilament.