OF CHROMATIN SUBSTRUCTURE: t)BODIES

Spread chromatin fibers, from isolated eucaryotic nuclei, reveal linear arrays of spherical particles (o bodies), about 70 A in diameter, connected by thin filaments about 15 A wide. These particles have been observed in freshly isolated nuclei from rat thymus, rat liver, and chicken erythrocytes. In addition, v bodies can be visualized in preparations of isolated sheared chromatin, and in chromatin reconstructed from dissociating solvent conditions (i.e., high urea-NaCl concentration). As a criterion for perturbation of native chromatin structure low-angle X-ray diffraction patterns were obtained from nuclear pellets at different stages in the preparation of nuclei for electron microscopy. These results suggest that the particulate (v body) structures observed by electron microscopy may be closely related to the native configuration of chromatin.