Electron microscope sections have been cut of chicken red blood cell nuclei by a novel procedure that produces zones of material below 100 Å in thickness. After fixing and staining, electron dense structures are observed that have dimensions closely correlating with those determined for nucleosomes. These structures appear as wedge-shaped or as circular objects with a diameter of approximately 90-100 Å. Five to eight of these objects are arranged in a spiral around a central core giving rise to a 250-300 Å structure which may represent a superbead or a cross section of a solenoidal fibre.
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