title: Chromatin architecture: investigation of a subunit of chromatin by dark field electron microscopy.
abstract: Dark field scanning electron microscopy of unstained, unfixed samples of chromatin, histone-1-depleted chromatin, and nucleohistone has been used to identify an apparent subunit of chromatin, namely a disk-shaped structure we term the unit particle, which is probably about 135 A wide and 50 A thick in the hydrated state. The unit particles are found at rather uniform intervals along thin DNA-like fibers. Histone 1 depletion leads to a bimodal distribution of these spacings. Our observations suggest that the unit particle consists of a loop of nucleoprotein, perhaps around a histone core.
mesh_terms: D000818:Animals; D002417:Cattle; D002467:Cell Nucleus / Q000032:analysis / Q000648:ultrastructure; D002843:Chromatin / Q000032:analysis / Q000648:ultrastructure*; D002850:Chromatography, Gel; D006657:Histones / Q000032:analysis; D008854:Microscopy, Electron; D009698:Nucleoproteins / Q000032:analysis; D013950:Thymus Gland / Q000032:analysis
chemical_list: D002843:Chromatin; D006657:Histones; D009698:Nucleoproteins