title: Studies on chromatin. IV. Evidence for a toroidal shape of chromatin subunits.
abstract: Electron microscopy of purified chromatin subunits (v-bodies [17] or nucleosomes [2] revealed a hole or at least a deep indentation in the globular nucleosome. A hole in the nucleosome was visualized using rotatory shadowing with platinum-palladium or more directly, by negative staining with sodium phosphotungstate. The diameter of the hole as measured from negatively stained samples is 10-25 A. The external diameter of the negatively stained nucleosome equals 75 +/- 15 A. Although most of the data are formally compatible with either a hole or a deep indentation in the nucleosome, some views of the particles in the negatively stained samples suggest a hole rather than an indentation. The possible significance of a toroidal structure of the chromatin subunit is discussed in the accompanying paper [3].
mesh_terms: D000818:Animals; D001665:Binding Sites; D002286:Carcinoma, Ehrlich Tumor / Q000032:analysis; D002501:Centrifugation, Zonal; D002843:Chromatin / Q000032:analysis / Q000648:ultrastructure*; D003852:Deoxyribonucleoproteins / Q000032:analysis*; D046911:Macromolecular Substances; D051379:Mice; D008854:Microscopy, Electron; D008970:Molecular Weight; D009690:Nucleic Acid Conformation; D009698:Nucleoproteins / Q000032:analysis*; D011485:Protein Binding; D011487:Protein Conformation
chemical_list: D002843:Chromatin; D003852:Deoxyribonucleoproteins; D046911:Macromolecular Substances; D009698:Nucleoproteins