title: Characterization of SV40 chromatin by mass determination on STEM.
abstract: Direct mass determination of purified SV40 minichromosomes was obtained by scanning transmission electron microscopy. Twenty to thirty percent of the minichromosomes were found with an Mr of 6.9 +/- 0.4 X 10(6). The rest of the molecules formed a spread Mr distribution ranging from 7.3 X 10(6) to 9.5 X 10(6) due possibly to different contents of the virus-coded proteins, mainly VP1. The apparent mass histogram of individual SV40 nucleosomes presents three maxima at Mr 2.1 X 10(5), 2.6 X 10(5) and 3.1 X 10(5) that could correspond to partially unravelled nucleosomes, complete nucleosomes and complete nucleosomes with the addition of VP1. Beaded structures with a higher mass were also measured; some were found at either side of the open nucleosome-free region.
mesh_terms: D002843:Chromatin / Q000032:analysis / Q000648:ultrastructure*; D004279:DNA, Viral / Q000032:analysis; D008855:Microscopy, Electron, Scanning; D008970:Molecular Weight; D009707:Nucleosomes / Q000648:ultrastructure; D013539:Simian virus 40 / Q000648:ultrastructure*; D014764:Viral Proteins / Q000032:analysis
chemical_list: D002843:Chromatin; D004279:DNA, Viral; D009707:Nucleosomes; D014764:Viral Proteins