Physicochemical properties of salt-soluble, unsheared chromatin. Hydrodynamic model calculations supporting a double-fibrillar structure.
Hydrodynamic model calculations of a special, salt-soluble chromatin fraction were performed on the basis of former experimental data. Using the models of an extended helix and of a cylinder fitted to this helix we conclude that in 0.1 M (NH4)2SO4 this chromatin has the conformation of a nucleosome double-fiber helix, i.e. a structure in which two helices share a common axis. Besides this helical structure, a stretched, linear double-fibrillar form can be derived from sedimentation data on the basis of a simple cylinder model. From the kinetic behaviour of experimental sedimentation coefficients which decrease shortly after chromatin extraction a conformational transition of the helical to the fibrillar form is postulated. At 0.2 M (NH4)2SO4 where histone H1 is released, these double-structures are supposed to dissociate into two single molecules with similar dimensions.
D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002843:Chromatin / Q000032:analysis*; D008027:Light; D008954:Models, Biological; D008970:Molecular Weight; D011487:Protein Conformation; D012542:Scattering, Radiation; D012995:Solubility
D002843:Chromatin