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Structural conformations of nucleosomes at low ionic strength from flow birefringence and intrinsic viscosity
Author(s) -
Harrington Rodney E.
Publication year - 1981
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1981.360200408
Subject(s) - chemistry , ionic strength , flow birefringence , birefringence , rotational diffusion , viscosity , anisotropy , particle (ecology) , nucleosome , intrinsic viscosity , ionic bonding , chemical physics , diffusion , crystallography , molecular physics , biophysics , chromatin , thermodynamics , dna , ion , optics , molecule , polymer , physics , biochemistry , organic chemistry , oceanography , aqueous solution , geology , biology
The shape and structure of nucleosomes from chicken erythrocytes as a function of ionic strength in solution using the complementary techniques of streaming birefringence and intrinsic viscosity were studied. As characterized by both rotational diffusion and optical anisotropy, three distinct conformational levels were observed. Above ∼8 m M ionic strength, the particles are oblate ellipsoids or discs with axial ratio of ∼0.5. Below ∼8 m M , two structural variants were observed: a relatively more symmetrical particle which exists between ∼8 and ∼0.5 m M , and a relatively asymmetric structure below ∼0.5 m M . Birefringence data are consistent with an “opened clamshell” type of model for the first of these and with a somewhat compacted form of linear DNA for the latter. The results provide insights into possible conformational states of transcriptionally active chromatin at the nucleosomal level of structure.