Document Detail

Torsional motion and elasticity of the deoxyribonucleic acid double helix and its nucleosomal complexes.
MedLine Citation:
PMID:  6291596     Owner:  NLM     Status:  MEDLINE    
Torsional thermal oscillations of the DNA double helix within the electron paramagnetic resonance (EPR) time scale (10(-10)-10(-3) s) as indicated by a rigid, intercalating probe are much smaller in the spacer segment between nucleosomes in chromatin than in long, free DNA molecules. Still smaller DNA oscillation is indicated in intact nuclei and yet smaller if the nuclei have been treated with glutaraldehyde. The values of EPR measurements are not affected by the loading density of probe. If the probe were capable of substantial oscillations or movement different from that of the helix, those oscillations would be expected to dominate the spectra when movement of the helix is restrained. We conclude that the correlation time for torsional movement of free DNA inferred from EPR spectra is characteristic of the double helix and that there is no significant independent motion of the probe. The correlation time for the DNA double helix in molecules longer than approximately 500 base pairs is close to 30 ns, corresponding to an elastic constant of 1.5 X 10(-19) ergs cm for deformation by twisting. The motions observed in chromatin are consistent with a model in which spheres of 50-60-A radius are connected by simple elastic rods with the length of spacer DNA and the same elastic constant. The spin-labeled ethidium probe has been characterized in detail by nuclear magnetic resonance, infrared, fluorescence, and visible light spectroscopy. The binding equilibria are consistent with the hypothesis that strongly immobilized probe molecules are preferentially bound to spacer DNA.
I Hurley; P Osei-Gyimah; S Archer; C P Scholes; L S Lerman
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Biochemistry     Volume:  21     ISSN:  0006-2960     ISO Abbreviation:  Biochemistry     Publication Date:  1982 Sep 
Date Detail:
Created Date:  1983-01-07     Completed Date:  1983-01-07     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0370623     Medline TA:  Biochemistry     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  4999-509     Citation Subset:  IM    
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MeSH Terms
Binding Sites
Cell Fractionation
Cell Nucleus
Chemistry, Physical
DNA* / blood
Electron Spin Resonance Spectroscopy
Erythrocytes / cytology
Intercalating Agents
Nucleic Acid Conformation*
Physicochemical Phenomena
Spin Labels
Reg. No./Substance:
0/Chromatin; 0/Intercalating Agents; 0/Nucleosomes; 0/Spin Labels; 3546-21-2/Ethidium; 9007-49-2/DNA

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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