The response of DNA length and twist to changes in ionic strength.
We examine twist-stretch coupling of unconstrained DNA using polyelectrolyte theory as applied to a line-charge model along with published data on the ionic-strength dependence of the twist angle. We conclude that twist-stretch coupling is negative: environmental changes that stretch free DNA, unconstrained by externally applied pulling or twisting forces, are accompanied by unwinding of the double helix. We also analyze a helical model and conclude that the observed unwinding of the DNA helix when ionic strength is decreased is driven by radial swelling of the helix.
Department of Chemistry and Chemical Biology, Rutgers University, 610 Taylor Road, Piscataway, NJ, 08854-8087.
Gerald S
GS
Manning
D004247:DNA / Q000737:chemistry*; D009690:Nucleic Acid Conformation; D009994:Osmolar Concentration
D004247:DNA
DNA; ionic strength effects; mechanics; polyelectrolyte effects