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The response of DNA length and twist to changes in ionic strength
Author(s) -
Manning Gerald S.
Publication year - 2015
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.22585
Subject(s) - ionic strength , twist , chemistry , helix (gastropod) , polyelectrolyte , ionic bonding , dna , coupling (piping) , chemical physics , swelling , crystallography , biophysics , composite material , materials science , geometry , ion , polymer , biochemistry , ecology , mathematics , organic chemistry , aqueous solution , snail , biology
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. © 2014 Wiley Periodicals, Inc. Biopolymers 103: 223–226, 2015.