Knots modify the coil–stretch transition in linear DNA polymers
Author(s)Narsimhan, Vivek; Soh, Beatrice W; Klotz, Alexander; Doyle, Patrick S
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We perform single-molecule DNA experiments to investigate the relaxation dynamics of knotted polymers and examine the steady-state behavior of knotted polymers in elongational fields. The occurrence of a knot reduces the relaxation time of a molecule and leads to a shift in the molecule's coil-stretch transition to larger strain rates. We measure chain extension and extension fluctuations as a function of strain rate for unknotted and knotted molecules. The curves for knotted molecules can be collapsed onto the unknotted curves by defining an effective Weissenberg number based on the measured knotted relaxation time in the low extension regime, or a relaxation time based on Rouse/Zimm scaling theories in the high extension regime. Because a knot reduces a molecule's relaxation time, we observe that knot untying near the coil-stretch transition can result in dramatic changes in the molecule's conformation. For example, a knotted molecule at a given strain rate can experience a stretch-coil transition, followed by a coil-stretch transition, after the knot partially or fully unties.
DepartmentMassachusetts Institute of Technology. Department of Chemical Engineering
Royal Society of Chemistry (RSC)
Soh, Beatrice W. et al. “Knots Modify the Coil–stretch Transition in Linear DNA Polymers.” Soft Matter 14, 9 (2018): 1689–1698 © 2018 Royal Society of Chemistry
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