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Updated: Feb 14, 2026
08:48
Stretching Short Sequences of DNA with Constant Force Axial Optical Tweezers
Published on: October 13, 2011
13.6K
Knots modify the coil-stretch transition in linear DNA polymers.
Beatrice W Soh1, Vivek Narsimhan2, Alexander R Klotz1
1Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA. pdoyle@mit.edu.
Soft Matter
|February 10, 2018
Summary
Knots in DNA molecules significantly speed up relaxation and alter their stretching behavior. Untying these knots can cause dramatic conformational changes, impacting polymer dynamics in elongational fields.
Area of Science:
- Polymer Physics
- Biophysics
- Materials Science
Background:
- Understanding polymer dynamics is crucial in various scientific fields.
- Knots in polymers can significantly alter their physical properties and behavior.
- Previous studies have explored polymer behavior in elongational fields, but the specific impact of knots requires further investigation.
Purpose of the Study:
- To investigate the relaxation dynamics of knotted polymers using single-molecule DNA experiments.
- To examine the steady-state behavior of knotted polymers in elongational fields.
- To quantify the effect of knots on polymer chain extension and relaxation times.
Main Methods:
- Single-molecule DNA experiments were conducted.
- Chain extension and extension fluctuations were measured as a function of strain rate for both unknotted and knotted DNA molecules.
- Data analysis involved collapsing curves using effective Weissenberg numbers and comparing with Rouse/Zimm scaling theories.
Main Results:
- The presence of a knot reduces a polymer molecule's relaxation time.
- Knots shift the coil-stretch transition to higher strain rates.
- Knotted polymer behavior can be collapsed onto unknotted curves by defining an effective Weissenberg number or using scaling theories.
Conclusions:
- Knots accelerate polymer relaxation and modify coil-stretch transitions.
- Knot untying near the coil-stretch transition can lead to abrupt conformational changes.
- The findings provide insights into the role of topological defects in polymer dynamics.
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