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Updated: Feb 10, 2026

Stretching Short Sequences of DNA with Constant Force Axial Optical Tweezers
Published on: October 13, 2011
Motion of Knots in DNA Stretched by Elongational Fields
Alexander R Klotz1, Beatrice W Soh1, Patrick S Doyle1
1Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02142, USA.
Abstract:
Knots in DNA occur in biological systems, serve as a model system for polymer entanglement, and affect the efficacy of modern genomics technologies. We study the motion of complex knots in DNA by stretching molecules with a divergent electric field that provides an elongational force. We demonstrate that the motion of knots is nonisotropic and driven towards the closest end of the molecule. We show for the first time experimentally that knots can go from a mobile to a jammed state by varying an applied strain rate, and that this jamming is reversible. We measure the mobility of knots as a function of strain rate, demonstrating the conditions under which knots can be driven towards the ends of the molecule and untied.
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