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Updated: Jul 8, 2026

Magnetic Tweezers for the Measurement of Twist and Torque
Published on: May 19, 2014
Link, twist, energy, and the stability of DNA minicircles
Kathleen A Hoffman1, Robert S Manning, John H Maddocks
1Department of Mathematics and Statistics, University of Maryland Baltimore County, Baltimore, MD 21250, USA. khoffman@math.umbc.edu
Abstract:
We describe how the stability properties of DNA minicircles can be directly read from plots of various biologically intuitive quantities along families of equilibrium configurations. Our conclusions follow from extensions of the mathematical theory of distinguished bifurcation diagrams that are applied within the specific context of an elastic rod model of minicircles. Families of equilibria arise as a twisting angle alpha is varied. This angle is intimately related to the continuously varying linking number Lk for nicked DNA configurations that is defined as the sum of Twist and Writhe. We present several examples of such distinguished bifurcation diagrams involving plots of the energy E, linking number Lk, and a twist moment m3, along families of cyclized equilibria of both intrinsically straight and intrinsically curved DNA fragments.
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