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Measurement of the Torque on a Single Stretched and Twisted DNA Using Magnetic Tweezers

2009; American Physical Society; Volume: 102; Issue: 7 Linguagem: Inglês

10.1103/physrevlett.102.078301

1092-0145

Francesco Mosconi, Jean‐François Allemand, David Bensimon, Vincent Croquette,

Nanopore and Nanochannel Transport Studies

We deduced the torque applied on a single stretched and twisted DNA by integrating the change in the molecule's extension with respect to force as it is coiled. While consistent with previous direct measurements of the torque at high forces (F>1 pN), this method, which is simple and does not require a sophisticated setup, allows for lower force estimates. We used this approach to deduce the effective torsional modulus of DNA, which decreases with force, and to estimate the buckling torque of DNA as a function of force in various salt conditions.