Magnetic torque tweezers: measuring torsional stiffness in DNA and RecA-DNA filaments.

Lipfert, Jan; Kerssemakers, Jacob W J; Jager, Tessa; Dekker, Nynke H · Nat Methods · 2010

basic_science · Level V

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Abstract

We introduce magnetic torque tweezers, which enable direct single-molecule measurements of torque. Our measurements of the effective torsional stiffness C of dsDNA indicated a substantial force dependence, with C = approximately 40 nm at low forces up to C = approximately 100 nm at high forces. The initial torsional stiffness of RecA filaments was nearly twofold larger than that for dsDNA, yet at moderate torques further build-up of torsional strain was prevented.

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