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Mechanically controlled DNA extrusion from a palindromic sequence by single molecule micromanipulation.
[Phys. Rev. Lett. 96 (18):188102 (2006)]
Alexandre Dawid, Fabien Guillemot, Camille Breme, Vincent Croquette, François Heslot
A magnetic tweezers setup is used to control both the stretching force and the relative linking number DeltaLk of a palindromic DNA molecule. We show here, in absence of divalent ions, that twisting negatively the molecule while stretching it at approximately 1 pN induces the formation of a cruciform DNA structure. Furthermore, once the cruciform DNA structure is formed, the extrusion of several kilo-base pairs of palindromic DNA sequence is directly and reversibly controlled by varying DeltaLk. Indeed the branch point behaves as a nanomechanical gear that links rotation with translation, a feature related to the helicity of DNA. We obtain experimentally a very good linear relationship between the extension of the molecule and DeltaLk. We use then this experiment to obtain a precise measurement of the pitch of B-DNA in solution : 3.61 +/- 0.03 nm/turn.Dans la même rubrique :
- DNA mechanics as a tool to probe helicase and translocase activity.
- Single molecule study of DNA conductivity in aqueous environment
- Unravelling the Mechanism of RNA-Polymerase Forward Motion by Using Mechanical Force.
- Single-molecule study of RuvAB-mediated Holliday-junction migration
- Dynamics of the DNA duplex formation studied by single molecule force measurements
- Rotational Drag on DNA : A Single Molecule Experiment
- Mechanical opening of DNA by micromanipulation and force measurement
- Unzipping DNA with Optical Tweezers : High Sequence Sensitivity and Force Flips
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