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Updated: Apr 21, 2026

Stretching Short Sequences of DNA with Constant Force Axial Optical Tweezers
Published on: October 13, 2011
Mechanical transition in a highly stretched and torsionally constrained DNA
Janusz Strzelecki1, Lukasz Peplowski1, Robert Lenartowski2
1Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziądzka 5, 87-100 Toruń, Poland.
Abstract:
We show results of our high force (up to 1.8 nN) atomic force microscopy force spectroscopy measurements of a double stranded DNA. We have found that the force spectra of torsionally constrained molecules display a small plateau occurring at a force of approximately 1 nN. This transition is absent in molecules with rotational freedom. Based on all-atom molecular dynamics simulations, we suggest that this plateau is a result of reducing the diameter of a double helix through extreme stretching. The simulation suggests that the molecule is forced into a form resembling an underwound P-DNA, with bases protruding outside of the backbones. These results broaden our understanding of the fundamental aspects of DNA nanomechanics.
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