Probing the salt dependence of the torsional stiffness of DNA by multiplexed magnetic torque tweezers

Probing the salt dependence of the torsional stiffness of DNA by multiplexed magnetic torque tweezers

Kriegel, Franziska (Ludwig Maximilians University)
Ermann, Niklas (Ludwig Maximilians University)
Forbes, R.J.G. (TU Delft BN/Nynke Dekker Lab)
Dulin, D. (TU Delft BN/Nynke Dekker Lab; Friedrich-Alexander-Universität Erlangen-Nürnberg)
Dekker, N.H. (TU Delft BN/Nynke Dekker Lab)
Lipfert, J. (Ludwig Maximilians University)

2017

The mechanical properties of DNA fundamentally constrain and enable the storage and transmission of genetic information and its use in DNA nanotechnology. Many properties of DNA depend on the ionic environment due to its highly charged backbone. In particular, both theoretical analyses and direct singlemolecule experiments have shown its bending stiffness to depend on salt concentration. In contrast, the salt-dependence of the twist stiffness of DNA is much less explored. Here, we employ optimized multiplexed magnetic torque tweezers to study the torsional stiffness of DNA under varying salt conditions as a function of stretching force. At low forces (<3 pN), the effective torsional stiffness is ∼10% smaller for high salt conditions (500 mM NaCl or 10 mM MgCl₂) compared to lower salt concentrations (20 mM NaCl and 100 mM NaCl). These differences, however, can be accounted for by taking into account the known salt dependence of the bending stiffness. In addition, the measured high-force (6.5 pN) torsional stiffness values of C = 103 ± 4 nm are identical, within experimental errors, for all tested salt concentration, suggesting that the intrinsic torsional stiffness of DNA does not depend on salt.

http://resolver.tudelft.nl/uuid:182d1a75-3a30-49f3-a0b1-de68f707e6e6

https://doi.org/10.1093/nar/gkx280

0305-1048

Nucleic acids research, 45 (10), 5920-5929

Institutional Repository

journal article

© 2017 Franziska Kriegel, Niklas Ermann, R.J.G. Forbes, D. Dulin, N.H. Dekker, J. Lipfert