title: Mechanical transition in a highly stretched and torsionally constrained DNA.
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.
authors.affiliation: Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziądzka 5, 87-100 Toruń, Poland.
authors.forename: Janusz
authors.initials: J
authors.lastname: Strzelecki
authors.affiliation: Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziądzka 5, 87-100 Toruń, Poland.
authors.forename: Lukasz
authors.initials: L
authors.lastname: Peplowski
authors.affiliation: Faculty of Biology and Environment Protection, Laboratory of Isotope and Instrumental Analysis, Lwowska 1, 87-100 Toruń, Poland.
authors.forename: Robert
authors.initials: R
authors.lastname: Lenartowski
authors.affiliation: Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziądzka 5, 87-100 Toruń, Poland.
authors.forename: Wieslaw
authors.initials: W
authors.lastname: Nowak
authors.affiliation: Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziądzka 5, 87-100 Toruń, Poland.
authors.forename: Aleksander
authors.initials: A
authors.lastname: Balter
mesh_terms: D003198:Computer Simulation; D004247:DNA / Q000737:chemistry* / Q000648:ultrastructure*; D055119:Elastic Modulus; D008422:Materials Testing; D008956:Models, Chemical; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D013314:Stress, Mechanical; D019415:Torque
chemical_list: D004247:DNA