title: Magnetic tweezers measurement of single molecule torque.
abstract: Torsional stress in linear biopolymers such as DNA and chromatin has important consequences for nanoscale biological processes. We have developed a new method to directly measure torque on single molecules. Using a cylindrical magnet, we manipulate a novel probe consisting of a nanorod with a 0.1 microm ferromagnetic segment coupled to a magnetic bead. We achieve controlled introduction of turns into the molecule and precise measurement of torque and molecule extension as a function of the number of turns at low pulling force. We show torque measurement of single DNA molecules and demonstrate for the first time measurements of single chromatin fibers.
authors.affiliation: Department of Mechanical Engineering, Howard Hughes Medical Institute Graduate Training Program and Institute for NanoBioTechnology, Johns Hopkins University, Baltimore Maryland 21218, USA.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Celedon
authors.forename: Ilana M
authors.initials: IM
authors.lastname: Nodelman
authors.forename: Bridget
authors.initials: B
authors.lastname: Wildt
authors.forename: Rohit
authors.initials: R
authors.lastname: Dewan
authors.forename: Peter
authors.initials: P
authors.lastname: Searson
authors.forename: Denis
authors.initials: D
authors.lastname: Wirtz
authors.forename: Gregory D
authors.initials: GD
authors.lastname: Bowman
authors.forename: Sean X
authors.initials: SX
authors.lastname: Sun
mesh_terms: D001704:Biopolymers; D002843:Chromatin / Q000737:chemistry; D004247:DNA / Q000737:chemistry; D008280:Magnetics
chemical_list: D001704:Biopolymers; D002843:Chromatin; D004247:DNA