biostudies-literatureCeledon AHoward Hughes Medical InstituteNIGMS NIH HHS1720-5https://www.ebi.ac.uk/biostudies/studies/S-EPMC4823137biostudies-literatureUnknown9(4)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.Nano lettersMagnetic tweezers measurement of single molecule torque.PMC4823137R01 GM084192-02R01 GM084192-01R01 GM075305-05R01 GM075305-04R01 GM075305-03R01 GM075305-02R01 GM075305R01 GM075305-01R01 GM084192Wildt BCeledon ANodelman IMSearson PBowman GDSun SXWirtz DDewan RfalseMagnetic tweezers measurement of single molecule torque.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.2009-01-01T00:00:00Z2009 Apr2020-10-29T13:23:34Z2019-03-27T03:11:22ZS-EPMC48231371930185910.1021/nl900631w