title: High Spatiotemporal-Resolution Magnetic Tweezers: Calibration and Applications for DNA Dynamics.
abstract: The observation of biological processes at the molecular scale in real time requires high spatial and temporal resolution. Magnetic tweezers are straightforward to implement, free of radiation or photodamage, and provide ample multiplexing capability, but their spatiotemporal resolution has lagged behind that of other single-molecule manipulation techniques, notably optical tweezers and AFM. Here, we present, to our knowledge, a new high-resolution magnetic tweezers apparatus. We systematically characterize the achievable spatiotemporal resolution for both incoherent and coherent light sources, different types and sizes of beads, and different types and lengths of tethered molecules. Using a bright coherent laser source for illumination and tracking at 6 kHz, we resolve 3 Å steps with a 1 s period for surface-melted beads and 5 Å steps with a 0.5 s period for double-stranded-dsDNA-tethered beads, in good agreement with a model of stochastic bead motion in the magnetic tweezers. We demonstrate how this instrument can be used to monitor the opening and closing of a DNA hairpin on millisecond timescales in real time, together with attendant changes in the hairpin dynamics upon the addition of deoxythymidine triphosphate. Our approach opens up the possibility of observing biological events at submillisecond timescales with subnanometer resolution using camera-based detection.
authors.affiliation: Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands. Electronic address: daviddulin82@gmail.com.
authors.forename: David
authors.initials: D
authors.lastname: Dulin
authors.affiliation: Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands.
authors.forename: Tao Ju
authors.initials: TJ
authors.lastname: Cui
authors.affiliation: Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands.
authors.forename: Jelmer
authors.initials: J
authors.lastname: Cnossen
authors.affiliation: Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands.
authors.forename: Margreet W
authors.initials: MW
authors.lastname: Docter
authors.affiliation: Department of Physics, Nanosystems Initiative Munich and Center for Nanoscience, Ludwig-Maximilians-University Munich, Munich, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Lipfert
authors.affiliation: Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands. Electronic address: n.h.dekker@tudelft.nl.
authors.forename: Nynke H
authors.initials: NH
authors.lastname: Dekker
mesh_terms: D004247:DNA / Q000737:chemistry*; D060526:Magnetic Fields; D056004:Molecular Dynamics Simulation; D009690:Nucleic Acid Conformation; D061848:Optical Imaging / Q000295:instrumentation / Q000379:methods* / Q000592:standards; D052898:Optical Tweezers
chemical_list: D004247:DNA