title: Optical tweezers based force measurement system for quantitating binding interactions: system design and application for the study of bacterial adhesion.
abstract: An optical force measurement system for quantitating forces in the pN range between micrometer-sized objects has been developed. The system was based upon optical tweezers in combination with a sensitive position detection system and constructed around an inverted microscope. A trapped particle in the focus of the high numerical aperture microscope-objective behaves like an omnidirectional mechanical spring in response to an external force. The particle's displacement from the equilibrium position is therefore a direct measure of the exerted force. A weak probe laser beam, focused directly below the trapping focus, was used for position detection of the trapped particle (a polystyrene bead). The bead and the condenser focus the light to a distinct spot in the far field, monitored by a position sensitive detector. Various calibration procedures were implemented in order to provide absolute force measurements. The system has been used to measure the binding forces between Escherichia coli bacterial adhesins and galabiose-functionalized beads.
authors.affiliation: Department of Physics, Umeå University, SE-901 87 Umeå, Sweden. erik.fallman@physics.umu.se
authors.forename: Erik
authors.initials: E
authors.lastname: Fällman
authors.forename: Staffan
authors.initials: S
authors.lastname: Schedin
authors.forename: Jana
authors.initials: J
authors.lastname: Jass
authors.forename: Magnus
authors.initials: M
authors.lastname: Andersson
authors.forename: Bernt Eric
authors.initials: BE
authors.lastname: Uhlin
authors.forename: Ove
authors.initials: O
authors.lastname: Axner
mesh_terms: D001422:Bacterial Adhesion / Q000502:physiology*; D001703:Biophysics / Q000295:instrumentation*; D004187:Disaccharides / Q000502:physiology*; D004926:Escherichia coli / Q000502:physiology; D008863:Microspheres; D008954:Models, Biological
chemical_list: D004187:Disaccharides; C032103:4-O-alpha-D-galactopyranosyl-D-galactose