title: DNA interactions in crowded nanopores.
abstract: The motion of DNA in crowded environments is a common theme in physics and biology. Examples include gel electrophoresis and the self-interaction of DNA within cells and viral capsids. Here we study the interaction of multiple DNA molecules within a nanopore by tethering the DNA to a bead held in a laser optical trap to produce a "molecular tug-of-war". We measure this tether force as a function of the number of DNA molecules in the pore and show that the force per molecule decreases with the number of molecules. A simple scaling argument based on a mean field theory of the hydrodynamic interactions between multiple DNA strands explains our observations. At high salt concentrations, when the Debye length approaches the size of the counterions, the force per molecule becomes essentially independent of the number of molecules. We attribute this to a sharp decrease in electroosmotic flow which makes the hydrodynamic interactions ineffective.
authors.affiliation: Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom.
authors.forename: Nadanai
authors.initials: N
authors.lastname: Laohakunakorn
authors.forename: Sandip
authors.initials: S
authors.lastname: Ghosal
authors.forename: Oliver
authors.initials: O
authors.lastname: Otto
authors.forename: Karolis
authors.initials: K
authors.lastname: Misiunas
authors.forename: Ulrich F
authors.initials: UF
authors.lastname: Keyser
mesh_terms: D004247:DNA / Q000737:chemistry*; D058608:Nanopores; D052898:Optical Tweezers
chemical_list: D004247:DNA