title: Thermophoretic forces on DNA measured with a single-molecule spring balance.
abstract: We stretch a single DNA molecule with thermophoretic forces and measure these forces with a spring balance: the DNA molecule itself. It is an entropic spring which we calibrate, using as a benchmark its Brownian motion in the nanochannel that contains and prestretches it. This direct measurement of the thermophoretic force in a static configuration finds forces up to 130 fN. This is eleven times stronger than the force experienced by the same molecule in the same thermal gradient in bulk, where the molecule shields itself. Our stronger forces stretch the middle of the molecule up to 80% of its contour length. We find the Soret coefficient per unit length of DNA at various ionic strengths. It agrees, with novel precision, with results obtained in bulk for DNA too short to shield itself and with the thermodynamic model of thermophoresis.
authors.affiliation: Department of Micro- and Nanotechnology, Technical University of Denmark, DK-2800 Lyngby, Denmark.
authors.forename: Jonas N
authors.initials: JN
authors.lastname: Pedersen
authors.affiliation: Department of Micro- and Nanotechnology, Technical University of Denmark, DK-2800 Lyngby, Denmark.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Lüscher
authors.affiliation: Department of Micro- and Nanotechnology, Technical University of Denmark, DK-2800 Lyngby, Denmark.
authors.forename: Rodolphe
authors.initials: R
authors.lastname: Marie
authors.affiliation: Department of Micro- and Nanotechnology, Technical University of Denmark, DK-2800 Lyngby, Denmark.
authors.forename: Lasse H
authors.initials: LH
authors.lastname: Thamdrup
authors.affiliation: Department of Micro- and Nanotechnology, Technical University of Denmark, DK-2800 Lyngby, Denmark.
authors.forename: Anders
authors.initials: A
authors.lastname: Kristensen
authors.affiliation: Department of Micro- and Nanotechnology, Technical University of Denmark, DK-2800 Lyngby, Denmark.
authors.forename: Henrik
authors.initials: H
authors.lastname: Flyvbjerg
mesh_terms: D017122:Bacteriophage T4 / Q000737:chemistry / Q000235:genetics; D004247:DNA / Q000737:chemistry*; D004279:DNA, Viral / Q000737:chemistry; D006358:Hot Temperature; D046210:Microfluidic Analytical Techniques / Q000379:methods; D008956:Models, Chemical; D053758:Nanoparticles / Q000737:chemistry; D009994:Osmolar Concentration; D013816:Thermodynamics
chemical_list: D004279:DNA, Viral; D004247:DNA