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Nano Lett. 2015 Oct 14;15(10):7118-25. doi: 10.1021/acs.nanolett.5b03264. Epub 2015 Sep 28.

Relevance of the Drag Force during Controlled Translocation of a DNA-Protein Complex through a Glass Nanocapillary.

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Laboratory of Nanoscale Biology, Institute of Bioengineering, School of Engineering, EPFL , 1015 Lausanne, Switzerland.
Institute of Physics , Bijenicka cesta 46, HR-10000 Zagreb, Croatia.


Combination of glass nanocapillaries with optical tweezers allowed us to detect DNA-protein complexes in physiological conditions. In this system, a protein bound to DNA is characterized by a simultaneous change of the force and ionic current signals from the level observed for the bare DNA. Controlled displacement of the protein away from the nanocapillary opening revealed decay in the values of the force and ionic current. Negatively charged proteins EcoRI, RecA, and RNA polymerase formed complexes with DNA that experienced electrophoretic force lower than the bare DNA inside nanocapillaries. Force profiles obtained for DNA-RecA in our system were different than those in the system with nanopores in membranes and optical tweezers. We suggest that such behavior is due to the dominant impact of the drag force comparing to the electrostatic force acting on a DNA-protein complex inside nanocapillaries. We explained our results using a stochastic model taking into account the conical shape of glass nanocapillaries.


DNA translocation; DNA‚ąíprotein complex; force measurements; nanocapillary; nanopore; optical tweezers

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