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BP: Fachverband Biologische Physik
BP 7: Poster I
BP 7.58: Poster
Monday, March 23, 2009, 17:45–20:00, P3
Optical tweezers measurements of threading DNA and DNA-ligand-complexes through solid-state nanopores — •Andy Sischka1, Christoph Kleimann1, Wiebke Hachmann2, Marcus M. Schäfer3, Ina Seuffert4, Katja Tönsing1, and Dario Anselmetti1 — 1Experimental Biophysics and Applied Nanosciences, Bielefeld University, Germany — 2Molecular and Surface Physics, Bielefeld University, Germany — 3Center for Nanotechnology (CeNTech), Münster, Germany — 4Fachbereich Physik, Fach M621, University of Konstanz, Germany
We developed a versatile and high precision 3D optical tweezers setup, capable for force measurements completely based on detection of backscattered light with minimal optical interference to measure forces in the sub-pN regime and to manipulate single molecules. With this novel setup, single dsDNA-molecules were threaded into a solid-state nanopore by applying electrical voltage across the membrane, as the electrostatic force and the ionic current through the pore were measured. Here, individual force steps could be observed for each DNA-molecule entering the nanopore. Active pulling of a single Lambda-DNA-molecule out of the nanopore by linearly increasing the bead-membrane distance induced a force signal with only very weak force oscillations of about 2 pN, until the DNA was completely pulled out of the nanopore. Binding of dedicated protein ligands (peroxiredoxin, and E.coli RNA-polymerase) to dsDNA caused a significant change in the apparent electrostatic forces that are required for threading and unthreading the DNA-ligand-complex through the nanopore.