Berlin 2012 – scientific programme

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BP: Fachverband Biologische Physik

BP 13: DNA/RNA and Related Enzymes

BP 13.5: Talk

Wednesday, March 28, 2012, 10:45–11:00, H 1058

Electrophortic mobility of DNA-grafted single colloids as studied by optical tweezers — •Ilya Semenov, Christof Gutsche, Mahdy M. Elmahdy, Olaf Ueberschär, and Friedrich Kremer — Institute for Experimental Physics I, University of Leipzig, Linnéstrasse 5, 04103 Leipzig, Germany

The electrophoretic mobility of single particles grafted with double stranded (ds) DNA is studied by use of optical tweezers (OT) accomplished with fast position detection (Single Colloid Electrophoresis [1, 2]). Parameters to be varied are the concentration (0.01 mMol/l - 1 Mol/l) and valency (KCl, CaCl₂, LaCl₃) of the ions in the surrounding aqueous medium, but as well the contour length (250, 1000 and 4000 base pairs) of the grafted chains. For the DNA-grafted colloids a pronounced decrease of the electrophoretic mobility is observed in comparison to blank particles under identical conditions. The findings are discussed in terms of the Standard Electrokinetic Model [3]. The electrophoretic mobility of a ds-DNA-grafted single colloid at high ionic strength can be understood quantitatively within the limits of the linearized Poisson-Boltzmann equation.

[1] I. Semenov et al., Journal of Physics: Condensed Matter 22, 494109 (2010).

[2] I. Semenov et al., Journal of Colloid and Interface Science 337, 260 (2009).

[3] R. W. O’Brien, and L. R. White, JCS, Farad. Trans. 2 74, 1607 (1978).