Regensburg 2007 – wissenschaftliches Programm
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SYPE: Symposium Polyelectrolytes
SYPE 3: Polyelectrolytes II
SYPE 3.6: Vortrag
Freitag, 30. März 2007, 12:15–12:30, H1
Forces of interaction between DNA -grafted colloids : an optical tweezers measurement — •Friedrich Kremer1, Kati Kegler1, Christof Gutsche1, and Mathias Salomo2 — 1PAF, Exp. Physik 1, Universität Leipzig, Linnéstr. 5, 04103 Leipzig — 2Biophysik, Universität Leipzig, Linnéstr. 5, 04103 Leipzig
Optical tweezers are employed to measure the forces of interaction between single DNA-grafted colloids. Parameters to be varied are the length of the DNA(1000 base pairs (bp) to 6000 bp),the grafting density (1.84*1E-4 chains/nm2 to 1.97*1E-5 chains/nm2) and the ionic concentration (1E-5 M to 10 mM NaCl) of the surrounding medium. From the measured force-separation dependence an interaction-length at a given force (2pN) is deduced. It shows in the mushroom-regime a scaling with the grafting density which levels off for brushes. For the latter the transition from an osmotic to a salted brush can be traced in detail by varying the ionic concentration in accordance with meanfield theories. Further experiments are carried out to measure the influence of the valency of the added salt. Special emphasis is given to the interaction between one DNA-grafted and one blank colloid. The results are discussed with respect to the different brush regimes.
[1] K. Kegler, M. Salomo, and F. Kremer, in Press Phys. Rev. Lett.