Regensburg 2004 – wissenschaftliches Programm

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SYLS: Life Sciences on the Nanometer Scale - Physics Meets Biology

SYLS 3: Symposium "Life Sciences on the Nanometer Scale - Physics Meets Biology"

SYLS 3.37: Poster

Mittwoch, 10. März 2004, 16:00–18:30, B

Attraction of similarly-charged macroions — •Ali Naji and Roland Netz — Sektion Physik, Ludwig-Maximilians-Universitaet Muenchen, Theresienstr. 37, 80333 Muenchen

We investigate effective electrostatic interaction between similarly-charged rod-like and spherical macroions in the regime of strong electrostatic correlations using the asymptotic strong-coupling theory. We examine the regime of charge parameters, in which dominant electrostatic attraction is predicted between charged rods and charged spheres. For highly-charged macroions, such an attraction gives rise to the formation of closely-packed macroion-macroion bound states with finite surface-to-surface separation. In this regime, the predictions of the strong-coupling theory for the equilibrium separation of macroions is found to be in quantitative agreement with recent numerical simulations both on charged rods and charged spheres. We study finite size effects (due to confinement) on the effective interaction: rod-like macroions are found to attract each other both in confined and unconfined geometries; specifically, unconfined rods show attraction when the single-rod Manning parameter becomes larger than 2/3. By contrast, spherical macroions exhibit attraction only in confinement, and the onset of attraction (the threshold charge strength) in this case depends on the size of the confining box, and weakly (logarithmically) increases with the box size. By decreasing the charge parameter, attracting macroions undergo an unbinding transition from a closely-packed bound state to a repulsion-dominated state. This transition occurs continuously for charged rods displaying a scaling relation, while charged spheres exhibit a discontinuous transition.