Berlin 2012 – wissenschaftliches Programm
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BP: Fachverband Biologische Physik
BP 23: Cytoskeletal Filaments
BP 23.7: Vortrag
Donnerstag, 29. März 2012, 16:45–17:00, H 1028
Structure and dynamics of in vitro cytokeratin networks — •Paul Pawelzyk1, Harald Herrmann2, and Norbert Willenbacher1 — 1Karlsruhe Institute of Technology (KIT), Institute for Mechanical Process Engineering and Mechanics, Gotthard-Franz-Str. 3, 76131 Karlsruhe, Germany — 2German Cancer Research Center, Division of Molecular Genetics, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany
Intermediate filament (IF) networks in epithelia cells consist of basic and acidic cytokeratin proteins, which join to heterodimers that assemble into filaments with a diameter of 10 nm. We have investigated networks of keratin 8 and 18 (K8/18) in vitro at different protein and MgCl2 concentrations using a combined approach including linear and non-linear rheology, scanning electron microscopy (SEM) and classical biochemical methods. The plateau modulus exhibits only a weak dependency on concentration (G0 ~ c0.5 ±0.1) which is attributed to filament bundling at higher keratin concentrations as confirmed by SEM. The onset of the non-linear stress response σcrit depends only weakly on these parameters. In contrast, the stress σmax at which the network ruptures and the corresponding differential modulus K′max strongly increase with increasing K8/18 or MgCl2 concentration. All data collapse onto a single master curve if K′/G0 is plotted versus σ/σcrit. Two scaling regimes with different exponents K′ ~ cαi are observed as already predicted by a composite network model including stiff rods connected by flexible linkers, but the experimentally obtained α-values (α1 = 1, α2 = 0.6) are clearly lower than those predicted theoretically.