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Soft Matter and Biological Physics
Eur. Phys. J. E 10, 319-330 (2003)
DOI: 10.1140/epje/i2002-10118-9

On the organization of self-assembled actin networks in giant vesicles

L. Limozin, M. Bärmann and E. Sackmann

Lehrstuhl für Biophysik E22, Physik Department, Technische Universität München, James Franck Str., 85748 Garching, Germany


(Received 17 January 2002 and Received in final form 29 November 2002 / Published online: 24 April 2003)

We studied the formation of actin scaffolds in giant vesicles of dimyristoylphosphatidylcholine (DMPC). Polymerization of actin was induced at low ionic strength through ionophore-mediated influx of Mg 2+ (2 mM). The spatial organization of the filamentous actin was visualized by confocal and epifluorescence microscopy as a function of the filaments length and membrane composition, by including various amounts of cholesterol or lipids with neutral and positively charged polyethyleneglycol headgroups (PEG lipopolymers). In vesicles of pure DMPC, the newly polymerized actin adsorbs to the membrane and forms a thin shell. In the presence of 2.5 mol% lipopolymers or of cholesterol at a molar fraction x=0.37, formation of a thin adsorbed film is impeded. A fuzzy cortex is predominantly formed in vesicles of diameter d smaller than the filament persistence length ( $d\leq 15~\mu$m) while for larger vesicles a homogeneous network formation is favoured in the bulk of the vesicle. The fuzzy-cortex formation is interpreted as a consequence of the reduction of the bending energy if the actin filaments accumulate close to the vesicle wall.

87.16.Dg - Membranes, bilayers, and vesicles.
87.16.Ka - Filaments, microtubules, their networks, and supramolecular assemblies.

© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2003