DOI: 10.1140/epje/i2002-10118-9
On the organization of self-assembled actin networks in giant vesicles
L. Limozin, M. Bärmann and E. SackmannLehrstuhl für Biophysik E22, Physik Department, Technische Universität München, James Franck Str., 85748 Garching, Germany Laurent_Limozin@ph.tum.de
(Received 17 January 2002 and Received in final form 29 November 2002 / Published online: 24 April 2003)
Abstract
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 (
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
