Eur. Phys. J. E 2, 125-136
Binding of actin filaments to charged lipid monolayers: Film balance experiments combined with neutron reflectivity
B. Demé1 - D. Hess1 - M. Tristl1 - Lay-Theng Lee2 - E. Sackmann1
1 Technische Universität München, Physik Department,
Lehrstuhl für Biophysik E22, James-Franck-Str., D-85747
Garching, Germany
2 Laboratoire Léon Brillouin, CEA-CNRS, Centre
d'Études de Saclay, F-91191 Gif sur Yvette, France
deme@ill.fr
Received 11 August 1999
Abstract
The binding of polymerised actin--a prototype of
semi-flexible macromolecule--to lipid monolayers is studied by
neutron reflectivity to deduce the average thickness, the
interfacial roughness and the polymer volume fraction of the
adsorbed film. Electrostatic interaction between actin filaments
(F-actin) and the lipid monolayer is mediated through a cationic
lipid (1,2-dimyristoyl-3-trimethylammonium-propane, DMTAP). The
adsorbed F-actin forms a monolayer with an average thickness of
69 to 84 Å, depending on the ionic strength of the buffer
and surface charge density of the monolayer. The volume fraction
of F-actin in the adsorbed layer can be as high as 0.29. The
thickness and high volume fraction of the actin layer suggest
that actin filaments lie flat on the surface and form nematic
ordering. The binding-unbinding equilibrium of F-actin is
controlled by the ionic strength and exhibits a strong
hysteresis. In contrast to the results obtained for filamentous
actin, monomeric actin (G-actin) shows no detectable binding to
the positively charged lipid layers.
PACS
61.12.Ha Neutron reflectometry - 68.55.Jk
Structure and morphology; thickness
Copyright EDP Sciences, Società Italiana di Fisica, Springer-Verlag
