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Viscoelastic properties of actin-coated membranes

E. Helfer1, S. Harlepp1, L. Bourdieu1,*, J. Robert1, F. C. MacKintosh2, and D. Chatenay1

  • 1Laboratoire de Dynamique des Fluides Complexes, U.M.R. 7506, 3 rue de l’Université, 67084 Strasbourg Cedex, France
  • 2Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1120

  • *Author to whom correspondence should be addressed.

Phys. Rev. E 63, 021904 – Published 19 January, 2001

DOI: https://doi.org/10.1103/PhysRevE.63.021904

Abstract

In living cells, cytoskeletal filaments interact with the plasma membrane to form structures that play a key role in cell shape and mechanical properties. To study the interaction between these basic components, we designed an in vitro self-assembled network of actin filaments attached to the outer surface of giant unilamellar vesicles. Optical tweezers and single-particle tracking experiments are used to study the rich dynamics of these actin-coated membranes (ACM). We show that microrheology studies can be carried out on such an individual microscopic object. The principle of the experiment consists in measuring the thermally excited position fluctuations of a probe bead attached biochemically to the membrane. We propose a model that relates the power spectrum of these thermal fluctuations to the viscoelastic properties of the membrane. The presence of the actin network modifies strongly the membrane dynamics with respect to a fluid, lipid bilayer one. It induces first a finite (ω=0) two-dimensional (2D) shear modulus G2D00.5 to 5 μN/m in the membrane plane. Moreover, the frequency dependence at high frequency of the shear modulus [G2D(f)f0.85±0.07] and of the bending modulus (κACM(f)f0.55±0.21) demonstrate the viscoelastic behavior of the composite membrane. These results are consistent with a common exponent of 0.75 for both moduli as expected from our model and from prior measurements on actin solutions.

See Also

Flexibility of Cell Membranes

Oliver Baker
Phys. Rev. Focus 7, 9 (2001)

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