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Séminaire Laura Rodriguez-Arriaga

Mechanics of Model Biomembranes

Laura R. Arriaga

Laboratoire de Physique des Solides
CNRS et Université Paris-Sud, Orsay

My Ph.D thesis addressed the question of the first principles underlying the mechanical behavior of biomembranes, i.e., the microscopic origin of the characteristic elasticity and fluidity of lipid bilayers and how it manifests in terms of structure and dynamics. With the necessary reference to the classical Fluid Mosaic Model [1] where mosaicity must be understood as heterogeneity, a direct consequence of the compositional richness of the membrane, our starting hypothesis assigned a structural and mechano-functional role to the lipid composition and distribution of the membrane. In particular, the so-called lipid rafts [2] were identified as the structural key elements and cholesterol, the main component in eukaryotic membranes, as the fundamental ingredient in the regulation of membrane fluidity and rigidity.

Two different experimental approaches were used to study the viscoelastic behavior of model biomembranes. The compressibility of each membrane leaflet was studied by oscillatory surface rheology experiments on Langmuir monolayers. In order to mimic the characteristic mosaicity of real membranes, our models were made of lipids in which phase coexistence could be induced by lateral pressure. The curvature mechanics of the complete bilayer was studied from the analysis of the shape fluctuations of unilamellar vesicles by radiation scattering techniques. Both methodologies were complementary in clarifying the coupling between the compression and the bending movements in biomembranes [3].

  1. S. J. Singer and G. L. Nicolson, Science 175, 720 (1972).
  2. K. Simons and E. Ikonen, Nature 387, 569 (1997).
  3. W. Helfrich, Z. Naturforsch. C 28, 693 (1973).