This model supports the idea of lipids forming a more or less randomly organized fluid, flat, bi-dimensional matrix in which proteins perform their distinct functions. Results from a number of experimental and theoretical studies emphasize the significance of these fundamental physical properties and call for a refinement of the fluid mosaic model (and the accompanying raft hypothesis).Ĭurrent views on structural and dynamical aspects of biological membranes have been profoundly influenced and to some extent biased by the fluid mosaic model, proposed by Singer and Nicolson (1972).

Unfortunately, these relevant physical features of membranes are often ignored in the most popular models for biological membranes. Via the curvature stress, molecular shape mediates a coupling to membrane-protein function and provides a set of physical mechanisms for formation of lipid domains and laterally differentiated regions in the plane of the membrane. A key controller of the bilayer’s propensity to form curved structures is the average molecular shape of the different lipid molecules. Bilayers are also subject to built-in curvature-stress instabilities that may be released locally or globally in terms of morphological changes leading to the formation of non-lamellar and curved structures. The structure, dynamics, and stability of lipid bilayers are controlled by thermodynamic forces, leading to overall tensionless membranes with a distinct lateral organization and a conspicuous lateral pressure profile. 3Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark, Odense, Denmark.2Membrane Biophysics and Biophotonics group, Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark.1Center for Biomembrane Physics (MEMPHYS), University of Southern Denmark, Odense, Denmark.

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