On the Biomembranes as Composite Lamellae of Smectic A Liquid Crystal and Macromolecular Network: Elastic Properties, Local and Collective Dynamics

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Abstract
Some exceptional elastic and dynamic properties of biomembranes (in particular cell plasma membranes) which are based on their composite structure consisting of a smectic A liquid/protein bilayer to which a quasi-twodimensional macromolecular network is loosely coupled are discussed. Compared to technical materials, their elastic properties are remarkably soft with respect to bending and shearing whereas the lateral area compressibility modulus is comparable to that of organic materials (e.g., polymers). The latter is essential for the membrane function as electrically insulating barrier and may play an important role for the molecular organization of the lipid/protein bilayer as well as the activity of enzymes. In the second part local motional processes as observed by incoherent quasielastic neutron scattering experiments are reported and basic principles of lateral mobility and undulatory excitations are discussed.