Experimental evidence of the electrostatic contribution to membrane bending rigidity
نویسندگان
چکیده
– We have investigated the thermal fluctuations of giant unilamellar dimyristoylphosphatidlycholine vesicles in the presence of both non-ionic and ionic surfactants (peptides) with identical apolar chains. Using vesicle fluctuation analysis, the effects of ionic and non-ionic surfactants upon membrane bending rigidity in the case of no added salt have been determined and the electrostatic contribution thereby isolated. We interpret these experimental findings in terms of a mean-field free-energy model for the adsorption of charged surfactants to a lipid bilayer and couple these results to describe the electrostatic contribution to membrane bending rigidity. This experimental study demonstrates how electrostatics affect the elastic properties of unilamellar bilayers. Membranes are complex and dynamic entities which serve not only to compartmentalize life but also as the site of many important targeting and signalling events. The membrane is thus an active port of biological function. For example, the localization of proteins to membrane interfaces is sensitive to membrane composition, pH, as well as charge effects. How membrane shape and mechanical properties may be altered by these factors is still not clear. Embedded in Helfrich’s curvature free energy is a description of the mechanical and conformational properties of membranes [1]:
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