The aqueous surroundings alter the bending rigidity of lipid membranes

Abstract

The bending elasticity is the mechanical property that characterizes the deformability of lipid bilayers. In the present study the bending elasticity of phosphatidylcholine lipid membranes is reported in aqueous media with various chemical composition and pH. The bending modulus is obtained from analysis of the thermal shape fluctuations, performed on nearly spherical giant lipid vesicles. Lower bending rigidity of phosphatidylcholine bilayers is measured in aqueous media, containing potassium or sodium chlorides, compared to its value in water without salts. The results reported here for the membrane bending elasticity at three acidic values of pH are compared with the literature data from micromanipulation measurements of giant unilamellar vesicles from the same lipid. In accordance with previous results, further evidences are provided for the softening of lipid bilayers in the presence of sucrose in the aqueous surroundings.