Bilayer bending rigidity of some synthetic lecithins

The curvature elastic modulus of fluid membranes of DMPC, DPPC, and DSPC in water was measured. From the equilibrium distribution of the thermal bending fluctuations of tubular vesicles we obtained values of 2.4, 2.0, and 1.8 × 10-12 erg, respectively, with errors of about 20 %. We also observed some deformations of the fluctuating tubes such as sharp knee-like bends and pronounced short-waved wriggles which apparent elastic energies seem too high for thermal excitation.