J. Phys. France
Volume 51, Number 10, mai 1990
Page(s) 945 - 961
J. Phys. France 51, 945-961 (1990)
DOI: 10.1051/jphys:019900051010094500

Bending elastic moduli of lipid bilayers : modulation by solutes

H.P. Duwe, J. Kaes et E. Sackmann

Physik-Department, Biophysics Group, Technische Universität München, D-8046 Garching, F.R.G.

We present high precision measurements of the bending elastic moduli for bilayers of a variety of different lipids and of modifications of the flexural rigidity by solutes. The measurements are based on the Fourier analysis of thermally excited membrane undulations (vesicle shape fluctuations) using a recently developed dynamic image processing method. Measurements of the bending modulus as a function of the undulation wave vector provide information on the limitation of the excitations by the constraint of finite membrane area (surface tension effects) and by transient lateral tensions arising in each monolayer by restricted diffusion at high wavevectors. Measurements of the autocorrelation function of the undulation amplitudes provide a further test of the theoretical models. Studies of the effect of solutes show that cholesterol increases the bending modulus of dimyristoylphosphatidylcholine from Kc = 1.1 × 10^-12 ergs to 4.2 x 10^-12 ergs (at 30 mole %). Incorporation of about 2 mole % of a short bipolar lipid reduces Kc to the order of kT. A scaling law between the projected radius of gyration, Rg, of these hyperelastic vesicles and the surface area, A (or number of lipid molecules N) of R2g ∝ A 0.94 ± 0.02 was established.

8715L - Mechanical properties.

Key words
bending -- elastic moduli -- Fourier analysis -- lipid bilayers -- organic compounds -- surface tension