Curvature elasticity of multilamellar lipid bilayers close to the chain-melting transition

We directly measured curvature elasticity of dipalmitoylphosphatidylcholine multilamellar bilayers close to the chain-melting transition using the met hod of electric-field-induced bending deformation of the cylindrical tubes. The result shows that the bending modulus, k(c), decreases remarkably at t emperatures close to the melting transition temperature. This reflects a so ftening of the bilayer resulted from the area fluctuations as predicted the oretically. However, the decrease of k(c) near the transition is far smalle r than that predicted. This is due to the experimental method and the narro w transition width of the multilamellar bilayers. Nevertheless, the result obtained gives direct evidence of the k(c) reduction predicted for multilam ellar membranes in the transition regime. Below about 41 degreesC, almost o f all cylindrical tubes cannot response to the electric field, indicating a very large bending rigidity. (C) 2001 Elsevier Science Ireland Ltd. All ri ghts reserved.