Eur. Phys. J. E (2010) 31: 105-113
https://doi.org/10.1140/epje/i2010-10551-1

Regular Article

Dissipative curvature fluctuations in bilayer vesicles: Coexistence of pure-bending and hybrid curvature-compression modes

¹ Mechanics of Biological Membranes and Biorheology, Universidad Complutense, Ciudad Universitaria s/n, E28040, Madrid, Spain
² Institut Laue Langevin, 6 rue Jules Horowitz, BP 156, F38042, Grenoble Cedex 9, France
³ Physikalische Chemie I, Univeristät Bayreuth, Universitätsstraße 30, D95447, Bayreuth, Germany

^* e-mail: monroy@quim.ucm.es

Received: 15 October 2009
Revised: 24 November 2009
Accepted: 3 December 2009
Published online: 20 January 2010

Abstract

We have studied the relaxation dynamics of shape fluctuations in unilamellar lipid vesicles by neutron spin echo (NSE). The presence of a hybrid curvature-compression mode coexisting with the usual bending one has been revealed in the experimental relaxation functions at high q . Differently to the conventional relaxation ∼ q ³ typical for bending modes, the hybrid mode was found to relax as ∼ q ² , which is compatible with a dissipation mechanism arising from intermonolayer friction. Complementary data obtained from flickering spectroscopy (FS) in giant unilamellar vesicles confirm the existence of both modes coexisting together. By combining NSE and FS data we have depicted the experimental bimodal dispersion diagram, which is found compatible with theoretical predictions for reliable values of the material parameters. From the present data two conventional dynamical methods (NSE and FS) have been shown to be suitable for measuring intermonolayer friction coefficients in bilayer vesicles.