The ripple phase in model membrane systems

Abstract

The highly hydrated phospholipid bilayers often exhibit the so called P _β or ripple phase, which is not yet clearly understood. We have associated the ripple phase to a thermally fluctuating ripple deformation of the bilayer that may be Fourier decomposed into a set of spatial modes. These modes, called ripplons or capillary waves, are driven by the viscoelastic properties of the membranes at the interface with the solvent. The model we proposed is applied on experimental results of radiowave dielectric measurements in DPPC- and DMPC-water mixtures, where the polarization contribution in the ripple phase is supposedly originated by the ripple modulation, and in DPPE-water mixture, where the pretransition disappears. The prediction of the model shows a good qualitative agreement with the experimental results in a wide frequency range.