Subterahertz Response of Planar Phospholipid Membranes in Inelastic Light Scattering

Using a method of low frequency Raman scattering, hydrated planar samples of phospholipid bilayers are studied at room temperature. It has been demonstrated that a relaxation response, the spectral shape of which corresponds to a wide distribution of relaxation times in the picosecond range, is manifested in the subterahertz range. The spectral susceptibility of the relaxation response is described by a power function with an exponent of 0.25, is the same for gel and fluid phases of phospholipid bilayers, and does not depend on the degree of saturation of hydrocarbon tails of different phospholipids. The subterahertz relaxation response can be considered as an elementary relaxation event, which precedes slower relaxation processes such as lateral diffusion and changes in the thickness or curvature of a phospholipid bilayer.