Brownian Motion of Lipid Molecules

Lateral and transmembrane diffusions in lipid molecules are discussed in terms of translational and rotational motions of a long cylinder. A procedure is suggested to deduce the dimensions (length and radius) of lipid molecules using experimental diffusion or viscosity data. It is shown that the hydrodynamic equation for transmembrane diffusion predicts a slower motion than for lateral diffusion, in qualitative agreement with experimental results. Further, the consequences of coupling transmembrane motion with rotational motion are discussed.