Effect of cholesterol on the fluidity of supported lipid bilayers

The lateral mobility serves as a key function of the cell membrane and can be regulated by the cholesterol. Here supported lipid bilayers were used to quantitatively analyse the influence of cholesterol on the fluidity of lipid bilayer in the environments with and without an electric field. We observed that with the increase of cholesterol proportion (0-30 mol%), the diffusion coefficient of DOPC lipid bilayer gradually decreased from 1.30 ± 0.15 μm² s^-1 to 0.28 ± 0.13 μm² s^-1, where as that of DPPC lipid bilayer increased slightly from ∼0 to 0.45 ± 0.18 μm² s^-1. We then showed that cholesterol also regulated the movement of charged lipids in the bilayer in the electric field. The migration rate of charged lipids in the DOPC bilayers slowed down as the cholesterol increased. The clarification of the dose-effect relationship of cholesterol for the bidirectional regulating effect on the mobility of lipid bilayer will extend applications of supported lipid bilayers as the model of cell membrane.