Liquid crystal theory of biomembranes

<正> 1 Introduction Helfrich noticed that lipid bilayer is the basic structural unit of cell membranes.He also recognized that if the carbon chains of the lipid molecules are treated as the director of uniaxial liquid crystal, the bilayer membrane is just like a homeotropic nematic liquid crystal cell of thickness (in the order of 8 nm) twice the length of the lipid molecule. Based on the Frank free energy density expression for uniaxial liquid crystals with unit normal to the membranes as the director of liquid crystal, Helfrich proposed the elastic energy of curvature per unit area of the cell membrane as