It has been investigated that the super-molecular structures in liquid crystalline states are made up of DEPE (1,2-dielaidoyl-sn-glycero-3-phosphatidyl-ethanolamine), sphingomyeline, monosialioganglioside-Gm1 and cholesterol by small angle X-ray diffraction. The effect of sphingomyeline on DEPE film was determined. A structure transition from Im3m(Q²²⁹) to Pn3m(Q²²⁴) occurred with increasing sphingomyeline concentration in the super-molecular structures. The effect of monosialioganglioside-Gm1 content on the super-molecular structures was also determined. At a critical concentration of monosialioganglioside-Gm1, the structure transition from Im3m(Q²²⁹) to Pn3m(Q²²⁴) occurred. The effect of the addition of cholesterol on DEPE-Shp-Gm1 super-molecular structure has also been investigated. There exists an interaction between the polar head (—OH) of cholesterol and that of DEPE, sphingomyeline, monosialioganglioside-Gm1 by oxygen-halogen bond, to form cubic phase of liquid crystalline states. A Pn3m(Q²²⁴) structure was further formed by hydrophilic/hydrophobic interaction.

Key words: biomembrane, cubic phase in liquid crystalline states, small angle X-ray diffraction