Glycan conformational change in mesomorphic structures of ternary systems: liposaccharide/phospholipid/water

An amphipatic liposaccharide, beta 16, has been synthesized by condensation of the glycoamino acid beta of ovomucoid with the palmitic acid to serve as a model on which the properties of the saccharide chains can be studied. This paper reports the ternary system beta 16/dipalmitoylphosphatidylcholine (DPPC)/water. Using X-ray diffraction and freeze-fracture electron microscopy, it was shown that the ternary system exhibits mesomorphic structures in the temperature range over which the aliphatic chains of the DPPC are in a liquid-like conformation. A phase diagram of the system was drawn at 75 degrees C in terms of the water concentration and of the beta 16 content. As the molar fraction in beta 16 increases from about 0.08 to 1, the ternary system displays successively two lamellar structures analogous to that exhibited by the system DPPC/H2O, then a hexagonal structure similar to that exhibited by the system beta 16/H2O. The two types of lamellar structure were shown to differ by the T or Y conformation adopted by their saccharide chains.