Abstract
Effects of the stereochemistry of oligosaccharide headgroups on the physical properties of aqueous synthetic glycolipid, 1, 3-di-O-dodecyl-2-O-(β-glycosyl) glycerols bearing cellooligosaccharides (β-1, 4-O-glycosidic bonds) and maltooligosaccharides (α-1, 4-O-glycosidic bonds) as hydrophilic groups have been studied. The increase in the number of glucose residues, N, in the two different headgoups exhibited opposite effects on the physical properties of the aqueous glycolipids. For the maltooligosaccharide-containing lipids, MalN(C12)2, increasing N in the headgroups decreases the hydrated-solid/liquid-crystalline phase trasition temperature Tm, and increases the “hydrophilicity” of the lipids. However, the Tm of the cellooligosaccharide-containing lipids CelN(C12)2 increases with increasing N of the cellooligosaccharide headgroups. It is noteworthy that Tm jumps from 59°C (for N=4) to above 160°C (for N=5), so that the Cel5(C12)2 cannot form a liquid crystalline phase, and is totally insoluble in water. The results can be explained in terms of different conformations of the headgroups, i.e., a “helical” conformation of the maltooligosaccharides and an “extended” conformation of the cellooligosaccharides.
