Synthesis and self-assembly behaviors of α-galactosyl ceramide (1,2)-polysaccharide analogue

Abstract

α-Galactosyl ceramide (GalCer) as a glycolipid has been long used as a standard reference for positive control in natural killer T cell studies. The (1,2)-disaccharide analogue of GalCer attracts a special attention in the study of lysosomal glycolipid processing. This paper describes the synthesis and self-assembly behaviors of GalCer 1,2-polysaccharide analogue (PolyGalCer), having considered the 1,2-disaccharide analogue as a structural motif. The synthesis of PolyGalCer is performed via one-pot glycosidation technique of 1,2-linked oligogalactan exploiting chain polymerization of galactose-based cyclic sulfite as a monomer initiated with ceramide-based alcoholic aglycon. Through the concentration dependence of PolyGalCer solutions in water or in MeOH on the turbidity, it is found that PolyGalCer forms associates in both media. From the intersection points, the critical aggregation concentration (CAC) values of PolyGalCer in water and MeOH were estimated. To know the self-assembly and the thermal transition behaviors, we performed dynamic light scattering (DLS) analysis of the associates comprising PolyGalCer in water. The transmission electron microscopy observations of the aqueous sample solution indicate that the solution of PolyGalCer includes large spherical associates. The results clarify that the 1,2-galactan moiety of PolyGalCer skeleton contributes on the kinetic inhibition of large associate formation and the metamorphosis of associates.

Keywords: Graft polymerization; Self-assembly; α-Galactosyl ceramide.