The variable surface glycolipids of mycobacteria: Structures, synthesis of epitopes, and biological properties

This chapter describes the structure and synthesis of epitopes and elaborates the biological properties of the variable surface glycolipids of mycobacteria. It also presents the detailed procedures for the isolation and purification of the species-specific glycolipids of mycobacteria. Large quantities of acylglycerols and phosphoglycerides are present, and it is often impossible to isolate specific glycopeptidolipids (GPLs) in preparative amounts directly from these extracts. The relative alkaline stability of the GPLs may be exploited under conditions that result in the saponification of acyl esters when the crude lipid extract, in 2:1 chloroform–methanol, is treated with an equal volume of 0.2 M sodium hydroxide. The direct compositional analysis of glycolipids from mycobacteria remains the simplest and most necessary first step, in the light of the widespread occurrence of endogenously methylated glycose residues. Hydrolysis of the glycolipid, followed by the identification by gas-chromatographic mass spectroscopy (GC-MS) using capillary columns of the derived alditol acetates, is most appropriate because this method allows for the location of the methyl ether substituents when these are present. The anomeric and ring configurations of glycosyl residues are also elaborated in the chapter. © 1995 Academic Press, Inc.