Analysis of the neutral glycan fractions of glycosyl-phosphatidylinositols by thin-layer chromatography.

The radiolabeled neutral glycan fractions of both glycosyl-phosphatidylinositol (GPI) protein anchors and related glycolipids were analyzed by thin-layer chromatography on silica gel 60, using butanol:ethanol:water (4:3:3, v/v) or a combination of 1-propanol:acetone:water (9:6:5, v/v and 5:4:1, v/v) as solvents. Dextran acid hydrolysates were used as standards, and oligomers up to 11 glucose units could be resolved. A comparison of 18 GPI-glycan standards revealed that their migration was dependent mainly on the size of the oligosaccharide. Isomers were generally not resolved, with the exception of Man alpha 1-6Man alpha 1-4AHM and Man alpha 1-3Man alpha 1-4AHM. Structures containing galactofuranose or GalNAc were well resolved from structures containing only Galp and/or Manp. The utility of this method for the microsequencing of radiolabeled neutral glycans derived from two GPI glycolipids, using exoglycosidases and chemical treatments, is demonstrated. This method is a simple and useful complement to the existing chromatographic techniques.