Densitometric quantification of brain gangliosides separated by two-dimensional thin layer chromatography

A procedure for accurate densitometric quantification of gangliosides separated by two-dimensional thin layer chromatography is reported. The procedure was set up employing 9 different pure gangliosides and was applied to the analysis of calf and pig brain gangliosides. Silica gel high performance thin layer plates, 10 x 10 cm. were two-dimensionally developed at 18-20 C with the following solvents: chloroform methanol 0.2% aqueous CaCl(2), 50/40/10 by volume, for the first run; n-propanol 17 M NH(4)OH/water, 6/2/1 by volume for the second run. Ganglioside spots were visualized by spraying with an Ehrlich reagent, which is specific for sialic acid, and heating at 120 C for 15 min. The spots were quantified by sequential scanning densitometry, linear responses being obtained for ganglioside amounts on the plate ranging from 0.1 to 6 nmol as bound sialic acid. The reproducibility of densitometric responses resulted to be acceptable since the standard deviation values were lower than +/- 15% of the mean values also for those ganglioside species contained in minor proportions. The ganglioside mixtures of calf and pig brain were resolved in about 20 spots. Of these 9 corresponded to gangliosides GM3, GM2, GM1, Fuc-GM1, GD1a, GD1b, Fuc-GD1b, GT1b and GQ1b, which were identified with certainty and quantified. The identification of GM3 (carrying N-glycolylneuraminic acid), GD3, GD1a (carrying N-acetyl- and N-glycolyl-neuraminic acid) and GT1a was only tentative. All the other spots corresponded to unidentified gangliosides, some of them possibly new species.