This paper reports the use of a quadrupole time-of-flight (Q-TOF) mass spectrometer fitted with a matrix-assisted
laser desorption/ionization (MALDI) ion source for the analysis of neutral and
acidic glycosphingolipids. All compounds gave strong [M + Na]+
ions with
2,5-dihydroxybenzoic acid as the matrix, with no loss of sensitivity with increasing mass as was observed from the corresponding
ions produced by electrospray.
Neutral glycosphingolipids showed negligible in-source fragmentation but sialylated compounds fragmented by loss of
sialic acid. However, these losses were not accompanied by unfocused post-source-decay
ions as observed with MALDI-reflectron-TOF instruments. The MS/MS spectra were almost identical to those obtained by electrospray. Fragmentation of all compounds was mainly by glycosidic cleavage to give
ions, both with and without the
ceramide moiety, which defined the
carbohydrate chain sequence. Weak
ions which defined the
sphingosine chain length and abundant
ions, produced by loss of the acyl chain, were present when this chain contained a 2-hydroxy group. The technique was applied to the identification of
ceramide-trihexosides present in tissues from mice genetically modified to model one of the
glycolipid storage diseases (
Fabry disease).