Application of matrix-assisted laser desorption ionization time-of-flight mass spectrometry with delayed ion extraction to ganglioside analyses

• Published in: Glycobiology (Oxford) 1997-07, Vol.7 (5), p.719-724
• Main Authors: Sugiyama, Eiko, Hara, Atsushi, Uemura, Kei-ichi, Taketomi, Tamotsu
• Format: Article
• Language: English
• Subjects: Carbohydrate Conformation; Ceramides - chemistry; Coumaric Acids; delayed ion extraction; gangliosides; Gangliosides - chemistry; Gentisates; Hydroxybenzoates; Indicators and Reagents; matrix-assisted laser desorption ionization time-of-flight mass spectrometry; methyl ester of gangliosides; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization - methods
• ISSN: 0959-6658; 1460-2423
• DOI: 10.1093/glycob/7.5.719

Various monosialo- and disialo-gangliosides and their derivatives were examined by delayed ion extraction matrix-assisted laser desorption ionization time-of-flight mass spectrometry (DE MALDI-TOF MS) in the reflector mode with α-cyano-4-hydroxycinnamic acid or 2,5-dihydroxybenzoic acid used as the matrix. Native gangliosides were generally found to give good spectra in the negative ion mode. 2,5-Dihydroxybenzoic acid was a better matrix for gangiiosides than a-cyano-4-hydroxycinnamic acid, because this matrix seemed to minimize loss of sialic acid and carbon dioxide of gangiiosides. About 1 pmol of gan-glioside was able to be detected with this matrix. When “A-series” gangiiosides such as GD1a and Ga1NAc-GD1a gave undesirable extra peaks probably due to loss of sialic acid besides molecule-related ion peaks, the methyl-esterification of the gangiiosides at the carboxyl groups of sialic acids was found to be necessary to obtain good DE MALDI-TOF mass spectra in the positive ion mode. In contrast, “B-series” gangiiosides such as GD1b, GD2, and GD3 gave rise to major dehydrated molecule-related ion [M-H2O-H]− peaks in the negative ion mode without the pretreatment of methyl-esterification. The DE MALDI-TOF mass spectrometric analysis enabled us to distinguish between GDla and GD1b, which have the same molecular weight It was also found that not only a purified sample, but also a mixed sample of various gangiiosides was amenable to the identification of them by DE MALDI-TOF MS.