Application of matrix-assisted laser desorption ionization time-of-flight mass spectrometry with delayed ion extraction to ganglioside analyses.
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 alpha-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 gangliosides than alpha-cyano-4-hydroxycinnamic acid, because this matrix seemed to minimize loss of sialic acid and carbon dioxide of gangliosides. About 1 pmol of ganglioside was able to be detected with this matrix. When "A-series" gangliosides such as GD1a and GalNAc-GD1a gave undesirable extra peaks probably due to loss of sialic acid besides molecule-related ion peaks, the methyl-esterification of the gangliosides 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" gangliosides 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 GD1a 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 gangliosides was amenable to the identification of them by DE MALDI-TOF MS.
Sugiyama
E
E
Department of Biochemistry, Research Center on Aging and Adaptation, Shinshu University School of Medicine, Matsumoto, Nagano, Japan.
Hara
A
A
Uemura
K
K
Taketomi
T
T
D002236:Carbohydrate Conformation; D002518:Ceramides / Q000737:chemistry*; D003373:Coumaric Acids; D005732:Gangliosides / Q000737:chemistry*; D005841:Gentisates; D062385:Hydroxybenzoates; D007202:Indicators and Reagents; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
D002518:Ceramides; D003373:Coumaric Acids; D005732:Gangliosides; D005841:Gentisates; D062385:Hydroxybenzoates; D007202:Indicators and Reagents; C007175:alpha-cyano-4-hydroxycinnamate; C010925:2,5-dihydroxybenzoic acid