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Stabilization of Sialic Acids in N ‐linked Oligosaccharides and Gangliosides for Analysis by Positive Ion Matrix‐assisted Laser Desorption/Ionization Mass Spectrometry
Author(s) -
Powell Andrew K.,
Harvey David J.
Publication year - 1996
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/(sici)1097-0231(19960715)10:9<1027::aid-rcm634>3.0.co;2-y
Subject(s) - chemistry , mass spectrometry , chromatography , protein mass spectrometry , surface enhanced laser desorption/ionization , matrix assisted laser desorption/ionization , ion , desorption , sample preparation in mass spectrometry , fast atom bombardment , sialic acid , matrix (chemical analysis) , analytical chemistry (journal) , biochemistry , electrospray ionization , organic chemistry , adsorption
Matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry of oligosaccharides and gangliosides normally causes loss of sialic acid, particularly when α‐cyano‐4‐hydroxycinnamic acid is used as the matrix. In addition, the potential signal is split because both positive and, to a greater extent, negative ions are formed while signals are frequently complicated as the result of partial alkali‐salt formation. In order to stabilize the sialic acid moieties under MALDI conditions and to divert all of the signal into the positive‐ion mode, a method involving their conversion into methyl esters has been developed. The method is relatively rapid and produces strong positive‐ion signals from N ‐linked oligosaccharides containing sialic acid and from gangliosides. The latter compounds are stable, even in the presence of α‐cyano‐4‐hydroxycinnamic acid. They give abundant molecular (MNa + ) ions, but with sufficient residual in‐source fragmentation to allow the sequence of the sugar chain to be determined. The sialic acid residue is stable after methylation, irrespective of its linkage to the parent molecule.