A systematic nomenclature for carbohydrate fragmentations in FAB-MS/MS spectra of glycoconjugates
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A summary of the ion types observed in the Fast Atom Bombardment Mass Spectrometry (FAB-MS) and collision induced decomposition (CID) MS/MS spectra of glycoconjugates (glycosphingolipids, glycopeptides, glycosides and carbohydrates) is presented. The variety of product ion types that arise by cleavages within the carbohydrate moieties has prompted us to introduce a systematic nomenclature to designate these ions. The proposed nomenclature has been developed primarily for FAB-MS, but can be used as well for other ionization techniques [field desorption (FD), direct chemical ionization (DCI), laser desorption/Fourier transform (LD/FT), etc.], and is applicable to spectra recorded in either the positive or negative ion mode during both MS and MS/MS experiments.
Ai, Bi and Ci labels are used to designate fragments containing a terminal (nonreducing end) sugar unit, whereas Xj, Yj and Zj represent ions still containing the aglycone (or the reducing sugar unit). Subscripts indicate the position relative to the termini analogous to the system used in peptides, and superscripts indicate cleavages within carbohydrate rings.
FAB-MS/MS spectra of a native glycosphingolipid and glycopeptide, and a permethylated ganglioside are shown as illustrations.
Key wordsglycolipids glycopeptides FAB-MS tandem mass spectrometry (MS/MS) nomenclature
fast atom bombardment mass spectrometry
collision induced decomposition
direct chemical ionisation
laser desorption/Fourier transform
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