Structural Characterization of Neutral Saccharides by Negative Ion MALDI Mass Spectrometry Using a Superbasic Proton Sponge as Deprotonating Matrix

• DOI: 10.1007/s13361-017-1679-y
• Publication Date: 2017-05-02T13:52:32Z
• Authors: Cosima Damiana Ca...; Tommaso R. I. Cat...; Julius F. Kögel; Antonio Monopoli; Francesco Palmisano; Jorge Sundermeyer
• Keywords: Glycosidic bond; Disaccharide; Fragmentation

The superbasic proton sponge 1,8-bis(tripyrrolidinylphosphazenyl)naphthalene (TPPN) has been successfully employed for the structural characterization of neutral saccharides, cyclodextrins, and saccharide alditols by matrix assisted laser desorption/ionization tandem mass spectrometry (MALDI-MS/MS). Owing to its inherently high basicity, TPPN is capable deprotonating carbohydrates (M) providing an efficient simple way produce gas-phase [M - H]- ions. Highly informative negative ions MS/MS spectra showing several diagnostic fragment were obtained, mainly A-type cross-ring C-type glycosidic cleavages. Indeed, cleavages monosaccharides with formation 0,2A, 0,3A, 2,4A, 2,5A, 3,5A, 0,3X product dominate spectra. A significant difference between reducing (e.g., lactose, maltose) non-reducing disaccharides sucrose, trehalose) was observed. Though anomeric positions blocked give rise deprotonated molecules, H]-, at m/z 341.1, ones exhibited a peak 340.1, most likely as radical anion, H•- H]-•. superiority clearly demonstrated comparison well recognized matrices, such 2,5-dihydroxybenzoic acid 2',4',6'-trihydroxyacetophenone (positive ion mode) nor-harman (negative mode). MALDI experiments on isotopically labeled sugars have greatly supported interpretation plausible fragmentation pathways. Graphical Abstract ᅟ.