title: Electrospray mass spectrometry and fragmentation of N-linked carbohydrates derivatized at the reducing terminus.
abstract: Derivatives were prepared from N-linked glycans by reductive amination from 2-aminobenzamide, 2-aminopyridine, 3-aminoquinoline, 2-aminoacridone, 4-amino-N-(2-diethylaminoethyl)benzamide, and the methyl, ethyl, and butyl esters of 4-aminobenzoic acid. Their electrospray and collision-induced dissociation (CID) fragmentation spectra were examined with a Q-TOF mass spectrometer. The strongest signals were obtained from the [M + Na]+ ions for all derivatives except sugars derivatized with 4-amino-N-(2-diethylaminoethyl)benzamide which gave very strong doubly charged [M + H + Na]2+ ions. The strongest [M + Na]+ ion signals were obtained from the butyl ester of 4-aminobenzoic acid and the weakest from 2-aminopyridine. The most informative spectra were recorded from the [M + Li]+ or [M + Na]+ ions. These spectra were dominated by ions produced by sequence-revealing glycosidic cleavages and "internal" fragments. Linkage-revealing cross-ring cleavage ions were reasonably abundant, particularly from high-mannose glycans. Although the nature of the derivative was found to have little effect upon the fragmentation pattern, 3-aminoquinoline derivatives gave marginally more abundant cross-ring fragments than the other derivatives. [M + H]+ ions formed only glycosidic fragments with few, if any, cross-ring cleavage ions. Doubly charged molecular ions gave less informative spectra; singly charged fragments were weak, and molecular ions containing hydrogen ([M + 2H]2+ and [M + H + Na]2+) fragmented as the [M + H]+ singly charged ions with no significant cross-ring cleavages.
authors.affiliation: Department of Biochemistry, Oxford Glycobiology Institute, United Kingdom. dh@glycob.ox.ac.uk
authors.forename: D J
authors.initials: DJ
authors.lastname: Harvey
mesh_terms: D000586:Amination; D002240:Carbohydrate Sequence; D002241:Carbohydrates / Q000737:chemistry*; D013058:Mass Spectrometry / Q000379:methods*; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D011134:Polysaccharides / Q000737:chemistry; D019163:Reducing Agents; D012545:Schiff Bases; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D002241:Carbohydrates; D011134:Polysaccharides; D019163:Reducing Agents; D012545:Schiff Bases