title: Ionization and collision-induced fragmentation of N-linked and related carbohydrates using divalent cations.
abstract: Maltoheptaose and several N-linked glycans were ionized by electrospray as adducts with the divalent cations Mg2+, Ca2+, Mn2+, Co2+ and Cu2+. [M + metal]2+ ions were the major species in all cases with calcium giving the highest sensitivity. In addition, copper gave [M + Cu]+ ions. Other cations gave singly charged ions only by elimination of a protonated monosaccharide. Fragmentation of the [M + metal]2+ ions produced both singly and doubly charged ions with the relative abundance of doubly charged ions decreasing in the order Ca > Mg > Mn > Co > Cu. Singly charged ions were formed by elimination of a protonated monosaccharide residue followed, either by successive monosaccharide residue losses, or by a 2,4A cross-ring cleavage of the reducing-terminal monosaccharide. Formation of doubly charged fragments from [M + metal]2+ ions involved successive monosaccharide-residue losses either with or without O,2A or 2,4A cross-ring cleavages of the reducing-terminal monosaccharide. Abundant diagnostic doubly charged ions formed by loss of the 3-antenna from the O,2A cross-ring product were specific to [M + Ca]2+ ions. Fragmentation of [M + Cu]+ ions was similar to that of the corresponding [M + H]+ ions in that most cross-ring fragments were absent.
authors.affiliation: Depart of Biochemistry, Oxford Glycobiology Institute, UK. dh@glycob.ox.ac.uk
authors.forename: D J
authors.initials: DJ
authors.lastname: Harvey
mesh_terms: D002118:Calcium / Q000737:chemistry; D002413:Cations, Divalent; D003035:Cobalt / Q000737:chemistry; D003300:Copper / Q000737:chemistry; D005690:Galactose / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry; D005936:Glucans / Q000737:chemistry*; D008274:Magnesium / Q000737:chemistry; D008345:Manganese / Q000737:chemistry; D009005:Monosaccharides / Q000737:chemistry*; D010047:Ovalbumin / Q000737:chemistry*; D011134:Polysaccharides / Q000737:chemistry*; D012260:Ribonucleases / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D002413:Cations, Divalent; D005936:Glucans; D009005:Monosaccharides; D011134:Polysaccharides; C031146:maltoheptaose; D003035:Cobalt; D008345:Manganese; D003300:Copper; D010047:Ovalbumin; D012260:Ribonucleases; C029600:ribonuclease B; D008274:Magnesium; D002118:Calcium; D005690:Galactose