Structural characterization of hexoses and pentoses using lead cationization. An electrospray ionization and tandem mass spectrometric study.
The analytical potential of the complexation of isomeric underivatized hexoses (D-glucose, D-galactose, D-mannose, D-talose, D-fructose), methylglycosides (1-O-methyl-alpha-D-glucose and 1-O-methyl-beta-D-glucose) and pentoses (D-ribose, D-xylose, D-arabinose and D-lyxose) by Pb(2+) ions, was investigated by electrospray ionization and tandem mass spectrometry (MS/MS). Pb(2+) ions react mainly with monosaccharides by proton abstraction to generate [Pb(monosaccharide)(m) - H](+) ions (m = 1-3). At low cone voltage, a less abundant series of doubly charged ions of general formula [Pb(monosaccharide)(n)](2+) is also observed. The maximum number n of monosaccharides surrounding a single Pb(2+) ion depends on the metal : monosaccharide ratio. Our study shows that MS/MS experiments have to be performed to differentiate Pb(2+)-coordinated monosaccharides. Upon collision, [Pb(monosaccharide) - H](+) species mainly dissociate according to cross-ring cleavages, leading to the elimination of C(n)H(2n)O(n) neutrals. The various fragmentation processes observed allow the C(1), C(2) and C(4) stereocenters of aldohexoses to be characterized, and also a clear distinction aldoses and fructose. Furthermore, careful analysis of tandem mass spectra also leads to successful aldopentose distinction. Lead cationization combined with MS/MS therefore appears particularly useful to identify underivatized monosaccharides.
Salpin
Jean-Yves
JY
Laboratoire Analyse et Environnement, UMR 8587, Bâtiment des Sciences, Université Evry Val d'Essonne, Boulevard François Mitterrand, 91025 Evry Cedex, France. jean-yves.salpin@chimie.univ-evry.fr
Tortajada
Jeanine
J
D002413:Cations, Divalent / Q000737:chemistry; D006601:Hexoses / Q000737:chemistry*; D007854:Lead / Q000737:chemistry*; D010429:Pentoses / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
D002413:Cations, Divalent; D006601:Hexoses; D010429:Pentoses; D007854:Lead