ESI-MS differential fragmentation of positional isomers of sulfated oligosaccharides derived from carrageenans and agarans |
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Authors: | Alan G Gonçalves Diogo R B Ducatti T Bruce Grindley M Eugênia R Duarte Miguel D Noseda |
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Institution: | 1.Departamento de Farmácia,Universidade Federal do Paraná,Brazil;2.Departamento de Bioquímica e Biologia Molecular,Universidade Federal do Paraná,Curitiba,Brazil;3.Department of Chemistry,Dalhousie University,Halifax,Canada |
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Abstract: | We have prepared a number of isomeric red seaweed galactan-derivative sulfated oligosaccharides to determine whether there
were diagnostic differences among the isomeric mass spectra obtained using ESI CID MS/MS (triple quadrupole instrument). Fragmentation
of the single or multicharged molecular ions from di-, tetra-, and hexasaccharides indicated that the relative positioning
of the sulfate groups and type of monosaccharide unit affect the rate of cleavage of the glycosidic bonds. We also performed
a comparative M-Na]− fragmentation study of positional isomers of sulfated disaccharides that present all four monosulfation possibilities on
the galactopyranosidic ring. In this case, negative-ion ESI CID MS/MS approach gave diagnostic product ions from cross-ring
cleavages along with the same main B1 ion (from sulfated Galp), at m/z 241, for all isomers. The isomeric disaccharides were also submitted to increased spray energy conditions inducing in-source
fragmentation; preformed B1 ions were then fragmented to give similar product ions as those found in M-Na]− analysis. Evaluation of the relative abundances mainly for cross-ring fragment ions at m/z 138, 139, 151, 153 allowed clear distinction among the members of the disaccharide series. The different ratios for m/z 151/153 ions were consistent with the predominance of m/z 153 being related to the cases when the bond involved in the cleavage process links a sulfated carbon. A quadrupole ion trap
instrument (MSn analysis) was also utilized to compare the results obtained with the triple quadrupole instrument. |
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