Localization of the O-glycosylated sites in peptides by fixed-charge derivatization with a phosphonium group.
The present study demonstrates that matrix-assisted laser desorption ionization/postsource decay (MALDI/PSD) analysis of the molecular cation of glycopeptides derivatized at their amino terminus with a phosphonium group cleaves peptide backbone without removing the glycan. The predictable a-type fragment ions retain the glycan moiety, enabling unambiguous localization of O-glycans on the peptide chain. In contrast, collision-activated dissociation tandem mass spectrometry analysis carried out on the doubly charged protonated phosphonium cation results in the predominant loss of the sugar moiety from the peptide. This result supports the previously proposed charge-induced fragmentation mechanism of the sugar-peptide bond. MALDI/PSD analysis of glycopeptides converted to their acetyl phosphonium derivatives is an effective alternative to electron capture dissociation, as illustrated by the positioning of up to three GalNac residues along the full tandem repeat peptide sequence derived from the MUC 5AC mucin.
UMR 8576 CNRS, Glycobiologie Structurale et Fonctionnelle, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq Cedex, France.
Xavier
X
Czeszak
Willy
W
Morelle
Guy
G
Ricart
Daniel
D
Tétaert
Jérôme
J
Lemoine
D000595:Amino Acid Sequence; D006020:Glycopeptides / Q000737:chemistry*; D006031:Glycosylation; D008969:Molecular Sequence Data; D063065:Organophosphonates; D010455:Peptides / Q000737:chemistry*; D011134:Polysaccharides / Q000032:analysis*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D006020:Glycopeptides; D063065:Organophosphonates; D010455:Peptides; D011134:Polysaccharides