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Structural analysis of O‐glycopeptides employing negative‐ and positive‐ion multi‐stage mass spectra obtained by collision‐induced and electron‐capture dissociations in linear ion trap time‐of‐flight mass spectrometry
Author(s) -
Deguchi Kisaburo,
Ito Hiroki,
Baba Takashi,
Hirabayashi Atsumu,
Nakagawa Hiroaki,
Fumoto Masataka,
Hinou Hiroshi,
Nishimura ShinIchiro
Publication year - 2007
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.2885
Subject(s) - chemistry , ion , mass spectrometry , mass spectrum , analytical chemistry (journal) , ion trap , collision induced dissociation , time of flight , chromatography , tandem mass spectrometry , organic chemistry
Structural analyses of various glycans attached to proteins and peptides are highly desirable for elucidating their biological roles. An approach based on mass spectrometry (MS) combining both collision‐induced dissociation (CID) and electron‐capture dissociation (ECD) in the positive‐ and negative‐ion modes has been proposed as a simple and direct method of assigning an O‐glycan without releasing it from the peptide and of determining the amino acid sequence of the peptide and glycosylation site. The instrument used is an electrospray ionization (ESI) linear ion trap (LIT) time‐of‐flight (TOF) mass spectrometer with tandem LITs for CID by He gas and ECD. The proposed approach was tested with two synthetic O‐glycopeptides binding a sialyl Lewis x (sLe x ) oligosaccharide and a 3′‐sialyl N ‐acetyllactosamine (3′‐SLN) on a serine (S) residue. In the negative‐ion mode, the CID MS 2 spectra of O‐glycopeptides showed a relatively abundant glycoside‐bond cleavage between the core N ‐acetylglucosamine (GlcNAc) and serine (S) that yields deprotonated C 3 ‐type fragment ions of O‐glycan and deprotonated Z 0 ‐type peptide ions. The structure of the sLe x (3′‐SLN) oligosaccharide was simply assigned by comparing the CID MS 3 spectrum derived from the C 3 ‐type fragment ion with the CID MS 2 spectra of the sLe x and sLe a (3′‐ and 6′‐SLN) standards (i.e., negative‐ion MS n spectral matching). The amino acid sequence of the peptide including the glycosylation site was determined from the ECD MS 2 spectrum in the positive‐ion mode. Copyright © 2007 John Wiley & Sons, Ltd.