The in situ gas-phase formation of a C-glycoside ion obtained during electrospray ionization tandem mass spectrometry. A unique intramolecular mechanism involving an ion-molecule reaction.
BACKGROUND
This study examines the electrospray ionization mass spectrometry (ESI-MS), in-source collision-induced dissociation (CID) fragmentation and low-energy collision-induced dissociation tandem mass spectrometry (CID-MS/MS) of a synthetic pair of β- and α-anomers of the amphiphilic cholesteryl polyethoxy neoglycolipids containing the 2-azido-2-deoxy-D-galactosyl-D-GalN3 moiety. We describe the novel and unique in situ gas-phase formation of a C-glycoside ion formed during all these gas-phase processes and propose a reasonable mechanism for its formation.


METHODS
The synthetic amphiphilic glycolipids were composed of the 2-deoxy-2-azido-D-galactosyl moiety (GalN3, the hydrophilic part) covalently attached to a polyethoxy spacer which is covalently linked to the cholesteryl moiety (hydrophobic part). The 2-azido-2-deoxy-α- and β-D-galactosyl-containing glycolipids were studied by in-time and in-space ESI-MS and CID-MS/MS in positive ion mode, with quadrupole ion trap (QIT), quadrupole-quadrupole-time-of-flight (QqTOF), and Fourier transform ion cyclotron resonance (FTICR) instruments.


RESULTS
Conventional single-stage ESI-MS analysis showed the formation of the protonated molecule. During the single-stage ESI-MS analysis and the CID-MS/MS of the [M+H](+) and [M+NH4](+) adducts obtained from both glycolipid anomers, the presence of a series of specific product ions with different intensities was observed, consistent with the [C-glycoside+H-N2](+), [cholestadiene+H](+), 2-deoxy-2-D-azido-galactosyl [GalN3](+), [GalNH](+) and [sugar-Spacer+H](+) ions.


CONCLUSIONS
The gas-phase formation of the [C-glycoside+H-N2](+) ion isolated from the glycolipid anomers was observed during both the ESI-MS of the glycolipids and the CID-MS/MS analyses of the [M+H](+) ions and it was found to occur by an intramolecular rearrangement involving an ion-molecule complex. CID-QqTOF-MS/MS and CID-FTICR-MS(2) analysis allowed the differentiation of the two glycolipid anomers and showed noticeable variation in the intensities of the product ions.
Department of Biochemistry, Memorial University of Newfoundland, St. John's Newfoundland, 232 Elizabeth Avenue, A1B 3X9, Canada.|Fisheries and Oceans Canada, Science Branch, St. John's Newfoundland, 80 East White Hills Road, A1C 5X1, Canada.|Department of Chemistry, Memorial University of Newfoundland, St. John's Newfoundland, 232 Elizabeth Avenue, A1B 3X7, Canada.
Joseph H
JH
Banoub
Department of Biochemistry, Memorial University of Newfoundland, St. John's Newfoundland, 232 Elizabeth Avenue, A1B 3X9, Canada.
Wael L L
WL
Demian
Department of Chemistry and Chemical Technology, University of Calabria, via P Bucci, Arcavacata di Rende, (CS), Italy.
Paolo
P
Piazzetta
Department of Chemistry, Memorial University of Newfoundland, St. John's Newfoundland, 232 Elizabeth Avenue, A1B 3X7, Canada.
George
G
Sarkis
Helmholtz Zentrum Muenchen, Research Unit Analytical Biogeochemistry, IngolstaedterLandstr. 1, D-85764, Neuherberg, Germany.
Basem
B
Kanawati
ICBMS-UMR 5246, Laboratoire LCO2-GLYCO, Université de Lyon, Université Claude Bernard Lyon 1, 43 bd du 11 Novembre 1918, 69622, Villeurbanne Cedex, France.
Dominique
D
Lafont
ICBMS-UMR 5246, Laboratoire LCO2-GLYCO, Université de Lyon, Université Claude Bernard Lyon 1, 43 bd du 11 Novembre 1918, 69622, Villeurbanne Cedex, France.
Nicolas
N
Laurent
Department of Chemistry, Memorial University of Newfoundland, St. John's Newfoundland, 232 Elizabeth Avenue, A1B 3X7, Canada.
Celine
C
Vaillant
Division of Laboratory Medicine, Faculty of Medicine, Memorial University of Newfoundland, Health Sciences Centre, 300 Prince Philip Drive, St. John's Newfoundland, A1B 3V6, Canada.
Edward
E
Randell
Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Via Aldo Moro, I-53100, Siena, Italy.
Gianluca
G
Giorgi
Department of Chemistry, Memorial University of Newfoundland, St. John's Newfoundland, 232 Elizabeth Avenue, A1B 3X7, Canada.
Travis D
TD
Fridgen
D006017:Glycolipids / Q000737:chemistry; D006027:Glycosides; D007477:Ions / Q000737:chemistry; D008958:Models, Molecular; D009005:Monosaccharides / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods*
C438934:C-glycoside; D006017:Glycolipids; D006027:Glycosides; D007477:Ions; D009005:Monosaccharides