Structural determination of glycosphingolipids as lithiated adducts by electrospray ionization mass spectrometry using low-energy collisional-activated dissociation on a triple stage quadrupole instrument
Ff. Hsu et J. Turk, Structural determination of glycosphingolipids as lithiated adducts by electrospray ionization mass spectrometry using low-energy collisional-activated dissociation on a triple stage quadrupole instrument, J AM SOC M, 12(1), 2001, pp. 61-79
Citations number
24
Categorie Soggetti
Spectroscopy /Instrumentation/Analytical Sciences
Journal title
JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY
Structural characterization of glycosphingolipids as their lithiated adduct
s using low-energy collisional-activated dissociation (CAD) tandem mass spe
ctrometry with electrospray ionization (ESI) is described. The tandem mass
spectra contain abundant fragment ions reflecting the long chain base (LCB)
, fatty acid, and the sugar constituent of the molecule and permit unequivo
cal identification of cerebrosides, di-, trihexosyl ceramides and globoside
s. The major fragmentation pathways arise from loss of the sugar moiety to
yield a lithiated ceramide ion, which undergoes further fragmentation to fo
rm multiple fragment ions that confirm the structures of the fatty acid and
LCB. The mechanisms for the ion formation and the possible configuration o
f the fragment ions, resulting from CAD of the lithiated molecular ions ([M
+ Li](+)) of monoglycosylceramides are proposed. The mechanisms were suppo
rted by CAD and source CAD tandem mass spectra of various cerebrosides and
of their analogous molecules prepared by H-D exchange. Constant neutral los
s and precursor ion scannings to identify galactosylceramides with sphingos
ine or sphinganine LCB subclasses, and with specific N-2-hydroxyl fatty aci
d subclass in mixtures are also demonstrated. (C) 2001 American Society for
Mass Spectrometry.