Characterization of a complex mixture of ceramides by fast atom bombardment and precursor and fragment analysis tandem mass spectrometry

Abstract

Fast atom bombardment, precursor and fragment ion analysis mass spectrometry were employed to characterize the fatty acid and long-chain base composition of a complex ceramide mixture prepared from beef brain lipids. Precursor ion analysis of a sphingenine-specific fragment allowed selective recognition of ceramides with different fatty acids, some of which escaped undetected in the source spectra owing to background contamination of the FAB matrix. The use of a triple quadrupole yielded far better results than linked scanning on a sector mass spectrometer, owing to unit mass resolution of the precursor ions, which allows discrimination of saturated from unsaturated acids with the same number of carbon atoms. The composition of the mixture of linked fatty acid was derived from the intensity of the molecular species both in the source and in the precursor spectra, and was compared with that obtained by capillary gas chromatography of the released fatty acid methyl esters. Some discrepancy between the values obtained with the two techniques can be attributed to very different surface activity of the short-and long-chain fatty acids. Analysis of the fragment ions following collision-induced decomposition of cationized species allowed localization of the position of the double bond in a ceramide containing a C-24:l fatty acyl chain.

Structural determination of glucosylceramides isolated from marine sponge by fast atom bombardment collision‐induced dissociation linked scan at constant B/E

“…In other words, these odd‐numbered ions may result from simple CC bond cleavage, without accompanying H‐rearrangement, giving distonic radical cations. These fragmentation patterns are consistent with those of previous reports of low‐energy CID–ESI–MS/MS of [Lipid + alkaline metal] + ions 18, 19…”

“…Mass spectrometry (MS) is an important analytical tool for the structural study of compounds extracted from trace biological samples. The structures of SLs have been elucidated by various MS ionization methods, including electron ionization (EI),12, 13 chemical ionization (CI),14 electrospray ionization (ESI),15, 16 atmospheric pressure chemical ionization,17 and fast atom bombardment (FAB) 18–20. EI and CI mass spectrometry are accompanied by derivatization reactions, such as permethylation for sequence analysis.…”

Structural determination of cerebrosides isolated from Asterias amurensis starfish eggs using high‐energy collision‐induced dissociation of sodium‐adducted molecules

“…Several analytical methods have been used to study glycosphingolipids extracted from biological samples 6, 7. Mass spectrometry is an important procedure for structural studies, and the structures of sphingolipids have been characterized using various ionization methods, including electron ionization (EI),8, 9 electrospray ionization (ESI),10, 11 and fast atom bombardment (FAB) 12–14. Recently, ESI tandem mass spectrometry (MS/MS) connected to liquid chromatography has been used to isolate and identify mixtures of sphingolipids, and low‐energy collision‐induced dissociation (CID) MS/MS has also been used in structural analyses 15–17.…”

New ceramides from Rantherium suaveolens

“…The aforementioned spectral data were in good agreement with those reported for phytosphingosine-type ceramides possessing a 2-hydroxyl fatty acyl moiety (10-15). The base peak at m/z 316 in the FABMS, and the lack of corresponding signals differing from 14 amu suggested the occurrence of a common C-18 LCB [C 14 H 27 -CH(OH)-CH(OH) -CH(CH 2 OH)-NH-] in the structures of 1-5(15,16). The position of the double bond could be deduced from the following evidence: The methyl protons at δ 0.82 showed 2 J and 3 J HMBC correlations with carbons at δ 26.1 (C-17) and 32.8 (C-16), whereas HMBC and COSY cross signals were observed between C-16 and the olefinic proton at δ 5.34 (H-15), and between H-15 and H-16, respectively.…”