|Byrdwell, W Craig|
Submitted to: Journal of Chromatography A
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/29/2007
Publication Date: 4/6/2007
Citation: Byrdwell, W.C., Perry, R.H. 2007. Liquid Chromatography with Dual Parallel Mass Spectrometry and 31P Nuclear Magnetic Resonance Spectroscopy for Analysis of Sphingomyelin and Dihydrosphingomyelin. II. Bovine Milk Sphingolipids. Journal of Chromatography A, 1146:164-185 Interpretive Summary: Mass spectrometry is an instrumental technique by which molecules are identified by their masses, and by the masses of fragments that come from them. This report uses mass spectrometry to identify a class of molecules in dairy milk that have been overlooked in the past. Sphingolipids are a type of molecule that produces signals that are passed between cells to initiate cellular events and processes. We used mass spectrometry to identify a class of sphingolipids in cow’s milk that has gone unreported or underreported in the past. We identified 47 individual molecules in one class of sphingolipids and 63 molecules in another class of sphingolipids. This report constitutes the most comprehensive and definitive report on cow’s milk sphingolipids yet published.
Technical Abstract: Liquid chromatography coupled to atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) mass spectrometry (MS), in parallel, was used for simultaneous detection of bovine milk sphingolipids (BMS). APCI-MS mass spectra exhibited mostly ceramide-like fragment ions, [Cer-H2O+H]+ and [Cer-2H2O+H]+, which were used to identify individual molecular species of BMS according to fatty acyl chain length:degree of unsaturation and long-chain base (LCB). ESI-MS was used to confirm the molecular weights of BMS species. Both sphingomyelin (SM) and dihydrosphingomyelin (DSM) molecular species were identified, with DSM species constituting 20% of BMS. Approximately 56 to 58% of DSM species contained a d16:0 LCB, while 34 to 37% contained a d18:0 LCB. Approximately 26 to 30% of SM species contained a d16:1 LCB, while 57 to 60% contained a d18:1 LCB. BMS species contained both odd and even carbon chain lengths. The most abundant DSM species contained a d16:0 LCB with a 22:0, 23:0 or 24:0 fatty acyl chain, while the most abundant SM species contained a d18:1 LCB with a 16:0 or 23:0 fatty acyl chain. 31P NMR spectroscopy was used to conclusively confirm that DSM is a dietary component in BMS.