Molecular species of sphingomyelin: determination by high-performance liquid chromatography/mass spectrometry with electrospray and high-performance liquid chromatography/tandem mass spectrometry with atmospheric pressure chemical ionization.
In a sphingomyelin-enriched sample of polar lipids from bovine milk, molecular species of intact sphingomyelin were separated by normal-phase high-performance liquid chromatography and detected by mass spectrometry (MS) for structural information. First, by using electrospray with positive ionization (ESI), protonated molecules ([M + H]+) were detected. Second, in atmospheric pressure chemical ionisation (APCI+), in-source fragmentation of sphingomyelin ions led to the formation of ceramide ions. With the ceramide ions as precursors, ions representative of both the long-chain base (LCB) parts and the fatty acid (FA) parts were detected in APCI-MS/MS via collision-induced decomposition (CID). Using this procedure, it was possible to determine the sphingomyelin molecular masses using ESI+ and then their respective LCB-FA combinations(s) using APCI+(-)MS/MS. At least 36 protonated molecules of intact sphingomyelin were detected in the bovine milk sample. The combinations found covered a range of molecular masses from 673 to 815 Da. The 12 most common protonated molecules (constituting approximately 90% of the total ion current in ESI) were composed of at least 25 different LCB-FA combinations. Saturated and unsaturated LCBs and FAs were detected in addition to hydroxy fatty acids. The most common LCBs were 16:1, 17:1, 18:1 and 19:1, whereas the most common FAs were 16:0, 22:0, 23:0 and 24:0. LCB-FA combinations of sphingomyelin from bovine brian, bovine erythrocytes and chicken egg yolk are also presented.
Karlsson
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AA
Nycomed Innovation AB, Ideon-Malmö, Sweden. anders.karlsson@nycomedin.ideon.se
Michélsen
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P
Odham
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G
D000818:Animals; D001923:Brain Chemistry; D002417:Cattle; D002645:Chickens; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004912:Erythrocytes / Q000737:chemistry; D005227:Fatty Acids / Q000097:blood / Q000737:chemistry / Q000302:isolation & purification; D005260:Female; D013058:Mass Spectrometry / Q000379:methods*; D008892:Milk / Q000737:chemistry; D015394:Molecular Structure; D010063:Ovum / Q000737:chemistry; D013109:Sphingomyelins / Q000097:blood / Q000737:chemistry* / Q000302:isolation & purification
D005227:Fatty Acids; D013109:Sphingomyelins