Linear ion-trap MSnwith high-resolution MS reveals structural diversity of 1-O-acylceramide family in mouse epidermis.
1-O-acylceramide is a new class of epidermal cer-amide (Cer) found in humans and mice. Here, we report an ESI linear ion-trap (LIT) multiple-stage MS (MSn) approach with high resolution toward structural characterization of this lipid family isolated from mice. Molecular species desorbed as the [M + H]+ions were subjected to LIT MS2to yield predominately the [M + H - H2O]+ions, followed by MS3to cleave the 1-O-acyl residue to yield the [M + H - H2O - (1-O-FA)]+ions. The structures of the N-acyl chain and long-chain base (LCB) of the molecule were determined by MS4on [M + H - H2O - (1-O-FA)]+ions that yielded multiple sets of specific ions. Using this approach, isomers varied in the 1-O-acyl (from 14:0- to 30:0-O-acyl) and N-acyl chains (from 14:0- to 34:1-N-acyl) with 18:1-sphingosine as the major LCB were found for the entire family. Minor isomers consisting of 16:1-, 17:1-, 18:2-, and 19:1-sphingosine LCBs with odd fatty acyl chain or with monounsaturated N- or O-fatty acyl substituents were also identified. An estimation of more than 700 1-O-acylceramide species, largely isobaric isomers, are present, underscoring the complexity of this Cer family.
Division of Nephrology Department of Medicine, Washington University School of Medicine, St. Louis, MO.
Meei-Hua
MH
Lin
Division of Nephrology Department of Medicine, Washington University School of Medicine, St. Louis, MO.
Jeffrey H
JH
Miner
Mass Spectrometry Resource, Division of Endocrinology, Diabetes, Metabolism, and Lipid Research, Department of Medicine, Washington University School of Medicine, St. Louis, MO.
John
J
Turk
Mass Spectrometry Resource, Division of Endocrinology, Diabetes, Metabolism, and Lipid Research, Department of Medicine, Washington University School of Medicine, St. Louis, MO. Electronic address: fhsu@im.wustl.edu.
Fong-Fu
FF
Hsu
D000818:Animals; D002518:Ceramides / Q000737:chemistry* / Q000302:isolation & purification*; D004817:Epidermis / Q000737:chemistry*; D007536:Isomerism; D008055:Lipids / Q000737:chemistry / Q000302:isolation & purification*; D051379:Mice; D015394:Molecular Structure; D021241:Spectrometry, Mass, Electrospray Ionization; D013110:Sphingosine / Q000737:chemistry / Q000302:isolation & purification
D002518:Ceramides; D008055:Lipids; D013110:Sphingosine
electrospray ionization; high-resolution mass spectrometry; higher collision energy dissociation; lipidomics; multiple-stage tandem mass spectrometry; skin ceramide; sphingolipid