Resolving Modifications on Sphingoid Base and N-Acyl Chain of Sphingomyelin Lipids in Complex Lipid Extracts

摘要: Sphingomyelins (SMs) are an essential class of lipids widely existing in different organisms. The sphingoid base and N-acyl chain two building blocks which can undergo types modifications during lipogenesis, including desaturation, hydroxylation, methyl branching. Current lipidomic analysis methods cannot provide detailed information on these structural motifs. Herein, we developed a tandem mass spectrometric method by harnessing radical-directed dissociation (RDD) from collision-induced (CID) the bicarbonate anion adduct SM ([M + HCO3]-). A major RDD channel produced high-abundance fragment carrying intact chain, termed as "N-acyl fragment", allowing assignment base/N-acyl composition relative quantitation compositional isomers at high sensitivity. also intrachain fragments lower abundances, helped localization branching hydroxylation SM. acetone Paterno-Buchi (PB) reaction was found to be capable derivatizing Δ4 carbon-carbon double bond (C═C) sphingosine (SPH) producing C═C diagnostic ions upon CID, albeit much efficiencies than those isolated alkyl chains. liquid chromatography-mass spectrometry workflow incorporating MS2 CID via [M HCO3]- PB-MS2 CID. capability profiling with demonstrated analyzing complex lipid extracts porcine brain Caenorhabditis elegans. These results provided visualization revealed large diversity each sample. included identification sphingadiene [d18:1(Δ4,14)], location N-acyls, C-2 iso-methyl branched SPH base.