Structural identification of m/z 738, 764, and 766 as plasmalogen PEs with the use of MS/MS. (A) Negative LC/MS/MS of m/z 738→319 and 738→115 from ionophore-activated neutrophil lipid extract. (Left insert) Negative MS/MS spectrum at 24.8 minutes from neutrophil lipid. (Right insert) Negative MS/MS spectrum of m/z 738 generated by 5-LOX oxidation of brain PE, eluting at 24.8 minutes. (B) Negative LC/MS/MS of m/z 764→319 and 764→115 from ionophore-activated neutrophil lipid extract. (Left inset) Negative MS/MS spectrum at 25.3 minutes from neutrophil lipid. (Right inset) Negative MS/MS spectrum of m/z 764 generated by 5-LOX oxidation of brain PE, eluting at 25.3 minutes. (C) Negative LC/MS/MS of m/z 766→319 and 766→115 from ionophore-activated neutrophil lipid extract. (Left inset) Negative MS/MS spectrum at 27.5 minutes from neutrophil lipid. (Right inset) Negative MS/MS spectrum of m/z 766 generated by 5-LOX oxidation of brain PE, eluting at 27.5 minutes.