Fig. 3.

Precursor LC/MS/MS identification of HODE EOx in the human skin. Human epidermal breast tissue was prepared and analyzed as described in Materials and methods. A: Precursor scan for m/z 295.2 ([M-H]⁻ for HODE) shows a series of ions eluting between 15 and 30 min, labeled 1–9. These are identified as EOS, EOH, and EOP epoxy-HODE ceramides with varying very-long-chain fatty acid carbon numbers. B–D: Representative chromatograms and MS/MS spectra of C32 EOS, EOH, and EOP HODE ceramides detected as precursor ([M-H+CH₃CO₂H]⁻) → 295.2. MS/MS spectra were acquired in the ion trap mode at the apex of elution for each lipid as described. EOH, hydroxysphingosine; EOP, phytosphingosine; EOS, esterified omega-hydroxy sphingosine; EOx, omega-hydroxy sphingosine/phytosphingosine/hydroxysphingosine.