Fig. 4: Structural elucidations of very long-chain PUFA-containing phosphatidylcholine (PC).

The result of in-depth lipidome profiling is shown by the scatter plot of retention time- and m/z axis. The annotation results of molecular species (MSL), double-bond (DB) resolved, sn- or OH-positions (SN or OH) resolved, and both sn- and DB- or both OH- and DB-position (SN + DB or OH + DB) resolved levels are described by the same color charts used in Fig. 2b. The sn1-position determined or uncharacterized for VLC-PUFA is described by triangle and diamond symbols, respectively. The bottom-right panel describes the experimental spectrum of the lipid ion annotated as PC 34:6(16,19,22,25,28,31)/22:6(4,7,10,13,16,19), where the E/Z isomer definition in acyl chains is unsupported, yet a representative form is shown. The top panel displays a 50-fold zoomed experimental spectrum and a 10-fold zoomed in silico spectrum of the assigned lipid in the upper and lower panels, respectively. Brown, green, orange, and red spectral peaks represent ions related to homolytic cleavages in acyl chains, lyso PC substructures, neutral loss of sn1-34:6 moiety, and precursor- or polar head-specific fragments, respectively. Source data are provided as a Source Data file.