Extended Data Fig. 2: Tandem mass spectra analysis determined sphingolipid intermediate structures.
From: Human gut bacteria produce structurally related monoglycolipids with contrasting immune functions
To assign the structures unambiguously, we chose chain length variants of major sphingolipid species, whose synthetic version was available. a) MS/MS spectra of B. fragilis KDS (C18:0) matched those of the synthetic standard. b) MS/MS spectra of synthetic C35:1 ceramide (m/z 568.53) was displayed. c) The parent ion with an m/z value of 570.53 from B. fragilis was structurally assigned as C35:0 dihydroceramide. d) The parent ion of m/z 568.53 from B. fragilis ΔcerR was assigned as C35:0 ketoCer. Comparison with isobaric C35:1 ceramide (Panel b) exhibits a distinct fragmentation pattern, as shown by the presence and absence of m/z 264 (300-2H2O). e-f) MS/MS spectra of C34:0 ketoCer and dhCer from B. fragilis were shown.
