Proposal for a common nomenclature for fragment ions in mass spectra of lipids
Fragment ion m/z values are denoted according to the three-step procedure outlined in Fig 2. The shorthand notation includes nomenclature based on both charged and neutral fragments (separated by “|”) (step 2). Annotation shown in boldface is prioritized based on the guidelines outlined in Fig 2 (step 3). Non-prioritized shorthand notation is occasionally omitted to avoid overly congested mass spectra. The representation of fragment ion m/z values by mass-balanced chemical reactions and fragment structures are shown in S3 Fig (step 1). A) Negative FTMS2 spectrum of deprotonated ACoA 19:0. B) Positive FTMS2 spectrum of ammoniated TAG 18:0–18:1–18:2. C) Positive FTMS2 spectrum of protonated PE O-18:1p/20:4. D) Negative FTMS2 spectrum of deprotonated and doubly charged CL 14:1–14:1–14:-15:1. E) Negative FTMS3 spectrum of FA 18:1 carboxylate anion m/z 281.3 derived from PC 16:0–18:1(9). F) Positive FTMS2 spectrum of protonated SM 18:1;2/17:0. G) Negative FTMS2 spectrum of deprotonated Cer 18:1;2/17:0;1. H) Positive FTMS2 spectrum of ammoniated SE 27:1/19:0 (cholesteryl ester 19:0).