Hierarchy of lipid structural information
- Species level is the lowest hierarchical level. It represents the Sum composition, i.e., sum of carbon atoms, DBE and number of additional oxygen atoms, e.g. FA 18:1;O. Assumptions by “biological intelligence” need to be stated. Of note, for Sterols the ABCD ring system is assumed and not expressed as DBE.
- Molecular species level annotates Lipid species with identified fatty acyl/alkyl residues, e.g. TG 16:0_18:1_18:1, a triglyceride.
- sn-Position level annotates GL and GP molecular species: Fatty acyl/alkyl constituents at the glycerol backbone are indicated by a slash, e.g. TG 16:0/18:1/18:1.
- DB/DBE-position level annotates species having constituents with Defined position of double bond(s)/double bond equivalent(s), e.g. FA 18:2(9,12);O.
- Phosphate-position level annotates Positions of phosphate group(s), e.g. for phosphatidylinositolphosphates PIP[3’] or PIP2[4’,5’].
- Structure defined level annotates Molecular species with constituents and functional groups, the latter include Triple bonds (Y), e.g. FA 18:2;OH or FA 18:0;Y.
- Full structure level annotates Molecular species with constituents and functional groups including positions, e.g. FA 18:2(9Z,11E);13OH or FA 18:0;9Y.
- Complete structure level annotates Molecular species with constituents and functional groups including positions and stereochemistry (acc. to LMSD), e.g. FA 18:2(9Z,11E);13OH[S] (= common name 13S-HODE).