Data for each timepoint was classified by LIPID MAPS category66 (link): glycerophospholipids, glycerolipids, sphingolipids, sterol lipids, fatty acyls, and prenol lipids were detected. Each category contains distinct subclasses as annotated below. Glycerophospholipids: Phosphatidylcholine (PC), Phosphatidylethanolamine (PE), Phosphatidylserine (PS), Phosphatidylinositol (PI), Methylphosphocholine (MePC), Phosphatidic acid (PA), Bis-methyl phosphatidic acid (BisMePA), Dimethyl phosphatidylethanolamine (dMePE), Phosphatidylgylcerol (PG), Bis-methylphosphatidylserine (BisMePS), Bis-methyl phosphatidyl ethanolamine (BisMePE), Cardiolipin (CL), Phosphatidylethanol (PEt), Biotinyl-phosphoethanolamine (BiotinylPE), Phosphatidylmethanol (PMe), Phosphatidylinositol-bisphosphate (PIP2), Phosphatidylinositol-monophosphate (PIP), Lysophosphatidylcholine (LPC), Lysophosphatidylethanolamine (LPE), Lysophosphatidylserine (LPS), Lysophosphatidylinositol (LPI), Lysophosphosphatidylgylcerol (LPG), Lysodimethyl phosphatidyl ethanolamine (LdMePE). Glycerolipids: Triglyceride (TG), Monogalactosyldiacylglycerol (MGDG), Monogalactosylmonoacylglycerol (MGMG), Diglyceride (DG), Sulfoquinovosylmonoacylglycerol (SQMG), Sulfoquinovosyldiacylglycerol (SQDG). Sphingolipids: Hexosylceramides (Hex1Cer), Simple Glc series (CerG1), Sphingomyelin (SM), Ceramide (Cer), Ceramide phosphate (CerP), Sulfatide (ST), Sphingoid base (So), Sphingomyelin phytosphingosine (phSM), Simple Glc series (CerG2GNAc1), Ceramide phosphorylethanolamine (CerPE), Sphingosine (SPH), Dihexosylceramides (Hex2Cer). Sterol lipids : Cholesterol ester (ChE), Zymosterol (ZyE). Fatty acyls: Fatty acid (FA), Acyl Carnitine (AcCa). Prenol lipids: Coenzyme (Co).
Individual lipid species were annotated according to sum composition of carbons and double bonds in the format Lipid Subclass (total number of carbons: total number of double bonds). If distinct fatty acid chains could be identified, they were annotated separated by an underscore (ex. PC 32:1, or PC (16:0_16:1). Using this approach, we cannot determine the sn-1 or sn-2 positions of the fatty acid chains. Lipid species within the sphingolipid category contain prefixes ‘d’ or ‘t’ to denote di-hydroxy or tri-hydroxy bases. For example, SM(d18:1_23:0) contains 2 hydroxyl groups. The Hex1Cer subclass is comprised of both glucosylceramide (GlcCer) and galactosylceramide (GalCer); the orientation of one of the hydroxyl groups in Glc differs from in Gal, and thus cannot be resolved by these methods 67 (link). Plasmanyl lipid species (ether linked) are annotated by ‘e’ and plasmenyl/plasmalogen (vinyl ether linked) lipid species are annotated by ‘p’ (ex. PC (36:5e) or PE (16:0p_20:4) 68 (link).
Individual lipid species were annotated according to sum composition of carbons and double bonds in the format Lipid Subclass (total number of carbons: total number of double bonds). If distinct fatty acid chains could be identified, they were annotated separated by an underscore (ex. PC 32:1, or PC (16:0_16:1). Using this approach, we cannot determine the sn-1 or sn-2 positions of the fatty acid chains. Lipid species within the sphingolipid category contain prefixes ‘d’ or ‘t’ to denote di-hydroxy or tri-hydroxy bases. For example, SM(d18:1_23:0) contains 2 hydroxyl groups. The Hex1Cer subclass is comprised of both glucosylceramide (GlcCer) and galactosylceramide (GalCer); the orientation of one of the hydroxyl groups in Glc differs from in Gal, and thus cannot be resolved by these methods 67 (link). Plasmanyl lipid species (ether linked) are annotated by ‘e’ and plasmenyl/plasmalogen (vinyl ether linked) lipid species are annotated by ‘p’ (ex. PC (36:5e) or PE (16:0p_20:4) 68 (link).
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