Mixed-acyl glycerophospholipids are among the most abundant lipids in nature. Famously, 1-palmitoyl-2-oleoyl phosphatidylcholine (POPC) is the most abundant phospholipid in most eukaryotic cells and tissues. The molecular structure of POPC follows the textbook consensus that unsaturated fatty acyl chains occupy the sn-2 position of the glycerol backbone while saturated fatty acyl chains are relegated to the sn-1 position. As our analytical technologies advance, this conventional wisdom is being turned inside out with the isomer 1-oleoyl-2-palmitoyl phosphatidylcholine (OPPC) being identified at high abundance in samples ranging from plasma to tissue [1,2,3]. Adding to the complexity, both isomers are present in many instances in ratios ranging from 1:100 to 1:1. Resolving the puzzle of lipid isomers requires advanced analytical tools in conjunction with structurally defined reference materials. Until recently, commercially available synthetic lipids were also comprised of mixtures, as transacylation occurring in the round-bottom flask always led to 10-20% OPPC in any preparation of POPC. Moreover, the regiopurity of the product was difficult to define. Avanti has now introduced the IsoPure line wherein innovative synthetic procedures produce mixed-acyl glycerophospholipids with >99% regiopurity. These next-generation standards will be pivotal to isomer-resolved identification of glycerophospholipids in biological samples.

[1] Ekroos K, Ejsing CS, Bahr U, Karas M, Simons K, Shevchenko A. Charting molecular composition of phosphatidylcholines by fatty acid scanning and ion trap MS3 fragmentation. J. Lipid Res. 2003, 44, 2181. PMID: 12923235

[2] Zacek P, Bukowski M, Rosenberger TA, Picklo M. Quantitation of isobaric phosphatidylcholine species in human plasma using a hybrid quadrupole linear ion-trap mass spectrometer. J. Lipid Res. 2016, 57, 2225. PMID: 27688258

[3] Maccarone AT, Duldig J, Mitchell TW, Blanksby SJ, Duchoslav E, Campbell JL. Characterization of acyl chain position in unsaturated phosphatidylcholines using differential mobility-mass spectrometry.J. Lipid Res. 2014, 55, 1668. PMID: 24939921