High mass accuracy and resolution facilitate identification of glycosphingolipids and phospholipids

Natural lipid profiling can improve our current understanding of disease mechanism in a systems biology approach combining genomics, proteomics, and phenotypic changes. However, lipid profiling is complicated by the >10,000 combinations of polar head group, hydrocarbon chain length and degree of unsaturation/hydroxylation, and glycan composition and branching pattern. Here, we show how LC separation coupled with high resolution Fourier transform ion cyclotron resonance mass analysis can quickly narrow down the possible phospholipid and glycosphingolipid compositions. That approach necessitates resolution of mass differences as small as 1.8 mDa [¹²C ₂¹³C₁N₁ (51.0064 Da) vs. H ₃O₃ (51.0082 Da)] in phospholipids and 1.6 mDa [ ¹³C₂S₁H₂ (59.9944 Da) vs. N ₂O₂ (59.9960 Da)] in glycosphingolipids. For novel/unknown lipid species, high mass accuracy based Kendrick mass defect analysis enables quick grouping of related lipid species for subsequent tandem MS structural characterization. For sulfur-containing lipid species, high mass resolution can reveal isotopic fine structure to verify assignment.