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 [12C213C1N1 (51.0064 Da) vs. H3O3 (51.0082 Da)] in phospholipids and 1.6 mDa [13C2S1H2 (59.9944 Da) vs. N2O2 (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.

Figure optionsDownload high-quality image (95 K)Download as PowerPoint slideResearch highlights▶ First resolution of the smallest mass differences in glycosphingolipids (1.6 mDa) and phospholipids (1.8 mDa). ▶ Ultrahigh mass accuracy FT-ICR MS enables quick assignment of phospholipids and glycosphingolipids from an accurate mass based lipid library. ▶ Kendrick mass defect analysis is vital for identification and characterization of previously unknown species or species not included in such a library. ▶ Resolution of isotopic fine structure reveals the presence (and number) of specific atoms in biological glycosphingolipids (e.g., sulfur).