Fig. 1

Building blocks of sphingolipid classes and an example of the in silico MS/MS spectrum. a The structural descriptions and abbreviations for fatty acids, sphingoid bases, and lipid classes are shown. The symbols m, o, and n describe the number of repeated substructures. The capitals L1 and L2 describe the connected modules among sphingoid bases (L1 and L2), fatty acid (L1), and head moieties (L2). b The upper (blue) and lower (red) panels show the experimental MS/MS spectrum and the in silico MS/MS spectrum of HexCer [NS] (d18:1/24:0), respectively. The red arrows indicate bond cleavages. Associated formulas with rearranged hydrogens are shown for each labeled cleavage