Electrospray ionization-linear ion trap-mass spectrometry (ESI-LIT-MS) of the major glycolipid species from F3A fraction. A) MS1 spectrum of permethylated F3A. B) MS2 spectrum of the singly-charged ion species ([M -H + 2 Na]+) at m/z 1371.8 observed in A. C) MS3 spectrum of the major daughter-ion species at m/z 996.7 observed in B. D) Summary of key fragments observed in the MS2 and MS3 spectra of permethylated GM3 species at m/z 1372. For simplification, the proposed GM3 structure is depicted without permethylation. m/z, mass to charge ratio.