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Fig. 7. Detection of ceramide, GalCer (HexCer), and LacCer in neutral glycosphingolipid brain extracts. Electrospray ionization-tandem MS (ESI-MS/MS) positive mode precursor ion spectra using the specific fragments m/z + 264 (A and B) or m/z + 292 (C) produced in the collision chamber of the instrument. Neutral glycosphingolipid extracts were from wild-type (WT) (A) and Galgt1 Siat9 double-null (B and C) mice. Sphingolipids containing d18:1 or t18:1 sphingoid bases were detected specifically by the fragment m/z 264, and those containing d20:1 or t20:1 sphingoid bases were detected specifically by the fragment m/z 292. Protonated Cer species were m/z 538 (d18:1,16:0), m/z 566 (d18:1,18:0), and m/z 648 (d18:1,24:1). Protonated HexCer species were as follows: m/z 728 (d18:1,18:0), m/z 744 (d18:1,h18:0), m/z 782 (d18:1,22:1), m/z 784 (d18:1,22:0), m/z 800 (d18:1,h22:0), m/z 810 (d18:1,24:1), m/z 812 (d18:1,24:0), m/z 826 (d18:1,h24:1), and m/z 828 (d18:1,h24:0). Protonated LacCer species were m/z 890 (d18:1,18:0) and m/z 918 (d20:1,18:0). The y axis represents the intensity of the measured MS signal as percent of the base peak. The base peak is the most intense peak of the spectrum, which is set to 100%.

Fig. 8. Detection of sulfatides. ESI-MS/MS negative mode precursor ion spectra m/z –97 of mice brain acidic glycosphingolipids extracts. Sulfatides were detected specifically by the fragment [HSO₄]^– (m/z 97) produced in the collision chamber of the instrument. (A) WT mice. (B) Galgt1 Siat9 double-null mice. Deprotonated SM4 species were as follows: m/z 806 (d18:1,18:0), m/z 822 (d18:1,h18:0), m/z 834 (d18:1,20:0), m/z 850 (d18:1,h20:0), m/z 860 (d18:1,22:1), m/z 862 (d18:1,22:0), m/z 876 (d18:1,h22:1), m/z 878 (d18:1,h22:0), m/z 888 (d18:1,24:1), m/z 890 (d18:1,24:0), m/z 904 (d18:1,h24:1), and m/z 906 (d18:1,h24:0). Deprotonated SM3 species were m/z 968 (d18:1,18:0) and m/z 996 (d20:1,18:0). The y axis represents the intensity of the measured MS signal as percent of the base peak. The base peak is the most intense peak of the spectrum, which is set to 100%.