Table 2. Compositional assignments of singly charged sodiated molecular ions [M + Na]+, observed in MALDI-TOF mass spectrometry spectra of permethylated GSL from MCF-7, Hs578T and MDA-MB-231 cells.
| Fatty acids | GSL | Calculated mono-isotopic molecular masses | MCF-7 | Hs578T | MDA-MB-231 |
|---|---|---|---|---|---|
| 16:0 | LacCer | 1010.7485 | - | - | 1010.75 |
| 24:0 | LacCer | 1122.8743 | - | - | 1122.88 |
| 16:0 | Gb3 | 1214.8483 | - | - | 1214.85 |
| 24:0 | Gb3 | 1326.9741 | - | - | 1326.98 |
| 16:0 | GA2 | 1255.8748 | - | 1255.85 | - |
| 24:0 | GA2 | 1367.9736 | - | 1367.98 | - |
| 16:0 | GM3 | 1371.9222 | 1371.91 | 1371.90 | 1371.94 |
| 24:0 | GM3 | 1484.0480 | 1484.04 | 1484.03 | 1484.06 |
| 16:0 | Gb4 | 1459.9746 | 1459.98 | 1459.96 | 1460.02 |
| 24:0 | Gb4 | 1572.1004 | 1572.09 | 1572.08 | 1572.12 |
| 16:0 | GM2 | 1617.0485 | 1617.07 | 1617.04 | 1617.10 |
| 24:0 | GM2 | 1729.1743 | 1729.17 | 1729.17 | 1729.18 |
| 16:0 | GD3 | 1733.0958 | - | - | - |
| 24:0 | GD3 | 1845.2216 | - | - | - |
| 16:0 | GM1a/b | 1821.1483 | 1821.17 (GM1a) |
1821.18 (GM1b) |
|
| 24:0 | GM1a/b | 1933.2741 | 1933.28 (GM1a) |
1933.26 (GM1b) |
1933.31 (GM1b) |
| 16:0 | GD2 | 1978.2222 | - | 1978.24 | - |
| 24:0 | GD2 | 2090.3480 | - | 2090.36 | - |
| 16:0 | GT3 | 2094.2695 | - | - | - |
| 24:0 | GT3 | 2206.3953 | - | - | - |
| 16:0 | GL7 | 2025.2481 | - | - | - |
| 24:0 | GL7 | 2137.3739 | - | - | 2137.40 |
| 16:0 | GD1a/b | 2182.3219 | 2182.34 (GD1a/b) |
- | 2182.37 (GD1a/c) |
| 24:0 | GD1a/b | 2294.4477 | 2294.46 (GD1a/b) |
- | 2294.49 (GD1a/c) |
Only masses corresponding to N-palmitoyl- (C16:0) or N-lignoceroyl- (C24:0) 2-amino-4-octadecene-1,3-diol (sphingosine) are indicated. Assignments were confirmed by mass spectrometry fragmentation of permethylated GSL by MALDI-TOF/TOF (data not shown). LacCer, lactosylceramide; Gb, globoside.