Table 1.
Positive ion mode
| Possible assignments for lipid molecular ion peaks | Calculated mass | Ar SIMS | MALDI | NP-LDI | Measured mass Ar SIMS | ∆ppm |
|---|---|---|---|---|---|---|
| Galactosylceramide (32:1) C38H73NO8K [M + K]+ | 710.4973 | + | 710.495 | −3.23 | ||
| Phosphatidic acid (34:1) C37H71O8PK [M + K]+ | 713.4523 | + | 713.4537 | 1.96 | ||
| Cerebroside C40H76NO9 [M + H] | 714.5519 | + | 714.5553 | 4.75 | ||
| Phosphatidic acid C39H73O8PNa [M + Na]+ | 723.494 | + | 723.4953 | 1.79 | ||
| Phosphatidylcholine (32:0) C39H73O8PK [M + K]+ | 734.5699 | + | + | 734.5677 | −2.99 | |
| Phosphatidic acid C39H73O8PK [M + K]+ | 739.4679 | + | 739.4683 | 0.54 | ||
| Phosphatidic acid (36:1) C39H75O8PK [M + K]+ | 741.4836 | + | 741.4826 | −1.34 | ||
| Sphingolipid (18:0) C42H81NO8NA [M + Na]+ | 750.5859 | + | + | 750.5789 | −9.32 | |
| Phosphatidylcholine fragment | 751.52 | + | + | 751.5181 | −2.52 | |
| Sphingomyelin (18:1/36:1) C41H83N2O6PNA [M + Na]+ | 753.5886 | + | 753.5873 | −1.72 | ||
| Phosphatidylcholine (32:0) C40H80NO8PNa [M + Na]+ | 756.5519 | + | + | 756.5541 | 2.9 | |
| Phosphatidylcholine (34:2) C42H81NO8 [M + H]+ | 758.5699 | + | 758.5634 | −8.56 | ||
| Phosphatidylcholine (34:1) C42H83NO8P [M + H]+ | 760.5856 | + | + | 760.5868 | 1.57 | |
| Phosphatidylcholine (34:0) C42H85NO8P [M + H]+ | 762.6012 | + | 762.5996 | −2.09 | ||
| Phosphatidylinositol (30:1) C39H76O12P [M + H]+ | 767.5074 | + | 767.5073 | −0.13 | ||
| Sphingomyelin (18:1/36:1)C41H83N2O6PK [M + K]+ | 769.5625 | + | 769.5614 | −1.42 | ||
| Phosphatidylcholine (32:0) C40H80NO8PK [M + K]+ | 772.5258 | + | + | 772.5251 | −0.9 | |
| Sphingomyelin (18:1/20:0) C43H87N2O6PNa [M + Na]+ | 781.6199 | + | + | 781.6157 | −5.37 | |
| Phosphatidylcholine (34:1) C42H82NO8PNa [M + Na]+ | 782.5675 | + | 782.5678 | 0.38 | ||
| Phosphatidylcholine C42H84NO8PNa (34:0) [M + Na]+ | 784.5831 | + | 784.5833 | 0.25 | ||
| Phosphatidylcholine (36:1) C44H87NO8P [M + H]+ | 788.6169 | + | 788.6164 | −0.63 | ||
| Phosphatidylcholine (34:1) C42H82NO8PK [M + K]+ | 798.5414 | + | + | 798.5426 | 1.5 | |
| Phosphatidylcholine (34:0) C42H84NO8PK [M + K]+ | 800.5571 | + | 800.554 | −3.87 | ||
| Sphingomyelin (18:1/22:0)C45H91N2O6PNa [M + Na]+ | 809.6512 | + | + | 809.6438 | −9.13 | |
| Phosphatidylcholine (36:1) C44H86NO8PNa [M + Na]+ | 810.5988 | + | 810.5941 | −5.79 | ||
| Galactosylceramide (d18:1/23:0) C47H91NO8Na [M + Na]+ | 820.6642 | + | + | 820.6583 | −7.18 | |
| Phosphatidylcholine (40:4) C48H89NO7P [M + H]+ | 822.6376 | + | + | 822.6394 | 2.18 | |
| Galactosylceramide (d18:0/22:0) C46H91NO8K [M + Na]+ | 824.6381 | + | + | 824.6315 | −8 | |
| Phosphatidylcholine (36:1) C44H86NO8PK [M + K]+ | 826.5727 | + | + | 826.579 | 7.62 | |
| Sphingolipid C48H91NO8Na [M + Na]+ | 832.6642 | + | + | 832.658 | −7.44 | |
| Sphingomyelin (18:1/24:1) C47H93N2O6PNa [M + Na]+ | 835.6668 | + | + | 835.6619 | −5.86 | |
| Phosphatidylcholine (42:1) C47H92NO7PNa [M + Na]+ | 836.6508 | + | 836.654 | 3.82 | ||
| Sphingomyelin (18:1/24:0)C47H95N2O6PNa [M + Na]+ | 837.6825 | + | + | 837.6744 | −9.66 | |
| Phosphatidylethanolamine (42:3) C47H88NO8PNa [M + Na] | 848.6144 | + | + | + | 848.619 | 5.42 |
| Cerebroside C48H93NO9Na [M + Na]+ | 850.6747 | + | + | 850.668 | −7.87 | |
| Sphingomyelin (18:1/24:1) C47H93N2O6PK [M + K]+ | 851.6408 | + | + | 851.6442 | 3.99 | |
| Phosphatidylcholine (41:4) C49H91NO8P [M + H]+ | 852.6482 | + | 852.6492 | 1.17 | ||
| Ceramide (40:0) C46H93NO11P [M + H]+ | 866.6486 | + | + | 866.6437 | −5.65 |
Lipid assignment for mass peaks obtained by NP-LDI, MALDI, and high-energy Ar cluster SIMS in the mouse brain in positive ion mode (Table 1) and peak assignments for NP-LDI and Ar GCIB SIMS spectra in negative ion mode (Table 2) [26, 40, 48, 66]. The peaks that appear in each MSI technique are weighted by (+). In Ar GCIB SIMS, the peaks enhanced after TFA modification of the sample are bold. Galactosylceramide (A/B) corresponds to long chain base (A)/ amide-linked fatty acid (B)