Table 3.
Computed spectral similarity scores between experimental and predicted ESI-MS/MS spectra at three energy levels (10, 20, and 40 eV). The results show higher similarities, and thus an improvement when using a rule-based approach (CFM-ID 3.0) over a combinatorial one (CFM-ID 2.0) for the prediction of lipid ESI-MS/MS spectra. The spectral similarities of the LipidBlast-generated consensus spectra further illustrate this trend. When available, the same LipidBlast-generated consensus spectrum was used for comparisons at each energy level. N/A corresponds to cases where (1) the adduct type was not covered by CFM-ID 2.0 at all, or (2) the adduct type was not covered by LipidBlast for the chemical class to which the test compound belongs.
| Compound | Adduct | Energy (eV) | CFM-ID 3.0 (Score) | CFM-ID 2.0 (Score) | LipidBlast (Score) |
|---|---|---|---|---|---|
| PA(16:0/18:1(9Z)) | [M−H]− | 10 | 1.00 | 0.36 | 0.00 |
| PS(16:0/18:1(9Z)) | [M−H]− | 10 | 1.00 | 0.31 | 0.00 |
| CL(18:0/18:0/18:0/18:0) | [M−2H](2H) | 10 | 0.98 | N/A | 0.00 |
| DG(18:0/20:4/0:0) | [M+Na]+ | 10 | 0.92 | 0.00 | N/A |
| PA(16:0/18:1(9Z)) | [M−H]− | 20 | 0.55 | 0.02 | 0.00 |
| PS(16:0/18:1(9Z)) | [M−H]− | 20 | 0.98 | 0.03 | 0.00 |
| CL(18:0/18:0/18:0/18:0) | [M−2H](2H) | 20 | 0.97 | N/A | 0.12 |
| DG(18:0/20:4/0:0) | [M+Na]+ | 20 | 0.93 | 0.00 | N/A |
| PA(16:0/18:1(9Z)) | [M−H]− | 40 | 0.96 | 0.03 | 0.90 |
| PS(16:0/18:1(9Z)) | [M−H]− | 40 | 0.92 | 0.10 | 0.91 |
| CL(18:0/18:0/18:0/18:0) | [M−2H](2H) | 40 | 0.91 | N/A | 0.89 |
| DG(18:0/20:4/0:0) | [M+Na]+ | 40 | 0.18 | 0.00 | N/A |
| PC(16:0/16:0) | [M+H]+ | 40 | 0.88 | 0.07 | 0.13 |
| TG(18:1/18:1/18:2) | [M+NH4]+ | 40 | 0.78 | 0.01 | 0.84 |