Table 2.
Modifications and spectral pairs found in data set 2.
| Δm | ΔRt | # of spectral pairs (pp > 0.98) | Modification type | Theoretical mass | Unimod AC # | ||
| Mean | ± 3Sigma | Mean | ± 3Sigma | ||||
| 53.9177 | ± 0.0180 | -15.3 | ± 222.3 | 5236 | Cation:Fe(II) | 53.9193 | None |
| 15.9942 | ± 0.0090 | -685.3 | ± 762.3 | 4613 | Oxidation | 15.9949 | 35 |
| 0.9959 | ± 0.0395 | 47.4 | ± 254.9 | 305 | Amidation/Deamidation | 0.9840 | 2/7 |
| 18.01 | N/A | N/A | N/A | N/A | Water-loss/Glu → pyro-Glu* | 18.0106 | 23/27 |
| 57.02 | N/A | N/A | N/A | N/A | Carbamidomethylation* | 57.0215 | 4 |
*Those modifications are found from the 1-D Δm histogram and manually validated by 2-D <Δm, ΔRt> histogram, but the data points for them are too few to effectively estimate their Δm and ΔRt distributions.