Table 1.
Assignment of major peptide ions observed in the MALDI-ToF mass spectrum of the EndoLysC protein digest Mass values are monoisotopic for [M+H]+ ions. For the N-terminal peptide, the calculated mass takes into account a modification by methionine excision (- 131.04 Da) and acylation (+ 42.01 Da), the theoretical mass of the unmodified peptide being 1568.80 Da.
| Measured mass (Da) | Calculated mass (Da) | Stretch location | Sequence ions identified by PSD analysis |
| 1051.48 | 1051.51 | 17–24 | |
| 1076.49 | 1076.53 | 282–290 | |
| 1201.67 | 1201.64 | 273–281 | |
| 1479.76 | 1479.77 | 2–12 | y2-y4, b2-b8, a5-a8, H and Y immonium ions |
| 1538.92 | 1538.94 | 305–317 | |
| 1559.78 | 1559.80 | 13–24 | |
| 1732.96 | 1732.98 | 291–304 | |
| 1792.97 | 1792.98 | 224–240 | |
| 1845.99 | 1845.98 | 318–334 | y2-y4, b2-b5, a4-a7, R,V and Y immonium ions |