TABLE 2.
Daughter ions produced during MS/MS analysis of a peptide at m/z 585.73+ containing the intersubunit isopeptide bond between Spy0128 (Lys161) and Cpa (Thr723)
| Observed m/za | Charge state | Calculated m/zb | Δ(obs−calc)c | Proposed structure |
|---|---|---|---|---|
| 147.11 | +1 | 147.11 | 0 | K |
| 199.10 | +1 | 199.11 | −0.01 | EP (a2 ion) |
| 211.15 | +1 | 211.14 | 0.01 | PId |
| 294.19 | +1 | 294.18 | 0.01 | FK |
| 326.17 | +1 | 326.17 | 0 | EPV |
| 339.22 | +1 | 339.20 | 0.02 | PIQ |
| 422.22 | +1 | 422.24 | −0.02 | QFK |
| 425.23 | +1 | 425.24 | −0.01 | EPVV |
| 486.26 | +1 | 486.27 | −0.01 | PIQF |
| 535.32 | +1 | 535.32 | 0 | IQFK |
| 632.40 | +1 | 632.38 | 0.02 | PIQFK |
| 731.49 | +1 | 731.45 | 0.04 | VPIQFK |
a
Monoisoptic masses of the observed ions.
b
Calculated ions. Monoisotopic masses were calculated using the Fragment Ion Calculator (http://db.systemsbiology.net:8080/proteomicsToolkit/FragIonServlet.html).
c
Difference between observed ion mass and calculated ion mass.
d
Internal ions are shown in italics.