TABLE 2.
Mass spectrometrya
| Method | Ion | Proposed structure | Mass (m/z)
|
Difference (ppm) | |
|---|---|---|---|---|---|
| Observed | Theoretical | ||||
| FT-MS | I | (MH2)2+, GDGLHPRL-Thia-S-Thia | 550.23166 | 550.231648 | 0.022 |
| II | (MH2)2+, 34S | 551.22845 | 551.22955 | 2.0 | |
| III | (MH)+, 13C2 | 551.23627 | 551.2350025 | 2.3 | |
| CID-MS/MS of 550.2 | A | (MH2)2+ of ion F | 481.20212 | 481.19883 | 6.8 |
| B | (MH2)2+ of parent ion minus C=O | 536.23520 | 536.23520 | 0.0 | |
| C | (MH)+, PRL-Thia-S-Thia-GD | 792.29387 | 792.29213 | 2.2 | |
| D | (MH)+, PRL-Thia-S-Thia-GDG | 849.31559 | 849.31359 | 2.4 | |
| E | (MH)+, PRL-Thia-S-Thia-GDGL | 962.39975 | 962.39766 | 2.2 | |
| F | (MH)+, HPRL-Thia-S-Thia-GDG | 986.37429 | 986.37250 | 1.8 | |
| IRMPD-MS/MS of 550.2 | G | (MH4)4+ of parent ion | 275.11674 | 275.115824 | 3.3 |
| H | (MH)+, GLH | 308.17152 | 308.17220 | 2.2 | |
| I | (MH2)2+ of parent ion | 550.23035 | 550.231648 | 2.4 | |
| J | (MH)+, RL-Thia-S-Thia-GD | 695.23870 | 695.239367 | 1.0 | |
| K | As ion C | 792.29121 | 792.29213 | 1.2 | |
| L | (MH)+, L-Thia-S-Thia-GDGLH | 846.30172 | 846.302694 | 1.2 | |
| M | As ion E | 962.39676 | 962.39766 | 0.9 | |
a
Proposed peptide structures are in one-letter amino acid code. Thia, cysteine modified to thiazole. Artifacts intrinsic to the machine and visible in other spectra of unrelated molecules constitute the other major peaks in the spectrum and are not tabulated here.