Table 3.
Matrix-assisted laser desorption/ionization post-source decay (MALDI PSD) and electrospray ionization collision-induced dissociation (ESI CID) tandem mass spectrometry fragment ions observed for [Asp3] MC-RA, MC-RA, [Asp3] MC-RAba and MC-RAba.
| Fragment Assignment a | [Asp3] MC-RA (10) | MC-RA (11) | [Asp3] MC-RAba (12) | MC-Raba (13) |
|---|---|---|---|---|
| M + H b,c | 939 | 953 | 953 | 967 |
| M − H2O + H b,c | 921 | 935 | 935 | 949 |
| M − COOH + H c | 894 | 908 | 908 | 922 |
| M − Z + H c | 868 | 882 | 868 | 882 |
| M − CH2NHCN2H3 + H c | 867 | 881 | 881 | 895 |
| M − Glu + H c | 810 | 824 | 824 | 838 |
| M − (Me)Asp + H c | 824 | 824 | 838 | 838 |
| M − Adda sidechain + H c | 787 | 819 | 819 | 833 |
| Mdha-Ala-Arg-(Me)Asp-Z + NH4 c | 514 | 528 | 528 | 542 |
| Mdha-Ala-Arg-(Me)Asp-Z − H2O + NH4 c | 496 | 510 | 510 | 524 |
| Mdha-Ala-Arg-(Me)Asp-Z + H c | 497 | 511 | 511 | 525 |
| Mdha-Ala-Arg-(Me)Asp − CH2NHCN2H3 + H c | 354 | 368 | 354 | 368 |
| Mdha-Ala-Arg-(Me)Asp + H c | 426 | 440 | 426 | 440 |
| Mdha-Ala-Arg + H b,c | 311 | 311 | 311 | 311 |
| Mdha-Ala + H b | 155 | 155 | - | 155 |
| Arg-(Me)Asp-Z + H c | 343 | 357 | 357 | |
| Glu-Mdha-Ala-Arg − COOH + H c | 395 | 395 | 395 | 395 |
| Glu-Mdha-Ala-Arg − CH2NHCN2H3 + H c | 368 | 368 | 368 | 368 |
| Glu-Mdha-Ala-Arg + H c | 440 | 440 | 440 | 440 |
| Glu-Mdha + H b | 213 | - | 213 | |
| Adda′-Glu-Mdha + H b,c | 375 | 375 | 375 | 375 |
| Adda′ + H b | 163 | 163 | - | 163 |
a Z = Position four amino acid (for 10–11 = 71 Da and 12–13 = 85 Da); Adda′ = Adda minus NH2 and the sidechain (C9H11O); CH2NHCN2H3 is a fragment of the arginine sidechain; b Fragments observed in the MALDI PSD spectra; c Fragments observed in the ESI CID spectra. Note: MALDI PSD analysis could not be conducted on 12.