TABLE 2.
Parent-daughter ions monitored to determine isotopic enrichments for glutamine and citrulline1
| M0, m/z |
M+n, m/z |
||||
| Parent | Daughter | Parent | Daughter | Enrichment determined | |
| Glutamine | 380 | 842 | 381 | 85 | Amino N |
| 380 | 3633 | 381 | 363 | Amido N | |
| 380 | 1704 | 381 | 170 | Whole molecule M+1 | |
| 380 | 170 | 381–3855 | 170 | Carbon skeleton (M+1−M+5) | |
| Citrulline | 409 | 702 | 410 | 71 | Amino N |
| 409 | 70 | 411 | 72 | 5,5 2H2 | |
| 409 | 3923 | 410 | 392 | Ureido N | |
| 409 | 392 | 410 | 393 | Amino N + δ N | |
| 409 | 170 | 410 | 170 | Whole molecule M+1 | |
| 409 | 170 | 410–4145 | 170 | Carbon skeleton (M+1−M+5) | |
1
M0, base ion; M+n, isotopologue of interest.
2
Fragments m/z 84 and 70 contain 2-N and 2,3,4 and 5-C of glutamine and citrulline, respectively.
3
Fragments m/z 363 and 392 contain the whole dansylated molecule after the loss of ammonia from the amido or ureido group of glutamine and citrulline, respectively.
4
The fragment m/z 170 represents the dimethyl amino naphthalene fragment of the dansylated molecule.
5
The reporter ion m/z 170 was used to determine the isotope distribution of glutamine and citrulline.