Table 2.
Modified peptides identified by LC-MS after tryptic digestion of oxidized ubiquitin and β-casein samples (500 μM). The mass to charge ratio (m/z) of modified peptides, with charge state in parenthesis, and the mass error (ppm) are indicated. The last three columns specify the experimental conditions where the modified peptides were identified, and the number of replicates showing the modified peptides (indicated with a + symbol). Ctrl: control; PB: phosphate buffer; D60: 60 mg mL−1 dextran (Mw 35,000–45,000).
| m/z modified peptide | Mass error (ppm) | Sequence and site of modification | Ctrl | PB | D60 |
|---|---|---|---|---|---|
| Ubiquitin | |||||
| 549.2773 (+2) | 0.2116 | 55TLSDY(+16)NIQK63 | + | +++ | +++ |
| β-casein | |||||
| 1333.9675 (+4) | −0.1177 | 49IHPFAQTQSLVYPFPGPIPNSLPQNIPPLTQTPVVVPPFLQPEVM(+16)GVSK97 | ++ | +++ | +++ |
| 343.8443 (+3) | −0.7956 | 106HKEM(+16)PFPK113 | +++ | +++ | |
| 1279.0549 (+5) | −0.1468 | 114YPVEPFTESQSLTLTDVENLHLPLPLLQSW(+16)MHQPHQPLPPTVM(+16)FPPQSVLSLSQSK169 | + | +++ | +++ |
| 1282.2539 (+5) | −0.1672 | 114YPVEPFTESQSLTLTDVENLHLPLPLLQSW(+32)M(+16)HQPHQPLPPTVMFPPQSVLSLSQSK169 | +++ | +++ | |
| 423.7271 (+2) | −1.2702 | 177AVPY(+16)PQR183 | +++ | +++ | |
| 734.7257 (+3) | −0.2506 | 184DM(+16)PIQAFLLYQEPVLGPVR202 | + | +++ | +++ |