Table 4.
Peptides with additional oxidative modifications of tyrosine residues identified by LC-MS/MS after incubation of rabbit hemopexin with t-BuOOH and HOCl
These modified peptides were unambiguously identified by MASCOT with the tyrosine modifications shown, based on mass difference, but the particular amino acid was not validated by MS/MS fragmentation. HPX, ROS ratios were 1:10 HOCl (FNPVSGEVPPGYdi-ClPLDVR, DYClFLSCPGR, and DYdi-ClFLSCPGR), and 1:1, 1:2.5, and 1:10 t-BuOOH (FNPVSGEVPPGYt-BuPLDVR). Mascot scores for FNPVSGEVPPGYt-BuPLDVR from 1:1 and 1:2.5 t-BuOOH searches were 39.2 and 32.8, respectively. Superscripts indicate residues modified by t-butylation (t-Bu), mono- (Cl), or di-chlorination (di-Cl).
| HPX species | NCBI gi number | Peptide sequence | COM site | Charge (+) | Mascot ions score |
|---|---|---|---|---|---|
| Rabbit | 130500366 | 211FNPVSGEVPPGYdi-ClPLDVR227 | 222 | 2 | 63.3 |
| Rabbit | 130500366 | 211FNPVSGEVPPGYtBuPLDVR227 | 222 | 2 | 39.3 |
| Rabbit | 130500366 | 228DYClFLSCPGR236 | 229 | 2 | 30.6 |
| Rabbit | 130500366 | 228DYdi-ClFLSCPGR236 | 229 | 2 | 31.8 |