Figure 4. Nitroxide-mediated inhibition of protein oxidation by the MPO-H₂O₂-Cl⁻ system.

Modification of surface-adsorbed perlecan (from 10 nM solution) and HSA (from 70 nM solution) by the MPO-H₂O₂-Cl⁻ system (10 nM MPO, 100 mM Cl⁻ and 10 μM H₂O₂) in the presence of nitroxides (10 μM) was quantified after 30 min reaction by ELISA by measuring loss of perlecan recognition by monoclonal antibody CSI-076 recognising perlecan domain I (black bars) and gain in recognition by monoclonal antibody 2D10G9 recognising HOCl-modified protein (perlecan, white bars; HSA, grey bars). Results are means ± S.E.M., n = 3 independent experiments. Modification of HSA was also quantified by amino acid analysis (Supplementary Figure S6).