Figure 4. Oxidation of DTT (400 μmol/l) in the presence of H₂O₂ (50 μmol/l) plus Fe²⁺ (concentrations expressed in μmol/l) in PB (100 mmol/l) (4A) and/or MOPS (100 mmol/l) (4B) buffers. The rate of thiol oxidations was determined by measuring the amount sulfhydryl groups at different times. Data show means ± SEM values from 3 to 4 independent experiments performed in duplicate. SEM cannot be seen when it is smaller than symbol.