Plasma AOPP Concentration Assay

Plasma AOPP concentrations were assessed as chloramine-T equivalents as described previously [18 (link)]. Briefly, 200 μL of each plasma sample (diluted 5 times in PBS) was placed into a 96-well plate, and then 10 μL of 1.16 M potassium iodide (Sigma, St. Louis, MO, USA) and 20 μL of acetic acid (Sigma, St. Louis, MO, USA) were added. Two hundred microlitres of chloramine-T (Sigma) at different concentrations (0, 20, 40, 80, and 100 μM) were used for calibration. The absorbance at 340 nm was read immediately by a Spectra Max M5 spectrophotometer (Molecular Devices, San Francisco, CA, USA). The AOPP concentrations are expressed as μmol/L of chloramine-T equivalents.