A competitive immunoassay showing the effect of PDI on conversion of Ca-TSP to the EDTA-conformation. Forty-three micrograms/milliliter PDI was incubated with 200 μmol/L GSH for 20 minutes before addition of Ca-TSP in 6 mmol/L EDTA. After 45-minutes incubation at room temperature, TSP was diluted into a solution containing antibody D4.6 and the competitive immunoassay was performed as described in Fig 5. The results are means ± SE of six separate experiments. (○), control TSP; (⋄), TSP with GSH; (□), TSP with PDI + GSH.