Binding of VWF mutants to collagens type I and III. A fixed concentration of (A) 0.25 μg/mL and (B) 0.125 μg/mL of rVWF obtained from transiently transfected COS-7 cells, or various concentrations of (C) 0 to 2 μg/mL and (D) 0 to 1 μg/mL of rVWF obtained from stable transfected BHK cells was added to wells coated with collagen I (A,C) or collagen III (B,D). Bound VWF was probed with horseradish peroxidase–labeled polyclonal anti-VWF antibodies and detected via peroxidase hydrolysis of Tetramethylbenzidine (A,C) and o-Phenylenediamine dihydrochloride for (B,D). Symbols represent wt-rVWF (▪), rVWF-δ A3 (□), p.L1696R-VWF (○), and p.P1824H-rVWF (△). (A,B) Binding of homozygous and cotransfected (1:1) mutants are represented as % of wt-VWF binding. Data represent means ± SD of 3 independent experiments. *P values < .05 as compared with wt values. OD, optical density; NP, normal pooled plasma.