Affinity measurements of SZ34 with full-length VWF and various VWF fragments using ELISA The native or denatured VWF fragments and pVWF at various concentrations were first incubated in solution with the antibody (SZ34 or SZ29) at constant concentration until equilibrium was reached, respectively. The denatured VWF fragments and pVWF were obtained by denaturization treatment with guanidine-HCl as above. The concentration of free antibody was then determined by an ELISA. The equilibrium dissociation constants (Kd) of antigen/antibody complexes in solution were obtained according to the equation [33] :