PDI interaction with αIIbβ3 and β3 by surface plasmon resonance. Full-length αIIbβ3 (25 μg/mL) or recombinant β3 (25 μg/mL) in 10mM acetate buffer, pH 5 or pH 4.5, respectively, was immobilized on the surface of a Biacore CM5 chip. Different concentrations of PDI (21μM [magenta], 7μM [gray], 2.33μM [gold], 0.78μM [turquoise], 0.26μM [pink], 0.09μM [blue], 0.03μM [green], or 0μM [red]) were injected, and the experiments were performed in duplicate with a running buffer of 10mM HEPES, pH 7.5, 150mM NaCl, 0.05% P20, 2mM MnCl2. The dissociation constant, Kd, was calculated based on the Kon and Koff value. (A) PDI binds to αIIbβ3 with a Kd of 0.67μM. (B) PDI binds to β3 with a Kd of 1.2μM.