Sensorgram of surface plasmon resonance-based analysis of interleukin-8 binding to bPF4. Biotinylated PF4 was immobilized on SA5 streptavidin-coated dextran chip and perfused with equilibrium buffer at 20 μL/min. At time A (start of association phase), equilibrium buffer containing the indicated concentrations (2, 3, 4, 5, and 6 μM; each in triplicate) of IL-8 was perfused over the chip. At point B (start of dissociation phase), perfusion with unsupplemented equilibrium buffer is resumed. From an average k_diss/k_assoc derived from a k_s plot, an equilibrium dissociation constant (K_d) for the interaction of PF4 with IL-8 of 42 nM was calculated.