Binding of myosin and fibrin monomers measured by SPR. (A) Myosin (at the indicated concentrations in 10 mM HEPES, 250 mM NaCl, 3 mM CaCl₂, pH 7.4) was applied to fibrin immobilized on the surface of the sensor chip and the relative SPR response (subtracting the response on the control BSA-coated surface) was recorded in a Biacore X system. (B) Fibrin prepared in the presence of 5 mM GPRP (in 10 mM HEPES, 150 mM NaCl, 3 mM CaCl₂, pH 7.4) was applied at the concentrations indicated in the inset to myosin immobilized on the surface of the sensor chip. The relative SPR response was recorded. The primary R_eq values were plotted (inset) and fitted to the equation described in “Materials and methods.”