Interaction of fibrinogen and immobilized myosin. (A) Time course of fibrinogen (Fg) binding to and dissociation from myosin. ¹²⁵I-labeled fibrinogen (250 nM) was applied in a 100-μL volume to myosin immobilized on microtiter plates. For the follow-up of the binding (•), at the indicated times the fibrinogen solution was removed and after washing the bound radioactivity was measured. For monitoring the dissociation (○), after a binding phase of 10 minutes the fibrinogen solution was discarded and 100 μL 10 mM HEPES 150 mM NaCl, pH 7.4, buffer was applied. At the indicated times the solution was removed and the residual bound radioactivity was measured (symbols). The lines show the modeled time course of the process using the rate constants gained with nonlinear fit to the experimental points. (B) Equilibrium-binding data. Mixtures of ¹²⁵I-fibrinogen (•) or Eu-fibrinogen (○) and varying amounts of nonlabeled fibrinogen were incubated in myosin-coated microtiter plates for 2 hours. After washing the myosin-bound labeled fibrinogen was measured as described in “Materials and methods.” Results are presented as mean measured bound fibrinogen (symbols), its SD (bars), and the best fit (solid line), which is obtained for a single class of binding sites as described in “Materials and methods.”