Morphometrical, mechanical, and biochemical properties during FN fibril assembly. (A) The number of FN molecules, (B) stretched length, (C) relaxed length, (D) thickness, (E) extensibility, given by the stretched-relaxed length ratio, (F) substrate force, (G) actin filament velocity, (H) the fraction of attached molecular clutches, and (I) the FA length are shown as a function of time for a 16-h simulation of an assembling FN fibril. The fraction of attached molecular clutches is given by total clutches bound to the FN Type III-10 domain, divided by the total number of clutches available for binding (two per exterior FN molecule). Measurements are for the simulation presented in Fig. 2.