Figure 1.

Structural properties of fibrin gels. (A) Atomic force microscopy shows a homogeneous network of thick and straight fibers (5 × 5 μm area). (B) Fibrin fibers have a hierarchical architecture: fibers (top) are bundles of protofibrils (middle), which consist of two half-staggered strands of fibrin monomers with αC-extensions (αC-e) protruding from the surface (bottom). (C–E) Confocal microscopy demonstrates that fibrin gels are homogeneous over a large range of protein concentrations. Scale bars, 10 μm. (F) (Top panel) The mesh size of fibrin gels estimated from confocal images decreases as the square-root of protein concentration (symbols), consistent with the expectation for homogeneous networks of fibers of constant diameter (solid line). (Bottom panel) Concentration dependence of the number of protofibrils per fiber N, measured by turbidimetry.