Transmission and scanning electron microscopy of Fg Philadelphia and normal control clot fibers. Clots were made under the same conditions as in Figure 2 with calcium. (A) Transmission electron micrograph of clot from fibrinogen Philadelphia at low magnification. Inset shows normal clot formed under similar conditions. Magnification bar = 1 μm. (B) Transmission electron micrograph of clot from fibrinogen Philadelphia at higher magnification, showing the details of fiber structure. Magnification bar = 0.5 μm. (C) Scanning electron micrograph of clot from fibrinogen Philadelphia showing the pattern of fiber branching, including fiber ends, with irregular branch points indicated by arrowheads. Magnification bar = 1 μm. (D) Scanning electron micrograph of control clot. Magnification bar = 1 μm.