Density differences of WT and fibrinogen variant fibrin clots involved in extended knob-hole interactions. Fibrin clots were allowed to form for 1 hour and imaged using laser scanning confocal microscopy (A: WT, B: γDEK, C: γD297N, D: γE323Q, E: γK356Q). Fiber count per 200 µm was quantified (F). Variant γDEK (B, F) was denser than WT (A, F). Mean ± SD, N = 4 (WT), N = 3 (all variants). ***P < .001 for variants compared with WT.