Protofibril packing dynamics of WT and extended knob-hole variant fibrin fibers. The UV-Vis spectrum (500 nm < λ < 780 nm) of fibrin clots was scanned for WT and all variants. The wavelength dependent turbidity of the fibrin clots was used to determine fiber diameter and quantitate intrafibrillar protofibril packing arrangements. The fiber diameter (A) corresponding to all 4 variants were similar to WT, and the number of protofibrils per fiber (B) was reduced for all variants, resulting in an increase in the distance between protofibrils (C). Mean ± SD, N = 3.