The mass-to-length ratio of fibrin fibers is dependent on the initial concentration of prothrombin.

Mass-to-length ratios were calculated by scanning the fibrin clots from 400 to 800 nm, as described in “Materials and methods.” Values were then normalized, such that 100% of plasma levels of prothrombin were set equal to 1. Note that the y-axis does not begin at 0. Data shown are representative of measurements on 9 experiments.