Figure 7: Models for Single Fiber Fibrinolysis.

A) Protofibril recoil model: Protofibrils, which are under tension in fibers, spring backwards as they are cleaved (in green), similar to how the strands of a tensed rope spring backward as they are cut. The springing backwards causes the fiber to appear as if it’s being pulled apart. B) Molecular stretching model: Protofibrils are under tension in fibers, and as protofibrils are cut, that tension is spread out across fewer and fewer protofibrils. Eventually the force on each protofibril is enough to unfold the remaining fibrin molecules (in blue) making up the protofibril, causing the fiber to slide apart. Here we show cut fibrin molecules leaving the fiber, rather than the protofibrils recoiling, to distinguish the mechanisms, but protofibril recoil could also occur concurrently with the molecular stretching model shown in panel B.