Multiscale Mechanics of Fibrin Polymer: Gel Stretching with Protein Unfolding and Loss of Water

1. Multiscale Mechanics of Fibrin Polymer: Gel Stretching with Protein Unfolding and Loss of Water A.E.X. Brown, R. Litvinov, P. Purohit, J. Weisel. And Dennis E. Discher, NSEC DMR08-32802 Vascular injury initiates biochemical reactions that cause the blood protein, fibrin, to polymerize and help to stop bleeding and support wound healing. Fibrin can also be a scaffold for thrombi that lead to cardiovascular diseases. To maintain homeostasis, fibrin clots must be stiff yet plastic so that the network can be permeated and eventually decomposed. We investigated the behavior of fibrin clots at the molecular scale, single-fiber scale, and macroscopic scale. At relatively low strains, fibers aligned and formed bundles, and at higher strains, protein unfolding occurred. An integrated model provides a molecular basis for fibrin elasticity and extensibility. Unfolded domains could be promising targets for modification in applications such as tissue engineering and cell biophysics, where stiffness is known to be important , and for designs of tougher fibrin sealants used in surgeries. Controlling unfolding could also lead to new strategies for breaking thrombi, perhaps by stabilizing the coiled coil, rendering clots more brittle for thrombectomy, or by destabilizing the coiled coil, making clots softer and less occlusive. Structural transitions observable at multiple scales may also be involved in the mechanics of other protein assemblies. Brown, et al Science 2009