Collet Jean-Philippe, Shuman Henry, Ledger Robert E, Lee Seungtaek, Weisel John W
Department of Cell and Developmental Biology and Institute for Environmental Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
Proc Natl Acad Sci U S A. 2005 Jun 28;102(26):9133-7. doi: 10.1073/pnas.0504120102. Epub 2005 Jun 20.
A blood clot needs to have the right degree of stiffness and plasticity to stem the flow of blood and yet be digestable by lytic enzymes so as not to form a thrombus, causing heart attacks, strokes, or pulmonary emboli, but the origin of these mechanical properties is unknown. Clots are made up of a three-dimensional network of fibrin fibers stabilized through ligation with a transglutaminase, factor XIIIa. We developed methods to measure the elastic moduli of individual fibrin fibers in fibrin clots with or without ligation, using optical tweezers for trapping beads attached to the fibers that functioned as handles to flex or stretch a fiber. Here, we report direct measurements of the microscopic mechanical properties of such a polymer. Fibers were much stiffer for stretching than for flexion, as expected from their diameter and length. Elastic moduli for individual fibers in plasma clots were 1.7 +/- 1.3 and 14.5 +/- 3.5 MPa for unligated and ligated fibers, respectively. Similar values were obtained by other independent methods, including analysis of measurements of fluctuations in bead force as a result of Brownian motion. These results provide a basis for understanding the origin of clot elasticity.
血凝块需要具备适当程度的硬度和可塑性，以阻止血液流动，同时又能被溶解酶消化，从而避免形成血栓，引发心脏病发作、中风或肺栓塞，但这些机械性能的起源尚不清楚。血凝块由纤维蛋白纤维的三维网络组成，通过与转谷氨酰胺酶XIIIa因子连接而稳定。我们开发了方法，使用光镊捕获附着在纤维上的珠子，这些珠子充当手柄来弯曲或拉伸纤维，从而测量有或没有连接的纤维蛋白凝块中单个纤维蛋白纤维的弹性模量。在此，我们报告了对这种聚合物微观机械性能的直接测量。正如根据其直径和长度所预期的那样，纤维拉伸时比弯曲时更硬。血浆凝块中未连接和连接的单个纤维的弹性模量分别为1.7±1.3和14.5±3.5兆帕。通过其他独立方法也获得了类似的值，包括分析由于布朗运动导致的珠子力波动的测量结果。这些结果为理解凝块弹性的起源提供了基础。
