Department of Molecular Spectroscopy, Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
Sci Adv. 2016 Jul 8;2(7):e1501778. doi: 10.1126/sciadv.1501778. eCollection 2016 Jul.
Following an injury, a blood clot must form at the wound site to stop bleeding before skin repair can occur. Blood clots must satisfy a unique set of material requirements; they need to be sufficiently strong to resist pressure from the arterial blood flow but must be highly flexible to support large strains associated with tissue movement around the wound. These combined properties are enabled by a fibrous matrix consisting of the protein fibrin. Fibrin hydrogels can support large macroscopic strains owing to the unfolding transition of α-helical fibril structures to β sheets at the molecular level, among other reasons. Imaging protein secondary structure on the submicrometer length scale, we reveal that another length scale is relevant for fibrin function. We observe that the protein polymorphism in the gel becomes spatially heterogeneous on a micrometer length scale with increasing tensile strain, directly showing load-bearing inhomogeneity and nonaffinity. Supramolecular structural features in the hydrogel observed under strain indicate that a uniform fibrin hydrogel develops a composite-like microstructure in tension, even in the absence of cellular inclusions.
受伤后，必须在伤口处形成血凝块以止血，然后才能进行皮肤修复。血凝块必须满足一组独特的材料要求；它们需要足够坚固以抵抗动脉血流的压力，但又必须高度灵活，以支持与伤口周围组织运动相关的大应变。这些综合特性是由纤维基质组成的，该基质由纤维蛋白组成。纤维蛋白水凝胶可以支持大的宏观应变，这是由于在分子水平上α-螺旋纤维结构展开到β片层，以及其他原因。在亚微米长度尺度上对蛋白质二级结构进行成像，我们发现另一个长度尺度与纤维蛋白功能相关。我们观察到，随着拉伸应变的增加，凝胶中的蛋白质多态性在微米长度尺度上变得空间不均匀，直接显示出承载的非均一性和非亲和力。在应变下观察到的水凝胶中的超分子结构特征表明，即使没有细胞包含物，均匀的纤维蛋白水凝胶在拉伸时也会形成类似复合材料的微观结构。
