Tang Ming, Li Tong, Gandhi Neha S, Burrage Kevin, Gu YuanTong
School of Chemistry Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, Australia.
Centre for Composite Material, University of Delaware, Newark, DE, 19711, USA.
Biomech Model Mechanobiol. 2017 Jun;16(3):1023-1033. doi: 10.1007/s10237-016-0870-6. Epub 2017 Jan 7.
Collagen is an abundant structural biopolymer in mammal vertebrates, providing structural support as well as mechanical integrity for connective tissues such as bone, ligament, and tendon. The mechanical behaviours of these tissues are determined by the nanomechanics of their structures at different hierarchies and the role of collagen structures in the extracellular matrix. Some studies revealed that there is significant microstructural difference in the longitudinal direction of the collagen fibril, which challenges the conventional rod-like assumption prevalently adopted in the existing studies. Motivated by this discrepancy, in this study, we investigated the longitudinal heterogeneous nanomechanical properties of type I collagen molecule to probe the origin of the longitudinal heterogeneity of the collagen fibril at the molecular level. A full length type I collagen molecule structure was built based on the experimentally calibrated nanostructure. Then, a suitable strain rate was determined for stretching the three intact 'gap' regions and three intact 'overlap' regions of the collagen molecule. Further, the nanomechanical properties of the six collagen molecule segments were characterized by performing steered molecular dynamics simulations, using the obtained suitable strain rate in modelling. The results indicate that this computational model can be used to capture the mechanical behaviour of the collagen molecule under physiological stress conditions. Moreover, the 'gap' regions show a lower stiffness and undergo a slightly lager strain in the unwinding process, compared to the 'overlap' regions of the collagen molecule. This investigation provides insights into the origin of the longitudinal heterogeneity of collagen fibrils at the molecular level and suggests that it is of significant importance to consider the longitudinal heterogeneous mechanical properties of the collagen molecule in the development of coarse-grained models of collagen-related tissues.
胶原蛋白是哺乳动物脊椎动物中一种丰富的结构生物聚合物，为骨骼、韧带和肌腱等结缔组织提供结构支撑以及机械完整性。这些组织的力学行为由其不同层次结构的纳米力学以及细胞外基质中胶原蛋白结构的作用决定。一些研究表明，胶原纤维的纵向存在显著的微观结构差异，这对现有研究中普遍采用的传统棒状假设提出了挑战。受这种差异的启发，在本研究中，我们研究了I型胶原蛋白分子的纵向非均匀纳米力学性质，以在分子水平上探究胶原纤维纵向非均匀性的起源。基于实验校准的纳米结构构建了全长I型胶原蛋白分子结构。然后，确定了拉伸胶原蛋白分子的三个完整“间隙”区域和三个完整“重叠”区域的合适应变速率。此外，通过进行引导分子动力学模拟，使用获得的合适应变速率进行建模，表征了六个胶原蛋白分子片段的纳米力学性质。结果表明，该计算模型可用于捕捉生理应力条件下胶原蛋白分子的力学行为。此外，与胶原蛋白分子的“重叠”区域相比，“间隙”区域在展开过程中表现出较低的刚度，并经历稍大的应变。这项研究为胶原纤维纵向非均匀性的起源提供了分子水平的见解，并表明在开发与胶原蛋白相关组织的粗粒度模型时考虑胶原蛋白分子的纵向非均匀力学性质具有重要意义。
