Pulling out a peptide chain from β-sheet crystallite： Propagation of instability of H-bonds under shear force

• Published in: Acta mechanica Sinica 2015-06, Vol.31 (3), p.416-424
• Main Authors: Xu, Changjian, Li, Dechang, Cheng, Yuan, Liu, Ming, Zhang, Yongwei, Ji, Baohua
• Format: Article
• Language: English
• Subjects: Classical and Continuum Physics; Computational Intelligence; Engineering; Engineering Fluid Dynamics; Research Paper; Theoretical and Applied Mechanics; 不稳定; 传播; 分子动力学模拟; 剪切力; 微晶板材; 机械性能; 氢键; 肽链
• ISSN: 0567-7718; 1614-3116
• DOI: 10.1007/s10409-015-0404-y

Anti-parallel β-sheet crystallite as the main component of silk fibroin has attracted much attention due to its superior mechanical properties. In this study, we examine the processes of pulling a peptide chain from β-sheet crystallite using steered molecular dynamics simulations to investigate the rupture behavior of the crystallite. We show that the failure of β-sheet crystallite was accompanied by a propagation of instability of hydrogen-bonds （H-bonds） in the crystallite. In addition, we find that there is an optimum size of the crystallite at which the H-bonds can work cooperatively to achieve the highest shear strength. In addition, we find that the stiffness of loading device and the loading rates have significant effects on the rupture behavior of β-sheet crystallite. The stiff loading device facilitates the rebinding of the Hbond network in the stick-slip motion between the chains, while the soft one suppresses it. Moreover, the rupture force of β-sheet crystallites decreases with loading rate. Particularly, when the loading rate decreases to a critical value, the rupture force of the β-sheet crystallite becomes independent of the loading rates. This study provides atomistic details of rupture behaviors of β-sheet crystallite, and, therefore, sheds valuable light on the underlying mechanism of the superior mechanical properties of silk fibroin.