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Understanding the Mechanical Properties and Structure Transition of Antheraea pernyi Silk Fiber Induced by Its Contraction
Biomacromolecules ( IF 5.5 ) Pub Date : 2018-02-05 00:00:00 , DOI: 10.1021/acs.biomac.7b01691 Yu Wang 1 , Jianchuan Wen 1 , Bo Peng 2 , Bingwen Hu 2 , Xin Chen 1 , Zhengzhong Shao 1
Biomacromolecules ( IF 5.5 ) Pub Date : 2018-02-05 00:00:00 , DOI: 10.1021/acs.biomac.7b01691 Yu Wang 1 , Jianchuan Wen 1 , Bo Peng 2 , Bingwen Hu 2 , Xin Chen 1 , Zhengzhong Shao 1
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Like most major ampullate silks of spider, the length of Antheraea pernyi silkworm silk can shrink to a certain degree when the fiber is in contact with water. However, what happens in terms of molecule chain level and how it correlates to the mechanical properties of the silk during its contraction is not yet fully understood. Here, we investigate the water-induced mechanical property changes as well as the structure transition of two kinds of A. pernyi silk fiber, which are forcibly reeled from two different individuals (silkworm a and silkworm b; the silk fiber from either one represents the lower and upper limit of the distribution of mechanical properties, respectively). The tensile test results present that most of the mechanical parameters except the post-yield modulus and breaking strain for both silk fibers have the same variation trend before and after their water contraction. Synchrotron FTIR and Raman spectra show that the native filament from silkworm a contains more α-helix structures than that in silkworm b filament, and these α-helices are partially converted to β-sheet structures after the contraction of the fibers, while the order of both β-sheet and α-helix slightly increase. On the other side, the content and orientation of both secondary structural components in silkworm b fiber keep unchanged, no matter if it is native or contracted. 13C CP/MAS NMR results further indicate that the α-helix/random coil to β-sheet conformational transition that occurred in the silk of silkworm a corresponds the Ala residues. Based upon these results, the detailed structure transition models of both as-reeled A. pernyi silk fibers during water contraction are proposed finally to interpret their properties transformation.
中文翻译：
了解per蚕丝纤维收缩引起的力学性能和结构转变
像大多数蜘蛛的主要壶腹丝一样，per蚕ther丝的长度在纤维与水接触时可以收缩到一定程度。然而，关于分子链水平的变化及其在蚕丝收缩过程中与蚕丝的机械性能之间的关系尚不完全清楚。在这里，我们研究了水诱导的机械性能变化以及两种A. pernyi丝纤维的结构转变，这两种纤维是从两个不同的个体（蚕a和蚕b）强行卷取而来的。; 任一种的丝纤维分别代表机械性能分布的下限和上限。拉伸试验结果表明，除了丝收缩前后，两种丝纤维的屈服后模量和断裂应变以外的大多数机械参数都具有相同的变化趋势。同步加速器FTIR和拉曼光谱表明，蚕a的天然丝比蚕b的丝具有更多的α螺旋结构，这些α螺旋在纤维收缩后部分转化为β片层结构，顺序为β-折叠和α-螺旋都略有增加。另一方面，蚕b的两个次要结构成分的含量和方向光纤保持不变，无论是本地的还是合同的。13 C CP / MAS NMR结果进一步表明，在蚕a的蚕丝中发生的从α螺旋/无规卷曲到β折叠的构象转变对应于Ala残基。基于这些结果，最后提出了两种ree蚕丝纤维在水收缩过程中的详细结构转变模型，以解释其性能转变。
更新日期：2018-02-05
中文翻译：
了解per蚕丝纤维收缩引起的力学性能和结构转变
像大多数蜘蛛的主要壶腹丝一样，per蚕ther丝的长度在纤维与水接触时可以收缩到一定程度。然而，关于分子链水平的变化及其在蚕丝收缩过程中与蚕丝的机械性能之间的关系尚不完全清楚。在这里，我们研究了水诱导的机械性能变化以及两种A. pernyi丝纤维的结构转变，这两种纤维是从两个不同的个体（蚕a和蚕b）强行卷取而来的。; 任一种的丝纤维分别代表机械性能分布的下限和上限。拉伸试验结果表明，除了丝收缩前后，两种丝纤维的屈服后模量和断裂应变以外的大多数机械参数都具有相同的变化趋势。同步加速器FTIR和拉曼光谱表明，蚕a的天然丝比蚕b的丝具有更多的α螺旋结构，这些α螺旋在纤维收缩后部分转化为β片层结构，顺序为β-折叠和α-螺旋都略有增加。另一方面，蚕b的两个次要结构成分的含量和方向光纤保持不变，无论是本地的还是合同的。13 C CP / MAS NMR结果进一步表明，在蚕a的蚕丝中发生的从α螺旋/无规卷曲到β折叠的构象转变对应于Ala残基。基于这些结果，最后提出了两种ree蚕丝纤维在水收缩过程中的详细结构转变模型，以解释其性能转变。
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