Huot Alexandrine, Lefèvre Thierry, Rioux-Dubé Jean-François, Paquet-Mercier François, Nault Anne-Philipe, Auger Michèle, Pézolet Michel
Department of Chemistry, Centre de recherche sur les matériaux avancés, Centre québécois sur les matériaux fonctionnels, Regroupement québécois de recherche sur la fonction, la structure et l'ingénierie des protéines, Université Laval, Québec, QC, Canada G1V 0A6.
Appl Spectrosc. 2015 Jun;69(6):689-98. doi: 10.1366/14-07776. Epub 2015 May 1.
To better understand the effect of mechanical stress during the spinning of silk, the protein orientation and conformation of Bombyx mori regenerated silk fibroin (RSF) films have been studied as a function of deformation in a static mode or in real time by tensile-Raman experiments and polarization modulation infrared linear dichroism (PM-IRLD), respectively. The data show that either for step-by-step or continuous stretching, elongation induces the progressive formation of β-sheets that align along the drawing axis, in particular above a draw ratio of ~2. The formation of β-sheets begins before their alignment during a continuous drawing. Unordered chains were, however, never found to be oriented, which explains the very low level of orientation of the amorphous phase of the natural fiber. Stress-perturbed unordered chains readily convert into β-sheets, the strain-induced transformation following a two-state process. The final level of orientation and β-sheet content are lower than those found in the native fiber, indicating that various parameters have to be optimized in order to implement a spinning process as efficient as the natural one. Finally, during the stress relaxation period in a step-by-step drawing, there is essentially no change of the content and orientation of the β-sheets, suggesting that only unordered structures tend to reorganize.
为了更好地理解蚕丝纺丝过程中机械应力的影响，通过拉伸拉曼实验和偏振调制红外线性二向色性（PM - IRLD）分别以静态模式或实时方式研究了家蚕再生丝素蛋白（RSF）膜的蛋白质取向和构象随变形的变化。数据表明，无论是逐步拉伸还是连续拉伸，伸长都会诱导沿拉伸轴排列的β折叠片层逐渐形成，特别是在拉伸比约为2以上时。在连续拉伸过程中，β折叠片层的形成先于其排列。然而，从未发现无序链有取向，这解释了天然纤维非晶相的取向水平非常低的原因。应力扰动的无序链很容易转化为β折叠片层，应变诱导的转变遵循双态过程。最终的取向水平和β折叠片层含量低于天然纤维中的水平，这表明为了实现与天然纺丝过程一样高效的纺丝过程，必须优化各种参数。最后，在逐步拉伸的应力松弛阶段，β折叠片层的含量和取向基本没有变化，这表明只有无序结构倾向于重新组织。
