Yoshioka Taiyo, Tashiro Kohji, Ohta Noboru
Department of Future Industry-oriented Basic Science and Materials, Graduate School of Engineering, Toyota Technological Institute , Tempaku, Nagoya 468-8511, Japan.
Japan Synchrotron Radiation Research Institute , 1-1 Koto, Mikazuki-cho, Sayo-gun, Hyogo 679-5198, Japan.
Biomacromolecules. 2016 Apr 11;17(4):1437-48. doi: 10.1021/acs.biomac.6b00043. Epub 2016 Mar 22.
Enhancing the molecular orientation of the regenerated silk fibroin (RF) up to a level comparable to the native silk is highly challenging. Our novel and promising strategy for the poststretching process is (1) creating at first an α-helix-HFIP complex with a hexagonal packing as an intermediate state and then (2) stretching it at a high temperature to induce the helix-to-sheet structural phase transition. Here we show for the first time the significantly high stretching efficiency of the proposed technique compared with the conventional wet-stretching techniques and the successful achievement of higher crystalline orientation and higher Young's modulus compared even with the native silk. The detailed structural analysis based on the time-resolved simultaneous measurement of stress-strain curve, synchrotron X-ray scatterings, and FTIR has revealed the structural transition mechanism from the hexagonally packed α-helix-HFIP complex to the highly oriented β-sheet crystalline state as well as the critical level of crystal orientation needed for the helix-to-sheet transition.
将再生丝素蛋白（RF）的分子取向提高到与天然丝相当的水平极具挑战性。我们针对后拉伸过程提出的新颖且有前景的策略是：首先创建一种具有六方堆积的α-螺旋-HFIP复合物作为中间状态，然后在高温下对其进行拉伸，以诱导螺旋-片状结构相变。在此，我们首次展示了与传统湿拉伸技术相比，所提出技术具有显著更高的拉伸效率，并且甚至与天然丝相比，成功实现了更高的结晶取向和更高的杨氏模量。基于应力-应变曲线、同步加速器X射线散射和傅里叶变换红外光谱的时间分辨同步测量进行的详细结构分析，揭示了从六方堆积的α-螺旋-HFIP复合物到高度取向的β-片层结晶态的结构转变机制，以及螺旋-片状转变所需的晶体取向临界水平。
