Silk Materials Research Unit, National Agriculture and Food Research Organization (NARO) , 1-2 Ohwashi, Tsukuba, Ibaraki 305-8634, Japan.
Department of Future Industry-Oriented Basic Science and Materials, Graduate School of Engineering, Toyota Technological Institute , Tempaku, Nagoya 468-8511, Japan.
Biomacromolecules. 2017 Dec 11;18(12):3892-3903. doi: 10.1021/acs.biomac.7b00920. Epub 2017 Nov 10.
The fibrous silk produced by bees, wasps, ants, or hornets is known to form a four-strand α-helical coiled coil superstructure. We have succeeded in showing the formation of this coiled coil structure not only in natural fibers, but also in artificial films made of regenerated silk of the hornet Vespa simillima xanthoptera using wide- and small-angle X-ray scatterings and polarized Fourier transform infrared spectroscopy. On the basis of time-resolved simultaneous synchrotron X-ray scattering observations for in situ monitoring of the structural changes in regenerated silk material during tensile deformation, we have shown that the application of tensile force under appropriate conditions induces a transition from the coiled α-helices to a cross-β-sheet superstructure. The four-stranded tertiary superstructure remains unchanged during this process. It has also been shown that the amorphous protein chains in the regenerated silk material are transformed into conventional β-sheet arrangements with varying orientation.
由蜜蜂、黄蜂、蚂蚁或胡蜂产生的纤维状丝已知形成四股α-螺旋卷曲螺旋超结构。我们已经成功地表明，不仅在天然纤维中，而且在使用黄胡蜂 Vespa simillima xanthoptera 的再生丝制成的人工薄膜中，都可以形成这种卷曲螺旋结构。通过广角和小角 X 射线散射以及偏振傅里叶变换红外光谱对黄蜂 Vespa simillima xanthoptera 的再生丝材料在拉伸变形过程中的结构变化进行实时同步同步加速器 X 射线散射观察的基础上，我们已经表明，在适当的条件下施加拉伸力会诱导从卷曲的α-螺旋向交叉β-片层超结构的转变。在此过程中，四股三级超结构保持不变。还表明，再生丝材料中的无定形蛋白质链转变成具有不同取向的常规β-片层排列。
