Silkworm silk has attracted considerable attention in recent years due to its excellent mechanical properties, biocompatibility, and promising applications in biomedical sector. However, a clear understanding of the molecular structure and the relationship between the excellent mechanical properties and the silk protein sequences are still lacking. This study carries out a thorough comparative structural analysis of silk fibers of four silkworm species (Bombyx mori, Antheraea pernyi, Samia cynthia ricini, and Antheraea assamensis). A combination of characterization techniques including scanning electron microscopy, mechanical test, synchrotron X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), and NMR spectroscopy was applied to investigate the morphologies, mechanical properties, amino acid compositions, nanoscale organizations, and molecular structures of various silkworm silks. Furthermore, the structure–property relationship is discussed by correlating the molecular structural features of silks with their mechanical properties. The results show that a high content of β-sheet structures and a high crystallinity would result in a high Young’s modulus for silkworm silk fibers. Additionally, a low content of β-sheet structures would result in a high extensibility.

中文翻译：

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各种蚕丝的结构比较：对结构-性能关系的一种认识

蚕丝由于其优异的机械性能，生物相容性以及在生物医学领域的广阔前景，近年来引起了相当大的关注。但是，仍然缺乏对分子结构以及优异的机械性能与丝蛋白序列之间关系的清楚理解。本研究进行的4种蚕丝纤维的透彻比较结构分析（家蚕，柞蚕，萨米亚蓖麻蚕，和柞assamensis）。结合了包括扫描电子显微镜，机械测试，同步加速器X射线衍射，傅立叶变换红外光谱（FTIR）和NMR光谱在内的表征技术来研究形态，力学性能，氨基酸组成，纳米级组织和分子结构各种蚕丝。此外，通过将蚕丝的分子结构特征与其机械性能相关联，讨论了结构与性质的关系。结果表明，高含量的β-折叠结构和高结晶度将导致蚕丝纤维的高杨氏模量。另外，低含量的β-折叠结构将导致高延伸性。