Biological Science Research Center, Southwest University, Chongqing 400716, China.
Chongqing Key Laboratory of Sericultural Science, Chongqing 400716, China.
Int J Mol Sci. 2019 Jun 21;20(12):3026. doi: 10.3390/ijms20123026.
Silk fiber has become a research focus because of its comprehensive mechanical properties. Metal ions can influence the conformational transition of silk fibroin. Current research is mainly focused on the role of a single ion, rather than the whole metal ion environment. Here, we report the effects of the overall metal ion environment on the secondary structure and mechanical properties of silk fibers after direct injection and feeding of silkworms with EDTA. The metal composition of the hemolymph, silk gland, and silk fiber changed significantly post EDTA treatment. Synchrotron FTIR analysis indicated that the secondary structure of silk fiber after EDTA treatment changed dramatically; particularly, the β-sheets decreased and the β-turns increased. Post EDTA treatment, the silk fiber had significantly decreased strength, Young's modulus, and toughness as compared with the control groups, while the strain exhibited no obvious change. These changes can be attributed to the change in the metal ion environment in the silk fibroin and sericin in the silk gland. Our investigation provides a new theoretical basis for the natural silk spinning process, and our findings could help develop a method to modify the mechanical properties of silk fiber using metal ions.
由于其全面的机械性能，丝纤维已成为研究热点。金属离子可以影响丝素蛋白的构象转变。目前的研究主要集中在单个离子的作用上，而不是整个金属离子环境。在这里，我们报告了在直接注射和喂食 EDTA 后，整体金属离子环境对家蚕丝中丝纤维的二级结构和力学性能的影响。处理后，血淋巴、丝腺和丝纤维的金属成分发生了显著变化。同步辐射 FTIR 分析表明，EDTA 处理后丝纤维的二级结构发生了显著变化；特别是β-折叠减少，β-转角增加。与对照组相比，EDTA 处理后的丝纤维强度、杨氏模量和韧性显著降低，而应变没有明显变化。这些变化可归因于丝腺中丝素蛋白和丝胶中金属离子环境的变化。我们的研究为天然丝纺丝过程提供了新的理论基础，我们的发现可能有助于开发一种使用金属离子来修饰丝纤维力学性能的方法。
