Department of Molecular Chemistry and Materials Science, Faculty of Chemistry, Weizmann Institute of Science, 7610001, Rehovot, Israel.
Department of Chemical Research Support, Faculty of Chemistry, Weizmann Institute of Science, 7610001, Rehovot, Israel.
Nat Commun. 2024 Aug 6;15(1):6671. doi: 10.1038/s41467-024-50879-9.
Silk fibers' unique mechanical properties have made them desirable materials, yet their formation mechanism remains poorly understood. While ions are known to support silk fiber production, their exact role has thus far eluded discovery. Here, we use cryo-electron microscopy coupled with elemental analysis to elucidate the changes in the composition and spatial localization of metal ions during silk evolution inside the silk gland. During the initial protein secretion and storage stages, ions are homogeneously dispersed in the silk gland. Once the fibers are spun, the ions delocalize from the fibroin core to the sericin-coating layer, a process accompanied by protein chain alignment and increased feedstock viscosity. This change makes the protein more shear-sensitive and initiates the liquid-to-solid transition. Selective metal ion doping modifies silk fibers' mechanical performance. These findings enhance our understanding of the silk fiber formation mechanism, laying the foundations for developing new concepts in biomaterial design.
蚕丝纤维独特的机械性能使其成为理想的材料，但它们的形成机制仍知之甚少。虽然已知离子支持丝纤维的生产，但它们的确切作用迄今仍未被发现。在这里，我们使用冷冻电子显微镜结合元素分析来阐明金属离子在丝腺内蚕丝演变过程中组成和空间定位的变化。在最初的蛋白质分泌和储存阶段，离子均匀地分散在丝腺中。一旦纤维被纺出，离子就从丝素核心游离到丝胶涂层，这一过程伴随着蛋白质链的排列和原料粘度的增加。这种变化使蛋白质对剪切更敏感，并引发液体到固体的转变。选择性的金属离子掺杂可以改变丝纤维的机械性能。这些发现增强了我们对丝纤维形成机制的理解，为开发生物材料设计的新概念奠定了基础。
