Evolutionary Origin of Silk Material Hierarchy

&lt;div style="direction: ltr;"&gt;Silk fibers, produced by arthropods and silkworms, are one of nature's brilliant materials designs, having ordered multi-scale hierarchical structures assembled via specific molecular interactions. This unique design creates a material with extraordinary mechanical properties, combining high strength, extensibility, and toughness. Although the spinning process of silk fibers has been extensively studied, the biological aspect of this process is still poorly understood. In general, the natural spinning process is accompanied by silk protein structural transition from its soluble random-coil state into a solidified beta-sheet rich conformation under the effect of shear forces, elongational flow, chelation by metal ions and changes in pH. However, it involves more complex and dynamic events such as phase separation, supramolecular organizations, structural-phase transitions, and changes in flow regime.<br/>Our investigation revealed the key steps and events in the complex formation of the silk fibers initiated inside the silk gland. The results showed the co-existence of multiple macromolecular structures, morphologies, and phase transition events.&lt;/div&gt;