Controlling the properties of silk-based materials by metal ions

Native silk fibers, produced by arthropods and silkworms, exhibit exceptional mechanical properties, including high strength and toughness. Such properties are defined not only by the sequence of silk fibroin protein but also by spinning mechanisms that are still poorly understood. In general, the spinning process accompanied by the conformational transition of silk fibroin protein, from random coil to β-sheet-rich secondary structure. Such transitions induced by the changes in the chemical environment and physical forces acting during the spinning: shear forces, elongational flow, chelation by metal ions and changes in pH. This research is focused on unraveling the role of metal ions in silk fibroin fibers formation. Metal ions, in particular, are known to induce the protein conformational change. However, their contribution to the definition of the final properties of the silk fiber is still unknown.