Spider dragline silk has unique characteristics of strength and extensibility, including supercontraction. When we use it as a biomaterial or material for textiles, it is important to suppress the effect of water on the fiber by as much as possible in order to maintain dimensional stability. In order to produce spider silk with a highly hydrophobic character, based on the sequence of ADF-3 silk, we produced recombinant silk (RSSP(VLI)) where all QQ sequences were replaced by VL, while single Q was replaced by I. The artificial RSSP(VLI) fiber was prepared using formic acid as the spinning solvent and methanol as the coagulant solvent. The dimensional stability and water absorption experiments of the fiber were performed for eight kinds of silk fiber. RSSP(VLI) fiber showed high dimensional stability, which is suitable for textiles. A remarkable decrease in the motion of the fiber in water was made evident by 13C solid-state NMR. This study using 13C solid-state NMR is the first trial to put spider silk to practical use and provide information regarding the molecular design of new recombinant spider silk materials with high dimensional stability in water, allowing recombinant spider silk proteins to be used in next-generation biomaterials and materials for textiles.
Keywords: 13C NMR spectroscopy; dimensional stability; recombinant spider silk protein.