Abstract
Summary: Poly(L‐lysine)s having an N^ε^‐substituted tetrapeptide, Lys‐Gly‐Tyr‐Gly, were synthesized by the coupling of the protected tetrapeptide active ester, Boc‐Lys(Z)‐Gly‐Tyr(Bzl)‐Gly (4‐hydroxyphenyl)dimethylsulfonium methylsulfate and N^ε^‐group of the poly(L‐lysine) side chain. The N^ε^‐substituted tetrapeptide functions as the substrate of tyrosinase and is responsible for the enzyme‐mediated interpolymer cross‐linking. The degree of N^ε^‐substitution (DS) was mostly controlled by changing the stoichiometry between the N^ε^‐amino groups of the parent poly(L‐lysine) and the protected tetrapeptide active ester. Two kinds of samples having DS values of 8.6 and 18 mol‐% were prepared. The resulting cationic N^ε^‐(Lys‐Gly‐Tyr‐Gly)‐poly(L‐lysine) (abbreviated as PLL(GYGK)) was spun into hybrid fibers with the anionic polysaccharide gellan via a polyionic complexation reaction at the interface between aqueous solutions of the two polymers. The mechanical strengths of the PLL(GYGK)‐gellan hybrid fibers were superior to those of the original poly(L‐lysine)‐gellan fibers. The mechanical strength of the hybrid fibers further increased upon the tyrosinase‐mediated cross‐linking reaction of the PLL(GYGK). This result indicates that the covalent cross‐bridge formation between the N^ε^‐substituted peptides significantly contributed to reinforcement of the hybrid fibers. The present study affords a new methodology for reinforcement inspired by a biological process.
Reinforcement mechanism of the PLL(GYGK)‐gellan hybrid fiber.
imageReinforcement mechanism of the PLL(GYGK)‐gellan hybrid fiber.