Improving strength of silks by adding a peptide

February 26, 2018

A promising substitute for petroleum-derived high-strength materials

Silk from silkworms and spiders is a light and tough material which shows biodegradability and low cytotoxicity. It can also be molded into various shapes such as films, sponges, and gels. These features have enabled practical use of the silk materials not only for conventional textile applications but also for medical applications.

In particular, spider silk has attracted great attention as a material with high toughness, which results from good extensibility and high strength comparable to steel. However, the mechanism for natural silks to form the crystal structure during their spinning process has not been comprehensively clarified until now; this has made it difficult to control the crystal structure of the artificial silk during processing for excellent physical properties.

A structure with reactive functional groups at both ends of the polymer chain is called a telechelic structure. A collaborative RIKEN CSRS–JASRI research team synthesized a polyalanine (a polypeptide consisting of the amino acid alanine) with a telechelic structure using chemoenzymatic polymerization. This telechelic polyalanine was added to spider-derived silk to produce a composite silk film. The resulting film showed improved tensile strength and toughness. The telechelic polyalanine was found to exhibit a nanofiber-like crystal form, having effectively created a β-sheet crystal structure in the silk film.

Since all the components in the composite material obtained by this method are bio-derived substances, this silk materials can be used as a substitute for conventional high-strength materials derived from petroleum, which is expected to contribute to the protection of the global environment.

Original article
Scientific Reports doi:10.1038/s41598-018-21970-1
K. Tsuchiya, T. Ishii, H. Masunaga, K. Numata,
"Spider dragline silk composite films doped with linear and telechelic polyalanine: Effect of polyalanine on the structure and mechanical properties".
Keiji Numata; Team Leader
Kosuke Tsuchiya; Senior Research Scientist
Enzyme Research Team