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Soft Matter|June 30, 2015

Use of extension-deformation-based crystallisation of silk fibres to differentiate their functions in nature

Authors:Keiji Numata1, Hiroyasu Masunaga2, Takaaki Hikima3, Sono Sasaki3,4, Kazuhide Sekiyama5 and Masaki Takata2,3

DOI: 10.1039/c5sm00757g

  • 1. Enzyme Research Team, Biomass Engineering Program Cooperative Division, RIKEN Center for Sustainable Resource Science
  • 2. Japan Synchrotron Radiation Research Institute
  • 3. RIKEN SPring-8 Center
  • 4. Graduate School of Science and Technology, Kyoto Institute of Technology
  • 5. Spiber Inc.


β-Sheet crystals play an important role in determining the stiffness, strength, and optical properties of silk and in the exhibition of silk-type-specific functions. It is important to elucidate the structural changes that occur during the stretching of silk fibres to understand the functions of different types of fibres. Herein, we elucidate the initial crystallisation behaviour of silk molecules during the stretching of three types of silk fibres using synchrotron radiation X-ray analysis. When spider dragline silk was stretched, it underwent crystallisation and the alignment of the β-sheet crystals became disordered initially but was later recovered. On the other hand, silkworm cocoon silk did not exhibit further crystallisation, whereas capture spiral silk was predominantly amorphous. Structural analyses showed that the crystallisation of silks following extension deformation has a critical effect on their mechanical and optical properties. These findings should aid the production of artificial silk fibres and facilitate the development of silk-inspired functional materials.

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Spiber’s research initiatives into novel protein materials have benefited from subsidies provided by the ImPACT Program on behalf of the Japanese Cabinet’s Council for Science, Technology and Innovation.