Shear-Induced beta-Crystallite Unfolding in Condensed Phase Nanodroplets Promotes Fiber Formation in a Biological Adhesive

Alexander Baer, Nils Horbelt, Marlies Nijemeisland, Santiago J. Garcia, Peter Fratzl, Stephan Schmidt, Georg Mayer, Matthew J. Harrington

Research output: Contribution to journalArticleScientificpeer-review

9 Citations (Scopus)

Abstract

Natural materials provide an increasingly important role model for the development and processing of next-generation polymers. The velvet worm Euperipatoides rowelli hunts using a projectile, mechanoresponsive adhesive slime that rapidly and reversibly transitions into stiff glassy polymer fibers following shearing and drying. However, the molecular mechanism underlying this mechanoresponsive behavior is still unclear. Previous work showed the slime to be an emulsion of nanoscale charge-stabilized condensed droplets comprised primarily of large phosphorylated proteins, which under mechanical shear coalesce and self-organize into nano- and microfibrils that can be drawn into macroscopic fibers. Here, we utilize wide-angle X-ray diffraction and vibrational spectroscopy coupled with in situ shear deformation to explore the contribution of protein conformation and mechanical forces to the fiber formation process. Although previously believed to be unstructured, our findings indicate that the main phosphorylated protein component possesses a significant β-crystalline structure in the storage phase and that shear-induced partial unfolding of the protein is a key first step in the rapid self-organization of nanodroplets into fibers. The insights gained here have relevance for sustainable production of advanced polymeric materials.

Original languageEnglish
Pages (from-to)4992-5001
Number of pages10
JournalACS Nano
Volume13
Issue number5
Early online date2019
DOIs
Publication statusPublished - May 2019

Keywords

  • bioinspiration
  • coacervate
  • mechanoresponsive
  • nanodroplets
  • Onychophora
  • self-assembly

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