Structural characterization of nanofiber silk produced by embiopterans (webspinners)

J. Bennett Addison, Thomas M. Osborn Popp, Warner S. Weber, Janice S. Edgerly, Gregory P. Holland, Jeffery Yarger

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Embiopterans produce silken galleries and sheets using exceptionally fine silk fibers in which they live and breed. In this study, we use electron microscopy (EM), Fourier-transform infrared (FT-IR) spectroscopy, wide angle X-ray diffraction (WAXD) and solid-state nuclear magnetic resonance (ssNMR) techniques to elucidate the molecular level protein structure of webspinner (embiid) silks. Silks from two species Antipaluria urichi and Aposthonia ceylonica are studied in this work. Electron microscopy images show that the fibers are about 90-100 nm in diameter, making webspinner silks among the finest of all known animal silks. Structural studies reveal that the silk protein core is dominated by β-sheet structures, and that the protein core is coated with a hydrophobic alkane-rich surface coating. FTIR spectra of native embiid silk shows characteristic alkane CH2stretchings near 2800-2900 cm-1, which decrease approximately 50% after washing the silk with 2:1 CHCl3:MeOH. Furthermore, 13C ssNMR data shows a significant CH2resonance that is strongly affected by the presence of water, supporting the idea that the silk fibers are coated with a hydrocarbon-rich layer. Such a layer is likely used to protect the colonies from rain. FTIR data also suggests that embiid silks are dominated by β-sheet secondary structures similar to spider and silkworm silk fibers. NMR data confirms the presence of β-sheet nanostructures dominated by serine-rich repetitive regions. A deconvolution of the serine Cβ NMR resonance reveals that approximately 70% of all seryl residues exist in a β-sheet structure. This is consistent with WAXD results that suggest webspinner silks are 70% crystalline, which is the highest crystalline fraction reported for any animal silks. The work presented here provides a molecular level structural picture of silk fibers produced by webspinners. This journal is

Original languageEnglish (US)
Pages (from-to)41301-41313
Number of pages13
JournalRSC Advances
Volume40
Issue number78
DOIs
StatePublished - 2014

Fingerprint

Silk
Nanofibers
Nuclear magnetic resonance
Fibers
Alkanes
Proteins
Paraffins
Serine
Electron microscopy
Animals
Crystalline materials
X ray diffraction
Nucleic Acid Repetitive Sequences
Deconvolution
Hydrocarbons
Washing
Fourier transform infrared spectroscopy
Rain
Nanostructures

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Chemistry(all)

Cite this

Addison, J. B., Osborn Popp, T. M., Weber, W. S., Edgerly, J. S., Holland, G. P., & Yarger, J. (2014). Structural characterization of nanofiber silk produced by embiopterans (webspinners). RSC Advances, 40(78), 41301-41313. https://doi.org/10.1039/c4ra07567f

Structural characterization of nanofiber silk produced by embiopterans (webspinners). / Addison, J. Bennett; Osborn Popp, Thomas M.; Weber, Warner S.; Edgerly, Janice S.; Holland, Gregory P.; Yarger, Jeffery.

In: RSC Advances, Vol. 40, No. 78, 2014, p. 41301-41313.

Research output: Contribution to journalArticle

Addison, JB, Osborn Popp, TM, Weber, WS, Edgerly, JS, Holland, GP & Yarger, J 2014, 'Structural characterization of nanofiber silk produced by embiopterans (webspinners)', RSC Advances, vol. 40, no. 78, pp. 41301-41313. https://doi.org/10.1039/c4ra07567f
Addison, J. Bennett ; Osborn Popp, Thomas M. ; Weber, Warner S. ; Edgerly, Janice S. ; Holland, Gregory P. ; Yarger, Jeffery. / Structural characterization of nanofiber silk produced by embiopterans (webspinners). In: RSC Advances. 2014 ; Vol. 40, No. 78. pp. 41301-41313.
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