Reversible assembly of β-sheet nanocrystals within caddisfly silk

J. Bennett Addison, Warner S. Weber, Qiushi Mou, Nicholas N. Ashton, Russell J. Stewart, Gregory P. Holland, Jeffery Yarger

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

Nuclear magnetic resonance (NMR) and X-ray diffraction (XRD) experiments reveal the structural importance of divalent cation-phosphate complexes in the formation of β-sheet nanocrystals from phosphorylated serine-rich regions within aquatic silk from caddisfly larvae of the species Hesperophyla consimilis. Wide angle XRD data on native caddisfly silk show that the silk contains a significant crystalline component with a repetitive orthorhombic unit cell aligned along the fiber axis with dimensions of 5.9 Å × 23.2 Å × 17.3 Å. These nanocrystalline domains depend on multivalent cations, which can be removed through chelation with ethylenediaminetetraacetic acid (EDTA). A comparison of wide angle X-ray diffraction data before and after EDTA treatment reveals that the integrated peak area of reflections corresponding to the nanocrystalline regions decreases by 15-25% while that of the amorphous background reflections increases by 20%, indicating a partial loss of crystallinity. 31P solid-state NMR data on native caddisfly silk also show that the phosphorylated serine-rich motifs transform from a rigid environment to one that is highly mobile and water-solvated after treatment with EDTA. The removal of divalent cations through exchange and chelation has therefore caused a collapse of the β-sheet structure. However, NMR results show that the rigid phosphorus environment is mostly recovered after the silk is re-treated with calcium. The 31P spin-lattice (T1) relaxation times were measured at 7.6 ± 3.1 and 1 ± 0.5 s for this calcium-recovered sample and the native silk sample, respectively. The shorter 31P T1 relaxation times measured for the native silk sample are attributed to the presence of paramagnetic iron that is stripped away during EDTA chelation treatment and replaced with diamagnetic calcium.

Original languageEnglish (US)
Pages (from-to)1269-1275
Number of pages7
JournalBiomacromolecules
Volume15
Issue number4
DOIs
StatePublished - Apr 14 2014

Fingerprint

Silk
Nanocrystals
Ethylenediaminetetraacetic acid
Edetic Acid
Chelation
Calcium
Positive ions
Divalent Cations
Nuclear magnetic resonance
X ray diffraction
Relaxation time
Serine
Spin-lattice relaxation
Phosphorus
Cations
Ion exchange
Phosphates
Iron
Crystalline materials
Water

ASJC Scopus subject areas

  • Bioengineering
  • Materials Chemistry
  • Polymers and Plastics
  • Biomaterials

Cite this

Addison, J. B., Weber, W. S., Mou, Q., Ashton, N. N., Stewart, R. J., Holland, G. P., & Yarger, J. (2014). Reversible assembly of β-sheet nanocrystals within caddisfly silk. Biomacromolecules, 15(4), 1269-1275. https://doi.org/10.1021/bm401822p

Reversible assembly of β-sheet nanocrystals within caddisfly silk. / Addison, J. Bennett; Weber, Warner S.; Mou, Qiushi; Ashton, Nicholas N.; Stewart, Russell J.; Holland, Gregory P.; Yarger, Jeffery.

In: Biomacromolecules, Vol. 15, No. 4, 14.04.2014, p. 1269-1275.

Research output: Contribution to journalArticle

Addison, JB, Weber, WS, Mou, Q, Ashton, NN, Stewart, RJ, Holland, GP & Yarger, J 2014, 'Reversible assembly of β-sheet nanocrystals within caddisfly silk', Biomacromolecules, vol. 15, no. 4, pp. 1269-1275. https://doi.org/10.1021/bm401822p
Addison JB, Weber WS, Mou Q, Ashton NN, Stewart RJ, Holland GP et al. Reversible assembly of β-sheet nanocrystals within caddisfly silk. Biomacromolecules. 2014 Apr 14;15(4):1269-1275. https://doi.org/10.1021/bm401822p
Addison, J. Bennett ; Weber, Warner S. ; Mou, Qiushi ; Ashton, Nicholas N. ; Stewart, Russell J. ; Holland, Gregory P. ; Yarger, Jeffery. / Reversible assembly of β-sheet nanocrystals within caddisfly silk. In: Biomacromolecules. 2014 ; Vol. 15, No. 4. pp. 1269-1275.
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