Letter | Published:

Liquid crystallinity of natural silk secretions

Abstract

NATURAL silk exhibits a strength and stiffness similar to, and a toughness up to ten times greater than, that of artificial high-performance fibres1–5. These exceptional tensile properties, the optical birefringence of some silk secretions6–9 and the molecular order exhibited by some synthetic polypeptides in solution10 all suggest that natural silk secretions might form liquid-crystalline phases. We have now used polarized-light microscopy to study the secretions from major ampullae of spiders (Nephila clavipes) and from silk glands of silkworms (Bombyx mori). As the concentration is increased by evaporation of water, nematic liquid-crystalline microstructures develop. We deduce that natural silk secretions become liquid crystalline after leaving the gland but before solidifying into a fibre, thus promoting global molecular alignment in the fibre. Our hand-drawn fibres from droplets of secretion, as well as sheared thin films, show a banded microstructure which is indicative of a periodic variation in the direction of molecular alignment11. Both B. mori and N. clavipes, on the other hand, have apparently developed processing routes that ensure uniform molecular alignment: the threads and draglines, respectively, of these species do not show banded microstructures.

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References

  1. 1

    Denny, M. J. exp. Biol. 65, 483–506 (1976).

  2. 2

    Calvert, P. Nature 340, 266 (1989).

  3. 3

    Vollrath, F. & Edmonds, D. T. Nature 340, 305–307 (1989).

  4. 4

    Gosline, J. M., Denny, M. W. & DeMont, M. E. Nature 309, 551–552 (1984).

  5. 5

    Prevorsek, D. C. in Polymer Liquid Crystals (eds Ciferri, A., Krigbaum, W. R. & Meyer, R. B.) Ch, 12 (Academic, New York, 1982).

  6. 6

    Lucas, F. & Rudall, K. M. in Comprehensive Biochemistry (eds Florkin, M. & Stotz, E. H.) Vol. 26B, Ch. 7 (Elsevier, Amsterdam, 1968).

  7. 7

    Magoshi, J., Magoshi, Y. & Nakamura, S. J. appl.Polym. Sci.: appl. Polym. Symp. 41, 187–204 (1985).

  8. 8

    Magoshi, J., Magoshi, Y. & Nakamura, S. Polym. Comm. 26, 60–61 (1985).

  9. 9

    Li, G. & Yu, T. Makromol. Chem. Rapid Comm. 10, 387–389 (1989).

  10. 10

    Elliot, A. & Ambrose, E. J. Discuss. Faraday Soc. 9, 246–251 (1950).

  11. 11

    Viney, C., Donald, A. M. & Windle, A. H. Polymer 26, 870–878 (1985).

  12. 12

    Tsuda, M. & Suzuki, Y. Proc. natn. Acad. Sci. U.S.A. 80, 7442–7446 (1983).

  13. 13

    Tamura, T. & Sakate, S. Insect Biochem. 18, 169–175 (1988).

  14. 14

    Lombardi, S. J. & Kaplan, D. L. Polym. Preprints 31(1), 195–196 (1990).

  15. 15

    Billmeyer, F. W. Textbook of Polymer Science Ch. 18 (Wiley, New York, 1984).

  16. 16

    Lizuka, E. J. appl. Polym. Sci.: appl. Polym. Symp. 41, 173–185 (1985).

  17. 17

    Dobb, M. G. & McIntyre, J. E. Adv. Polym. Sci. 60/61, 61–98 (1984).

  18. 18

    Demus, D. & Richter, L. Textures of Liquid Crystals (Verlag Chemie, Weinheim, 1978).

  19. 19

    Lucas, F. Discovery 25, 20–26 (1964).

  20. 20

    de Gennes, P. G. The Physics of Liquid Crystals Ch. 4 (Oxford University Press, 1979).

  21. 21

    Gray, G. W. & Goodby, J. W. Smectic Liquid Crystals: Textures and Structures 58 (Leonard Hill, Glasgow, 1984)

  22. 22

    Zheng, S., Li, G., Yao, W. & Yu, T. Appl. Spectrosc. 43, 1269–1272 (1989).

  23. 23

    Wilson, R. S. Q. J. microsc. Sci. 104, 557–571 (1962).

  24. 24

    Donald, A. M., Viney, C. & Windle, A. H. Polymer 24, 155–159 (1983).

  25. 25

    Marsano, E., Carpaneto, L. & Ciferri, A. Molec. Cryst. liq. Cryst. 158B, 267–278 (1988).

  26. 26

    Fried, F. & Sixou, P. Molec. Cryst. liq. Cryst. 158B, 163–184 (1988)

  27. 27

    Ernst, B. & Navard, P. Macromolecules 22, 1419–1422 (1989).

  28. 28

    Dobb, M. G., Johnson, D. J. & Saville, B. P. J. Polym. Sci.: Polym. Symp. 58, 237–251 (1977).

  29. 29

    Roche, E. J., Allen, S. R., Fincher, C. R. & Paulson, C. Molec. Cryst. liq. Cryst. 153, 547–552 (1987).

  30. 30

    Cokendolpher, J. C. & Brown, J. D. Ent. News 96, 114–118 (1985).

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