The self-organizing properties of squid reflectin protein


Reflectins, a recently identified protein family that is enriched in aromatic and sulphur-containing amino acids, are used by certain cephalopods to manage and manipulate incident light in their environment. These proteins are the predominant constituent of nanoscaled photonic structures that function in static and adaptive colouration, extending visual performance and intra-species communication. Our investigation into recombinantly expressed reflectin has revealed unanticipated self-assembling and behavioural properties, and we demonstrate that reflectin can be easily processed into thin films, photonic grating structures and fibres. Our findings represent a key step in our understanding of the property–function relationships of this unique family of reflective proteins.

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Figure 1: Light-organ platelets and native self-assembly of reflectin 1a protein from an insoluble precursor.
Figure 2: Solution casting of recombinant reflectin thin films.
Figure 3: Reflectin films exhibit shifts in the spectral interference peaks due to film swelling.
Figure 4: Surface diffraction gratings produced from reflectin/ionic liquid thin films.
Figure 5: Reflectin 1a fibres pulled from bulk precipitated protein.


  1. 1

    Vukusic, P. & Sambles, J. R. Photonic structures in biology. Nature 424, 852–855 (2003).

    CAS  Article  Google Scholar 

  2. 2

    Onslow, H. On a periodic structure in many insect scales and the cause of their iridescent colours. Phil. Trans. R. Soc. Lond. B 211, 1–74 (1921).

    Article  Google Scholar 

  3. 3

    Berthier, S. Iridescences: The Physical Colours of Insects (Springer, Berlin, 2006).

    Google Scholar 

  4. 4

    Johnsen, S. Cryptic and conspicuous colouration in the pelagic environment. Proc. R. Soc. Lond. B 269, 243–256 (2002).

    Article  Google Scholar 

  5. 5

    Johnsen, S. & Sosik, H. M. Cryptic colouration and mirror sides as camouflage strategies in near-surface pelagic habitats: Implications for foraging and predator avoidance. Limnol. Oceanogr. 48, 1277–1288 (2003).

    Article  Google Scholar 

  6. 6

    Griffiths, D. J., Winsor, H. & Luong-Van, T. Iridophores in the mantle of giant clams. Aust. Zool. 40, 319–326 (1992).

    Article  Google Scholar 

  7. 7

    Crookes, W. J. et al. Reflectins: The unusual proteins of squid reflective tissues. Science 303, 235–238 (2004).

    CAS  Article  Google Scholar 

  8. 8

    Land, M. F. The physics and biology of animal reflectors. Prog. Biophys. Mol. Biol. 24, 75–106 (1972).

    CAS  Article  Google Scholar 

  9. 9

    Denton, E. J., Land, F. R. S. & Land, M. F. Mechanisms of reflexion in silvery layers of fish and cephalopods. Proc. R. Soc. Lond. A 178, 43–61 (1971).

    CAS  Article  Google Scholar 

  10. 10

    Denton, E. J. On the organization of reflecting surfaces in some marine animals. Phil. Trans. R. Soc. B 258, 285–313 (1970).

    CAS  Article  Google Scholar 

  11. 11

    McFall-Ngai, M. J. & Montgomery, M. K. The anatomy and morphology of the adult bacterial light organ of Euprymna scolopes Berry (Cephalopoda: Sepiolidae). Biol. Bull. 147, 332–339 (1990).

    Article  Google Scholar 

  12. 12

    Montgomery, M. K. & McFall-Ngai, M. J. The muscle-derived lens of a squid bioluminescent organ is biochemically convergent with the ocular lens. Evidence for recruitment of aldehyde dehydrogenase as a predominant structural protein. J. Biol. Chem. 267, 20999–21003 (1992).

    CAS  Google Scholar 

  13. 13

    Weiss, J. L. et al. Methionine-rich repeat proteins: A family of membrane-associated proteins which contain unusual repeat regions. Biochim. Biophys. Acta 1668, 164–174 (2005).

    CAS  Article  Google Scholar 

  14. 14

    Cooper, K. M. & Hanlon, R. T. Correlation of iridescence with changes in iridophore platelet ultrastructure in the squid Lolliguncula brevis. J. Exp. Biol. 121, 451–455 (1986).

    CAS  Google Scholar 

  15. 15

    Cooper, K. M., Hanlon, R. T. & Budelmann, B. U. Physiological colour change in squid iridophores II. Ultrastructural mechanisms in Lolliguncula brevis. Cell Tissue Res. 259, 15–24 (1990).

    CAS  Article  Google Scholar 

  16. 16

    Mäthger, L. M., Collins, T. F. T. & Lima, P. A. The role of muscarinic receptors and intracellular Ca2+ in the spectral reflectivity changes of squid iridophores. J. Exp. Biol. 207, 1759–1769 (2004).

    Article  Google Scholar 

  17. 17

    Fincham, A. G., Moradian-Oldak, J. & Simmer, J. P. The structural biology of developing dental enamel. J. Struct. Biol. 126, 270–299 (1999).

    CAS  Article  Google Scholar 

  18. 18

    Eastoe, J. E. Organic matrix of tooth enamel. Nature 187, 411–412 (1960).

    CAS  Article  Google Scholar 

  19. 19

    Du, C., Falini, G., Fermani, S., Abbot, C. & Moradian-Oldak, J. Supramolecular assembly of amelogenin nanospheres into birefringent microribbons. Science 307, 1450–1454 (2005).

    CAS  Article  Google Scholar 

  20. 20

    Makin, O. S. & Serpell, L. C. Structures for amyloid fibrils. Fed. Eur. Bioch. Soc. J. 272, 5950–5961 (2005).

    CAS  Google Scholar 

  21. 21

    Swatloski, R. P., Spear, R. K., Holbrey, J. D. & Rogers, R. D. Dissolution of cellulose with ionic liquids. J. Am. Chem. Soc. 124, 4974–4975 (2002).

    CAS  Article  Google Scholar 

  22. 22

    Phillips, D. M. et al. Dissolution and regeneration of Bombyx mori silk fibroin using ionic liquids. J. Am. Chem. Soc. 126, 14350–14351 (2004).

    CAS  Article  Google Scholar 

  23. 23

    Sundd, M., Kundu, S. & Jagannadham, M. V. Alcohol-induced conformational transitions in ervatamin C. An alpha-helix to beta-sheet switchover. J. Protein Chem. 19, 169–176 (2000).

    CAS  Article  Google Scholar 

  24. 24

    Kumaran, S. & Roy, R. P. Helix-enhancing propersity of fluoro and alkyl alcohols: Influence of pH, temperature and cosolvent concentration on the helical conformation of peptides. J. Pep. Res. 53, 284–293 (1999).

    CAS  Article  Google Scholar 

  25. 25

    Ober, C. Persistence pays off. Science 296, 859–861 (2002).

    CAS  Article  Google Scholar 

  26. 26

    Qi, M. et al. A three-dimensional optic photonic crystal with designed point defects. Nature 429, 538–542 (2004).

    CAS  Article  Google Scholar 

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This work has been financially supported by DARPA (DSO) and AFOSR. We acknowledge M. McFall-Ngai (NIH AI50611) and E.G. Ruby (NIH RR 12294) for providing us with squid tissue. We thank M. Gupta for assistance with white-light interferometry imaging and D. Morse, R. Hanlon and M. Yustak for helpful discussions.

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Correspondence to Rajesh R. Naik.

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Kramer, R., Crookes-Goodson, W. & Naik, R. The self-organizing properties of squid reflectin protein. Nature Mater 6, 533–538 (2007).

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