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Science 28 March 2008:
Vol. 319. no. 5871, pp. 1816 - 1819
DOI: 10.1126/science.1154117
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Reports

The Transition from Stiff to Compliant Materials in Squid Beaks

Ali Miserez,1,2,3 Todd Schneberk,2,3 Chengjun Sun,2,3 Frank W. Zok,1* J. Herbert Waite2,3*

The beak of the Humboldt squid Dosidicus gigas represents one of the hardest and stiffest wholly organic materials known. As it is deeply embedded within the soft buccal envelope, the manner in which impact forces are transmitted between beak and envelope is a matter of considerable scientific interest. Here, we show that the hydrated beak exhibits a large stiffness gradient, spanning two orders of magnitude from the tip to the base. This gradient is correlated with a chemical gradient involving mixtures of chitin, water, and His-rich proteins that contain 3,4-dihydroxyphenyl-L-alanine (dopa) and undergo extensive stabilization by histidyl-dopa cross-link formation. These findings may serve as a foundation for identifying design principles for attaching mechanically mismatched materials in engineering and biological applications.

1 Materials Department, University of California, Santa Barbara, CA 93106, USA.
2 Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, CA 93106, USA.
3 Marine Science Institute, University of California, Santa Barbara, CA 93106, USA.

* To whom correspondence should be addressed. E-mail: zok{at}engineering.ucsb.edu (F.W.Z.); waite{at}lifesci.ucsb.edu (J.H.W.)

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Science. ISSN 0036-8075 (print), 1095-9203 (online)