title: The transition from stiff to compliant materials in squid beaks.
abstract: 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.
authors: Materials Department, University of California, Santa Barbara, CA 93106, USA.
authors: Ali
authors: A
authors: Miserez
authors: Todd
authors: T
authors: Schneberk
authors: Chengjun
authors: C
authors: Sun
authors: Frank W
authors: FW
authors: Zok
authors: J Herbert
authors: JH
authors: Waite
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001502:Beak / Q000033:anatomy & histology / Q000737:chemistry*; D001696:Biomechanical Phenomena; D002686:Chitin / Q000032:analysis* / Q000737:chemistry; D003187:Compliance; D049832:Decapodiformes / Q000033:anatomy & histology / Q000737:chemistry*; D004295:Dihydroxyphenylalanine / Q000032:analysis / Q000737:chemistry*; D004298:Dopamine / Q000031:analogs & derivatives / Q000032:analysis; D005612:Freeze Drying; D005944:Glucosamine / Q000032:analysis; D006244:Hardness; D006639:Histidine / Q000032:analysis / Q000737:chemistry; D010858:Pigmentation; D011506:Proteins / Q000032:analysis* / Q000737:chemistry; D014867:Water / Q000032:analysis*
chemical_list: D000596:Amino Acids; D011506:Proteins; D014867:Water; D002686:Chitin; C006374:N-acetyldopamine; D006639:Histidine; D004295:Dihydroxyphenylalanine; D005944:Glucosamine; D004298:Dopamine