Infiltration of chitin by protein coacervates defines the squid beak mechanical gradient

Phase transitions as intermediate steps in the formation of molecularly engineered protein fibers

“…In some cases, coacervates are formed by a single polyelectrolyte. These events have been referred to as self- 12,13 , elementary 14 , one-component 15 , or simple 16 coacervation.…”

“…In studies based on mussel and sandcastle worm adhesives, it was found that the coacervation step preassembles the protein constituents of the adhesives, which in combination with the low surface energy and cohesiveness results in a very efficient function 19–22 . The role of coacervates in the formation of biological materials such as squid beak has also been described, in which again the preassembled state of proteins and low surface energy of the coacervate leads to efficient infiltration of a scaffold and subsequently to the formation of mechanically excellent structures 12,13 . Also for tropoelastin assembly has it been shown that a coacervate step leads to structural assembly 4,23 .…”

Recipe for squid beak

“…Open questions include the exact structures of these molecules, the types of interactions they undergo, the kinetics of their interactions, the ways that they condense into solid structures, and the types of chemistry that are involved in the curing of the resulting materials 4,5 . Tan et al now approach these questions with their study of the beak of the jumbo squid Dosidicus gigas 6 .…”

“…Because the proteins entrapped in the squid beak are difficult to fully identify by direct isolation, Tan et al 6 instead studied the protein-secreting cells, the beccublasts ( Fig. 1).…”

“…The work by Tan et al 6 is elegant in its combination of techniques, although many details remain to be elucidated: for example, how the different types of protein BIOMATERIALS Recipe for squid beak the molecular basis of biomaterial assembly and function can provide inspiration for new materials science designs. new research explains the squid beak's transition from soft to hard through the identification of two new families of proteins with unusual physical properties.…”