Pseudoelastic behaviour of a natural material is achieved via reversible changes in protein backbone conformation.
The egg capsules of marine prosobranch gastropods, commonly know as whelks, function as a protective encapsulant for whelk embryos in wave-swept marine environments. The proteinaceous sheets comprising the wall of whelk egg capsules (WEC) exhibit long-range reversible extensibility with a hysteresis of up to 50 per cent, previously suggested to result from reversible changes in the structure of the constituent protein building blocks. Here, we further investigate the structural changes of the WEC biopolymer at various hierarchical levels using several different time-resolved in situ approaches. We find strong evidence in these biological polymers for a strain-induced reversible transition from an ordered conformational phase to a largely disordered one that leads to the characteristic reversible hysteretic behaviour, which is reminiscent of the pseudoelastic behaviour in some metallic alloys. On the basis of these results, we generate a simple numerical model incorporating a worm-like chain equation to explain the phase transition behaviour of the WEC at the molecular level.
Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Wissenschaftspark Golm, 14424 Potsdam, Germany. matt.harrington@mpikg.mpg.de
Matthew J
MJ
Harrington
S Scott
SS
Wasko
Admir
A
Masic
F Dieter
FD
Fischer
Himadri S
HS
Gupta
Peter
P
Fratzl
D060105:Animal Shells / Q000737:chemistry*; D000818:Animals; D001704:Biopolymers / Q000737:chemistry*; D004548:Elasticity; D004625:Embryo, Nonmammalian / Q000033:anatomy & histology / Q000737:chemistry; D008954:Models, Biological; D011487:Protein Conformation; D012908:Snails / Q000033:anatomy & histology / Q000737:chemistry*; D013059:Spectrum Analysis, Raman; D014961:X-Ray Diffraction
D001704:Biopolymers