Iron-clad fibers: a metal-based biological strategy for hard flexible coatings.
The extensible byssal threads of marine mussels are shielded from abrasion in wave-swept habitats by an outer cuticle that is largely proteinaceous and approximately fivefold harder than the thread core. Threads from several species exhibit granular cuticles containing a protein that is rich in the catecholic amino acid 3,4-dihydroxyphenylalanine (dopa) as well as inorganic ions, notably Fe3+. Granular cuticles exhibit a remarkable combination of high hardness and high extensibility. We explored byssus cuticle chemistry by means of in situ resonance Raman spectroscopy and demonstrated that the cuticle is a polymeric scaffold stabilized by catecholato-iron chelate complexes having an unusual clustered distribution. Consistent with byssal cuticle chemistry and mechanics, we present a model in which dense cross-linking in the granules provides hardness, whereas the less cross-linked matrix provides extensibility.
Harrington
Matthew J
MJ
Department of Biomaterials, Max Planck Institute for Colloids and Interfaces, Potsdam 14424, Germany. Matt.Harrington@mpikg.mpg.de
Masic
Admir
A
Holten-Andersen
Niels
N
Waite
J Herbert
JH
Fratzl
Peter
P
D000825:Animal Structures / Q000737:chemistry; D000818:Animals; D001696:Biomechanical Phenomena; D055598:Chemical Phenomena; D004295:Dihydroxyphenylalanine / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D006244:Hardness; D007501:Iron / Q000737:chemistry; D008954:Models, Biological; D049878:Mytilus / Q000737:chemistry* / Q000502:physiology; D011506:Proteins / Q000737:chemistry* / Q000378:metabolism; D020449:Repetitive Sequences, Amino Acid; D013059:Spectrum Analysis, Raman
D005290:Ferric Compounds; D011506:Proteins; C037403:adhesive protein, mussel; D004295:Dihydroxyphenylalanine; D007501:Iron