The Jaws of<i>Nereis</i>: Microstructure and Mechanical Properties

Birkedal, Henrik; Broomell, Chris C.; Khan, Rashda K.; Slack, Nelle L.; Lichtenegger, Helga C.; Zok, Frank W.; Stucky, Galen D.; Waite, J. Herbert

doi:10.1557/proc-874-l2.8/k2.8

Cited by 6 publications

(5 citation statements)

References 13 publications

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“…SEM was used to calibrate the SIMS depth scale. SIMS was performed toward the bulging area of the jaw pieces. A low-energy electron flood was used for charge compensation, but because some signal drift due to sample charging was unavoidable, all signals were normalized to 12 C (Figure e−g).…”

Section: Methodsmentioning

confidence: 99%

Exploring Gradients of Halogens and Zinc in the Surface and Subsurface of Nereis Jaws

et al. 2006

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The outstanding mechanical properties of impact-bearing tissues, such as Nereis jaws, make their morphology and chemical composition a subject of particular interest. The complex structure of the jaw was recently reported to exhibit molecular gradients that were closely correlated with stiffness and hardness.(18) Accordingly, we have explored the spatial distribution and bonding chemistries of Zn and the halogens in the surface structure of the jaws. Using secondary ion mass spectrometry (SIMS) and scanning electron microscopy (SEM), we found that Cl, Br, and I distributions are enhanced in surface layers of the basal protected portion of the jaw but are shifted to greater depths toward the exposed jaw tip. There are thus two complementary halogen gradients in the jaw: one on the surface that decreases from the base to the tip, coupled to an increasing one in the subsurface layers. The outer surface coating appeared to have granular morphology, in contrast to the anisotropic, fibrous core that dominates the subarchitecture. Using X-ray photoelectron spectroscopy (XPS), we discovered that Zn, I, and Br in the jaws have single chemical environments whereas chlorine is present in two distinct modes (Cl-Zn and Cl-C). Given the inverse relationship between surface exposure and halogen abundance in the jaws, it is unlikely that the halogens contribute directly to mechanical properties such as wear and hardness.

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Section: Methodsmentioning

confidence: 99%

Exploring Gradients of Halogens and Zinc in the Surface and Subsurface of Nereis Jaws

et al. 2006

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“…For all realistic estimates of n, Ē is about 10 % greater than E and is insensitive to the selection of n.) The trends observed herein are in accord with preliminary data on a different section on the same jaw. [43] Microscopy and elemental mapping: The jaw section investigated by nanoindentation was further studied by environmental scanning electron microscopy (ESEM) by using a FEI XL30 with a field emission gun. Other sections, prepared in the same way, were also examined in the ESEM.…”

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Halogenated Veneers: Protein Cross‐Linking and Halogenation in the Jaws ofNereis, a Marine Polychaete Worm

et al. 2006

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Mineralized tissues are produced by most living organisms for load and impact functions. In contrast, the jaws of the clam worm, Nereis, are hard without mineralization. However, they are peculiarly rich in halogens, which are associated with a variety of post-translationally modified amino acids, many of which are multiply halogenated by chlorine, bromine, and/or iodine. Several of these modified amino acids, namely dibromohistidine, bromoiodohistidine, chloroiodotyrosine, bromoiodotyrosine, chlorodityrosine, chlorotrityrosine, chlorobromotrityrosine, and bromoiodotrityrosine, have not been previously reported. We have found that the distributions of Cl, Br, and I differ: Cl is widespread whereas Br and I, although not colocalized, are concentrated in proximity to the external jaw surfaces. By using nanoindentation, we show that Br and I are unlikely to play a purely mechanical role, but that the local Zn and Cl concentrations and jaw microstructure are the prime determinants of local jaw hardness. Several of the post-translationally modified amino acids are akin to those found in various sclerotized structures of invertebrates, and we propose that they are part of a cross-linked protein casing.

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“…In contrast to Mn 2+ , the Zn 2+ -loaded gels displayed atypical behavior with respect to the melting point, which was higher than the salt-free control up to a threshold concentration of 0.50 M Zn 2+ . We suggest that this is due to zinc binding to specific gelatin constituents forming strong cross-links, as is the case for trivalent ions. , Zinc is a well-known ligand in protein chemistry and has been used to form coordination cross-link-strengthened protein materials in marine worm jaws. − Its complex cross-linking capability has been demonstrated in the literature using collagen analogues where it has also been shown to be reversible. − …”

Section: Discussionmentioning

confidence: 91%

Influence of Metal Ions on the Melting Temperature, Modulus, and Gelation Time of Gelatin Gels: Specific Ion Effects on Hydrogel Properties

2018

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The impact of ions on hydrogel strength is not well understood, in particular with regards to specific ion effects for cations. Herein, we find that divalent and monovalent cations in most cases reduce the modulus and melting temperature while increasing the gelation time of gelatin hydrogels. This behavior is in contrast to the well-known stiffening effect of trivalent metals. The melting temperature, the logarithm of the gelation time, and the logarithm of the amplitude of the complex modulus were found to follow a power law dependence on ionic strength: kI x . The power law exponent, x, was found to be universal within the groups of monovalent and divalent cations. The prefactor k depended linearly on the ionic radius, which was used as a proxy for ion polarizability. The slope of this linear dependence was different for monovalent and divalent cations.

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The Jaws ofNereis: Microstructure and Mechanical Properties

Cited by 6 publications

References 13 publications

Exploring Gradients of Halogens and Zinc in the Surface and Subsurface of Nereis Jaws

Exploring Gradients of Halogens and Zinc in the Surface and Subsurface of Nereis Jaws

Halogenated Veneers: Protein Cross‐Linking and Halogenation in the Jaws ofNereis, a Marine Polychaete Worm

Influence of Metal Ions on the Melting Temperature, Modulus, and Gelation Time of Gelatin Gels: Specific Ion Effects on Hydrogel Properties

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