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Issue 25, 2018
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Intracrystalline incorporation of nacre protein hydrogels modifies the mechanical properties of calcite crystals: a microcompression study

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Abstract

The fracture toughness of mollusk shell nacre has been attributed to many factors, one of which is the intracrystalline incorporation of nacre-specific proteins. Although mechanical force measurements have been made on the nacre layer and on individual calcium carbonate crystals containing occluded organic molecules and macromolecules, there are few if any studies which examine the impact of occluded proteins on the mechanical properties of calcium carbonate crystals. To remedy this, we performed microcompression studies of calcite crystals grown in the presence and absence of two recombinant nacre proteins, r-AP7 (H. rufescens, intracrystalline proteome) and r-n16.3 (P. fucata, framework proteome), both of which are known aggregators that form hydrogel nanoinclusions within in vitro calcite. We find that, relative to protein-free calcite, the intracrystalline inclusion of either r-AP7 or r-n16.3 nacre protein hydrogels within the calcite crystals leads to a reduction in strength. However, nacre protein-modified crystals were found to exhibit elastic deformation under force compared to control scenarios, with no discernable differences noted between intracrystalline or framework protein-modified crystals. We conclude from our in vitro microcompression studies that the intracrystalline incorporation of nacre proteins can contribute to fracture-resistance of the crystalline phase by significantly reducing both modulus AND critical strength.

Graphical abstract: Intracrystalline incorporation of nacre protein hydrogels modifies the mechanical properties of calcite crystals: a microcompression study

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Publication details

The article was received on 02 May 2018, accepted on 06 Jun 2018 and first published on 08 Jun 2018


Article type: Communication
DOI: 10.1039/C8TB01156G
Citation: J. Mater. Chem. B, 2018,6, 4191-4196
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    Intracrystalline incorporation of nacre protein hydrogels modifies the mechanical properties of calcite crystals: a microcompression study

    J. Risan, G. Jain, M. Pendola and J. S. Evans, J. Mater. Chem. B, 2018, 6, 4191
    DOI: 10.1039/C8TB01156G

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