Forming nacreous layer of the shells of the bivalves Atrina rigida and Pinctada margaritifera: An environmental- and cryo-scanning electron microscopy studyReport as inadecuate




Forming nacreous layer of the shells of the bivalves Atrina rigida and Pinctada margaritifera: An environmental- and cryo-scanning electron microscopy study - Download this document for free, or read online. Document in PDF available to download.

* Corresponding author 1 Department of Structural Biology 2 Chemical Research Support Rehovot 3 BOME - Biologie des organismes marins et écosystèmes 4 ISTO - Institut des Sciences de la Terre d-Orléans

Abstract : A key to understanding control over mineral formation in mollusk shells is the microenvironment inside the pre-formed 3-dimensional organic matrix framework where mineral forms. Much of what is known about nacre formation is from observations of the mature tissue. Although these studies have elucidated several important aspects of this process, the structure of the organic matrix and the microenvironment where the crystal nucleates and grows are very difficult to infer from observations of the mature nacre. Here, we use environmental- and cryo-scanning electron microscopy to investigate the organic matrix structure at the onset of mineralization in the nacre of two mollusk species: the bivalves Atrina rigida and Pinctada margaritifera. These two techniques allow the visualization of hydrated biological materials coupled with the preservation of the organic matrix close to physiological conditions. We identified a hydrated gel-like protein phase filling the space between two interlamellar sheets prior to mineral formation. The results are consistent with this phase being the silk-like proteins, and show that mineral formation does not occur in an aqueous solution, but in a hydrated gel-like medium. As the tablets grow, the silk-fibroin is pushed aside and becomes sandwiched between the mineral and the chitin layer.

Keywords : Biomineralization Mollusk shell nacre Matrix macromolecules Cryo-scanning electron microscopy Silk fibroin





Author: Fabio Nudelman - Eyal Shimoni - Eugenia Klein - Marthe Rousseau - Xavier Bourrat - Evelyne Lopez - Lia Addadi - Steve Weiner -

Source: https://hal.archives-ouvertes.fr/



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