Conférence

Prof. Marc McKee - The structure of avian (chicken) eggshell

Réalisation : 23 mars 2021 Mise en ligne : 23 mars 2021
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Descriptif

The functional properties of biomineralizedstructures found in Nature result from interactions between their hybridcomponents – both organic (mostly proteins) and inorganic (mineral) phases – togenerate hierarchical organization across different length scales.  In its dual function, the calcitic avianeggshell provides a protective barrier for the enclosed developing chick embryowhile also serving to provide calcium for the growing chick skeleton by theprocess of shell dissolution.  Here, adetailed structural analysis (including a description of nanostructure) isgiven for the eggshell produced by the domesticated chicken, along with changesthat occur following eggshell dissolution – a shell-thinning and weakeningprocess leading to hatching of the chick (pipping) which occurs after egg fertilizationand incubation.  Eggshell containsabundant proteins, and the localization of some of these (particularlyosteopontin) will be described at the ultrastructural level, and correlatedwith generating nanostructure and shell hardness.  X-ray and electron imaging and diffractiondata, together with atomic force microscopy observations, describe an alignednanostructure of mineral within the shell. A similar nanostructure could be reproduced in synthetic calcitecrystals by the simple addition of osteopontin, which becomes occluded withinthe calcite to generate this mineralization pattern.  Taken together, these findings are consistentwith this protein's mineral-binding and regulatory role in biomineralization ina large number of biological systems, and point to a highly conserved, mineralnanostructure-regulating activity of osteopontin conserved over at least 300million years of evolution.

 

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