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Séminaire recherche du 3 juin à 14h30

Thématique : Biominéralisation

par Laurent Tranchant - publié le , mis à jour le

3 juin 2022 – 14h30-16h00

Frédéric Marin – Directeur de recherche CNRS
Responsable adjoint de l’équipe SAMBA au laboratoire de biogéosciences à
l’Université de Bourgogne – Franche Comté
UMR CNRS/uB/EPHE 6282 Biogéosciences
Université de Bourgogne, 6 bd Gabriel, 21000 DIJON

Titre : Shell biomineralization in molluscs : what proteomics teaches us

Résumé : Biominerals are organo-minerals structures produced by living systems. They contribute to the adaptation of living organisms to different environments by fulfilling a variety of physiological functions that go along with adapted morphologies. One of the aims of biomineralization is to understand how organisms "sculpt" these complex morphologies at nano and molecular scales : we know for example that occluded organic matrix proteins influence the lattice parameters of biominerals and that many of them strongly interact in vitro with the mineral phase, but their exact roles are still to be known. In molluscs, high-throughput screening approaches (proteomics, transcriptomics) performed in the last twelve years on shell matrices have revealed the huge diversity of shell proteins and molecular functions associated to the controlled deposition of calcium carbonate crystals. Proteins of the shell matrix are not only involved in physical roles (nucleation, guiding the mineral growth in privileged directions) but also in the protection of the system (’immunity’), in the dialog between the epithelial cells that secrete the ingredients for calcifying and the mineralization front itself and in other less understood functions. Few examples will be treated in this seminar. A particular emphasis will be put on the shell proteins that exhibit intrinsically disordered domains.


Marie Albéric – Chargée de recherche CNRS au LCMCP
Laboratoire de chimie de la matière condensée de Paris, Tour 44-43 / 4ème
étage, 4, Place Jussieu, 75005 Paris

Titre : Biomineralization in sea urchins : A view on amorphous calcium carbonate occurrence, stabilization and crystallization

Résumé : Some biomineralized structures with intricate shapes and morphologies, such as the colorful skeletal elements of sea urchins grow via the deposition of hydrated amorphous calcium carbonate (ACC) that subsequently transforms into anhydrous ACC and finally crystallizes into single-crystalline calcite. Applying the heat-stimulated crystallization of remnant anhydrous ACC and destruction of intra-crystalline organic molecules in those biominerals, we evidenced by HR-XRD, calcite lattice distortions originating in strong atomic interactions at the organic-inorganic interfaces and showed by in situ heating SAXS measurements, the evolution of nano-pores, which likely compensate mineral volume shrinkage during ACC crystallization and organics removal. Our results suggest that ACC crystallization proceeds as far as organics can serve as space-filling and accommodate for density changes due to the amorphous to crystalline transformation. Beyond that point, crystallization is hindered and ACC kinetically trapped within the biominerals in the form of thin layers. We propose that ACC thin layers are adjacent to the organic/inorganic interfaces and may serve as buffer layers between intracrystalline organics and crystalline calcite with elastic energy stored in the form of lattice strains. In addition, studying in vitro ACC systems with pair distribution function analysis during heat induced crystallization we showed that water governs the local structural rearrangement prior to crystallization. Finally, we are extending our approach to study the role of organic pigments in the biomineralization pathways of these colorful biominerals in which polyhydroxylated naphthoquinones are entrapped and may very well be involved in shaping these large single crystalline biominerals by playing a role in the stabilization and crystallization processes of ACC.


Le séminaire aura lieu sous format hybride. Si vous souhaitez y assister, vous pouvez demander le lien de connexion aux organisateurs : Luca Polacchi (luca.polacchi@synchrotron-soleil.fr) et Laurent Tranchant (laurent.tranchant@synchrotron-soleil.fr).


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