Biomineralization – Early Onset of Precipitation
Tristan Georges (PhD student):
Crystallization of biominerals does not follow classical mineralization pathways whereby the crystal growth ions-by-ions in a saturated aqueous solution (epitaxial mechanism). In opposition, biominerals crystallization follows non-classical nucleation routes involving successive events. (i) Free ions in solution (Ca2+, PO43-, CO32-) are in equilibrium with prenucleation inorganic species (PNIS) described as (meta)stable ionic clusters. The evolution of these PNIS by aggregation or concentration leads to (ii) the nucleation of nano-objects (nanocrystals, amorphous nanoparticles, etc.) that are transient precursors of the mineral phase. Then (iii) the mineral growth often occurs through oriented particle attachment leading to (iv) the final crystalline biomineral.
Importantly, biominerals crystallization is occurring in vivo under a biological control through the action of dedicated proteins. As a result, these processes are extremely complex and the regulation in vivo of these events by mineralizing proteins is largely unknown. This project aims at clarifying molecular mechanisms of apatite formation controlled (or not) by biological agents.
For this purpose, we use a combined approach of cutting edge analytical techniques at multiple length scales on a structural and dynamical point-of-view :
- Liquid-phase TEM
- D-DNP (dissolution dynamic nuclear polarization) solution-NMR
- Cryo-fixed solid-state NMR
31P D-DNP solution-NMR : 31P spectrum of a CaP solution highlighting the 31P resonance of free phosphate (red) and PNS-bonded phosphate (blue). b) time evolution of the 31P signal amplitude of PNS displaying the formation and the aggregation regime. c) the time-constants evaluated through the 31P NMR experiments.
PhD director: Dr. Thierry Azaïs. Collaborators: Pr. Dennis Kurzbach (University of Vienna, Austria)