Protein-Mineral Interaction of Purified Nacre Proteins with Calcium Carbonate Crystals

Nacre, a fascinating biogenic material consisting of calcium carbonate and organic molecules, presents remarkable mechanical and chemical properties that far exceed those of the pure components. Nacre is created by a self-organizing process guided by organic macromolecules. In particular proteins specifically control and regulate the nucleation and growth of the mineral phase, influencing the crystal morphology and polymorph selection.In this work new strategies to extract and purify proteins from the nacre of Haliotis laevigata in their native and functional state were developed and mechanisms of interaction between native nacre proteins with calcium carbonate in solution and calcium carbonate minerals were investigated. In particular the function of the intracrystalline proteins, a novel group of proteins characterized for the first time in nacre, and perlucin and perlinhibin, two already sequenced nacre proteins, were elucidated. It has been shown that each nacre protein presents a very specific and unique function in terms of calcium carbonate mineralization.