Protein-induced, previously unidentified twin form of calcite.

Boaz Pokroy (1) , Moshe Kapon (2) , Frédéric Marin (3) , Noam Adir (2) , Emil Zolotoyabko (1)

1 Department of Materials Engineering
2 Faculty of Chemistry
3 BGS - Biogéosciences [UMR 6282]

Using single-crystal x-ray diffraction, we found a formerly unknown twin form in calcite crystals grown from solution to which a mollusc shell-derived 17-kDa protein, Caspartin, was added. This intracrystalline protein was extracted from the calcitic prisms of the Pinna nobilis shells. The observed twin form is characterized by the twinning plane of the (108)-type, which is in addition to the known four twin laws of calcite identified during 150 years of investigations. The established twin forms in calcite have twinning planes of the (001)-, (012)-, (104)-, and (018)-types. Our discovery provides additional evidence on the crucial role of biological macromolecules in biomineralization.

Mots clés: biomineralization; crystal growth; twinning; x-ray diffraction; calcium carbonate

Domaines: Biomatériaux

Boaz Pokroy, Moshe Kapon, Frédéric Marin, Noam Adir, Emil Zolotoyabko. Protein-induced, previously unidentified twin form of calcite.. Proceedings of the National Academy of Sciences of the United States of America, 2007, 104 (18), pp.7337-7341. ⟨10.1073/pnas.0608584104⟩. ⟨hal-00198458⟩