title: Protein-induced, previously unidentified twin form of calcite.
abstract: 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.
authors: Department of Materials Engineering, Technion-Israel Institute of Technology, Haifa 32000, Israel. bpokroy@tx.technion.ac.il
authors: B
authors: B
authors: Pokroy
authors: M
authors: M
authors: Kapon
authors: F
authors: F
authors: Marin
authors: N
authors: N
authors: Adir
authors: E
authors: E
authors: Zolotoyabko
mesh_terms: D002119:Calcium Carbonate / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry*
chemical_list: D011506:Proteins; D002119:Calcium Carbonate