title: Coexistence of amorphous and crystalline calcium carbonate in skeletal tissues.
abstract: We describe a new type of composite skeletal tissues in which calcite and stabilized amorphous calcium carbonate (ACC) coexist in well-defined domains. The organisms that form such structures are widely separated in the animal kingdom phylogenetic tree: calcareous sponges and ascidians. This paper compares the microstructures of their composite skeletal elements: The triradiate spicules from the sponge Clathrina are composed of a core of calcite embedded in a thick layer of ACC and covered by a thin calcitic envelope; the tunic spicules from the ascidian Pyura pachydermatina are composed of a core of ACC enveloped by an insoluble organic sheath and covered by a thick calcitic layer. We compare and contrast the macromolecules associated with different amorphous and crystalline phases and their ability to induce the formation of stabilized ACC in vitro.
authors.affiliation: Bell Laboratories/Lucent Technologies, Murray Hill, New Jersey 07974-2008, USA. jaizenberg@lucent.com
authors.forename: J
authors.initials: J
authors.lastname: Aizenberg
authors.forename: S
authors.initials: S
authors.lastname: Weiner
authors.forename: L
authors.initials: L
authors.lastname: Addadi
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002113:Calcification, Physiologic / Q000502:physiology*; D002119:Calcium Carbonate / Q000737:chemistry* / Q000378:metabolism; D003460:Crystallization; D018360:Crystallography, X-Ray; D016326:Extracellular Matrix Proteins / Q000737:chemistry / Q000502:physiology; D008854:Microscopy, Electron; D011161:Porifera / Q000502:physiology; D013055:Spectrophotometry, Infrared; D014561:Urochordata / Q000502:physiology; D014961:X-Ray Diffraction
chemical_list: D000596:Amino Acids; D016326:Extracellular Matrix Proteins; D002119:Calcium Carbonate