Regensburg 2007 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 20: POSTER: Biological Systems + New Materials

CPP 20.6: Poster

Wednesday, March 28, 2007, 16:00–18:30, Poster B

Biological Calcium Carbonate Precipitation — •Sigrid Hennig, Christian Soor, Sabine Hild, and Andreas Ziegler — Central Facility for Electron Microscopy; University of Ulm, Albert-Einstein-Allee 11, 89069 Ulm

Biominerals have unique structures and morphologies, which acquire much better performance than geological minerals. Calcium carbonate is the most common mineral found in living organisms occurring as calcite, aragonite, and, to a lesser extent, vaterite and hydroxy calcite. Interestingly many organisms form amorphous calcium carbonate (ACC) that would be unstable in-vitro. ACC is thought to be a precursor phase for crystalline modifications and, because of its high solubility, occurs in transient calcium carbonate reservoirs. The terrestrial crustacean Porcellio scaber develops large ACC reservoirs that are used for the mineralization of the new cuticle synthesized before the old cuticle is shed in a process called moulting. In order to investigate the formation and stabilization of biogenic ACC under physiological conditions we analysed the cation composition in the region of ACC formation, isolated the proteins of the organic matrix and tested their effects on mineral precipitation. We show that under these conditions the physiological Mg concentration (13 mM, Ca:Mg about 1:1) has a large effect on crystal morphology. Matrix proteins prevent crystal precipitation and lead to formation of 50 nm large colloidal particles. Depending on matrix concentration these particles are arranged in hollow sphere super structures resembling ACC spherules in P. scaber during natural degradation.