engleski

Influence of natural acidic macromolecules extracted from sea corals on calcium carbonate precipitation

One of the most abundant minerals in nature and consequently one of the most intensively investigated precipitation system is calcium carbonate, CaCO3. Calcium carbonate forms six solid modifications: three polymorphs (calcite, aragonite and vaterite), calcium carbonate hexahydrate, calcium carbonate monohydrate and amorphous calcium carbonate. In biological systems, CaCO3 predominantly appears as calcite and/or aragonite and less commonly as vaterite and/or amorphous calcium carbonate. Calcium carbonate biominerals (formed during the biomineralization) are natural biocomposites in which the inorganic phase is principal component with the organic matrix being present as a minor fraction.1 Molluscs shells, pearls and corals are examples of such natural biocomposites. Extraordinary physical and chemical properties of these materials are the result of a controlled crystallization of CaCO3, that is, essentially, induced by the organic matrix. Aragonite, one of calcium carbonate polymorphs, is the major mineral component in corals. Due to the considerable susceptibility of corals on temperature changes, the global warming is one of the greatest threats for corals and coral reefs existence. In addition the increased atmospheric CO2 reacts with sea water and causes its acidification, which may influence the CaCO3 precipitation in calcifying organisms such as corals. An accurate evaluation of global warming effects on corals requires the knowledge of coral biomineralization processes that is still poorly understood In order to determine the role of soluble, hydrophilic, organic macromolecules (SOM), in a process of coral biomineralization, the effects of soluble biomacromolecules extracted from the Mediterranean coral skeleton of Balanophyllia europea2 and Leptosammia pruvoti, on calcium carbonate precipitation has been investigated. The results of kinetics and structural analysis indicated that the respective macromolecules of SOM strongly interact with aragonite crystals. References: 1 Mann, S., (2001). Biomineralization. Principles and Concepts in Bioinorganic Materials Chemistry, Oxford University Press, New York. 2 Goffredo, S., Vergni, P., Reggi, M., Caroselli, E., Sparla F., Levy O., Dubinsky Z.  Falini, G. (2011). PLoS ONE 6(7) e22338.

calcium carbonate; aragonite; corals; biomineralization

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