engleski

The role of alanine, aspartic acid and lysine in calcium carbonate biomineralization

Calcium carbonates could be biomineralized by different invertebrate organisms, either in a form of certain polymorph (calcite, vaterite and aragonite) or hydrated modification. The formation of specific crystal modification or appearance of appropriate morphological form can be influenced by parameters like temperature, pH or supersaturation, as well as by the presence of inorganic components or biomolecules. At that, the important organic components of extrapallial fluids, in which the biomineralization takes place, are proteins. Previously, the influence of isolated fragments of proteins extracted from mineralized tissues, or their synthetic macromolecular analogues has been investigate in the appropriate calcium carbonate model systems.1, 2 , 3 The aim of this research is to investigate the influence of amino acids, selected as simple models of biomacromolecules supposed to be responsible for nucleation, growth and transformation of calcium carbonates in biomineralizating systems. For that purposes, alanine (Ala), lysine (Lys) and aspartic acid (Asp) were used. Besides their chemical differences, at the conditions applied in the selected model systems the used amino acids have different net charges as well: Ala is neutral, Lys is positive and Asp is negatively charged. The results of potentiometric, spectroscopic, chemical, structural (PXRD) and microscopical (SEM) analyses indicated the overall inhibition of calcite precipitation in the presence of Lys and Aps, that (inhibition) is probably caused by slower transformation of initially formed vaterite, into calcite.4 Since both amino acids are charged at applied experimental conditions, some non specific surface interactions are assumed to be responsible for observed effect. The additional kinetic experiments and molecular modelling will be necessary to reveal the nature of respective intermolecular interactions.

biomineralization ; calcium carbonate ; amino acids

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