EFFECTS OF AMINO ACIDS, MAGNESIUM, AND MOLLUSCAN EXTRAPALLIAL FLUID ON CRYSTALLIZATION OF CALCIUM CARBONATE:IN VITROEXPERIMENTS

Open Access
Publisher Website
Google Scholar
Abstract
The extrapallial fluid (EPF), the fluid component of the shell-forming system of molluks, was examined for its effect on the rate of CaCO3 crystal formation in vitro. The medium was an artificial inorganic extrapallial fluid supersaturated with respect to CaCO3. EPF of the bivalves Crassostrea virginica and Mercenaria mercenaria strongly inhibited CaCO3 crystallization in high dilution. The inhibitory material had negatively charged groups as indicated by the removal of inhibition subsequent to passage through a Sephadex column and the restoration of inhibition in material eluted from the column with 2.0 M NaCl. Polyaspartic and polyglutamic acids with COO- groups also inhibited crystal formation whereas polyamino acids lacking those groups and free amino acids were without effect. The inhibition by the acidic polyamino acids suggests that polypeptides known to be present in EPF are 1 possible cause of inhibition of crystal formation by EPF. Mg present in EPF was also strongly inhibitory. The observed inhibition of in vitro crystallization by EPF and Mg indicates that these substances could be factors in governing CaCO3 deposition rate in molluscan shell.