REGULATION OF CALCITE CRYSTAL MORPHOLOGY BY INTRACRYSTALLINE ACIDIC PROTEINS AND GLYCOPROTEINS

Many biologically Formed calcite crystals contain intracrystalline mac romolecules, The ways in which they interact with growing calcite crys tals were evaluated by monitoring changes in the morphology of calcite crystals grown in vitro in their presence, Macromolecules were extrac ted from within isolated prisms from the prismatic layer of the shell of the mollusk Atrina rigida and from spines of the sea urchin Paracen trotus lividus. Two modes of interaction were identified; the interact ion of highly acidic proteins with calcite planes perpendicular to the c crystallographic axis and the interaction of glycoproteins with pla nes roughly parallel to the c axis, By different preparative procedure s we demonstrated that the polysaccharide moieties of the sea urchin s pine glycoproteins are directly involved in the latter mode of interac tions, We suggest that organisms utilize the abilities of these macrom olecules to interact in different ways with calcite crystals, and in s o doing fine-tune aspects of the control of crystal growth in vivo.