S. Albeck et al., INTERACTIONS OF VARIOUS SKELETAL INTRACRYSTALLINE COMPONENTS WITH CALCITE CRYSTALS, Journal of the American Chemical Society, 115(25), 1993, pp. 11691-11697
The calcitic skeletal elements of many organisms contain small amounts
of proteins and glycoproteins which are incorporated within single cr
ystals of calcite. Extraction and partial purification of the intracry
stalline macromolecules allowed the identification of their interactio
ns with synthetic calcite crystals. Specific interactions were inferre
d from induced morphological modifications associated with the develop
ment of new faces on calcite crystals grown in the presence of these m
acromolecules in solution. Partially purified macromolecules extracted
from within sea urchin spines interacted only with faces roughly para
llel to the c crystallographic axis of calcite, producing well-develop
ed (01l} faces. Macromolecules extracted from within mollusk shell pri
sms separated into two fractions each having a characteristic amino ac
id composition and displayed distinct specific interactions with growi
ng calcite crystals: A highly acidic fraction interacts with the {001}
set of faces, while a different fraction, which is only moderately ac
idic and has an amino acid composition similar to that of the sea urch
in spines, interacts specifically with the {01l} set of faces. Magnesi
um, a major ionic component of the sea urchin spines, causes the devel
opment of the {011} set of crystal faces. The existing knowledge on th
e direction of intercalation of the macromolecules in the biogenic cry
stals agrees with the interacting planes in the synthetic crystals, su
ggesting the relevance of our in vitro assay to the system in vivo. We
suggest that each separate mode of interaction may infer a specific r
ole in the regulation of biological crystal growth.