Interactions Between Acidic Macromolecules and Structured Crystal Surfaces. Stereochemistry and Biomineralization

Abstract

Some organisms are capable of exerting exquisite control ower the crystals they form. Key components in this process are unusually acidic proteins (aspartic acid-rich). In this study we use a series of calciun dicarboxylic acid salts to investigate in vitro how these proeins are capable of interacting specifically with certain crystal faces. The property that characterizes the affected faces is the orientation of sets of carboxyl groups which are perpendicular to the plane of the face in well defined motifs. Calcite crystals grown urder the same conditions were ohserved to nucleate off a stereochemically equivalent face and to be oriented with their c axes perpendicular to the substrate. We show that this is a result of the acidic proteins adsorbing onto the substrate and then inducing oriented nucleation. This study underscores the importance of these proteins in biological crystal growth and demonstrates some of the basic mechanisms involved.