AFM Investigation of the Interaction of Chiral Amino Acids with the (104) Face of Calcite

摘要

In biomineralized tissue, Nature often uses a single crystal system to form tools with widely varied form and functionality. To accomplish this, organisms have developed methods to deterministically modify and control crystal habit, commonly creating shapes with lower symmetry than is possessed by the pure crystal. In this paper we use atomic force microscopy to investigate the effect of chiral amino acids on calcite growth. We show that the atomic steps and resultant macroscopic shape exhibit a lower symmetry that reflects the chirality of the amino acid. We use this result to constrain the possible stereospecific binding sites. We argue that the change in morphology is not due to the incorporation of the amino acid, but rather that it acts like a surfactant changing the energetics of the interface. These results suggest that the conventional paradigm for understanding the geometrical and chemical aspects of biomineralization in terms of stereochemical recognition should be expanded to capture the energetic controls that determine the mechanisms of mineral modification by biomolecules.