Direct observation of the transition from calcite to aragonite growth as induced by abalone shell proteins

The mixture of EDTA-soluble proteins found in abalone nacre are known to ca use the nucleation and growth of aragonite on calcite seed crystals in supe rsaturated solutions of calcium carbonate. Past atomic force microscope stu dies of the interaction of these proteins with calcite crystals did not obs erve this transition because no information about the crystal polymorph on the surface was obtained. Here we have used the atomic force microscope to directly observe changes in the atomic lattice on a calcite seed crystal af ter the introduction of abalone shell proteins. The observed changes are co nsistent with a transition to (001) aragonite growth on a (1014) calcite su rface.