The study by Addadi and Weiner investigates the interactions between acidic matrix macromolecules and crystals, particularly calcite, during biomineralization. They found that these macromolecules, which are rich in aspartic acid, exhibit a stereochemical property that allows them to nucleate calcite crystals on specific crystal faces. This property is essential for the interaction and is observed when proteins are adsorbed onto a rigid substrate. The study uses in vitro experiments to examine the effects of these macromolecules on crystal growth, revealing that they specifically influence the orientation of carboxylate groups on the crystal surfaces. The findings highlight the importance of these acidic proteins in regulating crystal growth and suggest that the stereochemical requirements are crucial for the formation of well-structured biogenic crystals. The results also indicate that the same proteins can act as nucleators of calcite when adsorbed on a rigid surface, providing insights into the mechanisms of crystal growth in vivo.The study by Addadi and Weiner investigates the interactions between acidic matrix macromolecules and crystals, particularly calcite, during biomineralization. They found that these macromolecules, which are rich in aspartic acid, exhibit a stereochemical property that allows them to nucleate calcite crystals on specific crystal faces. This property is essential for the interaction and is observed when proteins are adsorbed onto a rigid substrate. The study uses in vitro experiments to examine the effects of these macromolecules on crystal growth, revealing that they specifically influence the orientation of carboxylate groups on the crystal surfaces. The findings highlight the importance of these acidic proteins in regulating crystal growth and suggest that the stereochemical requirements are crucial for the formation of well-structured biogenic crystals. The results also indicate that the same proteins can act as nucleators of calcite when adsorbed on a rigid surface, providing insights into the mechanisms of crystal growth in vivo.