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Chiral Amino Acids Alter Mineral Structure
REBECCA RAWLS
When chiral amino acids such as aspartic acid bind to growing calcite crystals, they alter the morphology of the crystal. Staff scientists Christine A. Orme and James J. De Yoreo of Lawrence Livermore National Laboratory, associate professor of geological sciences Patricia M. Dove of Virginia Tech, and their colleagues find that the regular shape of calcite crystals (left) becomes partially rounded when the crystals are grown from solutions containing L-aspartic acid (center) or D-aspartic acid (right). As can be seen in these atomic force microscopy images, the crystal morphologies produced by the L- and D-amino acids are mirror images of one another [Nature, 411, 775 (2001)].
"The effect is primarily one of modifying the surface energetics of calcite," De Yoreo says. Modeling experiments show that D- and L-amino acids bind preferentially to different steps on the calcite crystal surface, and that binding changes the shape of those steps.
Living organisms use organic molecules to direct crystal growth in ways that are the envy of materials scientists, De Yoreo says. This study offers a way to begin to understand that control on a molecular scale.
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