Vaterite, a polymorph of CaCO 3, has attracted attention in the biomineralization field because it is the mineral phase of the solitary stolidobranch ascidian Herdmaniamomus 16, an invertebrate having a hierarchically organized helical skeleton.
However, until now, knowledge of how chiral molecules might direct nano-sized calcium carbonate ‘building blocks’ to form larger chiral hierarchical architectures remains unknown. In biology, differences in the handedness of biomineralized, chiral architectures of calcium carbonate polymorphs are thought to result from the actions of chiral biomolecules 4, 10, 11, 12, 13, 14, 15. In nonbiological systems, formation of chiral crystals has been described, induced by abiotic twist, optical effects and surface stress 7, 8, 9. Chirality is ubiquitous in biology, including in calcium carbonate biomineralization, and it is found in many hardened structures of invertebrate marine and terrestrial organisms, notably helical gastropod shells and now-extinct ammonites 2, 3, 4, 5, 6. These findings suggest a molecular mechanism for how biomineralization-related enantiomers might exert hierarchical control to form extended chiral suprastructures.Ĭhirality-the fundamental phenomenon of handedness-ranges across nature from the atomic arrangement of amino acids to the long, macroscopically helical tooth of the narwhal Monodon monoceros 1. Nanoparticle tilting after binding of chiral amino acids is proposed as a chiral growth mechanism, where a ‘mother’ subunit nanoparticle spawns a slightly tilted, consequential ‘daughter’ nanoparticle, which by amplification over various length scales creates oriented mineral platelets and chiral vaterite suprastructures. Chiral, vaterite toroidal suprastructure having a ‘right-handed’ (counterclockwise) spiralling morphology is induced by L-enantiomers of Asp and Glu, whereas ‘left-handed’ (clockwise) morphology is induced by D-enantiomers, and sequentially switching between amino-acid enantiomers causes a switch in chirality. Here we show that chiral, hierarchically organized architectures for calcium carbonate (vaterite) can be controlled simply by adding chiral acidic amino acids (Asp and Glu). Chirality is ubiquitous in biology, including in biomineralization, where it is found in many hardened structures of invertebrate marine and terrestrial organisms (for example, spiralling gastropod shells).
0 kommentar(er)
