Impact of Chiral Molecules on the Formation of Biominerals: A Calcium Oxalate Monohydrate Example

Minerals in organisms often exhibit chiral shapes. The physical mechanism by which chiral information is transferred from molecules to crystal morphology is still not well-defined. In this article, we investigate the influence of chiral molecules on the growth of calcium oxalate monohydrate (COM), a mineral phase commonly found in solanacea plants and human kidney stones, by combining in situ atomic force microscopy (AFM) and molecular mechanics modeling. Three synthetic 6-residue linear aspartic acid-rich peptides of l-Asp6, d-Asp6, and l-Asp3–d-Asp3 are used as surrogate molecules, with the first two being an enantiomeric pair. Our observations show that, while both l-Asp6 and d-Asp6 modify the growth of COM by interacting with specific steps on existing faces, the effect from the peptide l-Asp3–d-Asp3 on COM growth is minimal. Furthermore, AFM images reveal that the two enantiomers have different binding preferences to steps that are related by mirror symmetry. As a result, growth morphologies with dif...