Chirality change in helical crystals of potassium dichromate

Specific morphologies occasionally appear in the crystal growth in gels. Potassium dichromate (K2Cr2O7) crystals grown in gelatin gel have been found to exhibit various morphologies by varying only initial concentrations of K2Cr2O7 and gelatin in the medium. Particularly unique are huge helical crystals grown under the condition of high concentrations of both solute and gelatin, and right-handedness is overwhelmingly superior to left-handedness in helical chirality. We have found for the first time that huge left-handed helical crystals grow when adding acidic amino acids such as aspartic acid or glutamic acid, revealing the existence of an enantiomer of huge helical crystals of K2Cr2O7. The present finding is expected to be relevant to biocrystallization such as the growth of seashells.