Understanding chiral amplification and chiral interactions in conglomerate crystals

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Louis Pasteur is best known for the process of ‘pasteurization’, typically associated with milk, but Pasteur’s contribution to Chemistry is probably more far reaching. In 1848, Pasteur separated mirror image crystals of sodium ammonium tartrate based solely on visual inspection, and in the process inaugurated the intriguing topic of molecular asymmetry. Chirality, or handedness, is part of our everyday lives and its importance is particularly evident in the pharmaceutical industry, the agrochemical industry, and the food industry. The global market for chiral technology-enabled products is forecast to reach $5.1 billion by 2017. Chiral preference for one handedness of biomolecules is a characteristic of living systems, but the origin of biological homochirality is one of the outstanding mysteries facing scientists today and a precise explanation has yet to be found. A popular theory speculates that surfaces of chiral crystals such as quartz could have been the asymmetric influence that led to the origin of chiral molecules in the prebiotic world. Speculations such as these have drawn a great deal of attention towards chiral crystals. In our lab we are breaking mirror-symmetry and creating chiral crystals of only one handedness (homochiral) using a simple grinding technique. More importantly, we are able to steer the direction (or handedness) of mirror-symmetry breaking using chiral additives (e.g. left- or right-handed amino acids). The main objective of this research program is to investigate the phenomenon of directed mirror-symmetry breaking at the molecular level. We will use classic crystal growing techniques and modern instrumental and computational methods to study the interactions of chiral molecules with chiral crystals. Not only does this research have exciting implications regarding the origin of homochirality, but the interaction of organic molecules with crystalline materials is a continuously expanding research field for chemists, biochemists, and biologists (e.g. formation of bones, teeth, kidney stones and shells). Our work on chiral crystal grinding, may provide important insight into polymorphism and co-crystallization that play critical roles in the solid-state properties of pharmaceuticals.