MINERALS AND MOLECULES: APPLICATION OF MICROARRAY TECHNOLOGY TO PROBE CHIRAL INTERACTIONS

Life possesses a striking preference for chiral (i.e., handed) amino acids, sugars and other essential biomolecules. The ability of some mineral surfaces to adsorb selectively chiral molecules may have contributed to the origins of this biochemical homochirality. Mineral-molecule interactions, furthermore, provide a promising avenue for the development of commercial processes for chiral drug synthesis and purification (a $100 billion annual industry). We have modified DNA microarray technology to investigate chiral interactions between molecules and mineral surfaces. Originally designed for high throughput data mining of genomes, these arrays can fit up to 120,000 separate tests per mineral section. This technology thus is ideal for the kind of combinatorial chemistry necessary for screening interactions between numerous crystal surfaces and organic molecules. We employed a Telechem Spotbot microarrayer to print small volumes (0.7 nL) of fluorescent labeled L- and D-amino acids onto (110) orthoclase feldspar, (214) calcite, (100) quartz, and (001) muscovite mica surfaces, at up to 20 different dilutions, each in quintuplicate to allow for surface variation. We scanned surfaces for fluorescence with a Genepix 4000B scanner, washed the surfaces with saline solution, and then scanned again to observe preferential molecular binding post-wash. Differences in molecular adsorption are revealed by differences in fluorescent intensity of spot arrays. For example, we observe significant and quantifiable preferential retention of L lysine on the (100) face of right-handed quartz compared to that of left-handed quartz. We conclude that microarray technology holds the promise for rapid surveying of mineral-molecule interactions.