A New Approach to Chiral Enrichment by Exposure of Racemates of Amino Acids to Sonochemically-Prepared BSA Microspheres

This preliminary study describes a one-step sonochemical formation of Bovine Serum Albumin (BSA) microspheres and their chiral interaction with several amino acids. Partial separation between enantiomers of various amino acids was accomplished by the interaction of these microspheres with solutions of racemic amino acids. The highest rate of enantiomeric enrichment was attained for D,L-cysteine, where 59% enantiomeric excess (ee) of the L-cysteine was measured. This indicates the preferrential interaction of the BSA microspheres with the D-enantiomer of cystein. No chiral activity was observed for unsonicated BSA molecules. All other D,L-amino acids that were examined provided enrichment of the D-enantiomer albeit in lower ee values. D,L-cysteine interacted with the BSA microspheres leading to L-enantioselective enrichment up to 59 % ee at room tempertaure and 72% at 5 °C. Chiral enrichment was also carried out succesfully with other protein microspheres such as Avidin microspheres. In this case up to 41 % ee was acheived on interaction with DL-phenylalanine. Our simple and facile method opens a new window for enantiomeric separation of racemic compounds.