INVESTIGATION OF INTERACTIONS BETWEEN DRUG ENANTIOMERS AND FLAVOPROTEIN AS A CHIRAL SELECTOR BY AFFINITY CAPILLARY ELECTROPHORESIS

Interactions between drug enantiomers and flavoprotein as a pseudo chi ral stationary phase were investigated by using affinity capillary ele ctrophoresis (CE) in order to avoid the effects of nonspecific interac tions that occur in chiral HPLC. Circular dichroism (CD) measurement w as used to monitor changes of the secondary structure of flavoprotein under various analysis conditions in affinity CE. The chiral discrimin ation region for ketoprofen on the flavoprotein surface was concluded to consist of alpha-helix structure, and the decrease of chiral separa tion ability with increase of methanol content in the electrophoretic buffer was directly related to conformational change of the alpha-heli x. Studies with chemically modified flavoprotein indicated that two ty pes of interaction at the chiral discrimination region are required fo r chiral separation: pi-pi interaction of a tryptophan residue with th e aromatic ring of ketoprofen, and ionic interaction of the carboxyl g roup of ketoprofen with an amino group and a carboxyl group of the pro tein.