SEPARATION OF AMINO-ACID AND PEPTIDE STEREOISOMERS BY NONIONIC MICELLE-MEDIATED CAPILLARY ELECTROPHORESIS AFTER CHIRAL DERIVATIZATION

Enantiomers of amino acids and peptides were derivatized with a fluore scent chiral reagent, 4-(3-isothiocyanatopyrrolidin-1-yl)-7-nitro-2,1 ,3-benzoxadiazole [R-(-)- or S-(+)-NBD-PyNCS] and the resulting diaste reomeric derivatives separated by capillary electrophoresis (CE). The CE running buffer consisted of 25 mM acetate buffer (pH 4) and 10 mM o f the nonionic surfactant Triton X-100. The excitation maximum of NBD- PyNCS at 480 nm matches the major Ar-ion emission line at 488 nm allow ing sensitive laser-induced fluorescence detection with limits of dete ction around 50 nM. D-Proline and D-aspartate spiked (at 10(-4) M and 10(-5) M concentrations, respectively) into complex biological matrice s (rabbit serum and homogenate of Aplysia californica buccal ganglion) are detected without matrix interferences. This method has also been applied to the determination of D- and L-amino acid residues in peptid es after acid hydrolysis. Results from the chiral analysis of the natu rally-occurring peptide, gramicidin D, are shown. (C) 1998 Elsevier Sc ience B.V.