A FLUOROGENIC REAGENT FOR AMINO-ACIDS IN LIQUID-CHROMATOGRAPHY, 4-(2-CYANOISOINDOLYL)PHENYLISOTHIOCYANATE

A newly synthesized Edman-type fluorogenic reagent, 4-(2-cyanoisoindolyl)phenylisothiocyanat reacted with 20 tested amino acids in a basic medium to produce the corresponding thiocarbamoyl derivatives. The derivatives were converted in an acidic medium to the thiohydantoin derivatives which were separated by reversed-phase chromatography and detected by fluorimetry. The on-column detection limits for amino acids (S/N=3) were on the subpicomole level. Dipeptides, Leu-Ala and Ala-Gly also reacted with the reagent to produce the thiocarbamoyl derivatives which were cleft in an acidic medium at the peptide bonds to produce the thiohydantoin derivatives of the N-terminal amino acids.