PHENYLGLYOXAL AND GLYOXAL AS FLUOROGENIC REAGENTS SELECTIVE FOR N-TERMINAL TRYPTOPHAN-CONTAINING PEPTIDES

Methods are described for the determination of N-terminal tryptophan-containing peptides in which phenylglyoxal and glyoxal are used as fluorogenic reagents. Phenylglyoxal and glyoxal react selectively with the peptides when heated in a strongly acidic medium in the presence of potassium hexacyanoferrate(III) and in a moderately acidic medium, respectively, at 100-degrees-C for 30 min to produce fluorescence. The detection limits of N-terminal tryptophan-containing small peptides tested are 118-165 pmol ml-1 in the reaction mixtures. The reaction mixture of tryptophulalanine, a model peptide, with glyoxal afforded a single peak when separated by reversed-phase liquid chromatography whereas that with phenylglyoxal gave several peaks.