Synthesis and fluorescence properties of intramolecularly quenched fluorogenic p-nitroanilides containing coumarin or quinolinone derivatives as fluorophores

Nine model intramolecularly quenched fluorogenic substrates (IQFS) of the g eneral structure F-Phe-NH-Np, containing coumarin or quinolinone derivative s as fluorophores (F) and the p-nitroanilide group (Np) as quencher, were s ynthesized. The study of the fluorescence properties of the substrates synt hesized and the corresponding fluorophores showed that efficient quenching of fluorescence (>89%) was observed in all cases. The combination of 7-glut arylamido-4-methyl-coumarin (Met-NM-G It-OH) or 7-methoxy-4-coumarylacetic acid (Mca) with the p-nitroanilide group gave the best results (97.2 and 98 .8% quenching, respectively). These fluorophores can be used to convert pep tide p-nitroanilides into IQFS, which, retaining their chromogenic properti es, may be applied in both fluorometric and colorimetric assays.