Development of a new selective labeling method for the target protein of bioactive molecule
by means of turn-ON fluorescence

Target identification of bioactive molecules, which leads to the development of novel classes of drugs with few side effects or the discovery of new druggable proteins, is a vital and still daunting task. To overcome the time-consuming work, we developed a novel affinity labeling method employing a small bifunctional O-nitrobenzoxadiazole (O-NBD) unit having both reactivity and potential fluorescence. O-NBD is usually not fluorescent, but gives the fluorescence in response to existing amino group in protein. This method is not only simple but also powerful for target identification as well as ligand binding-site determination. Moreover, since the target labeling takes place with turn-ON fluorescence, the approach enables a sensitive imaging/detection of target proteins in living cells.