Bromoacetylfluorescein monoaldehyde as a fluorescence turn-on probe for cysteine over homocysteine and glutathione

A novel fluorescent probe possessing the two different functional groups of bromoacetyl ester and aldehyde functionality was designed as a selective chemodosimeter for cysteine (Cys). The initially nonfluorescent bromoacetyl-fluorescein monoaldehyde (3) was rapidly transformed into a strongly fluorescent molecule through the first nucleophilic substitution followed by the subsequent ester bond cleavage reactions by one Cys and the second oxazolidine formation reaction with another Cys. The molecular probe exhibited a rapid response toward Cys over homocysteine or glutathione owing to the favorable kinetic processes with Cys, of which property was successfully applied for live cell imaging with tunicamycin, an inducer of cytosolic Cys.