A fluorescent probe for the discrimination between Cys and GSH
Fluorescent probe RTP was rationally designed and synthesized to differentially detect cysteine (Cys) and glutathione (GSH) in different channels. RTP was constructed by incorporating a nitrothiophenyl receptor to a rhodamine fluorophore. The replacement of the receptor by the mercapto group in biothiols forms a weakly fluorescent thioether. The amino group in Cys/Hcy further attacks the thioether through aromatic nucleophilic substitution via a five/six-membered ring to form highly fluorescent red-emitting amino-substituted rhodamine. Moreover, RTP has been successfully used for fluorescence imaging of Cys in living Hela cells.