Simultaneous fluorescence sensing of Cys and GSH from different emission channels.

A chlorinated coumarin-hemicyanine dye with three potential reaction sites was exploited as fluorescent probe for biothiols. The Cys-induced substitution-rearrangement-cyclization, Hcy-induced substitution-rearrangement, and GSH-induced substitution-cyclizatioin cascades lead to the corresponding amino-coumarin, amino-coumarin-hemicyanine, thiol-coumarin with distinct photophysical properties, enabling Cys and GSH to be selectively detected from different emission channels at two different excitation wavelengths.