A fluorescent sensor bearing nitroolefin moiety for the detection of thiols and its biological imaging

A fluorescein-based sensor bearing nitroolefin moiety for the detection of thiols was prepared. Upon addition of thiols, such as cysteine (Cys), homocysteine (Hcy) and glutathione, the solution containing sensor showed an increase of absorption intensity at 497 nm with a slight blue-shift as well as the enhancement in fluorescence intensity at 520 nm. The fluorescence enhancement and absorption change are attributed to the Michael addition of thiols to the double bond of nitroolefin moiety in sensor. The probe displays a fast response to Cys with the rate constant (k _obs) of 2.3 min ^-1 and the detection limit to Cys was evaluated to be 0.2 μM. The confocal microscopy experiments demonstrate that this sensor is potential for the imaging of thiols in living cells.