A near-infrared fluorescent probe with remarkably large stokes shift for specifical imaging of peroxynitrite fluctuations in Hela cells.

Peroxynitrite (ONOO), an endogenous reactive nitrogen species, plays an important role in maintaining intracellular homeostasis. Abnormal levels of ONOO in cells could cause protein oxidation which is confirmed that related with Alzheimer's diseases, so accurate monitoring of ONOO in cells is crucial. Herein, a novel fluorescent probe (XPC) based on dicyanomethylene-4H-benzothiopyran was developed by regulating its intramolecular charge transfer (ICT) effect to detect ONOO. Once reaction with ONOO, the fluorescence of XPC was turned on and the emission wavelength could reach up to 750 nm. Furthermore, XPC exhibited satisfactory performances for ONOO such as large Stokes shift (200 nm), good sensitivity (Limit of detection = 13 nM), high selectivity to ONOO over other a reactive nitrogen species (RNS)/reactive oxygen species (ROS). More importantly, XPC was successfully applied for monitoring the fluctuations of ONOO in living cells.