Fast fluorescence photoswitching in a bodipy-oxazine dyad with excellent fatigue resistance

We synthesized a photoswitchable fluorescent probe incorporating a BODIPY fluorophore and an oxazine photochrome within the same molecular skeleton. The selective excitation of the BODIPY component at visible wavelengths is accompanied by the emission of light in the form of fluorescence. However, the illumination of the sample at ultraviolet wavelengths opens reversibly the oxazine ring and activates the intramolecular transfer of energy from the fluorophore to the photochrome with concomitant fluorescence quenching. As a result, the emission of this fluorophore-photochrome dyad can be modulated on a microsecond time scale for hundreds of switching cycles, relying on the interplay of two exciting beams. Our operating principles for fast fluorescence photoswitching with excellent fatigue resistance can lead to the development of valuable probes for the super-resolution imaging of biological samples.