Photoswitchable PM 8

Photoswitchable PM8 is a fluorescent probe used for super-resolution imaging of the plasma membrane. Photoswitchable PM8 functions through a light-induced Z/E isomerization mechanism: in the hydrophobic cell membrane environment, the Z isomer forms a planar intramolecular charge transfer state stabilized by an intramolecular hydrogen bond, which restricts conformational freedom, reduces nonradiative decay, and produces bright fluorescence; in contrast, the E isomer lacks this hydrogen bond, has increased conformational freedom, and exhibits a fluorescence-quenched state. The fluorescence of Photoswitchable PM8 can be switched "on/off" by visible light: activation with 405 nm light forms the fluorescent Z isomer, and switching with 561 nm light converts it to the nonfluorescent E isomer. In the membrane environment, Photoswitchable PM8 enables single-molecule localization for super-resolution imaging. Due to solvent-induced quenching and aggregation, Photoswitchable PM8 has negligible fluorescence in aqueous solution, but upon binding to the hydrophobic membrane environment it produces bright fluorescence, enabling high signal-to-noise ratio imaging without washing .