Photoregulated fluxional fluorophores for live-cell super-resolution microscopy with no apparent photobleaching

Photoswitchable mols. have multiple applications in the phys. and life sciences because their properties can be modulated with light. Fluxional mols., which undergo rapid degenerate rearrangements in the electronic ground state, also exhibit switching behavior. The stochastic nature of fluxional switching, however, has hampered its application in the development of functional mols. and materials. Here we combine photoswitching and fluxionality to develop a fluorophore that enables very long (\textgreater30 min) time-lapse single-mol. localization microscopy in living cells with minimal phototoxicity and no apparent photobleaching. These long time-lapse expts. allow us to track intracellular organelles with unprecedented spatiotemporal resoln., revealing new information of the three-dimensional compartmentalization of synaptic vesicle trafficking in live human neurons.