Far-field fluorescence nanoscopy is a family of methods that has revolutionized biological imaging by providing sub-diffraction spatial resolution while keeping the low invasiveness of visible light interrogation. Making use of on-off switching of molecular emission, these methods break any fundamental limitation to the achievable spatial resolution. In practice, however, the resolution is limited by the total number of excitation-emission or on-off cycles that a molecule can perform or withstand. Under biological conditions, the lateral resolution is typically limited to about 20 – 50 nm. Axial resolution is typically worse, in the range of 60 – 120 nm. Resolving supramolecular protein structures, as well as the spatial organization of protein-protein interactions requires another push to the resolution to get into sub-10 nm regime, which is the typical size of structural proteins and complexes.
In this lecure, I will present three recent advances from our lab that enable biological imaging with sub-10 nm resolution. First, a new and simpler implementation of MINFLUX1 will be described. Second, a successful combination of STED-FRET will be shown, which is able to super-resolve biomolecular direct interactions. Finally, a TIRF nanoscopy based on DNA-PAINT that can deliver sub-10 nm in three dimensions, and that can be implemented on any wide-field single molecule fluorescence microscope, will be presented.
(1) Balzarotti, F. et al. Science 355 (2017) 606–612.