Single-Molecule Photoswitching Enables High-Resolution Optical Imaging

Fluorescence imaging of biological systems with spatial resolution beyond diffraction limit is of intensive interests. Recently, it has been discovered that by stochastically photoswitching fluorophores on and off, the diffraction limit can be circumvented in far-field optical imaging. Here we present a small photoswitching dye, spiropyran derivatives with the desired characteristics as the excellent photoswitchable molecular fluorophores.[3] Using such a fluorophore, we have achieved photoactuated unimolecular logical switching attained reconstruction (PULSAR) microscopy, with resolution down to 10-40 nm, far beyond the diffraction limit. Spiropyran requires no special treatment to cells and can be readily modified using chemical functional groups for specific targeting.