Ultrabright photoactivatable fluorophores created by reductive caging

Sub-diffraction-limit imaging can be achieved by sequential localization of photoactivatable fluorophores, for which the image resolution depends on the number of photons detected per localization. We report a strategy for fluorophore caging that creates photoactivatable probes with high photon yields. Upon photoactivation, these probes can provide 10(4)-10(6) photons per localization and allow imaging of fixed samples with resolutions of several nanometers. This strategy can be applied to many fluorophores across the visible spectrum.