Bright photoactivatable fluorophores for single-molecule imaging

Small molecule fluorophores are important tools for advanced imaging experiments. The development of self-labeling protein tags such as the HaloTag and SNAP-tag has expanded the utility of chemical dyes in live-cell microscopy. We recently described a general method for improving the brightness and photostability of small, cell-permeable fluorophores, resulting in the novel azetidine-containing \"Janelia Fluor\" (JF) dyes. Here, we refine and extend the utility of the JF dyes by synthesizing photoactivatable derivatives that are compatible with live-cell labeling strategies. These compounds retain the superior brightness of the JF dyes once activated, but their facile photoactivation also en