A molecular logic gate enables super-resolved imaging of intracellular lipid droplets

Photoactivatable dyes enable single-mol. imaging in biol. Despite progress in the development of new fluorophores and labeling strategies, many cellular compartments remain difficult to image beyond the limit of diffraction in living cells. For example, lipid droplets, which are organelles that contain mostly neutral lipids, have eluded single-mol. imaging. To visualize these challenging subcellular targets, it is necessary to develop new fluorescent mol. devices beyond simple on/off switches. Here, we report a fluorogenic mol. logic gate that can be used to image single mols. assocd. with lipid droplets with excellent specificity. This probe requires the subsequent action of light, a lipophilic environment and a competent nucleophile to produce a fluorescent product. The combination of these requirements results in a probe that can be used to image the boundary of lipid droplets in three dimensions with resolns. beyond the limit of diffraction. Moreover, this probe enables single-mol. tracking of lipids within and between droplets in living cells.