Yang, S.K. et al. Nat. Chem. 5, 692–697 (2013).

Small-molecule fluorophores are invaluable tools for investigating biological processes, in particular for single-molecule studies. But such studies are plagued by fluorophore blinking and photobleaching—which are, respectively, temporary and permanent suspension of light emission. A promising group of reagents, the so-called Keio fluors, based on a BODIPY (boron-dipyrromethene) scaffold, have very high photostability and reduced blinking compared to commonly used fluorophores, but Keio fluors are not water-soluble, precluding their practical use in biological applications. Yang et al. modified the Keio fluor scaffold with a large, water-soluble polyglycerol dendrimer (PGD) and showed that the reagent maintained long and stable fluorescence emission. This PGD-BODIPY probe appears promising for single-molecule imaging applications.