Asanuma, H. et al. Angew. Chem. Int. Ed. Engl. doi:10.1002/anie.201411000 (17 February 2015).

Specific labeling of RNAs in living cells can be technically challenging. Asanuma et al. describe a new type of linear probe for fluorescent labeling of target mRNAs that is both highly specific and resistant to nuclease activity. This probe consists of nucleobases built on a D-threoninol scaffold that is modified at multiple positions with perylene moieties. In solution, the probe is linear, and the perylene fluorescence is self-quenched. Upon target binding, however, the probe becomes brightly fluorescent. For use in cells, the probe was also modified with an anthraquinone to further quench the perylene. The researchers tested probes targeting DsRed mRNA in live mammalian cells. They observed blue fluorescence of the probe only in cells expressing DsRed, demonstrating that this probe should enable live-cell imaging of mRNA.