Song, W. et al. J. Am. Chem. Soc. 136, 1198–1201 (2014).

Strack, R.L. et al. Nat. Methods 10, 1219–1224 (2013).

The RNA aptamers Spinach and its recently improved variant Spinach2 (Strack et al., 2013) can be fused to an RNA of interest, allowing RNA tracking experiments to be performed in living cells. Spinach2 lights up RNA by binding the fluorogenic small molecule (Z)-4-(3,5-difluoro-4-hydroxybenzylidene)-1,2-dimethyl-1H-imidazol-5(4H)-one (DFHBI) and activating its fluorescence. However, DFHBI does not have ideal spectral characteristics: most microscopes have filters that are optimized for imaging GFP or fluorescein isothiocyanate. In order to adapt the spectral characteristics of Spinach2 for common microscope filters tuned for GFP or YFP, Song et al. present novel DFHBI chemical derivatives that serve as 'plug-and-play' fluorophores for Spinach2, allowing researchers to choose the optimal fluorophore for their experimental needs or swap out fluorophores with ease.