Bajar et al. Sci. Rep. 6, 20889 (2016).

Fluorescent proteins are widely used in biology. Two very important photophysical properties of these proteins are their brightness and their photostability, which influence the signal-to-noise ratio and duration of imaging experiments. Bajar et al. developed improved monomeric fluorescent proteins for enhanced protein labeling and molecular sensing by Förster resonance energy transfer (FRET). They subjected the green fluorescent protein mClover and the red fluorescent protein mRuby2 to mutagenesis and then screened for brightness and photostability. The resulting mClover2 was 60% more photostable than mClover, and mRuby3 was 200% more photostable and 35% brighter than mRuby2, making it the brightest and most photostable monomeric red fluorescent protein. The authors demonstrated that mClover2 and mRuby3 perform well as fusions in mammalian cells and are an efficient FRET pair.