Scherbakova, D.M. et al. Nat. Commun. 7, 12405 (2016).

Near-infrared fluorescent proteins (NIR FPs) derived from bacterial phytochromes are useful for a broad range of applications, including multicolor and deep-tissue imaging. Scherbakova et al. developed three monomeric NIR FPs, called miRFPs, that have desirable photophysical properties and perform well in diverse applications. The researchers demonstrate that the spectrally distinct miRFPs, which emit maximally at 670, 703 and 709 nm, respectively, are twofold to fivefold brighter than existing monomeric NIR FPs and have bright signal at endogenous levels of the cofactor biliverdin. To demonstrate their broad applicability, the researchers showed that the miRFPs can perform well in multiple fusions for determining subcellular localization, and that they are useful for structured illumination microscopy. They also used the miRFPs to develop reporters based on bimolecular fluorescence complementation and for in vivo imaging in mice.