Video of mKate2 fusions
in living cells.

mKate2 is the next generation of far-red fluorescent protein TagFP635 (mKate) [Shcherbo et al., 2007; Shcherbo et al., 2009]. Possessing fluorescence with excitation/emission maxima at 588 and 633 nm, mKate2 is almost 3-fold brighter than TagFP635 and is 10-fold brighter than mPlum at physiological pH 7.5. Within the optical window optimal for light penetration in living tissues, calculated brightness of mKate2 is at least 2-fold higher compared to any monomeric fluorescent protein reported to date.

mKate2 is characterized by complete and fast chromophore maturation at 37°C with maturation half-time <20 min (versus 40 min for mCherry). It is more photostable under both widefield and confocal illumination than other monomeric far-red proteins, including TagFP635, mRaspberry and mPlum. The high brightness, far-red emission spectrum, excellent pH resistance and photostability, coupled with low toxicity demonstrated in transgenic Xenopus laevis embryos, make mKate2 a superior fluorescent tag for imaging in living tissues.

mKate2 is mainly intended for protein labeling. Its far-red fluorescence allows easy and reliable separation from standard green fluorescent labels in dual-color high-throughput assays.