mScarlet: a bright monomeric red fluorescent protein for cellular imaging

Abstract

We report the engineering of mScarlet, a truly monomeric red uorescent protein with record brightness, quantum yield (70%) and uorescence lifetime (3.9 ns). We developed mScarlet starting with a consensus synthetic template and using improved spectroscopic screening techniques; mScarlets crystal structure reveals a planar and rigidied chromophore. mScarlet outperforms existing red uorescent proteins as a fusion tag, and it is especially useful as a Frster resonance energy transfer (FRET) acceptor in ratiometric imaging.