Red fluorescent proteins: chromophore formation and cellular applications

► RFPs emit orange, red, and far-red fluorescence in their final matured states. ► The maturation of a DsRed type chromophore proceeds via a blue-emitting intermediate. ► The photoconversion of a Kaede type RFP occurs via a β-elimination reaction. ► Superior RFPs will be required for use in deep-tissue and whole-body imaging. ► It is possible to design new RFPs with improved photochemical properties.