Development and characterization of a unique photoactivatable label

Here a new fluorescent protein, IrisFP, is introduced, incorporating three different photoactivation pathways: irreversible green-to-red photoconversion, and reversible bright-dark photoswitching in both green and red states. The combination of these pathways enables superresolution pulse-chase experiments. A monomeric version of the protein is demonstrated for improved live-cell studies, and a detailed photophysical characterization of an analogue is presented.