BGF fluorogenic ligands for SNAP-tag S sizeBGF series fluorogenic ligands are non emitting molecular rotors in free form, however, they exibit bright, rainbow fluorescence when bind to the self labeling SNAP tag and conformational locked. The palette of SNAP tag mimics of fl uorescent proteins (SmFPs) thus generated possess bright, rapidly inducible fluorescence ranging from cyan to infrared. SmFPs are integral chemical genetic entities based on the same fluorogenic principle as Fluorescent