Wikipedia
Dronpa
Dronpa is a reversibly switchable photoactivatable fluorescent protein that is 2.5 times as bright as EGFP. Dronpa gets switched off by strong illumination with 488 nm (blue) light and this can be reversed by weak 405 nm UV light. A single dronpa molecule can be switched on and off over 100 times. It has an excitation peak at 503 nm and an emission peak at 518 nm.