Fig. 1: Structure and photoswitching scheme of rsEGFP2.

a Three-dimensional structure showing an 11-stranded β-barrel embedding a chromophore held by a central α-helix. b The chromophore of rsEGFP2 in its fluorescent on-state (bottom) absorbs at 479 nm (laser 488 nm) and emits at 503 nm. Isomerization competes with fluorescence and leads the chromophore to its non-fluorescent off-state, which absorbs at 403 nm (laser 400 nm) and ultimately isomerizes back to the initial on-state. Flashes and arrows represent the color of each actinic wavelength. The width of arrows is representative of the efficiency of each isomerization.