Fig. 3: Effect of increasing laser power densities on K-intermediate retinal conformation.
Difference electron density maps (Fobs(light)-Fobs(dark), negative density in yellow, positive density in blue, contoured at 3 σ) collected at different laser power densities. The lowest and highest laser power densities are a direct comparison using data collected at SwissFEL (6 ps). The two middle panels were collected at LCLS (10 ps) and SACLA (10 ps), respectively, and are shown for comparison. A distinct peak, not present in the 342 GW/cm2 map, appears above the negative density in the 2493 GW/cm2 map (gray arrow), indicating a second retinal conformation. The models represented are: the refined dark model (dark green); the refined light model (light blue or light green for the model recorded at 342 GW/cm2) and the two structures obtained at the highest laser power density (orange) for comparison. The lower panel shows the refined retinal models and extrapolated density maps (2Fext(light)-Fcalc at 1 σ) for the highest and lowest laser power density collected after femtosecond laser excitation.
