Fig. 6.

Sub-ps effects of photon absorption on retinal. a Close-up of the retinal (purple sticks) in the dark-unrestrained state, as well as at 0.24, 0.49, 0.74 and 1 ps. Distortions from the initial planarity of the retinal occur within 0.24 ps and evolve further in time, especially at the Schiff base bond, at the C13=C14 bond and at the C10-C11 bond, while the C10 and C14 atoms move in opposite directions (red arrows, a blue arrow marks the pivot point) away and towards Tyr185 (shown as sticks), respectively. Minor torsion occurs also at C8. The electron density maps around the retinal (refined for the dark state, 15% extrapolated for the other panels) are contoured at 1.0σ. At 1 ps, the density for the C13=C14 bond is only visible at lower contour levels. b, c, The torsion angles between the β-ionone ring and the beginning (C18-C5=C6-C7 torsion angle, b) and end (C18-C5-C13-C20 torsion angle, c) of the polyene chain are plotted in time. The oscillatory modulation of the angles with frequencies of 119 ± -9 cm⁻¹ (b) and 93 ± 14 cm⁻¹ (c) further visualize the twisting of the entire retinal. The error bars were derived as described in the Supplementary Methods. Source data are provided for Fig. 6b, c as a Source Data file