FIGURE 2.

Retinal isomers during the photocycle. A, retinal aldehyde HPLC extraction of different C128T states was performed at the times indicated after a 5-min blue or green illumination. Shown are the data from one single experiment. In the initial dark state, we found a mixture of 22% 13-cis and 78% all-trans, as reported previously. Surprisingly, after the extended illumination, we found significantly increased contributions of cis retinals. The share of 13-cis retinal was, however, dependent on illumination conditions; its maximum was reached 180 s after light. We found a slightly lesser maximal amount after a blue illumination (left column) than after a green illumination (right column). The relaxation into a dark state-like retinal mixture occurred on a very slow timescale that was even slower than the observed spectral alterations. B, extracted retinal isomer mixture before and at different times after the illumination; shown are 13-cis retinal (red), 11-cis retinal (green), 9-cis retinal (cyan), and all-trans retinal (blue). C, time course of the extracted retinal isomer mixture after application of a green (520 nm) instead of a blue illumination. Color codes are the same as described in B.