Fig. 5. Blue light excitation of OCP proteins.

a) b) Absorption spectra of recombinant OCP Orange Carotenoid-binding Protein) isolated from transformed Chlamydomonas rein-hardtii strains expressing OCP only (ocp1 a, OCP) or both BKT (β-carotene ketolase) and OCP (ocp1-bkt1 b, OCP-BKT). Absorption spectra are reported as optical density (OD) for dark-adapted protein (black), after 5 min of blue light illumination (blue) and after 20 min of dark recovery (grey). c) d) Absorption spectra integrated in 525–575 nm range (active OCP^R) or 425–475 nm range (inactive OCP^O) reported as arbitrary units (a.u.). e) Absorption spectra of OCP-BKT after subtraction of YFP (Yellow Fluorescent Protein) signal for dark adapted sample and after 5 min of blue light illumination. f) Comparison of OCP^R formation (spectra integrated in 525–575 nm range) for OCP and OCP-BKT. Integrated absorption data reported in c), d) and f) were normalized to 1 in the case of 525–572 nm absorption of dark-adapted samples (time 0). Error bars are reported as standard deviation in c), d) and f) for dark adapted samples, after the blue light treatment and after dark recovery (n = 3).