Fig. 1: Sample preparation and characterization of the PSI-LHCI-LHCII supercomplex from C. reinhardtii.

a, b Low temperature (77 K) fluorescence emission spectra of C. reinhardtii cell (a) and thylakoid (b) locked in state 1 (black line) and state 2 (red line). The excitation wavelength was 436 nm and all spectra were normalized to the emission value at 688 nm. c Separation of PSI-LHCI-LHCII supercomplex by sucrose density gradient (SDG) centrifugation from cells in state 1 and state 2. d Size-exclusion chromatographic elution profiles of the PSI-LHCI and PSI-LHCI-LHCII fractions isolated by SDG from the state 2 cell. Elution was performed with a Superose 6 Increase 10/300 GL column (flow rate of 100 μl min⁻¹) at 4 °C and monitored by absorption at 280 nm. e Room-temperature absorption spectra of the PSI-LHCI and PSI-LHCI-LHCII obtained from size-exclusion chromatography. The spectra were normalized to the maximum in the red region. The PSI-LHCI-LHCII supercomplex showed higher peaks at 470 nm and 650 nm (indicated by bars), indicating that this fraction contains higher Chl b content (from LHCII) than the PSI-LHCI complex. f Low temperature (77 K) fluorescence emission spectra of PSI-LHCI and PSI-LHCI-LHCII after size-exclusion chromatography upon excitation of Chl a at 436 nm. The spectra are normalized to the maximum of the emission peaks. Both two samples show the typical emission peaks of PSI-LHCI in red region, but the PSI-LHCI-LHCII has a small shoulder at 680 nm (indicated by bar).