White led light

EPR thylakoid samples were prepared as discussed above at a final concentration of 1.6 mg ml^–1 Chl S. leopoliensis membranes. The flavodoxin samples contained 100 μM deuterated flavodoxin53 (link) in the presence of 0.3 mM DCPIP and 10 mM sodium ascorbate as donors to P700⁺. The samples were placed in quartz EPR tubes, degassed in a nitrogen box, capped and illuminated for 10 s at room temperature with visible light, prior to freezing in liquid N₂. For the low temperature electron transfer experiments, S. leopoliensis native membrane and membrane/Pt-nanoparticle samples were placed in quartz EPR tubes and dark-adapted for 20 min at room temperature prior to freezing in liquid nitrogen. Both samples contained 1.6 mg ml^–1 Chl, 0.3 mM DCPIP and 10 mM sodium ascorbate. cw X-band (9.5 GHz) EPR measurements were carried out with a Bruker ELEXSYS II E500 EPR spectrometer (Bruker Biospin Corp, Rheinstetten, Germany) equipped with a TE102 rectangular EPR resonator (Bruker ER 4102ST) and a helium gas-flow cryostat (ICE Oxford, UK). Temperature control was provided by an ITC (Oxford Instruments, UK). The samples were transferred from liquid nitrogen to the pre-cooled resonator at 10 K. To measure the low temperature light-induced protein activity, X-band EPR spectra were recorded at 10 K shortly after continuous illumination with a white light LED (Thorlabs).