Figure 6. Time dependence of EPR signal intensity of the EMPO-OOH adduct measured at pH 4.5 in spinach PSII membrane particles in the presence of PQs with different side-chain length.

PSII membrane particles were illuminated with white light (900 μE·m⁻²·s⁻¹) in the presence of 25 mM EMPO, 100 μM desferal, 150 μg of chl·ml⁻¹ and 40 mM acetate buffer (pH 4.5). PQs at 33 μM were added before illumination. r.u., relative units.