Figure 3. Efficiency of electron extraction for three quinone derivatives in the WT strain using light-induced absorbance changes of P₇₀₀.

(a) P₇₀₀ reduction ratio as a function of exogenous quinone concentration (mean±s.d.; n=4). P₇₀₀ redox states were estimated from the absorbance changes at 705−730 nm. The P₇₀₀ reduction ratio was calculated as 1 minus the oxidation level reached after a 10 s illumination (26 μmol photons m⁻² s⁻¹) over the level of full P₇₀₀⁺ oxidation after a saturating light pulse. Decreases in the P₇₀₀ reduction ratio indicate a reduced electron flux towards P₇₀₀⁺ in the presence of exogenous quinones. (b) P₇₀₀ reduction ratio as a function of exogenous quinone concentration in the presence of 10 μM DCMU (mean±s.d.; n=3). (c,d) P₇₀₀ reduction rate (k_red), normalized to the rate measured in the absence of quinones (k_red(0)), as a function of exogenous quinone concentration, derived from the data of (a,b), respectively. The normalized k_red/k_red(0) ratio is particularly useful to compare strains or conditions that have different basal levels of P₇₀₀ reduction ratio, as seen here after DCMU treatment.