Uncoupling effect of lipid peroxidation in spinach thylakoids exposed to peroxyl radicals generated by 2,2?-azobis (2-amidinopropane) dihydrochloride

In this study, we characterized how lipid peroxidation alters the functionality of spinach thylakoids exposed to peroxyl radicals generated by azo compound 2,2-azobis(2-amidinopropane) dihydrochloride (AAPH). Incubation in presence different concentrations (0 200 mmol·L –1 ) AAPH inhibited formation ?pH (IC 50 ? 1.5 estimated quenching 9-aminoacridine fluorescence (Q9-AA). The Q9-AA inhibition was correlated (R 2 = 0.98) extent determined accumulation thiobarbituric acid reactive substances. Much higher were required inhibit maximum (Fv/Fm) and effective (?F/Fm?) photochemical efficiencies photosystem II 120 , respectively), indicating that moderate caused uncoupling thylakoids. This confirmed 62% stimulation O uptake rates measured without artificial uncoupler NH 4 Cl when increased from 0 20 reaching similar values Cl. Above AAPH, with declined similarly decrease ?F/Fm?. These results suggest H + -leakiness thylakoid membranes could be one primary effects oxidative stress.