High-light induced superoxide radical formation in cytochrome b6f complex from Bryopsis corticulans as detected by EPR spectroscopy

The generation of superoxide radical ( O 2 - ) in Cyt b6f of Bryopsis corticulans under high light illumination was studied using electron paramagnetic resonance (EPR) spectroscopy. This could be evidenced by the addition of SOD which specifically reacted with O 2 - . The generation of O 2 - was lost in the absence of oxygen and was found to be suppressed in the presence of NaN3 and be scavenged by extraneous antioxidants such as ascorbate, β-carotene and glutathione which could also scavenged 1 O 2 ∗ . These results indicated that O 2 - which produced under high light illumination in Cyt b6f of B. corticulans might rise from a reaction which 1 O 2 ∗ could participated in. Also the photo-protection mechanism to Cyt b6f complex by antioxidants which might contain in thylakoid was speculated.