Protection of the Isolated Photosystem II Reaction Centre Against Photodamage by Removing Oxygen or Adding Silicomolybdate
The isolated photosystem II reaction centre or so called Dl/D2/cyt b559 complex (1,2) which binds 4 chlorophylls (Chl), 2 pheophytins (Phe), 1 cytochrome b559 (cyt b559) and 1 β-carotene (3) can perform the primary charge separation between P680 and Phe (1–5). However PSII reaction centres isolated in Triton X-100 are very labile (6), especially in the light where a selective bleach indicative of the destruction of P680 is induced (5). Consequent loss of photochemical activity has also been detected (5,7). Here we have investigated the effect silicomolybdate (SiMo) and oxygen on the stability of the isolated PSII reaction centre in the light by absorption and circular dichroism (CD) spectroscopy. Reaction centres were stabilised by exchange into dodecylmaltoside. Under anaerobic conditions, we are able to obtain a reversible light-induced CD change which correlates with the accumulation of P680+.
KeywordsReaction Centre Circular Dichroism Circular Dichroism Spectrum Light Treatment Cytochrome B559
- Cyt b559
Unable to display preview. Download preview PDF.