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Photoinactivation sites of photosystem i in isolated chloroplasts

, : Photoinactivation sites of photosystem i in isolated chloroplasts. Plant & Cell Physiology 27(6): 961-968

Illumination of isolated spinach chloroplasts under aerobic conditions induced photoinactivation of PS I as measured by NADP+ photoreduction with 2,6-dichlorophenolindophenol and ascorbate as electron donors. The iron-sulfur centers X, B, and A also were decreased. The extent of photoinactivation of any of these centers or P700 as single components could not account for the loss of PS I activity. It was correlated, however, with the product of each fraction of the three iron-sulfur centers remaining intact. These results suggest a linear electron transfer sequence of the three centers. Incubation of chloroplasts with xanthine oxidase in the dark also led to decrease of PS I activity as well as of iron-sulfur centers. It is concluded that the main cause of photoinactivation of PS I is the destruction of the iron-sulfur centers by some species of active oxygen produced by illuminated class II chloroplasts.

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Related references

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