Sensitization of Chloroplast Reactions. I. Sensitization of Reduction & Oxidation of Cytochrome C by Chloroplasts

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Abstract
Normal photoreduction of cytochrome c by chloroplasts is changed to photo-oxidation by treatment with detergent, by aging or by mild heating. During the transition from 1 action to the other, the long wave limit of photoreduction shifts to shorter wavelengths and either a net reduction or net oxidation can be observed - dependent on wavelength. The effectiveness spectrum of the photoreduction process shows a drop at wavelengths beyond 690 mu. In contrast, the quantum yield of photooxidation rises at long wavelengths. It is concluded that the photooxidation of cytochrome c is driven exclusively by the 1st (long wave) photoact of photosynthesis. (Spinach chloroplasts and cell-free preparations of the blue-green alga Anacystis nidulans were used in the experiments.).