Photooxidation of Cytochromes c, f, and Plastocyanin by Detergent Treated Chloroplasts

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Abstract
A11 systems were stimulated (up to 6-fold) by viologen dyes and other auto-oxidizable, low potential agents. The photooxidation of ferro cytochrome c was stimulated by catalytic amounts of cytochrome f and plastocyanin (up to 30- and 150-fold, yielding rates up to 1500 and 5000 [mu]moles/mg chlorophyll hour). The quantum yield as well as the light saturated rate were enhanced. Quantum yields approaching unity were observed in long-wave red light. The light-saturated rate was only slightly dependent upon temperature. In the presence of viologen, plastocyanin and cytochrome f were themselves photooxidized with high efficiency and rate. The data are interpreted on the assumptions that only the "long-wave" photoact of photosynthesis is operative, that particle bound cytochrome f mediates the reaction in a charge transfer complex with P700 and that its redox state determines the probability of a photoact''s being successful.