Accession Number : AD0619224

Title :   PLASTOCYANIN PHOTO-OXIDATION BY DETERGENTTREATED CHLOROPLASTS,

Corporate Author : MARTIN CO BALTIMORE MD RESEARCH INST FOR ADVANCED STUDIES

Personal Author(s) : Kok,Bessel ; Rurainski,Hans J.

Report Date : 16 NOV 1964

Pagination or Media Count : 4

Abstract : The time course was measured of the photo-oxidation of two concentrations of plastocyanin, 70% of which was in the reduced state at the beginning of the experiment. Despite a 4.5-fold concentration difference, the initial rate of photo-oxidation is equal in both cases. However, the time required for the conversion to be half completed is 4.5-fold longer in the case of high substrate concentration. These kinetics closely resemble those reported for cytochrome f and indicate that the rate is proportional to the ratio (plastocyanin) reduced/(plastocyanin) total. Data were also obtained by recording the time courses of plastocyanin photo-oxidation for two light intensities. The saturation rate as well as quantum yield of the process are proportional to the fraction of the substrate in the reduced form. The most reasonable explanation remains that in photosynthesis, plastocyanin and cytochrome f function 'in parallel', both donating to Photosystem I electrons generated in the second, O2-evolving, photo-act. (Extracted)

Descriptors :   (*PHOTOCHEMICAL REACTIONS, ORGANIC PIGMENTS), (*ORGANIC PIGMENTS, PHOTOCHEMICAL REACTIONS), OXIDATION, REACTION KINETICS, CHLOROPHYLLS, PHOTOSYNTHESIS

Distribution Statement : APPROVED FOR PUBLIC RELEASE