Photochemistry and enzymology of photosynthesis. Annual progress report, May 1, 1975--April 30, 1976

Technical Report · Thu Apr 01 04:00:00 EST 1976

DOI:https://doi.org/10.2172/7363259· OSTI ID:7363259

Kok, B.; Fowler, C. F.; Radmer, R. J.; Hardt, H. H.

Work during the reporting period can be separated into four main topics. Highlights include oxygen evolution, proton transport, acid-base induced fluorescence changes, and mass spectrometer studies. Under some conditions we have observed the apparent transition of S/sub 1/ to S/sub 2/ in the dark. Redox titrations showed that this transition has a midpoint potential of 400 mV at pH 7, and a pH dependence of 60 mV per pH unit. The proton uptake and release that apparently accompany the reduction and oxidation of plastoquinone were found to oscillate with a period of two in flashing light. Proton release associated with the O/sub 2/-evolving system was found to oscillate with a period of four in flashing light; however, only one-half of the protons seemed to be liberated in the final O/sub 2/-evolving step. We found that three to four protons per electron were transported from the outside to the inside of the thylakoid, which suggests that at each coupling site one electron transports two protons simultaneously. Further evidence was obtained for a base-induced backflow of electrons to the System II acceptor Q. A subsequent fluorescence transient, which could not be readily rationalized in the context of standard models, was also observed. Using whole algae, we observed that molecular O/sub 2/ directly competes with CO/sub 2/ for photosynthetically generated reducing power via a process unrelated to carbon metabolism. In a study using CO/sub 2/-depleted chloroplasts, we found that bicarbonate was not the immediate source of O/sub 2/ in the bicarbonate-dependent Hill reaction.

• Research Organization: Martin Marietta Labs., Baltimore, Md. (USA)
• OSTI ID: 7363259
• Report Number(s): COO-3326-47
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
550500 -- Metabolism
59 BASIC BIOLOGICAL SCIENCES
ALGAE
BIOMASS
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CHALCOGENIDES
CHARGED-PARTICLE TRANSPORT
CHEMICAL REACTIONS
CHEMISTRY
CRYOGENIC FLUIDS
ELECTRONS
ELEMENTARY PARTICLES
ELEMENTS
ENERGY SOURCES
ENZYMES
FERMIONS
FLUIDS
FLUORESCENCE
LEPTONS
LUMINESCENCE
MASS SPECTROMETERS
MEASURING INSTRUMENTS
METABOLISM
NONMETALS
OXIDES
OXYGEN
OXYGEN COMPOUNDS
PH VALUE
PHOTOCHEMICAL REACTIONS
PHOTOCHEMISTRY
PHOTOSYNTHESIS
PLANTS
PROTON TRANSPORT
RADIATION TRANSPORT
REDOX REACTIONS
RENEWABLE ENERGY SOURCES
SPECTROMETERS
SYNTHESIS