Showing papers on "Photosynthetic reaction centre published in 1974"
TL;DR: In this paper, the complete absorption difference spectrum of the primary electron acceptor of Photosystem II has been measured at room temperature in subchloroplast fragments prepared with deoxycholate and the shape and amplitude of the spectrum indicate that the primary reaction involves the reduction of one bound plastoquinone molecule per reaction center to its semiquinone anion.
262 citations
TL;DR: Isolated photosynthetic reaction center from the bacterium Rhodospirillum rubrum was extracted with acetone-methanol and was proposed to contain 4 moles of bacteriochlorophyll, 2 mole of bacteriopheophytin, and 1 mole of spirilloxanthin per equivalent of P870.
129 citations
TL;DR: EPR lineshapes of the triplet signals show almost complete spin polarization demonstrating that inter-system crossing is a highly selective process.
96 citations
TL;DR: The P 680 absorption difference spectrum and electron spin resonance could be explained by the oxidation of a chlorophyll a dimer, which may be the same as that of the difference spectrum of P680 if the bleaching at 700 nm is attributed to a band shift.
96 citations
TL;DR: The kinetics of fluorescence yield in Chlorella pyrenoidosa and spinach chloroplasts were studied and it was suggested that a fast fluorescence component is only present in organisms with intact O2-evolving system, whereas a slow rise predominantly occurs in organism with the watersplitting system irreversibly inhibited by hydroxylamine.
76 citations
TL;DR: The fluorescence-induction phenomena of the Photosystem-II particles have been correlated with their photochemical properties in the presence of secondary electron acceptors and (or) donors which further confirm the PhotosSystem-II character of the particle.
63 citations
TL;DR: It is shown that o -phenanthroline binds specifically to the reaction center protein and when so bound inhibits the transfer of electrons from primary to secondary acceptors.
59 citations
TL;DR: The molecular details for the primary reaction in photosynthesis are deduced from several recent critical experimental observations and a symmetrical structure is proposed for the basic unit of the reaction center in plant photosynthesis.
Abstract: In this paper, the molecular details for the primary reaction in photosynthesis are deduced from several recent critical experimental observations. A symmetrical structure is proposed for the basic unit of the reaction center in plant photosynthesis. A mathematical consequence of the symmetrical arrangement is the creation of an anomalously long-lived trap state, which makes possible the summation of a reaction-center triplet excitation and an antenna chlorophyll singlet excitation to bring the photoactive chlorophylls to a charge-transfer state prior to entering into a primary photochemical reaction.
54 citations
TL;DR: Using laser flash excitation the light saturation curve of the triplet signal has been compared with that of the free-radical formation due to photooxidation of P870 under identical optical conditions and shows that the quantum yield of triplet formation is nearly the same as the photochemical bleaching of bacteriochlorophyll.
52 citations
TL;DR: Results indicate that below 150 °K three types of reaction centers of Photosystem 1 occur, and Ferredoxin is the only electron acceptor, but the rates of the back reaction of reduced ferredoxin with oxidized P700 are different for each type of reaction center.
51 citations
TL;DR: It is concluded that iodination results in the introduction of iodine into the Photosystem II reaction center pigment-protein complex and thereby introduces a new quenching, and is in agreement with previously published schemes which suggest that Photos System II mediated electron transport traverses the membrane.
TL;DR: It is proposed that reaction-center components are preferentially assembled into the membrane during the early period of photosynthetic membrane development.
TL;DR: The restoration by silicotungstic acid of the reversible light-induced pH rise mediated by pyocyanine in EDTA-treated chloroplasts corresponds to an irreversible fixation of the acid and partly restores ferricyanide reduction and O2 evolution in chloroplast suspensions supplemented with DCMU.
TL;DR: Using the technique of flash photolysis — electron spin resonance (FPESR), it is confirmed that a portion of the ESR Signal I of Photosystem I in green-plant photosynthesis responds reversibly to light at low temperatures.
TL;DR: It was unable to definitely associate any of the thermoluminescence peaks with delayed light emitted during a particular time-range of dark decay, but three distinct glow peaks were observed, suggesting that quantum conversion at Reaction Center II may involve three different types of energy storage with differing stabilization energies.
TL;DR: The ability of bicarbonate ion (HCO3-) to stimulate photosynthetic oxygen evolution in maize chloroplast fragments exposed to continuous light depends on light intensity as discussed by the authors.
Abstract: The ability of bicarbonate ion (HCO3-) to stimulate photosynthetic oxygen evolution in maize chloroplast fragments exposed to continuous light depends on light intensity. Stimulation by HCO3- is less at low intensities. In HCO3--depleted chloroplasts exposed to brief saturating light flashes, period 4 oscillations (in O2 yield per flash) are damped within three cycles. Readdition of HCO3- to these preparations restores the oscillatory pattern to higher flash numbers, indicating that HCO3- reduces the probability of “misses” in the photosystem II reaction center. The rate of the dark relaxation reaction Sn′ → Sn+1 (where S refers to the oxidation state of the oxygen-evolving mechanism and n = 0, 1, or 2), after a photoact in the photosystem II reaction center, is retarded in HCO3--depleted chloroplasts compared to the rate for this reaction in depleted chloroplasts to which HCO3- has been resupplied. However, the final oxygen-evolving reaction after the accumulation of four positive charges appears to be independent of HCO3-. Bicarbonate has no effect on the dark deactivation of the higher oxidation states (S2 and S3) of the positive charge-accumulating system. We propose two alternate ways in which the kinetic model of oxygen evolution developed by Kok et al. [(1970) Photochem. Photobiol. 11, 457-475] can be extended to include the action of HCO3-.
TL;DR: In this article, it was shown that low concentrations of the plastoquinone antagonist dibromothymoquinones partially inhibit the Hill reaction and completely cancels the O 2 burst, a purely System II-dependent phenomenon.
TL;DR: A mutant, O1, of Rhodopseudomonas spheroides has been prepared that is not capable of bacteriochlorophyll synthesis, but excretes pigments spectroscopically similar to green plant chlorophylls, suggesting that a cyclic electron flow system had been reconstituted.
TL;DR: Another mutant, strain 71-20 apparently has functional reaction centers, yet it does not grow anaerobically in the light for unknown reasons, and three of the mutants form light harvesting but not reaction-center bacteriochlorophyll; their membranes lack proteins 10 and 11, though proteins 9 and 15 are detectable.
TL;DR: Intracytoplasmic membranes of wild type strain 37 b 4 and mutant strains A1a car-bchl-, A1A car- bchl+ of Rhodopseudomonas capsulata were isolated and reaction center particles were found to be enriched in reaction center bacteriochlorophyll.
Abstract: Intracytoplasmic membranes of wild type strain 37 b 4 and mutant strains A1a car-bchl-, A1a car-bchl+ ofRhodopseudomonas capsulata were isolated. The membrane proteins were solubilized and separated by polyacrylamide gel electrophoresis (methods of Takayamaet al., 1964; Weber and Osborn, 1969). The band patterns were compared with each other. From the strain A1a car-bchl+ reaction center particles were isolated by treatment of membrane with Triton X-100 followed by sucrose density gradient centrifugation. The reaction center particles were found to be enriched in reaction center bacteriochlorophyll. This pigment shows a reversible bleaching at 855 nm and a blue shift at 798 nm. The light harvesting bacteriochlorophyll portion of this fraction was 14–22% of the total bacteriochlorophyll content. The three main proteins of the reaction center particles amount to about 80% of the total protein of the particles. The molecular weights of the main proteins were estimated to be 32000, 27500 and 22500 daltons.
TL;DR: A comparison between Olive Necrotic (ON) 8147 mutant and normal Zea mays L. chloroplasts revealed that the mutant had: (1) a lowered ratio of pigments (chlorophylls (Chl) and carotenoids) to proteins, (2) a higher ratio of pigment system I to II (based on the ratios of Ch a to b, pigment system II to II emission at 298 and 77° K, and the variable to constant fluorescence), and (3) higher saturation rate of electron flow (dichlor
TL;DR: In this article, the electron transport dependent diazonium incorporation reflects a conformational change (unspecified at this time) in membrane components, which is localized after the site of DCMU inhibition but before plastoquinone.
Abstract: Various partial redox reactions involved in photosynthetic electron transport were studied in relation to the electron transport dependent incorporation of the water soluble chemical modifier, diazonium benzene sulfonic acid (DABS)* into chloroplast membranes. This electron transport dependent diazonium incorporation reflects a conformational change (unspecified at this time) in membrane components. The redox reaction(s) responsible for this conformational change was shown to be localized after the site of DCMU inhibition but before plastoquinone by the following evidence:
1.
Electron transport from water to lipophilic “Class III” electron acceptors such as dimethyl benzoquinone and high concentrations of dibromothymoquinone potentiate the extra DABS binding to the membranes. These compounds are reduced prior to or at the plastoquinone site.
2.
Electron transfer from water to silicomolybdate plus ferricyanide, a DCMU insensitive reaction, does not result in the incremental diazonium binding.
3.
Photosystem I cyclic electron flow mediated by menadione (anaerobic), which requires participation of plastoquinone does not give the extra diazonium binding.
TL;DR: It is proposed that two light reactions occur at the reaction center of Photosystem-II (RC-II) at low temperature.
TL;DR: It is concluded that the isolated 310 material acts on the reducing side of Photosystem I at or near the site of reduction of ferred toxin and competes with ferredoxin for the reducing power generated by the photosynthetic reaction center.
Journal Article•
TL;DR: In this article, the reaction center of photosystem-2 was studied in spinach chloroplasts, by detection of C-550 and of oxidized cytochrome b559 (using differential absorption spectroscopy, at −196 °C).
TL;DR: Results are consistent with the hypothesis that illumination generates a reaction initiator which is fairly stable in methanol but decays with a half-life of about 4.5 min in reaction center particles after illumination ceases.