Search results for "Photosystem"
showing 10 items of 103 documents
Cytochrome F as Indicator for the Interaction of the Two Photosystems in the State 1 and State 2
1990
The transition of plants into a State 1 or a State 2 by an excess of PS I or PS II excitation was described by BONAVENTURA and MYERS [1]. Since the time of their investigations fluorometric methods gained increasing importance in analyzing the distribution of energy between the two photosystems [21. It was possible to correlate the altered energy balance to the phosphorylation of LHCII and it’s migration into non-appressed thylakoid membranes [31. However fluorescence measurements can give only indirect evidences that also changes in the activity of the two photosystems are produced by the changed energy distribution. A direct assessment of the photochemical variations during state transiti…
Changes in the Constitution of Thylakoid Membranes in Spruce Needles During an Open‐top Chamber Experiment
1992
The goal of the presented paper was to study the emission effects of natural air pollutants on the protein complexes of the thylakoid membrane. The tests were carried out in the frame of a long-term experiment in which spruce trees kept in open-top chambers with unfiltered ambient-air were compared to spruce trees in chambers with purified-air. The reaction centres of photosystem I (P-700), cytochrome f, cytochrome b-563, cytochrome b-559, as well as the oxidation speed of the antennae chlorophylls were quantified. The concentrations of the cytochromes f and b-563 indicate a marked annual rhythm with decreased concentrations during the summer months. The spruce trees in chambers with ambien…
The concentration of Cytochrome f and P700 in chlorophyll-deficient mutants of Chlorella fusca
1977
The ratio of Chlorophyll: Cytochrome f and of Chlorophyll: P700 (reaction center pigment in photosystem I) is essentially lower in chlorophyll-deficient mutants than in the normal green strain. On a dry weight basis, the mutants have the same or a higher content of redox enzymes than the normal form. The size of the photosynthetic unit of the mutants is 4 to 7 times smaller than that of the normal strains, due mainly to a deficiency of the light-harvesting chlorophyll-protein complex.
Measurements of cytochrome f and P-700 in intact leaves of Sinapis alba grown under high-light and low-light conditions
1978
The oxidation and reduction of cytochrome f and P-700 is measured spectrophotometrically in leaves of low-light and high-light plants. After illumination with red light, an induction phenomenon for cytochrome f oxidation is observed which indicates a regulation of photosystem I activity through energy distribution between the pigment systems by the energy state of the membrane. After far-red excitation the reduction of cytochrome f in the dark is much slower in low-light leaves. This shows that cyclic electron transport is not improved in low-light plants under these conditions. P-700 is oxidized on excitation with far-red light. However, with high intensities of far-red light, P-700 is par…
Comparative Investigations on the Photosynthetic Electron Transport Chain of Spruce (Picea Abies) with Different Degrees of Damage in the Open Air
1988
Several components of the photosynthetic electron transport chain (P-700, cytochrome f, QB-protein) as well as the rate of electron transport and the chlorophyll content of the needles of spruce trees with different degrees of damage were investigated. The investigations were carried out in pair comparison at a location in the Hunsruck (West Germany). The rate of electron transport was determined as photoreduction of 2,6-dichlorophenolindophenol. Significant damage to the electron transport system is shown in the thylakoids of the damaged trees compared to the less severely damaged trees. In the spruce trees with more damage, the rates of electron transport are significantly lower. The inve…
Study of electrostatic potential surface distribution of wild-type plastocyaninSynechocystissolution structure determined by homonuclear NMR
2003
Plastocyanin is a small (∼10 kDa), type I blue copper protein that works as an electron donor to photosystem I from cytochrome f in both chloroplast systems and in some strains of cyanobacteria. Comparative studies of the kinetic mechanisms of plastocyanins in different organisms show that the electron transfer from photosystem I happens by simple collision in cyanobacteria but through a intermediate transition complex in green algae and superior plants. Previous work has proved that this effect cannot be explained by structural variations across the different plastocyanins but it can be explained by differences in the electrostatic potential distribution at the protein surface. In that cas…
Cyclic and noncyclic photophosphorylation during the ontogenesis of high-light and low-light leaves of Sinapis alba.
1981
Noncyclic electron transport to ferricyanide and photophosphorylation as well as the methylviologen mediated aerobic and anaerobic photophosphorylation with dichlorophenolindophenol-ascorbate as the electron donor of photosystem I were measured during the development of high-light and low-light adapted leaves of Sinapis alba. Anaerobic methylviologen-catalyzed phosphorylation is more than twice as high as aerobic phosphorylation. The difference between the rates of aerobic and anaerobic phosphorylation is sensitive to dibromothymoquinone. Thus, under anaerobic conditions, methylviologen mediates a cyclic phosphorylation including plastoquinone. All photochemical activities of high-light chl…
The importance of a highly active and DeltapH-regulated diatoxanthin epoxidase for the regulation of the PS II antenna function in diadinoxanthin cyc…
2005
The present study focuses on the regulation of diatoxanthin (Dtx) epoxidation in the diadinoxanthin (Ddx) cycle containing algae Phaeodactylum tricornutum, Thalassiosira pseudonana, Cyclotella meneghiniana and Prymnesium parvum and its significance for the control of the photosystem II (PS II) antenna function. Our data show that Dtx epoxidase can exhibit extremely high activities when algal cells are transferred from high light (HL) to low light (LL). Under HL conditions, Dtx epoxidation is strongly inhibited by the light-driven proton gradient. Uncoupling of the cells during HL illumination restores the high epoxidation rates observed during LL. In Ddx cycle containing algae, non-photoche…
Biochemical indicators for novel forest decline in spruce
1998
Abstract The impact of air pollution on 24 stands of spruce trees in several regions in Germany was investigated. We looked for evidence of biochemical and physiological change at the level of the photosynthetic thylakoid membranes as well as for changes in the antioxidative system in two year old needles. We observed that, as the chlorophyll content decreases in the needles, the amoung of D1 protein declines far more rapidly in relation to the redox components P700 and cytochrome f. Consequently, the PSII/PSI stoichiometry keeps dropping to pregressively lower, meaning unfavorable, values at the chlorophyll content diminishes. This is particularly the case in the higher elevation character…
Proteomic analysis of the photosystem I light-harvesting antenna in tomato (Lycopersicon esculentum).
2004
Until now, more genes of the light-harvesting antenna of higher-plant photosystem I (PSI) than proteins have been described. To improve our understanding of the composition of light-harvesting complex I (LHCI) of tomato (Lycopersicon esculentum), we combined one- and two-dimensional (1-D and 2-D, respectively) gel electrophoresis with immunoblotting and tandem mass spectrometry (MS/ MS). Separation of PSI with high-resolution 1-D gels allowed separation of five bands attributed to proteins of LHCI. Immunoblotting with monospecific antibodies and MS/MS analysis enabled the correct assignment of the four prominent bands to light-harvesting proteins Lhcal -4. The fifth band was recognized by o…