نتایج جستجو برای: photosystem
تعداد نتایج: 7100 فیلتر نتایج به سال:
Bala Krishna Kolli, Swati Tiwari and Prasanna Mohanty School of Life Sciences, Jawaharlal Nehru University, New Delhi 110 067, India Z. Naturforsch. 53c, 369-377 (1998); received December 15, 1997 Fluorescence Transients, Photosystem II, Quinones, Spirulina, Ultraviolet-B When Spirulina platensis filaments were exposed to 0.75 mW.m_2.s_1 of ultraviolet-B radi ation (the ultraviolet-B radiation...
The efficiency of oxygenic photosynthesis depends on the presence of core antenna chlorophyll closely associated with the photochemical reaction centers of both photosystem II (PSII) and photosystem I (PSI). Although the number and overall arrangement of these chlorophylls in PSII and PSI differ, structural comparison reveals a cluster of 26 conserved chlorophylls in nearly identical positions ...
As was described previously, an antiserum to polypeptide 11000 inhibited photosynthetic electron transport on the oxygen evolving side of photosystem II. The effect of the antiserum on chloroplasts from two tobacco mutants also clearly showed that the inhibition site is on the photosystem II-side of the electron transport chain. One of the two tobacco mutants lacks the oxygen evolving capacity ...
Long-term imbalance in light absorption and electron transport by photosystem I (PSI) and photosystem II (PSII) in chloroplasts brings about changes in the composition, structure, and function of thylakoid membranes. The response entails adjustment in the photosystem ratio, which is optimized to help the plant retain a high quantum efficiency of photosynthesis (W.S. Chow, A. Melis, J.M. Anderso...
In acclimation to changing light environments, photosynthetic organisms modulate the ratio of two photosynthetic reaction centers (photosystem I [PSI] and photosystem II). One mutant, which could not modulate photosystem stoichiometry upon the shift to high light, was isolated from mutants created by random transposon mutagenesis. Measurements of chlorophyll fluorescence and analysis of the rea...
A photosynthetic organism is subjected to photo-oxidative stress when more light energy is absorbed than is used in photosynthesis. In the light, highly reactive singlet oxygen can be produced via triplet chlorophyll formation in the reaction centre of photosystem II and in the antenna system. In the antenna, triplet chlorophyll is produced directly by excited singlet chlorophyll, while in the ...
The dioxygen we breathe is formed by light-induced oxidation of water in photosystem II. O2 formation takes place at a catalytic manganese cluster within milliseconds after the photosystem II reaction centre is excited by three single-turnover flashes. Here we present combined X-ray emission spectra and diffraction data of 2-flash (2F) and 3-flash (3F) photosystem II samples, and of a transient...
In the red alga Porphyra perforata, the level of chlorophyll fluorescence in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) decreased during illumination of the thallus. The results showed that: (a) this decay was related to the photooxidative activity of photosystem I; (b) Q, the primary electron acceptor of photosystem II, became oxidized during the decay of the fluorescence; ...
Abbreviations: a*PSII, optical cross section for photosys factor; Chl a, chlorophyll a; Ci, inorganic carbon; CO2, carb anhydrase; ETR, electron transport rate; FIRe, fluorescence Fm′ , light-adapted maximum fluorescence; Fv/Fm, maximum tochemistry in photosystem II; HCO3, bicarbonate; HEPE according to Lavergne and Trissl (1995); MIMS, membran enine dinucleotide phosphate; NaHCO3, sodium bicar...
To understand whether fusions of thylakoid membranes from the parental chloroplasts occurred during zygote formation in Chlamydomonas reinhardtii, we performed an ultrastructural analysis of the zygotes produced by crossing mutants lacking photosystem I or II protein complexes, in the absence of de novo chloroplast protein synthesis. Thylakoid membranes from each parent could be distinguished o...
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