Hydroxyl radicals are not the protagonists of UV-B-induced damage in isolated thylakoid membranes

2007 ◽  
Vol 34 (12) ◽  
pp. 1112 ◽  
Author(s):  
Iva Šnyrychová ◽  
Péter B. Kós ◽  
Éva Hideg
Keyword(s):  
Hydrogen Peroxide ◽  
Electron Transport ◽  
Hydroxyl Radicals ◽  
Early Stage ◽  
D1 Protein ◽  
Photosynthetic Electron Transport ◽  
Thylakoid Membranes ◽  
Oxygen Species ◽  
Free Hydrogen ◽  
By Products

The production of reactive oxygen species (ROS) was studied in isolated thylakoid membranes exposed to 312 nm UV-B irradiation. Hydroxyl radicals (•OH) and hydrogen peroxide were measured directly, using a newly developed method based on hydroxylation of terephthalic acid and the homovanillic acid/peroxidase assay, respectively. At the early stage of UV-B stress (doses lower than 2.0 J cm–2), •OH were derived from superoxide radicals via hydrogen peroxide. Production of these ROS was dependent on photosynthetic electron transport and was not exclusive to UV-B. Both ROS were found in samples exposed to the same doses of PAR, suggesting that the observed ROS are by-products of the UV-B-driven electron transport rather than specific initiators of the UV-B-induced damage. After longer exposure of thylakoids to UV-B, leading to the inactivation of PSII centres, a small amount of •OH was still observed in thylakoids, even though no free hydrogen peroxide was detected. At this late stage of UV-B stress, •OH may also be formed by the direct cleavage of organic peroxides by UV-B. Immunodetection showed that the presence of the observed ROS alone was not sufficient to achieve the degradation of the D1 protein of PSII centres.

Mode of Inhibition of Photosynthetic Electron Transport by Substituted Diphenylethers

1981 ◽  
Vol 36 (9-10) ◽  
pp. 848-852 ◽  
Author(s):  
W. Draber ◽  
H. J. Knops ◽  
A. Trebst
Keyword(s):  
Electron Transport ◽  
Electron Flow ◽  
Photosynthetic Electron Transport ◽  
Thylakoid Membranes ◽  
Photosynthetic Electron Flow ◽  
Spinach Chloroplasts

Abstract Several substituted diphenylethers were found to be effective inhibitors of photosynthetic electron flow in isolated thylakoid membranes from spinach chloroplasts. T heir site of inhibition was localized with artificial acceptor and donor systems. The phenylether of an alkyl substituted nitrophenol is prim arely inhibiting electron flow after plastoquinone function whereas a dinitro-phenylether of a phenyl substituted nitrophenol is inhibiting before plastoquinone function. Therefore certain diphenylethers interfere with plastoquinone function at the oxidation or reduction site, depending on the substitution.

scholarly journals Impact of High Light on Reactive Oxygen Species Production within Photosynthetic Biological Membranes

2015 ◽  
Vol 6 (2) ◽  
pp. 50 ◽  
Author(s):  
Vetoshkina D. V. ◽  
Borisova-Mubarakshina M. M. ◽  
Naydov I. A. ◽  
Kozuleva M. A. ◽  
Ivanov B. N.
Keyword(s):  
Reactive Oxygen Species ◽  
Electron Transport ◽  
Electron Transport Chain ◽  
Reactive Oxygen ◽  
Photosynthetic Electron Transport ◽  
Lipid Phase ◽  
H2o2 Production ◽  
Oxygen Species ◽  
Photosynthetic Electron Transport Chain ◽  
Transport Chain

In this study we describe the mechanisms of reactive oxygen species (ROS) production in the photosynthetic electron transport chain of higher plants chloroplasts under illumination. We implement an improved method for the measurement of hydrogen peroxide (H2O2) production in lipid phase of photosynthetic membranes of chloroplasts. Total rate of H2O2 production and the production within the thylakoid membrane under operation of photosynthetic electron transport chain is evaluated. Obtained data show that even in the presence of an efficient electron acceptor, methyl viologen, an increase in light intensity leads to an increase in H2O2 production mainly within the thylakoid membranes. The role of H2O2 produced within the photosynthetic biological membrane is discussed.

Formation mechanisms of superoxide radical and hydrogen peroxide in chloroplasts, and factors determining the signalling by hydrogen peroxide

2018 ◽  
Vol 45 (2) ◽  
pp. 102 ◽  
Author(s):  
Boris N. Ivanov ◽  
Maria M. Borisova-Mubarakshina ◽  
Marina A. Kozuleva
Keyword(s):  
Hydrogen Peroxide ◽  
Electron Transport ◽  
Thylakoid Membrane ◽  
Electron Transport Chain ◽  
Superoxide Radical ◽  
Photosynthetic Electron Transport ◽  
Formation Mechanisms ◽  
H2o2 Production ◽  
Photosynthetic Electron Transport Chain ◽  
Transport Chain

Reduction of O2 molecule to superoxide radical, O2•−, in the photosynthetic electron transport chain is the first step of hydrogen peroxide, H2O2, production in chloroplasts in the light. The mechanisms of O2 reduction by ferredoxin, by the components of the plastoquinone pool, and by the electron transfer cofactors in PSI are analysed. The data indicating that O2•− and H2O2 can be produced both outside and within thylakoid membrane are presented. The H2O2 production in the chloroplast stroma is described as a result of either dismutation of O2•− or its reduction by stromal reductants. Formation of H2O2 within thylakoid membrane in the reaction of O2•− with plastohydroquinone is examined. The significance of both ways of H2O2 formation for specificity of the signal being sent by photosynthetic electron transport chain to cell adaptation systems is discussed.

Chemical and biochemical aspects of superoxide radicals and related species of activated oxygen

1982 ◽  
Vol 60 (11) ◽  
pp. 1330-1345 ◽  
Author(s):  
Ajit Singh
Keyword(s):  
Hydrogen Peroxide ◽  
Hydroxyl Radicals ◽  
Superoxide Radical ◽  
Superoxide Radicals ◽  
Living Systems ◽  
Biological Processes ◽  
Oxygen Species ◽  
Peroxy Radicals ◽  
Activated Oxygen ◽  
Oxygen Yield

The spectrum of biological processes in which oxygen is used by living systems is quite large, and the products include some damaging species of activated oxygen, particularly the superoxide radical [Formula: see text] and hydrogen peroxide (H2O2). Superoxide radicals and hydrogen peroxide, in turn, can lead to the formation of other damaging species: hydroxyl radicals (∙OH) and singlet oxygen (1O2). Hydroxyl radicals react with organic compounds to give secondary free radicals that, in the presence of oxygen, yield peroxy radicals, peroxides, and hydroperoxides. Formation, interconversion, and reactivity of [Formula: see text] and related activated oxygen species, methods available for their detection, and the basis of their biological toxicity are briefly reviewed.

Regulation of photosystem II by metabolic and environmental factors

1989 ◽  
Vol 323 (1216) ◽  
pp. 269-279 ◽  
Keyword(s):  
Electron Transport ◽  
Higher Plants ◽  
Photosynthetic Electron Transport ◽  
Thylakoid Membranes ◽  
Internal Factors ◽  
Regulatory Processes ◽  
Quenching Analysis ◽  
Intact Chloroplasts ◽  
Rate Of Dissipation

The thylakoid membranes of higher plants possess several mechanisms that control both the distribution and rate of dissipation of absorbed light. These mechanisms, which allow regulation of photosynthetic electron transport in response to alteration in external and internal factors, can be observed as the various processes that quench chlorophyll fluorescence. By using the 'light-doubling techniques’, together with analysis of quenching relaxation, it is possible to assess quantitatively the extents of these regulatory processes and to allow their interrelations to be studied. These techniques can be applied to in vitro systems or to leaves, and can be particularly useful when applied with electron-transport measurements and when models are used to aid interpretation. Results of quenching analysis at different light intensities in isolated thylakoids, intact chloroplasts, protoplasts, algae and leaves of a variety of species are presented.

scholarly journals 367 Scavenging Capacity of Active Oxygen Species in Blackberry

HortScience ◽  
2000 ◽  
Vol 35 (3) ◽  
pp. 455E-455
Author(s):  
Shiow Y. Wang ◽  
Hongjun Jiao
Keyword(s):  
Hydrogen Peroxide ◽  
Ascorbic Acid ◽  
Singlet Oxygen ◽  
Hydroxyl Radicals ◽  
Fruit Juice ◽  
Active Oxygen Species ◽  
Active Oxygen ◽  
Oxygen Species ◽  
Scavenging Capacity ◽  
Β Carotene

The effect of blackberries (Rubus sp.) genotypes on antioxidant activities against superoxide radicals (O2–), hydrogen peroxide (H2O2), hydroxyl radicals (OH), and singlet oxygen (O,), was evaluated. The results were expressed as percent inhibition of active oxygen species production in the presence of fruit juice. The active oxygen radical absorbance capacity (ORAC) value referred to the net protection in the presence of fruit juice, and was expressed as micromoles of α-tocopherol, ascorbate, α-tocopherol, and β-carotene equivalents per 10 g of fresh weight for O2–, H2O2, OH, and O2, respectively. Among the different cultivars, juice of Hull' blackberry had the highest oxygen species, superoxide radicals (O2–), hydrogen peroxide (H2O2), hydroxyl radicals (OH), and singlet oxygen (O2,) scavenging capacity. Different antioxidants have their functional scavenging capacity against active oxygen species. There were interesting and marked differences among the different antioxidants in their abilities to inhibit the different active oxygen species. β-carotene had by far the highest scavenging activity against O2– but had absolutely no effect on H2O2. Ascorbic acid was the best at inhibiting H2O2 free radical activity. For OH, there was a wide range of scavenging capacities with α-tocopherol the highest and ascorbic acid the lowest. Glutathione had higher O2– scavenging capacity compared to the other antioxidants.

A Phytotoxicity Biosensor using Photosynthetic Membranes

1990 ◽  
Vol 25 (2) ◽  
pp. 175-186 ◽  
Author(s):  
Marc Purcell ◽  
Robert Carpentier
Keyword(s):  
Electron Transport ◽  
Small Volume ◽  
Chlorophyll Concentration ◽  
Photosynthetic Electron Transport ◽  
Inhibitory Effect ◽  
Thylakoid Membranes ◽  
Photoelectrochemical Cell ◽  
Synthetic Membranes ◽  
Low Concentrations ◽  
Artificial Electron Acceptor

Abstract The potential of a photoelectrochemical cell employing photo-synthetic membranes in an application as a phytotoxicity biosensor is demonstrated. In this cell, a small volume (80 μl) of isolated thylakoid membranes is used to produce a photocurrent. The reduced species produced during photosynthetic electron transport are oxidized by soluble electroactive mediators which are reoxidized by a platinum working electrode. The photocurrent generated was inhibited by relatively low concentrations of herbicides, nitrite, sulfite and several heavy metals due to their inhibitory effect on photosynthetic electron transport. The cell sensitivity was enhanced when chlorophyll concentration was reduced and artificial electron acceptor concentration was increased.

A new mild, clean and highly efficient method for the preparation of graphene quantum dots without by-products

2015 ◽  
Vol 3 (34) ◽  
pp. 6871-6876 ◽  
Author(s):  
Chong Zhu ◽  
Siwei Yang ◽  
Gang Wang ◽  
Runwei Mo ◽  
Peng He ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Quantum Dots ◽  
Graphene Oxide ◽  
Tungsten Oxide ◽  
Hydroxyl Radicals ◽  
Efficient Method ◽  
Graphene Quantum Dots ◽  
Catalytic Decomposition ◽  
Highly Efficient ◽  
By Products

We demonstrated that graphene oxide can be oxidized and cut into graphene quantum dots by hydroxyl radicals which is obtained by catalytic decomposition of hydrogen peroxide with a tungsten oxide nanowire catalyst.

scholarly journals Salt Priming Protects Photosynthetic Electron Transport against Low-Temperature-Induced Damage in Wheat

Sensors ◽  
2019 ◽  
Vol 20 (1) ◽  
pp. 62 ◽  
Author(s):  
Hui Li ◽  
Huawei Li ◽  
Yanjie Lv ◽  
Yongjun Wang ◽  
Zongshuai Wang ◽  
...  
Keyword(s):  
Electron Transport ◽  
Low Temperature ◽  
Reaction Center ◽  
Early Stage ◽  
Photochemical Efficiency ◽  
Photosynthetic Electron Transport ◽  
Nacl Solution ◽  
Wheat Seedlings ◽  
Germinating Seeds ◽  
Salt Priming

Low temperature limits the photochemical efficiency of photosystems in wheat plants. To test the effect of salt priming on the photosynthetic electron transport in wheat under low temperature, the germinating seeds of a winter wheat cv. Jimai44 were primed with varying concentrations of NaCl solutions (0, 10, 30, and 50 mM NaCl, indicated by S0, S10, S30, and S50, respectively) for 6 d, and after 11 d of recovery, the seedlings were subsequently exposed to 24-h low-temperature stress (2 °C). Under low temperature, the S30 plants possessed the highest absorption flux per reaction center and higher density of reaction center per cross-section among the treatments. In addition, S30 plants had higher trapped energy flux for reducing QA and fraction of QA-reducing reaction centers and non-QB reducing center than the non-primed plants under low temperature, indicating that S30 plants could maintain the energy balance of photosystems and a relatively higher maximum quantum efficiency of photosystem II under low temperature. In addition, the low temperature-induced MDA accumulation and cell death were alleviated by salt priming in S30 plants. It was suggested that salt priming with an optimal concentration of NaCl solution (30 mM) during seed germination enhanced the photochemical efficiency of photosystems in wheat seedlings, which could be a potential approach to improve cold tolerance in wheat at an early stage.

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