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1.
Photosynthesis, Photorespiration and Respiration of Detached Spruce Twigs as Influenced by Oxygen Concentration and Light Intensity 总被引:1,自引:0,他引:1
J. Poskuta 《Physiologia plantarum》1968,21(5):1129-1136
The effects of oxygen concentration and light intensity on the rates of apparent photosynthesis, true photosynthesis, photorespiration and dark respiration of detached spruce twigs were determined by means of an infra-red carbon dioxide analyzer (IRCA). A closed circuit system IRCA was filled with either 1 per cent of oxygen in nitrogen, air (21 % O2) or pure oxygen (100 % O2). Two light intensities 30 × 103 erg · cm ?2· s?1 and 120 × 103 erg · cm?2· s?1 were applied. It has been found that the inhibitory effect of high concentration of oxygen on the apparent photosynthesis was mainly a result of a stimulation of the rate of CO2 production in light (photorespiration). In the atmosphere of 100 % O2, photorespiration accounts for 66–80 per cent of total CO2 uptake (true photosynthesis). Owing to a strong acceleration of photorespiration by high oxygen concentrations, the rate of true photosynthesis calculated as the sum of apparent photosynthesis and photorespiration was by several times less inhibited by oxygen than the rate of apparent photosynthesis. The rates of dark respiration were essentially unaffected by the oxygen concentrations used in the experiments. An increase in the intensity of light from 30 × 103 erg · cm?3· s?1 to 120 · 103 erg · cm?2· s?1 enhanced the rate of photorespiration in the atmospheres of 21 and 100 % oxygen but not in 1 % O2. The rate of apparent photosynthesis, however, was little affected by light intensity in an atmosphere of 1 % oxygen. 相似文献
2.
-Rates of oxygen uptake were measured in chick and/or rat astrocytes and neuronal cells cultivated for 2–4 weeks in Falcon flasks or Rose chambers. All the preparations were found to have respiratory rates between 0.4 and 0.8 × 10?5μl/h O2 per cell. Based upon measurements of cell diameters these values were recalculated to about 570 μmol/g wet wt. for the neuronal cells and 130 μmol/g wet wt. for the glial cells. The results are compared with previous data of oxygen uptake by neurons and glial cells separated by other procedures. 相似文献
3.
Inhibition of photosynthesis after exposure to solar radiation was investigated in the marine green alga Dunaliella salina by monitoring photosynthetic optimal quantum yield Fv/Fm and efficiency of oxygen production. Samples were exposed to solar radiation in Ancient Korinth, Greece (37°58′ N, 23°0′ E) in August 1994. Within 30 min, Fv/Fm and efficiency of oxygen production decreased with similar kinetics with increasing exposure time. The inhibition, however, diminished when ultraviolet radiation was progressively excluded by means of colour filter glasses. Samples exposed for 3 h showed complete or partial recovery of photosynthesis, with almost the same rate under all irradition conditions. The fit of the experimental data with an analytical model describing inhibition of photosynthesis as a function of a linear combination of the photon fluence in the UV-B, UV-A and PAR allows one to estimate the relative mean effectiveness for inhibition by the three spectral ranges [about 2 × 10?4, 4 × 10?6 and 2 × 10?7 (μmol photons m?2)?1 for UV-B, UV-A and PAR, respectively]. 相似文献
4.
The oxidation reaction of H2O2 with KIO4 can produce chemiluminescence (CL) in the presence of the surfactant Tween40 and the CL intensity of the CL system KIO4–H2O2–Tween40 can be strikingly enhanced after injection of tannic acid. On this basis, a flow injection method with CL detection was established for the determination of tannic acid. The method is simple, rapid and effective to determine tannic acid in the range of 7.0 × 10?9 to 1.0 × 10?5 mol/L with a determination limit of 2.3 × 10?9 mol/L. The relative standard deviation is 2.6% for the determination of 5.0 × 10?6 mol/L tannic acid (n = 11). The method has been applied to determine the content of tannic acid in industrial wastewater with satisfactory results. It is believed that the CL reaction formed singlet oxygen 1O2* and the emission was from an excited oxygen molecular pair O2(1Δg)O2(1∑?g) in the KIO4–H2O2–Tween40 reaction. Tween40 played an important role in enhancing stabilization of the excited oxygen molecular pair O2(1Δg)O2(1∑?g) and in increasing CL intensity. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
5.
A chemiluminescent assay composed of TCPO [bis(2,4,6-trichlorophenyl)oxalate] and harmless rhodamine B is proposed to be superior in the determination of menadione-catalyzed hydrogen peroxide (H2O2) production by viable mammalian cells to that composed of TCPO and harmful pyrene [Anal. Biochem. 207 (1992) 255–260]. In tests, the proposed assay showed that the measurable concentration of H2O2 and the viable cell number ranged from 10?9 to 10?3 M and from 2 × 102 to 2 × 106 cells/100 μl/well in the presence of 10% bovine serum, respectively. The measuring time was approximately 10 min. On the other hand, the measurable cell numbers by the colorimetric WST-1 and MTT assays requiring several hours ranged only from 103 to 104 cells/100 μl/well and from 104 to 105 cells/100 μl/well, respectively. The cytotoxicity of sodium dodecyl sulfate was also observed at intervals of 1 min by the proposed assay, but not by the above colorimetric assays. 相似文献
6.
《Free radical research》2013,47(4-6):259-270
Using the pulse radiolysis technique, we have demonstrated that bleomycin-Fe(III) is stoichiometrically reduced by CO2? to bleomycin-Fe(II) with a rate of (1.9 ± 0.2) × 108M?1s?1. In the presence of calf thymus DNA, the reduction proceeds through free bleomycin-Fe(III) and the binding constant of bleomycin-Fe(III) to DNA has been determined to be (3.8 ± 0.5) x 104 M?1. It has also been demonstrated that in the absence of DNA O2?1 reacts with bleomycin-Fe(III) to yield bleomycin-Fe(II)O2, which is in rapid equilibrium with molecular oxygen, and decomposes at room temperature with a rate of (700 ± 200) s?1. The resulting product of the decomposition reaction is Fe(III) which is bound to a modified bleomycin molecule. We have demonstrated that during the reaction of bleomycin-Fe(II) with O2, modification or self-destruction of the drug occurs, while in the presence of DNA no destruction occurs, possibly because the reaction causes degradation of DNA. 相似文献
7.
Flow injection chemiluminescence determination of naphazoline hydrochloride in pharmaceuticals
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A simple and sensitive flow injection chemiluminescence (FI‐CL) method was developed for the determination of naphazoline hydrochloride (NPZ). The method is based on the enhancing effect of NPZ on the weak CL signal from the reaction of KIO4 with H2O2. Experimental parameters that affected the CL signal, including the pH of the KIO4 solution, concentrations of KIO4, H2O2 and disodium‐EDTA and flow rate were optimized. Under the optimum conditions, the increment of CL intensity was linearly proportional to the concentration of NPZ in the range 5.0 × 10?6 to 70 × 10?6 mol/L. The detection limit was 1.0 × 10?6 mol/L and the relative standard deviation for 50 × 10?6 mol/L NPZ solution was 2.8% (n = 11). In addition, a high throughput of 120 samples/h was achieved. The utility of this method was demonstrated by determining NPZ in pharmaceuticals. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
8.
Effect of external oxygen demand on radial oxygen loss by Juncus roots in titanium citrate solutions 总被引:3,自引:1,他引:2
B. K. Sorrell 《Plant, cell & environment》1999,22(12):1587-1593
Radial oxygen loss (ROL) from the roots of two semiaquatic rushes, Juncus effusus L. and Juncus inflexus L., was studied in reducing titanium citrate buffer, using both closed incubations and a flow-through, titrimetric system. In closed experiments, roots released oxygen at a constant rate over a wide range of external oxygen demands, with the ROL rate only depending on sink strength at low demands, and no oxygen release into oxidized solutions. In the titrimetric experiments, roots continued to release oxygen at constant rates when provided with a constant external oxygen demand. ROL was higher in J. effusus (9·5 ± 1 × 10?7 mol O2 h?1 root?1) than in J. inflexus (4·5 ± 0·5 × 10?7 mol O2 h?1 root?1). Light and dark changes around the shoots did not affect the ROL rate in J. inflexus, whereas in J. effusus ROL was ≈ 1·75 times higher in the light than in the dark, presumably due to changes in stomatal aperture. These results suggest that ROL is controlled by the external oxygen demand at low to moderate reducing intensities, but that structural limitations to oxygen diffusion rates prevent ROL from continuing to increase at higher external oxygen demands. 相似文献
9.
The mechanism for the hydroxyl-radical-induced depolymerization of cellulose under alkaline conditions in air was investigated using density functional theory at the B3LYP/6-31+G(d,p) level as well as electron transfer theory. The pathway for the depolymerization of cellulose was obtained theoretically and H abstraction from the C(3) atom of the pyran ring during the cleavage of the glucosidic bond was found to be the rate-limiting step due to its high energy barrier (16.81 kcal/mol) and low reaction rate constant (4.623?×?104 mol L?1 s?1). Calculations of the electron transfer between O2 and the saccharide radical performed with the HARLEM software package revealed that following the H abstraction, the oxygen molecule approaches C(2) on the saccharide radical and obtains an electron from the radical, even though no bond forms between the oxygen molecule and the radical. The rate constant for electron transfer could be as high as 1.572?×?1011 s?1. Furthermore, an enol intermediate is obtained during the final stage of the depolymerization. 相似文献
10.
Yuko Iwasaki Shingo Takahashi Koichi Aizawa 《Bioscience, biotechnology, and biochemistry》2013,77(2):280-291
Measurements of the second-order rate constants and the singlet oxygen absorption capacity (SOAC) values for the reaction of singlet oxygen (1O2) with 23 kinds of food extracts were performed in ethanol/chloroform/D2O (50:50:1, v/v/v) solution at 35 °C. It has been clarified that the SOAC method is useful to evaluate the 1O2-quenching activity (i.e. the SOAC value) of food extracts having two orders of magnitude different rate constants from 3.18 × 104 L g?1 s?1 for tomato to 1.55 × 102 for green melon. Furthermore, comparison of the observed rate constants for the above food extracts with the calculated ones based on the concentrations of seven kinds of carotenoids included in the food extracts and the rate constants reported for each carotenoids was performed, in order to ascertain the validity of the SOAC assay method developed and to clarify the ratio of the contribution of principal carotenoids to the SOAC value. 相似文献
11.
In this work, the effects of H2O2 at concentrations of 10?8–10?2 mol/l on the neutrophil ability to generate reactive oxygen and chlorine species (ROCS) and to secrete myeloperoxidase (MPO) were studied, as well as the H2O2 damaging action on neutrophils. It was found that H2O2 at concentrations of 2 × 10?3–10?2 mol/l led to disturbances of neutrophil membrane barrier properties and to a lactate dehydrogenase release. Incubation of neutrophils with an addition of 10?4–10?7 mol/l H2O2 was accompanied by an increase of the cell ability to generate ROCS during phagocytosis and a decrease of neutrophil ability to secrete MPO and ROCS into the extracellular medium during adhesion. Mechanisms of the H2O2 action are coupled with arachidonic acid metabolism. Inhibition of the 5-lipoxygenase or cyclooxygenase metabolism pathways produced an enhancement of the H2O2 destructive effect. Block of 5-lipoxygenase pathway led to elimination of the H2O2 action on MPO and ROCS secretion and to an enhancement of the H2O2 effect on the neutrophil ability to generate ROCS during phagocytosis. The obtained data indicate a high blood neutrophil resistance to the H2O2 destructive action and confirm the H2O2 regulatory role with respect to the neutrophil functions. 相似文献
12.
J.E. Packer J.S. Mahood V.O. Mora-Arellano T.F. Slater R.L. Willson B.S. Wolfenden 《Biochemical and biophysical research communications》1981,98(4):901-906
The ‘singlet oxygen scavengers’. 1,4-diazobicyclo(2,2,2)-octane (DABCO), diphenyl furan and β-carotene react rapidly with the organic peroxyradical CCl3O2?. The absolute reaction rate constants k = 1.2 ± 0.2 × 107, 6 ± 2 × 107 at 1.5 ± 0.2 × 109 M?1s?1 respectively have been determined by pulse radiolysis. Comparison with other data suggest that other free radicals are also likely to react with these compounds; in the case of the hydroxyl radical and DABCO k = 1.25 × 109 M?1s?1 has been determined. 相似文献
13.
Replacement of media in cell cultures during exposure to hyperoxia was found to alter oxygen toxicity. Following 100 hr of exposure to 95% or 80% O2, the surviving fraction (SF) of Chinese hamster fibroblasts, as assayed by clonogenicity, was less than 1 × 10?3 when the culture media was replaced only at the onset of the O2 exposure. Media replacement every 24 hr throughout the hyperoxic exposure resulted in SFs of 1.7 × 10?1 (95% O2) and 1.9 × 10?1 (80% O2) at 95 hr. Cellular resistance to and metabolism of 4-hydroxy-2-nonenal (4HNE), a cytotoxic byproduct of lipid peroxidation, was examined in cells 24 hr following exposure to 80% O2 for 144 hr with media replacement. These O2-exposed cells were resistant to 4HNE, requiring 2.6 times as long in 80 μM 4HNE to reach 30% survival as compared to density-matched normoxia control. Furthermore, during 40 and 60 min of exposure to 4HNE, the O2-preexposed cells metabolized greater quantities of 4HNE (fmole/cell) relative to control. The activity of glutathione S-transferase (GST), an enzyme believed to be involved with the detoxification of 4HNE, was significantly increased in the O2-preexposed cells compared with controls. Catalase activity was significantly increased, but no change was found in total glutathione content, glutathione peroxidase, manganese superoxide dismutase, and copper-zinc superoxide dismutase activities at the time of 4HNE treatment in the O2-preexposed cells relative to density-matched control. The results demonstrate that in vitro tolerance to the cytotoxic effects of hyperoxia can be achieved through media replacement during O2 exposure. Tolerance to oxygen toxicity conferred resistance to the cytotoxic effects of 4HNE, possibly through GST-catalyzed detoxification. These results provide further support for the hypothesis that toxic aldehydic byproducts of lipid peroxidation contribute to hyperoxic injury. 相似文献
14.
Hydrogen peroxide amplifies the chemiluminescence in the oxidation of luminol by sodium hypochlorite. A linear relationship between concentration of hydrogen peroxide and light intensity was found in the concentration range 5 × 10?8?7.5 × 10?6 mol/l. At 7.5 × 10?6 mol/l H2O2 the chemiluminescence is amplified 550—fold. The chemiluminescence spectra of these reactions have a wavelength maximum at 431 nm independent of the concentration of hydrogen peroxide. The results indicate that hydrogen peroxide is a necessary component in the chemiluminescent oxidation of the luminol by sodium hypochlorite. 相似文献
15.
Escherichia coli B were more susceptible to radiation lethality and showed a greater oxygen enhancement ratio when exposed in dilute suspension (1 × 105 cells/ml) than when exposed in dense suspensions (1 × 109 cells/ml). The oxygen enhancement, seen with dilute suspensions, was diminished by superoxide dismutase, catalase, mannitol, or histidine. Heat-denatured superoxide dismutase was without effect. The results are interpreted as indicating a role for O2? plus H2O2 in the oxygen enhancement of radiation lethality, and a scheme is proposed which is consistent with the observations. 相似文献
16.
The main purpose of this study was to develop an inexpensive, simple, rapid and sensitive chemiluminescence (CL) method for the determination of glutamine (Gln) using a flow‐injection (FI) system. Gln was found to strongly inhibit the CL signal of the luminol–H2O2–CuSO4 system in Na2B4O7 solution. A new FI‐CL method was developed for the determination of Gln. Parameters affecting the reproducibility and CL detection were optimized systematically. Under the optimized conditions, the corresponding linear regression equation was established over the range of 5.0 × 10?7 to 2.5 × 10?6 mol/L with the detection limit of 1.8 × 10?8 mol/L. The relative standard deviation was found to be 1.8% for 11 replicate determinations of 1.5 × 10?6 mol/L Gln. The proposed method has been satisfactorily applied for the determination of Gln in real samples (Marzulene‐s granules) with recoveries in the range of 98.7–108.6%. The minimum sampling rate was about 100 samples/h. The possible mechanism of this inhibitory CL was studied by fluorescence spectrophotometer and UV–vis spectrophotometer. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
17.
《Free radical research》2013,47(4):241-253
We have evaluated the abilities of ferulic acid, (±) catechin, (+) catechin and (-) epicatechin to scavenge the reactive oxygen species hydroxyl radical (OH±), hypochlorous acid (HOCl) and peroxyl radicals (RO2).Ferulic acid tested at concentrations up to 5 mM inhibited the peroxidation of phospholipid liposomes. Both (±) and (+) catechin and (-) epicatechin were much more effective. All the compounds tested reacted with trichloromethyl peroxyl radical (CCl3O2) with rate constants > 1 × 106M?1s?1.A mixture of FeCl3-EDTA, hydrogen peroxide (H2O2) and ascorbic acid at pH 7.4, has often been used to generate hydroxyl radicals (OH.) which are detected by their ability to cause damage to the sugar deoxyribose. Ferulic acid, (+) and (±) catechin and (-) epicatechin inhibited deoxyribose damage by reacting with OH. with rate constants of 4.5 × 109M?1s?1, 3.65 × 109M?1s?1, 2.36 × 109M?1s?1 and 2.84 × 109M?1s?1 respectively. (-) Epicatechin, ferulic acid and the (+) and (±) catechins exerted pro-oxidant action, accelerating damage to DNA in the presence of a bleomycin-iron complex. On a molar basis, ferulic acid was less effective in causing damage to DNA compared with the catechins.A mixture of hypoxanthine and xanthine oxidase generates O2 which reduces cytochrome c to ferrocytochrome c. (+) Catechin and (-) epicatechin inhibited the reduction of cytochrome c in a concentration dependent manner. Ferulic acid and (±) catechin had only weak effects.All the compounds tested were able to scavenge hypochlorous acid at a rate sufficient to protect alpha-1-antiproteinase against inactivation. Our results show that catechins and ferulic acid possess antioxidant properties. This may become important given the current search for “natural” replacements for synthetic antioxidant food additives. 相似文献
18.
K Nagami 《Biochemical and biophysical research communications》1973,51(2):364-369
The fast reaction technique of pulse radiolysis was used to produce free radicals in aqueous solution from alcohols, deoxyribose, cytosine, uracil, thymine, dihydrothymine and histidine. The electron transfer reactions from these radicals to p-benzoquinone was observed from the formation kinetics of the semiquinone anion ·BQ? at 430 nm and the efficiency was found to be as high as 90% or more, with k~5×109 M?1sec?1. In acid or neutral solutions in the presence of oxygen the peroxy radicals ·O2RH formed do not essentially transfer an electron to BQ, and the efficiency is <10%. The significance of these results in the fixation of radiation damage in photobiology and radiation biology are indicated. The reactions of the superoxide ·O2? radical with BQ are also presented and discussed. 相似文献
19.
《Free radical research》2013,47(1-5):173-184
The sources and steady-state concentration of singlet oxygen in the atmosphere are assessed in view of potential effects on the biosphere. Collision-induced absorption of sunlight by molecular oxygen in 1 atm of air produces O2(a'δg) at a rate P = 1.6 × 10'cm's?1 in bright sunlight. Less than 10% are added to this purely natural source by the photolysis of ozone, and by anthropogenic sensitizers (SO2, NO2, volatile aromatics). Collisional quenching of O2(a'δg) by ground state oxygen establishes a steady-state concentration of ca. 1.7 × 108cm?1'. Reactions of singlet oxygen with other atmospheric pollutants are entirely negligible when compared with the concurrent reactions of ambient OH and 03. Potential effects of atmospheric singlet oxygen on the biosphere are limited by the deposition rate F< 0.051 P which depends on the production rate P of O2(a' δg) in the air layer immediately above the flat surface. 相似文献
20.
The degradation of phenanthrene sorbed on soil has been carried out using a H2O2/goethite heterogeneous catalytic oxidation process. The effect of operating variables, such as the goethite concentration, pH, H2O2 concentration, soil organic matter, and bicarbonate ions has been investigated. The reaction followed pseudo-first order kinetics. The rate constants were evaluated and varied between 2.0×10?4 and 1.1×10?3?min?1 depending on the H2O2 concentration. The highest rate of degradation of phenanthrene was observed at a H2O2 concentration of 5?M and 134.0?g/kg goethite. The intermediate product formed during the degradation of phenanthrene was identified to be salicylic acid that finally degraded to CO2 and H2O. H2O2 consumption continued as the OH radical attacked the salicylic acid. More than 80% consumption of the 5?M H2O2 took place within 30?min, and the degradation was almost complete after 3?h of reaction. Neutral pH was found to be effective in the removal of phenanthrene. Both soil organic matter (SOM) and bicarbonate ions in the soil inhibited the oxidation rate of phenanthrene. 相似文献