scholarly journals Production of Singlet Oxygen (1O2) during the Photochemistry of Aqueous Pyruvic Acid: The Effects of pH and Photon Flux under Steady-State O2(aq) Concentration

2019 ◽  
Vol 53 (21) ◽  
pp. 12425-12432 ◽  
Author(s):  
Alexis J. Eugene ◽  
Marcelo I. Guzman
Keyword(s):  
Steady State ◽  
Singlet Oxygen ◽  
Pyruvic Acid ◽  
Photon Flux ◽  
Effects Of Ph

Active oxygen species in the liver of rats submitted to chronic hypobaric hypoxia

1993 ◽  
Vol 264 (6) ◽  
pp. C1395-C1400 ◽  
Author(s):  
L. E. Costa ◽  
S. Llesuy ◽  
A. Boveris
Keyword(s):  
Steady State ◽  
Singlet Oxygen ◽  
Active Oxygen Species ◽  
Liver Mitochondria ◽  
Active Oxygen ◽  
Female Rats ◽  
H2o2 Production ◽  
Oxygen Species ◽  
State Concentration

The spontaneous in situ liver chemiluminescence of female rats submitted to 4,400 m (simulated altitude) for 2 mo and of their corresponding controls at sea level was determined as an approach to the measurement of the intracellular steady-state concentrations of singlet oxygen and oxygen free radicals. Spontaneous liver chemiluminescence was decreased by approximately 40% in hypoxic rats, whereas CCl4-induced chemiluminescence was unchanged. Liver mitochondria isolated from hypoxic rats showed a 53% decreased rate of H2O2 production and an increased content of cytochrome b (36%), with normal content of cytochromes c1, c, and a-a3. Superoxide dismutase showed a 26% decrease in activity, whereas catalase and glutathione peroxidase activities were not significantly decreased by this extent of hypoxia. Cytochrome P-450 and glutathione contents were unchanged. There were no significant differences in the hydroperoxide-initiated chemiluminescence (an estimation of tissue chain-breaker antioxidants) of homogenates, mitochondria, and microsomes. Results suggest that in chronic hypoxia there is a lower rate of generation of active oxygen species in liver, leading to a decreased steady-state concentration of singlet oxygen.

Lactic and Pyruvic Acid Relations in Contracting Mammalian Muscle

1956 ◽  
Vol 186 (2) ◽  
pp. 221-223 ◽  
Author(s):  
Jacob Sacks ◽  
Jo H. Morton
Keyword(s):  
Lactic Acid ◽  
Steady State ◽  
Pyruvic Acid ◽  
Acid Content ◽  
Marked Decrease ◽  
Blood Stream ◽  
Anaerobic Conditions ◽  
Tetanic Contraction ◽  
Mammalian Muscle ◽  
Lactic Acid Content

Tetanic contraction of mammalian muscle under essentially anaerobic conditions was found to result in marked increase in the pyruvic acid content as well as in the lactic acid content. The increase in lactic acid content was proportionately greater than in the pyruvic acid content. Repeated single twitches at a rate of 1/sec., continued long enough to produce a steady state, resulted in only a slight increase in pyruvic acid content, with a marked decrease in the ratio of pyruvic to lactic acid. The pyruvic acid formed during the steady state of activity appears not to pass into the blood stream.

Phosphate Requirement, Photosynthesis, and Diel Cell Cycle of Scenedesmus obliquas Under Fluctuating Light

1987 ◽  
Vol 44 (10) ◽  
pp. 1753-1758 ◽  
Author(s):  
C. N. Shin ◽  
G-Y Rhee ◽  
J. Chen
Keyword(s):  
Steady State ◽  
Average Rate ◽  
Scenedesmus Obliquus ◽  
Constant Light ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Cell Numbers ◽  
P Limitation ◽  
Fluctuating Light ◽  
Light Fluctuation

The effect of light fluctuation (0.06 Hz) on P requirement, photosynthesis, and the diel cell-division cycle was investigated in Scenedesmus obliquus in a chemostat under a 12 h day: 12 h night cycle. P requirement was much less under oscillating than under constant daylight of the same photon flux density. However, cell chlorophyll a was significantly higher, indicating an increased N requirement. There was little difference in photosynthetic efficiency (the slope of the photosynthesis–light regression) between oscillating and constant light, but photosynthetic capacity was higher in fluctuating light. Cell C was also higher. A strong diel rhythmicity in steady-state cell numbers was observed with little phase difference between oscillating and constant light. Although steady-state cell numbers under P limitation were significantly higher under fluctuating light, there was no difference in instantaneous growth rates and their diel distribution. At a dilution rate of 0.6∙d−1, cell death occurred at an average rate of −0.56∙d−1 between 4 h before and 5 h after the onset of the dark period.

scholarly journals ENGINEERING FOR MICROPROPAGATION OF SUGARCANE

HortScience ◽  
1992 ◽  
Vol 27 (6) ◽  
pp. 618b-618
Author(s):  
Paul N. Walker ◽  
Joan P. Harris ◽  
Loren D. Gautz
Keyword(s):  
Linear Programming ◽  
Steady State ◽  
Programming Model ◽  
Cost Model ◽  
Photon Flux ◽  
Unsteady State ◽  
Photosynthetic Photon Flux ◽  
Engineering Studies ◽  
State Production ◽  
The Cost

Four engineering studies on optimization of sugarcane micropropagation are summarized. The optimum environmental conditions based on the cost of production were found to be with two medium changes per multiplication period, 6 initial shoots per vessel and a photosynthetic photon flux of 200 μmol/m2s even though greater production was obtained for more light, fewer shoots per vessel and more medium changes. A cost model for comparing production treatments under steady state production and a linear programming model for unsteady state production are discussed. Preliminary results on mechanization of the transfer process are also presented.

scholarly journals Effects of pH and Repellent Tactic Stimuli on Protein Methylation Levels in Escherichia coli

1982 ◽  
Vol 152 (1) ◽  
pp. 384-399
Author(s):  
Joan L. Slonczewski ◽  
Robert M. Macnab ◽  
Jeffry R. Alger ◽  
Anna M. Castle
Keyword(s):  
Escherichia Coli ◽  
Steady State ◽  
Methylation Level ◽  
Control Level ◽  
Weak Acid ◽  
Base Hydrolysis ◽  
Constant Ph ◽  
Effects Of Ph ◽  
Chemotaxis Proteins ◽  
High Concentrations

Intracellular pH (pH int ) and extracellular pH (pH ext ) of Escherichia coli were measured at 12-s time resolution by 31 P-nuclear magnetic resonance: a sudden neutral-to-acid shift in pH ext (e.g., from 7.0 to 5.6) caused a transient failure of homeostasis, with pH int decreasing by about 0.4 unit in ca. 30 s and then returning to its original value (ca. 7.5) over a period of several minutes. Membrane proton conductance was estimated to be 20 pmol s −1 cm −2 pH unit −1 . Addition of the membrane-permeant weak acid benzoate at constant pH ext also caused a lowering of pH int ; at high concentrations it generated an inverted transmembrane pH gradient (ΔpH). The buffering capacity of the cells was estimated by such experiments to be ca. 50 mM per pH unit. Effects of pH-related stimuli on the methyl-accepting chemotaxis proteins (MCPs) were examined: the steady-state methylation of MCP I was found to decrease when pH int was lowered by weak acid addition or when pH ext was lowered. The extent of demethylation in the latter case was too great to be explained by imperfect steady-state homeostasis; a small but reproducible undershoot in methylation level correlated with the observed short-term homeostatic failure. MCP II underwent smaller and more complex changes than MCP I, in response to pH-related stimuli. The methylation level of MCP I could not, by any condition tested, be driven below a limit of ca. 15% of the control level (unstimulated cells at pH ext 7.0). The weak-acid concentration needed to reach that limit was dependent on pH ext , as would be expected on the basis of ΔpH-driven concentrative effects. The potency ranking of weak acids was the same with respect to lowering pH int , demethylating MCP I, and causing repellent behavioral responses. The data are consistent with a model whereby MCP I and hence tactic behavior are sensitive to both pH int and pH ext . Evidence is presented that pH int may also have a direct (non-MCP-related) effect on motor function. Comparison of methyl - 3 H- and 35 S-labeled MCP I revealed that in both unstimulated and repellent-stimulated cells the major species did not carry methyl label, yet it had an electrophoretic mobility that indicated that it was more positively charged than the unmethylated form observed in methyltransferase mutants, and it was susceptible to base hydrolysis. This suggests that a substantial fraction of MCP I molecules is methylated or otherwise modified but neither exchanges methyl label nor undergoes reverse modification by repellent stimuli.

How quality and quantity of brown carbon influence singlet oxygen production in aqueous organic aerosols

2021 ◽  
Author(s):  
Sophie Bogler ◽  
Nadine Borduas-Dedekind ◽  
Imad el Haddad ◽  
David Bell ◽  
Kaspar Dällenbach
Keyword(s):  
Reactive Oxygen Species ◽  
Steady State ◽  
Quantum Yield ◽  
Singlet Oxygen ◽  
Molecular Oxygen ◽  
Biomass Burning ◽  
Secondary Organic Aerosols ◽  
Organic Aerosols ◽  
Oxygen Species ◽  
Brown Carbon

<p>Singlet oxygen (<sup>1</sup>O<sub>2</sub>) is a reactive oxygen species that has recently gained attention as a competitive oxidant in the atmosphere. This excited state of molecular oxygen is formed by indirect photochemistry in the presence of chromophoric dissolved organic matter (DOM) as sensitizers, molecular oxygen and sunlight. The produced highly reactive intermediate <sup>1</sup>O<sub>2 </sub>is then capable of oxidizing and degrading many organic atmospheric components, thereby affecting their lifetime in the atmosphere. Despite this influence on atmospheric fate, the spatiotemporal distribution of <sup>1</sup>O<sub>2</sub> in particular matter (PM) is currently unknown. We hypothesized that brown carbon in biomass burning organic aerosols emitted during winter in Switzerland would lead to higher <sup>1</sup>O<sub>2</sub> steady-state concentrations in PM compared to summer. Therefore, to advance atmospheric <sup>1</sup>O<sub>2 </sub>research, we investigated the <sup>1</sup>O<sub>2</sub> sensitizing ability of organic aerosols sampled on 24-hour PM10 filters. Specifically, these filters were collected throughout 2013 in Frauenfeld and San Vittore in Switzerland, characterized as urban background and rural traffic measurement stations, respectively. We extracted the water-soluble organic components and quantified <sup>1</sup>O<sub>2 </sub>steady state concentrations as well as <sup>1</sup>O<sub>2</sub> quantum yield. The quantum yield enhances the data intercomparison as this value shows the normalization of <sup>1</sup>O<sub>2 </sub>production as a function of the rate of absorbance of the organic aerosols. In our ongoing efforts of expanding the spatiotemporal scale of our measurements, our results from Frauenfeld so far show a range between 0.38 – 6.05 · 10<sup>-13 </sup>M for <sup>1</sup>O<sub>2 </sub>steady state concentrations and quantum yields up to 2.1± 0.5<sup></sup>%. In preliminary experiments, samples from the rural site San Vittore show similar values, with potentially higher values during periods of significant biomass burning contributions. The values underline <sup>1</sup>O<sub>2</sub>’s<sub></sub>potential importance for atmospheric processing, e.g. comparing to Manfrin et al. (ES&T, 2019)<sup>1</sup> who reported <sup>1</sup>O<sub>2 </sub>steady state concentrations of 3 ± 1 · 10<sup>-14 </sup>M from secondary organic aerosols extracts. More importantly, the filter extracts analyzed thus far show a strong seasonal trend, with increased <sup>1</sup>O<sub>2 </sub>values and higher variability in winter as compared to summer. This result corroborates the hypothesis that there is more chromophoric DOM present in winter, due to a higher fraction of brown carbon emitted e.g. in biomass burning for residential heating. To extend this analysis, we are currently correlating the results for <sup>1</sup>O<sub>2 </sub>with molecular markers based on mass spectrometry data available from previous filter analysis provided by Daellenbach et al., (ACP, 2017)<sup>2</sup>. Finding these correlations will enable the prediction of <sup>1</sup>O<sub>2 </sub>sensitizing abilities of organic material present in the aerosols both qualitatively and quantitatively. In all, our work will help constrain the seasonal relevance of <sup>1</sup>O<sub>2 </sub>photochemistry in the atmosphere.</p><p><strong>References</strong></p><p>1. Manfrin, A. et al. Reactive Oxygen Species Production from Secondary Organic Aerosols: The Importance of Singlet Oxygen. Environmental Science & Technology 53, 8553–8562 (2019).<br>2. Daellenbach, K. R. et al. Long-term chemical analysis and organic aerosol source apportionment at nine sites in central Europe: source identification and uncertainty assessment. Atmospheric Chemistry and Physics 17, 13265–13282 (2017).</p>

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