The role of carbonate radicals on the kinetics, radical chemistry, and energy requirement of UV/chlorine and UV/H2O2 processes

Chemosphere ◽  
2021 ◽  
pp. 130499
Author(s):  
Shumin Zhu ◽  
Zaochen Tian ◽  
Pin Wang ◽  
Weiqiu Zhang ◽  
Lingjun Bu ◽  
...  
Keyword(s):  
Energy Requirement ◽  
Radical Chemistry

scholarly journals Molecular Hydrogen, a Neglected Key Driver of Soil Biogeochemical Processes

2019 ◽  
Vol 85 (6) ◽  
Author(s):  
Sarah Piché-Choquette ◽  
Philippe Constant
Keyword(s):  
Energy Requirement ◽  
Keystone Species ◽  
Physiological Role ◽  
Atp Synthesis ◽  
Potential Contribution ◽  
Biogeochemical Processes ◽  
Individual Level ◽  
C Cycling ◽  
The Impact

ABSTRACTThe atmosphere of the early Earth is hypothesized to have been rich in reducing gases such as hydrogen (H2). H2has been proposed as the first electron donor leading to ATP synthesis due to its ubiquity throughout the biosphere as well as its ability to easily diffuse through microbial cells and its low activation energy requirement. Even today, hydrogenase enzymes enabling the production and oxidation of H2are found in thousands of genomes spanning the three domains of life across aquatic, terrestrial, and even host-associated ecosystems. Even though H2has already been proposed as a universal growth and maintenance energy source, its potential contribution as a driver of biogeochemical cycles has received little attention. Here, we bridge this knowledge gap by providing an overview of the classification, distribution, and physiological role of hydrogenases. Distribution of these enzymes in various microbial functional groups and recent experimental evidence are finally integrated to support the hypothesis that H2-oxidizing microbes are keystone species driving C cycling along O2concentration gradients found in H2-rich soil ecosystems. In conclusion, we suggest focusing on the metabolic flexibility of H2-oxidizing microbes by combining community-level and individual-level approaches aiming to decipher the impact of H2on C cycling and the C-cycling potential of H2-oxidizing microbes, via both culture-dependent and culture-independent methods, to give us more insight into the role of H2as a driver of biogeochemical processes.

Evaluation of Mitochondrial Function in Isolated Rat Hepatocytes and Mitochondria during Oxidative Stress

2007 ◽  
Vol 35 (3) ◽  
pp. 353-361 ◽  
Author(s):  
Zuzana Červinková ◽  
Halka Lotková ◽  
Pavla Křivaková ◽  
Tomáš Roušar ◽  
Otto Kučera ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Mitochondrial Function ◽  
Mitochondrial Permeability Transition ◽  
Energy Requirement ◽  
High Energy ◽  
Molecular Probe ◽  
Isolated Rat Hepatocytes ◽  
Isolated Mitochondria

The majority of toxic agents act either fully or partially via oxidative stress, the liver, specifically the mitochondria in hepatocytes, being the main target. Maintenance of mitochondrial function is essential for the survival and normal performance of hepatocytes, which have a high energy requirement. Therefore, greater understanding of the role of mitochondria in hepatocytes is of fundamental importance. Mitochondrial function can be analysed in several basic models: hepatocytes cultured in vitro; mitochondria in permeabilised hepatocytes; and isolated mitochondria. The aim of our study was to use all of these approaches to evaluate changes in mitochondria exposed in vitro to a potent non-specific peroxidating agent, tert-butylhydroperoxide (tBHP), which is known to induce oxidative stress. A decrease in the mitochondrial membrane potential (MMP) was observed in cultured hepatocytes treated with tBHP, as illustrated by a significant reduction in Rhodamine 123 accumulation and by a decrease in the fluorescence of the JC-1 molecular probe. Respiratory Complex I in the mitochondria of permeabilised hepatocytes showed high sensitivity to tBHP, as documented by high-resolution respirometry. This could be caused by the oxidation of NADH and NADPH by tBHP, followed by the disruption of mitochondrial calcium homeostasis, leading to the collapse of the MMP. A substantial decrease in the MMP, as determined by tetraphenylphosphonium ion-selective electrode measurements, also confirmed the dramatic impact of tBHP-induced oxidative stress on mitochondria. Swelling was observed in isolated mitochondria exposed to tBHP, which could be prevented by cyclosporin A, which is evidence for the role of mitochondrial permeability transition. Our results demonstrate that all of the above-mentioned models can be used for toxicity assessment, and the data obtained are complementary.

Glucose metabolism in the lactating beagle dog

1962 ◽  
Vol 202 (2) ◽  
pp. 329-333 ◽  
Author(s):  
Jack R. Luick ◽  
Arthur L. Black ◽  
Harold R. Parker ◽  
Mogens G. Simesen
Keyword(s):  
Plasma Glucose ◽  
Metabolic Pathways ◽  
Milk Fat ◽  
Specific Activity ◽  
Energy Requirement ◽  
Similar Data ◽  
Lactating Cows ◽  
Diabetic Dog ◽  
Oxidation Of Glucose

A study was made of the role of glucose as an oxidizable substrate and as a source of C for the synthesis of milk using lactating beagle dogs. Uniformly C14-labeled glucose was used as a tracer of these metabolic pathways. Our data indicate that the labeled glucose was completely eliminated from the dog's body within 24 hr after injection. Sixty percent of the injected dose appeared in the expired CO2, 40% in the various milk products. Comparison of the integrated specific activity of plasma glucose with that of expired CO2 indicates that 36% of the dog's energy requirement is met by the oxidation of glucose. This presumably means that the catabolism of noncarbohydrate substances must be of considerable importance to the energy metabolism of not only the fasted dog and the diabetic dog, as has been demonstrated earlier, but also of the fed dog. We have also shown that 68–100% of the C required for the synthesis of lactose is derived from plasma glucose. In addition, plasma glucose contributes 7.2–12% of milk protein C and 5.1–8.7% of milk fat C. These results are compared with similar data obtained earlier in our laboratory using lactating cows and sows.

scholarly journals Hydroxy nitrate production in the OH-initiated oxidation of alkenes

2015 ◽  
Vol 15 (8) ◽  
pp. 4297-4316 ◽  
Author(s):  
A. P. Teng ◽  
J. D. Crounse ◽  
L. Lee ◽  
J. M. St. Clair ◽  
R. C. Cohen ◽  
...  
Keyword(s):  
Branching Ratio ◽  
Peroxy Radical ◽  
Branching Ratios ◽  
Peroxy Radicals ◽  
Photochemical Smog ◽  
Radical Chemistry ◽  
Heavy Atoms ◽  
Isomer Distribution ◽  
Deuterium Substitution

Abstract. Alkenes are oxidized rapidly in the atmosphere by addition of OH and subsequently O2 leading to the formation of β-hydroxy peroxy radicals. These peroxy radicals react with NO to form β-hydroxy nitrates with a branching ratio α. We quantify α for C2–C8 alkenes at 295 K ± 3 and 993 hPa. The branching ratio can be expressed as α = (0.045 ± 0.016) × N − (0.11 ± 0.05) where N is the number of heavy atoms (excluding the peroxy moiety), and listed errors are 2σ. These branching ratios are larger than previously reported and are similar to those for peroxy radicals formed from H abstraction from alkanes. We find the isomer distributions of β-hydroxy nitrates formed under NO-dominated peroxy radical chemistry to be different than the isomer distribution of hydroxy hydroperoxides produced under HO2-dominated peroxy radical chemistry. Assuming unity yield for the hydroperoxides implies that the branching ratio to form β-hydroxy nitrates increases with substitution of RO2. Deuterium substitution enhances the branching ratio to form hydroxy nitrates in both propene and isoprene by a factor of ~ 1.5. The role of alkene chemistry in the Houston region is re-evaluated using the RONO2 branching ratios reported here. Small alkenes are found to play a significant role in present-day oxidant formation more than a decade (2013) after the 2000 Texas Air Quality Study identified these compounds as major contributors to photochemical smog in Houston.

Secondary Organic Aerosol Formation from Cyclohexene Ozonolysis:  Effect of OH Scavenger and the Role of Radical Chemistry

2004 ◽  
Vol 38 (12) ◽  
pp. 3343-3350 ◽  
Author(s):  
M. D. Keywood ◽  
J. H. Kroll ◽  
V. Varutbangkul ◽  
R. Bahreini ◽  
R. C. Flagan ◽  
...  
Keyword(s):  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Aerosol Formation ◽  
Radical Chemistry ◽  
Secondary Organic Aerosol Formation

Debarking, pitch removal and retting: Role of microbes and their enzymes

2020 ◽  
Vol 5 (10) ◽  
Author(s):  
Amit Kumar ◽  
Mukesh Yadav ◽  
Workinesh Tiruneh
Keyword(s):  
Energy Requirement ◽  
Paper Industry ◽  
White Rot Fungi ◽  
White Rot ◽  
Operating Costs ◽  
Enzyme Treatment ◽  
Chemical Additives ◽  
Wood Extractives ◽  
Paper Manufacturing

AbstractMicrobial enzymes are green and clean alternatives for several processes in the pulp and paper industry. Enzyme treatment decreases the energy requirement and minimizes the wood losses during drum debarking. Lipophilic wood extractives are known as pitch. Pitch deposition adversely affects the pulp quality and increases equipment maintenance and operating costs during paper manufacturing. Several chemical additives have been used to remove pitch deposits. Natural seasoning of wood is used to minimize pitch content in wood, but it has some disadvantages including yield losses and decreased brightness. Controlled seasoning with white-rot fungi or albino strains of sapstain fungi is an effective tool for degradation and removal of wood extractives. Enzymes including lipase, laccase, sterol esterase, and lipooxygenase have also been used to minimize pitch-related problems. Enzymatic retting has been proved an eco-friendly and economical solution for chemical degumming and traditional retting.

Melatonin as a prospective metabolic regulator in pathologically altered cardiac energy homeostasis

2021 ◽  
Vol 4 (2) ◽  
pp. 316-335
Author(s):  
Swaimanti Sarkar ◽  
Aindrila Chattopadhyay ◽  
Debasish Bandyopadhyay
Keyword(s):  
Oxidative Stress ◽  
Ischemia Reperfusion Injury ◽  
Energy Requirement ◽  
Ischemia Reperfusion ◽  
Cardiac Cells ◽  
Acid Oxidation ◽  
Ros Generation ◽  
Atp Production ◽  
Working Heart

A constant energy supply is indispensable for the relentlessly working heart. The unique metabolic flexibility of the cardiac tissue enables it to maintain its energy requirement under variable physiological conditions. However, some physiopathological statuses including aging, ischemia-reperfusion injury, diabetic cardiomyopathy, pathological cardiac hypertrophy, and heart failure frequently cause cardiac dysfunction and detrimental metabolic alteration. If the ATP supply fails to match the requirement of a working heart, the heart loses its functional capacity, resulting in slower recovery. A decrease in energy generation is often the ramifications of myocardial mitochondrial dysfunction and oxidative stress. Melatonin, a broad-spectrum antioxidant molecule has an appreciable role in the maintenance of metabolic homeostasis― from a single cell to an entire organism. Melatonin has the capacity to reduce ROS generation, preserve mitochondrial stability, and restore a robust mitochondrial function for unabated ATP production in cardiac tissues. Additionally, melatonin can promote carbohydrate and fat metabolism to further improve the ATP production in heart. In cardiac cells, melatonin upregulates GLUT4 expression either by impeding oxidative stress or by enhancing AMPK activation which accelerates fatty acid oxidation by upregulating PPAR-α and CPT-1α. Melatonin plays a pivotal role in the maintenance of calcium homeostasis in cardiomyocytes by obviating oxidative stress-mediated disruption of SERCA and NCX proteins. A possible role of melatonin to convert the Warburg effect to oxidative metabolism in pathological cardiac events has been recently contemplated. The current review will discuss the possible role of melatonin protecting against cardiac metabolic imbalances under pathological states.

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