scholarly journals Photochemistry of the Cloud Aqueous Phase: A Review

Molecules ◽  
2020 ◽  
Vol 25 (2) ◽  
pp. 423
Author(s):  
Angelica Bianco ◽  
Monica Passananti ◽  
Marcello Brigante ◽  
Gilles Mailhot
Keyword(s):  
Hydrogen Peroxide ◽  
Hydroxyl Radical ◽  
Aqueous Phase ◽  
Review Paper ◽  
Formation Rate ◽  
Nitrate Radical ◽  
Steady State Concentration ◽  
Potential Impact ◽  
State Concentration

This review paper describes briefly the cloud aqueous phase composition and deeply its reactivity in the dark and mainly under solar radiation. The role of the main oxidants (hydrogen peroxide, nitrate radical, and hydroxyl radical) is presented with a focus on the hydroxyl radical, which drives the oxidation capacity during the day. Its sources in the aqueous phase, mainly through photochemical mechanisms with H2O2, iron complexes, or nitrate/nitrite ions, are presented in detail. The formation rate of hydroxyl radical and its steady state concentration evaluated by different authors are listed and compared. Finally, a paragraph is also dedicated to the sinks and the reactivity of the HO• radical with the main compounds found in the cloud aqueous phase. This review presents an assessment of the reactivity in the cloud aqueous phase and shows the significant potential impact that this medium can have on the chemistry of the atmosphere and more generally on the climate.

The chemistry of lipid alkoxyl radicals and their role in metal-amplified lipid peroxidation

1995 ◽  
Vol 61 ◽  
pp. 65-72 ◽  
Author(s):  
Lawrence J. Marnett ◽  
Allan L. Wilcox
Keyword(s):  
Lipid Peroxidation ◽  
Steady State ◽  
Fatty Acid ◽  
Hydroxyl Radical ◽  
Metal Complexes ◽  
Polyunsaturated Fatty Acid ◽  
Ring Opening ◽  
Steady State Concentration ◽  
State Concentration ◽  
Fatty Acid Hydroperoxides

Reaction of polyunsaturated fatty acid hydroperoxides with metal complexes generates lipid alkoxyl radicals and metal-oxo complexes. Lipid alkoxyl radicals are presumed to be the species responsible for metal-amplified lipid peroxidation because of the chemical analogy of simple organic alkoxyl radicals to the hydroxyl radical. However, polyunsaturated fatty acid alkoxyl radicals exhibit a rich and diverse chemistry that is dominated by intramolecular cyclization to epoxyallylic radicals. Studies described herein demonstrate that the equilibrium between cyclization and ring-opening of epoxyallylic radicals lies overwhelmingly toward cyclization. Thus lipid alkoxyl radicals have a steady-state concentration that is so low that their contribution to metal-amplified lipid peroxidation is insignificant. In fact, the species responsible for metal amplification of lipid peroxidation appears to be the epoxyperoxyl radical formed by coupling the epoxyallylic radical to molecular oxygen.

Role of the Smoking-Induced Cytochrome P450 (CYP)1A2 and Polymorphic CYP2D6 in Steady-State Concentration of Olanzapine

2003 ◽  
Vol 23 (2) ◽  
pp. 119-127 ◽  
Author(s):  
Juan Antonio Carrillo ◽  
Angustias G. Herráiz ◽  
Sara Isabel Ramos ◽  
Guillermo Gervasini ◽  
Sonia Vizcaíno ◽  
...  
Keyword(s):  
Cytochrome P450 ◽  
Steady State ◽  
Steady State Concentration ◽  
Cyp 1A2 ◽  
State Concentration

Osmotic Adaption in the Marine Alga Griffithsia monilis (Rhodophyceae): The Role of Ions and Organic Compounds

1979 ◽  
Vol 6 (4) ◽  
pp. 523 ◽  
Author(s):  
M.A Bisson ◽  
G.O Kirst
Keyword(s):  
Steady State ◽  
Osmotic Pressure ◽  
Marine Alga ◽  
Turgor Pressure ◽  
Red Alga ◽  
Steady State Concentration ◽  
Photosynthetic Product ◽  
The Individual ◽  
State Concentration

The red alga G. monilis maintains its turgor pressure constant at 4.05 � 0.14 x 10*5 Pa (179 measurements), or 166 mosmol/kg, over a range of external osmotic pressures from 900 to 1300 mosmol/kg. It is capable of regulating turgor pressure in the dark or when sorbitol is used to increase the external osmotic pressure. Complete regulation of turgor requires 24-36 h, although much of the regulation is accomplished in the first 2 h. The change in II*i is achieved by controlling the concentrations of K+, Na+, and Cl-. In the vacuole, KCl concentration is higher than NaCl, and KCI is usually more important than NaCl in regulating turgor, although the importance of the individual cations varies with specific conditions. The steady-state concentration of the principal photosynthetic product, digeneaside, increases with increasing external osmotic pressure. Its concentration is too low to affect the internal osmotic pressure if it is distributed evenly throughout the cell but, if it is restricted to the cytoplasm, it can play a major role in regulating the volume of the cytoplasm.

scholarly journals Dual Role of ROS as Signal and Stress Agents: Iron Tips the Balance in favor of Toxic Effects

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Elena Gammella ◽  
Stefania Recalcati ◽  
Gaetano Cairo
Keyword(s):  
Reactive Oxygen Species ◽  
Hydrogen Peroxide ◽  
Oxidative Damage ◽  
Cell Signaling ◽  
Hydroxyl Radical ◽  
Iron Homeostasis ◽  
Storage Proteins ◽  
Oxygen Species ◽  
Physiologic Role

Iron is essential for life, while also being potentially harmful. Therefore, its level is strictly monitored and complex pathways have evolved to keep iron safely bound to transport or storage proteins, thereby maintaining homeostasis at the cellular and systemic levels. These sequestration mechanisms ensure that mildly reactive oxygen species like anion superoxide and hydrogen peroxide, which are continuously generated in cells living under aerobic conditions, keep their physiologic role in cell signaling while escaping iron-catalyzed transformation in the highly toxic hydroxyl radical. In this review, we describe the multifaceted systems regulating cellular and body iron homeostasis and discuss how altered iron balance may lead to oxidative damage in some pathophysiological settings.

scholarly journals Yields of hydrogen peroxide from the reaction of hydroxyl radical with organic compounds in solution and ice

2011 ◽  
Vol 11 (14) ◽  
pp. 7209-7222 ◽  
Author(s):  
T. Hullar ◽  
C. Anastasio
Keyword(s):  
Hydrogen Peroxide ◽  
Hydroxyl Radical ◽  
Organic Compounds ◽  
Octanoic Acid ◽  
Formation Rate ◽  
Peroxyl Radicals ◽  
Water Control ◽  
Organic Species ◽  
Simulated Solar Light ◽  
Octanedioic Acid

Abstract. Hydrogen peroxide (HOOH) is a significant oxidant in atmospheric condensed phases (e.g., cloud and fog drops, aqueous particles, and snow) that also photolyzes to form hydroxyl radical (•OH). •OH can react with organics in aqueous phases to form organic peroxyl radicals and ultimately reform HOOH, but the efficiency of this process in atmospheric aqueous phases, as well as snow and ice, is not well understood. We investigate HOOH formation from •OH attack on 10 environmentally relevant organic compounds: formaldehyde, formate, glycine, phenylalanine, benzoic acid, octanol, octanal, octanoic acid, octanedioic acid, and 2-butoxyethanol. Liquid and ice samples with and without nitrate (as an •OH source) were illuminated using simulated solar light, and HOOH formation rates were measured as a function of pH and temperature. For most compounds, the formation rate of HOOH without nitrate was the same as the background formation rate in blank water (i.e., illumination of the organic species does not produce HOOH directly), while formation rates with nitrate were greater than the water control (i.e., reaction of •OH with the organic species forms HOOH). Yields of HOOH, defined as the rate of HOOH production divided by the rate of •OH production, ranged from essentially zero (glycine) to 0.24 (octanal), with an average of 0.12 ± 0.05 (95 % CI). HOOH production rates and yields were higher at lower pH values. There was no temperature dependence of the HOOH yield for formaldehyde or octanedioic acid between −5 to 20 °C and ice samples had approximately the same HOOH yield as the aqueous solutions. In contrast, HOOH yields in formate solutions were higher at 5 and 10 °C compared to −5 and 20 °C. Yields of HOOH in ice for solutions containing nitrate and either phenylalanine, benzoate, octanal, or octanoic acid were indistinguishable from zero. Our HOOH yields were approximately half those found in previous studies conducted using γ-radiolysis, but this difference might be due to the much lower (and more environmentally relevant) •OH formation rates in our experiments.

Role of hydrogen peroxide and hydroxyl radical in pyrite oxidation by molecular oxygen

2010 ◽  
Vol 74 (17) ◽  
pp. 4971-4987 ◽  
Author(s):  
Martin A.A. Schoonen ◽  
Andrea D. Harrington ◽  
Richard Laffers ◽  
Daniel R. Strongin
Keyword(s):  
Hydrogen Peroxide ◽  
Hydroxyl Radical ◽  
Molecular Oxygen ◽  
Pyrite Oxidation ◽  
Oxidation By Molecular Oxygen
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