Hydroxyl radical buffered by isoprene oxidation over tropical forests

2012 ◽  
Vol 5 (3) ◽  
pp. 190-193 ◽  
Author(s):  
D. Taraborrelli ◽  
M. G. Lawrence ◽  
J. N. Crowley ◽  
T. J. Dillon ◽  
S. Gromov ◽  
...  
Keyword(s):  
Hydroxyl Radical ◽  
Tropical Forests ◽  
Isoprene Oxidation

scholarly journals Erratum: Hydroxyl radical buffered by isoprene oxidation over tropical forests

2012 ◽  
Vol 5 (4) ◽  
pp. 300-300 ◽  
Author(s):  
D. Taraborrelli ◽  
M. G. Lawrence ◽  
J. N. Crowley ◽  
T. J. Dillon ◽  
S. Gromov ◽  
...  
Keyword(s):  
Hydroxyl Radical ◽  
Tropical Forests ◽  
Isoprene Oxidation

Hydroxyl Radical Recycling in Isoprene Oxidation Driven by Hydrogen Bonding and Hydrogen Tunneling: The Upgraded LIM1 Mechanism

2014 ◽  
Vol 118 (38) ◽  
pp. 8625-8643 ◽  
Author(s):  
Jozef Peeters ◽  
Jean-François Müller ◽  
Trissevgeni Stavrakou ◽  
Vinh Son Nguyen
Keyword(s):  
Hydrogen Bonding ◽  
Hydroxyl Radical ◽  
Hydrogen Tunneling ◽  
Isoprene Oxidation

scholarly journals The role of boundary layer dynamics on the diurnal evolution of isoprene and the hydroxyl radical over tropical forests

2011 ◽  
Vol 116 (D7) ◽  
Author(s):  
Jordi Vilà-Guerau de Arellano ◽  
Edward G. Patton ◽  
Thomas Karl ◽  
Kees van den Dries ◽  
Mary C. Barth ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Hydroxyl Radical ◽  
Tropical Forests ◽  
Boundary Layer Dynamics

scholarly journals OH reactivity in a South East Asian tropical rainforest during the Oxidant and Particle Photochemical Processes (OP3) project

2013 ◽  
Vol 13 (18) ◽  
pp. 9497-9514 ◽  
Author(s):  
P. M. Edwards ◽  
M. J. Evans ◽  
K. L. Furneaux ◽  
J. Hopkins ◽  
T. Ingham ◽  
...  
Keyword(s):  
Hydroxyl Radical ◽  
Tropical Rainforest ◽  
Primary Source ◽  
Oxidation Products ◽  
Chemical Mechanism ◽  
Large Variability ◽  
Photochemical Processes ◽  
Radical Reactivity ◽  
Isoprene Oxidation ◽  
Isoprene Oxidation Products

Abstract. OH (hydroxyl radical) reactivity, the inverse of the chemical lifetime of the hydroxyl radical, was measured for 12 days in April 2008 within a tropical rainforest on Borneo as part of the OP3 (Oxidant and Particle Photochemical Processes) project. The maximum observed value was 83.8 ± 26.0 s−1 with the campaign averaged noontime maximum being 29.1 ± 8.5 s−1. The maximum OH reactivity calculated using the diurnally averaged concentrations of observed sinks was ~ 18 s−1, significantly less than the observations, consistent with other studies in similar environments. OH reactivity was dominated by reaction with isoprene (~ 30%). Numerical simulations of isoprene oxidation using the Master Chemical Mechanism (v3.2) in a highly simplified physical and chemical environment show that the steady state OH reactivity is a linear function of the OH reactivity due to isoprene alone, with a maximum multiplier, to account for the OH reactivity of the isoprene oxidation products, being equal to the number of isoprene OH attackable bonds (10). Thus the emission of isoprene constitutes a significantly larger emission of reactivity than is offered by the primary reaction with isoprene alone, with significant scope for the secondary oxidation products of isoprene to constitute the observed missing OH reactivity. A physically and chemically more sophisticated simulation (including physical loss, photolysis, and other oxidants) showed that the calculated OH reactivity is reduced by the removal of the OH attackable bonds by other oxidants and photolysis, and by physical loss (mixing and deposition). The calculated OH reactivity is increased by peroxide cycling, and by the OH concentration itself. Notable in these calculations is that the accumulated OH reactivity from isoprene, defined as the total OH reactivity of an emitted isoprene molecule and all of its oxidation products, is significantly larger than the reactivity due to isoprene itself and critically depends on the chemical and physical lifetimes of intermediate species. When constrained to the observed diurnally averaged concentrations of primary VOCs (volatile organic compounds), O3, NOx and other parameters, the model underestimated the observed diurnal mean OH reactivity by 30%. However, it was found that (1) the short lifetimes of isoprene and OH, compared to those of the isoprene oxidation products, lead to a large variability in their concentrations and so significant variation in the calculated OH reactivity; (2) uncertainties in the OH chemistry in these high isoprene environments can lead to an underestimate of the OH reactivity; (3) the physical loss of species that react with OH plays a significant role in the calculated OH reactivity; and (4) a missing primary source of reactive carbon would have to be emitted at a rate equivalent to 50% that of isoprene to account for the missing OH sink. Although the presence of unmeasured primary emitted VOCs contributing to the measured OH reactivity is likely, evidence that these primary species account for a significant fraction of the unmeasured reactivity is not found. Thus the development of techniques for the measurement of secondary multifunctional carbon compounds is needed to close the OH reactivity budget.

Experimental evidence for efficient hydroxyl radical regeneration in isoprene oxidation

2013 ◽  
Vol 6 (12) ◽  
pp. 1023-1026 ◽  
Author(s):  
H. Fuchs ◽  
A. Hofzumahaus ◽  
F. Rohrer ◽  
B. Bohn ◽  
T. Brauers ◽  
...  
Keyword(s):  
Hydroxyl Radical ◽  
Experimental Evidence ◽  
Isoprene Oxidation

Activation of cytochrome c to a peroxidase compound I-type intermediate by H2O2: relevance to redox signalling in apoptosis

2004 ◽  
Vol 71 ◽  
pp. 97-106 ◽  
Author(s):  
Mark Burkitt ◽  
Clare Jones ◽  
Andrew Lawrence ◽  
Peter Wardman
Keyword(s):  
Cytochrome C ◽  
Hydroxyl Radical ◽  
Redox Regulation ◽  
Chemotherapeutic Agents ◽  
Tyrosyl Radical ◽  
Compound I ◽  
Definitive Evidence ◽  
Enhanced Production ◽  
Physico Chemical

The release of cytochrome c from mitochondria during apoptosis results in the enhanced production of superoxide radicals, which are converted to H2O2 by Mn-superoxide dismutase. We have been concerned with the role of cytochrome c/H2O2 in the induction of oxidative stress during apoptosis. Our initial studies showed that cytochrome c is a potent catalyst of 2′,7′-dichlorofluorescin oxidation, thereby explaining the increased rate of production of the fluorophore 2′,7′-dichlorofluorescein in apoptotic cells. Although it has been speculated that the oxidizing species may be a ferryl-haem intermediate, no definitive evidence for the formation of such a species has been reported. Alternatively, it is possible that the hydroxyl radical may be generated, as seen in the reaction of certain iron chelates with H2O2. By examining the effects of radical scavengers on 2′,7′-dichlorofluorescin oxidation by cytochrome c/H2O2, together with complementary EPR studies, we have demonstrated that the hydroxyl radical is not generated. Our findings point, instead, to the formation of a peroxidase compound I species, with one oxidizing equivalent present as an oxo-ferryl haem intermediate and the other as the tyrosyl radical identified by Barr and colleagues [Barr, Gunther, Deterding, Tomer and Mason (1996) J. Biol. Chem. 271, 15498-15503]. Studies with spin traps indicated that the oxo-ferryl haem is the active oxidant. These findings provide a physico-chemical basis for the redox changes that occur during apoptosis. Excessive changes (possibly catalysed by cytochrome c) may have implications for the redox regulation of cell death, including the sensitivity of tumour cells to chemotherapeutic agents.

Tropical Forests

1921 ◽  
Vol 3 (3supp) ◽  
pp. 267-270
Author(s):  
Vernon Kellogg ◽  
R. M. Yerkes ◽  
H. E. Howe
Keyword(s):  
Tropical Forests

Valuing Tropical Forests

1995 ◽  
Author(s):  
Randall A. Kramer ◽  
narendra Sharma ◽  
Mohan Munasinghe
Keyword(s):  
Tropical Forests
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