scholarly journals Effect of pH and Oxalate on Hydroquinone-Derived Hydroxyl Radical Formation during Brown Rot Wood Degradation

2003 ◽  
Vol 69 (10) ◽  
pp. 6025-6031 ◽  
Author(s):  
Elisa Varela ◽  
Ming Tien
Keyword(s):  
Lipid Peroxidation ◽  
Hydroxyl Radical ◽  
Iron Reduction ◽  
Brown Rot ◽  
Radical Formation ◽  
Semiquinone Radical ◽  
Ferric Ion ◽  
Redox Cycle ◽  
Fenton Chemistry ◽  
Effect Of Ph

ABSTRACT The redox cycle of 2,5-dimethoxybenzoquinone (2,5-DMBQ) is proposed as a source of reducing equivalent for the regeneration of Fe2+ and H2O2 in brown rot fungal decay of wood. Oxalate has also been proposed to be the physiological iron reductant. We characterized the effect of pH and oxalate on the 2,5-DMBQ-driven Fenton chemistry and on Fe3+ reduction and oxidation. Hydroxyl radical formation was assessed by lipid peroxidation. We found that hydroquinone (2,5-DMHQ) is very stable in the absence of iron at pH 2 to 4, the pH of degraded wood. 2,5-DMHQ readily reduces Fe3+ at a rate constant of 4.5 × 103 M−1s−1 at pH 4.0. Fe2+ is also very stable at a low pH. H2O2 generation results from the autoxidation of the semiquinone radical and was observed only when 2,5-DMHQ was incubated with Fe3+. Consistent with this conclusion, lipid peroxidation occurred only in incubation mixtures containing both 2,5-DMHQ and Fe3+. Catalase and hydroxyl radical scavengers were effective inhibitors of lipid peroxidation, whereas superoxide dismutase caused no inhibition. At a low concentration of oxalate (50 μM), ferric ion reduction and lipid peroxidation are enhanced. Thus, the enhancement of both ferric ion reduction and lipid peroxidation may be due to oxalate increasing the solubility of the ferric ion. Increasing the oxalate concentration such that the oxalate/ferric ion ratio favored formation of the 2:1 and 3:1 complexes resulted in inhibition of iron reduction and lipid peroxidation. Our results confirm that hydroxyl radical formation occurs via the 2,5-DMBQ redox cycle.

Hydroxyl radical formation from bacteria-assisted Fenton chemistry at neutral pH under environmentally relevant conditions

2016 ◽  
Vol 13 (4) ◽  
pp. 757 ◽  
Author(s):  
Jarod N. Grossman ◽  
Tara F. Kahan
Keyword(s):  
Hydrogen Peroxide ◽  
Hydroxyl Radical ◽  
Natural Waters ◽  
Shewanella Oneidensis ◽  
Radical Formation ◽  
Production Rates ◽  
Fenton Chemistry ◽  
Iron Reducing Bacteria ◽  
Neutral Ph ◽  
Reducing Bacteria

Environmental contextReactions in natural waters such as lakes and streams are thought to be extremely slow in the absence of sunlight (e.g. at night). We demonstrate that in the presence of iron, hydrogen peroxide and certain bacteria (all of which are common in natural waters), certain reactions may occur surprisingly quickly. These findings will help us predict the fate of many compounds, including pollutants, in natural waters at night. AbstractDark Fenton chemistry is an important source of hydroxyl radicals (OH•) in natural waters in the absence of sunlight. Hydroxyl radical production by this process is very slow in many bodies of water, owing to slow reduction and low solubility of FeIII at neutral and near-neutral pH. We have investigated the effects of the iron-reducing bacteria Shewanella oneidensis (SO) on OH• production rates from Fenton chemistry at environmentally relevant hydrogen peroxide (H2O2) and iron concentrations at neutral pH. In the presence of 2.0 × 10–4M H2O2, OH• production rates increased from 1.3 × 10–10 to 2.0 × 10–10Ms–1 in the presence of 7.0 × 106cellsmL–1 SO when iron (at a concentration of 100μM) was in the form of FeII, and from 3.6 × 10–11 to 2.2 × 10–10Ms–1 when iron was in the form of FeIII. This represents rate increases of factors of 1.5 and 6 respectively. We measured OH• production rates at a range of H2O2 concentrations and SO cell densities. Production rates depended linearly on both variables. We also demonstrate that bacteria-assisted Fenton chemistry can result in rapid degradation of aromatic pollutants such as anthracene. Our results suggest that iron-reducing bacteria such as SO may be important contributors to radical formation in dark natural waters.

Fenton chemistry in biology and medicine

2007 ◽  
Vol 79 (12) ◽  
pp. 2325-2338 ◽  
Author(s):  
Josef Prousek
Keyword(s):  
Hydroxyl Radical ◽  
Fenton Reaction ◽  
Brown Rot ◽  
White Rot ◽  
Practical Utilization ◽  
Fenton Chemistry ◽  
Radical Production

Various aspects of the participation of Fenton chemistry in biology and medicine are reviewed. Accumulated evidence shows that both hydroxyl radical and ferryl [Fe(IV)=O]2+ can be formed under a variety of Fenton and Fenton-like reactions. Some examples of metal-independent hydroxyl radical production are included. Extracellular Fenton reaction is illustrated by the white rot and brown rot wood-decaying fungi. The natural and practical utilization of catechol-driven Fenton reaction is also presented.

Iron reduction potentiates hydroxyl radical formation only in flavonols

2012 ◽  
Vol 135 (4) ◽  
pp. 2584-2592 ◽  
Author(s):  
Kateřina Macáková ◽  
Přemysl Mladěnka ◽  
Tomáš Filipský ◽  
Michal Říha ◽  
Luděk Jahodář ◽  
...  
Keyword(s):  
Hydroxyl Radical ◽  
Iron Reduction ◽  
Radical Formation

scholarly journals Pathways for Extracellular Fenton Chemistry in the Brown Rot Basidiomycete Gloeophyllum trabeum

2001 ◽  
Vol 67 (6) ◽  
pp. 2705-2711 ◽  
Author(s):  
Kenneth A. Jensen ◽  
Carl J. Houtman ◽  
Zachary C. Ryan ◽  
Kenneth E. Hammel
Keyword(s):  
Polyethylene Glycol ◽  
Brown Rot ◽  
Redox Cycle ◽  
Gloeophyllum Trabeum ◽  
Fenton Reagent ◽  
Fenton Chemistry ◽  
Brown Rot Fungus ◽  
Predominant Form ◽  
Two Factors ◽  
Oxalate Complexes

ABSTRACT The brown rot fungus Gloeophyllum trabeum uses an extracellular hydroquinone-quinone redox cycle to reduce Fe3+ and produce H2O2. These reactions generate extracellular Fenton reagent, which enablesG. trabeum to degrade a wide variety of organic compounds. We found that G. trabeum secreted two quinones, 2,5-dimethoxy-1,4-benzoquinone (2,5-DMBQ) and 4,5-dimethoxy-1,2-benzoquinone (4,5-DMBQ), that underwent iron-dependent redox cycling. Experiments that monitored the iron- and quinone-dependent cleavage of polyethylene glycol by G. trabeum showed that 2,5-DMBQ was more effective than 4,5-DMBQ in supporting extracellular Fenton chemistry. Two factors contributed to this result. First, G. trabeum reduced 2,5-DMBQ to 2,5-dimethoxyhydroquinone (2,5-DMHQ) much more rapidly than it reduced 4,5-DMBQ to 4,5-dimethoxycatechol (4,5-DMC). Second, although both hydroquinones reduced ferric oxalate complexes, the predominant form of Fe3+ in G. trabeum cultures, the 2,5-DMHQ-dependent reaction reduced O2 more rapidly than the 4,5-DMC-dependent reaction. Nevertheless, both hydroquinones probably contribute to the extracellular Fenton chemistry of G. trabeum, because 2,5-DMHQ by itself is an efficient reductant of 4,5-DMBQ.

Hydroxyl radical formation and lipid peroxidation enhancement by chromium

1992 ◽  
Vol 32 (1-3) ◽  
pp. 161-170 ◽  
Author(s):  
Charles Coudray ◽  
Patrice Faure ◽  
Samar Rachidi ◽  
Andre Jeunet ◽  
Marie Jeanne Richard ◽  
...  
Keyword(s):  
Lipid Peroxidation ◽  
Hydroxyl Radical ◽  
Radical Formation

scholarly journals Lipid peroxidation in electroporated hepatocytes occurs much more readily than does hydroxyl-radical formation

1991 ◽  
Vol 277 (3) ◽  
pp. 767-771 ◽  
Author(s):  
T Hallinan ◽  
J Gor ◽  
C A Rice-Evans ◽  
R Stanley ◽  
R O'Reilly ◽  
...  
Keyword(s):  
Lipid Peroxidation ◽  
Hydroxyl Radical ◽  
Membrane Lipids ◽  
Electron Microscopic Examination ◽  
Radical Formation ◽  
Permeability Barrier ◽  
Redox Systems ◽  
Plasma Membrane Permeability ◽  
Electron Microscopic ◽  
Free Radical Damage

1. Rat hepatocytes suspended in 0.25 M-sucrose were electropermeabilized. This completely disrupted their plasma-membrane permeability barrier. 2. The endoplasmic reticulum in electroporated hepatocytes appeared morphologically preserved and maintained its permeability barrier as evidenced by electron-microscopic examination and latency measurements on luminal reticular enzymes. 3. Upon aerobic incubation with an NADPH-generating system and iron/ADP, porated hepatocytes peroxidized their membrane lipids at rates similar to those of matched microsomal preparations. 4. When hepatocytes were incubated with iron/EDTA and azide, radical formation detectable with dimethyl sulphoxide (DMSO) was only 10-20% that shown by microsomes. Omitting azide abolished hepatocyte reactivity with DMSO completely. Effects of hydroxyl-radical (.OH) scavengers and of added catalase suggest that the radical detected by DMSO is .OH. 5. Cytosolic inhibitor(s) from hepatocytes seemed to be a major factor limiting .OH formation. These were macromolecular, but showed a degree of heat-stability. Dialysis largely abolished inhibition, but this could be restored again by adding GSH. 6. Since .OH formation in hepatocytes seems to be much more stringently prevented than lipid peroxidation, free-radical damage originating from intracellular redox systems seems more likely to take the form of lipid peroxidation.

Sign in / Sign up

Export Citation Format

Share Document