EPR Evidence for hydroxyl- and substrate-derived radicals in Fe(II)-oxalate/hydrogen peroxide reactions. The importance of the reduction of Fe(III)-oxalate by oxygen-conjugated radicals to regenerate Fe(II) in reactions of carbohydrates and model compounds

Park, Jonathan S. B.; Wood, Paul M.; Gilbert, Bruce C.; Whitwood, Adrian C.

doi:10.1039/a900882i

Cited by 18 publications

(6 citation statements)

References 12 publications

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“…The g factor of the F [CA-CNC] 3 film was 2.0030. These g values match those described in the literature for phenoxy radicals, and the difference in the measurements depends on the protonation of the radical …”

Section: Resultssupporting

confidence: 87%

“…The g factor of the F [CA-CNC] 3 film was 2.0030. These g values match those described in the literature for phenoxy radicals, 68 and the difference in the measurements depends on the protonation of the radical. 69 The amplitude of the EPR signal was proportional to the mass of the film introduced in the EPR tube, which confirmed the homogeneous distribution of phenoxy radicals in the films.…”

Section: Dpphsupporting

confidence: 87%

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Dual Antioxidant Properties and Organic Radical Stabilization in Cellulose Nanocomposite Films Functionalized by In Situ Polymerization of Coniferyl Alcohol

et al. 2020

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A new biobased material based on an original strategy using lignin model compounds as natural grafting additive on a nanocellulose surface through in situ polymerization of coniferyl alcohol by the Fenton reaction at two pH values was investigated. The structural and morphological properties of the materials at the nanoscale were characterized by a combination of analytical methods, including Fourier transform infrared spectroscopy, liquid chromatography combined with mass spectrometry, nuclear molecular resonance spectroscopy, electron paramagnetic resonance spectroscopy, water sorption capacity by dynamic vapor sorption, and atomic force microscopy (topography and indentation modulus measurements). Finally, the usage properties, such as antioxidant properties, were evaluated in solution and the nanostructured casted films by radical 2,2′-diphenyl-1-picrylhydrazyl (DPPH•) scavenging tests. We demonstrate the structure–function relationships of these advanced CNC-lignin films and describe their dual functionalities and characteristics, namely, their antioxidant properties and the presence of persistent phenoxy radicals within the material.

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Section: Resultssupporting

confidence: 87%

Section: Dpphsupporting

confidence: 87%

Dual Antioxidant Properties and Organic Radical Stabilization in Cellulose Nanocomposite Films Functionalized by In Situ Polymerization of Coniferyl Alcohol

et al. 2020

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“…A mechanism of CDH participation in the Fenton reaction has been proposed for the brown rot fungus Coniophora puteana (Hyde & Wood, 1997) in wood containing oxalic acid which strongly chelates Fe 31 and Fe 21 (Espejo & Agosin, 1991). The redox properties of Fe-oxalate complexes can have a large influence on Fenton chemistry (Hyde & Wood, 1997;Park et al, 1997Park et al, , 1999. CDH can reduce Fe 31oxalate effectively only at pH values below c. 2.5, where it is present as Fe 31 -dioxalate, because the reduction potential of the Fe 31 -trioxalate complex that predominates above this pH is too negative.…”

Section: Oxidative Decomposition Of Cellulosementioning

confidence: 99%

Degradation of cellulose by basidiomycetous fungi

2008

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Cellulose is the main polymeric component of the plant cell wall, the most abundant polysaccharide on Earth, and an important renewable resource. Basidiomycetous fungi belong to its most potent degraders because many species grow on dead wood or litter, in environment rich in cellulose. Fungal cellulolytic systems differ from the complex cellulolytic systems of bacteria. For the degradation of cellulose, basidiomycetes utilize a set of hydrolytic enzymes typically composed of endoglucanase, cellobiohydrolase and beta-glucosidase. In some species, the absence of cellobiohydrolase is substituted by the production of processive endoglucanases combining the properties of both of these enzymes. In addition, systems producing hydroxyl radicals based on cellobiose dehydrogenase, quinone redox cycling or glycopeptide-based Fenton reaction are involved in the degradation of several plant cell wall components, including cellulose. The complete cellulolytic complex used by a single fungal species is typically composed of more than one of the above mechanisms that contribute to the utilization of cellulose as a source of carbon or energy or degrade it to ensure fast substrate colonization. The efficiency and regulation of cellulose degradation differs among wood-rotting, litter-decomposing, mycorrhizal or plant pathogenic fungi and yeasts due to the different roles of cellulose degradation in the physiology and ecology of the individual groups.

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“…Both formic and glycolic acid were found when acetic acid was oxidized by Fenton's reagent (Almkvist and Persson 2008b). Oxalic acid can reduce F e (III) ions to F e (II) ions and is proposed as a promoter for Fenton-type of reactions (Park et al 1999). The relatively high concentration observed and its low pK a values (1.2 and 4.2) (Serjeant and Dempsey 1979) show that oxalic acid is the main contributor to the low pH values monitored (see below).…”

Section: Increased Concentration Of Low-molecular Acidsmentioning

confidence: 99%

Analysis of acids and degradation products related to iron and sulfur in the Swedish warship Vasa

Almkvist

Persson

2008

HFSG

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Aqueous wood extracts from the historic Swedish warship Vasa have been analyzed by 1 H-NMR spectroscopy, ion chromatography, and matrix assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry as part of studies on the chemical degradation related to increased levels of iron and sulfur. The results show that low molecular organic acids have accumulated in the Vasa wood after the 1961 salvage. The increased acidity was found in a context of chemical degradation of the wood polymers and the conservation agent polyethylene glycol (PEG) in iron-rich parts of the timber. Formic, glycolic and oxalic acid are all possible endproducts of oxidative degradation of wood polymers, whereas hydrolysis of acetyl groups in xylan may have contributed to increased concentrations of acetic acid. MALDI-TOF spectra of PEG displaced towards lowmolecular PEG oligomers, as reported earlier, were accompanied by increased levels of formic acid, indicating oxidative degradation of PEG. PEG with a carboxylic acid end group (PEGC) was observed to a minor degree in the wood. However, analysis of stored conservation treatment solutions showed high concentrations of PEGC yielding significant contributions to the acidity during the 1960s conservation period. PEGC was probably formed as a result of microbial processes during the early conservation regime. Calculations using concentrations and well-established acidity constants show that oxalic and formic acid are the primary contributors to a low pH in the wood. The increased acidity in the interior of the wood was found in the absence of sulfur compounds but in a context of iron. The majority of the sub-samples with significant levels of sulfate in the surface region with a prospective sulfur oxidation, however, showed neither a decreased pH nor significant depolymerization. This indicates that oxidation pathways of organically bound sulfur do not necessarily produce strong acids, and thereby free protons, as the final product. These observations imply opposing effects of iron and reduced sulfur species, with iron acting as a initiator in oxidative reactions of Fenton type, whereas the reduced organic sulfur compounds may act as anti-oxidants.

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EPR Evidence for hydroxyl- and substrate-derived radicals in Fe(II)-oxalate/hydrogen peroxide reactions. The importance of the reduction of Fe(III)-oxalate by oxygen-conjugated radicals to regenerate Fe(II) in reactions of carbohydrates and model compounds

Cited by 18 publications

References 12 publications

Dual Antioxidant Properties and Organic Radical Stabilization in Cellulose Nanocomposite Films Functionalized by In Situ Polymerization of Coniferyl Alcohol

Dual Antioxidant Properties and Organic Radical Stabilization in Cellulose Nanocomposite Films Functionalized by In Situ Polymerization of Coniferyl Alcohol

Degradation of cellulose by basidiomycetous fungi

Analysis of acids and degradation products related to iron and sulfur in the Swedish warship Vasa

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