Photochemical Oxidation of Water by 2-Methyl-1,4-benzoquinone:  Evidence against the Formation of Free Hydroxyl Radical

The effect of complex formation on the oxidation of substrate in the Fe2+-H2O2 system has been studied. t-Butyl alcohol which is normally oxidized to the dimer, 2,5-dimethylhexane-2,5-diol, by Fenton's reagent has been used as a probe for the presence of free hydroxyl radical. �� It is shown that when suitable complexes are formed substrates are not oxidized by free hydroxyl radical. Instead, new mechanisms involving one- and two-electron transfers within a substrate-ferrous ion-peroxide complex are proposed.

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Improvements in Functionalities of Porcine Serum Protein Hydrolysates Induced by Free Hydroxyl Radical

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.554-556.1487 ◽

2012 ◽

Vol 554-556 ◽

pp. 1487-1492

Author(s):

He Hong Yang ◽

Pei Jun Li ◽

Bao Hua Kong ◽

Yan Qing Li ◽

Ju Yang Zhao ◽

...

Keyword(s):

Hydroxyl Radical ◽

Functional Properties ◽

Plasma Protein ◽

Food Systems ◽

Activity Index ◽

Early Stage ◽

Protein Hydrolysates ◽

Free Hydroxyl ◽

Foaming Capacity ◽

Mediated Oxidation

Hydrolysated peptides from kinds of proteins have been applied as natural ingredients in food industry, mainly due to their good functional properties. However, the fate of them under different processing conditions is rarely understood. In our study, changes of functional properties in porcine plasma protein hydrolysates (PPH) were evaluated in a free hydroxyl radical-mediated oxidation system. PPH was obtained by hydrolyzing porcine plasma protein with Alcalase for 5 h at pH 8.0, 55°C. When exposed to free radical-mediated oxidation, functional properties of PPH improved dramatically with growing oxidant concentrations and reaction time, especially at 20°C. Solubility, foaming capacity and emulsification of PPH increased significantly (P < 0.05) during early stage of oxidation, with solubility increasing from 83.1% (non-oxidized PPH) to 97.4%(20°C, 10mM H2OSubscript text2, 5 h), emulsifying activity index and foaming capacity rising form 1.24m2/g to 2.73 m2/g, and 144% to183%, respectively. Stability for emulsifying and foaming were also found to be reinforced. The improvements in functional properties of PPH helped to play theoretical basis for applying the peptides in food systems.

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Free hydroxyl radical is not involved in an important reaction of lignin degradation by Phanerochaete chrysosporium Burds

Biochemical Journal ◽

10.1042/bj2260455 ◽

1985 ◽

Vol 226 (2) ◽

pp. 455-460 ◽

Cited By ~ 39

Author(s):

T K Kirk ◽

M D Mozuch ◽

M Tien

Keyword(s):

Hydroxyl Radical ◽

Phanerochaete Chrysosporium ◽

Fenton Reaction ◽

Lignin Degradation ◽

Mechanism Of Formation ◽

Mass Spectral ◽

Free Hydroxyl ◽

Lignin Model ◽

Trapping Agent ◽

Fenton System

Hydroxyl radical (HO.) has been implicated in the degradation of lignin by Phanerochaete chrysosporium. This study assessed the possible involvement of HO. in degradation of lignin substructural models by intact cultures and by an extracellular ligninase isolated from the cultures. Two non-phenolic lignin model compounds [aryl-C(alpha)HOH-C(beta)HR-C(gamma)H2OH, in which R = aryl (beta-1) or R = O-aryl (beta-O-4)] were degraded by cultures, by the purified ligninase, and by Fenton's reagent (H2O2 + Fe2+), which generates HO. The ligninase and the cultures formed similar products, derived via an initial cleavage between C(alpha) and C(beta) (known to be an important biodegradative reaction), indicating that the ligninase is responsible for model degradation in cultures. Products from the Fenton degradation were mainly polar phenolics that exhibited little similarity to those from the biological systems. Mass-spectral analysis, however, revealed traces of the same products in the Fenton reaction as seen in the biological reactions; even so, an 18O2-incorporation study showed that the mechanism of formation differed. E.s.r. spectroscopy with a spin-trapping agent readily detected HO. in the Fenton system, but indicated that no HO. is formed during ligninase catalysis. We conclude, therefore that HO. is not involved in fungal C(alpha)-C(beta) cleavage in the beta-1 and beta-O-4 models and, by extension, in the same reaction in lignin.

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