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

1985 ◽  
Vol 226 (2) ◽  
pp. 455-460 ◽  
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.

scholarly journals Generation of *OH initiated by interaction of Fe2+ and Cu+ with dioxygen; comparison with the Fenton chemistry.

2000 ◽  
Vol 47 (4) ◽  
pp. 951-962 ◽  
Author(s):  
N K Urbański ◽  
A Beresewicz
Keyword(s):  
Superoxide Dismutase ◽  
Hydroxyl Radical ◽  
Fenton Reaction ◽  
Copper Toxicity ◽  
Reducing Agents ◽  
H2o2 Concentration ◽  
Fenton Chemistry ◽  
Fenton System ◽  
Krebs Henseleit Buffer

Iron and copper toxicity has been presumed to involve the formation of hydroxyl radical (*OH) from H2O2 in the Fenton reaction. The aim of this study was to verify that Fe2+-O2 and Cu+-O2 chemistry is capable of generating *OH in the quasi physiological environment of Krebs-Henseleit buffer (KH), and to compare the ability of the Fe2+-O2 system and of the Fenton system (Fe2+ + H2O2) to produce *OH. The addition of Fe2+ and Cu+ (0-20 microM) to KH resulted in a concentration-dependent increase in *OH formation, as measured by the salicylate method. While Fe3+ and Cu2+ (0-20 microM) did not result in *OH formation, these ions mediated significant *OH production in the presence of a number of reducing agents. The *OH yield from the reaction mediated by Fe2+ was increased by exogenous Fe3+ and Cu2+ and was prevented by the deoxygenation of the buffer and reduced by superoxide dismutase, catalase, and desferrioxamine. Addition of 1 microM, 5 microM or 10 microM Fe2+ to a range of H2O2 concentrations (the Fenton system) resulted in a H2O2-concentration-dependent rise in *OH formation. For each Fe2+ concentration tested, the *OH yield doubled when the ratio [H2O2]:[Fe2+] was raised from zero to one. (i) Fe2+-O2 and Cu+-O2 chemistry is capable of promoting *OH generation in the environment of oxygenated KH, in the absence of pre-existing superoxide and/or H2O2, and possibly through a mechanism initiated by the metal autoxidation; (ii) The process is enhanced by contaminating Fe3+ and Cu2+; (iii) In the presence of reducing agents also Fe3+ and Cu2+ promote the *OH formation; (iv) Depending on the actual [H2O2]:[Fe2+] ratio, the efficiency of the Fe2+-O2 chemistry to generate *OH is greater than or, at best, equal to that of the Fe2+-driven Fenton reaction.

A Systematic DFT Study of Two Elementary Steps Involving Hydrogen Peroxide and the Hydroxyl Radical in the Fenton Reaction

2018 ◽  
Author(s):  
Danilo Carmona ◽  
David Contreras ◽  
Oscar A. Douglas-Gallardo ◽  
Stefan Vogt-Geisse ◽  
Pablo Jaque ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Hydroxyl Radical ◽  
Ab Initio ◽  
Fenton Reaction ◽  
Basis Set ◽  
Basis Sets ◽  
Dft Methods ◽  
Elementary Steps ◽  
Oxygen Oxygen ◽  
Complete Basis Set

The Fenton reaction plays a central role in many chemical and biological processes and has various applications as e.g. water remediation. The reaction consists of the iron-catalyzed homolytic cleavage of the oxygen-oxygen bond in the hydrogen peroxide molecule and the reduction of the hydroxyl radical. Here, we study these two elementary steps with high-level ab-initio calculations at the complete basis set limit and address the performance of different DFT methods following a specific classification based on the Jacob´s ladder in combination with various Pople's basis sets. Ab-initio calculations at the complete basis set limit are in agreement to experimental reference data and identified a significant contribution of the electron correlation energy to the bond dissociation energy (BDE) of the oxygen-oxygen bond in hydrogen peroxide and the electron affinity (EA) of the hydroxyl radical. The studied DFT methods were able to reproduce the ab-initio reference values, although no functional was particularly better for both reactions. The inclusion of HF exchange in the DFT functionals lead in most cases to larger deviations, which might be related to the poor description of the two reactions by the HF method. Considering the computational cost, DFT methods provide better BDE and EA values than HF and post--HF methods with an almost MP2 or CCSD level of accuracy. However, no systematic general prediction of the error based on the employed functional could be established and no systematic improvement with increasing the size in the Pople's basis set was found, although for BDE values certain systematic basis set dependence was observed. Moreover, the quality of the hydrogen peroxide, hydroxyl radical and hydroxyl anion structures obtained from these functionals was compared to experimental reference data. In general, bond lengths were well reproduced and the error in the angles were between one and two degrees with some systematic trend with the basis sets. From our results we conclude that DFT methods present a computationally less expensive alternative to describe the two elementary steps of the Fenton reaction. However, choice of approximated functionals and basis sets must be carefully done and the provided benchmark allows a systematic validation of the electronic structure method to be employed

A Novel pH-responsive Fe-MOF System for Enhanced Cancer Treatment Mediated by Fenton Reaction

2021 ◽  
Author(s):  
Senlin Wang ◽  
Hong-Shuai Wu ◽  
Kai Sun ◽  
Jinzhong Hu ◽  
Fanghui Chen ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Hydroxyl Radical ◽  
Cancer Treatment ◽  
Cell Apoptosis ◽  
Fenton Reaction ◽  
Reactive Oxygen ◽  
Cationic Polymer ◽  
Intracellular Reactive Oxygen Species ◽  
Oxygen Species ◽  
Ph Responsive

Recently, the toxic hydroxyl radical (·OH) has received wide interest in inducing cell apoptosis by increasing the intracellular reactive oxygen species (ROS) levels. Herein, a cationic polymer (MV-PAH) was rationally...

scholarly journals Enhancement of Iron-Based Photo-Driven Processes by the Presence of Catechol Moieties

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 372
Author(s):  
Javier Moreno-Andrés ◽  
Iván Vallés ◽  
Paula García-Negueroles ◽  
Lucas Santos-Juanes ◽  
Antonio Arques
Keyword(s):  
Fenton Reaction ◽  
Advanced Oxidation Processes ◽  
Salt Water ◽  
Degradation Process ◽  
Contaminants Of Emerging Concern ◽  
Low Salt ◽  
Aquaculture Industry ◽  
Iron Based ◽  
Ph Range ◽  
Fenton System

Photo-induced Advanced Oxidation Processes (AOPs) using H2O2 or S2O82− as radical precursors were assessed for the abatement of six different contaminants of emerging concern (CECs). In order to increase the efficiency of these AOPs at a wider pH range, the catechol organic functional compound was studied as a potential assistant in photo-driven iron-based processes. Different salinity regimes were also studied (in terms of Cl− concentration), namely low salt water (1 g·L−1) or a salt–water (30 g·L−1) matrix. Results obtained revealed that the presence of catechol could efficiently assist the photo-Fenton system and partly promote the photo-induced S2O82− system, which was highly dependent on salinity. Regarding the behavior of individual CECs, the photo-Fenton reaction was able to enhance the degradation of all six CECs, meanwhile the S2O82−-based process showed a moderate enhancement for acetaminophen, amoxicillin or clofibric acid. Finally, a response-surface methodology was employed to determine the effect of pH and catechol concentration on the different photo-driven processes. Catechol was removed during the degradation process. According to the results obtained, the presence of catechol in organic macromolecules can bring some advantages in water treatment for either freshwater (wastewater) or seawater (maritime or aquaculture industry).

scholarly journals Involvement of a local Fenton reaction in the reciprocal modulation by O2 of the glucagon-dependent activation of the phosphoenolpyruvate carboxykinase gene and the insulin-dependent activation of the glucokinase gene in rat hepatocytes

1998 ◽  
Vol 335 (2) ◽  
pp. 425-432 ◽  
Author(s):  
Thomas KIETZMANN ◽  
Torsten PORWOL ◽  
Karl ZIEROLD ◽  
Kurt JUNGERMANN ◽  
Helmut ACKER
Keyword(s):  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
Fenton Reaction ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Gene Activation ◽  
Three Dimensional ◽  
Rat Hepatocytes ◽  
Confocal Laser ◽  
Radical Scavenger ◽  
Insulin Dependent

H2O2 mimicked the action of periportal pO2 in the modulation by O2 of the glucagon-dependent activation of the phosphoenolpyruvate carboxykinase (PCK) gene and the insulin-dependent activation of the glucokinase (GK) gene. H2O2 can be converted in the presence of Fe2+ in a Fenton reaction into hydroxyl anions and hydroxyl radicals (•OH). The hydroxyl radicals are highly reactive and might interfere locally with transcription factors. It was the aim of the present study to investigate the role of and to localize such a Fenton reaction. Hepatocytes cultured for 24 h were treated under conditions mimicking periportal or perivenous pO2 with glucagon or insulin plus the iron chelator desferrioxamine (DSF) or the hydroxyl radical scavenger dimethylthiourea (DMTU) to inhibit the Fenton reaction. PCK mRNA was induced by glucagon maximally under conditions of periportal pO2 and half-maximally under venous pO2. GK mRNA was induced by insulin with reciprocal modulation by O2. DSF and DMTU reduced the induction of PCK mRNA to about half-maximal and increased the induction of GK mRNA to maximal under both O2 tensions. Hydroxyl radical formation was maximal under arterial pO2. Perivenous pO2, DSF and DMTU each decreased the formation of •OH to about 70% of control. The Fenton reaction could be localized in a perinuclear space by confocal laser microscopy and three-dimensional reconstruction techniques. In the same compartment, iron could be detected by electron-probe X-ray microanalysis. Thus a local Fenton reaction is involved in the O2 signalling, which modulated the glucagon- and insulin-dependent PCK gene and GK gene activation.

scholarly journals Effects of supplementation with phosphorus, calcium and manganese during oil palm frond fermentation by Phanerochaete chrysosporium on ligninase enzyme activity

2020 ◽  
Vol 21 (5) ◽  
Author(s):  
Roni Pazla ◽  
Novirman Jamarun ◽  
Fauzia Agustin ◽  
Mardiati Zain ◽  
Arief Arief ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Phanerochaete Chrysosporium ◽  
Oil Palm ◽  
Manganese Peroxidase ◽  
Crude Protein ◽  
Lignin Degradation ◽  
Lignin Content ◽  
Oil Palm Frond ◽  
Range Test ◽  
Palm Frond

Abstract. Pazla R, Jamarun N, Agustin F, Zain M, Cahyani NO. 2020. Effects of supplementation with phosphorus, calcium and manganese during oil palm frond fermentation by Phanerochaete chrysosporium on ligninase enzyme activity. Biodiversitas 21: 1833-1838. The objective of this study was to evaluate the effects of supplementation with phosphorus (P) in combination with calcium (Ca) and manganese (Mn) during oil palm frond (OPF) fermentation by Phanerochaete chrysosporium on ligninase enzyme activity and lignin degradation. This study was carried out using a randomized complete design with 3 treatments (addition of P, Ca and Mn) and 5 replicates. The following treatments were performed: T1 (P 1000 + Ca 2000 + Mn 150 ppm), T2 (P 1500 + Ca 2000 + Mn 150 ppm), and T3  (P 2000 + Ca 2000 +Mn 150 ppm). The data were subjected to an analysis of variance (ANOVA), and differences between treatment means were tested using Duncan's multiple range test (DMRT). The parameters measured were as follows: lignin peroxidase (LiP) activity (U/mL), manganese peroxidase (MnP) activity (U/mL), crude protein (CP) content (%), crude fiber (CF) content (%) and the decrease in lignin (%). The results revealed a significant increase in LiP activity and CP content and a decrease in the lignin content (p<0.05) by the addition of P in the T3 treatment. However, the treatment nonsignificantly increased (p>0.05) MnP activity and significantly decreased (P<0.05) the CF content. In conclusion, supplementation of the OPF fermentation process with P 2000, Ca 2000, and Mn 150 ppm resulted in the highest ligninase enzyme activity and in decreased lignin content.

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