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According to the latest report from the intergovernmental panel on climate change (IPCC), currently, global warming due to methane (CH4) alone is about 0.5°C while due to carbon dioxide (CO2) alone is about 0.75°C. As CH4 emissions will continue growing, in order to limit warming to 1.5˚C, some of the most effective strategies are rapidly reducing CH4 emissions and developing large scale CH4 removal methods. The aim of this review article is to summarise and propose possible methods for atmospheric CH4 removal, based on the hydroxyl radical (°OH), which is the principal natural sink of many gases in the atmosphere and on many water surfaces. Inspired by mechanisms of °OH generation in the atmosphere and observed or predicted enhancement of °OH by climate change and human activities, we proposed several methods to enhance the °OH sink by some physical means using water vapour and artificial UV radiation.

Pig plasma contains a large amount of protein. Porcine plasma polypeptide can be prepared by the enzymatic hydrolysis of porcine plasma protein. The present study investigated the function, structure, and mechanisms of porcine plasma peptides.The results showed that WVRQAPGKGL had a major ability to scavenge hydroxyl radical scavenging activity (HRSA) (35.25%), 2,2'-azino-bis (3-ethylbenzothiazo line-6-sulfonic acid) diammonium salt radical scavenging activity (ABTS RSA) (93.09%) and 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity (DPPH RSA) (25.72%), as well as in angiotensin converting enzyme (ACE) inhibition (91.64%). WVRQAPGKGL could inactivate ACE by binding to Zn2+ because of the presence of carboxyl in WVRQAPGKGL. The ACE inhibition, HRSA, and DPPH of synthetic WVRQAPGKGL were improved by 12.70%, 16.06%, and 117.11% respectively after in vitro digestion. It (0.1 mg mLA new difunctional (antioxidant and hypotensive) peptide, WVRQAPGKGL, derived from porcine plasma hydrolyzate was isolated by gel filtration and reverse phase chromatography, and identified by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS)

Hydroxyl polycyclic aromatic hydrocarbons are considered active mutagenic and carcinogenic substances and are found in extremely low levels (ng/g) in biological samples. As a result, their determination in urine and blood samples is challenging, and a sensitive and effective method for the analysis of trace hydroxyl polycyclic aromatic hydrocarbons in complex biological matrices is required. In this work, a novel macroporous in-tube solid-phase microextraction monolith was prepared via a thiol-yne click reaction, and a highly efficient analytical method based on in-tube solid-phase microextraction coupled with UHPLC-MS/MS was developed to determine hydroxyl polycyclic aromatic hydrocarbons with low detection limits of 0.137-11.0 ng/L in complex biological samples. Four hydroxyl polycyclic aromatic hydrocarbons, namely, 2-hydroxyanthraquinone, 1-hydroxypyrene, 1,8-dihydroxyanthraquinone, and 6-hydroxychrysene, were determined in the urine samples of smokers, non-smokers, and whole blood samples of mice. Satisfactory recoveries were achieved in the range of 83.1-113% with relative standard deviations of 3.2-9.7%. It was found that implementation of the macroporous monolith gave a highly efficient approach for enriching trace hydroxyl polycyclic aromatic hydrocarbons in biological samples.

Lysosome-relevant cell death induced by lysosomal membrane permeabilization (LMP) has recently attracted increasing attention. However, nearly no studies show that currently available LMP inducers can evoke immunogenic cell death (ICD) or convert immunologically cold tumors to hot. Herein, we report a LMP inducer named TPE-Py-pYK(TPP)pY, which can respond to alkaline phosphatase (ALP), leading to formation of nanoassembies along with fluorescence and singlet oxygen turn-on. TPE-Py-pYK(TPP)pY tends to accumulate in ALP-overexpressed cancer cell lysosomes as well as induce LMP and rupture of lysosomal membranes to massively evoke ICD. Such LMP-induced ICD effectively converts immunologically cold tumors to hot as evidenced by abundant CD8+ and CD4+ T cells infiltration into the cold tumors. Exposure of ALP-catalyzed nanoassemblies in cancer cell lysosomes to light further intensifies the processes of LMP, ICD and cold-to-hot tumor conversion. This work thus builds a new bridge between lysosome-relevant cell death and cancer immunotherapy.

Off-target toxicity and insufficient hydroxyl radicals (. OH) generation limit the further clinical application of nanozymes in chemodynamic therapy (CDT). Herein, we designed and constructed a microRNA-triggered nanozyme cascade platform for enhanced tumor-specific chemodynamic therapy. The nanozyme-based cascade reaction could be triggered successfully by the high expression of microRNA in cancer cells to generate more . OH, thus exhibiting excellent tumor-specific therapeutic performance. Our work provides a new dimension for tumor-specific chemodynamic therapy.

In this study, a magnetic nanocatalyst (Fe3 O4 @SiO2 @CeO2 ) was prepared and applied in the catalytic ozonation of methyldopa (MD). The effects of operational parameters on catalytic ozonation performance were investigated, including ozone dosage, catalyst dosage, initial MD concentration, and pH. The removal of MD was 45.2% in ozonation, whereas the efficiency was achieved to 83.0% with the addition of Fe3 O4 @SiO2 @CeO2 . The results showed that Fe3 O4 @SiO2 @CeO2 could significantly improve the catalytic ozonation performance. And the enhanced mechanism study showed that it was attributed to promotion of ozone decomposition to generate hydroxyl radical. The reaction model was explored, and the reaction rates were calculated for the MD degradation in catalytic ozonation. A higher degradation efficiency of MD in catalytic ozonation was attributed to the enhanced surface effect of the catalysts, which was confirmed by using TBA, PO43- , and p-BQ as scavengers of hydroxyl radical, surface reaction, and superoxide radical. The hydroxyl radical and superoxide radical played an important role in the degradation of MD. The mechanism of catalytic ozonation by Fe3 O4 @SiO2 @CeO2 was discussed via X-ray photoelectron spectroscopy (XPS) spectra and experimental data.

Hydrogen binding of molecules on specific solid surface is an attractive interaction that can be employed as driving force for chemical bond activation, material directed assembly, protein protection, etc. However, the lack of quantitative characterization method for hydrogen bonds (HBs) on surface seriously limits its application. Herein, we measured the standard Gibbs free energy change (ΔG 0 ) of surface HBs using NMR technique. HBs accepting ability of surface was investigated in term of comparing ΔG 0 values by employing model biomass platform 5-hydroxymethylfurfural on a series of Co-N-C-n catalysts with electron-rich doped-nitrogen contents adjusted. Reducing the ΔG 0 effectively improves HBs accepting ability of the nitrogen-doped surface, and promotes the O-H bonds selectively initiated activation in the oxidation of 5-hydroxymethylfurfural. As a result, the reaction kinetics is accelerated and the rate constant is significantly increased. In addition to excellent catalytic performance, the turnover frequency (TOF) value for this oxidation is extremely higher than the reported non-noble metal catalysts.

Chemodynamic therapy (CDT) based on Fenton and Fenton-like reactions induces cancer cell killing via in situ catalyzing H

In this study, an enzyme-assisted extraction method was used to extract Orchis chusua D. Don (Salep) polysaccharide (SP), which was then modified by sulfation, acetylation, phosphorylation, and carboxymethylation to obtain modified polysaccharides. Furthermore, their degree of substitution, chemical composition, and molecular weight were evaluated. The primary structural features were characterized by UV spectra, FT-IR spectra, Congo-red test, and scanning electron microscope. The phosphorylated polysaccharide (SP-P) was demonstrated the highest scavenging ability on hydroxyl radical and growth-promoting activity on Lactobacillus Bulgaricus. The carboxymethylated polysaccharide (SP-C) was exhibited the strongest DPPH and ABTS radical scavenging effects. The acetylated polysaccharide (SP-A) displayed the best proliferation effects on Bifidobacterium adolescentis, whereas the sulfated polysaccharide (SP-S) maintained moderately stable antioxidant and probiotic ability. These findings indicate that the modified polysaccharides had their potential significance as new antioxidants and probiotics for the food industry. PRACTICAL APPLICATION: This article provides a new source for the development of polysaccharide derivatives as new antioxidants and probiotics for the food industry.

Despite the great efforts of using DNAzyme for gene therapy, its clinical success is limited by the lack of simple delivery systems and limited anticancer efficacy. Here, we develop a simple approach for the synthesis of hybrid nanostructures that exclusively consist of DNAzyme and Cu2+ with ultra-high loading capacity. The Cu-DNAzyme nanohybrids allow to effectively co-deliver DNAzyme and Cu2+ into cancer cells for combinational catalytic therapy. The released Cu2+ can be reduced to Cu+ by glutathione and then catalyze endogenous H2 O2 to form cytotoxic hydroxyl radicals for chemodynamic therapy (CDT), while the 10-23 DNAzyme enables the catalytic cleavage of VEGFR2 mRNA and activates gene silencing for gene therapy. We demonstrate that the system can efficiently accumulate in the tumor and exhibit amplified cascade antitumor effects with negligible systemic toxicity. Our work paves an extremely simple way to integrate DNAzyme with CDT for the dual-catalytic tumor treatment.

Chemodynamic therapy (CDT) is an effective tumor treatment strategy in which FeII reacts with hydrogen peroxide (H2 O2 ) in tumor cells to produce highly toxic hydroxyl radical (. OH) through the Fenton reaction. However, the content of endogenous H2 O2 in cells is limited, and the reaction between FeIII and H2 O2 is inefficient, greatly limiting the efficiency of the Fenton reaction and reducing the effectiveness of tumor treatment. Therefore, in this work, we designed and synthesized a new type of nano-system (CaO2 @TA-FeIII ) for the enhanced CDT of tumors, in which the polyphenolic compound- tannic acid (TA) and FeIII formed a TA-Fe nano-coating on the surface of calcium peroxide (CaO2 ) nanospherical aggregates. When the CaO2 @TA-FeIII nanoconjugates reach the tumor site, the CaO2 contained in the nanoconjugates produces H2 O2 after disintegration in tumor cells, and the carried TA rapidly reduces FeIII to FeII , solving the two major shortcomings in CDT of (1) insufficient content of H2 O2 in cancer cells, and (2) low catalytic efficiency of the Fenton reaction. Additionally, the . OH produced in the Fenton reaction induces oxidative stress for the tumor cells, promoting the occurrence of the "calcium overload" process, and thereby accelerating the death of tumor cells. Experimental results in vitro and in vivo showed that CaO2 @TA-FeIII nanoconjugates can effectively kill cancer cells and display an excellent tumor therapeutic effect. We believe that the CaO2 @TA-FeIII nanoconjugates are a promising new nano-platform for highly effective tumor treatment.

Increased use of titanium dioxide (TiO2 ) nanoparticles (NPs) in domestic and industrial applications has increased the risk for adverse environmental outcomes based on an elevated likelihood of organism exposure. Anatase TiO2 NP exposure to ultraviolet A (UV-A) radiation in aquatic environments generates radical oxygen species (ROS), which may ultimately be responsible for increased organism toxicity. We have identified and measured the 2 most relevant ROS species, hydroxyl and superoxide radicals, and described that ROS can be modeled using the highly reactive hydroxyl radical to provide an upper bound for toxicity. The TiO2 NPs were co-exposed to increasing natural organic matter (NOM) amounts (measured as concentration of dissolved organic carbon [DOC]) and simulated-sunlight UV-A intensities. Radical production rate was determined using fluorescence spectroscopy and was positively correlated with increases in TiO2 concentration and UV-A intensity, and negatively correlated with increased DOC concentration. Daphnia magna toxicity was also found to decrease with NOM addition, which is attributed to the decreased radical production rate with increased DOC concentrations. We demonstrate that the rate of ROS production from simulated-sunlight-irradiated TiO2 NPs can be quantified using relatively simple fluorescent techniques. We show that toxicity to TiO2 NP varies greatly with conditions, and that concentration alone is a poor predictor of toxicity. Describing toxicity/hydroxyl radical measurement may be a more accurate way to describe overall risk. We provide a framework for a simple model to describe toxicity/hydroxyl radical. These conclusions demonstrate the importance of considering exposure conditions as a means of risk management during TiO2 NP toxicity testing, waste management, and regulatory decisions. Environ Toxicol Chem 2021;40:1322-1334. © 2021 SETAC.

A new approach to hydrogen production from water is described. This simple method is based on carbon dioxide-mediated water decomposition under UV radiation. The water contained dissolved sodium hydroxide, and the solution was saturated with gaseous carbon dioxide. During saturation, the pH decreased from about 11.5 to 7-8. The formed bicarbonate and carbonate ions acted as scavengers for hydroxyl radicals, preventing the recombination of hydroxyl and hydrogen radicals and prioritizing hydrogen gas formation. In the presented method, not yet reported in the literature, hydrogen production is combined with carbon dioxide. For the best system with alkaline water (0.2 m NaOH) saturated with CO

Phosphorus monoxide (. PO) is a key intermediate in phosphorus chemistry, and its association with the hydroxyl radical (. OH) to yield metaphosphorous acid (cis-HOPO) contributes to the chemiluminescence in the combustion of phosphines. When photolyzing cis-HOPO in an Ar-matrix at 2.8 K, the simplest dioxophosphorane HPO2 and an elusive hydroxyl radical complex (HRC) of . PO form. This prototypical radical-radical complex reforms into cis-HOPO at above 12.0 K by overcoming a barrier of 0.28±0.02 kcal mol-1 . The vibrational spectra of this HRC and its D- and 18 O-isotopologues suggest a structure of . OH⋅⋅⋅OP. , for which a triplet spin multiplicity with a binding energy of -3.20 kcal mol-1 has been computed at the UCCSD(T)-F12a/aug-cc-pVTZ level.

Polyglycidylmethacrylate/polyindole (PGMA/PIN) conducting polymer composites having five different compositions were prepared chemically using FeCl3 as an oxidant agent in chloroform solution and nitrogen atmosphere at 10°C. The conducting polymer composites were characterized by FTIR spectroscopic technique, scanning electron microscopy (SEM), atomic force microscopy (AFM), and thermogravimetric analysis (TGA) measurements. It is seen that morphological structure of composite is different from PIN and PGMA. PGMA/PIN conducting polymer composite including 50% of PIN has a nonuniform and less homogenous structure compared to the PIN and PGMA polymer. in vitro antioxidant activity such as reduction force, superoxide radical removal activity, hydroxyl radical trapping activity, MDA measurements in Saccharomyces cerevisiae cells of PGMA/PIN conducting polymer composite was investigated. It was observed that the reduction force capacities decreased as PIN content and increased due to the percentage of composite of PGMA content. in vitro studies of synthesized composites have shown us that these compounds possess new antioxidant properties.

Unpredictable in vivo therapeutic feedback of hydroxyl radical (•OH) efficiency is the major bottleneck of chemodynamic therapy. Herein, we describe novel Fenton-based nanotheranostics NQ-Cy@Fe&GOD for spatio-temporally reporting intratumor •OH-mediated treatment, which innovatively unites dual-channel near-infrared (NIR) fluorescence and magnetic resonance imaging (MRI) signals. Specifically, MRI signal traces the dose distribution of Fenton-based iron oxide nanoparticles (IONPs) with high-spatial resolution, meanwhile timely fluorescence signal quantifies •OH-mediated therapeutic response with high spatio-temporal resolution. NQ-Cy@Fe&GOD can successfully monitor the intracellular release of IONPs and •OH-induced NQO1 enzyme in living cells and tumor-bearing mice, which makes a breakthrough in conquering the inherent unpredictable obstacles on spatio-temporally reporting chemodynamic therapy, so as to manipulate dose-dependent therapeutic process. This unprecedented strategy can elaborately bridge MRI and fluorescence imaging modality with spatio-temporal resolution, and paves a new pathway for accurately evaluating in situ generation of •OH feedback on the intratumoral catalytic Fenton reaction.

Tirapazamine (TPZ) has been tested in clinical trials on radio‐chemotherapy due to its potential highly selective toxicity towards hypoxic tumor cells. It was suggested that either the hydroxyl radical or benzotriazinyl radical may form as bioactive radical after the initial reduction of TPZ in solution. In the present work, we studied low‐energy electron attachment to TPZ in the gas phase and investigated the decomposition of the formed TPZ− anion by mass spectrometry. We observed the formation of the (TPZ–OH)− anion accompanied by the dissociation of the hydroxyl radical as by far the most abundant reaction pathway upon attachment of a low‐energy electron. Quantum chemical calculations suggest that NH2 pyramidalization is the key reaction coordinate for the reaction dynamics upon electron attachment. We propose an OH roaming mechanism for other reaction channels observed, in competition with the OH dissociation., Low‐energy electrons make a choice: Upon the attachment of a low‐energy electron to the potential radiosensitizer compound tirapazamine in the gas phase, dissociation of the OH radical is by far the most abundant reaction obtained. Other dissociation channels as well as the metastable parent anion formed upon roaming of OH are computationally predicted.

Guanine radicals are important reactive intermediates in DNA damage. Hydroxyl radical (HO. ) has long been believed to react with 2'-deoxyguanosine (dG) generating 2'-deoxyguanosin-N1-yl radical (dG(N1-H). ) via addition to the nucleobase π-system and subsequent dehydration. This basic tenet was challenged by an alternative mechanism, in which the major reaction of HO. with dG was proposed to involve hydrogen atom abstraction from the N2-amine. The 2'-deoxyguanosin-N2-yl radical (dG(N2-H). ) formed was proposed to rapidly tautomerize to dG(N1-H). . We report the first independent generation of dG(N2-H). in high yield via photolysis of 1. dG(N2-H). is directly observed upon nanosecond laser flash photolysis (LFP) of 1. The absorption spectrum of dG(N2-H). is corroborated by DFT studies, and anti- and syn-dG(N2-H). are resolved for the first time. The LFP experiments showed no evidence for tautomerization of dG(N2-H). to dG(N1-H). within hundreds of microseconds. This observation suggests that the generation of dG(N1-H). via dG(N2-H). following hydrogen atom abstraction from dG is unlikely to be a major pathway when HO. reacts with dG.

Co single-atom catalysts (SACs) with good aqueous solubility and abundant labelling functional groups were prepared in Co/Fe bimetallic metal-organic frameworks by a facile solvothermal method without high-temperature calcination. In contrast to traditional chemiluminescence (CL) catalysts, Co SACs accelerated decomposition of H2 O2 to produce a large amount of singlet oxygen (1 O2 ) rather than superoxide (O2 .- ) and hydroxyl radical (OH. ). They were found to dramatically enhance the CL emission of the luminol-H2 O2 reaction by 1349 times, and, therefore, were employed as very sensitive signal probes for conducting CL immunoassay of cardiac troponin I. The detection limit of the target analyte was as low as 3.3 pg mL-1 . It is the first time that employment of SACs for boosting CL reactions has been validated. The Co SACs can also be employed to trace other biorecognition events with high sensitivity.

Chaos and the natural evolution of tumor systems can lead to the failure of tumor therapies. Herein, we demonstrate that iridium oxide nanoparticles (IrOx ) possess acid-activated oxidase and peroxidase-like functions and wide pH-dependent catalase-like properties. The integration of glucose oxidase (GOD) unlocked the oxidase and peroxidase activities of IrOx by the production of gluconic acid from glucose by GOD catalysis in cancer cells, and the produced H2 O2 was converted into O2 to compensate its consumption in GOD catalysis owing to the catalase-like function of the nanozyme, thus resulting in the continual consumption of glucose and the self-supply of substrates to generate superoxide anion and hydroxyl radical. Moreover, IrOx can constantly consume glutathione (GSH) by self-cyclic valence alternation of IrIV and IrIII . These cascade reactions lead to a "butterfly effect" of initial starvation therapy and the subsequent pressure of multiple reactive oxygen species (ROS) to completely break the self-adaption of cancer cells.

In this study, nano-CaO2 (nCaO2 ) was successfully synthesized and constituted the nCaO2 /Fe(II) system applying to remediate BTEX, which are typical mixed pollutants in contaminated groundwater. The particle size of the synthesized nCaO2 was 108.91 nm, and it displayed better BTEX remediation performance than that of commercial CaO2 . The innovative generation pattern of hydroxyl radicals ( HO · ) in the nCaO2 /Fe(II) system has been investigated using benzoic acid as the HO · probe, and the proper molar ratio of nCaO2 /Fe(II) was optimized as 1/1. Over 90% of BTEX was removed in 180 min with the nCaO2 /Fe(II)/BTEX molar ratio of 40/40/1. Further experiments evaluated the influence of co-existence of mixed pollutants chlorinated hydrocarbon compounds (CHCs) or surfactant constituents on BTEX remediation performance. The experimental results suggested that CHCs have limited influence on BTEX removal rate and surfactants have negative effects on BTEX remediation performance in the experimental conditions. In conclusion, the findings in this study could give some inspirations to apply the nCaO2 /Fe(II) process in remediating co-existing pollutants in contaminated groundwater. PRACTITIONER POINTS: nCaO2 /Fe(II) system applied to remediate mixed contaminants. HO · generation pattern of the nCaO2 /Fe(II) system has been investigated. The influence of chloride hydrocarbon compounds have been studied. The effects of surfactants were evaluated.

Highland barley brewer's spent grain (BSG), being China's brewing industry's major by-product is the focus of current research. The aim of the present study was to scrutinize the effects of ultrasound and heat pretreatments on enzymatic hydrolysis of highland barley BSG protein hydrolysates (HBSGPH) and evaluate the effect of enzymatic hydrolysis time on the antioxidant activity of hydrolysates by Alcalase. Different ultrasonic waves (40 and 50 kHz) and heat pretreatment temperatures (50 and 100 °C) were chosen and the pretreatment time was 15, 30, and 60 min. The obtained results revealed that the ultrasound pretreatment of highland barley BSG protein at 40 and 50 kHz has significantly (P < 0.05) enhanced about 57 and 67% of oxygen radical absorption capacity of obtained hydrolysate over the untreated substrate. The 1,1-diphenyl-2-picrylhdrazl (DPPH) radical scavenging activity (DRSA) 28%, metal chelating activity (MCA) 54%, superoxide radical scavenging activity (SRSA) 18%, and hydroxyl radical scavenging activity (HRSA) 25% of HBSGPH at 50 kHz were also improved (P < 0.05) significantly. HBSGPH from heat treatment at 100 °C showed no SRSA and HRSA scavenging activities but improved significantly (P < 0.05) about 27% ferric reducing antioxidant power (FRAP) assay values. In the present work, the resultant HBSGPH had stronger antioxidant properties with ultrasound pretreatment at 50 kHz and the enzymatic hydrolysis after 4 hr was facilitating the enzymatic release of antioxidant peptides from HBSGPH. PRACTICAL APPLICATION: Highland barley BSG is attracting toward natural food products due to its potent natural antioxidants to overcome the risk of diseases and are beneficial for human health.

Chemodynamic therapy (CDT) is an emerging treatment that usually employs chemical agents to decompose hydrogen peroxide (H2O2) into hydroxyl radical (•OH) via Fenton or Fenton‐like reactions, inducing cell apoptosis or necrosis by damaging biomacromolecules such as, lipids, proteins, and DNA. Generally, CDT shows high tumor‐specificity and minimal‐invasiveness in patients, thus it has attracted extensive research interests. However, the catalytic reaction efficiency of CDT is largely limited by the relatively high pH at the tumor sites. Herein, a 808 nm laser‐potentiated peroxidase catalytic/mild‐photothermal therapy of molybdenum diphosphide nanorods (MoP2 NRs) is developed to improve CDT performance, and simultaneously achieve effective tumor eradication and anti‐infection. In this system, MoP2 NRs exhibit a favorable cytocompatibility due to their inherent excellent elemental biocompatibility. Upon irradiation with an 808 nm laser, MoP2 NRs act as photosensitizers to efficiently capture the photo‐excited band electrons and valance band holes, exhibiting enhanced peroxidase‐like catalytic activity to sustainedly decompose tumor endogenous H2O2 to •OH, which subsequently destroy the cellular biomacromolecules both in tumor cells and bacteria. As demonstrated both in vitro and in vivo, this system exhibits a superior therapeutic efficiency with inappreciable toxicity. Hence, the work may provide a promising therapeutic technique for further clinical applications., A promising therapeutic strategy of laser‐potentiated peroxidase catalytic/mild‐photothermal therapy of molybdenum diphosphide nanorods (MoP2 NRs) is proposed to improve CDT performance and achieve effective tumor eradication and anti‐infection. In this system, MoP2 NRs exhibit favorable cytocompatibility and peroxidase‐like catalytic activity to decompose tumor endogenous H2O2 into •OH radicals, which subsequently break biomolecules, simultaneously inducing tumor cells apoptosis and bacteria inactivation.

Landfill leachate can threaten the environment and human life. Therefore, this study aims to investigate the efficiency of ozone (O3 ), O3 with zirconium tetrachloride (O3 /ZrCl4 ) and O3 with tin tetrachloride (O3 /SnCl4 ) in remediating the stabilised anaerobic landfill leachate (SAL) from Alor Pongsu, Perak. Hydroxyl radical (OH•) is an important oxidising agent in the ozonation process. Its presence was tested using tert-Butyl alcohol. Results showed that using ZrCl4 and SnCl4 in ozonation boosted the generation of hydroxyl radical, thereby enhancing the oxidation process and pollutant removal inside the sample. The O3 /ZrCl4 mix at chemical oxygen demand (COD) to ZrCl4 ratio of 1:1.5, pH 8-9 and 90 min reaction time resulted in the highest reduction rates of COD and colour at 91.9% and 99.6%, respectively. All results demonstrated that the optimum performance occurred at alkaline conditions (pH > 8), proving that OH radicals primarily oxidised the pollutants through an indirect reaction pathway. The biodegradability (biochemical oxygen demand/COD) ratio was also considerably improved from 0.02 (raw) to 0.37 using O3 /ZrCl4 , compared with using O3 alone and using O3 /SnCl4, which only recorded 0.23 and 0.28, respectively, after the treatment. The study demonstrated that O3 /ZrCl4 was the most efficient combination.

As a type of reactive oxygen species (ROS), hydroxyl radical (·OH) is closely associated with many kinds of diseases. The present study aimed to develo p a novel OH fluorescent probe based on coumarin, a new compound that has not been previously reported. This probe exhibited good linear range and selectivity for ·OHl, and is able to avoid interference from some metal ions and other kinds of ROS (H2 O2 , O2 .- , 1 O2 , and HClO). Meanwhile, this probe has been used to evaluate the ·OH-scavenging efficiency of different compounds, such as isopropyl alcohol, cytosine, uracil, Tempo, Glutathione (GSH), and dimethyl sulfoxide (DMSO). Therefore, the present study shows that this probe not only can effectively measure the level of ·OH, but also can assess the ·OH-scavenging efficiency of different compounds. Furthermore this current study suggested that following further optimization, this probe may be potentially applied in the diagnosis of oxidative stress in human body.

BACKGROUND: Photocatalysis is one of the effective ways to solve the problem of water and gas pollution. An excellent photocatalyst should have the following advantages: efficient photocatalytic activity for gas and water pollutants, recyclable and stable characteristics, non‐toxic and low‐cost. Constructing heterojunctions and introducing oxygen vacancies (OVs) are two effective measures to achieve these targets. RESULTS: It is found that the 1.0% Pd/PdO/β‐Bi₂O₃ exhibits the best photocatalytic activity with an efficiency of 97.4% for Bisphenol A (BPA) degradation and 47.6% for nitric oxide (NO) removal within 30 min. The 1.0% Pd/PdO/β‐Bi₂O₃ composite shows 23.3% efficiency in the photodegradation of BPA under 595 nm monochromatic light irradiation, while β‐Bi₂O₃ tends to be invalid. Moreover, the OVs promote the removal of NO without irradiation. CONCLUSION: In this work, a novel ternary Pd/PdO/β‐Bi₂O₃ material as high‐performance photocatalyst for the BPA degradation and NO removal was synthesized. The presence of OVs promotes the activation of the oxygen molecule, thereby facilitating the photocatalytic process. The p‐n junction of PdO/β‐Bi₂O₃ and the Schottky barrier of Pd/β‐Bi₂O₃ significantly limit the recombination of photoinduced electron–hole pairs in the composite. Furthermore, an artifact in the electron spin resonance (ESR) spectrum obtained by spin trapping with 5,5‐dimethyl‐1‐pyrroline N‐oxide (DMPO) as adducts confirms that both hydroxyl radical (•OH) and superoxide radical (•O₂⁻) species are involved in the photocatalytic process. The present work offers a new perspective for developing the composite photocatalysts with high efficiency through loading of metal nanoparticles and creating an heterojunction. © 2019 Society of Chemical Industry

In order to promote the comprehensive utilization of the Auricularia auricula waste residue, the extraction process and the physicochemical properties of melanin from A. auricula waste residue were studied. Furthermore, the chemical antioxidant activity of waste residue melanin and its protective effect on cell oxidative injury induced by H2O2 were investigated. The results indicated that the ultrasonic‐assisted extraction process could be used to extract the melanin from A. auricula waste residue. Melanin had a good solubility in alkali solution and exhibited a certain stability to thermal. There was no significant difference between A. auricula melanin control group and waste residue melanin on ABTS, DPPH, and hydroxyl radical scavenging activity. Waste residue melanin significantly inhibited the cell death caused by H2O2, and the cell viability was restored to 98.09 ± 5.97% when the melanin concentration was 1.6 mg/ml. Cell morphology observation confirmed that the melanin ameliorated the morphological changes of cells induced by oxidative stress.

A photocatalyst with a high separation efficiency of carriers is crucial for the photocatalytic efficient decomposition of volatile organic compounds (VOCs). In this work, a new iodine-deficient BiO1.2 I0.6 /Bi2 O3 photocatalyst was developed through a solvothermal approach coupled with thermal decomposition. The 2 wt % BiO1.2 I0.6 /Bi2 O3 sample demonstrated optimal photocatalytic activity for the degradation of toluene, achieving a 55.1 % mineralization ratio under 8 h of irradiation, which was 14.9 and 2.1 times higher than those of BiO1.2 I0.6 and Bi2 O3 , respectively. Compared with BiO1.2 I0.6 and Bi2 O3 , 2 wt % BiO1.2 I0.6 /Bi2 O3 exhibited the weakest fluorescence band, highest photocurrent density, and lowest impedance; thus suggesting that Bi2 O3 compounded by 2 wt % BiO1.2 I0.6 distinctly promoted the separation efficiency of carriers. The hydroxyl radical (. OH) was the main active species, apart from holes, for the photocatalytic degradation of toluene.

The use of gold nanoparticles as radiosensitizers is an effective way to boost the killing efficacy of radiotherapy while drastically limiting the received dose and reducing the possible damage to normal tissues. Herein, we designed aggregation-induced emission gold clustoluminogens (AIE-Au) to achieve efficient low-dose X-ray-induced photodynamic therapy (X-PDT) with negligible side effects. The aggregates of glutathione-protected gold clusters (GCs) assembled through a cationic polymer enhanced the X-ray-excited luminescence by 5.2-fold. Under low-dose X-ray irradiation, AIE-Au strongly absorbed X-rays and efficiently generated hydroxyl radicals, which enhanced the radiotherapy effect. Additionally, X-ray-induced luminescence excited the conjugated photosensitizers, resulting in a PDT effect. The in vitro and in vivo experiments demonstrated that AIE-Au effectively triggered the generation of reactive oxygen species with an order-of-magnitude reduction in the X-ray dose, enabling highly effective cancer treatment.

Cimicifuga dahurica (Turcz.) Maxim. exerts significant antioxidative due to its high phenolic constituent content. In this study, the extraction condition of the phenolic constituents and antioxidant effect was optimized by the Box-Behnken design and response surface methodology. Eleven main bioactive analytes of Cimicifuga dahurica (Turcz.) Maxim. were simultaneously quantified by high-performance capillary electrophoresis with diode-array detector to assess the effect of extraction technology. The optimal extraction parameters were determined as: the concentration of ethanol 56.21%, liquid/solid ratio 14.65:1, and extraction time 1.64 h for 2.67 times. According to the results, a maximal value of total phenolic acids (3.67 mg/g) was obtained. Meanwhile, the influence of different extraction technology on antioxidant activities were evaluated by 1,1-diphenyl-2-picrylhydrazyl, 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonate), ferric reducing antioxidant power and hydroxyl radical scavenging method. The results presented here showed that the content of phenolic acid and antioxidant effect was much higher than the European Pharmacopoeia. Altogether, this method successfully applied response surface methodology to optimize the Cimicifuga dahurica (Turcz.) Maxim. extract with high antioxidant activities.

The reaction profiles for the uni- and bimolecular decomposition of benzyl hydroperoxide have been studied in the context of initiation reactions for the (aut)oxidation of hydrocarbons. The unimolecular dissociation of benzyl hydroperoxide was found to proceed through the formation of a hydrogen-bonded radical-pair minimum located +181 kJ mol-1 above the hydroperoxide substrate and around 15 kJ mol-1 below the separated radical products. The reaction of toluene with benzyl hydroperoxide proceeds such that O-O bond homolysis is coupled with a C-H bond abstraction event in a single kinetic step. The enthalpic barrier of this molecule-induced radical formation (MIRF) process is significantly lower than that of the unimolecular O-O bond cleavage. The same type of reaction is also possible in the self-reaction between two benzyl hydroperoxide molecules forming benzyloxyl and hydroxyl radical pairs along with benzaldehyde and water as co-products. In the product complexes formed in these MIRF reactions, both radicals connect to a centrally placed water molecule through hydrogen-bonding interactions.

BACKGROUND: Anodic oxidation, a promising approach for the removal of refractory organic pollutants in wastewater through advanced oxidation, still faces the challenge of high energy consumption. This study coupled an O₂‐reducing biocathode, a cathode thermodynamically more favorable than conventional abiotic ones, with an MnOₓ/Ti electrocatalytic porous anode, to produce a novel biocathode–electrocatalytic reactor (BECR). RESULTS: After inoculation, the BECR was successfully started up to generate current at a voltage of 0.7 V, which was lower than the startup voltages of electrocatalytic reactors with abiotic cathodes. The cathode potential of the BECR was increased by approximately 300 mV. Abundant electrochemically active microorganisms were found on the BECR cathode with Pseudomonas and Acinetobacter as the dominant genera reducing O₂ to H₂O. Furthermore, hydroxyl radical (·OH) generation was detected in the anode chamber of the BECR after startup at 0.7 V and contributed to its current production. This phenomenon was not observed for electrocatalytic reactors. The mechanism of the BECR in reducing the applied voltage to generate ·OH was well elucidated using the thermodynamic theory of Gibbs free energy. CONCLUSIONS: The coupling of the O₂‐reducing biocathode improved the thermodynamics of the BECR cathode toward a high redox potential and consequently reduced its applied voltage to generate ·OH, thereby rendering it as potentially energy saving and suitable for use in wastewater treatment. © 2019 Society of Chemical Industry

BACKGROUND: Methylated derivatives of catechins have received great attention for health beneficial effects, especially antiallergic activity. However, the scarce natural abundance of methylated catechins limits further bioactive studies. The objective of this work was to investigate regiospecific methylation of the hydroxyls of (+)‐catechin through a stepwise differentiation strategy based on electronic difference between the hydroxyl groups. RESULTS: Selective methylation of the hydroxyls on different rings was realized by employing Meerwein salt as the methylation reagent. Preferential acylation of the phenolic hydroxyls on A and B rings allowed selective exposure of the aliphatic hydroxyl on C ring to methylation. The vicinal phenolic hydroxyls on B ring were preferentially methylated under mild basic condition due to the acidic properties. Methylation of the phenolic hydroxyls on A ring was achieved by sequential protection and deprotection operations. Finally, antioxidant activities of all the individual methylated (+)‐catechins were explored by 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid) assay. CONCLUSION: Regiospecific methylation of the phenolic and aliphatic hydroxyls was systematically achieved under mild conditions. Preparation of all the individual methylated (+)‐catechins was accomplished with a greener methylation reagent: nonvolatile Meerwein salt. This work laid a solid foundation for preparation of diverse O‐methylated catechins for bioactivity studies. © 2019 Society of Chemical Industry

Protein oxidation is considered as an important issue in food preservation process. In the present study, the potential influence of protein oxidation on water holding capacity and protein structure of jumbo squid (Dosidicus gigas) mantle was investigated. After the hydroxyl radical oxidation, it was found that the carbonyl, surface hydrophobicity and dityrosine content of myofibrillar protein significantly increased (P