Radical Oxidation Research Articles

Oxidative Deformylation of the Predominant DNA Lesion 5-Formyl-2'-deoxyuridine.

Radical oxidation of DNA gives rise to potentially deleterious lesions such as strand breaks and various nucleobase modifications including 5-formyl-2'-deoxyuridine (5-fo-dU), a prevalent product derived from the oxidation of the C5-methyl group of thymidine. The present study investigates the unusual transformation of 5-fo-dU into 5-hydroxy-2'-deoxyuridine (5-oh-dU) and 5,6-dihydroxy-5,6-dihydro-2'-deoxuridine (gly-dU), two products typically associated with the oxidation of 2'-deoxycytidine. Detailed mechanistic analyses reveal that hydrogen peroxide, either generated as a byproduct of ascorbate autoxidation or added exogenously, mediates the formation of these oxidatively induced C5-dealkylated products. We show that the major product 5-oh-dU results from a Baeyer-Villiger rearrangement of the formyl functionality of 5-fo-dU while the minor product gly-dU derives from α,β-oxidation of the enal portion followed by deformylation. These reactions were observed in both 2'-deoxynucleoside monomers as well as isolated DNA. Our findings further clarify the oxidation chemistry of thymidine and highlight a novel oxidative decomposition pathway that can help understand the fate of certain types of DNA damage. Furthermore, our results underscore the pro-oxidant properties of ascorbate in vitro that can lead to the adventitious oxidation of substrates via the reduction of trace metals ions and generation of hydrogen peroxide.

Salt template-assisted polymer tethering strategy to achieve high dispersed cobalt single atoms/clusters on porous carbon catalysts for effective Fenton-like reactions

The exploration of the synthesis of porous carbon-supported metal nanocatalysts with high metal loading and dispersion for the development of heterogenous catalysts is important. However, this remains a challenging subject. In this paper, a salt template-assisted polymer tethering strategy was proposed to prepare Co single atom and ultrafine cluster anchored on porous carbon (Co-NPC) with a high-loading of 16.9wt%, thereby exposing high density of reaction sites. The obtained Co-NPC catalyst exhibited excellent catalytic performance for almost 100% degradation of bisphenol A (BPA) within 20min, which is much faster than the CoSA-NPC catalyst with only single atom sites and Co-NC without salt template added. Radical quenching experiments and electron paramagnetic resonance tests verified that both the nonradical oxidation pathway by 1O2, the electron transfer and radical oxidation pathway by •OH, SO4•- appeared during the degradation process. After 3 cycles, the removal rate of BPA did not decrease significantly. The fixed bed experiment revealed that Co-NPC could realize the continuous degradation of methylene blue (MB) with almost 100% degradation efficiency. This research indicated that the strategy by pyrolyzing metal coordinated polymer is a potential method for the synthesis of high metal loading catalyst at gram scale, meeting the requirement of practical applications.

Rotaxane-catalyzed aerobic oxidation of primary alcohols

Nitroxide radicals are widely utilized as catalysts for the oxidation of primary alcohols. Here, the aerobic catalytic oxidation cycle of nitroxide radicals has been implemented within a mechanically interlocked rotaxane architecture consisting of a paramagnetic crown ether, which is confined by a molecular axle containing a dialkylammonium station and a 1,2,3-triazole unit. The rotaxane is engineered to exploit the oxidation of a primary alcohol: the primary catalyst is the wheel, a nitroxide radical capable of altering its oxidation state during the catalytic cycle, while the co-oxidant is the Cerium(IV)/O2 couple. The synthesis of the proposed rotaxane, along with its characterization using EPR, HRMS, voltammetry and NMR data, is reported in the paper. The aerobic catalytic oxidation cycle was further investigated using EPR, NMR and GC-MS analyses. This study can aid in the design of autonomously driven molecular machines that exploit the aerobic catalytic oxidation of nitroxide radicals.

Study on the enhancement of oxidation activity of heated coal in closed fire area and mechanism of reignition by opening seal

Residual heat following the closure of a coal mine fire area induces alterations in the physical and chemical structure of coal, which not only interfere with the opening time but also engenders potential catastrophic incidents upon the reopening of the fire area. Therefore, the structural changes in coal before and after pyrolysis were first analyzed by SEM, BET, XPS, 13C NMR and ESR. Second, the crossing-point temperature and constant-temperature differential heat methods were employed to investigate the process and characteristics of alkyl radical oxidation heat production. Quantum chemistry was integrated to analyze the mechanism of coal oxidation activity enhancement when the fire area was unsealed. The experimental results revealed that the residual heat could induce physicochemical structural changes in coal at varying distances. Upon exposure to oxygen, cracks facilitate oxygen migration and water evaporation mitigates heat consumption. The low-energy barrier of the alkyl radical oxidation reactions intensifies the oxidation activity of pyrolyzed coal, which can react with oxygen at room temperature to release heat. Under heat storage conditions, the active groups in coal are stimulated to further react. As a corollary, the substantial release of heat occurs, heightening the risk of coal re-ignition upon reopening of the fire area. The research results are helpful in performing accurate targeted treatment for different temperature gradients in underground fire areas to prevent the reignition of heated coal in closed fire areas.

Біометричний аналіз показників прооксидантно-антиоксидантного стану плазми крові щурів за дії гістаміну і кверцетину

The regularities of the effect of histamine in concentrations of 0.01; 0.1; 1; 10 μM were studied and quercetin in concentrations of 0.1; 0.3; 0.5; 1; 3; 5 mM, as well as their combined effect on the prooxidant-antioxidant state of blood plasma of rats, using cluster and factor biometric analyses. It was established that the experimental groups according to the investigated indicators (TBА-positive products, lipid hydroperoxides, carbonyl groups of neutral and basic proteins, superoxide anion radical, superoxide dismutase, catalase, reduced glutathione, ATP) were distributed among 13 clusters (according to cluster analysis). In one group of similarities, the effect of histamine in concentrations of 0.01 µM and 1 µM was revealed. Quercetin at a concentration of 0.5 mM and histamine at a concentration of 0.1 µM have a similar effect on the indicators of the prоoxidant-antioxidant state of the blood plasma. Combined addition to the blood of histamine at a concentration of 10 μM and quercetin at a concentration of 0.1; 0.5; 3 mM lead to the same changes in the indicated studied indicators. Cluster analysis also combined the combined effects of 0.01 μM histamine and 0.1 and 3 mM quercetin. It is important to note that a decrease in the content of carbonyl groups of proteins was found in those classers whose experimental blood groups were added to histamine and quercetin, which indicates a decrease in protein damage due to free radical oxidation processes. Using factor analysis, it was established the presence of three hidden factors that affect the processes of free radical oxidation of blood under the action of histamine and quercetin. A high correlation of factor I with protein carbonyl groups, reduced glutathione, superoxide anion radical was revealed. Factor II is most correlated with ATP, superoxide dismutase, lipid hydroperoxides. There is a close relationship between factor III and TBА-positive products and catalase. Taking into account the closeness of the relationship, factor I was given the name “factor of action on proteins”, factor II – “factor of action on bioenergetics and initiator of lipid peroxidation processes”, factor III – “factor of enhancement of lipid peroxidation processes”. It was established that quercetin activates factor I (influence on proteins, causing their oxidation) and factor III (intensification of lipid peroxidation processes) depending on the concentration of the drug. Quercetin in a concentration of 1 mM has the property of both factors (I and III).

When Metal Complexes Evolve, and a Minor Species is the Most Active: the Case of Bis(Phenanthroline)Copper in the Catalysis of Glutathione Oxidation and Hydroxyl Radical Generation

AbstractSeveral copper‐ligands, including 1,10‐phenanthroline (Phen), have been investigated for anticancer purposes based on their capacity to bind excess copper (Cu) in cancer tissues and form redox active complexes able to catalyse the formation of reactive oxygen species (ROS), ultimately leading to oxidative stress and cell death. Glutathione (GSH) is a critical compound as it is highly concentrated intracellularly and can reduce and dissociate copper(II) from the ligand forming poorly redox‐active copper(I)‐thiolate clusters. Here we report that Cu‐Phen2 speciation evolves in physiologically relevant GSH concentrations. Experimental and computational experiments suggest that at pH 7.4 mostly copper(I)‐GSH clusters are formed, but a minor species of copper(I) bound to one Phen and forming ternary complexes with GSH (GS−Cu‐Phen) is the redox active species, oxidizing quite efficiently GSH to GSSG and forming HO⋅ radicals. This minor active species becomes more populated at lower pH, such as typical lysosomal pH 5, resulting in faster GSH oxidation and HO⋅ production. Consistently, cell culture studies showed lower toxicity of Cu‐Phen2 upon inhibition of lysosomal acidification. Overall, this study underscores that sub‐cellular localisation can considerably influence the speciation of Cu‐based drugs and that minor species can be the most redox‐ and biologically‐active.

When Metal Complexes Evolve, and a Minor Species is the Most Active: the Case of Bis(Phenanthroline)Copper in the Catalysis of Glutathione Oxidation and Hydroxyl Radical Generation.

Several copper-ligands, including 1,10-phenanthroline (Phen), have been investigated for anticancer purposes based on their capacity to bind excess copper (Cu) in cancer tissues and form redox active complexes able to catalyse the formation of reactive oxygen species (ROS), ultimately leading to oxidative stress and cell death. Glutathione (GSH) is a critical compound as it is highly concentrated intracellularly and can reduce and dissociate copper(II) from the ligand forming poorly redox-active copper(I)-thiolate clusters. Here we report that Cu-Phen2 speciation evolves in physiologically relevant GSH concentrations. Experimental and computational experiments suggest that at pH7.4 mostly copper(I)-GSH clusters are formed, but a minor species of copper(I) bound to one Phen and forming ternary complexes with GSH (GS-Cu-Phen) is the redox active species, oxidizing quite efficiently GSH to GSSG and forming HO⋅ radicals. This minor active species becomes more populated at lower pH, such as typical lysosomal pH5, resulting in faster GSH oxidation and HO⋅ production. Consistently, cell culture studies showed lower toxicity of Cu-Phen2 upon inhibition of lysosomal acidification. Overall, this study underscores that sub-cellular localisation can considerably influence the speciation of Cu-based drugs and that minor species can be the most redox- and biologically-active.

INDICATORS OF FREE RADICAL OXIDATION AND ANTIOXIDANT PROTECTION IN THE ORAL FLUID OF CHILDREN WITH CHRONIC CATARRHAL GINGIVITIS AND DIABETIS MELLITUS

Failure of antioxidant mechanisms leads to an increase in lipid peroxidation products in the body, resulting in a non-specific cascade of cellular membrane damage. Proteins play a crucial role in metabolic processes, but when lipid peroxidation intensifies, protein modifications occur, leading to fragmentation, denaturation, and loss of biological activity. This disruption impairs tissue regenerative processes. The objective of this study was to analyze indicators of free radical oxidation and antioxidant protection in the oral fluid of children with chronic catarrhal gingivitis and type I diabetes mellitus. Materials and methods. A total of 170 children aged 12 to 16 were observed, including 130 who were examined and treated at the Endocrinology Department of the Regional Municipal Non-Profit Institution “Chernivtsi Regional Pediatric Clinical Hospital” for type 1 diabetes mellitus. Among them, 74 children had a disease duration of less than 5 years, including 65 with chronic catarrhal gingivitis. Sixty five children had diabetes for more than 5 years, with 44 of them diagnosed to have chronic catarrhal gingivitis. The children with chronic catarrhal gingivitis were further divided into groups based on their level of glycemic control: 1 child with optimal glycemic control, 66 with suboptimal glycemic control, and 42 with glycemic control at a high risk to life. The control group included 40 practically healthy children: 22 of them had clinically healthy periodontal tissues, and 18 children were diagnosed to suffer from chronic catarrhal gingivitis. Results. The study performed found out that children with chronic catarrhal gingivitis present increased indicators of lipid peroxide oxidation (protein oxidative modification, diene conjugates, malondialdehyde) and decreased activity of the enzyme in the antioxidant protective system of the oral fluid (whole protein, НS-groups, ceruloplasmin, activity of supermutase and catalase) in comparison with indicators of children without dental pathology. The most considerable changes were found in patients with chronic catarrhal gingivitis and type 1 diabetes mellitus, especially when the disease lasted more than 5 years (р<0,05).

Evaluation of antioxidant activity of 1,2,4-triazole derivatives in the initiation of free radical processes

The activation of lipid free radical oxidation is a key stage in the development of many diseases and can lead to the emergence of related complications. To identify new synthetic compounds with antioxidant properties, it is necessary to conduct studies on various models of experimental free radical oxidation of biomolecules. Literature sources indicate that among the derivatives of 1,2,4-triazole, there is a significant number that possess high antioxidant activity. The aim of the study to assess the antioxidant properties of newly synthesized S-derivatives of 1,2,4-triazole through the inhibition of reactive oxygen species accumulation in the superoxide dismutase system. Materials and methods. To achieve this goal, we used one of the methods for assessing antioxidant activity by initiating free radical processes in vitro, specifically by inhibiting the accumulation of reactive oxygen species. Results. Twenty-three S-derivatives of 5-(thiophene-3-ylmethyl)-4-R-1,2,4-triazole-3-thiols were investigated. The most effective compound was sodium 2-((4-phenyl-5-thiophene-3-ylmethyl)-1,2,4-triazole-3-yl)thio)acetate, which exceeded the activity of both reference drugs. Following in activity was compound 22, 1-phenyl-2-((4-phenyl-5-(thiophene-3-ylmethyl)-4H-1,2,4-triazole-3-yl)thio)ethanol, which demonstrated an effect similar to that of emoxipine, while compound 7, 1-(3-fluorophenyl)-2-((5-thiophene-3-ylmethyl)-4H-1,2,4-triazole-3-yl)thio)ethanone, was slightly less active. Conclusions. It was established that among the new S-derivatives of 1,2,4-triazole, some exhibit significant antioxidant effects that are comparable to or exceed the efficacy of reference drugs.

Mn-Fe Dual-Metal Assemblages on Carbon-Coated Al2O3 Spheres for Catalytic Ozonation Oxidation: Structure, Performance, and Reaction Mechanism.

Catalysts with high catalytic activity and low production cost are important for industrial application of heterogeneous catalytic ozonation (HCO). In this study, we designed a carbon-coated aluminum oxide carrier (C-Al2O3) and reinforced it with Mn-Fe bimetal assemblages to prepare a high-performance catalyst Mn-Fe/C-Al2O3. The results showed that the carbon embedding significantly improved the abundance of surface oxygen functional groups, conductivity, and adsorption capacity of γ-Al2O3, while preserving its exceptional mechanical strength as a carrier. The prepared Mn-Fe/C-Al2O3 catalyst exhibited satisfactory catalytic ozonation activity and stability in the degradation of p-nitrophenol (PNP). Electron paramagnetic resonance (EPR) and quenching experiments reveal that radical ( ⋅ OH and ⋅ O2 ⋅ ) and nonradical oxidation (1O2) dominated the PNP degradation process. Theoretical calculations corroborated that the anchored atomic Fe and Mn sites regulated the local electronic structure of the catalyst. This modulation effectively promoted the activation of O3 molecules, resulting in the generation of atomic oxygen species (AOS) and reactive oxygen species (ROS). The economic analysis on Mn-Fe/C-Al2O3 revealed that it was a cost-competitive catalyst for HCO. This study not only deepens the understanding on the reaction mechanism of HCO with transition metal/carbon composite catalysts, also provides a high-performance and cost-competitive ozone catalyst for prospective application.

Efficient Water Reforming of Biomass to H2 via Well-Organized Redox-Neutral Cleavage of C-C, O-H and C-H Bonds.

Hydrogen (H2) is a clean and environmentally friendly energy carrier. The depletion of fossil fuels makes renewable H2 production highly desirable. Water reforming of renewable biomass to hydrogen, with a relay of natural photosynthesis to biomass, would be an indirect pathway to realize the ideal but extremely challenging photocatalytic overall water splitting to hydrogen, with favorable thermodynamics. Since the seminal work of water reforming of biomass in 1980, great endeavors have been made. Nevertheless, hitherto, the entire kinetic pathway has been elusive, which seriously limits the reforming processes. Using a designed well-organized redox-neutral cleavage of C-C, O-H and C-H bonds enabled by photoelectrocatalysis, here, we show the efficient water reforming of biomass to hydrogen at room temperature, with a yield up to 93 %. The clear insights into the kinetic pathway with oxidation of carbon radicals to carbon cations as the indicated rate-determining step, would cast brightness for efficient and sustainable hydrogen production to accelerate the hydrogen economy.

Efficient Water Reforming of Biomass to H2 via Well‐Organized Redox‐Neutral Cleavage of C−C, O−H and C−H Bonds

AbstractHydrogen (H2) is a clean and environmentally friendly energy carrier. The depletion of fossil fuels makes renewable H2 production highly desirable. Water reforming of renewable biomass to hydrogen, with a relay of natural photosynthesis to biomass, would be an indirect pathway to realize the ideal but extremely challenging photocatalytic overall water splitting to hydrogen, with favorable thermodynamics. Since the seminal work of water reforming of biomass in 1980, great endeavors have been made. Nevertheless, hitherto, the entire kinetic pathway has been elusive, which seriously limits the reforming processes. Using a designed well‐organized redox‐neutral cleavage of C−C, O−H and C−H bonds enabled by photoelectrocatalysis, here, we show the efficient water reforming of biomass to hydrogen at room temperature, with a yield up to 93 %. The clear insights into the kinetic pathway with oxidation of carbon radicals to carbon cations as the indicated rate‐determining step, would cast brightness for efficient and sustainable hydrogen production to accelerate the hydrogen economy.

Effects of hydroxyl radical oxidation on the structural and functional properties of mutton myosin

Effects of hydroxyl radical oxidation on the structural and functional properties of mutton myosin

α-Nucleophilic Addition to α,β-Unsaturated Carbonyl Compounds via Photocatalytically Generated α-Carbonyl Carbocations.

We report the photocatalytic oxidation of α-carbonyl radicals of amides or esters to the corresponding α-carbonyl carbocations through super photoreductant CBZ6 induced redox-neutral photocatalysis. The α-carbonyl radicals are formed by the β-addition of alkyl radicals generated in situ by the photocatalytic fragmentation of N-hydroxyphthalimide esters to the α,β-unsaturated amides and esters. This method enables the α-nucleophilic addition of hydroxyl or alkoxyl radicals to amides and esters without any prefunctionalization.

The status of erythrocyte glutathione in clinical medicine: reality and possibilities

The review examines the current state of free radical oxidation processes in clinical medicine. Based on many years of our research and analysis of the literature, we consider the most promising assessment of the activity of glutathione reductase and the level of glutathione reduced in erythrocytes, as a characteristic of the thiol-disulfide redox system of glutathione, not only to indicate oxidative stress, but also a possible prognostic marker of “free radical diseases”.

Nitrite leads to the formation of N-nitrosodimethylamine during sulfate radical oxidation of dimethylamine compounds

Sulfate radical (SO4•−) advanced oxidation processes (SR-AOPs) are efficient for degrading a broad spectrum of contaminants. This study demonstrates that the existence of environmentally relevant concentrations of nitrite (NO2−) can lead to the formation of N-nitrosodimethylamine (NDMA), a probable human carcinogen, when heat activated peroxydisulfate (heat/PDS) is applied to address contaminants with dimethylamine moieties, such as tetracyclines. NO2− effectively competes with tetracyclines for SO4•− at a high second-order reaction rate constant of 8.8×108 M−1s−1, thus suppressing the degradation. Simultaneously, SO4•− reacts with NO2− to form the nitrogen dioxide radical (NO2•) which rapidly dimerizes to a potent nitrosating agent named dinitrogen tetroxide (N2O4). N2O4, in turn, attacks the dimethylamine moiety in tetracyclines via nucleophilic substitution, contributing to the degradation of parent compounds and generating an active intermediate that quickly decomposes to NDMA, along with the release of R+ and NO3−. The released R+ can be further oxidized by SO4•− to form phenolic intermediates which combine with NO2• to generate nitrated products. When 5 μM oxytetracycline (OTC) was treated with 0.5 mM PDS in the presence of 20 μM NO2− at 60 ℃, the highest formation of NDMA was 0.045 μM in 1 h. NDMA formation was also observed for other compounds with dimethylamine moieties, such as methylene blue, phenylurea herbicides, etc., with the molar yield ranging from 0.07 to 3.53%, negatively related to the R-N bond dissociation energy of the precursors. These findings suggest that NDMA can be commonly generated when SO4•− is applied to the degradation of dimethylamine pollutants in wastewater treatment or groundwater remediation where NO2− ubiquitously exists, which may pose a serious threat to the aquatic environment.

Mechanism of lipid peroxidation of liposomes by cold atmospheric pressure plasma jet irradiation.

Liposome lipid peroxidation induced by cold atmospheric pressure plasma jet (CAPPJ) irradiation was investigated. The formation of thiobarbituric acid reactive substances (TBARS), an indicator of lipid peroxidation final products, as a function of irradiation was observed. Lipid radicals, peroxidation reaction intermediates generated by CAPPJ irradiation, were confirmed by increased NBD-pen fluorescence intensity. Additionally, lipid peroxidation products, liposomal phosphatidylcholine (PC) isomers, were analyzed by LC-MS/MS. Products specific to singlet oxygen (1O2) oxidation, 16:0/10-hydroperoxy-8E,12Z-octadecanoic acid (10-8E,12Z-HpODE) PC and 16:0/12-9E,13E-HpODE PC, were not detected, but radical oxidation specific products 16:0/13-9E,11E-HpODE PC and 16:0/9-10E,12E-HpODE PC were. This suggests that during CAPPJ irradiation, radicals, rather than 1O2, are the primary reactive species of lipid peroxidation. This is also supported by the β-carotene quenching of 1O2 not suppressing TBARS and lipid radical generation. Also, neither TBARS formation nor lipid radical generation were suppressed by SOD, indicating that the superoxide radical (O2 •-) is not responsible for the lipid peroxidation reaction. As the CAPPJ irradiation of water produces large quantities of hydroxyl radical (•OH) and •OH scavengers decreased the amount of TBARS produced by CAPPJ irradiation, it is highly plausible that •OH is the primary species involved in CAPPJ-induced liposome lipid peroxidation.

Assessment of clinical and laboratory parameters of oral сavity in patients with orthodontic systems

equipment (braces) on the biochemical parameters of oral fluid. Materials and methods. The study involved patients aged 18 to 22 years who are undergoing orthodontic treatment with a bracket system. Thegroup of examined persons was 25 people. The control group included 15 practically healthy people without braces. All patients underwent dental status assessment (Green – Vermillion hygiene index – simplified IG-Y; PMA inflammation index), laboratory examination of oral fluid before and after controlled oral hygiene. The biochemical analysis included determination of the acid-base balance in the oral fluid using a pH meter, assessment of free radical oxidation by chemiluminogram parameters by biochemiluminescence and by levels of molecular products of lipid peroxidation (diene and triene conjugates, Schiff bases), activity of the enzyme alkaline phosphatase, concentrations of total protein and lactate. Results and discussions. In patients undergoing orthodontic treatment with a bracket system, an insufficient level of oral hygiene and inflammatory manifestations in the gums of moderate severity were revealed. The level of the acid-base balance of the oral fluid before controlled hygiene was equal to 6.8±0.19, that is, below the range of normal pH values in the oral cavity. After hygiene, the pH of the oral fluid returned to the norm of 7.1±0.2. In patients with braces, activation of free radical oxidation and an increase in lipoperoxidation parameters – triene conjugates and Schiff bases, increased activity of alkaline phosphatase, total protein and lactate levels took place.Cоnclusion. After hygienic treatment of the oral cavity, the biochemical parameters did not differ statistically significantly from the control data.

New insights into the improved contaminants removal in SBR by intermittently weak ultrasound

The combination of intermittently weak ultrasound and sequencing batch reactor was thoroughly investigated to elucidate the relationship between enhanced contaminants removal and activated sludge characteristics, microbial composition, and regulation of differentially expressed genes (DEGs). At 12 °C, irradiation with an ultrasound intensity of 9.68 W/L, an irradiation time of 10 min, and an interval time of 24 h led to significant increases in COD, NH4+−N, and TP removals with the rates of 93.10 ± 1.51%, 95.75 ± 0.76%, and 92.52 ± 0.95%, respectively. The intermittently weak ultrasound enhanced contaminants removal was primarily attributed to the stimulated microbial metabolism, in which the mechanical oscillation rather than free radical oxidation facilitated the loosening of activated sludge flocs and promoted microorganism proliferation. Elevating the ultrasound intensity or irradiation time could weaken the effect of enhancing ammonia−oxidizing bacteria activity and suppressing nitrite−oxidizing bacteria activity. The results revealed that intermittently weak ultrasound primarily affected the extracellular polymeric substances (EPS), with protein nitrogen playing a more significant role than polysaccharide within EPS against ultrasound−induced stress. Furthermore, ultrasound irradiation elevated the energy barrier in total−binding EPS interaction energy curves, thereby inhibiting activated sludge aggregation. Over prolonged operation, the relative abundance of the prevalent denitrifying genus Thauera increased by 90.3%, whereas that of the fully aerobic denitrifier and nitrite producer Dokdonella increased by 68.7%. The intermittently weak ultrasound induced enhancement of microbial metabolism−related DEGs pathways, which served as the main contributor to the improved contaminants removal. These findings provide novel insights into the mechanisms by which intermittently weak ultrasound enhances the effectiveness of biological wastewater treatment.

Tuning Co-Operative Energy Transfer in Copper(I) Complexes Using Two-Photon Absorbing Diimine-Based Ligand Sensitizers.

Photocatalysis mediated by low energy light wavelengths has potential to enable safer, sustainable synthetic methods. A phenanthroline-derived ligand bathocupSani, with a large two-photon absorption (TPA) cross section was used to construct a heteroleptic complex [Cu(bathocupSani)(DPEPhos)]BF4 and a homoleptic complex [Cu(bathocupSani)2]BF4. The ligand and the respective homoleptic complex with copper exhibit two-photon upconversion with an anti-Stokes shift of 1.2 eV using red light. The complex [Cu(bathocupSani)2]BF4 promoted energy transfer photocatalysis enabling oxidative dimerization of benzylic amines, sulfide oxidation, phosphine oxidation, boronic acid oxidation and atom-transfer radical addition.