Ti3+/Ti4+ and Co2+/Co3+ redox couples in Ce-doped Co-Ce/TiO2 for enhancing photothermocatalytic toluene oxidation.

Cerium and cobalt loaded Co-Ce/TiO2 catalyst prepared by impregnation method was investigated for photothermal catalytic toluene oxidation. Based on catalyst characterizations (XPS, EPR and H2-TPR), redox cycle between Co and TiO2 (Co2+ + Ti4+ ↔ Co3+ + Ti3+) results in the formation of Co3+, Ti3+ and oxygen vacancies, which play important roles in toluene catalytic oxidation reaction. The introduction of Ce brings in the dual redox cycles (Co2+ + Ti4+ ↔ Co3+ + Ti3+, Co2+ + Ce4+ ↔ Co3+ + Ce3+), further promoting the elevation of reaction sites amount. Under full spectrum irradiation with light intensity of 580 mW/cm2, Co-Ce/TiO2 catalyst achieved 96% of toluene conversion and 73% of CO2 yield, obviously higher than Co/P25 and Co/TiO2. Co-Ce/TiO2 efficiently maintains 10-hour stability test under water vapor conditions and exhibits better photothermal catalytic performance than counterparts under different wavelengths illumination. Photothermal catalytic reaction displays improved activities compared with thermal catalysis, which is attributed to the promotional effect of light including photocatalysis and light activation of reactive oxygen species.

A critical review of Mnammox coupled with the NDMO for innovative nitrogen removal.

In the context of increasing global nitrogen pollution, traditional biological nitrogen removal technologies like nitrification and denitrification are hindered by high energy consumption. Additionally, the deployment of anaerobic ammonium oxidation (Anammox) technology is constrained due to the slow growth rate of Anammox bacteria and there is a bottleneck in nitrogen removal efficiency. To overcome these technical bottlenecks, researchers have discovered a revolutionary nitrogen removal technology that cleverly combines the redox cycling of manganese with nitrification and denitrification reactions. In this new process, manganese dependent anaerobic ammonium oxidation (Mnammox) bacteria can convert NH4+ to N2 under anaerobic conditions, while nitrate/nitrite dependent manganese oxidation (NDMO) bacteria use NO3-/NO2- as electron acceptors to oxidize Mn2+ to Mn4+. Mn4+ acts as an electron acceptor in Mnammox reaction, thereby realizing the autotrophic nitrogen removal process. This innovative method not only simplifies the steps of biological denitrification, but also significantly reduces the consumption of oxygen and organic carbon, providing a more efficient and environmentally friendly solution to the problem of nitrogen pollution. The article initially provides a concise overview of prevalent nitrogen removal technologies and the application of manganese in these processes, and discusses the role of manganese in biogeochemical cycles, including its discovery, mechanism of action, microbial communities involved, and its impact on these key factors in the process. Subsequently, metabolic principles, benefits, advantages, and environmental considerations of Mnammox coupled with the NDMO process are analyzed in detail. Finally, this article summarizes the shortcomings of current research and looks forward to future research directions. The goal of this article is to provide a valuable reference for researchers to fully understand the application of manganese in nitrogen removal processes.

Remediation of AMD based on hydrogeochemical zonation: A typical metal mine in China.

Mining activities disrupt the natural oxidative balance underground, increasing the oxidation of metal sulfides like pyrite. This process leads to the formation of highly acidic mine drainage (AMD) with elevated concentrations of iron (Fe) and sulfate (SO42-). However, generic plugging and backfilling methods, when applied without considering the specific post-mining oxidative environments of different metal mines, often yields minimal results. To clarify the distribution of the underground redox environment after mining of a metal mine in Dexing, China, fifteen water samples from flood and dry periods, as well as fifteen borehole samples, were collected for hydrogeological and chemical analysis. For the first time, the study proposed that the redox zone could be identified and delineated through vertical analysis of water storage media, mineral composition, and hydrochemical characteristics. A hydrogeochemical cause model was constructed, revealing that AMD formation primarily occurs in oxidative and transition zones. Based on the redox zone characteristics of the study area, actual engineering sealing was performed on the oxidation and transition zones of cavity No. 23. As a result, the pH increased from 2.5 before remediation to 4.5, indicating a reduction in acidity. The concentrations of SO42- and Fe significantly decreased, reducing from 1360.0 mg/L and 147.0 mg/L before treatment to 726.0 mg/L and 23.6 mg/L after treatment; the total decrease amounting to 46.6 % and 84.0 %, respectively. The concentrations of Mn and Cu similarly, decreased by 10.7 % and 15.6 %, respectively. This study provides a novel approach and valuable reference for the refined identification and classification of redox zones after metal mine exploitation, as well as for the targeted plugging and treatment of cavities that produce AMD.

Linking sediment geochemistry with catchment processes, internal phosphorus loading and lake water quality.

Research in the field of sediment geochemistry suggests potential linkages between catchment processes (land use), internal phosphorus (P) loading and lake water quality, but evidence is still poorly quantified due to a limited amount of data. Here we address the issues based on a comprehensive data set from 27 lakes in southern Finland. Specifically, we aimed at: 1) elucidating factors behind spatial variations in sediment geochemistry; 2) assessing the impact of diagenetic transformation on sediment P regeneration across lakes based on the changes in the vertical distribution of sediment components; 3) exploring the role of the sediment P forms in internal P loading (IL), and 4) determining the impact of IL on lake water quality. The relationship between sediment P concentration and field area percentage (FA%) was statistically significant in (mainly eutrophic) lakes with catchments that included more than 10 % of fields. We found that sediment iron-bound P (Fe-P) increased with increasing FA%, which agrees with the high expected losses from the cultivated areas. Additionally, populated areas increased the pool of sediment Fe-P. Internal P loading was significantly positively related to both sediment Fe-P and sediment organic P (Org-P). However, Org-P was not significant (as the third predictor) in models that had a trophic state variable as the first predictor and Fe-P as the second predictor. Further, the vertical profiles of sediment components indicated a role of diagenetic transformations in the long-term sediment P release, especially in lakes with deeper maximum depth and longer water residence time. Finally, IL was significantly positively correlated to water quality variables including phytoplankton biomass, its proportion of cyanobacteria, chlorophyll a concentration and trophic state index. Our findings suggest that reduction of P losses from the field and populated areas will decrease internal P loads and increase water quality through a reduced pool of Fe-P.

Introducing Phosphorus into the Overcrowded Thiele's hydrocarbon Family: Unveiling Contorted Main Group Diradicaloids with Dynamic Redox Behavior.

Thiele's Hydrocarbons (THs) featuring a 9,10-anthrylene core with switchable geometric and electronic configurations offer exciting possibilities in advanced functional materials. Despite significant advances in main group-based diradicaloids in contemporary chemistry, main group THs containing an anthrylene cores have remained elusive, primarily due to the lack of straightforward synthetic strategies and the inherent high reactivity of these species. In this study, we utilize an anthracene-based phosphine synthon to demonstrate, for the first time, a facile and high-yielding synthetic strategy for robust P-functionalized overcrowded ethylenes (OCEs) within the TH family. These OCEs feature a non-symmetric environment, incorporating (thio)xanthyl and phosphaalkene termini. We systematically probe the electronic structures of these derivatives to illustrate the impact of the isolobal phosphaalkene motif on the quinoidal/diradicaloid character. Notably, the compounds exhibit dynamic redox behavior, leading to orthogonally twisted conformational changes upon oxidation, with a kinetically locked redox-couple.

Passively administered fluoxetine reaches the juvenile brain of FSL rats and reduces antioxidant defences, without altering serotonin turnover.

BACKGROUND: Fluoxetine is present in breast milk, yet it is unclear to what extent it, or its active metabolite, norfluoxetine, reaches the brain of the infant and what the effects of such exposure on neurobiological processes are. We therefore aimed to quantify the concentration of passively administered fluoxetine and norfluoxetine in the whole brains of exposed Flinders sensitive line (FSL) offspring and establish their influence on serotonergic function and redox status. METHODS: Adult FSL dams received fluoxetine (10 mg/kg/day), or placebo for fourteen days, beginning on postpartum day 04. Offspring were passively exposed to fluoxetine until postnatal day 18 and euthanized on postnatal day 22. Whole brain fluoxetine, norfluoxetine, serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), and reduced (GSH) and oxidized glutathione (GSSG) concentrations were measured via liquid chromatography-mass spectrometry (LC-MS) analysis. RESULTS: Whole-brain serotonin and 5-hydroxyindoleacetic acid concentrations, and serotonin turnover (5-HIAA/5-HT) were comparable between strains. Treatment-naïve FSL rats had lower GSH and higher GSSG whole-brain concentrations, relative to FRL controls, and an overall decreased GSH/GSSG ratio. Passively administered fluoxetine resulted in undetectable whole-brain concentrations, while norfluoxetine averaged 41.28 ± 6.47 ng/g. Serotonin turnover of FSL rats was unaffected by passively administered fluoxetine, while redox status (GSH/GSSG) was decreased. CONCLUSION: Our findings confirm that passively administered fluoxetine reaches the infant brain in the form of norfluoxetine and may manipulate processes of oxidative stress regulation. Further studies into the long-term bio-behavioural effects are however needed to effectively inform breast feeding mothers on the safety of antidepressant-use.

The role of ascorbate redox turnover in iron toxicity tolerance.

Iron (Fe) toxicity is a major abiotic stress in lowland rice production. Breeding tolerant varieties has proven challenging due to the complex genetic architecture of Fe toxicity tolerance and the strong genotype-by-environment interactions. Additionally, conventional methods for phenotyping visible stress symptoms are often inaccurate, inconsistent, and lack reproducibility. In our previous work, we identified that ascorbate redox regulation, mediated by the activities of dehydroascorbate reductase (DHAR) and ascorbate oxidase (AO), contributed to high tolerance in an indica rice genotype across various environments. To explore whether this mechanism is common among other rice genotypes, we selected ten genotypes with contrasting stress symptoms under Fe-toxic conditions to examine the roles of DHAR and AO in regulating Fe toxicity tolerance. Additionally, we aimed to develop objective and accurate image-based phenotyping methods to replace the traditional leaf bronzing scoring method. Among the ten genotypes we tested, we found significant positive correlations between DHAR activity and stress symptoms in plants grown under both Fe toxicity and control conditions, suggesting a general link between ascorbate redox regulation and Fe toxicity tolerance. Using RGB signals from leaf images of plants exposed to 1000 mg/L Fe2+, we evaluated 36 different color indices to quantify stress symptoms. We identified the normalized green‒red difference index as most significant in quantifying stress symptoms under Fe toxicity conditions. Our findings suggest that DHAR activity could be potentially employed as a biomarker in the screening of rice germplasms and breeding tolerant cultivars to Fe toxicity.

Synergy of atomic hydrogen reduction and reactive oxygen species oxidation over confined Mn bifunctional site for electrocatalytic deep mineralization.

Traditional reduction or oxidation processes generating one-component free radicals face challenges in deep dechlorination and mineralization of chlorophenols from wastewater. Herein, an efficient electrocatalytic process has been developed, which couples atomic H* reduction with reactive oxidation species (•OH and 1O2) oxidation on a bifunctional cathode for 4 -chlorophenol (4 -CP) removal. The N - doped carbon nanotubes encapsulated manganese nanoparticles was fabricated as cathode, which could generate atomic H* , initiating nucleophilic hydrodechlorination in presence of confined MnO sites. Subsequently, electrophilic oxidation by generating mainly 1O2 on confined Mn7C3 sites and •OH on confined MnO sites, facilitating the oxidative processes. Experimental results and theory calculations demonstrated that reductive dechlorination and oxidative mineralization processes could mutually promote each other, resulting in an enhancement factor of 2.90. At pH 7, this process achieved 100 % removal for 4 -CP, 84 % dechlorination, 76 % total organic carbon (TOC) removal and low energy consumption (0.76 kWh g-1TOC) within 120 min. Notably, TOC for chlorophenols containing Cl substituents at different positions and real lake water containing 4 -CP could be almost completely removed. This research establishes confined non-noble bifunctional active sites that synergistically enhance reductive dechlorination and oxidative degradation processes, holding significant treatment potential for application in deep mineralization of organochlorine from water/wastewater.

Topiroxostat improves glomerulosclerosis in type 2 diabetic Nagoya Shibata Yasuda mice with early nephropathy.

Reactive oxygen species production might be prevented by xanthine oxidoreductase (XOR) inhibitors, which can cause glomerulosclerosis. We aimed to investigate whether topiroxostat, an XOR inhibitor, prevents diabetic kidney disease development in mice. Six-week-old control Institute of Cancer Research (ICR) mice and type-2 diabetic Nagoya Shibata Yasuda (NSY) mice were divided into the ICR group (ICR mice who received a lard-containing high-fat diet [HFD] based on the AIN-93G diet), NSY control group (NSY mice who received the same aforementioned diet), and NSY+topiroxostat group (NSY mice who received the same aforementioned diet with addition of 0.0012% topiroxostat). After 20 weeks, plasma biomarkers, XOR activity and oxidative stress levels, which were assessed using malondialdehyde (MDA), were measured through enzyme-linked immunosorbent assay or enzymatic methods. Kidney pathology was evaluated using periodic acid-Schiff staining. Redox gene and protein expression were determined using RT-qPCR and western blotting. Plasma XOR activity was lower in NSY mice treated with topiroxostat than those without. Plasma cystatin C and creatinine levels did not differ between the ICR and NSY control groups or between the NSY control and NSY+topiroxostat groups. The NSY+topiroxostat group showed a smaller mesangial area than the NSY control group. The mRNA expression of Sod3, Prdx1, Gpx2, and Gpx3 was higher in the NSY+topiroxostat group than in the NSY control group. Renal MDA levels were lower in the NSY+topiroxostat group than in the HFD control group. Topiroxostat can reduce glomerular sclerosis, and the reduction is associated with renal oxidative markers.

A Strategy to Mitigate Jahn Teller Effect of Mn-Rich NASICON Framework for Sodium-Ion Batteries.

Mn-based sodium superionic conductors have driven attention to the low-cost advanced cathode materials for sodium-ion batteries (SIBs). However, low-rate capability and unsatisfactory cyclic performance due to the Jahn teller effect of Mn3+ redox couple which occurs from the change in Mn-O bond length at the octahedral site of crystal structure during charge-discharge, eventually limiting their application. Herein, a disordered and sodium deficient NASICON Na4-xMn(FeVCrTi)0.25(PO4)3 (termed as Na4-xMn(HE)) is synthesized to mitigate this Jahn teller effect to achieve high rate and ultrastable cathode material. Interestingly, the as-prepared Na3.5Mn(HE) shows five reversible electron reactions (i.e., Ti3+/Ti4+, Fe2+/Fe3+, V3+/V4+, Mn2+/Mn3+, and Mn3+/Mn4+) and demonstrates 141 mA h g-1 at 0.2 C with 80% capacity retention at 1 C after 500 cycles which is far superior to its counterparts binary Mn-based materials. The excellent cyclic performance is due to the remediation of the Jahn teller effect in sodium-deficient entropy-stabilized material. The structural reversibility, enhanced kinetics, and electronic properties are further studied in detail by in situ X-ray diffraction (XRD), ex situ X-ray photoelectron spectroscopy (XPS), and first principal calculations. Na3.5Mn(HE)//HC full cell delivered 89.7 mAh g-1 capacity at 0.2 C. This work sheds light on designing Mn-based cathodes with superior electrochemical performance for wide energy storage applications.

Chromium(II)-isophthalate 2D MOF with Redox-Tailorable Gas Adsorption Selectivity.

Redox-active metal-organic frameworks (MOFs) are very promising materials due to their potential capabilities for postsynthetic modification aimed at tailoring their application properties. However, the research field related to redox-active MOFs is still relatively underdeveloped, which limits their practical application. We investigated the self-assembly process of Cr(II) ions and isophthalate (m-bdc) linkers, which have been previously demonstrated to yield 0D metal-organic polyhedra. However, using the diffusion-controlled synthetic approach, we demonstrate the selective preparation of a 2D-layered Cr(II)-based MOF material [Cr(m-bdc)]·H2O (1·H2O). Remarkably, the controlled oxidation of the developed 2D MOF using nitric oxide or dry oxygen resulted in modified porous materials with excellent H2/N2 adsorption selectivities.

Demystifying anaerobic respiration: a problem-solving exercise.

Anaerobic respiration reactions are of fundamental importance to global biogeochemical cycling of elements. Yet, the idea that cellular respiration can occur not only in the absence of oxygen but also involve the oxidation of inorganic substrates (e.g., AsO33-, Fe2+, H2, H2S, Mn2+, NH3, and S0) is often foreign to many undergraduate students. This article describes a problem-solving exercise where students are introduced to the thermodynamic fundamentals of respiration with a particular focus on the role of redox (reduction-oxidation) potentials (E0´). In the exercise, the students investigate how the difference in redox potential (ΔE0´) between different pairs of reductants and oxidants affects the range of permissible microbial metabolic reactions in natural environments when oxygen is absent.

Hesperetin-7-O-rhamnoglucoside ameliorates dichlorvos-facilitated cardiotoxicity in rats by counteracting ionoregulatory, ion pumps, redox, and lipid homeostasis disruptions.

The contamination of edible agricultural goods with pesticides, including dichlorvos (DVDP), poses a substantial public health risk, promoting severe morbidity and mortality, especially in developing countries. It has been shown that hesperidin (hesperetin-7-O-rhamnoglucoside or Hes-7-RGlc) preserves cytomembrane, redox, and lipid homeostasis; unfortunately, its function on dichlorvos-incited heart damage has not been investigated. This work explored the ameliorative influence of Hes-7-RGlc on DVDP-activated cardiotoxicity. For this end, forty-two rats were randomly appropriated into seven groups (6 rats/group): Control, DVDP alone (8 mg.kg⁻¹day⁻¹), DVDP supplied with either Hes-7-RGlc (50 and 100 mg.kg⁻¹day⁻¹) or the reference medication atropine (0.2 mg.kg⁻¹day⁻¹), and Hes-7-RGlc alone (50 and 10 mg.kg⁻¹day⁻¹) were the seven groups investigated. DVDP was administered orally for seven days, followed by fourteen days of Hes-7-RGlc therapy. Then the rats were euthanized, and their blood and hearts were removed. Hes-7-RGlc chemotherapy substantially (p<0.05) restored DVDP-elicited dynamics in plasma and cardiac/myocardium creatine kinase isoenzyme (CK-MB), major lipids (cholesterol, triacylglycerol, and phospholipids), electrolytes (Na⁺, K⁺, Ca²âº, Mg²âº, Cl⁻), and total protein. Hes-7-RGlc remedy decidedly (p<0.05) abolished DDVP-stimulated amplification in the cardiac concentration of H2O2, NO and malondialdehyde; annulled DVDP-educed decreases in heart GSH levels, activities of GST, SOD, catalase, and glutathione peroxidase, ion transporters (Na⁺/K⁺-ATPase and Ca²âº/Mg²âº-ATPase), ALT, AST, ALP, and LDH-1. Collectively, Hes-7-RGlc can be advocated as a natural supplementary candidate and blocker of DVDP-provoked heart deficits via its capacity to reverse disruptions of electrolytes, ion pumps, redox status, and lipid homeostasis.

Natural redox mediator anthraquinone aloe-emodin facilitated the in-situ mineralized γ-FeO(OH) membrane for the removal of tannic acid through photocatalytic-PMS activation.

The growing utilization of Traditional Chinese Medicine (TCM) has resulted in an increase in wastewater. Herein, a new kind of organic-inorganic redox mediator membrane by immobilizing γ-FeO(OH) and aloe-emodin(AE) with the characteristic large π-conjugation anthraquinone structure on PVDF membrane was innovatively achieved. AE exhibiting both electron deficiency and redox activity possesses a co-catalyst role in degradation of tannic acid (TA), aiding in the separation of charge carriers through the sequential hydrogenation and dehydrogenation of AE. The removal rates of TA were 92.8 % in the tannic acid solution and 60.3 % in the simulated rhubarb wastewater by the AE-γ-FeO(OH) membrane under PMS+Vis conditions in 45 min. Also, they show a higher recovery of pure water flux and owning good fouling performance. Overall, this current work presents a novel approach for the design and preparation of organic-inorganic photocatalytic composite membrane using readily available natural products for the purification TCM wastewater.

High-Electrochemical-Activity Composite Cathode Enabled by Fast Segmental Relaxation for Solid-State Lithium-Sulfur Batteries.

Solid-state lithium-sulfur batteries (SSLSBs) have attracted a great deal of attention because of their high theoretical energy density and intrinsic safety. However, their practical applications are severely impeded by slow redox kinetics and poor cycling stability. Herein, we revealed the detrimental effect of aggregation of lithium polysulfides (LiPSs) on the redox kinetics and reversibility of SSLSBs. As a paradigm, we introduced a multifunctional hyperbranched ionic conducting (HIC) polymer serving as a solid polymer electrolyte (SPE) and cathode binder for constructing SSLSBs featuring high electrochemical activity and high cycling stability. It is demonstrated that the unique structure of the HIC polymer with numerous flexible ether oxygen dangling chains and fast segmental relaxation enables the dissociation of LiPS clusters, facilitates the conversion kinetics of LiPSs, and improves the battery's performance. A Li|HIC SPE|HIC-S battery, in which the HIC polymer acts as an SPE and cathode binder, exhibits an initial capacity of 910.1 mA h gS-1 at 0.1C and 40 °C, a capacity retention of 73.7% at the end of 200 cycles, and an average Coulombic efficiency of approximately 99.0%, demonstrating high potential for application in SSLSBs. This work provides insights into the electrochemistry performance of SSLSBs and provides a guideline for SPE design for SSLSBs with high specific energy and high safety.

Redox-inducible Radiomimetic Photosensitizers Selectively Suppress Cancer Cell Proliferation by Damaging DNA through Radical Cation Chemistry.

Radiotherapy leverages ionizing radiation to kill cancer cells through direct and indirect effects, and direct effects are considered to play an equal or greater role. Several photosensitizers have been developed to mimic the direct effects of radiotherapy, generating radical cations in DNA models, but none has been applied in cellular studies. Here, we design a radiomimetic photosensitizer, producing DNA radical cations in cells for the first time. To reduce adverse effects, several redox-inducible precursors are prepared as cancer cells have elevated levels of GSH and H2O2. These precursors respond to GSH or H2O2, releasing the active photosensitizer that captures DNA abasic (AP) sites and generates DNA radical cations upon photolysis, without disrupting the redox state of cells. DNA radical cations migrate freely and are eventually trapped by H2O and O2 to yield DNA lesions, thus triggering DNA damage response. Our study suggests that direct effects of radiotherapy suppress cancer cell proliferation mainly by inducing G2/M phase cell cycle arrest, rather than promoting apoptosis. Synergistic effects of the precursor and chemotherapeutic agents are also observed in combination phototherapy. Beyond highlighting an alternative strategy for phototherapy, this proof-of-concept study affords a facile cellular platform to study the direct effects of radiotherapy.

Dual, Photo-Responsive and Redox-Active Supramolecular Foldamers.

We report on dual, light-responsive and redox-active foldamers that demonstrate reversible and robust stimuli-induced behaviour. Herein, UV/Vis, 1H NMR and circular dichroism (CD) spectroscopy and cyclic voltammetry have been used to establish the reversibility and highly robust nature of the light- and redox-driven behaviour of these new foldamers with minimal levels of fatigue observed even upon multiple cyclic treatments with irradiative/non-irradiative and oxidative/reductive conditions. This proof-of-concept work paves the way towards the creation of novel stimuli-responsive foldamers of increasing sophistication capable of demonstrating reversible and robust responses to multiple distinct stimuli.

FDX2, an iron-sulfur cluster assembly factor, is essential to prevent cellular senescence, apoptosis or ferroptosis of ovarian cancer cells.

Recent studies reveal that biosynthesis of iron-sulfur clusters (Fe-Ss) is essential for cell proliferation, including that of cancer cells. Nonetheless, it remains unclear how Fe-S biosynthesis functions in cell proliferation/survival. Here, we report that proper Fe-S biosynthesis is essential to prevent cellular senescence, apoptosis or ferroptosis, depending on cell context. To assess these outcomes in cancer, we developed an ovarian cancer line with conditional KO of FDX2, a component of the core Fe-S assembly complex. FDX2 loss induced global down-regulation of Fe-S-containing proteins and Fe2+ overload, resulting in DNA damage and p53 pathway activation, and driving the senescence program. p53-deficiency augmented DNA damage responses upon FDX2 loss, resulting in apoptosis rather than senescence. FDX2 loss also sensitized cells to ferroptosis, as evidenced by compromised redox homeostasis of membrane phospholipids (PLs). Our results suggest that p53 status and PL homeostatic activity are critical determinants of diverse biological outcomes of Fe-S deficiency in cancer cells.

Redox-Driven Formation of Mn(III) in Ice.

Redox-driven reactions involving Mn(II) species adsorbed at Mn(IV) oxide surfaces can release Mn(III) in the form of dissolved Mn(III)-ligand species in natural waters. Using pyrophosphate (PP) as a model ligand, we show that freezing accelerates and enhances Mn(III) formation in the form of Mn(III)-PP complexes. This freeze-promoted reaction is explained by the concentration of Mn(IV) oxides and solutes (Mn(II), Na+, and Cl-) into the minute fractions of liquid water locked between ice (micro)crystals - the Liquid Intergrain Boundary (LIB). Time-resolved freezing experiments at -20 °C showed that Mn(III) yields were greatest at low salt (NaCl) content. In contrast, high salt content promoted Mn(III) formation through chloride complexation, although yields became lower as the cryosalt mineral hydrohalite (NaCl·2H2O) dehydrated the LIB by drawing water into its structure. Consecutive freeze-thaw cycles also showed that dissolved Mn(III) concentrations increased within the very first few minutes of each freezing event. Because each thaw event released unreacted PP previously locked in ice, each sequential freeze-thaw cycle increased Mn(III) yields, until ∼80% of the Mn was converted to Mn(III). This was achieved after only seven cycles. Finally, temperature-resolved freezing experiments down to -50 °C showed that the LIB produced the greatest quantities of Mn(III) at -10 °C, where the volumes were greater. Reactivity was however sustained in ice formed below the eutectic (-21.3 °C), down to -50 °C. We suspect that this sustained reactivity was driven by persistent forms of supercooled water, such as Mn(IV) oxide-bound thin water films. By demonstrating the freeze-driven production of Mn(III) by comproportionation of dissolved Mn(II) and Mn(IV) oxide, this study highlights the potentially important roles these reactions could play in the production of pools of Mn(III) in natural water and sediments of mid- and high-latitudes environments exposed to freeze-thaw episodes.

Tributyltin-induced visceral adiposity is associated with impaired redox balance in white adipose tissue of male rats.

Tributyltin (TBT) is an organotin compound that has several adverse health effects, including the development of obesity. Although obesity is strongly associated with adipose redox imbalance, there is a lack of information on whether TBT promotes a pro-oxidative environment in WAT. Thus, adult male Wistar rats were randomly exposed to either vehicle (ethanol 0.4%) or TBT (1000 ng/kg) for 30 days. Body and fat pad masses, visceral fat morphology, lipid peroxidation, protein carbonylation, redox status markers, and catalase activity were evaluated. TBT promoted increased adiposity and visceral fat, with hypertrophic adipocytes, but did not alter body mass and subcutaneous fat. ROS production and lipid peroxidation were elevated in TBT group, as well as catalase protein expression and activity, although protein oxidation and glutathione peroxidase protein expression remained unchanged. In conclusion, this is the first study to demonstrate that subacute TBT administration leads to visceral adipose redox imbalance, with increased oxidative stress. This enlights the understanding of the metabolic toxic outcomes of continuous exposure to TBT in mammals.