Real-time observation of a metal complex-driven reaction intermediate using a porous protein crystal and serial femtosecond crystallography.

Determining short-lived intermediate structures in chemical reactions is challenging. Although ultrafast spectroscopic methods can detect the formation of transient intermediates, real-space structures cannot be determined directly from such studies. Time-resolved serial femtosecond crystallography (TR-SFX) has recently proven to be a powerful method for capturing molecular changes in proteins on femtosecond timescales. However, the methodology has been mostly applied to natural proteins/enzymes and limited to reactions promoted by synthetic molecules due to structure determination challenges. This work demonstrates the applicability of TR-SFX for investigations of chemical reaction mechanisms of synthetic metal complexes. We fix a light-induced CO-releasing Mn(CO)3 reaction center in porous hen egg white lysozyme (HEWL) microcrystals. By controlling light exposure and time, we capture the real-time formation of Mn-carbonyl intermediates during the CO release reaction. The asymmetric protein environment is found to influence the order of CO release. The experimentally-observed reaction path agrees with quantum mechanical calculations. Therefore, our demonstration offers a new approach to visualize atomic-level reactions of small molecules using TR-SFX with real-space structure determination. This advance holds the potential to facilitate design of artificial metalloenzymes with precise mechanisms, empowering design, control and development of innovative reactions.

[Quantitative Activity-Induced Manganese-Enhanced Magnetic Resonance Imaging: Principles, Applications, and Limitations].

Accurate identification of regions that show activity changes in response to functional expression is necessary to understand the mechanisms underlying functional expression in the brain. Quantitative activity-induced manganese-enhanced magnetic resonance imaging (qAIM-MRI) is a noninvasive whole-brain activity history imaging method used for this purpose. Notably, qAIM-MRI is a pseudo-Ca2+ imaging method that uses Mn2+ as a surrogate marker for Ca2+. In this paper, I describe the principles, applications, and limitations of qAIM-MRI.

Urine manganese, cadmium, lead, arsenic, and selenium among autism spectrum disorder children in Kuala Lumpur.

Background: The development of autism spectrum disorder (ASD) may stem from exposure to environmental pollutants such as heavy metals. The primary objective of this study is to determine the role of heavy metals of concern such as manganese (Mn), cadmium (Cd), lead (Pb), arsenic (As), and essential trace element selenium (Se) among ASD children in Kuala Lumpur, Malaysia. Method: A total of 155 preschoolers in Kuala Lumpur between the ages 3 to 6 participated in an unmatched case-control study, comprising ASD children (n = 81) recruited from an early intervention program for autism, and 74 children without autism who were recruited from public preschools. Urine samples were collected at home, delivered to the study site, and transported to the environmental lab within 24 hours. Inductively coupled plasma mass spectrometry (ICP-MS) was applied to measure the concentration of heavy metals in the samples. Data were analysed using bivariate statistical tests (Chi-square and T-test) and logistic regression models. Result: This study demonstrated that Cd, Pb, and As urine levels were significantly greater in children without autism relative to those affected with ASD (p < 0.05). No significant difference was in the levels of Se (p = 0.659) and Mn (p = 0.875) between children with ASD and the control group. The majority of children in both groups have urine As, Pb, and Cd values lower than 15.1 µg/dL, 1.0 µg/dL, and 1.0 µg/dL, respectively which are the minimal risk values for noncarcinogenic detrimental human health effect due to the heavy metal's exposure . Factors associated with having an ASD child included being a firstborn, male, and higher parental education levels (adjusted odds ratios (aOR) > 1, p < 0.05). Conclusion: Preschoolers in this study demonstrated low levels of heavy metals in their urine samples, which was relatively lower in ASD children compared to the healthy matched controls. These findings may arise from the diminished capacity to excrete heavy metals, especially among ASD children, thereby causing further accumulation of heavy metals in the body. These findings, including the factors associated with having an ASD child, may be considered by healthcare professionals involved in child development care, for early ASD detection. Further assessment of heavy metals among ASD children in the country and interventional studies to develop effective methods of addressing exposure to heavy metals will be beneficial for future reference.

Serum macroelements and microelements levels in periparturient dairy cows in relation to fatty liver diseases.

BACKGROUND: Fatty liver in dairy cows is a common metabolic disease defined by triglyceride (TG) buildup in the hepatocyte. Clinical diagnosis of fatty liver is usually done by liver biopsy, causing considerable economic losses in the dairy industry owing to the lack of more effective diagnostic methods. Therefore, this study aimed to investigate the potential utility of blood biomarkers for the diagnosis and early warning of fatty liver in dairy cows. RESULTS: A total of twenty-four lactating cows within 28 days after parturition were randomly selected as experimental animals and divided into healthy cows (liver biopsy tested, n = 12) and cows with fatty liver (liver biopsy tested, n = 12). Inductively coupled plasma mass spectrometry (ICP-MS) was used to determine the macroelements and microelements in the serum of two groups of cows. Compared to healthy cows (C), concentrations of calcium (Ca), potassium (K), magnesium (Mg), strontium (Sr), selenium (Se), manganese (Mn), boron (B) and molybdenum (Mo) were lower and copper (Cu) was higher in fatty liver cows (F). Meanwhile, the observed differences in macroelements and microelements were related to delivery time, with the greatest major disparity between C and F occurring 7 days after delivery. Multivariable analysis was used to test the correlation between nine serum macroelements, microelements and fatty liver. Based on variable importance projection and receiver operating characteristic (ROC) curve analysis, minerals Ca, Se, K, B and Mo were screened as the best diagnostic indicators of fatty liver in postpartum cows. CONCLUSIONS: Our data suggested that serum levels of Ca, K, Mg, Se, B, Mo, Mn, and Sr were lower in F than in C. The most suitable period for an early-warning identification of fatty liver in cows was 7 days after delivery, and Ca, Se, K, B and Mo were the best diagnostic indicators of fatty liver in postpartum cows.

PHD2 enzyme is an intracellular manganese sensor that initiates the homeostatic response against elevated manganese.

Intracellular sensors detect changes in levels of essential metals to initiate homeostatic responses. But, a mammalian manganese (Mn) sensor is unknown, representing a major gap in understanding of Mn homeostasis. Using human-relevant models, we recently reported that: 1) the primary homeostatic response to elevated Mn is upregulation of hypoxia-inducible factors (HIFs), which increases expression of the Mn efflux transporter SLC30A10; and 2) elevated Mn blocks the prolyl hydroxylation of HIFs by prolyl hydroxylase domain (PHD) enzymes, which otherwise targets HIFs for degradation. Thus, the mammalian mechanism for sensing elevated Mn likely relates to PHD inhibition. Moreover, 1) Mn substitutes for a catalytic iron (Fe) in PHD structures; and 2) exchangeable cellular levels of Fe and Mn are comparable. Therefore, we hypothesized that elevated Mn directly inhibits PHD by replacing its catalytic Fe. In vitro assays using catalytically active PHD2, the primary PHD isoform, revealed that Mn inhibited, and Fe supplementation rescued, PHD2 activity. However, a mutation in PHD2 (D315E) that selectively reduced Mn binding without substantially impacting Fe binding or enzymatic activity resulted in complete insensitivity of PHD2 to Mn in vitro. Additionally, hepatic cells expressing full-length PHD2D315E were less sensitive to Mn-induced HIF activation and SLC30A10 upregulation than PHD2wild-type. These results: 1) define a fundamental Mn sensing mechanism for controlling Mn homeostasis-elevated Mn inhibits PHD2, which functions as a Mn sensor, by outcompeting its catalytic Fe, and PHD2 inhibition activates HIF signaling to up-regulate SLC30A10; and 2) identify a unique mode of metal sensing that may have wide applicability.

High-temperature PTT/CDT coordination nanoplatform realizing exacerbated hypoxia for enhancing hypoxia-activated chemotherapy to overcome tumor drug resistance.

BACKGROUND: Hypoxia-activated prodrugs present new opportunities for safe and effective tumor drug resistance therapy due to their high selectivity for hypoxic cells. However, the uneven distribution of oxygen in solid tumor and insufficient hypoxia in the tumor microenvironment greatly limit its therapeutic efficacy. RESULTS: In this paper, a novel AQ4N-Mn(II)@PDA coordination nanoplatform was designed and functionalized with GMBP1 to target drug-resistant tumor cells. Its excellent photothermal conversion efficiency could achieve local high-temperature photothermal therapy in tumors, which could not only effectively exacerbate tumor hypoxia and thus improve the efficacy of hypoxia-activated chemotherapy of AQ4N but also significantly accelerate Mn2+-mediated Fenton-like activity to enhance chemodynamic therapy. Moreover, real-time monitoring of blood oxygen saturation through photoacoustic imaging could reflect the hypoxic status of tumors during treatment. Furthermore, synergistic treatment effectively inhibited tumor growth and improved the survival rate of mice bearing orthotopic drug-resistant tumors. CONCLUSIONS: This study not only provided a new idea for PTT combined with hypoxia-activated chemotherapy and CDT for drug-resistant tumors but also explored a vital theory for real-time monitoring of hypoxia during treatment.

Neuroprotective Strategies and Cell-Based Biomarkers for Manganese-Induced Toxicity in Human Neuroblastoma (SH-SY5Y) Cells.

Manganese (Mn) is an essential heavy metal in the human body, while excess Mn leads to neurotoxicity, as observed in this study, where 100 µM of Mn was administered to the human neuroblastoma (SH-SY5Y) cell model of dopaminergic neurons in neurodegenerative diseases. We quantitated pathway and gene changes in homeostatic cell-based adaptations to Mn exposure. Utilizing the Gene Expression Omnibus, we accessed the GSE70845 dataset as a microarray of SH-SY5Y cells published by Gandhi et al. (2018) and applied statistical significance cutoffs at p < 0.05. We report 74 pathway and 10 gene changes with statistical significance. ReactomeGSA analyses demonstrated upregulation of histones (5 out of 10 induced genes) and histone deacetylases as a neuroprotective response to remodel/mitigate Mn-induced DNA/chromatin damage. Neurodegenerative-associated pathway changes occurred. NF-κB signaled protective responses via Sirtuin-1 to reduce neuroinflammation. Critically, Mn activated three pathways implicating deficits in purine metabolism. Therefore, we validated that urate, a purine and antioxidant, mitigated Mn-losses of viability in SH-SY5Y cells. We discuss Mn as a hypoxia mimetic and trans-activator of HIF-1α, the central trans-activator of vascular hypoxic mitochondrial dysfunction. Mn induced a 3-fold increase in mRNA levels for antioxidant metallothionein-III, which was induced 100-fold by hypoxia mimetics deferoxamine and zinc.

Genome-Wide Identification of OsZIPs in Rice and Gene Expression Analysis under Manganese and Selenium Stress.

Zinc (Zn)- and iron (Fe)-regulating transport-like proteins (ZIPs) are a class of proteins crucial for metal uptake and transport in plants, particularly for Zn and Fe absorption and distribution. These proteins ensure the balance of trace elements essential for plant growth, development, and metabolic activities. However, the role of the rice (Oryza sativa) OsZIP gene family in manganese (Mn) and selenium (Se) transport remains underexplored. This research conducted an all-sided analysis of the rice OsZIPs and identified 16 OsZIP sequences. Phylogenetic analysis categorized the OsZIPs predominantly within the three subfamilies. The expression levels of OsZIPs in rice root and leaf subjected to Mn and Se toxicity stress were examined through quantitative real-time PCR (qRT-PCR). The findings revealed significant differential expression of many OsZIPs under these conditions, indicating a potential regulating effect in the response of rice to Mn and Se toxicity. This work lays a foundation for further functional studies of OsZIPs, enhancing our understanding of the response mechanisms of rice to Mn and Se toxicity and their roles in growth, development, and environmental adaptation.

Experimental and computational study on morin and its complexes with Mg2+, Mn2+, Zn2+, and Al3+: Coordination and antioxidant properties.

Morin (MRN), an intriguing bioflavonol, has received increasing interest for its antioxidant properties, as have its metal complexes (Mz+-MRN). Understanding their antioxidant behavior is critical to assess their pharmaceutical, nutraceutical potential, and therapeutic impact in the design of advanced antioxidant drugs. To this end, knowing the speciation of different H+-MRN and Mz+-MRN is pivotal to understand and compare their antioxidant ability. In this work, the protonation constant values of MRN under physiological ionic strength and temperature conditions (I = 0.15 mol L-1 and t = 37 °C), determined by UV-vis spectrophotometric titrations, are introduced. Thus, a reliable speciation model on H+-MRN species in aqueous solution is presented, which exhibits five stable forms depending on pH, supplemented by quantum-mechanical calculations useful to determine the proton affinities of each functional group and corresponding deprotonation order. Furthermore, potentiometry and UV-vis spectrophotometry have been exploited to determine the thermodynamic interaction parameters of MRN with different metal cations (Mg2+, Mn2+, Zn2+, Al3+). The antioxidant ability of H+-MRN and Mz+-MRN has been evaluated by the 2,2'-diphenyl-1-benzopyran-4-one (DPPH) method, and the Zn2+-MRN system has proven to afford the most potent antioxidant effect. Ab initio molecular dynamics simulations of Mz+-MRN species at all possible chelation sites and under explicit water solvation allowed for the fine characterization not only of the metal chelation modalities of MRN in explicit water, but also of the role played by the local water environment around the metal cations. Those microscopic patterns reveal to be informative on the different antioxidant capabilities recorded experimentally.

Rapid Determination of Cr3+ and Mn2+ in Water Using Laser-Induced Breakdown Spectroscopy Combined with Filter Paper Modified with Gold Nanoclusters.

Excessive emissions of heavy metals not only cause environmental pollution but also pose a direct threat to human health. Therefore, rapid and accurate detection of heavy metals in the environment is of great significance. Herein, we propose a method based on laser-induced breakdown spectroscopy (LIBS) combined with filter paper modified with bovine serum albumin-protected gold nanoclusters (LIBS-FP-AuNCs) for the rapid and sensitive detection of Cr3+ and Mn2+. The filter paper modified with AuNCs was used to selectively enrich Cr3+ and Mn2+. Combined with the multi-element detection capability of LIBS, this method achieved the simultaneous rapid detection of Cr3+ and Mn2+. Both elements showed linear ranges for concentrations of 10-1000 µg L-1, with limits of detection of 7.5 and 9.0 µg L-1 for Cr3+ and Mn2+, respectively. This method was successfully applied to the determination of Cr3+ and Mn2+ in real water samples, with satisfactory recoveries ranging from 94.6% to 105.1%. This method has potential application in the analysis of heavy metal pollution.

Elevated thyroid manganese reduces thyroid iodine to induce hypothyroidism in mice, but not rats, lacking SLC30A10 transporter.

Elevated manganese (Mn) accumulates in the brain and induces neurotoxicity. SLC30A10 is an Mn efflux transporter that controls body Mn levels. We previously reported that full-body Slc30a10 knockout mice (1) recapitulate the body Mn retention phenotype of humans with loss-of-function SLC30A10 mutations and (2) unexpectedly develop hypothyroidism induced by Mn accumulation in the thyroid, which reduces intra-thyroid thyroxine. Subsequent analyses of National Health and Nutrition Examination Survey data identified an association between serum Mn and subclinical thyroid changes. The emergence of thyroid deficits as a feature of Mn toxicity suggests that changes in thyroid function may be an underappreciated, but critical, modulator of Mn-induced disease. To better understand the relationship between thyroid function and Mn toxicity, here we further defined the mechanism of Mn-induced hypothyroidism using mouse and rat models. Slc30a10 knockout mice exhibited a profound deficit in thyroid iodine levels that occurred contemporaneously with increases in thyroid Mn levels and preceded the onset of overt hypothyroidism. Wild-type Mn-exposed mice also exhibited increased thyroid Mn levels, an inverse correlation between thyroid Mn and iodine levels, and subclinical hypothyroidism. In contrast, thyroid iodine levels were unaltered in newly generated Slc30a10 knockout rats despite an increase in thyroid Mn levels, and the knockout rats were euthyroid. Thus, Mn-induced thyroid dysfunction in genetic or Mn exposure-induced mouse models occurs due to a reduction in thyroid iodine subsequent to an increase in thyroid Mn levels. Moreover, rat and mouse thyroids have differential sensitivities to Mn, which may impact the manifestations of Mn-induced disease in these routinely used animal models.

Study on harmless treatment of electrolytic manganese residue by low temperature thermochemical method.

The Electrolytic Manganese Residue (EMR) is a by-product of the electrolytic manganese metal (EMM) industry, containing high concentrations of potential pollutants such as NH4+-N and soluble Mn2+. These components pose a serious threat to the ecological environment. To explore accurate, efficient, and harmless treatment methods for EMR, this study proposes a low-temperature thermochemical approach. The orthogonal experiment design investigates the effects of reaction temperature, reaction time, quicklime (CaO), sodium carbonate (Na2CO3), sodium phosphate (Na3PO4) (Reviewer #3), and water consumption on manganese solidified and ammonia removal from EMR. The results indicate that optimal conditions are a reaction temperature of 60 ℃ (Reviewer #3) and a reaction time of 10 min. CaO precipitates Mn2+ as manganese hydroxide (Mn(OH)2) (Reviewer #3), achieving effective manganese solidified and ammonia removal. The addition of Na2CO3 causes Mn2+ to form manganesecarbonate (MnCO3) (Reviewer #3)precipitate, while Na3PO4 makes Mn2+ form Manganese phosphate trihydrate (Mn3(PO4)2·3H2O) (Reviewer #3). Increased water consumption enhances the interaction adequacy between ions. Under optimal conditions (CaO 10%, Na2CO3 1%, Na3PO4 0.5%, and 80% water consumption), the removal rate of ammonium ions reaches 98.5%, and the solidification rate of soluble Mn2+ is 99.9%. The order of influence on ammonium ion removal is CaO > water consumption > Na3PO4 > Na2CO3. Therefore, this study provides a new method for low-cost process disposal and efficient harmless treatment of EMR (Reviewer #3).

The mechanism of arbuscular mycorrhizal fungi-alleviated manganese toxicity in plants: A review.

The development of the mining industry and the overuse of inorganic fertilizers have led to an excess of manganese (Mn) in the soil, thereby, contaminating the soil environment and people's health. On heavy metal-contaminated soils, the combined arbuscular mycorrhizal fungi (AMF)-phytoremediation technique becomes a hotspot because of its environmentally friendly, in situ remediation. AMF inoculation often leads to a decrease in host Mn acquisition, which provides a basis for its application in phytoremediation of contaminated soils. Moreover, the utilization value of native AMF is greater than that of exotic AMF, because native AMF can adapt better to Mn-contaminated soils. In addition to the fact that AMF enhance plant Mn tolerance responses such as regionalization, organic matter chelation, limiting uptake and efflux, and so on, AMF also develop plant-independent fungal pathways such as direct biosorption of Mn by mycorrhizal hyphae, fungal Mn transporter genes, and sequestration of Mn by mycorrhizal hyphae, glomalin, and arbuscule-containing root cortical cells, which together mitigate excessive Mn toxicity to plants. Clarifying AMF-plant interactions under Mn stress will provide support for utilizing AMF as a phytoremediation in Mn-contaminated soils. The review reveals in detail how AMF develop its own mechanisms for responding to excess Mn and how AMF enhance plant Mn tolerance, accompanied by perspectives for future research.

Formation of Biogenic Manganese Oxide Nodules on Hyphae of a New Fungal Isolate of Periconia That Immobilizes Aqueous Copper.

Mn(II)-oxidizing microorganisms are considered to play significant roles in the natural geochemical cycles of Mn and other heavy metals because the insoluble biogenic Mn oxides (BMOs) that are produced by these microorganisms adsorb other dissolved heavy metals and immobilize them as precipitates. In the present study, a new Mn(II)-oxidizing fungal strain belonging to the ascomycete genus Periconia, a well-studied plant-associating fungal genus with Mn(II)-oxidizing activity that has not yet been exami-ned in detail, was isolated from natural groundwater outflow sediment. This isolate, named strain TS-2, was confirmed to oxidize dissolved Mn(II) and produce insoluble BMOs that formed characteristic, separately-located nodules on their hyphae while leaving major areas of the hyphae free from encrustation. These BMO nodules also adsorbed and immobilized dissolved Cu(II), a model analyte of heavy metals, as evidenced by elemental mapping ana-lyses of fungal hyphae-BMO assemblages using a scanning electron microscope with energy-dispersive X-ray spectroscopy (SEM-EDX). Analyses of functional genes within the whole genome of strain TS-2 further revealed the presence of multiple genes predicted to encode laccases/multicopper oxidases that were potentially responsible for Mn(II) oxidation by this strain. The formation of BMO nodules may have functioned to prevent the complete encrustation of fungal hyphae, thereby enabling the control of heavy metal concentrations in their local microenvironments while maintaining hyphal functionality. The present results will expand our knowledge of the physiological and morphological traits of Mn(II)-oxidizing Periconia, which may affect the natural cycle of heavy metals through their immobilization.

Chemical fractionation and mobility of Cd, Mn, Ni, and Pb in farmland soils near a ceramics company.

Soil contamination due to industrial activity in ceramics production is of concern because of the risk of heavy metal pollution. Successive extraction was used to measure and identify the concentrations of Cd, Mn, Ni, and Pb in farming soils near a ceramics company in Nigeria. Furthermore, soil pH and particle size analyses were determined. The concentration of Pb was the highest, followed by that of Ni, Mn, and Cd (lowest), and the mean level of Cd exceeded the regulatory allowed limit of 1.4 mg kg-1. The order of the metals' mobility factors was as follows: Cd > Mn > Ni, Pb. While the Fe-Mn oxide phase had 37% (Mn) and 20 to 83% (Ni), the residual fraction had approximately 30% (Cd) and 19 to 50% (Pb). Soil pollution evaluation was performed using enrichment factor (EF), contamination factor (CF), pollution load index (PLI), and geoaccumulation index (Igeo). Values of EF indicated significant enrichment for all metals, as the EF mean values for Cd, Ni, and Pb in soil were > 1.5. Total EF is of the order Cd > Pb > Ni > Mn. CF results revealed moderate to very high contamination (CF < 1: 3 ≤ CF ≥ 6). Similarly, the PLI indicated moderately to severely polluted soil. The order is 100 m > 200 m > 300 m > 400 m. The Igeo ranged from 1.46 to 2.76 (Cd), 0.07 to 1.62 (Ni), and 0.05 to 2.81 (Pb). The PCA, CA, and EF analyses suggest that the metals are a consequence of anthropogenic activities.

Manganese porphyrin-based treatment improves fetal-placental development and protects against oxidative damage and NLRP3 inflammasome activation in a rat maternal hypothyroidism model.

Oxidative stress (OS) and endoplasmic reticulum stress (ERS) are at the genesis of placental disorders observed in preeclampsia, intrauterine growth restriction, and maternal hypothyroidism. In this regard, cationic manganese porphyrins (MnPs) comprise potent redox-active therapeutics of high antioxidant and anti-inflammatory potential, which have not been evaluated in metabolic gestational diseases yet. This study evaluated the therapeutic potential of two MnPs, [MnTE-2-PyP]5+ (MnP I) and [MnT(5-Br-3-E-Py)P]5+ (MnP II), in the fetal-placental dysfunction of hypothyroid rats. Hypothyroidism was induced by administration of 6-Propyl-2-thiouracil (PTU) and treatment with MnPs I and II 0.1 mg/kg/day started on the 8th day of gestation (DG). The fetal and placental development, and protein and/or mRNA expression of antioxidant mediators (SOD1, CAT, GPx1), hypoxia (HIF1α), oxidative damage (8-OHdG, MDA), ERS (GRP78 and CHOP), immunological (TNFα, IL-6, IL-10, IL-1ß, IL-18, NLRP3, Caspase1, Gasdermin D) and angiogenic (VEGF) were evaluated in the placenta and decidua on the 18th DG using immunohistochemistry and qPCR. ROS and peroxynitrite (PRX) were quantified by fluorometric assay, while enzyme activities of SOD, GST, and catalase were evaluated by colorimetric assay. MnPs I and II increased fetal body mass in hypothyroid rats, and MnP I increased fetal organ mass. MnPs restored the junctional zone morphology in hypothyroid rats and increased placental vascularization. MnPs blocked the increase of OS and ERS mediators caused by hypothyroidism, showing similar levels of expression of HIFα, 8-OHdG, MDA, Gpx1, GRP78, and Chop to the control. Moreover, MnPs I and/or II increased the protein expression of SOD1, Cat, and GPx1 and restored the expression of IL10, Nlrp3, and Caspase1 in the decidua and/or placenta. However, MnPs did not restore the low placental enzyme activity of SOD, CAT, and GST caused by hypothyroidism, while increased the decidual and placental protein expression of TNFα. The results show that treatment with MnPs improves the fetal-placental development and the placental inflammatory state of hypothyroid rats and protects against oxidative stress and reticular stress caused by hypothyroidism at the maternal-fetal interface.

Comparing Mn-based oxides filters started by KMnO4 versus K2FeO4 for ammonium and manganese removal: Formation mechanism of active species.

A pilot-scale filtration system was adopted to prepare filter media with catalytic activity to remove manganese (Mn2+) and ammonium (NH4+-N). Three different combinations of oxidants (KMnO4 and K2FeO4) and reductants (MnSO4 and FeCl2) were used during the start-up period. Filter R3 started up by KMnO4 and FeCl2 (Mn7+→MnOx) exhibited excellent catalytic property, and the NH4+-N and Mn2+ removal efficiency reached over 80% on the 10th and 35th days, respectively. Filter R1 started up by K2FeO4 and MnSO4 (MnOx←Mn2+) exhibited the worst catalytic property. Filter R2 started up by KMnO4 and MnSO4 (Mn7+→MnOx←Mn2+) were in between. According to Zeta potential results, the Mn-based oxides (MnOx) formed by Mn7+→MnOx performed the highest pHIEP and pHPZC. The higher the pHIEP and pHPZC, the more unfavorable the cation adsorption. However, it was inconsistent with its excellent Mn2+ and NH4+-N removal abilities, implying that catalytic oxidation played a key role. Combined with XRD and XPS analysis, the results showed that the MnOx produced by the reduction of KMnO4 showed early formation of buserite crystals, high degree of amorphous, high content of Mn3+ and lattice oxygen with the higher activity to form defects. The above results showed that MnOx produced by the reduction of KMnO4 was more conducive to the formation of active species for catalytic oxidation of NH4+-N and Mn2+ removal. This study provides new insights on the formation mechanisms of the active MnOx that could catalytic oxidation of NH4+-N and Mn2+.

Effect and mechanism of Mn2+ on urease activity during anaerobic biological treatment of landfill leachate.

As a crucial hydrolytic enzyme, urease plays a vital role in anaerobic biological treatment. It is well-known that manganese ions are abundant in landfill leachate, but their concentration fluctuates significantly. However, few studies have investigated the effect and mechanism of different concentrations of Mn2+ on urease activity during anaerobic biological treatment of landfill leachate. This paper aimed to investigate the effects and mechanisms of different concentrations of Mn2+ on urease activity. The results showed that an appropriate amount of Mn2+ could significantly enhance urease activity, while a high concentration of Mn2+ could inhibit it. Insight into the mechanisms behind this phenomenon, various methods such as Zeta potential, particle size, ultraviolet spectroscopy, fluorescence spectroscopy, Fourier transform infrared spectroscopy, and statistical analysis were employed in our study. Research suggested that, on one hand, Mn2+ may form hydrogen bonds with the side chain amino or carboxyl groups of urease amino acid residues, affecting the structure of urease through hydrogen bonding. Additionally, Mn2+ also binds to urease through hydrophobic interactions. On the other hand, the C-OH and C-N functional groups in urease have a strong affinity for Mn2+, and changes in these functional groups can greatly enhance the activity of urease. Furthermore, under the action of high concentrations of Mn2+, while the structure of urease becomes more stable, there is also a steric hindrance phenomenon that affects the substrate from entering the catalytic center. Therefore, studying the mechanism of Mn2+ affecting urease activity has significant biological significance and provides a new perspective for exploring the impact of metals on anaerobic bioprocessing of landfill leachate.

Comparative investigation of tellurium-doped transition metal nanoparticles (Zn, Sn, Mn): Unveiling their superior photocatalytic and antibacterial activity.

In this study, tellurium-doped and undoped metal oxide nanoparticles (NPs) (ZnO, Mn3O4, SnO2) are compared, and a practical method for their synthesis is presented. Nanocomposites were created using the coprecipitation process, and comparisons between the three material categories under study were made using a range of characterization methods. The produced materials were subjected to structural, morphological, elemental composition, and functional group analyses using XRD, FESEM in combination with EDS, and FTIR. The optical characteristics in terms of cutoff wavelength were evaluated using UV-visible spectroscopy. Catalyzing the breakdown of methylene blue (MB) dye, the isolated nanocomposites demonstrated very consistent behavior when utilized as catalysts. Regarding both doped and undoped ZnO NPs, the maximum percentage of degradation was found to be 98% when exposed to solar Escherichia coli and Staphylococcus aureus, which stand for gram-positive and gram-negative bacteria, respectively, and were chosen as model strains for both groups using the disk diffusion technique in the context of in vitro antibacterial testing. Doped and undoped ZnO NPs exhibited greater antibacterial efficacy, with significant inhibition zones measuring 31.5 and 37.8 mm, compared with other metal oxide NPs.

Specific of accumulation of manganese in organs and tissues of Hereford cattle.

The elemental status of cattle is one of the important factors, which determine its growth, fertility, fetal development, meat and dairy production, etc. Therefore, the study of content of different elements in cattle organs and tissues and its correlation with cattle characteristics and diet is urgent task. It is also important to develop intravital and low-invasive methods to analyze element content in cattle to regulate its diet during lifetime. In the present work, we have studied the content and distribution of manganese in Hereford cattle from an ecologically clean zone of Western Siberia (Russia). 252 samples were taken from 31 bulls aged 15-18 months. They were collected from various livestock farms in the region and analyzed using atomic absorption spectrophotometry (organs and muscle tissue) and inductively coupled plasma atomic emission spectrometry (hair). The median values of manganese concentration obtained in natural moisture for hair, heart, kidneys, liver, lungs, muscles, spleen, testes, and brain were 25, 0.37, 1.0, 2.6, 0.4, 0.2, 0.4, 0.5, and 0.5 ppm. Accordingly, the concentration of manganese differs significantly in the organs and tissues of animals (H = 188.6, df = 8, p <0.0001). Statistically significant associations of manganese were revealed in pairs: liver-testis, hair-testis, spleen-testis, and heart-brain. The classification of organs and tissues of animals according to the level of content and variability of manganese is carried out. The concentration of manganese in the body is not uniform, most of all it is deposited in the hair and excretory organs of the liver and kidneys. In other organs and muscle tissues, the distribution of manganese is more even and is in the range of 0.2-0.5 ppm. The resulting ranges can be used as a guideline for Hereford cattle bred in Western Siberia.