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1.
Nat Commun ; 12(1): 804, 2021 02 05.
Artigo em Inglês | MEDLINE | ID: mdl-33547322

RESUMO

Evolution of xeno nucleic acid (XNA) world essentially requires template-directed synthesis of XNA polymers. In this study, we demonstrate template-directed synthesis of an acyclic XNA, acyclic L-threoninol nucleic acid (L-aTNA), via chemical ligation mediated by N-cyanoimidazole. The ligation of an L-aTNA fragment on an L-aTNA template is significantly faster and occurs in considerably higher yield than DNA ligation. Both L-aTNA ligation on a DNA template and DNA ligation on an L-aTNA template are also observed. High efficiency ligation of trimer L-aTNA fragments to a template-bound primer is achieved. Furthermore, a pseudo primer extension reaction is demonstrated using a pool of random L-aTNA trimers as substrates. To the best of our knowledge, this is the first example of polymerase-like primer extension of XNA with all four nucleobases, generating phosphodiester bonding without any special modification. This technique paves the way for a genetic system of the L-aTNA world.


Assuntos
Amino Álcoois/metabolismo , Butileno Glicóis/metabolismo , DNA/genética , Imidazóis/química , Ácidos Nucleicos/síntese química , RNA/genética , Amino Álcoois/química , Pareamento de Bases , Biocatálise , Butileno Glicóis/química , Cátions Bivalentes , DNA/química , DNA/metabolismo , Primers do DNA/química , Primers do DNA/metabolismo , Manganês/química , Manganês/metabolismo , Conformação de Ácido Nucleico , RNA/química , RNA/metabolismo , Soluções
2.
Analyst ; 146(2): 463-470, 2021 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-33491016

RESUMO

Selective detection of adenosine monophosphate (AMP) and adenosine diphosphate (ADP) which are less charged molecules than adenosine triphosphate (ATP) or pyrophosphate (PPi) in aqueous solution has been considered challenging because AMP and ADP have relatively low binding affinity for phosphate receptors. In this study, colorimetric discrimination of nucleoside phosphates was achieved based on catalytic signal amplification through the activation of artificial peroxidase. This method showed high selectivity for AMP and ADP over ATP and PPi, unlike previous phosphate sensors that use Zn2+-dipicolylamine-based receptors. High selectivity of the suggested method allowed discrimination of AMP in aqueous solution by the naked eye, and the detection limit was estimated to be 0.5 µM. Mechanism analysis revealed AMP acted as activators in the peroxidation cycle of the Mn2(bpmp)/ABTS/H2O2 system despite having relatively low binding affinity. Additionally, high selectivity and quantitative signal amplification allowed for the development of colorimetric phosphodiesterase and a small molecule kinase assay method. The newly proposed method offers direct, real-time, and quantitative analysis of enzyme activities and inhibition, and is expected to be further applied to high-throughput screening of inhibitors.


Assuntos
Nucleotídeos de Adenina/análise , Colorimetria/métodos , Benzotiazóis/química , Materiais Biomiméticos/química , Catálise , Complexos de Coordenação/química , Ensaios Enzimáticos , Peróxido de Hidrogênio/química , Cinética , Manganês/química , Ácidos Sulfônicos/química
3.
Ecotoxicol Environ Saf ; 211: 111904, 2021 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-33453639

RESUMO

This original research was performed to assess the possible effects of solid biochar (25 g biochar kg-1 soil) and biochar-based nanocomposites (BNCs) of magnesium oxide (25 g BNC-MgO kg-1 soil), manganese oxide (25 g BNC-MnO biochar kg-1 soil) and combined use of these nanocomposites (12.5 g BNC-MgO + 12.5 g BNC-MnO kg-1 soil) on soil properties and salinity (non-saline, 6 and 12 dSm-1) tolerance of safflower plants (Carthamus tinctorius L.). Application of biochar, particularly BNCs increased the pH and cation exchange capacity of soil, and the contents of water, potassium, calcium, magnesium, manganese, chlorophyll (a & b), nutrients uptake, water use efficiency and plant growth. Sodium adsorption ratio (SAR), exchangeable sodium percentage (ESP) of soil, sodium absorption rate of plants and osmolyte production (soluble carbohydrates and proteins, proline and glycine betaine) under 6 and 12 dSm-1 salinities were decreased by biochar and BNCs treatments. Sodium sorption capacity of BNCs was much higher than the solid biochar, which reflected the superiority of BNCs in decreasing sodium uptake by plants. The combined application of BNC-MgO + BNC-MnO proved to be the preferable treatment for decreasing salt toxicity in safflower. Biochar and BNCs improved root and shoot growth by lowering SAR, ESP, sodium absorption rate of plants and osmotic stress under saline conditions. These results conclude that BNCs can enrich the plant cells with nutrients, increase the nutrients absorption rate and maintain the plant tissue water content at an optimum level to improve plant growth under salt stress.


Assuntos
Carvão Vegetal , Magnésio/química , Manganês/química , Adsorção , Carthamus tinctorius/metabolismo , Clorofila , Íons/metabolismo , Magnésio/metabolismo , Manganês/metabolismo , Nanocompostos , Óxidos/metabolismo , Potássio/metabolismo , Salinidade , Estresse Salino , Tolerância ao Sal , Sódio/metabolismo , Solo/química , Poluentes do Solo/metabolismo
4.
Ecotoxicol Environ Saf ; 211: 111893, 2021 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-33461016

RESUMO

In this study, electric field and ball milling were used to leach Mn2+ from low-grade pyrolusite (LGP). The effects of current density, reaction time, reaction temperature, ball-to-powder weight ratio, and ball milling time on the leaching efficiency of Mn2+ from LGP as well as the leaching mechanism were systematically studied. The results showed that the combined use of electric field and ball milling enhanced the leaching of Mn2+ from LGP. The leaching efficiency of Mn2+ reached 97.79% under the optimum conditions of LGP-to-pyrite mass ratio of 1:0.18, current density of 30 mA/cm2, LGP-to-H2SO4 mass ratio of 1:0.4, liquid-to-solid ratio of 5:1, ball-to-powder weight ratio of 1:1, ball milling time of 2 h, temperature of 80 °C, and leaching duration of 120 min. This value was 25.95% higher than that attained without ball milling and 41.45% higher than that attained when neither ball milling nor electric field was employed. Pyrite was fully oxidized to generate additional SO42- and Fe3+, and was further hydrolyzed to form jarosite (KFe3(SO4)2(OH)6) and hydronium jarosite (Fe3(SO4)2(OH)5·2H2O) via ball milling and electric field application. Moreover, the electric field changed the surface charge distribution of the mineral particles and promoted collisions between them as well as the collapse of the crystal lattice, further improving the leaching efficiency of Mn2+ from LGP. This study provided a new method for leaching Mn from LGP.


Assuntos
Manganês/química , Modelos Químicos , Compostos Férricos , Ferro , Compostos de Manganês , Óxidos , Sulfatos , Sulfetos
5.
Food Chem ; 342: 128299, 2021 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-33508901

RESUMO

Manganese-doped zinc sulfide quantum dots (Mn-ZnS QDs) are promising candidates for multi-channel sensing analysis due to their multi-dimensional optical properties. In this study, we integrated amino-silane and ionic liquid co-modified Mn-ZnS QDs and covalent organic frameworks (COFs) into optosensing nanoparticles to provide triple-dimensional optical response signals and combined them with chemometrics for the analysis of multiple pesticide residues. Through the exploration and optimization of a series of conditions, fluorescence, room temperature phosphorescence, and ultraviolet-visible combined with chemometrics were used for the discrimination and recognition of multiple pesticide residues in fruits and vegetables. The ionic liquid of 1-vinyl-3-ethylimidazolium tetrafluoroborate was used to modify Mn-ZnS QDs to improve the optical response and enrichment of pesticide adsorption sites, which were also synergistically enhanced by the COF support. This is a potential method to discriminate pesticides efficiently and enables fast and reliable analysis of pesticides in the agricultural and food industries.


Assuntos
Líquidos Iônicos/química , Estruturas Metalorgânicas/química , Resíduos de Praguicidas/análise , Pontos Quânticos/química , Espectrometria de Fluorescência , Espectrofotometria Ultravioleta , Cucumis sativus/química , Cucumis sativus/metabolismo , Análise Discriminante , Concentração de Íons de Hidrogênio , Malus/química , Malus/metabolismo , Manganês/química , Análise de Componente Principal , Sulfetos/química , Compostos de Zinco/química
6.
Chemosphere ; 262: 128082, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33182100

RESUMO

As important natural oxidants and adsorbents, manganese (Mn) oxide minerals affect the speciation, bioavailability and fate of pollutants and nutrient elements. It was found that birnessite-type Mn(IV) oxide minerals can be formed in the presence of NO3- and solar irradiation. However, the photochemical formation and transformation processes from Mn2+ to Mn(IV) oxide minerals remain unclear. In this work, the Mn(IV) oxide minerals were confirmed to be photochemically formed mainly due to the disproportionation of Mn(III) intermediates generated from the oxidation of Mn2+ in the presence of NO3- under UV light irradiation. The oxidation rate of Mn2+ to Mn(IV) oxide minerals decreased with increasing initial Mn2+ concentration due to the lower disproportionation rate. The increase in NO3- concentration, pH and temperature promoted Mn2+ photochemical oxidation. The photochemical formation rate of Mn(IV) oxide minerals increased with increasing ligand concentrations at low ligand concentrations. Ligands affected the formation of Mn(IV) oxide minerals by promoting the formation and reducing the reactivity of Mn(III) intermediates. Overall, this work reveals the important role of Mn(III) intermediates in the formation of natural Mn oxide minerals.


Assuntos
Compostos de Manganês/química , Manganês/química , Minerais/química , Óxidos/química , Luz Solar , Manganês/efeitos da radiação , Compostos de Manganês/efeitos da radiação , Minerais/efeitos da radiação , Modelos Teóricos , Oxirredução , Óxidos/efeitos da radiação , Processos Fotoquímicos , Temperatura
7.
Chemosphere ; 263: 127914, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32822940

RESUMO

The MSWI fly ash (FA) is classified as hazardous waste and electrolytic manganese residue (EMR) as the harmful industrial waste. FA, water-washed FA (WFA), EMR and coal fly ash (CFA) were co-recycled to form lightweight MFCE ceramisites. The effects of FA, WFA and mixed MSWI fly ash on ceramisites were discussed. The approach to mixing FA and WFA increased the recycling amount of MSWI fly ash. The optimal mixture of 34.5% EMR, 24.1% CFA, 20.7% FA and 20.7% WFA sintered at 1160 °C for 12 min with a procedural heating rate (10 °C/min) and belonged to Class 800 artificial lightweight aggregate (GB/T 17431.1-2010); the quantity of MSWI fly ash in ceramisite was as high as 41.4%. Volatilization rates of Cd, Pb, Cu, Zn, Mn and Cr for ceramisite were higher 75.0, 24.2, 62.7, 133, 343 and 764% than FA respectively, attributed to the co-existence of chlorides and sulfates. The remained Zn, Cu, Pb, Mn and Cr were exchanged with Mg2+/Ca2+/Al3+ of diopside and wollastonite to form residual fractions. Our findings provided a feasibility method of co-recycling MSWI fly ash and electrolytic manganese residue to produce green lightweight aggregates.


Assuntos
Cinza de Carvão/química , Incineração , Manganês/química , Carbono , Carvão Mineral , Eletrólise , Íons , Metais Pesados/análise , Material Particulado , Eliminação de Resíduos , Resíduos Sólidos , Volatilização
8.
Nucleic Acids Res ; 49(2): 1023-1032, 2021 01 25.
Artigo em Inglês | MEDLINE | ID: mdl-33367848

RESUMO

Pseudomonas putida MPE exemplifies a novel clade of manganese-dependent single-strand DNA endonuclease within the binuclear metallophosphoesterase superfamily. MPE is encoded within a widely conserved DNA repair operon. Via structure-guided mutagenesis, we identify His113 and His81 as essential for DNA nuclease activity, albeit inessential for hydrolysis of bis-p-nitrophenylphosphate. We propose that His113 contacts the scissile phosphodiester and serves as a general acid catalyst to expel the OH leaving group of the product strand. We find that MPE cleaves the 3' and 5' single-strands of tailed duplex DNAs and that MPE can sense and incise duplexes at sites of short mismatch bulges and opposite a nick. We show that MPE is an ambidextrous phosphodiesterase capable of hydrolyzing the ssDNA backbone in either orientation to generate a mixture of 3'-OH and 3'-PO4 cleavage products. The directionality of phosphodiester hydrolysis is dictated by the orientation of the water nucleophile vis-à-vis the OH leaving group, which must be near apical for the reaction to proceed. We propose that the MPE active site and metal-bound water nucleophile are invariant and the enzyme can bind the ssDNA productively in opposite orientations.


Assuntos
Proteínas de Bactérias/metabolismo , Enzimas Reparadoras do DNA/metabolismo , DNA de Cadeia Simples/metabolismo , Desoxirribonuclease I/metabolismo , Pseudomonas putida/enzimologia , Proteínas de Bactérias/química , Pareamento de Bases , Domínio Catalítico , Reparo de Erro de Pareamento de DNA , Reparo do DNA , Enzimas Reparadoras do DNA/química , Desoxirribonuclease I/química , Histidina/química , Hidrólise , Manganês/química , Modelos Moleculares , Nitrofenóis/metabolismo , Fosfatos/química , Ligação Proteica , Conformação Proteica , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Relação Estrutura-Atividade , Água
9.
Nat Commun ; 11(1): 5036, 2020 10 07.
Artigo em Inglês | MEDLINE | ID: mdl-33028818

RESUMO

Alkyl carboxylic acids as well as primary amines are ubiquitous in all facets of biological science, pharmaceutical science, chemical science and materials science. By chemical conversion to redox-active esters (RAE) and Katritzky's N-alkylpyridinium salts, respectively, alkyl carboxylic acids and primary amines serve as ideal starting materials to forge new connections. In this work, a Mn-mediated reductive decarboxylative/deaminative functionalization of activated aliphatic acids and primary amines is disclosed. A series of C-X (X = S, Se, Te, H, P) and C-C bonds are efficiently constructed under simple and mild reaction conditions. The protocol is applicable to the late-stage modification of some structurally complex natural products or drugs. Preliminary mechanistic studies suggest the involvement of radicals in the reaction pathway.


Assuntos
Aminas/química , Técnicas de Química Sintética/métodos , Ácidos Graxos/química , Manganês/química , Catálise , Estudos de Viabilidade , Oxirredução
10.
Ecotoxicol Environ Saf ; 206: 111341, 2020 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-32979720

RESUMO

In this study, a new electrochemical method was used to simultaneously efficient removal of Mn2+ and NH4+-N in wastewater with Cu plate as cathode. The effects of various reaction parameters on the concentrations of Mn2+, NH4+-N and by-products (NO3--N and NO2--N, free chlorine and residual chlorine), as well as the removal mechanism were investigated. The results showed that the removal efficiencies of Mn2+ and NH4+-N were 99.1% and 92.9%, and the concentrations of NO3--N, NO2--N, free chlorine and residue chlorine were 0.73 mg/L, 0.15 mg/L, 0.13 mg/L and 0.63 mg/L reacting for 3 h at room temperature, respectively, when the current density was 10 mA/cm2, the mass ratio of ClO- and Cl- was 1:1, the initial pH was 9. The concentrations of Mn2+, NH4+-N and by-products in wastewater met the integrated wastewater discharge standard (GB8978-1996). In addition, spherical manganese oxide was deposited on the anode plate, and spherical manganese oxide collapsed over electrolysis time. Manganese was mainly removed in the form of MnO, Mn(OH)2 and MnO2. NH4+-N was mainly oxidized to N2. Economic evalution revealed that the treatment cost was 2.93 $/m3.


Assuntos
Amônia/química , Compostos de Manganês/química , Óxidos/química , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/química , Cloro , Cobre/química , Técnicas Eletroquímicas , Eletrodos , Eletrólise , Manganês/química , Nitrogênio/análise , Oxirredução , Águas Residuárias/química
11.
Ecotoxicol Environ Saf ; 205: 111317, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32950807

RESUMO

Electrolytic manganese residue (EMR) is a solid waste remained in filters after using sulfuric acid to leaching manganese carbonate ore. EMR contains high concentration of soluble manganese (Mn2+) and ammonia nitrogen (NH4+-N), which seriously pollutes the environment. In this study, a low cost of phosphate based binder for Mn2+ and NH4+-N stabilization in EMR by low grade-MgO (LG-MgO) and superphosphate was studied. The effects of different types of stabilizing agent on the concentrations of NH4+-N and Mn2+, the pH of the EMR leaching solution, stabilizing mechanisms of NH4+-N and Mn2+, leaching test and economic analysis were investigated. The results shown that the pH of the EMR leaching solution was 8.07, and the concentration of Mn2+ was 1.58 mg/L, both of which met the integrated wastewater discharge standard (GB8978-1996), as well as the concentration of NH4+-N decreased from 523.46 mg/L to 32 mg/L, when 4.5 wt.% LG-MgO and 8 wt.% superphosphate dosage were simultaneously used for the stabilization of EMR for 50 d Mn2+ and NH4+-N were mainly stabilized by Mn3(PO4)2·2H2O, MnOOH, Mn3O4, Mn(H2PO4)2·2H2O and NH4MgPO4·6H2O. Economic evaluation revealed that the treatment cost of EMR was $ 11.89/t. This study provides a low-cost materials for NH4+-N and Mn2+ stabilization in EMR.


Assuntos
Amônia/química , Manganês/química , Amônia/análise , Carbonatos , Eletrólise , Eletrólitos/química , Poluentes Ambientais/análise , Manganês/análise , Nitrogênio/análise , Fosfatos/química , Resíduos Sólidos/análise , Águas Residuárias/química
12.
J Vis Exp ; (160)2020 06 18.
Artigo em Inglês | MEDLINE | ID: mdl-32628168

RESUMO

For biomedical applications, metal oxide nanoparticles such as iron oxide and manganese oxide (MnO), have been used as biosensors and contrast agents in magnetic resonance imaging (MRI). While iron oxide nanoparticles provide constant negative contrast on MRI over typical experimental timeframes, MnO generates switchable positive contrast on MRI through dissolution of MnO to Mn2+ at low pH within cell endosomes to 'turn ON' MRI contrast. This protocol describes a one-pot synthesis of MnO nanoparticles formed by thermal decomposition of manganese(II) acetylacetonate in oleylamine and dibenzyl ether. Although running the synthesis of MnO nanoparticles is simple, the initial experimental setup can be difficult to reproduce if detailed instructions are not provided. Thus, the glassware and tubing assembly is first thoroughly described to allow other investigators to easily reproduce the setup. The synthesis method incorporates a temperature controller to achieve automated and precise manipulation of the desired temperature profile, which will impact resulting nanoparticle size and chemistry. The thermal decomposition protocol can be readily adapted to generate other metal oxide nanoparticles (e.g., iron oxide) and to include alternative organic solvents and stabilizers (e.g., oleic acid). In addition, the ratio of organic solvent to stabilizer can be changed to further impact nanoparticle properties, which is shown herein. Synthesized MnO nanoparticles are characterized for morphology, size, bulk composition, and surface composition through transmission electron microscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy, respectively. The MnO nanoparticles synthesized by this method will be hydrophobic and must be further manipulated through ligand exchange, polymeric encapsulation, or lipid capping to incorporate hydrophilic groups for interaction with biological fluids and tissues.


Assuntos
Hidroxibutiratos/química , Compostos de Manganês/química , Manganês/química , Nanopartículas Metálicas/química , Óxidos/química , Pentanonas/química , Temperatura , Vidro/química , Interações Hidrofóbicas e Hidrofílicas , Nanopartículas Metálicas/ultraestrutura , Nitrogênio/química , Tamanho da Partícula , Espectroscopia de Infravermelho com Transformada de Fourier , Propriedades de Superfície , Água/química , Difração de Raios X
13.
Nature ; 583(7816): 453-458, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32669693

RESUMO

Manganese is one of the most abundant elements on Earth. The oxidation of manganese has long been theorized1-yet has not been demonstrated2-4-to fuel the growth of chemolithoautotrophic microorganisms. Here we refine an enrichment culture that exhibits exponential growth dependent on Mn(II) oxidation to a co-culture of two microbial species. Oxidation required viable bacteria at permissive temperatures, which resulted in the generation of small nodules of manganese oxide with which the cells associated. The majority member of the culture-which we designate 'Candidatus Manganitrophus noduliformans'-is affiliated to the phylum Nitrospirae (also known as Nitrospirota), but is distantly related to known species of Nitrospira and Leptospirillum. We isolated the minority member, a betaproteobacterium that does not oxidize Mn(II) alone, and designate it Ramlibacter lithotrophicus. Stable-isotope probing revealed 13CO2 fixation into cellular biomass that was dependent upon Mn(II) oxidation. Transcriptomic analysis revealed candidate pathways for coupling extracellular manganese oxidation to aerobic energy conservation and autotrophic CO2 fixation. These findings expand the known diversity of inorganic metabolisms that support life, and complete a biogeochemical energy cycle for manganese5,6 that may interface with other major global elemental cycles.


Assuntos
Bactérias/metabolismo , Crescimento Quimioautotrófico , Manganês/metabolismo , Bactérias/classificação , Bactérias/genética , Bactérias/crescimento & desenvolvimento , Ciclo do Carbono , Dióxido de Carbono/metabolismo , Técnicas de Cocultura , Perfilação da Expressão Gênica , Isótopos , Manganês/química , Compostos de Manganês/química , Compostos de Manganês/metabolismo , Oxirredução , Óxidos/química , Óxidos/metabolismo , Filogenia
14.
PLoS One ; 15(6): e0234136, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32520947

RESUMO

Groundwater treatment sludge is a Fe/Mn-bearing waste that is mass produced in groundwater treatment plant. In this study, sludge was converted to a magnetic adsorbent (MA) by adding ascorbate. The sludge was weakly magnetised in the amorphous form with Fe and Mn contents of 28.8% and 8.1%, respectively. After hydrothermal treatment, Fe/Mn oxides in the sludge was recrystallised to siderite and rhodochrosite, with jacobsite as the intermediate in the presence of ascorbate. With an increment in ascorbate dosage, the obtained magnetic adsorbent had a significant increase in chromate adsorption but a decrease in magnetisation. When the Mascorbate/MFe molar ratio was 10, the produced MA-10 was a dumbbell-shaped nanorod with a length of 2-5 µm and a diameter of 0.5-1 µm. This MA-10 showed 183.2 mg/g of chromate adsorption capacity and 2.81 emu/g of magnetisation. The mechanism of chromate adsorption was surface coprecipitation of the generated Cr3+ and Fe3+/Mn4+ from redox reaction between chromate and siderite/rhodochrosite on MA-10, separately. This study demonstrated an efficient recycling route of waste sludge from groundwater treatment to produce MA for treating chromate-bearing wastewater.


Assuntos
Cromatos/química , Magnetismo , Nanotubos/química , Esgotos/química , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/química , Adsorção , Carbonatos/química , Compostos Férricos/química , Ferro/química , Cinética , Manganês/química , Oxirredução , Óxidos/química
15.
Nat Commun ; 11(1): 2738, 2020 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-32483131

RESUMO

Almost half of all enzymes utilize a metal cofactor. However, the features that dictate the metal utilized by metalloenzymes are poorly understood, limiting our ability to manipulate these enzymes for industrial and health-associated applications. The ubiquitous iron/manganese superoxide dismutase (SOD) family exemplifies this deficit, as the specific metal used by any family member cannot be predicted. Biochemical, structural and paramagnetic analysis of two evolutionarily related SODs with different metal specificity produced by the pathogenic bacterium Staphylococcus aureus identifies two positions that control metal specificity. These residues make no direct contacts with the metal-coordinating ligands but control the metal's redox properties, demonstrating that subtle architectural changes can dramatically alter metal utilization. Introducing these mutations into S. aureus alters the ability of the bacterium to resist superoxide stress when metal starved by the host, revealing that small changes in metal-dependent activity can drive the evolution of metalloenzymes with new cofactor specificity.


Assuntos
Proteínas de Bactérias/metabolismo , Ferro/metabolismo , Manganês/metabolismo , Metaloproteínas/metabolismo , Staphylococcus aureus/enzimologia , Superóxido Dismutase/metabolismo , Sequência de Aminoácidos , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Domínio Catalítico , Evolução Molecular , Ferro/química , Isoenzimas/classificação , Isoenzimas/genética , Isoenzimas/metabolismo , Manganês/química , Metaloproteínas/química , Metaloproteínas/genética , Mutação , Oxirredução , Filogenia , Homologia de Sequência de Aminoácidos , Staphylococcus aureus/genética , Superóxido Dismutase/química , Superóxido Dismutase/genética , Superóxidos/metabolismo
16.
Chemosphere ; 259: 127424, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32599383

RESUMO

Efficiency of Mn passive treatment from mine drainage (MD) is limited, in the presence of Fe, because of the wide stability field of dissolved Mn(II) species. Physicochemical and mineralogical characterization, as well as static leaching tests at pH 7 (CTEU-9) of four samples were performed to assess Mn immobilization processes from MD and post-treatment stability of residues. Samples consisted of half-calcined dolomite, from three column reactors that treated Mn in MD. The first residue originated from real acid mine drainage treatment (R-AMD; pH 2.4; 623 mg/L Fe; 22 mg/L Mn), the second from real contaminated neutral drainage (R-CND; pH 6.7; 0.6 mg/L Mn) and the third from synthetic CND (S-CND; pH 6.8; 47 mg/L Mn). A sample of calcite (CAL) was also collected in a field oxic limestone drain that treats AMD (pH 4.1; 10.2 mg/L Fe; 12.4 mg/L Mn) on a closed mine site. Mineralogical analyses showed Mn immobilization in the form of MnOx. In R-AMD residues, Fe and Al concentrations almost doubled relative to half calcined dolomite before MD treatment, while Mn removal was inefficient. In S-CND residues, high concentrations of Mn were immobilized (>6.6 g/kg). The mineralogy of R-AMD residues showed that Fe precipitates coated the dolomite, in the form of Fe-(oxy)hydroxysulfates. Half-calcined dolomite is effective for Mn removal in S-CND, but Fe inhibits Mn treatment in AMD. Metal(loid)s in eluates were below the threshold limits, but the pH of R-CND (11.1) and S-CND (10.5) residues no longer met the discharge criteria (pH 6.0 to 9.5).


Assuntos
Manganês/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Carbonato de Cálcio , Concentração de Íons de Hidrogênio , Magnésio , Manganês/análise , Mineração , Poluentes Químicos da Água/análise
17.
Chemosphere ; 258: 127120, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32544808

RESUMO

Diclofenac (DCF) control measures have become an area of increased interest for environmental researchers due to the high environmental concentration and risk of DCF. Adsorption seems to be promising for DCF removal from the aqueous phase because of its specific superiority in comparison with biodegradation, membrane separation, and advanced oxidation or reduction. In this study, OMS-2 and metal-doped OMS-2 ((Me-OMS-2, with Me = Co, Cu or Ce) were prepared and tested as adsorbents for the removal of DCF. It was evident that the maximum adsorption capacity and rate of Ce-OMS-2 were much higher than those of the other adsorbents, which could be attributed to its large specific surface area and stereoscopic aperture structure. The experimental data are fitted the pseudo-second-order model, the Elovich equation and the Langmuir model well; moreover, the process is an endothermic and spontaneous thermodynamic process, during which the entropy increased, based on the experimental results, indicating that chemisorption was dominant during the DCF adsorption process onto Ce-OMS-2. By the integral of the peak deconvoluted from the XPS spectrum, the ratio of Mn3+/Mn4+ increased from 0.393 to 0.407, revealing that Mn(IV) is rarely reduced into Mn(III) during the DCF adsorption process.


Assuntos
Diclofenaco/química , Diclofenaco/isolamento & purificação , Manganês/química , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Espectroscopia de Ressonância de Spin Eletrônica , Substâncias Húmicas , Concentração de Íons de Hidrogênio , Cinética , Oxirredução , Termodinâmica , Água , Poluentes Químicos da Água/química
18.
Chemosphere ; 254: 126780, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32353809

RESUMO

The presence of As(V) and Mn(VII) in water beyond the permissible concentration allowed by World Health Organization (WHO) standard affects human beings, animals and the environment adversely. Hence, there is need for an efficient material to remove these potentially toxic elements from wastewater prior to discharge into water bodies. This research focused on the application of response surface method (RSM) assisted optimization of Fe-Ni/Activated carbon (AC) catalyst for the synthesis of MWCNTs. Also, the MWCNTs was carboxylated and the adsorption behaviors of both nano-adsorbents in the removal of As(V) and Mn(VII) from industrial wastewater was investigated through experimental and computational techniques. The prepared Fe-Ni/AC, MWCNTs and MWCNTs-OCH2CO2H were characterized using BET, TGA, FTIR, HRSEM, HRTEM, XRD and XPS. The result showed the BET surface area of Fe-Ni/AC, MWCNTs and MWCNTs-OCH2CO2H were obtained as 1100, 1250 and 1172 m2/g, respectively. Due to the enhanced impact of carboxylation, the adsorption capacity of As(V) and Mn(VII) removal increased from 200 to 192 mg/g for MWCNTs to 250 and 298 mg/g for MWCNTs-OCH2CO2H. The isotherm and kinetic models were best fitted by Langmuir and pseudo-second order kinetics, while the thermodynamic investigation found that the adsorption process was endothermic, spontaneous and chemisorptions controlled. The regeneration potential of MWCNTs and MWCNTs-OCH2CO2H after six repeated applications revealed good stability of adsorption efficiency. The study demonstrated optimization importance of Fe-Ni/AC catalyst design for MWCNTs adsorbents and the potentials of utilizing both MWCNTs and MWCNTs-OCH2CO2H in the removal of selected heavy metals from water and soil.


Assuntos
Arsênico/química , Manganês/química , Nanotubos de Carbono/química , Águas Residuárias/química , Poluentes Químicos da Água/análise , Adsorção , Carvão Vegetal , Concentração de Íons de Hidrogênio , Cinética , Metais Pesados , Termodinâmica , Eliminação de Resíduos Líquidos , Água , Purificação da Água/métodos
19.
J Med Chem ; 63(11): 6057-6065, 2020 06 11.
Artigo em Inglês | MEDLINE | ID: mdl-32372648

RESUMO

Toxicity concerns related to Gd(III)-based magnetic resonance imaging (MRI) agents prompted an intensive research toward their replacement by complexes of essential metal ions, like Mn(II). Here, we report a macrocyclic chelate, [Mn(PC2A-BP)], which possesses high thermodynamic stability (log KMnL = 14.86 and pMn=8.35) and kinetic inertness (t1/2pH=7.4 = 286.2 h) as well as as remarkable relaxivity (r1p = 23.5 mM-1 s-1, 0.49 T, 37 °C) in the presence of human serum albumin, allowing a significant MRI signal intensity increase in the vasculature even at low dose (25 µmol/kg) of the complex.


Assuntos
Meios de Contraste/química , Imagem por Ressonância Magnética/métodos , Manganês/química , Complexos de Coordenação/química , Estabilidade de Medicamentos , Humanos , Cinética , Ligantes , Albumina Sérica/química , Termodinâmica
20.
Phys Chem Chem Phys ; 22(23): 12894-12908, 2020 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-32373850

RESUMO

In photosynthesis, dioxygen formation from water is catalyzed by the oxygen evolving complex (OEC) in Photosystem II (PSII) that harbours the Mn4Ca cluster. During catalysis, the OEC cycles through five redox states, S0 to S4. In the S2 state, the Mn4Ca cluster can exist in two conformations, which are signified by the low-spin (LS) g = 2 EPR multiline signal and the high-spin (HS) g = 4.1 EPR signal. Here, we employed time-resolved membrane inlet mass spectrometry to measure the kinetics of H218O/H216O exchange between bulk water and the two substrate waters bound at the Mn4Ca cluster in the S, S, and the S3 states in both Ca-PSII and Sr-PSII core complexes from T. elongatus. We found that the slowly exchanging substrate water exchanges 10 times faster in the S than in the S state, and that the S→ S conversion has at physiological temperature an activation barrier of 17 ± 1 kcal mol-1. Of the presently suggested S models, our findings are best in agreement with a water exchange pathway involving a S state that has an open cubane structure with a hydroxide bound between Ca and Mn1. We also show that water exchange in the S3 state is governed by a different equilibrium than in S2, and that the exchange of the fast substrate water in the S2 state is unaffected by Ca/Sr substitution. These findings support that (i) O5 is the slowly exchanging substrate water, with W2 being the only other option, and (ii) either W2 or W3 is the fast exchanging substrate. The three remaining possibilities for O-O bond formation in PSII are discussed.


Assuntos
Cálcio/metabolismo , Manganês/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , Água/metabolismo , Cálcio/química , Cristalografia por Raios X , Manganês/química , Modelos Moleculares , Conformação Molecular , Oxigênio/química , Oxigênio/metabolismo , Complexo de Proteína do Fotossistema II/química , Água/química
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