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1.
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
2.
Ecotoxicol Environ Saf ; 202: 110921, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32800256

RESUMO

Jarosite is one of the iron oxyhydroxysulfate minerals that are commonly found in acid mine drainage (AMD) systems. In natural environments, phosphate and sulfate reducing bacteria (SRB) may be coupled to jarosite reduction and transformation. In this research, the effect of phosphate on jarosite reduction by SRB and the associated secondary mineral formation was studied using batch experiments. The results indicated that Fe3+ is mainly reduced by biogenic S2- in this experiment. The effect of PO43- on jarosite reduction by SRB involved not only a physico-chemical factor but also a microbial factor. Phosphate is an essential nutrient, which can support the activity of SRB. In the low PO43- treatment, the production of total Fe2+ was found to be slightly larger than that in the zero PO43- treatment. Sorption of PO43- effectively elevated jarosite stability via the formation of inner sphere complexes, which, therefore, inhibited the reductive dissolution of jarosite. At the end of the experiment, the amounts of total Fe2+ accumulation were determined to be 4.54 ± 0.17a mM, 4.66 ± 0.22a mM, 3.91 ± 0.04b mM and 2.51 ± 0.10c mM (p < 0.05) in the zero, low, medium and high PO43- treatments, respectively, following the order of low PO43- treatment > zero PO43- treatment > medium PO43- treatment > high PO43- treatment. PO43- loading modified the transformation pathways for the jarosite mineral, as well. In the zero PO43- treatment, the jarosite diffraction lines disappeared, and mackinawite dominated at the end of the experiment. Compared to PO43--free conditions, vivianite was found to become increasingly important at higher PO43- loading conditions. These findings indicate that PO43- loading can influence the broader biogeochemical functioning of AMD systems by impacting the reactivity and mineralization of jarosite mineral.


Assuntos
Bactérias/metabolismo , Compostos Férricos/química , Fosfatos/química , Sulfatos/química , Adsorção , Biodegradação Ambiental , Compostos Ferrosos , Ferro/química , Compostos de Ferro/química , Minerais , Mineração , Oxirredução
3.
Yakugaku Zasshi ; 140(8): 955-960, 2020.
Artigo em Japonês | MEDLINE | ID: mdl-32741867

RESUMO

A nickel-aluminium-zirconium complex-layered hydroxide (NAZ), which was synthesized using each inorganic sulfate mixing ratio of 0.9 : 1.0 : 0.1, was prepared and calcined at different temperatures. The physicochemical properties of the NAZ were analyzed by scanning electron microscopy, specific surface area, number of hydroxyl groups, and pore volume. The specific surface area, number of hydroxyl groups, and pore volume of NAZ was 51.9 m2/g, 1.08 mmol/g, and 0.27 µL/g, respectively. The amount of phosphate ion adsorbed onto NAZ was higher than that onto calcined NAZ at different temperatures. Therefore, the interaction between phosphate ions and NAZ was assessed using the elemental distribution analysis and the binding energy. After adsorption, the intensity of phosphorus atoms increased, indicating that the phosphate ions were adsorbed onto the NAZ surface. Additionally, phosphorus peaks (189 eV for 2s and 130 eV for 2p), which were not detected before adsorption, were clearly detected after adsorption. On the other hand, the intensity of the sulfur peak (165 eV for 2p) decreased after adsorption. Thus, we evaluated the ion exchange between phosphate ion and sulfate ion in the interlayer space of the NAZ. As a result, the correlation coefficient between the amount of phosphate ion adsorbed and the amount of sulfate ion released was positively correlated (r=0.960). Therefore, it can be clearly stated that one of the adsorption mechanisms of phosphate ions was related to ion exchange in the interlayer space of the NAZ. These findings are useful for preventing the eutrophication and recovery of phosphate ion in water environments.


Assuntos
Complexos de Coordenação/química , Complexos de Coordenação/síntese química , Hidróxidos/química , Hidróxidos/síntese química , Fosfatos/química , Adsorção , Alumínio , Fenômenos Químicos , Eutrofização , Troca Iônica , Íons , Microscopia Eletroquímica de Varredura , Níquel , Zircônio
4.
Biomolecules ; 10(8)2020 08 05.
Artigo em Inglês | MEDLINE | ID: mdl-32764519

RESUMO

Lupane-type pentacyclic triterpenes such as betulin and betulinic acid play an important role in the search for new therapies that would be effective in controlling viral infections. The aim of this study was the synthesis and evaluation of in vitro anti-HIV-1 activity for phosphate derivatives of 3-carboxyacylbetulin 3-5 as well as an in silico study of new compounds as potential ligands of the C-terminal domain of the HIV-1 capsid-spacer peptide 1 (CA-CTD-SP1) as a molecular target of HIV-1 maturation inhibitors. In vitro studies showed that 28-diethoxyphosphoryl-3-O-(3',3'-dimethylsuccinyl)betulin (compound 3), the phosphate analog of bevirimat (betulinic acid derivative, HIV-1 maturation inhibitor), has IC50 (half maximal inhibitory concentration) equal to 0.02 µM. Compound 3 inhibits viral replication at a level comparable to bevirimat and is also more selective (selectivity indices = 1250 and 967, respectively). Molecular docking was used to examine the probable interaction between the phosphate derivatives of 3-carboxyacylbetulin and C-terminal domain (CTD) of the HIV-1 capsid (CA)-spacer peptide 1 (SP1) fragment of Gag protein, designated as CTD-SP1. Compared with interactions between bevirimat (BVM) and the protein, an increased number of strong interactions between ligand 3 and the protein, generated by the phosphate group, were observed. These compounds might have the potential to also inhibit SARS-CoV2 proteins, in as far as the intrinsically imprecise docking scores suggest.


Assuntos
Fármacos Anti-HIV/síntese química , Simulação de Acoplamento Molecular , Triterpenos/química , Produtos do Gene gag do Vírus da Imunodeficiência Humana/metabolismo , Fármacos Anti-HIV/farmacologia , Sítios de Ligação , Fosfatos/química , Ligação Proteica , Succinatos/química , Succinatos/farmacologia , Triterpenos/farmacologia , Produtos do Gene gag do Vírus da Imunodeficiência Humana/química
5.
Chemosphere ; 260: 127461, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32673865

RESUMO

Tris (1-chloro-2-propyl) phosphate (TCPP) is a chlorinated organic phosphate used in various applications as a flame retardant and plasticizer. TCPP is a known suspected carcinogen and is not effectively removed by traditional water treatments such as biological, chlorination, and UV irradiation. In this study, the UV/H2O2 reaction was employed to degrade TCPP in water. TCPP was effectively degraded in the UV/H2O2 reaction by pseudofirst-order kinetics. The second-order rate constant of the reaction between the TCPP and OH radical was determined to be 4.35 (±0.13) × 108 M-1 s-1 using the competition kinetics with nitrobenzene as a reference compound. The degradation of TCPP was affected by the amount of H2O2, pH, and coexisting water components such as HCO3-, NO3-, and humic acid. Approximately 64.2% of total organic carbon (TOC) in TCPP was mineralized in 12 h during the UV/H2O2 reaction, whereas chloride (Cl-) and phosphate (PO43-) ions were identified as ionic byproducts with the recoveries of 96% chlorine (Cl) and 50% phosphorus (P). Five organic transformation products (TPs) of TCPP were also identified using LC-qTOF/MS. Considering the identified TPs, the main degradation pathway of TCPP during the UV/H2O2 reaction was found to be OH-radical-induced hydroxylation. Finally, a 70% decrease in bioluminescence inhibition in Vibrio fischeri was observed during the UV/H2O2 reaction, and the time-toxicity profile was similar to the time-peak area profile of TPs. The result of this study implies that TCPP can be efficiently removed with significant mineralization and toxicity reduction by the UV/H2O2 process.


Assuntos
Compostos Organofosforados/química , Cloretos , Cloro , Retardadores de Chama/análise , Substâncias Húmicas , Peróxido de Hidrogênio/química , Cinética , Organofosfatos/química , Oxirredução , Fosfatos/química , Plastificantes/química , Raios Ultravioleta , Água , Poluentes Químicos da Água/análise , Purificação da Água
6.
Chemosphere ; 259: 127469, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32640377

RESUMO

In this study, Mg and/or Al modified biochars (MABC1, MBC2, ABC3) prepared by co-precipitation were to explore their phosphate adsorption capacity from aqueous solution and the potential for soil phosphate interception. The results revealed that MABC composites contained more functional groups than MBC and showed a higher surface area than ABC. The surface of MABC contained dispersed MgAl2O4, Mg(OH)2, AlOOH and Al2O3 crystals that were associated with its enhanced maximum phosphate adsorption capacity (153.40 mg g-1). According to Langmuir model, the maximum adsorption capacity of MABC was 15.91, 1.85, and 93.54 times the capacity of MBC, ABC, and raw biochar (BC4), respectively. The addition of MABC in red soil could significantly slow down the release of soil phosphorus, and MABC also had a stronger phosphate interception capacity (59.89%) than other BCs. In summary, MABC exhibits superior phosphate adsorption and interception capacity, making it ideal for treatment and prevention of phosphorus-polluted water.


Assuntos
Fosfatos/química , Poluentes do Solo/química , Adsorção , Hidróxido de Alumínio , Óxido de Alumínio , Carvão Vegetal , Fósforo/química , Solo , Água
7.
Chemosphere ; 258: 127327, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32559493

RESUMO

Microparticle sorbents (MPSs) containing nano-Fe3O4 core, nano-layered double hydroxides shell modified with different transitional elements (TE-MPSs) are effective for capturing phosphate from wastewater. In present article, different TE-MPSs loaded with Ce, La, Zr and Hf were synthesized and the phosphorous removal performances were compared. The molecular-level mechanism of phosphate adsorption was successfully simulated by pseudo-atom model based on virtual crystal approximation method, which was in line with the spectroscopic data. The results confirmed the inter-sphere complexation reaction between phosphate and TE-MPSs under neutral pH. And the adsorption mechanism probably changed during cycles of adsorption/regeneration. As revealed by elemental composition analysis, ion exchange mechanism probably played an important part in phosphate adsorption in Cycle 1 while the ligand complexation became dominant after regenerated with NaOH in the following cycles. This work indicates that the highly effective, easily separable and repeatedly usable TE-MPSs has the potential for phosphate sequestration and recovery from sewage wastewater.


Assuntos
Nanopartículas de Magnetita , Fosfatos/química , Adsorção , Concentração de Íons de Hidrogênio , Hidróxidos/química , Fósforo , Esgotos , Elementos de Transição , Águas Residuárias/química
8.
Chemistry ; 26(43): 9407, 2020 Aug 03.
Artigo em Inglês | MEDLINE | ID: mdl-32567105

RESUMO

Invited for the cover of this issue are the groups of Roman Dembinski, Mehran Mostafavi, and Amitava Adhikary at the Polish Academy of Sciences, Université Paris-Saclay, and Oakland University. The image depicts a doughnut as a way of illustrating the hole transfer process. Read the full text of the article at 10.1002/chem.202000247.


Assuntos
Nucleosídeos/química , Fosfatos/química
9.
Food Chem ; 327: 127057, 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-32464461

RESUMO

Chilling injury (CI) restricts the quality and shelf life of bell pepper fruits; reducing these CI-induced detrimental effects is therefore of high economic and agricultural relevance. Here, we investigated the effects of trisodium phosphate (TSP), salicylic acid (SA), and TSP + SA treatments on pepper fruits under cold stress at 4 °C for 25 d. Combined TSP + SA treatment performed an optimal effect. Specifically, TSP + SA treatment enhanced fatty-acid desaturation efficiency, as indicated by the increased expression of key fatty acid desaturase genes, and higher content of unsaturated fatty acids. Meanwhile, TSP + SA treatment inhibited the CI-induced membrane damage, manifested as lower electrolyte leakage and malondialdehyde content. Furthermore, low field-nuclear magnetic resonance and proline content also revealed that TSP + SA treatment mitigated CI through enhancing water retention in pepper fruits. Collectively, our results may shed new light on optimizing the low-temperature storage conditions of post-harvest peppers.


Assuntos
Capsicum/química , Ácidos Graxos/química , Fosfatos/química , Ácido Salicílico/química , Água/química , Capsicum/efeitos dos fármacos , Capsicum/metabolismo , Parede Celular/efeitos dos fármacos , Temperatura Baixa , Ácidos Graxos/metabolismo , Frutas/química , Frutas/efeitos dos fármacos , Frutas/metabolismo , Malondialdeído/química , Malondialdeído/metabolismo , Permeabilidade/efeitos dos fármacos , Fosfatos/farmacologia , Prolina/química , Ácido Salicílico/farmacologia
10.
Chemosphere ; 256: 127124, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32450354

RESUMO

In the present work, talc (a low-cost clay) encapsulated salts alginate (TAL) beads were synthesized by cross-linking with lanthanum ion and tested for phosphate adsorption. Multiple methods were applied for the characterization of composites. The combined effect of talc and lanthanum improved phosphate removal performance of TAL beads. Factors such as talc content, La3+ concentration, adsorbent dosage, pH, co-existing ions (Cl-, NO3- and SO42-) were studied in batch experiments. The optimized TAL-7 beads exhibited satisfactory selectivity towards phosphate in the coexistence of competing anions and could remain efficient phosphate removal in the pH range of 4-6. The phosphate removal efficiency reached to 95% with a maximum uptake of 16.4 mg P/g obtained at the optimal pH 4. Further experiments suggested that Langmuir isotherm model and the pseudo-second-order kinetic model could well describe the phosphate adsorption process of TAL-7 beads. Moreover, TAL-7 beads exhibited superior phosphate fixation performance in the long-term experiment. The results from adsorption experiment and characterization analysis demonstrated that TAL-7 beads could be a cost-effective and promising biosorbent for phosphate adsorption and fixation in the aqueous environment.


Assuntos
Alginatos/química , Hidrogéis/química , Lantânio/química , Fosfatos/análise , Talco/química , Poluentes Químicos da Água/análise , Adsorção , Ânions , Concentração de Íons de Hidrogênio , Íons/química , Cinética , Fosfatos/química , Água/química , Poluentes Químicos da Água/química , Purificação da Água/métodos
11.
Chemosphere ; 256: 126968, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32428738

RESUMO

The recycling of nutrients from wastewater and their recovery in the form of valuable products is an effective strategy to accelerate the circular economy concept. Phosphorus recovery from wastewater by struvite crystallization (MgNH4PO4·6H2O) is one of the most applied techniques to compensate for the increasing demand and to slow down the depletion rate of phosphate rocks. Using low-cost magnesium sources, such as seawater, improves the financial sustainability of struvite production. In this study, the potential of seawater for struvite crystallization versus the commonly used magnesium source, MgCl2, was tested by crystal growth and kinetic experiments. The impact of ammonium concentration, magnesium concentration and pH on the growth kinetics of struvite in synthetic and real reject water were studied. The results showed that simultaneous precipitation of calcium phosphate was insignificant when using seawater, while presence of struvite seeds diminished it further. Among the supersaturation regulators, pH had the most significant effect on the struvite growth with both MgCl2 and seawater, while high N:P molar ratios further improved the struvite crystal growth by seawater. The N:P molar ratios higher than 6 and Mg:P molar ratios higher than 0.2 are recommended to improve the crystal growth kinetics. It was concluded that seawater is a promising alternative magnesium source and the control of supersaturation regulators (i.e., Mg:P, N:P and pH) is an effective strategy to control the reaction kinetics and product properties.


Assuntos
Modelos Químicos , Água do Mar/química , Estruvita/química , Fosfatos de Cálcio , Cristalização , Cinética , Magnésio/química , Cloreto de Magnésio/química , Compostos de Magnésio/química , Minerais , Fosfatos/química , Fósforo/química , Reciclagem , Águas Residuárias/química
12.
Nat Commun ; 11(1): 2528, 2020 05 20.
Artigo em Inglês | MEDLINE | ID: mdl-32433521

RESUMO

Arene dearomatization reactions are an important class of synthetic technologies for the rapid assembly of unique chemical architectures. Herein, we report a catalytic protocol to initiate a carboamination/dearomatization cascade that proceeds through transient sulfonamidyl radical intermediates formed from native sulfonamide N-H bonds leading to 1,4-cyclohexadiene-fused sultams. Importantly, this work demonstrates a facile approach to employ two-dimensional aromatic compounds as modular building blocks to generate richly substituted, three-dimensional compounds. These reactions occur at room temperature under visible light irradiation and are catalyzed by the combination of an iridium(III) photocatalyst and a dialkyl phosphate base. Reaction optimization, substrate scope, mechanistic features, and synthetic applications of this transformation are presented.


Assuntos
Radicais Livres/química , Irídio/química , Catálise/efeitos da radiação , Ligação de Hidrogênio , Luz , Estrutura Molecular , Fosfatos/química , Sulfonamidas/química
13.
Chemosphere ; 256: 127056, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32447108

RESUMO

Trivalent cerium (Ce(Ⅲ)) was demonstrated to have great potential for phosphate (P) removal. Besides the valence states, the relationship of nano-structure and adsorption capacity needs further study to explore more efficient adsorbents. Herein, a series of Ce(Ⅲ)-terephthalate (BDC) metal-organic framework (MOF) with linker deficiencies are fabricated to achieve excellent P capture. The defective density can be increased by decreasing the reaction time and the ratio of organic linkers/metal. TGA reveals Ce-BDC-48 synthesized with BDC:Ce ratio of 1:1 for 48 h possessed 2.5 missing linkers per inorganic node. And the P uptake of Ce-BDC-48 was 35% higher than that of Ce-BDC-72 without defects. The maximum adsorption capacity of Ce-BDC-48 was 278.8 mg/g for P and 128.0 mg/g for fluoride (F), respectively. The adsorption mechanism illustrates that both P and F mainly focus on the Ce(Ⅲ) active sites to achieve ligand exchange. The competing adsorption of P and F at the lower concentration of F (50 mg/L) indicates that the interference of F for P removal is insignificant on account of the selective preferential order of P. However, with the increment of F concentration (100 mg/L), amount of F with small sizes gathering around the adsorbent surface enlarge the steric hindrance to hinder the access of P, leading to the sharp decline of P uptake. This study not only provides promising candidate by the design of structural defects for the P removal in practical application but also give a deep analysis on the adsorption mechanism of P with competing F surrounded.


Assuntos
Cério/química , Fluoretos/química , Fosfatos/química , Poluentes Químicos da Água/química , Adsorção
14.
Biochim Biophys Acta Proteins Proteom ; 1868(8): 140441, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32371149

RESUMO

Dengue represents a substantial public health burden, particularly in low-resource countries. Non-structural protein 3 (NS3) is a multifunctional protein critical in the virus life cycle and has been identified as a promising anti-viral drug target. Despite recent crystallographic studies of the NS3 helicase domain, only subtle structural nucleotide-dependent differences have been identified, such that its coupled ATPase and helicase activities remain mechanistically unclear. Here we use molecular dynamics simulations to explore the nucleotide-dependent conformational landscape of the Dengue virus NS3 helicase and identify substantial changes in the protein flexibility during the ATP hydrolysis cycle. We relate these changes to the RNA-protein interactions and proposed translocation models for other monomeric helicases. Furthermore, we report a novel open-loop conformation with a likely escape route for Pi after hydrolysis, providing new insight into the conformational changes that underlie the ATPase activity of NS3.


Assuntos
Trifosfato de Adenosina/química , Vírus da Dengue/química , Fosfatos/química , Proteínas não Estruturais Virais/química , Trifosfato de Adenosina/metabolismo , Motivos de Aminoácidos , Sítios de Ligação , Vírus da Dengue/enzimologia , Hidrólise , Simulação de Dinâmica Molecular , Fosfatos/metabolismo , Ligação Proteica , Conformação Proteica em alfa-Hélice , Conformação Proteica em Folha beta , Domínios e Motivos de Interação entre Proteínas , RNA Helicases/química , RNA Helicases/metabolismo , Serina Endopeptidases/química , Serina Endopeptidases/metabolismo , Termodinâmica , Proteínas não Estruturais Virais/metabolismo
15.
Chemosphere ; 255: 126937, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32402882

RESUMO

Phosphate competes with arsenate for sorption sites on poorly crystalline iron and aluminum (hydr)oxides. The competition has implications e.g. for the management of arsenic-contaminated soil and water. Phosphate competition with arsenate on mixed phases containing both iron and aluminum (hydr)oxides has rarely been investigated. Here, the phosphate competition with arsenate on mixtures of poorly crystalline aluminum hydroxide (Alhox) and ferrihydrite (Fh), was investigated in batch experiments at pH 6.5. X-ray absorption spectroscopy (XAS) was performed on the phosphorus and arsenic K edges, which offered a unique insight in the partitioning of arsenate and phosphate on mixed Alhox-Fh sorbents. Under the studied conditions the sorption capacity of the mixed sorbents (per mol Al or Fe) increased at higher Alhox to Fh ratios. The XAS measurements provided direct evidence that phosphate competed more effectively with arsenate for sorption sites on Alhox than on Fh. For example, in a mixture with 50% of both sorbents and with similar additions of arsenate and phosphate, 71% of the oxyanions adsorbed on Fh and 46% on Alhox were arsenate. Consequently, phosphate may mobilize arsenate more easily from mixed iron-aluminum matrices that are rich in aluminum.


Assuntos
Hidróxido de Alumínio/química , Arseniatos/química , Fosfatos/química , Adsorção , Alumínio/química , Arsênico/química , Compostos Férricos , Ferro/química , Óxidos/química , Água
16.
Chimia (Aarau) ; 74(4): 252-256, 2020 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-32331542

RESUMO

Polyoxophosphates are ubiquitous in nature and play important roles in biological systems and in the environment. Pyrophosphate (PPi), an important member of this family, is produced in over 200 biochemical reactions and is a marker in clinical diagnosis. In addition to its endogenous role, PPi alias E450 is currently used as preservative, emulsifier or taste intensifier in foodstuff. Despite this widespread occurrence and biological importance, it is rather surprising that robust chemical systems that detect selectively and sensitively PPi in challenging matrices are still lacking. This mini review focuses on metal-salen complexes as reaction-based fluorescent sensors for the selective detection of PPi and other phosphates. The mode of detection is based on a novel disassembly approach in which the metal ion is sequestered by the target analyte from the complex and the metal-free ligand hydrolyses spontaneously into its fluorescent subunits. Optimizations of the probe and applications for PPi detection in cells and foodstuff are described.


Assuntos
Fosfatos/química , Etilenodiaminas , Corantes Fluorescentes , Metais
17.
Nat Microbiol ; 5(7): 917-928, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32251370

RESUMO

Bacteria have evolved diverse mechanisms to fend off predation by bacteriophages. We previously identified the Dnd system, which uses DndABCDE to insert sulfur into the DNA backbone as a double-stranded phosphorothioate (PT) modification, and DndFGH, a restriction component. Here, we describe an unusual SspABCD-SspE PT system in Vibrio cyclitrophicus, Escherichia coli and Streptomyces yokosukanensis, which has distinct genetic organization, biochemical functions and phenotypic behaviour. SspABCD confers single-stranded and high-frequency PTs with SspB acting as a nickase and possibly introducing nicks to facilitate sulfur incorporation. Strikingly, SspABCD coupled with SspE provides protection against phages in unusual ways: (1) SspE senses sequence-specific PTs by virtue of its PT-stimulated NTPase activity to exert its anti-phage activity, and (2) SspE inhibits phage propagation by introducing nicking damage to impair phage DNA replication. These results not only expand our knowledge about the diversity and functions of DNA PT modification but also enhance our understanding of the known arsenal of defence systems.


Assuntos
Bacteriófagos/fisiologia , Interações Hospedeiro-Patógeno , Fosfatos/metabolismo , Streptomyces/fisiologia , Streptomyces/virologia , Adesinas Bacterianas/química , Adesinas Bacterianas/genética , Adesinas Bacterianas/metabolismo , Sítios de Ligação , Ativação Enzimática , Genoma Bacteriano , Interações Hospedeiro-Patógeno/genética , Modelos Moleculares , Fases de Leitura Aberta , Fosfatos/química , Ligação Proteica , Conformação Proteica , Multimerização Proteica
18.
Nucleosides Nucleotides Nucleic Acids ; 39(1-3): 407-425, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32310030

RESUMO

Telomerase activity has been regarded as a critical step in cellular immortalization and carcinogenesis and because of this, regulation of telomerase represents an attractive target for anti-tumor specific therapeutics. Recently, one avenue of cancer research focuses on antisense strategy to target the oncogenes or cancer driver genes, in a sequence specific fashion to down-regulate the expression of the target gene. The protein catalytic subunit, human telomerase reverse transcriptase (hTERT) and the template RNA component (hTERC) are essential for telomerase function, thus theoretically, inhibition of telomerase activity can be achieved by interfering with either the gene expression of hTERT or the hTERC of the telomerase enzymatic complex. The present study showed that phosphorothioate antisense oligonucleotide (sASO)-nuclear localization signal (NLS) peptide conjugates targeting hTERC could inhibit telomerase activity very efficiently at 5 µM concentration but less efficiently at 1 µM concentration. On the other hand, siRNA targeting hTERT mRNA could strongly suppress hTERT expression at 200 nM concentration. It was also revealed that siRNA targeting hTERT could induce telomere attrition and then irreversible arrest of proliferation of cancer cells.


Assuntos
Pontos de Checagem do Ciclo Celular/efeitos dos fármacos , Inibidores Enzimáticos/química , Inibidores Enzimáticos/farmacologia , Sinais de Localização Nuclear/química , Oligonucleotídeos Antissenso , Fosfatos/química , Telomerase/antagonistas & inibidores , Telômero/química , Proliferação de Células/efeitos dos fármacos , Ativação Enzimática , Células HeLa , Humanos , Peptídeos/química , RNA Mensageiro/genética , RNA Interferente Pequeno/genética , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , Telomerase/química , Células Tumorais Cultivadas
19.
Chemosphere ; 253: 126691, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32294599

RESUMO

Low redox potential in flooded soils may affect phosphate bioavailability by reducing iron oxides or formation of new minerals. To investigate phosphate behavior in anoxic conditions, goethite was selected as a soil model and coated by humic acid (HA) and sodium borohydride was used as a reducing agent. Adsorption experiments were conducted in 0.1 M NaNO3 as a function of pH in oxic (Eh = +254 to +448 mV) and suboxic (Eh = -162 to +167 mV) conditions for four phosphate concentrations (0.05-0.8 mM). CD-MUSIC and NOM-CD models in combination with Extended Stern model were used to describe the experimental data. Results show that by increasing pH and carbon content in the organo-mineral composites, the released phosphate to the solution increases in both oxic and suboxic conditions. In suboxic conditions, as a result of sodium borohydride dissociation in water and consequently boron release to the solution, at high loading of boron and low loading of phosphate, boron can compete with phosphate for the surface reactive sites and decrease its adsorption. On the other hand, ferrous iron can attenuate boron effect and promote phosphate adsorption. The results indicated that goethite surface is resistant to the reductive transformation that may occur at relatively low redox potential due to its high crystalline character and thermodynamic stability. HA may, however, promote the formation of amorphous iron phases, which consequently might induce phosphate adsorption in OM-mineral composites. The derived affinity constants in oxic conditions described the experimental data of suboxic conditions reasonably well.


Assuntos
Compostos de Ferro/química , Minerais/química , Modelos Químicos , Fosfatos/química , Adsorção , Boro , Carbono , Compostos Férricos , Substâncias Húmicas , Ferro , Solo/química
20.
Chemosphere ; 250: 126245, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32234617

RESUMO

Hydrothermal experiments with magnesium, ammonium, and phosphate (MAP) solution at a temperature of 120 OC for 24 h and pH (9 and 10), whilst effects of varying Mg2+/Ca2+/HCO-3 ratios on struvite crystallization were examined. The study was performed to investigate their effects on the quality and quantity of crystals using the XRPD Rietveld refinement and SEM method. Obviously, the struvite crystallization was inhibited through the forming of calcite, dolomite, hydroxyapatite, sylvite, and Mg-whitlockite under different pH conditions. In the absence of Ca2+ and HCO-3 ions, struvite and dittmarite were formed at pH solutions (9 and 10). Struvite proportion reduced with pH (9 and 10) under Mg2+/Ca2+/HCO-3 ratios (1:1:1 and 2:1:1), and depleted under the Mg2+/Ca2+/HCO-3 ratio of 1:2:2. An obvious change in morphologies of crystals into nanosized particles was observed. Results of the low proportion of struvite for experiments with Mg2+/Ca2+/HCO-3 molar ratios may be a drawback for phosphate recovery.


Assuntos
Cálcio/química , Estruvita/química , Compostos de Amônio , Carbonato de Cálcio , Cálcio na Dieta , Cristalização , Íons , Magnésio , Compostos de Magnésio/química , Fosfatos/química
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