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1.
Molecules ; 26(9)2021 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-34066463

RESUMO

The neodymium(III) complex of orotic acid (HOA) was synthesized and its structure determined by means of analytical and spectral analyses. Detailed vibrational analysis of HOA, sodium salt of HOA, and Nd(III)-OA systems based on both the calculated and experimental spectra confirmed the suggested metal-ligand binding mode. Significant differences in the IR and Raman spectra of the complex were observed as compared to the spectra of the ligand. The calculated vibrational wavenumbers, including IR intensities and Raman scattering activities, for the ligand and its Nd(III) complex were in good agreement with the experimental data. The vibrational analysis performed for the studied species, orotic acid, sodium salt of orotic acid, and its Nd(III) complex helped to explain the vibrational behaviour of the ligand's vibrational modes, sensitive to interaction with Nd(III). In this paper we also report preliminary results about the cytotoxicity of the investigated compounds. The cytotoxic effects of the ligand and its Nd(III) complex were determined using the MTT method on different tumour cell lines. The screening performed revealed that the tested compounds exerted cytotoxic activity upon the evaluated cell lines.


Assuntos
Neodímio/química , Ácido Orótico/química , Espectrofotometria Infravermelho/métodos , Células A549 , Antineoplásicos/farmacologia , Linhagem Celular Tumoral , Quelantes , Células HeLa , Humanos , Células Jurkat , Ligantes , Modelos Moleculares , Estrutura Molecular , Sódio/química , Análise Espectral Raman , Vibração
2.
Molecules ; 26(11)2021 May 27.
Artigo em Inglês | MEDLINE | ID: mdl-34072211

RESUMO

Fungi have become an invaluable source of bioactive natural products, with more than 5 million species of fungi spanning the globe. Fractionation of crude extract of Neodidymelliopsis sp., led to the isolation of a novel polyketide, (2Z)-cillifuranone (1) and five previously reported natural products, (2E)-cillifuranone (2), taiwapyrone (3), xylariolide D (4), pachybasin (5), and N-(5-hydroxypentyl)acetamide (6). It was discovered that (2Z)-cillifuranone (1) was particularly sensitive to ambient temperature and light resulting in isomerisation to (2E)-cillifuranone (2). Structure elucidation of all the natural products were conducted by NMR spectroscopic techniques. The antimicrobial activity of 2, 3, and 5 were evaluated against a variety of bacterial and fungal pathogens. A sodium [1-13C] acetate labelling study was conducted on Neodidymelliopsis sp. and confirmed that pachybasin is biosynthesised through the acetate polyketide pathway.


Assuntos
Ascomicetos/metabolismo , Produtos Biológicos/química , Policetídeos/isolamento & purificação , Acetamidas/química , Antraquinonas/química , Antibacterianos/química , Anti-Infecciosos/química , Anti-Infecciosos/farmacologia , Bactérias/metabolismo , Isótopos de Carbono/química , Fermentação , Espectroscopia de Ressonância Magnética , Testes de Sensibilidade Microbiana , Policetídeos/química , Sódio/química , Acetato de Sódio , Espectrometria de Massas por Ionização por Electrospray
3.
Food Chem ; 360: 129990, 2021 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-34034053

RESUMO

Novel sodium reduction strategies are urgently required by the food industry. We hypothesised that redesigning salt crystals (size, density, hydrophobicity and flow properties) will offer a new route to increase saltiness and therefore reduce sodium. Eight salts were compared with different physicochemical properties, the resultant particles were characterised and adhesion to product, loss in-pack, rate of dissolution and ultimately saltiness perception were evaluated. Principle findings included that particle adhesion was driven by particle size (r = -0.85, p = 0.008), bulk density (r = -0.80, p = 0.017) and flow properties (r = 0.77, p = 0.015); loss in-pack was associated with particle size and hydrophobicity of the salt particle while dissolution and/or saltiness perception was also driven by particle size and hydrophobicity of the salt particle. The findings offer a new set of design rules for future ingredient design for the food and flavour industries.


Assuntos
Sais/química , Cloreto de Sódio na Dieta/análise , Sódio/análise , Idoso , Feminino , Humanos , Cinética , Análise dos Mínimos Quadrados , Masculino , Espectrometria de Massas , Pessoa de Meia-Idade , Tamanho da Partícula , Sódio/química , Paladar/fisiologia , Percepção Gustatória
4.
J Chromatogr A ; 1648: 462211, 2021 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-33992993

RESUMO

The adsorption separation of L-tryptophan (L-Trp) by the weakly polar hyper-cross-linked resin XDA-200 was studied. First, the adsorption equilibria of different species of L-Trp on the resin were compared. Then, the adsorption isotherms and adsorption kinetics of L-Trp were studied at different pH values. Finally, the dynamic adsorption and separation processes of L-Trp in a packed bed of the resin were studied. The distribution coefficient of L-Trp± between the resin and an aqueous solution of L-Trp (55.69) was found to be markedly larger than that of L-Trp+ (27.53) and L-Trp- (10.42). An adsorption isotherm model depending on pH was established to simulate the adsorption equilibrium data of L-Trp. The cooperative adsorption of sodium ion (Na+) with L-Trp- cannot be ignored when the solution pH is higher than 8.0. Thus, a modified surface diffusion model considering cooperative adsorption of Na+ with L-Trp- was established. The model fitted the kinetic curves for L-Trp adsorption under different pH values satisfactorily. The surface diffusion coefficient of L-Trp first decreased and then increased as pH increased from 3 to 12. In this study, a modified film-surface diffusion model considering cooperative adsorption of Na+ with L-Trp- is proposed. Further, we show that our proposed model can predict the chromatographic peaks of L-Trp, L-glutamic acid (L-Glu), and Na+ satisfactorily.


Assuntos
Reagentes para Ligações Cruzadas/química , Modelos Teóricos , Sódio/química , Triptofano/química , Adsorção , Cromatografia , Difusão , Concentração de Íons de Hidrogênio , Cinética , Água/química
5.
J Phys Chem Lett ; 12(20): 5023-5029, 2021 May 27.
Artigo em Inglês | MEDLINE | ID: mdl-34024101

RESUMO

Lipopolysaccharides (LPS) in sea spray aerosol (SSA) particles have recently been shown to undergo heterogeneous reactions with HNO3 in the atmosphere. Here, we integrate theory and experiment to further investigate how the most abundant sea salt cations, Na+, Mg2+, and Ca2+, impact HNO3 reactions with LPS-containing SSA particles. Aerosol reaction flow tube studies show that heterogeneous reactions of SSA particles with divalent cation (Mg2+ and Ca2+) and LPS signatures were less reactive with HNO3 than those dominated by monovalent cations (Na+). All-atom molecular dynamics simulations of model LPS aggregates suggest that divalent cations cross-link the oligosaccharide chains to increase molecular aggregation and rigidity, which changes the particle phase and morphology, decreases water diffusion, and consequently decreases the reactive uptake of HNO3. This study provides new insight into how complex chemical interactions between ocean-derived salts and biogenic organic species can impact the heterogeneous reactivity of SSA particles.


Assuntos
Cálcio/química , Lipopolissacarídeos/química , Magnésio/química , Ácido Nítrico/química , Água do Mar/química , Sódio/química , Aerossóis/química , Cátions/química , Tamanho da Partícula , Sais/química , Propriedades de Superfície
6.
Int J Mol Sci ; 22(6)2021 Mar 23.
Artigo em Inglês | MEDLINE | ID: mdl-33806825

RESUMO

Metabolically active gasotransmitters (nitric oxide, carbon monoxide and hydrogen sulfide) are important signalling molecules that show therapeutic utility in oxidative pathologies. The reduced form of selenium, hydrogen selenide (HSe-/H2Se), shares some characteristics with these molecules. The simple selenide salt, sodium hydroselenide (NaHSe) showed significant metabolic activity, dose-dependently decreasing ex vivo O2 consumption (rat soleus muscle, liver) and transiently inhibiting mitochondrial cytochrome C oxidase (liver, heart). Pharmacological manipulation of selenoprotein expression in HepG2 human hepatocytes revealed that the oxidation status of selenium impacts on protein expression; reduced selenide (NaHSe) increased, whereas (oxidized) sodium selenite decreased the abundance of two ubiquitous selenoproteins. An inhibitor of endogenous sulfide production (DL-propargylglycine; PAG) also reduced selenoprotein expression; this was reversed by exogenous NaHSe, but not sodium hydrosulfide (NaHS). NaHSe also conferred cytoprotection against an oxidative challenge (H2O2), and this was associated with an increase in mitochondrial membrane potential. Anesthetized Wistar rats receiving intravenous NaHSe exhibited significant bradycardia, metabolic acidosis and hyperlactataemia. In summary, NaHSe modulates metabolism by inhibition of cytochrome C oxidase. Modification of selenoprotein expression revealed the importance of oxidation status of selenium therapies, with implications for current clinical practice. The utility of NaHSe as a research tool and putative therapeutic is discussed.


Assuntos
Compostos de Selênio/farmacologia , Compostos de Selênio/uso terapêutico , Animais , Antioxidantes/farmacologia , Antioxidantes/uso terapêutico , Técnicas de Química Sintética , Relação Dose-Resposta a Droga , Avaliação Pré-Clínica de Medicamentos , Regulação da Expressão Gênica/efeitos dos fármacos , Humanos , Oxirredução , Estresse Oxidativo/efeitos dos fármacos , Compostos de Selênio/síntese química , Compostos de Selênio/química , Selenoproteínas/genética , Sódio/química , Selenito de Sódio/química
7.
Biochemistry (Mosc) ; 86(3): 370-381, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33838636

RESUMO

Modulation of cytokine production by physical activity is of considerable interest, since it might be a promising strategy for correcting metabolic processes at both cellular and systemic levels. The content of IL-6, IL-8, and IL-15 in the plasma and the concentration of monovalent cations in the skeletal muscles of trained and untrained mice were studied at different periods after static and dynamic exercises. Dynamic loads caused an increase in the IL-6 content and decrease in the IL-15 content in the plasma of untrained mice, but produced no effect on the concentration of IL-8. In trained mice, the effect of a single load on the concentration of IL-6 and IL-15 in the plasma was enhanced, while the concentration of IL-8 decreased. Static loads produced a similar, but more pronounced effect on the plasma concentration of IL-6 and IL-15 compared the dynamic exercises; however, the concentration of IL-8 in response to the static exercise increased significantly. Prior training reinforced the described response for all the myokines studied. Dynamic load (swimming) increased the intracellular content of sodium but decreased the content of potassium in the mouse musculus soleus. Similar response was observed after the static load (grid hanging) in the musculus biceps; but no correlation of this response with the prior training was found. Possible mechanisms involved in the regulation of cytokine secretion after exercise are discussed, including triggering of gene transcription in response to changes in the [Na+]i/[K+]I ratio.


Assuntos
Citocinas/sangue , Músculo Esquelético/fisiologia , Condicionamento Físico Animal , ATPase Trocadora de Sódio-Potássio/metabolismo , Animais , Cátions Monovalentes , Interleucina-15/sangue , Interleucina-6/sangue , Interleucina-8/sangue , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Músculo Esquelético/química , Músculo Esquelético/enzimologia , Músculo Esquelético/metabolismo , Plasma/metabolismo , Potássio/análise , Potássio/química , Sódio/análise , Sódio/química
8.
Molecules ; 26(4)2021 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-33671928

RESUMO

Metal organic framework (MOF)-derived carbon nanostructures (MDC) synthesized by either calcinations or carbonization or pyrolysis are emerging as attractive materials for a wide range of applications like batteries, super-capacitors, sensors, water treatment, etc. But the process of transformation of MOFs into MDCs is time-consuming, with reactions requiring inert atmospheres and reaction time typically running into hours. In this manuscript, we report the transformation of 1,4-diazabicyclo[2.2.2]octane, (DABCO)-based MOFs into iron nitride nanoparticles embedded in nitrogen-doped carbon nanotubes by simple, fast and facile microwave pyrolysis. By using graphene oxide and carbon fiber as microwave susceptible surfaces, three-dimensional nitrogen-doped carbon nanotubes vertically grown on reduced graphene oxide (MDNCNT@rGO) and carbon fibers (MDCNT@CF), respectively, were obtained, whose utility as anode material in sodium-ion batteries (MDNCNT@rGO) and for EMI (electromagnetic interference) shielding material (MDCNT@CF) is reported.


Assuntos
Carbono/química , Fontes de Energia Elétrica , Fenômenos Eletromagnéticos , Estruturas Metalorgânicas/química , Nanoestruturas/química , Nitrogênio/química , Sódio/química , Fibra de Carbono/química , Eletrodos , Íons , Nanoestruturas/ultraestrutura , Nanotubos de Carbono/ultraestrutura , Espectroscopia Fotoeletrônica , Pirólise , Análise Espectral Raman , Difração de Raios X
9.
Int J Biol Macromol ; 174: 485-493, 2021 Mar 31.
Artigo em Inglês | MEDLINE | ID: mdl-33548307

RESUMO

Three phenolic acids including p-hydroxybenzoic acid (PHBA), 3,4-dihydroxybenzoic acid, (DHBA), and gallic acid (GA) were grafted onto native pectin (Na-Pe) through enzymatic method. Ultraviolet-visible spectrometry, Fourier transform infrared spectroscopy, and 1H NMR analyses were used to explore the reaction mechanism. Results indicated that the p-hydroxyl of the phenolic acids reacted with the methoxycarbonyl of pectin through transesterification, and a covalent connection was formed. The phenolic acid contents of PHBA modified pectin (Ph-Pe), DHBA modified pectin (Dh-Pe), and GA modified pectin (Ga-Pe) were 20.18%, 18.87%, and 20.32%, respectively. After acylation with phenolic acids, the 1,1-diphenyl-2-picryl hydrazine clearance of pectin changed from 7.68% (Na-Pe) to 6.88% (Ph-Pe), 40.80% (Dh-Pe), and 90.30% (Ga-Pe), whereas its inhibition ratio of pectin increased from 3.11% (Na-Pe) to 35.02% (Ph-Pe), 66.36% (Dh-Pe), and 77.89% (Ga-Pe). Moreover, compared with Na-Pe, modified pectins exhibited better emulsification properties and stronger antibacterial activities against both Escherichia coli and Staphylococcus aureus.


Assuntos
Ácido Gálico/química , Hidroxibenzoatos/química , Parabenos/química , Pectinas/farmacologia , Acilação , Antibacterianos/química , Antibacterianos/farmacologia , Emulsificantes/química , Emulsificantes/farmacologia , Escherichia coli/efeitos dos fármacos , Escherichia coli/crescimento & desenvolvimento , Esterificação , Espectroscopia de Ressonância Magnética , Testes de Sensibilidade Microbiana , Viabilidade Microbiana/efeitos dos fármacos , Pectinas/química , Sódio/química , Espectroscopia de Infravermelho com Transformada de Fourier , Staphylococcus aureus/efeitos dos fármacos , Staphylococcus aureus/crescimento & desenvolvimento
10.
Int J Biol Macromol ; 175: 459-472, 2021 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-33549663

RESUMO

As an emerging pollutant treatment material, hydrogel is known for its good adsorption capacity and environmental friendliness. In this study, a composite material of acrylic acid as the polymerization monomer grafted sodium lignosulfonate and guar gum was prepared, which provided a channel for adsorbing metal ions with its abundant active functional groups and porous structure. The optimized synthesized product was applied to the removal of Cu2+ and Co2+ in a one-component system and a multi-component system, and the maximum ion adsorption capacities obtained were determined to be 709 mg g-1 of Cu2+, 601 mg g-1 of Co2+, respectively. The adsorption kinetics and isotherms were well fitted by the pseudo second-order kinetic model and the Langmuir isotherm, showing that the adsorption of Cu2+ and Co2+ by the adsorbent belongs to the chemisorption on monolayer. XPS results confirmed the successful adsorption of Cu2+ and Co2+ by GG/SLS. Surface complexation was proposed to be the main mechanism for GG/SLS adsorbent to remove heavy metal ions. In addition, the use of recycling research showed that the adsorbent has good chemical stability. These results provided valuable information for designing highly efficient adsorbents that can be used as a high-quality wastewater treatment material.


Assuntos
Galactanos/química , Lignina/análogos & derivados , Mananas/química , Gomas Vegetais/química , Purificação da Água/métodos , Adsorção , Dióxido de Carbono/química , Dióxido de Carbono/isolamento & purificação , Cobre/química , Cobre/isolamento & purificação , Hidrogéis/química , Concentração de Íons de Hidrogênio , Íons , Cinética , Lignina/química , Metais Pesados , Sódio/química , Águas Residuárias/química , Poluentes Químicos da Água/química
11.
Nucleic Acids Res ; 49(4): 2306-2316, 2021 02 26.
Artigo em Inglês | MEDLINE | ID: mdl-33524157

RESUMO

Vast G-quadruplexes (GQs) are primarily folded by one, two, or four G-rich oligomers, rarely with an exception. Here, we present the first NMR solution structure of a trimolecular GQ (tri-GQ) that is solely assembled by the self-trimerization of d(GTTAGG), preferentially in Na+ solution tolerant to an equal amount of K+ cation. Eight guanines from three asymmetrically folded strands of d(GTTAGG) are organized into a two-tetrad core, which features a broken G-column and two width-irregular grooves. Fast strand exchanges on a timescale of second at 17°C spontaneously occur between folded tri-GQ and unfolded single-strand of d(GTTAGG) that both species coexist in dynamic equilibrium. Thus, this tri-GQ is not just simply a static assembly but rather a dynamic assembly. Moreover, another minor tetra-GQ that has putatively tetrameric (2+2) antiparallel topology becomes noticeable only at an extremely high strand concentration above 18 mM. The major tri-GQ and minor tetra-GQ are considered to be mutually related, and their reversible interconversion pathways are proposed accordingly. The sequence d(GTTAGG) could be regarded as either a reading frame shifted single repeat of human telomeric DNA or a 1.5 repeat of Bombyx mori telomeric DNA. Overall, our findings provide new insight into GQs and expect more functional applications.


Assuntos
DNA/química , Quadruplex G , Potássio/química , Sódio/química , Animais , Bombyx/genética , Temperatura Alta , Humanos , Modelos Moleculares , Ressonância Magnética Nuclear Biomolecular , Telômero/química
12.
Plant Physiol Biochem ; 160: 239-256, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33524921

RESUMO

High salt concentrations in the growing medium can severely affect the growth and development of plants. It is imperative to understand the different components of salt-tolerant network in plants in order to produce the salt-tolerant cultivars. High-affinity potassium transporter- and myelocytomatosis proteins have been shown to play a critical role for salinity tolerance through exclusion of sodium (Na+) ions from sensitive shoot tissues in plants. Numerous genes, that limit the uptake of salts from soil and their transport throughout the plant body, adjust the ionic and osmotic balance of cells in roots and shoots. In the present review, we have tried to provide a comprehensive report of major research advances on different mechanisms regulating plant tolerance to salinity stress at proteomics, metabolomics, genomics and transcriptomics levels. Along with the role of ionic homeostasis, a major focus was given on other salinity tolerance mechanisms in plants including osmoregulation and osmo-protection, cell wall remodeling and integrity, and plant antioxidative defense. Major proteins and genes expressed under salt-stressed conditions and their role in enhancing salinity tolerance in plants are discussed as well. Moreover, this manuscript identifies and highlights the key questions on plant salinity tolerance that remain to be discussed in the future.


Assuntos
Plantas/química , Potássio/química , Salinidade , Tolerância ao Sal , Sódio/química , Regulação da Expressão Gênica de Plantas , Íons
13.
Int J Biol Macromol ; 171: 234-241, 2021 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-33412203

RESUMO

Despite numerous applications of nanofibrous alginate (Alg) mat, its facile fabrication via electrospinning is still challenging. The low alginate content compared to the carrier polymer and existence of impurities are the main drawbacks of existing approaches. The purpose of this research is both to study and improve alginate electrospinnability by focusing on the effect of inter- and intramolecular hydrogen bonding. Based on hard and soft acids and bases (HSAB) theory, the Na+ cations (carboxylate counter-cation) were substituted with a harder acid, Li+ cation, to increase the strength of ionic interaction and decrease the density of hydrogen bonding. Viscosity and electrical conductivity measurements as well as FTIR and 1H NMR revealed a lower intramolecular hydrogen bonding density in Li-Alg. SEM images showed improvement of alginate electrospinnability for Li-Alg compared to the salts of Na-Alg and K-Alg. This study sheds more light on underlying reasons hindering alginate electrospinning and introduces a simple method for fabrication of nanofibers with high alginate content.


Assuntos
Alginatos/química , Nanofibras/química , Configuração de Carboidratos , Cátions/química , Teoria da Densidade Funcional , Condutividade Elétrica , Ligação de Hidrogênio , Lítio/química , Microscopia Eletrônica de Varredura , Potássio/química , Sódio/química , Espectroscopia de Infravermelho com Transformada de Fourier , Viscosidade
14.
Carbohydr Polym ; 256: 117429, 2021 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-33483018

RESUMO

An eco-friendly dust suppression and sand-fixation liquid mulching film was prepared via a facile secondary spraying process in this work. Water polyurethane (WPU) was blended with dissolved humic acid (HA) firstly, and then the blend solutions (HWPU) were sprayed on the surface of cationic starch (CS) / sodium lignosulfonate (LS) film to synthesize the liquid mulching film (CLS-HWPU). The effects of liquid mulching film composition on mechanical properties in dry and wet states were investigated. The results showed that the optimal composition of liquid mulching film was: 3% (CS), 0.9 % (LS), 1.5 % (glycerol), 2% (HA), and 30 % (WPU). The CLS-HWPU liquid mulching films were characterized in terms of light transmittance, degradation performance test, contact angle test, scanning electron microscopy (SEM), total reflectance-Fourier transform infrared spectrometer (ATR-FTIR), thermo gravimetric analysis (TGA), and erosion resistance test. The results indicated that the CLS-HWPU film had good UV resistance, thermal stability, anti-erosion, and biodegradation. The CLS-HWPU film meets the demand of dust suppression and sand-fixation in dusty areas and desertification environments, which opens a new application field for liquid mulching film with high safety and environmental protection.


Assuntos
Poliuretanos/química , Areia/química , Solo/química , Água/química , Biodegradação Ambiental , Cátions , Poeira , Eletrólitos , Eletrônica , Glicerol/química , Substâncias Húmicas , Interações Hidrofóbicas e Hidrofílicas , Lignina/análogos & derivados , Lignina/química , Plásticos , Polímeros/química , Sódio/química , Espectroscopia de Infravermelho com Transformada de Fourier , Amido , Estresse Mecânico , Propriedades de Superfície , Resistência à Tração , Termogravimetria
15.
Carbohydr Polym ; 256: 117564, 2021 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-33483065

RESUMO

Superior mechanical properties, high adsorption capacity, and excellent regeneration property are crucial design criterions to develop a new-type aerogel for adsorptive applications towards heavy metal removal from water. Herein, chitosan and melamine not only introduced abundant functional groups to increase adsorbing sites for lead ions, but also reinforced the three-dimensional network skeleton structure of absorbents to improve the service life in adsorption applications. As-fabricated alginate/melamine/chitosan aerogel can extract Pb (II) from aqueous solution efficiently, i.e., the optimum adsorption quantity of 1331.6 mg/g at pH 5.5, which exhibited excellent and selective adsorption capacity for Pb (II) against the competition of coexisting divalent metal ions. More importantly, alginate/melamine/chitosan aerogel could be regenerated using dilute acidic solution and recovered well after eight adsorption-desorption cycles. This work might offer a new idea for design and preparation of biomass-based aerogel sorbents with promising prospect in the remediation of Pb (II)-contaminated wastewater.


Assuntos
Alginatos/química , Quitosana/química , Íons , Chumbo/química , Triazinas/química , Adsorção , Materiais Biocompatíveis/química , Biomassa , Géis , Concentração de Íons de Hidrogênio , Cinética , Metais , Metais Pesados , Sódio/química , Espectroscopia de Infravermelho com Transformada de Fourier , Estresse Mecânico , Temperatura , Águas Residuárias/química , Poluentes Químicos da Água/química , Purificação da Água
16.
J Colloid Interface Sci ; 588: 657-669, 2021 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-33261818

RESUMO

Biomass, as a continuously available raw material, is widely used to produce hard carbon. However, many researchers have ignored the natural special morphology of biomass and the influence of oxygen on the sodium storage performance. Here, we use the cilia of the setaria viridis as the precursor to obtain a fiber-like oxygen-doped hierarchical porous hard carbon (SVC). The sodium storage mechanism of SVC is studied by controlling the pyrolysis temperature. Studies have shown that the natural fibrous structure and vertical holes of SVC can provide channels for the rapid penetration of electrolyte. The appropriate nanocrystal size affords commodious circumstances for the insertion of Na+. More importantly, the increase in carbonization temperature will change the bonding mode of carbon and oxygen, promote the rupture of single bonds and retain the existence of double bonds, which is beneficial to the improvement of coulombic efficiency and reversible capacity. The hybrid sodium storage mechanism composed of insertion behavior and capacitance behavior promotes SVC to have higher reversible capacity (285.4 mAh g-1 at 0.05 A g-1) and excellent rate performance (90.7 mAh g-1 at 5 A g-1). This research provides some new ideas for the study of hard carbon.


Assuntos
Carbono , Oxigênio , Sódio , Biomassa , Porosidade , Sódio/química
17.
Int J Biol Macromol ; 166: 789-797, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-33157133

RESUMO

The ι-carrageenan degrading marine bacterium, Cellulophaga baltica, was isolated from the surface of a filamentous red alga Vertebrata fucoides. Maximum ι-carrageenase production was optimized by single-factor experiments. Optimal fermentation conditions were 1.6 g/L furcellaran, 4 g/L yeast extract as carbon sources, 5 g/L sea salt, and 48 h of incubation time at 20 °C. Extracellular ι-carrageenase from the culture supernatant was purified by ultrafiltration, ammonium sulfate precipitation, and finally by anion-exchange chromatography, showed a 26-fold increase in specific activity as compared to that in the crude enzyme. According to the results from SDS-PAGE and HPLC-SEC, the molecular weight of the purified enzyme was estimated to be 31 kDa. The purified enzyme showed the maximum specific activity of 571 U/mg at 40 °C and pH 7.5-8.0. It maintained 73% of the total activity below 40 °C and 90% of its total activity at pH 7.2. Notably, the enzyme is a cold-adapted ι-carrageenase, which showed 33.4% of the maximum activity at 10 °C. The enzyme was stimulated by Na+, K+, and NH4+, whereas Ca2+, Mg2+, Fe3+, sea salt, and EDTA acted as enzyme inhibitors.


Assuntos
Proteínas de Bactérias/metabolismo , Carragenina/metabolismo , Fermentação , Flavobacteriaceae/enzimologia , Glicosídeo Hidrolases/metabolismo , Compostos de Amônio/química , Proteínas de Bactérias/química , Estabilidade Enzimática , Flavobacteriaceae/metabolismo , Glicosídeo Hidrolases/química , Potássio/química , Sódio/química , Especificidade por Substrato
18.
Analyst ; 146(2): 547-557, 2021 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-33165468

RESUMO

Hexaammineruthenium(iii), RuHex3+, is a DNA-binding metal complex that is widely used as a redox marker for the indirect determination of DNA coverage at the electrode surface. The conversion of electrochemically quantifiable surface excess of RuHex3+ into DNA surface coverage requires the knowledge of the binding site size of RuHex3+ (s). Traditionally, s on surface-immobilized DNA has been assumed to be equivalent to that on solution-phase DNA, which was experimentally determined in previous studies. Nevertheless, the different local microenvironments existing inside DNA monolayers in comparison to that in bulk solutions cast doubt on the validity of this assumption. In this report, we used electrochemical techniques to investigate s on surface-immobilized DNA. The values of s inside the DNA monolayers were found to be significantly smaller than that reported on solution-phase DNA. Besides, s was found to depend on the DNA packing density and became larger by increasing the DNA surface coverage or hybridizing the surface-tethered DNAs with complementary strands. Our data indicate that the RuHex3+ method, in which an s value of 3 nucleotides is used for the conversion of RuHex3+ to DNA surface coverage, does not always give reliable results.


Assuntos
DNA/química , Ouro/química , Compostos de Rutênio/química , Sítios de Ligação , Eletroquímica , Eletrodos , Hibridização de Ácido Nucleico , Sódio/química , Propriedades de Superfície
19.
Environ Geochem Health ; 43(5): 2037-2048, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33244649

RESUMO

Helicobacter pylori can be found in the stomach of about half of the humans, and a large population can be associated with serious diseases. To survive in the stomach H. pylori increases the pH locally by producing ammonia which binds to H+ becoming ammonium. This work investigated the effects on the in-vitro growth of H. pylori of a natural cation-exchanger mainly composed (≈70%) of clinoptilolite and mordenite. The zeolitized material from Cuba was evaluated in its original form (M), as well as in its Na- (M-Na) and Zn-exchanged (M-Zn) counterparts. In the preliminary agar cup diffusion test, H. pylori revealed susceptibility only to M-Zn, with a direct relationship between concentration and width of inhibition halo. Further experiments evidenced that bacterium replication increases when ammonium is supplied to the growth medium and decreases when zeolites subtract NH4+ via ion exchange. Due to the multi-cationic population of its zeolites M was not effective enough in removing ammonium and, in the Minimum Inhibitory Concentration (MIC) test, allowed bacterial growth even at a concentration of 50 mg/mL. Inhibition was achieved with M-Na because it contained sodium zeolites capable of maximizing NH4+ subtraction, although the MIC was high (30 mg/mL). M-Zn evidenced a more effective inhibitory capacity, with a MIC of 4 mg/mL. Zinc has antimicrobial properties and H. pylori growth was affected by Zn2+ released from clinoptilolite and mordenite. These zeolites, being more selective towards NH4+ than Zn2+, can also subtract ammonium to the bacterium, thus enhancing the efficacy of M-Zn.


Assuntos
Silicatos de Alumínio/farmacologia , Antibacterianos/farmacologia , Helicobacter pylori/efeitos dos fármacos , Zeolitas/farmacologia , Zinco/farmacologia , Silicatos de Alumínio/química , Compostos de Amônio/metabolismo , Compostos de Amônio/farmacologia , Antibacterianos/química , Cuba , Helicobacter pylori/crescimento & desenvolvimento , Troca Iônica , Testes de Sensibilidade Microbiana , Sódio/química , Zeolitas/química , Zinco/química
20.
Food Chem ; 338: 127840, 2021 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-32822903

RESUMO

In bottled wines, haze and turbidity are phenomena to be avoided. Since bentonite fining is a common process to clarify wines removing heat unstable proteins, a theoretical study on the adsorption of three Charged Model Molecules (CMMs, egg albumin, polyphenols and riboflavin) was carried out to deep comprehend this chemical phenomenon. Four bentonites were adopted and finely characterized together with the potential release of Na+ and Ca2+ cations, revealing suitable for RT albumin removal within 120 min. Better results in terms of adsorbed quantity were achieved by adopting 12%v/v EtOH/H2O solvent and by swelling bentonites for 24 h before use. With the most performing sample (Na/Ca_0.27), a comprehensive study on simultaneous adsorption of the three CMMs was performed, resulting in polyphenols adsorption increase due to their interactions with albumin. Notwithstanding the majority of albumin and riboflavin was successfully removed, ca. 40-50% of tested polyphenols was preserved.


Assuntos
Bentonita/química , Vinho/análise , Adsorção , Cálcio/química , Cálcio/metabolismo , Cromatografia Líquida de Alta Pressão , Cinética , Espectrometria de Massas , Ovalbumina/química , Polifenóis/química , Riboflavina/química , Sódio/química , Sódio/metabolismo
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