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1.
Molecules ; 26(4)2021 Feb 13.
Artículo en Inglés | MEDLINE | ID: mdl-33668455

RESUMEN

Novel polymer composites based on polyamide-imide Torlon and deep eutectic solvent (DES) were fabricated and adapted for separation processes. DES composed of zinc chloride and acetamide in a ratio of 1:3 M was first chosen as a Torlon-modifier due to the possibility of creating composites with a uniform filling of the DES through the formation of hydrogen bonds. The structure of the membranes was investigated by scanning electron microscopy and X-ray diffraction analysis; thermal stability was determined by thermogravimetric analysis and mass spectrometry. The surface of the composites was studied by determining the contact angles and calculating the surface tension. The transport properties were investigated by such membrane methods as pervaporation and gas separation. It was found that the inclusion of DES in the polymer matrix leads to a significant change in the structure and surface character of composites. It was also shown that DES plays the role of a plasticizer and increases the separation performance in the separation of liquids and gases. Torlon/DES composites with a small amount of modifier were effective in alcohol dehydration, and were permeable predominantly to water impurities in isopropanol. Torlon/DES-5 demonstrates high selectivity in the gas separation of O2/N2 mixture.


Asunto(s)
Gases/aislamiento & purificación , Imidas/química , Nylons/química , Solventes/química , Espectrometría de Masas , Conformación Molecular , Nitrógeno/química , Oxígeno/química , Permeabilidad , Tensión Superficial , Temperatura , Termogravimetría , Agua , Difracción de Rayos X
2.
Molecules ; 26(4)2021 Feb 15.
Artículo en Inglés | MEDLINE | ID: mdl-33671928

RESUMEN

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.


Asunto(s)
Carbono/química , Suministros de Energía Eléctrica , Fenómenos Electromagnéticos , Estructuras Metalorgánicas/química , Nanoestructuras/química , Nitrógeno/química , Sodio/química , Fibra de Carbono/química , Electrodos , Iones , Nanoestructuras/ultraestructura , Nanotubos de Carbono/ultraestructura , Espectroscopía de Fotoelectrones , Pirólisis , Espectrometría Raman , Difracción de Rayos X
3.
Carbohydr Polym ; 260: 117770, 2021 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-33712128

RESUMEN

Chitin-derived three-dimensional nanomaterials has tremendous potential in pesticide residue analysis as an attractive green substitute for toxic solvents. The work presented herein focuses on constructing the environmentally friendly nitrogen-containing chitin-derived carbon microspheres (N-CCMP) for the efficient adsorption of neonicotinoid pesticides (NPs) including acetamiprid, clothianidin, imidacloprid and thiamethoxam. The N-CCMP displayed hierarchical porous structure, uniform size distribution, and excellent specific surface area of 680.8 m2 g-1. The N-CCMP with N-heterocyclic ring structure and surface oxygen functional groups exhibited good affinity to NPs, which was beneficial for the rapid adsorption. Then, the N-CCMP were utilized as sorbent in extraction of NP residues. Under the optimum conditions, the relative recoveries in water and juice sample were in the range of 85 %-116 % and 74 %-108 %, with relative standard deviations (RSDs) of 0.1 %∼5.2 % and 0.7 %∼5.2 %, respectively. The extraction performance of N-CCMP were still over 80 % after 5 times of reuse.


Asunto(s)
Carbono/química , Quitina/química , Microesferas , Neonicotinoides/química , Nitrógeno/química , Residuos de Plaguicidas/química , Adsorción , Cromatografía Líquida de Alta Presión , Agua Dulce/análisis , Jugos de Frutas y Vegetales/análisis , Neonicotinoides/análisis , Residuos de Plaguicidas/análisis , Porosidad , Espectrometría de Masas en Tándem
4.
Molecules ; 26(4)2021 Feb 20.
Artículo en Inglés | MEDLINE | ID: mdl-33672726

RESUMEN

This study was conducted to identify a new alkaline and thermophilic protease (Ba.St.Pr) produced from Bacillus stearothermophilus isolated from olive oil mill sols and to evaluate its culture conditions, including temperature, pH, carbon and nitrogen sources, and incubation time. The optimum culture conditions for cell growth (10 g/L) and protease production (5050 U/mL) were as follows: temperature 55 °C, pH 10, inoculation density 8 × 108 CFU/mL, and incubation time 24 h. The use of 3% yeast extract as the nitrogen sources and galactose (7.5 g/L) as the carbon sources enhanced both cell growth and protease production. Using reversed-phase analytical HPLC on C-8 column, the new protease was purified with a molecular mass of approximately 28 kDa. The N-terminal sequence of Ba.St.Pr exhibited a high level of identity of approximately 95% with those of Bacillus strains. Characterization under extreme conditions revealed a novel thermostable and alkaline protease with a half-life time of 187 min when incubated with combined Ca2+/mannitol. Ba.St.Pr demonstrated a higher stability in the presence of surfactant, solvent, and Ca2+ ions. Consequently, all the evaluated activity parameters highlighted the promising properties of this bacterium for industrial and biotechnological applications.


Asunto(s)
Bacillus/enzimología , Proteínas Bacterianas/química , Biotecnología , Endopeptidasas/química , Aceite de Oliva/metabolismo , Temperatura , Proteínas Bacterianas/biosíntesis , Proteínas Bacterianas/aislamiento & purificación , Carbono/química , Carbono/metabolismo , Endopeptidasas/biosíntesis , Endopeptidasas/aislamiento & purificación , Concentración de Iones de Hidrógeno , Nitrógeno/química , Nitrógeno/metabolismo , Aceite de Oliva/química
5.
Food Chem ; 349: 129160, 2021 Jul 01.
Artículo en Inglés | MEDLINE | ID: mdl-33550018

RESUMEN

Indigo carmine (IC) dye is hazardous and allergenic for humans even though it has been excessively used in a wide range of industries. Therefore, the quantitative determination of IC is still challenging. Herein, for the first time, we have developed fluorometric and colorimetric dual-mode nanoprobe derived from the ion-pair association complex between the negatively charged IC and positively charged N@C-dots in pH = 3.0. Consequently, the binding between N@C-dots and IC resulted in cyan blue and quenching of N@C-dots fluorescence. The dependence of the fluorescence response on IC concentrations was linear over the range of 0.73-10.0 µM (R2 = 0.9989) with LOD of 0.24 µM. On the other hand, the linearity of the colorimetric method ranged from 9.97 to 80.0 µM (R2 = 0.9986) with LOD of 3.3 µM. The sensor was applied for estimation of IC in fruit juice and soft drink without the need for exhaustive extraction steps.


Asunto(s)
Bebidas/análisis , Carbono/química , Análisis de los Alimentos/métodos , Contaminación de Alimentos/análisis , Carmin de Índigo/análisis , Límite de Detección , Nitrógeno/química , Colorimetría , Fluorometría , Humanos
6.
Nat Commun ; 12(1): 830, 2021 02 05.
Artículo en Inglés | MEDLINE | ID: mdl-33547297

RESUMEN

In marine and freshwater oxygen-deficient zones, the remineralization of sinking organic matter from the photic zone is central to driving nitrogen loss. Deep blooms of photosynthetic bacteria, which form the suboxic/anoxic chlorophyll maximum (ACM), widespread in aquatic ecosystems, may also contribute to the local input of organic matter. Yet, the influence of the ACM on nitrogen and carbon cycling remains poorly understood. Using a suite of stable isotope tracer experiments, we examined the transformation of nitrogen and carbon under an ACM (comprising of Chlorobiaceae and Synechococcales) and a non-ACM scenario in the anoxic zone of Lake Tanganyika. We find that the ACM hosts a tight coupling of photo/litho-autotrophic and heterotrophic processes. In particular, the ACM was a hotspot of organic matter remineralization that controlled an important supply of ammonium driving a nitrification-anammox coupling, and thereby played a key role in regulating nitrogen loss in the oxygen-deficient zone.


Asunto(s)
Ciclo del Carbono/fisiología , Carbono/química , Chlorobi/metabolismo , Ciclo del Nitrógeno/fisiología , Nitrógeno/química , Synechococcus/metabolismo , Compuestos de Amonio/química , Compuestos de Amonio/metabolismo , Anaerobiosis/fisiología , Procesos Autotróficos , Carbono/metabolismo , Chlorobi/química , Clorofila/química , Clorofila/metabolismo , República Democrática del Congo , Ecosistema , Marcaje Isotópico , Lagos/química , Lagos/microbiología , Nitrificación/fisiología , Nitrógeno/metabolismo , Oxidación-Reducción , Synechococcus/química , Tanzanía
7.
Food Chem ; 349: 129131, 2021 Jul 01.
Artículo en Inglés | MEDLINE | ID: mdl-33581434

RESUMEN

Soy sauce is a traditional fermented soy food for enhancing the umami taste in Asian cuisines. In this study, 16S rRNA gene throughput sequencing analysis showed the bacterial communities and the changes in soy sauce during fermentation. Weissella, Bacillus and Lactococcus were the most abundant at genus level. The uncultured bacterium Weissella and Lactococcus had relatively high abundance at species level. Alpha diversity analysis indicated the bacterial community diversity increased at fermentation initiation, while decreased as fermentation progressed. Based on beta-diversity analysis, four clusters including cluster I (time point A-F), cluster II (G,H), cluster III (I,J) and cluster IV(K) were distinctly separated, indicating the fermentation time significantly affected bacterial community diversity. Also, close associations were found between the bacterial communities in soy sauce and its amino acid nitrogen, organic acid and reducing sugar contents during fermentation. Therefore, it will provide important information for optimization of the soy sauce production process.


Asunto(s)
Aminoácidos/análisis , Bacterias/genética , Fermentación , Secuenciación de Nucleótidos de Alto Rendimiento , Alimentos de Soja/análisis , Alimentos de Soja/microbiología , Azúcares/análisis , Aminoácidos/química , Bacterias/aislamiento & purificación , Bacterias/metabolismo , Nitrógeno/química , ARN Ribosómico 16S/genética , Gusto
8.
J Chromatogr A ; 1641: 461990, 2021 Mar 29.
Artículo en Inglés | MEDLINE | ID: mdl-33640806

RESUMEN

This study demonstrates a novel application of nitrogen-doped carbon dots (NCDs) to enable the separation of different lengths of single-stranded DNA (ssDNA) by eletrokinetic means. Carbon dots have recently found widespread application in the fields of sensing, diagnostics, and healthcare due to their biocompatibility and low toxicity. In light of growing interest in the use of ssDNA aptamers over antibodies in the fields of biosensor development and drug delivery, it is important to establish a simple and effective method for aptamer separation. In this study, we employed NCDs as buffer additives in a capillary electrophoresis (CE)-based method, giving rise to the separation of FAM-labeled ssDNA samples ranging from 32 to 100 bases in length, with resolutions ranging from 1.30 - 1.77. In particular, we adopted a capillary transient isotachophoresis (ctITP) system with laser-induced fluorescence (LIF) detection, with both the separation and sample buffers modified by the addition of 30 µg/mL NCDs. These nanomaterials were prepared by a simple hydrothermal method from a mixture of citric acid and ethylenediamine. The NCDs themselves are highly fluorescent and photostable. As components in the background electrolyte, they did not interfere with the fluorescence emission of the FAM-labeled DNA samples. Under the conditions employed, no separation could be achieved in the absence of the NCDs nor with undoped CDs. The results show that NCDs function as buffer additives capable of enhancing electrokinetic-based separations of ssDNA, and hence, provide a new application for these carbon nanomaterials.


Asunto(s)
Carbono/química , ADN de Cadena Simple/aislamiento & purificación , Electroforesis Capilar/métodos , Isotacoforesis/métodos , Rayos Láser , Nitrógeno/química , Electroósmosis , Fluorescencia
9.
Ecotoxicol Environ Saf ; 208: 111713, 2021 Jan 15.
Artículo en Inglés | MEDLINE | ID: mdl-33396044

RESUMEN

A novel Microcystis bloom caused by Microcystis densa has occurred in a typical subtropical reservoir every spring and summer since 2012, and it has caused several ecological and economic losses. To determine the environmental factors that influence the growth and physiological characteristics of M. densa, we investigated the variations in physicochemical factors and M. densa cell density from 2007 to 2017. The results showed that the urea-N concentration increased significantly (from 0.02 ± 0.00-0.20 ± 0.01 mg N l-1), whereas other factors did not vary significantly. NO3--N and urea-N concentrations were higher than the NH4+-N concentration during the M. densa bloom. The nitrogen composition changed, and urea-N and NO3--N became a major nitrogen sources in the reservoir. Water temperature and increased urea-N concentrations were the primary factors that influenced variations in M. densa cell density (45.5%, p < 0.05). Laboratory experiments demonstrated that M. densa cultured with urea-N exhibited a higher maximum cell density (9.8 ± 0.5 × 108 cells l-1), more cellular pigments for photosynthesis (chlorophyll a and phycocyanin) and photoprotection (carotenoid), and more proteins than those cultured with NH4+-N and NO3--N. These results suggested that M. densa cultured with urea-N exhibited preferable growth and physiological conditions. Moreover, M. densa exhibited an increased maximum specific uptake rate (0.93 pg N cell-1 h-1) and reduced half-saturation constant (0.03 mg N l-1) for urea-N compared with NH4+-N and NO3--N, suggesting that M. densa preferred urea-N as its major nitrogen source. These results collectively indicated that the increasing urea-N concentration was beneficial for the growth and physiological conditions of M. densa. This study provided ten years of field data and detailed physiological information supporting the critical effect of urea-N on the growth of a novel bloom species M. densa. These findings helped to reveal the mechanism of M. densa bloom formation from the perspective of dissolved organic nitrogen.


Asunto(s)
Eutrofización , Microcystis/crecimiento & desarrollo , Nitrógeno/metabolismo , Urea/metabolismo , Proteínas Bacterianas/metabolismo , Microcystis/metabolismo , Nitratos/análisis , Nitratos/metabolismo , Nitrógeno/análisis , Nitrógeno/química , Pigmentos Biológicos/metabolismo , Temperatura , Urea/análisis
10.
Food Chem ; 346: 128974, 2021 Jun 01.
Artículo en Inglés | MEDLINE | ID: mdl-33465571

RESUMEN

The effects of argon and nitrogen cold plasma treatments on the lipolytic enzymes activity in wheat germ were investigated. Using argon as plasma gas, the residual activity of lipase and lipoxygenase decreased to 42.50% and 87.72%, respectively after 30 min. Switching plasma input gas to nitrogen, the residual activities of lipase and lipoxygenase after the same time of atmospheric cold plasma (ACP) treatment were 77.50% and 92.52%, respectively. The antioxidant potential and phenolic compounds show no significant difference during ACP duration. However, the remaining activities of lipase and lipoxygenase after 30 min steam autoclaving were 6.25% and 18.60%, respectively. Also, the antioxidant activity and total phenolic content reduced by 14.70% and 30.80%, respectively. In brief, the ACP treatment efficiency was function of the input gas and the treatment time. The presented results about the input gas impacts would be useful in industrial development of ACP application for wheat germ stabilization.


Asunto(s)
Lipasa/metabolismo , Lipooxigenasa/metabolismo , Gases em Plasma/química , Triticum/enzimología , Antioxidantes/química , Argón/química , Nitrógeno/química , Fenoles/química , Temperatura , Triticum/química
11.
J Chromatogr A ; 1637: 461833, 2021 Jan 25.
Artículo en Inglés | MEDLINE | ID: mdl-33373796

RESUMEN

The reliable determination of arsine (AsH3) and phosphine (PH3) in hydrogen (H2), nitrogen (N2) and liquefied petroleum gas (LPG) is of great importance because of its drastic effects on the efficiency of catalysts, as well as the strict regulations associated with health, safety and environmental issues. It is challenging for an analyst to determine the parts per billion of AsH3 and PH3 in H2, N2, and LPG at low and high pressures without collection procedures using adsorption, desorption, and dissolution techniques. To overcome this analytical need an analytical methodology was developed, employing a variable pressure sampler (VPS) coupled to a gas chromatograph (GC) with mass spectrometry (MS) for the identification and quantification of traces of AsH3 and PH3. The instrumentation, tubing and accessories of the VPS were made of passivated steel to avoid losses from absorption of AsH3 and PH3 in the steel which would generate significant analytical problems. The VPS had a homogeneous heating block that prevented analyte losses from condensation. With the VPS, 24 AsH3 and PH3 standards were prepared between 0.005 and 0.1 mg kg-1 in balance of H2, N2 and LPG. The separation and quantification of the analytes was achieved with an improved GC with 4 valves and 5 columns in series that guaranteed the elimination of impurities. The proposed method was optimized in VPS and GC-MS and then validated showing highly accaptable linearity (r2 > 0.9999), detection limits (<0.0009 mg kg-1), limits of quantification (<0.003 mg kg-1), intra-day and inter-day precision and accuracy (<1.14% and ≤3.0% respectively), recovery for the standard addition (86-109%), P values> 0.05 for the test Student's t paired who evaluated the effect of the matrix on pressure and concentration. The speed of analysis was high (<5.2 min). The method was applied to real samples, showing values between 0.005 and 0.1 mg kg-1 and an effect on the efficiency of the Ziegler Natta catalyst between 5 and 56%.


Asunto(s)
Arsenicales/análisis , Cromatografía de Gases y Espectrometría de Masas/métodos , Hidrógeno/química , Nitrógeno/química , Petróleo/análisis , Fosfinas/análisis , Humanos , Límite de Detección , Reproducibilidad de los Resultados
12.
Int J Food Microbiol ; 339: 109014, 2021 Feb 02.
Artículo en Inglés | MEDLINE | ID: mdl-33333444

RESUMEN

The objective of this study was to develop a method with improved sensitivity for Campylobacter jejuni detection in foods. Nitrogen-doped carbon nanodots (N-CNDs) were synthesized and added to an enrichment medium (Bolton broth) at a concentration of 10 mg/mL. A light-emitting diode (LED) at a wavelength of 425 nm was used to irradiate the N-CNDs-supplemented enrichment medium to induce an exothermic reaction for 1 h. Additionally, a monoclonal antibody specific to C. jejuni NCTC11168 was developed using hybridoma cells to aid detection. The C. jejuni detection capabilities of N-CNDs-supplemented enrichment medium and the conventional Bolton broth enrichment, were compared using duck samples. C. jejuni in the enrichment was detected with the monoclonal antibody based-indirect enzyme-linked immunosorbent assay (ID-ELISA). The N-CNDs-supplemented enrichment medium showed a better C. jejuni detection capability than the conventional Bolton broth enrichment. Additionally, data from ID-ELISA showed excellent detection efficiency and a shortened detection time in the N-CNDs-supplemented enrichment medium after LED irradiation at 425 nm. These results indicate that 1-h LED irradiation at 425 nm to Bolton broth supplemented with the N-CNDs increased the detection efficiency and shortened the detection time with the monoclonal antibody for C. jejuni in food.


Asunto(s)
Campylobacter jejuni/aislamiento & purificación , Ensayo de Inmunoadsorción Enzimática , Microbiología de Alimentos/métodos , Carne/microbiología , Nanopartículas/química , Animales , Anticuerpos Monoclonales/metabolismo , Bacterias/efectos de los fármacos , Carbono/química , Carbono/farmacología , Medios de Cultivo , Patos/microbiología , Nitrógeno/química , Nitrógeno/farmacología
13.
Food Chem ; 340: 128056, 2021 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-33032152

RESUMEN

In the study, a novel kind of peptides-zinc (AKP-Zn) chelate was obtained using the Antarctic krill (Euphausia superba) peptides (AKP) as raw material, the reaction was carried out with the mass ratio of the AKP to ZnSO4·7H2O of 1:2 at pH 6.0 and 60 °C for 10 min. The structure and composition of the AKP, including particle size, Zeta potential, molecular weight distribution, amino acid composition, microstructure and surface elemental composition, changed significantly after chelating with zinc. The result of Fourier transform infrared spectroscopy indicated that zinc could be chelated by carboxyl oxygen and amino nitrogen atoms of the AKP. Furthermore, compared with zinc sulfate and zinc gluconate, the AKP-Zn chelate was more stable at various pH conditions and the simulated gastrointestinal digestion experiment. These findings would provide a scientific basis for developing new zinc supplements and the high-value utilization of Antarctic krill protein resource.


Asunto(s)
Proteínas de Artrópodos/química , Quelantes/química , Péptidos/química , Péptidos/farmacocinética , Zinc/química , Aminoácidos/análisis , Animales , Proteínas de Artrópodos/farmacocinética , Suplementos Dietéticos , Digestión , Euphausiacea/química , Concentración de Iones de Hidrógeno , Peso Molecular , Nitrógeno/química , Espectroscopía Infrarroja por Transformada de Fourier , Zinc/análisis
14.
Food Chem ; 335: 127677, 2021 Jan 15.
Artículo en Inglés | MEDLINE | ID: mdl-32739822

RESUMEN

Facile detection of malachite green (MG), a toxic dye, in aquaculture is urgently demanded for environment and food safety. Herein, we design a novel fluorescent probe, namely red emissive Se,N,Cl-doped carbon dots (CDs), to accurately determinate MG. CDs are prepared by hydrothermal treatment of selenourea and o-phenylenediamine in HCl solution. This material exhibits excitation-independent dual emissions at 625 and 679 nm, with a high quantum yield of 23.6%. A selective and sensitive fluorescent sensor toward MG is established based on inner filter effect, because both the excitation and emission light of CDs can be strongly absorbed by MG. The fluorescence quenching of CDs is linear to the MG concentration over the range of 0.07-2.50 µM with a low detection limit of 21 nM. Trace-level analysis of MG in fish tissue is successfully explored, demonstrating the great potential of the proposed sensor for MG monitoring in aquatic products.


Asunto(s)
Productos Pesqueros/análisis , Análisis de los Alimentos/métodos , Contaminación de Alimentos/análisis , Puntos Cuánticos/química , Colorantes de Rosanilina/análisis , Animales , Carbono/química , Cloro/química , Fluorescencia , Colorantes Fluorescentes/química , Análisis de los Alimentos/instrumentación , Nitrógeno/química , Compuestos de Organoselenio/química , Selenio/química , Espectrometría de Fluorescencia , Urea/análogos & derivados , Urea/química
15.
Chemosphere ; 262: 127895, 2021 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-32799151

RESUMEN

In order to improve the adsorption efficiency of ammonia nitrogen in low temperature wastewater, the modified activated carbon (Fe-AC) was prepared by impregnation-calcination modification of Fe(NO3)3. The characterization results indicated that the total pore volume, specific surface area and the point of zero charge of activated carbon increased after modification. A better adsorption effect was achieved under neutral condition than under alkaline or acidic condition. The effect of Ca2+ on competitive adsorption of NH4+ was greater than that of Na+ when both cations were present. Pseudo-first-order kinetic model was confirmed to be consistent with Fe-AC adsorption kinetic data, and Langmuir model was consistent with adsorption isotherm data. The adsorption thermodynamics demonstrated that the ammonia nitrogen adsorption process by Fe-AC was spontaneous and low-temperature was helpful to improve the adsorption capacity. The mechanism of adsorption of ammonia nitrogen by Fe-AC was the comprehensive effect of physical adsorption and chemical adsorption, which was the essential reason for improving the adsorption efficiency of ammonia nitrogen by Fe-AC at a low temperature. This research offered a new way for the modification of activated carbon and a new method for the removal of ammonia nitrogen at a low temperature.


Asunto(s)
Amoníaco/química , Carbón Orgánico/química , Aguas Residuales/química , Contaminantes Químicos del Agua/química , Adsorción , Frío , Hierro/química , Cinética , Nitrógeno/química , Temperatura , Termodinámica , Contaminantes Químicos del Agua/análisis
16.
Int J Mol Sci ; 22(1)2020 Dec 25.
Artículo en Inglés | MEDLINE | ID: mdl-33375617

RESUMEN

Molecular mechanisms for N2 fixation (solar NH3) and CO2 conversion to C2+ products in enzymatic conversion (nitrogenase), electrocatalysis, metal complexes and plasma catalysis are analyzed and compared. It is evidenced that differently from what is present in thermal and plasma catalysis, the electrocatalytic path requires not only the direct coordination and hydrogenation of undissociated N2 molecules, but it is necessary to realize features present in the nitrogenase mechanism. There is the need for (i) a multi-electron and -proton simultaneous transfer, not as sequential steps, (ii) forming bridging metal hydride species, (iii) generating intermediates stabilized by bridging multiple metal atoms and (iv) the capability of the same sites to be effective both in N2 fixation and in COx reduction to C2+ products. Only iron oxide/hydroxide stabilized at defective sites of nanocarbons was found to have these features. This comparison of the molecular mechanisms in solar NH3 production and CO2 reduction is proposed to be a source of inspiration to develop the next generation electrocatalysts to address the challenging transition to future sustainable energy and chemistry beyond fossil fuels.


Asunto(s)
Amoníaco/química , Dióxido de Carbono/química , Nitrógeno/química , Sistema Solar , Amoníaco/síntesis química , Catálisis , Modelos Químicos , Modelos Moleculares , Conformación Molecular , Estructura Molecular , Nitrogenasa/química , Nitrogenasa/metabolismo , Oxidación-Reducción , Gases em Plasma
17.
Int J Mol Sci ; 22(1)2020 Dec 25.
Artículo en Inglés | MEDLINE | ID: mdl-33375728

RESUMEN

Brassinosteroids are a class of plant hormones that regulate a broad range of physiological processes such as plant growth, development and immunity, including the suppression of biotic and abiotic stresses. In this paper, we report the synthesis of new brassinosteroid analogues with a nitrogen-containing side chain and their biological activity on Arabidopis thaliana. Based on molecular docking experiments, two groups of brassinosteroid analogues were prepared with short and long side chains in order to study the impact of side chain length on plants. The derivatives with a short side chain were prepared with amide, amine and ammonium functional groups. The derivatives with a long side chain were synthesized using amide and ammonium functional groups. A total of 25 new brassinosteroid analogues were prepared. All 25 compounds were tested in an Arabidopsis root sensitivity bioassay and cytotoxicity screening. The synthesized substances showed no significant inhibitory activity compared to natural 24-epibrassinolide. In contrast, in low concentration, several compounds (8a, 8b, 8e, 16e, 22a and 22e) showed interesting growth-promoting activity. The cytotoxicity assay showed no toxicity of the prepared compounds on cancer and normal cell lines.


Asunto(s)
Brasinoesteroides/síntesis química , Brasinoesteroides/farmacología , Técnicas de Química Sintética , Nitrógeno/química , Arabidopsis/efectos de los fármacos , Arabidopsis/crecimiento & desarrollo , Brasinoesteroides/química , Estructura Molecular , Desarrollo de la Planta/efectos de los fármacos
18.
Int J Nanomedicine ; 15: 6961-6973, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-33061362

RESUMEN

Background: Although graphene quantum dots (GQDs) have received considerable research attention for their applications in various fields, the use of GQDs, such as nitrogen-doped GQDs (N-GQDs) and amino-functionalized N-GQDs (amino-N-GQDs), as photosensitizers to facilitate photodynamic therapy (PDT) has received limited research intention. To address this research gap, this study prepared novel amino-N-GQDs and investigated their properties. Methods: The amino-N-GQDs subjected to two-photon excitation (TPE) exhibited remarkable bactericidal capability in PDT. The bonding compositions of nitrogen and the amino-functionalized group played a critical role in their antimicrobial effects. Results: Compared with amino-group-free N-GQDs and amino-N-free GQDs, the amino-N-GQDs generated a higher amount of reactive oxygen species, demonstrating their superior efficacy for two-photon PDT. Additionally, the intrinsic luminescence properties and high photostability of the amino-N-GQDs demonstrate their suitability as an effective two-photon contrast agent for tracking bacteria during two-photon biomedical imaging. Conclusion: The amino-N-GQD and their remarkable properties may provide an efficient alternative approach for observing and easily eliminating malignant microbes in the future.


Asunto(s)
Antibacterianos/farmacología , Medios de Contraste/química , Nitrógeno/farmacología , Fotoquimioterapia/métodos , Puntos Cuánticos/química , Antibacterianos/química , Bacillus subtilis/efectos de los fármacos , Grafito/química , Luminiscencia , Nitrógeno/química , Fotones , Fármacos Fotosensibilizantes/química , Fármacos Fotosensibilizantes/farmacología
19.
PLoS One ; 15(9): e0239433, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32960913

RESUMEN

This work aimed at studying the photochemical treatment of a landfill leachate using ultraviolet light, hydrogen peroxide, and ferrous or ferric ions, in a batch recycle photoreactor. The effect of inorganic carbon presence, pH, initial H2O2 amount (0-9990 mg L-1) as well as Fe(II) (200-600 ppm) and Fe(III) (300-700 ppm) concentrations on the total carbon removal and color change was studied. Prior to the photochemical treatment, a pretreatment process was applied; inorganic nitrogen and inorganic carbon were removed by means of air stripping and initial pH regulation, respectively. The leachate sent subsequently for photochemical treatment was free of inorganic carbon and contained only organic carbon with concentration 1200±100 mg L-1 at pH 5.1-5.3. The most favorable concentrations of H2O2 and ferric ions for carbon removal were 6660 mg L-1 and 400 ppm, respectively. Adjusting the initial pH value in the range of 2.2-5.3 had a significant effect on the organic carbon removal. The photo-Fenton-like process was more advantageous than the photo-Fenton one for leachate treatment. By applying the most favorable operating conditions, 88.7% removal of total organic carbon, 100% removal of total inorganic carbon, 96.5% removal of total nitrogen, and 98.2% color removal were achieved.


Asunto(s)
Peróxido de Hidrógeno/química , Residuos Sólidos/análisis , Rayos Ultravioleta , Eliminación de Residuos Líquidos/métodos , Carbono/química , Color , Compuestos Férricos/química , Compuestos Ferrosos/química , Concentración de Iones de Hidrógeno , Iones/química , Hierro/química , Azul de Metileno/química , Nitrógeno/química , Oxidación-Reducción
20.
PLoS One ; 15(9): e0239706, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32976530

RESUMEN

Flash-cooling of macromolecular crystals for X-ray diffraction analysis is usually performed in liquid nitrogen (LN2). Cryogens different than LN2 are used as well for this procedure but are highly underrepresented, e.g., liquid propane and liquid ethane. These two cryogens have significantly higher cooling rates compared with LN2 and may thus be beneficial for flash-cooling of macromolecular crystals. Flash-cooling in liquid propane or liquid ethane results in sample vitrification but is accompanied by solidification of these cryogens, which is not compatible with the robotic systems nowadays used for crystal mounting at most synchrotrons. Here we provide a detailed description of a new double-chambered device and procedure to flash-cool loop mounted macromolecular crystals in different cryogenic liquids. The usage of this device may result in specimens of better crystal- and optical quality in terms of mosaic spread and ice contamination. Furthermore, applying the described procedure with the new double-chambered device provides the possibility to screen for the best flash-cooling cryogen for macromolecular crystals on a routine basis, and, most importantly, the samples obtained allow the usage of state-of-the-art robotic sample-loading systems at synchrotrons.


Asunto(s)
Frío , Cristalografía por Rayos X/instrumentación , Cristalografía por Rayos X/métodos , Etano/química , Nitrógeno/química , Propano/química
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