Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 4.209
Filtrar
1.
Phys Chem Chem Phys ; 21(40): 22224-22229, 2019 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-31576857

RESUMO

The application of co-solvents and high pressure has been reported to be an efficient means to tune the kinetics of enzyme-catalyzed reactions. Co-solvents and pressure can lead to increased reaction rates without sacrificing enzyme stability, while temperature and pH operation windows are generally very narrow. Quantitative prediction of co-solvent and pressure effects on enzymatic reactions has not been successfully addressed in the literature. Herein, we are introducing a thermodynamic approach that is based on molecular interactions in the form of activity coefficients of substrate and of enzyme in the multi-component solution. This allowed us to quantitatively predict the combined effect of co-solvent and pressure on the kinetic constants, i.e. the Michaelis constant KM and the catalytic constant kcat, of an α-CT-catalyzed peptide hydrolysis reaction. The reaction was studied in the presence of different types of co-solvents and at pressures up to 2 kbar, and quantitative predictions could be obtained for KM, kcat, and finally even primary Michaelis-Menten plots using activity coefficients provided by the thermodynamic model PC-SAFT.


Assuntos
Quimotripsina/química , Fenilalanina/análogos & derivados , Dimetil Sulfóxido/química , Hidrólise , Cinética , Metilaminas/química , Fenilalanina/química , Pressão , Solventes/química , Termodinâmica , Ureia/química , Água/química
2.
Chem Pharm Bull (Tokyo) ; 67(9): 940-944, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31474733

RESUMO

The photostability of three types of furosemide (FUR) cocrystal (FUR-caffeine, FUR-urea, and FUR-nicotinamide cocrystals) was studied under irradiation with a D65 fluorescent lamp. The coloration of the FUR-urea pellets was significantly faster than that of the intact FUR, whereas the coloration of FUR-nicotinamide was suppressed compared with that of intact FUR and the other cocrystals. In the case of FUR-urea, the chemical degradation of FUR increased by approximately 6.6% after irradiation for 90 d. On the other hand, FUR-nicotinamide showed better chemical stability, with only 1.3% of FUR degraded, which was significantly lower than the other cocrystals. The FUR-urea pellets showed a UV-Visible absorption spectrum similar to that of intact FUR, while the absorption range of FUR-nicotinamide shifted to a shorter wavelength. The light sensitivity of FUR-nicotinamide was improved because of the much lower emission of the D65 fluorescent lamp in the absorption range of the cocrystal.


Assuntos
Cafeína/química , Furosemida/química , Luz , Niacinamida/química , Ureia/química , Cristalização , Estabilidade de Medicamentos , Espectrofotometria
3.
Phys Chem Chem Phys ; 21(37): 21038-21048, 2019 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-31528920

RESUMO

Dramatically different properties have been observed for two types of osmolytes, i.e., trimethylamine N-oxide (TMAO) and urea, in a protein folding process. Great progress has been made in revealing the potential underlying mechanism of these two osmolyte systems. However, many problems still remain unsolved. In this paper, we propose to use the persistent homology to systematically study the osmolytes' molecular aggregation and their hydrogen-bonding network from a global topological perspective. It has been found that, for the first time, TMAO and urea show two extremely different topological behaviors, i.e., an extensive network and local clusters, respectively. In general, TMAO forms highly consistent large loop or circle structures in high concentrations. In contrast, urea is more tightly aggregated locally. Moreover, the resulting hydrogen-bonding networks also demonstrate distinguishable features. With a concentration increase, TMAO hydrogen-bonding networks vary greatly in their total number of loop structures and large-sized loop structures consistently increase. In contrast, urea hydrogen-bonding networks remain relatively stable with slight reduction of the total loop number. Moreover, the persistent entropy (PE) is, for the first time, used in characterization of the topological information of the aggregation and hydrogen-bonding networks. The average PE systematically increases with the concentration for both TMAO and urea, and decreases in their hydrogen-bonding networks. But their PE variances have totally different behaviors. Finally, topological features of the hydrogen-bonding networks are found to be highly consistent with those from the ion aggregation systems, indicating that our topological invariants can characterize intrinsic features of the "structure making" and "structure breaking" systems.


Assuntos
Metilaminas/química , Ureia/química , Entropia , Hidrogênio/química , Ligações de Hidrogênio , Simulação de Dinâmica Molecular , Agregação Patológica de Proteínas , Homologia Estrutural de Proteína
4.
Chem Commun (Camb) ; 55(71): 10563-10566, 2019 Aug 29.
Artigo em Inglês | MEDLINE | ID: mdl-31417990

RESUMO

Besides delivering plausible prebiotic feedstock molecules and high-energy initiators, extraterrestrial impacts could also affect the process of abiogenesis by altering the early Earth's geological environment in which primitive life was conceived. We show that iron-rich smectites formed by reprocessing of basalts due to the residual post-impact heat could catalyze the synthesis and accumulation of important prebiotic building blocks such as nucleobases, amino acids and urea.


Assuntos
Argila/química , Ferro/química , Meteoroides , Silicatos/química , Aminoácidos/química , Catálise , Terra (Planeta) , Evolução Química , Meio Ambiente Extraterreno/química , Origem da Vida , Ureia/química
5.
Phys Chem Chem Phys ; 21(35): 19469-19479, 2019 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-31461098

RESUMO

Using all-atom molecular dynamics simulations of aqueous solutions of the globular protein SNase, the dynamic behavior of water molecules and cosolvents (trimethylamine-N-oxide (TMAO) and urea) in the hydration shell of the protein was studied for different solvent compositions. TMAO is a potent protein-stabilizing osmolyte, whereas urea is known to destabilize proteins. For molecules that are initially located in successive narrow layers at a given distance from the protein, the mean displacements and the distribution of displacements for short time intervals are calculated. For molecules that are initially located in solvation shells of a given thickness around the protein, the characteristic residence times in these shells are determined to characterize the dynamic behavior of the solvent molecules as a function of the distance to the protein. A combined consideration of these characteristics allows to reveal additional features of the dynamics of the cosolvents. It is shown that TMAO molecules leave the nearest vicinity of the protein faster than urea molecules, despite the fact that the mobility of TMAO molecules, measured by their mean displacements, is lower than that of urea. Moreover, we show that the rate of release of TMAO molecules from the hydration shell is lower in ternary (TMAO + urea + H2O) solvent mixtures than in the binary ones. This is consistent with a recent observation that the fraction of TMAO near the protein decreases in the presence of urea. From the analysis of the decay of the number of particles initially located in the region of the first peak of the distribution function of solvent molecules around the protein, we estimated that about 20 water molecules and 6-7 urea molecules stay near the protein for more than 1000 ps.


Assuntos
Endodesoxirribonucleases/química , Endodesoxirribonucleases/metabolismo , Metilaminas/química , Simulação de Dinâmica Molecular , Ureia/química , Água/química , Estabilidade Proteica , Solventes/química
6.
Chem Asian J ; 14(17): 2953-2957, 2019 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-31321878

RESUMO

This paper describes the synthesis of protein microtube motors having a urease interior surface and highlights their nonbubble-propelled behavior driven by enzymatic reaction (urea→NH3 and CO2 ). The precursor microtubes were prepared by layer-by-layer assembly using a track-etched microporous polycarbonate membrane. Immobilization of a urease on the internal wall was accomplished using avidin-biotin interaction. The tubules swam smoothly in an aqueous media containing a physiological concentration of urea. Each tubule was rotating laterally while moving forward. It is remarkable that the microtubes were digested completely by proteases, demonstrating perfect biodegradability.


Assuntos
Avidina/química , Biotina/química , Urease/metabolismo , Avidina/metabolismo , Biotina/metabolismo , Enzimas Imobilizadas/química , Enzimas Imobilizadas/metabolismo , Cimento de Policarboxilato/química , Porosidade , Ureia/química , Ureia/metabolismo , Urease/química
7.
BMC Vet Res ; 15(1): 233, 2019 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-31286932

RESUMO

BACKGROUND: The increasing costs of feed has subsequently increased the costs of production of livestock, thereby decreasing the profit margin of this sector. The utilization of agro-industrial by-products has to some extent substitute some of the corn grains and soyabean meal, commonly used in animal feeds. In Malaysia, palm kernel cake (PKC) is a by-product of the oil palm industry and is frequently used to supply both crude protein (14-16% CP) and energy (11 MJ/kg) in ruminants. The energy and protein content are adequate for maintenance in the majority of ruminants. However, highly available energy supplementation is known to improve growth performance and protein deposition. This study was carried out to determine the effect on the quality of meat and fatty acid composition of the semitendinosus (ST), supraspinatus (SS), and longissimus lumborum (LL) muscles of Dorper lambs by including corn as an energy source in a basal diet of PKC urea-treated rice straw. RESULTS: The results show that the LL muscle-drip loss was greater in animals supplemented with 5% corn compared to the other groups. Higher pH values of SS and LL muscles were observed in animals supplemented with 5 and 10% corn. Furthermore, the L* value of ST muscle was increased in lambs fed on 5% corn while, reduced in those fed on 0% corn, but the a* and b* values were not significantly different in the treatment groups. The fatty acid composition of the SS muscles showed that lambs fed on 10% corn had higher levels of sum PUFA n-3 compared to those fed on 0% corn. The concentration of C18:1trans11 and CLA c12 t10 in ST muscle from the lambs fed on supplemented diets were higher than those of the controls. CONCLUSION: This study has concluded the supplementation of corn as a source of energy into a PKC urea-treated rice straw-based diet increased the PUFA concentrations of muscles as compared to control groups.


Assuntos
Fenômenos Fisiológicos da Nutrição Animal , Dieta/veterinária , Ácidos Graxos/análise , Carne/normas , Músculo Esquelético/química , Oryza/química , Zea mays/metabolismo , Ração Animal/normas , Animais , Malásia , Músculo Esquelético/metabolismo , Ovinos , Ureia/química
8.
Phys Chem Chem Phys ; 21(30): 16785-16797, 2019 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-31328193

RESUMO

The selective catalytic reduction technique for automotive applications depends on ammonia production from a urea-water solution via thermolysis and hydrolysis. In this process, undesired liquid and solid by-products are formed in the exhaust pipe. The formation and decomposition of these by-products have been studied by thermogravimetric analysis and differential scanning calorimetry. A new reaction scheme is proposed that emphasizes the role of thermodynamic equilibrium of the reactants in liquid and solid phases. Thermodynamic data for triuret have been refined. The observed phenomenon of liquefaction and re-solidification of biuret in the temperature range of 193-230 °C is explained by formation of a eutectic mixture with urea.


Assuntos
Termodinâmica , Ureia/química , Catálise , Temperatura Ambiente
9.
Chemistry ; 25(52): 12145-12158, 2019 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-31271481

RESUMO

Urease uses a cluster of two NiII ions to activate a water molecule for urea hydrolysis. The key to this unsurpassed enzyme is a change in the conformation of a flexible structural motif, the mobile flap, which must be able to move from an open to a closed conformation to stabilize the chelating interaction of urea with the NiII cluster. This conformational change brings the imidazole side chain functionality of a critical histidine residue, αHis323, in close proximity to the site that holds the transition state structure of the reaction, facilitating its evolution to the products. Herein, we describe the influence of the solution pH in modulating the conformation of the mobile flap. High-resolution crystal structures of urease inhibited in the presence of N-(n-butyl)phosphoric triamide (NBPTO) at pH 6.5 and pH 7.5 are described and compared to the analogous structure obtained at pH 7.0. The kinetics of urease in the absence and presence of NBPTO are investigated by a calorimetric assay in the pH 6.0-8.0 range. The results indicate that pH modulates the protonation state of αHis323, which was revealed to have pKa =6.6, and consequently the conformation of the mobile flap. Two additional residues (αAsp224 and αArg339) are shown to be key factors for the conformational change. The role of pH in modulating the catalysis of urea hydrolysis is clarified through the molecular and structural details of the interplay between protein conformation and solution acidity in the paradigmatic case of a metalloenzyme.


Assuntos
Níquel/química , Urease/química , Amidas/química , Catálise , Domínio Catalítico , Cátions Bivalentes , Concentração de Íons de Hidrogênio , Hidrólise , Cinética , Compostos Organofosforados/química , Conformação Proteica , Ureia/química
10.
Chem Pharm Bull (Tokyo) ; 67(7): 707-712, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31257326

RESUMO

Hypobromous acid (HOBr) is generated not only by eosinophils but also by neutrophils in the presence of Br- at the plasma concentration. Reactivity of HOBr is greatly modulated by coexistent compounds such as amines and amides. In this study, we investigated effects of urea in the reaction of nucleosides with HOBr. When nucleosides were incubated with HOBr without urea in potassium phosphate buffer at pH 7.4 and 37°C, the reactions almost completed within 10 min, with consumptions in the order of 2'-deoxyguanosine > 2'-deoxycytidine > 2'-deoxythymidine > 2'-deoxyadenosine, generating 8-bromo-2'-deoxyguanosine and 5-bromo-2'-deoxycytidine. In the presence of urea, the reaction of nucleosides with HOBr was relatively slow, continuing over several hours. When HOBr was preincubated without urea in potassium phosphate buffer at pH 7.4 and 37°C for 48 h, the preincubated HOBr solution did not react with nucleosides. However, a similar preincubated solution of HOBr with urea reacted with nucleosides to generate 8-bromo-2'-deoxyguanosine and 5-bromo-2'-deoxycytidine. These results imply that a reactive bromine compound with a long life, probably bromourea, is generated by HOBr in neutral urea solution and reacts with nucleosides, resulting in brominated nucleosides.


Assuntos
Bromatos/química , Nucleosídeos/química , Ureia/química , Cromatografia Líquida de Alta Pressão , Desoxicitidina/química , Desoxiguanosina/análogos & derivados , Desoxiguanosina/análise , Desoxiguanosina/química , Halogenação , Fosfatos/química , Compostos de Potássio/química , Espectrometria de Massas por Ionização por Electrospray , Timidina/química
11.
Phys Chem Chem Phys ; 21(24): 12806-12817, 2019 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-31165827

RESUMO

We present a study of the combined effects of natural cosolvents (TMAO, glycine, urea) and pressure on the activity of the tetrameric enzyme lactate dehydrogenase (LDH). To this end, high-pressure stopped-flow methodology in concert with fast UV/Vis spectroscopic detection of product formation was applied. To reveal possible pressure effects on the stability and dynamics of the enzyme, FTIR spectroscopic and neutron scattering measurements were carried out. In neat buffer solution, the catalytic turnover number of the enzyme, kcat, increases up to 1000 bar, the pressure range where dissociation of the tetrameric species to dimers sets in. Accordingly, we obtain a negative activation volume, ΔV# = -45.3 mL mol-1. Further, the enzyme substrate complex has a larger volume compared to the enzyme and substrate in the unbound state. The neutron scattering data show that changes in the fast internal dynamics of the enzyme are not responsible for the increase of kcat upon compression. Whereas the magnitude of kcat is similar in the presence of the osmolytes, the pressure of deactivation is modulated by the addition of cosolvents. TMAO and glycine increase the pressure of deactivation, and in accordance with the observed stabilizing effect both cosolvents exhibit against denaturation and/or dissociation of proteins. While urea does not markedly affect the magnitude of the Michaelis constant, KM, both 1 M TMAO and 1 M glycine exhibit smaller KM values of about 0.07 mM and 0.05 mM below about 1 kbar. Such positive effect on the substrate affinity could be rationalized by the effect the two cosolutes impose on the thermodynamic activities of the reactants, which reflect changes in water-mediated intermolecular interactions. Our data show that the intracellular milieu, i.e., the solution conditions that have evolved, may be sufficient to maintain enzymatic activity under extreme environmental conditions, including the whole pressure range encountered on Earth.


Assuntos
L-Lactato Desidrogenase/química , Solventes/química , Glicina/química , Cinética , Metilaminas/química , Modelos Moleculares , Pressão , Desnaturação Proteica , Dobramento de Proteína , Multimerização Proteica , Termodinâmica , Ureia/química , Água/química
12.
Chemphyschem ; 20(16): 2082-2092, 2019 08 16.
Artigo em Inglês | MEDLINE | ID: mdl-31233266

RESUMO

The studied enzyme-based biocatalytic system mimics NXOR Boolean logic gate, which is a logical operator that corresponds to equality in Boolean algebra. It gives the functional value true (1) if both functional arguments (input signals) have the same logical value (0,0 or 1,1), and false (0) if they are different (0,1 or 1,0). The output signal producing reaction is catalyzed by pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH), which is inhibited at acidic and basic pH values. Two other reactions catalyzed by esterase and urease produce acetic acid and ammonium hydroxide, respectively, shifting solution pH from the optimum pH for PQQ-GDH to acidic and basic values (1,0 and 0,1 input combinations, respectively), thus switching the enzyme activity off (output 0). When the input signals are not applied (0,0 combination) or both applied compensating each other (1,1 combination) the optimum pH is preserved, thus keeping PQQ-GDH running at the high rate (output 1). The biocatalytic cascade mimicking the NXOR gate was characterized optically and electrochemically. In the electrochemical experiments the PQQ-GDH enzyme communicated electronically with a conducting electrode support, thus resulting in the electrocatalytic current when signal combinations 0,0 and 1,1 were applied. The logic gate operation, when it was realized electrochemically, was also extended to the biomolecular release controlled by the gate. The release system included two electrodes, one performing the NXOR gate and another one activated for the release upon electrochemically stimulated alginate hydrogel dissolution. The studied system represents a general approach to the biocatalytic realization of the NXOR logic gate, which can be included in different catalytic cascades mimicking operation of concatenated gates in sophisticated logic circuitries.


Assuntos
Computadores Moleculares , Esterases/química , Glucose Desidrogenase/química , Lógica , Urease/química , Acetatos/química , Alginatos/química , Animais , Canavalia/enzimologia , Técnicas Eletroquímicas/instrumentação , Técnicas Eletroquímicas/métodos , Eletrodos , Fluoresceína-5-Isotiocianato/química , Corantes Fluorescentes/química , Concentração de Íons de Hidrogênio , Ferro/química , Nanotubos de Carbono/química , Suínos , Ureia/química
13.
J Chem Phys ; 150(21): 215103, 2019 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-31176332

RESUMO

The denaturing or stabilizing influence of a cosolvent on a protein structure is governed by a fine balance of the energetics of the excluded volume effect and the energetics of direct protein-cosolvent interactions. We have previously characterized the energetic contributions of excluded volume and direct interactions with urea for proteins and protein groups. In this work, we examine the molecular origins underlying the relatively weak temperature and urea dependences of the m-values of globular proteins. Our combined experimental and computational results collectively paint a picture in which the relative independence of protein m-values of urea concentration originates from fortuitous compensatory effects of a progressive increase in the solvent-accessible surface area of the unfolded state and a slightly higher urea binding constant of the unfolded state relative to the folded state. Other denaturing cosolvents which lack such a compensation make poor candidates for linear extrapolation model-based protein stability determination studies. The observed diminution in m-values with increasing temperature reflects, in addition to the aforementioned compensatory effects, a decrease in protein-urea binding constants with temperature in accordance with the negative sign of the binding enthalpy.


Assuntos
Proteínas/química , Temperatura Ambiente , Ureia/química , Desdobramento de Proteína , Solventes/química , Termodinâmica
14.
J Agric Food Chem ; 67(25): 6970-6977, 2019 Jun 26.
Artigo em Inglês | MEDLINE | ID: mdl-31150237

RESUMO

Huanglongbing (HLB), also known as citrus greening, is a bacterial disease that poses a devastating threat to the citrus industry worldwide. To manage this disease efficiently, we developed and characterized a ternary aqueous solution (TSOL) that contains zinc nitrate, urea, and hydrogen peroxide. We report that TSOL exhibits better antimicrobial activity than commercial bactericides for growers. X-ray fluorescence analysis demonstrates that zinc is delivered to citrus leaves, where the bacteria reside. FTIR and Raman spectroscopy, molecular dynamics simulations, and density functional theory calculations elucidate the solution structure of TSOL and reveal a water-mediated interaction between Zn2+ and H2O2, which may facilitate the generation of highly reactive hydroxyl radicals contributing to superior antimicrobial activity of TSOL. Our results not only suggest TSOL as a potent antimicrobial agent to suppress bacterial growth in HLB-infected trees, but also provide a structure-property relationship that explains the superior performance of TSOL.


Assuntos
Antibacterianos/química , Antibacterianos/farmacologia , Citrus/microbiologia , Nitratos/química , Nitratos/farmacologia , Doenças das Plantas/prevenção & controle , Rhizobiaceae/fisiologia , Compostos de Zinco/química , Compostos de Zinco/farmacologia , Peróxido de Hidrogênio/química , Peróxido de Hidrogênio/farmacologia , Doenças das Plantas/microbiologia , Folhas de Planta/microbiologia , Rhizobiaceae/efeitos dos fármacos , Espectroscopia de Infravermelho com Transformada de Fourier , Análise Espectral Raman , Relação Estrutura-Atividade , Ureia/química , Ureia/farmacologia
16.
Biophys Chem ; 251: 106175, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31128561

RESUMO

This investigation amends the analysis of isopiestic measurements of solvent thermodynamic activity by taking into account the fact that the solvent activity, traditionally expressed in mole-fraction terms, is a molal parameter because of the constraints (constant temperature and pressure) under which the measurements are made. Application of the revised procedure to published isopiestic measurements on aqueous urea solutions at 25 °C yields a dimerization constant of 0.066 molal-1, which is two-fold larger than an earlier published estimate based on an incorrect definition of the solute activity coefficient. Despite amendments to the quantitative detail, the present study confirms the existence of a large negative entropic contribution that largely counters its enthalpic counterpart arising from the hydrogen bonding responsible for dimer formation. This evidence of enthalpy-entropy compensation is entirely consistent with quantum-mechanical predictions of the adverse effect of water on urea dimerization. Changes in water structure thus contribute significantly to the energetics of urea dimerization in aqueous solution.


Assuntos
Ureia/química , Pressão Osmótica , Soluções , Termodinâmica , Água/química
17.
Biophys Chem ; 251: 106190, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31146215

RESUMO

In this review we discuss results from temperature and pressure dependent single-molecule Förster resonance energy transfer (smFRET) studies on nucleic acids in the presence of macromolecular crowders and organic osmolytes. As representative examples, we have chosen fragments of both DNAs and RNAs, i.e., a synthetic DNA hairpin, a human telomeric G-quadruplex and the microROSE RNA hairpin. To mimic the effects of intracellular components, our studies include the macromolecular crowding agent Ficoll, a copolymer of sucrose and epichlorohydrin, and the organic osmolytes trimethylamine N-oxide, urea and glycine as well as natural occurring osmolyte mixtures from deep sea organisms. Furthermore, the impact of mutations in an RNA sequence on the conformational dynamics is examined. Different from proteins, the effects of the osmolytes and crowding agents seem to strongly dependent on the structure and chemical make-up of the nucleic acid.


Assuntos
DNA/química , RNA/química , Temperatura Ambiente , Cloridrinas/química , Transferência Ressonante de Energia de Fluorescência , Glicina/química , Humanos , Metilaminas/química , Conformação de Ácido Nucleico , Pressão , Sacarose/química , Ureia/química
18.
J Colloid Interface Sci ; 551: 16-25, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31075630

RESUMO

Cu(I) doped nano-Fe3O4 were synthesized and loaded on ordered porous carbon materials using a facile co-precipitated. The synthesized catalysts were characterized by XRD, XPS, HRTEM, FESEM-EDX mapping and N2 adsorption-desorption. The results showed that the crystal unit cell of Fe3O4 was enlarged due to the implantation of small amount of Cu(I) into the Fe3O4 structure (Fe2.85Cu0.15O4). With increased Cu content, the catalyst was dominated with Cu2O and the Fe3O4 phase disappeared, the catalytic performance of Fe-Cu bimetal oxide became worse. The Cu(I)-Fe3O4/C composite was enriched with Fe(II), Fe(III) and Cu(I) sites. The prepared Cu-Fe bimetal oxide/C composite exhibited higher specific TOF and oxidation efficiency E on carbamazepine oxidation than Fe2.85Cu0.15O4 and Fe3O4. The enhanced catalytic reactivity was attributed to the synergetic effect of surface Fe and Cu species on the H2O2 activation. The dissolved metals induced catalytic reaction at pH 4.5-8.1 was ignorable. Thus, the catalytic decomposition of H2O2 by Cu-Fe3O4/C at near neutral pH was controlled by interface reactions. The CBZ in the close proximity to the interface was attacked by the generated ROS and formed urea, 2-hydroxybenzyl alcohol and other oxidative products.


Assuntos
Carbamazepina/química , Carbono/química , Cobre/química , Peróxido de Hidrogênio/química , Nanopartículas de Magnetita/química , Adsorção , Álcool Benzílico/química , Catálise , Concentração de Íons de Hidrogênio , Cinética , Oxirredução , Porosidade , Espécies Reativas de Oxigênio/química , Propriedades de Superfície , Ureia/química
19.
Eur J Med Chem ; 175: 349-356, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31096155

RESUMO

Twelve 2,3-dihydro-[1,4]-dioxino[2,3-f]quinazoline derivatives were designed and evaluated as vascular endothelial growth factor receptor 2 (VEGFR-2) inhibitors. The most half-maximal inhibitory concentration (IC50) values of them were less than 10 nM. Among these compounds, 13d displayed highly effective inhibitory activity against VEGFR-2 (IC50 = 2.4 nM) and excellent antiproliferative activities against human umbilical vein endothelial cells (HUVECs) (IC50 = 1.2 nM). When anti-tumor animal experiments were carried out in mice, the tumor almost disappeared (TGI = 133.0%) after six days of administration of 13d. Therefore, 13d was a potential and effective anticancer agent. The binding conformations were respectively compared between VEGFR-2 with 13d and leading compound lenvatinib, and shows that they have similar binding modes.


Assuntos
Inibidores da Angiogênese/farmacologia , Antineoplásicos/farmacologia , Proliferação de Células/efeitos dos fármacos , Descoberta de Drogas , Quinazolinas/farmacologia , Receptor 2 de Fatores de Crescimento do Endotélio Vascular/antagonistas & inibidores , Inibidores da Angiogênese/química , Animais , Antineoplásicos/química , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13 , Células HEK293 , Células Endoteliais da Veia Umbilical Humana , Humanos , Concentração Inibidora 50 , Camundongos , Camundongos Nus , Simulação de Acoplamento Molecular , Compostos de Fenilureia/química , Compostos de Fenilureia/farmacologia , Espectroscopia de Prótons por Ressonância Magnética , Quinazolinas/química , Quinolinas/química , Quinolinas/farmacologia , Espectrometria de Massas por Ionização por Electrospray , Ureia/química , Ensaios Antitumorais Modelo de Xenoenxerto
20.
Talanta ; 201: 143-148, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31122404

RESUMO

The current study proposes a fast one-pot microwave assisted synthesis of new carbon dots (CDs) based on glycerol and urea. The novel carbon nanoparticles (GUCDs) have been appropriately characterized and exhibited good luminescent properties with a quantum yield of about 9.8%. Interestingly, the GUCDs are able to selectively interact with tetracycline class antibiotics, which produce a decrease in the native fluorescence of the CDs. On the base of these features, a new analytical method has been developed for the determination of tetracycline. The proposed method has shown satisfactory analytical parameters, such as good linearity range -between 0.5 and 25 µM (R2 = 0.9997)- and an acceptable detection limit (165 nM). Moreover, the new method has been successfully applied for tetracycline determination in urine samples with good recoveries (94.7-103%) and precision (4.6 RSD%).


Assuntos
Carbono/química , Pontos Quânticos/química , Tetraciclina/urina , Carbono/efeitos da radiação , Fluorescência , Fluorometria/métodos , Glicerol/química , Humanos , Concentração de Íons de Hidrogênio , Limite de Detecção , Pontos Quânticos/efeitos da radiação , Raios Ultravioleta , Ureia/química
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA