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1.
Acta Crystallogr C Struct Chem ; 76(Pt 8): 746-752, 2020 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-32756037

RESUMO

A series of five binary complexes, i.e. three cocrystals and two molecular salts, using 2-chloro-4-nitrobenzoic acid as a coformer have been produced with five commonly available compounds, some of pharmaceutical relevance, namely, 2-chloro-4-nitrobenzoic acid-isonicotinamide (1/1), C7H4ClNO4·C6H6N2O, 2-chloro-4-nitrobenzoic acid-3,3-diethylpyridine-2,4(1H,3H)-dione (2/1), 2C7H4ClNO4·C9H13NO2, 2-chloro-4-nitrobenzoic acid-pyrrolidin-2-one (1/1), C7H4ClNO4·C4H7NO, 2-carboxypiperidinium 2-chloro-4-nitrobenzoate, C6H12NO2-·C7H3ClNO4-, and (2-hydroxyethyl)ammonium 2-chloro-4-nitrobenzoate, C2H8NO+·C7H3ClNO4-. The coformer falls under the classification of a `generally regarded as safe' compound. All five complexes make use of a number of different heteromeric hydrogen-bonded interactions. Intermolecular potentials were evaluated using the CSD-Materials module.


Assuntos
Clorobenzoatos/química , Sais/química , Cristalografia por Raios X , Preparações Farmacêuticas
2.
J Chromatogr A ; 1625: 461305, 2020 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-32709348

RESUMO

A novel kind of magnetic porous carbon nano-fibers (Fe3O4@P-CNFs) materials was successfully prepared and used as an adsorbent. Based on the above-mentioned adsorbent, a simple and effective magnetic disperse solid-phase extraction (MSPE) method was developed and first utilized to the enrichment and purification of five Sudan dyes (including Sudan I, Sudan II, Sudan III, Sudan IV, and Sudan Red 7B) in foodstuffs for the first time. High-performance liquid chromatography was used to determine the content of the Sudan dyes. The parameters affecting the extraction performance were studied and optimized, including the amount of the adsorbent and inorganic salt, type and the volume of the eluent, pH of the sample solution and extraction time. Under the optimized experimental conditions, the results show that the proposed method has a good linear relationship (r≥ 0.9993). The limits of detection range from 0.88 µg L-1 to 1.27 µg L-1. The recoveries range from 86.6% to 99.7% with the relative standard deviations ranging from 0.6% to 7.9% in the methodology validation. The above-mentioned results indicate that the proposed method is a sensitive and reliable procedure with good reproducibility for the detection of Sudan dyes residues in foodstuffs.


Assuntos
Compostos Azo/análise , Fibra de Carbono/química , Corantes/análise , Análise de Alimentos , Fenômenos Magnéticos , Nanofibras/química , Adsorção , Compostos Azo/química , Corantes/química , Concentração de Íons de Hidrogênio , Limite de Detecção , Nanofibras/ultraestrutura , Porosidade , Análise de Regressão , Reprodutibilidade dos Testes , Sais/química , Fatores de Tempo
3.
Nature ; 581(7807): 215-220, 2020 05.
Artigo em Inglês | MEDLINE | ID: covidwho-19579

RESUMO

A new and highly pathogenic coronavirus (severe acute respiratory syndrome coronavirus-2, SARS-CoV-2) caused an outbreak in Wuhan city, Hubei province, China, starting from December 2019 that quickly spread nationwide and to other countries around the world1-3. Here, to better understand the initial step of infection at an atomic level, we determined the crystal structure of the receptor-binding domain (RBD) of the spike protein of SARS-CoV-2 bound to the cell receptor ACE2. The overall ACE2-binding mode of the SARS-CoV-2 RBD is nearly identical to that of the SARS-CoV RBD, which also uses ACE2 as the cell receptor4. Structural analysis identified residues in the SARS-CoV-2 RBD that are essential for ACE2 binding, the majority of which either are highly conserved or share similar side chain properties with those in the SARS-CoV RBD. Such similarity in structure and sequence strongly indicate convergent evolution between the SARS-CoV-2 and SARS-CoV RBDs for improved binding to ACE2, although SARS-CoV-2 does not cluster within SARS and SARS-related coronaviruses1-3,5. The epitopes of two SARS-CoV antibodies that target the RBD are also analysed for binding to the SARS-CoV-2 RBD, providing insights into the future identification of cross-reactive antibodies.


Assuntos
Betacoronavirus/química , Peptidil Dipeptidase A/química , Peptidil Dipeptidase A/metabolismo , Receptores Virais/química , Receptores Virais/metabolismo , Glicoproteína da Espícula de Coronavírus/química , Glicoproteína da Espícula de Coronavírus/metabolismo , Sequência de Aminoácidos , Anticorpos Neutralizantes/imunologia , Betacoronavirus/metabolismo , Sítios de Ligação , Sequência Conservada , Cristalografia por Raios X , Epitopos/química , Epitopos/imunologia , Evolução Molecular , Humanos , Ligação de Hidrogênio , Modelos Moleculares , Ligação Proteica , Domínios Proteicos , Vírus da SARS/química , Sais/química , Alinhamento de Sequência , Água/análise , Água/química
4.
Food Chem ; 321: 126674, 2020 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-32244137

RESUMO

Lake deposits, plant-based ashes, filtrates and evaporites or alkaline salts are used traditionally in food preparations by local populations in Africa, Asia, South America, and Oceania. Depending on the context, traditional alkaline salts are used to reduce cooking times, improve rheological characteristics of starchy doughs, maintain the color of vegetables, improve the viscosity of sticky vegetables, and act as emulsifiers. This review highlights some of the relationships among chemical composition and physicochemical properties of traditional alkaline salts when used in solution as well as their functionalities. In addition, their potential toxicity and physiological effects are explored, which might lead to a better understanding of some previously unexplained functionalities and future trends in research, such as their impact on human health.


Assuntos
Lagos/química , Plantas/química , Sais/química , Animais , Culinária , Alimentos , Humanos , Viscosidade
5.
Food Chem ; 324: 126887, 2020 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-32339788

RESUMO

Epigenetic regulation and salt ions play essential roles in senescence control, but the underlying regulatory mechanism of senescence has not been thoroughly revealed in broccoli postharvest buds. Here, we found 200 mmol·L-1 NaCl, 400 mmol·L-1 KCl, 40 mmol·L-1 CaCl2 and 0.5 µmol·L-1 Trichostatin-A (TSA, a histone deacetylase inhibitor) delayed the bud senescence. They resulted in significantly inhibiting the malondialdehyde (MDA) content, and dramatically promoting the contents of superoxide dismutase (SOD), peroxidase (POD) and Chlorophyll. Furthermore, the expression of PHEOPHYTINASE (PPH) and NONYELLOWING (NYE1), but not SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1), were remarkably repressed by salt ions and TSA. Interestingly, HISTONE DEACETYLASE 9 (HDA9) and CATION/Ca2+ EXCHANGER 1 (CCX1) were down-regulated by NaCl, CaCl2 and TSA. Further assays demonstrated that HDA9 could not interact with CCX1 promoter. It suggested that CCX1 along with HDA9 were involved in inhibiting the senescence of broccoli buds, and regulated aging by indirect interaction.


Assuntos
Antioxidantes/metabolismo , Brassica/metabolismo , Regulação para Baixo/efeitos dos fármacos , Histona Desacetilases/metabolismo , Proteínas de Plantas/metabolismo , Sais/farmacologia , Sequência de Aminoácidos , Antiporters/química , Antiporters/genética , Antiporters/metabolismo , Brassica/química , Brassica/classificação , Cloreto de Cálcio/química , Cloreto de Cálcio/farmacologia , Clorofila/metabolismo , Flores/química , Flores/metabolismo , Ácidos Hidroxâmicos/química , Ácidos Hidroxâmicos/farmacologia , Íons/química , Filogenia , Sais/química , Alinhamento de Sequência
6.
Nature ; 581(7807): 215-220, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32225176

RESUMO

A new and highly pathogenic coronavirus (severe acute respiratory syndrome coronavirus-2, SARS-CoV-2) caused an outbreak in Wuhan city, Hubei province, China, starting from December 2019 that quickly spread nationwide and to other countries around the world1-3. Here, to better understand the initial step of infection at an atomic level, we determined the crystal structure of the receptor-binding domain (RBD) of the spike protein of SARS-CoV-2 bound to the cell receptor ACE2. The overall ACE2-binding mode of the SARS-CoV-2 RBD is nearly identical to that of the SARS-CoV RBD, which also uses ACE2 as the cell receptor4. Structural analysis identified residues in the SARS-CoV-2 RBD that are essential for ACE2 binding, the majority of which either are highly conserved or share similar side chain properties with those in the SARS-CoV RBD. Such similarity in structure and sequence strongly indicate convergent evolution between the SARS-CoV-2 and SARS-CoV RBDs for improved binding to ACE2, although SARS-CoV-2 does not cluster within SARS and SARS-related coronaviruses1-3,5. The epitopes of two SARS-CoV antibodies that target the RBD are also analysed for binding to the SARS-CoV-2 RBD, providing insights into the future identification of cross-reactive antibodies.


Assuntos
Betacoronavirus/química , Peptidil Dipeptidase A/química , Peptidil Dipeptidase A/metabolismo , Receptores Virais/química , Receptores Virais/metabolismo , Glicoproteína da Espícula de Coronavírus/química , Glicoproteína da Espícula de Coronavírus/metabolismo , Sequência de Aminoácidos , Anticorpos Neutralizantes/imunologia , Betacoronavirus/metabolismo , Sítios de Ligação , Sequência Conservada , Cristalografia por Raios X , Epitopos/química , Epitopos/imunologia , Evolução Molecular , Humanos , Ligação de Hidrogênio , Modelos Moleculares , Ligação Proteica , Domínios Proteicos , Vírus da SARS/química , Sais/química , Alinhamento de Sequência , Água/análise , Água/química
7.
J Chromatogr A ; 1621: 461083, 2020 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-32317103

RESUMO

A rapid and sensitive direct immersion solid-phase microextraction (SPME) technique for the analysis of seven chloro (Cl-) and nitro (NO2-) substituted anilines, toluenes, and nitrobenzenes from small volume (1.5 mL) aqueous samples was optimized for gas chromatography using Design of Experiments (DoE). Screening of the SPME factors was performed by a fractional factorial DoE, and the optimization of influential factors was achieved with a central composite multi-response surface DoE. Extraction time, pre-SPME agitation speed, extraction temperature, and desorption temperature were identified as significant factors and their values were set using a desirability function that maximized the extraction of the seven target analytes. Extraction time and agitation speed showed significant interactions for most analytes (α = 0.05). The relative standard deviations (RSDs) for within-day and between-day analyses were below 8%, suggesting that the method was repeatable and reproducible. The obtained limits of detection were in the low µg/L range (1-10) using a Flame Ionization Detector, far below what is needed for industrial contaminated sites (usually >1 mg/L). The optimized SPME method increased the analyte concentration up to 2-3 orders of magnitude compared with direct GC injection. The optimized SPME method was applied to two groundwater samples from a contaminated site in which the concentrations of three of the target analytes were ranged from 0.06 to 9.42 mg/L with RSDs <11%. When the concentrations of the target analytes in the sample matrix were higher than 0.5 mg/L, a competition for the SPME extraction sites was observed where analytes with higher affinity for the fiber material replaced the analytes with lower affinity. As a result, dilution of highly contaminated samples is recommended. This study provided for the first time an analytical method for the quantification of frequently co-occurring contaminants from the chloro­ and nitro- substituted aniline, toluene, and nitrobenzene families.


Assuntos
Hidrocarbonetos Aromáticos/análise , Nitrocompostos/análise , Microextração em Fase Sólida/métodos , Análise de Variância , Calibragem , Água Subterrânea/química , Limite de Detecção , Modelos Teóricos , Reprodutibilidade dos Testes , Sais/química , Temperatura , Fatores de Tempo , Poluentes Químicos da Água/análise
8.
Biochim Biophys Acta Bioenerg ; 1861(7): 148185, 2020 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-32171794

RESUMO

In the aerobic respiratory chains of many organisms, complex I functions as the first electron input. By reducing ubiquinone (Q) to ubiquinol, it catalyzes the translocation of protons across the membrane as far as ~200 Å from the site of redox reactions. Despite significant amount of structural and biochemical data, the details of redox coupled proton pumping in complex I are poorly understood. In particular, the proton transfer pathways are extremely difficult to characterize with the current structural and biochemical techniques. Here, we applied multiscale computational approaches to identify the proton transfer paths in the terminal antiporter-like subunit of complex I. Data from combined classical and quantum chemical simulations reveal for the first time structural elements that are exclusive to the subunit, and enables the enzyme to achieve coupling between the spatially separated Q redox reactions and proton pumping. By studying long time scale protonation and hydration dependent conformational dynamics of key amino acid residues, we provide novel insights into the proton pumping mechanism of complex I.


Assuntos
Antiporters/metabolismo , Complexo I de Transporte de Elétrons/metabolismo , Subunidades Proteicas/metabolismo , Força Próton-Motriz/fisiologia , Sequência de Aminoácidos , Antiporters/química , Modelos Moleculares , Conformação Proteica , Subunidades Proteicas/química , Prótons , Sais/química , Thermus thermophilus/metabolismo , Água/química
9.
Pharm Res ; 37(4): 70, 2020 Mar 16.
Artigo em Inglês | MEDLINE | ID: mdl-32185516

RESUMO

PURPOSE: While including amorphous solid dispersion (ASD) in tablet formulations is increasingly common, tablets containing high ASD loading are associated with slow disintegration, which presents a challenge to control pill burden for less potent compounds. METHODS: We use a model ASD, composed of a hydrophobic drug with copovidone and a non-ionic surfactant, to explore formulation options that can prevent slow disintegration. RESULTS: In addition to the ASD loading, the pH of the disintegration medium and the inclusion of inorganic salts in the tablet also have an impact on the tablet disintegration time. Certain kosmotropic salts, when added in the formulation, can significantly accelerate tablet disintegration, though the rank order in their effectiveness does not exactly follow the Hofmeister series at pH 1.8. The particle size and dissolution rate of the salt can contribute to its overall effectiveness. CONCLUSION: We provided a mechanistic explanation of the disintegration process: fast-dissolving kosmotropic salt results in a concentrated salt solution inside the restrained tablet matrix, thus inhibiting the dissolution of copovidone and preventing polymer gelling which is the main cause leading the slow disintegration. The outcome of this study has enabled the design of a higher ASD loading platform formulation for copovidone based ASD. Graphical Abstract MicroCT aids the mechanistic understanding of the role of inorganic salt in the tablet disintegration of amorphous solid dispersion based formulation.


Assuntos
Pirrolidinas/química , Sais/química , Comprimidos/química , Compostos de Vinila/química , Química Farmacêutica , Excipientes/química , Concentração de Íons de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Concentração Osmolar , Tamanho da Partícula , Solubilidade
10.
Macromol Rapid Commun ; 41(6): e1900644, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32022349

RESUMO

In a significant breakthrough from classical molecular (i.e., nonpolymeric) iodonium salts in light-induced photochemistry, the synthesis and use of new safer polymeric iodonium salts are reported here. They are shown to be involved in charge transfer complexes (CTCs) while in interaction with a safe amino acid derivative (N-phenylglycine). Also, this study demonstrates i) the formation of CTCs between the iodonium (acceptor) and an aryl/alkyl amine (donor) through UV-vis measurements of the monomer, ii) the formation of radicals in electron spin resonance spin trapping experiments when the CTCs are irradiated by visible light (405 nm), and iii) their efficiency as a photoinitiator to polymerize three different acrylic monomers under LED irradiation at 405 nm under air and their application to 3D resolved laser writing of thick samples (3 mm). High reactivity for polymeric iodonium salts comparable with molecular ones is exhibited with the advantage of potential lower migration. To the best of the authors' knowledge, this is the first reported instance of polymeric iodonium salts acting as polymerization initiators.


Assuntos
Radicais Livres/química , Compostos de Iodo/química , Polimerização/efeitos da radiação , Polímeros/química , Sais/química , Glicina/análogos & derivados , Glicina/química , Luz , Processos Fotoquímicos , Polietilenoglicóis/química , Polímeros/síntese química , Ácidos Polimetacrílicos/química , Poliestirenos/química
11.
J Photochem Photobiol B ; 204: 111800, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32028188

RESUMO

Herein, we have reported the synthesis, characterization and catalytic activity of highly stable gold nanoparticles (Au NPs) using red cabbage extract (RCE) under UV irradiation. The anthocyanin groups predominantly existing in RCE play an essential role for biosynthesis of stable Au NPs. The reasons for using anthocyanins: 1) they act as chelating agents for preferentially reacting with gold ions (Au3+) to form Au3+- anthocyanin complexes, 2) as light-active reductants for reduction of Au3+ to zero valent Au0 under UV irradiation and 3) as stabilizing agent for preventing Au NPs from aggregation in high salt concentration owing to their unique salt tolerance property. We also demonstrate that how reaction time, concentration of RCE, pH value of reaction solutions and using one more reducing agent affected formation of the Au NPs. The stability of RCE Au NPs was comparatively studied with commercial (citrate stabilized) Au NPs against 100 mM salt (NaCl) solution. The RCE-Au NP showed reduction ability for conversion of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). UV-vis spectrometry, transmission electron microscopy (TEM), dynamic light scattering (DLS) and zeta potential (ZT) methods were utilized to characterize the Au NPs. We demonstrated that how whole RCE (anthocyanins molecules are major component) can be used as photo-active reducing and stabilizing agents to form Au NPs in a short time under UV irradiation and strong reducing agent without additional agents.


Assuntos
Brassica/química , Ouro/química , Nanopartículas Metálicas/química , Raios Ultravioleta , Antocianinas/química , Brassica/metabolismo , Catálise , Química Verde , Nitrofenóis/química , Oxirredução , Extratos Vegetais/química , Sais/química
12.
Chem Commun (Camb) ; 56(20): 3081-3084, 2020 Mar 10.
Artigo em Inglês | MEDLINE | ID: mdl-32051996

RESUMO

Surface CIEE based on Zn-HDS as host material and GSH-CuNCs as guest molecules was developed to produce fluorescence composite GSH-CuNCs/Zn-HDS for the first time. It displays high quantum yield, long fluorescence lifetime and good stability, and was applied to sensitive bioenzyme sensing and fabrication of a high performance light-emitting diode.


Assuntos
Cobre/química , Enzimas/análise , Corantes Fluorescentes/química , Luz , Nanopartículas Metálicas/química , Zinco/química , Enzimas/metabolismo , Glutationa/química , Tamanho da Partícula , Sais/química , Propriedades de Superfície
13.
Artigo em Inglês | MEDLINE | ID: mdl-32014662

RESUMO

A hybrid mode of hydrophobic interaction chromatography (HHIC) is an emerging analytical technique for the separation of biomolecules under non-denaturing conditions that combines elements of conventional hydrophobic interaction and reversed-phase chromatography. This article explores the impact of mobile phase composition such as salt concentration and organic modifier on the separation of therapeutic monoclonal antibodies and related large biomolecules using poly (alkyl aspartamide) silica HIC columns. The initial mobile phase salt concentration had a significant impact on the separation of a mixture of large biomolecules demonstrating that the relationship of elution and salt concentration was more complex than in conventional HIC. In general, the earlier eluting components exhibited greater retention at higher salt concentration as is typical of HIC separations. Conversely, the later eluting components showed greater retention at lower initial salt concentration. This differential is useful for improving the overall separation by widening the elution window for components of a mixture. In addition, no significant unfolding of the proteins was detected by intrinsic fluorescence or electrospray mass spectrometry. The impact of linear velocity and gradient steepness was also evaluated.


Assuntos
Anticorpos Monoclonais/química , Dióxido de Silício/química , Cromatografia Líquida de Alta Pressão , Interações Hidrofóbicas e Hidrofílicas , Sais/química , Solventes/química
14.
Food Chem ; 317: 126424, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32088405

RESUMO

In this study, a simple, efficient, and green effervescence tablet-assisted microextraction method based on the solidification of deep eutectic solvent (ETA-ME-SDES) was developed to determine picoxystrobin, pyraclostrobin, and trifloxystrobin in water, juice, wine, and vinegar samples by HPLC. An eco-friendly, hydrophobic, deep eutectic solvent (DES, acting as the extraction solvent) was synthesized by thymol and octanoic acid in the molar ratio of 1:5. The extraction solvent dispersed in sample solutions with the assistance of pH adjustment and effervescence reaction, and was collected after solidification in an ice bath. Several essential conditions, including the type and the volume of DESs, the amount of ammonia hydroxide, and the components of effervescence tablets were optimized. The limits of detection ranged from 0.15 to 0.38 µg L-1. Extraction recovery ranged from 77.4 to 106.9%. The proposed method was successful in determining the amount of strobilurin fungicides in water, juice, wine, and vinegar samples.


Assuntos
Ácido Acético/análise , Cromatografia Líquida de Alta Pressão , Sucos de Frutas e Vegetais/análise , Fungicidas Industriais/análise , Estrobilurinas/análise , Poluentes Químicos da Água/análise , Vinho/análise , Acetatos/análise , Fungicidas Industriais/química , Concentração de Íons de Hidrogênio , Iminas/análise , Limite de Detecção , Microextração em Fase Líquida/métodos , Sais/química , Estrobilurinas/química , Poluentes Químicos da Água/química
15.
Pharm Res ; 37(3): 42, 2020 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-31989335

RESUMO

PURPOSE: The design of biorelevant conditions for in vitro evaluation of orally administered drug products is contingent on obtaining accurate values for physiologically relevant parameters such as pH, buffer capacity and bile salt concentrations in upper gastrointestinal fluids. METHODS: The impact of sample handling on the measurement of pH and buffer capacity of aspirates from the upper gastrointestinal tract was evaluated, with a focus on centrifugation and freeze-thaw cycling as factors that can influence results. Since bicarbonate is a key buffer system in the fasted state and is used to represent conditions in the upper intestine in vitro, variations on sample handling were also investigated for bicarbonate-based buffers prepared in the laboratory. RESULTS: Centrifugation and freezing significantly increase pH and decrease buffer capacity in samples obtained by aspiration from the upper gastrointestinal tract in the fasted state and in bicarbonate buffers prepared in vitro. Comparison of data suggested that the buffer system in the small intestine does not derive exclusively from bicarbonates. CONCLUSIONS: Measurement of both pH and buffer capacity immediately after aspiration are strongly recommended as "best practice" and should be adopted as the standard procedure for measuring pH and buffer capacity in aspirates from the gastrointestinal tract. Only data obtained in this way provide a valid basis for setting the physiological parameters in physiologically based pharmacokinetic models.


Assuntos
Bicarbonatos/química , Ácidos e Sais Biliares/química , Líquidos Corporais/química , Líquidos Corporais/metabolismo , Trato Gastrointestinal Superior/química , Trato Gastrointestinal Superior/metabolismo , Tampões (Química) , Famotidina/administração & dosagem , Famotidina/metabolismo , Absorção Gastrointestinal , Humanos , Concentração de Íons de Hidrogênio , Ibuprofeno/administração & dosagem , Ibuprofeno/metabolismo , Intestino Delgado , Sais/química , Estômago
16.
J Appl Microbiol ; 128(6): 1678-1693, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31997433

RESUMO

AIMS: Differences in the bacterial population of cucumber fermentations brined with no salt, 100 mmol l-1 (1·1%) calcium chloride (CaCl2 ) or 1·03 mol l-1 (6%) sodium chloride (NaCl) were studied. METHODS AND RESULTS: Changes in the microbiology and chemistry of commercial and laboratory scale cucumber fermentations occurring as a function of time were monitored using colony counts and metagenetic analysis, and a pH probe and high-performance liquid chromatography analysis respectively. Dissolved oxygen and carbon dioxide content were monitored in commercial fermentations. Fermentations brined with calcium chloride (CaCl2 ) or no salt sustained faster microbial growth and reduction in pH than those brined with 1·03 mol l-1 NaCl. Leuconostoc, Lactococcus and Weissella dominated in fermentations brined with no salt or 100 mmol l-1 CaCl2 on day 1 as compared to Weissella and enterobacteria in fermentations containing 1·03 mol l-1 NaCl. Lactobacilli dominated all fermentations by the third day, regardless of salt type, and was followed, in relative abundance by Pediococcus, Leuconostoc, Lactococcus and Weissella. From 84 to 96% of the population was composed of Lactobacillus by day 7 of the fermentations, except in the no salt fermentations in which a mixed population of LAB remained. The population of LAB found in commercial cucumber fermentations brined with 100 mmol l-1 CaCl2 (n = 18) or 1·03 mol l-1 NaCl (n = 9) mimicked that of laboratory fermentations. A declining population of aerobes was detected in commercial fermentations brined with CaCl2 on day 1. CONCLUSION: A reduced NaCl content in cucumber fermentation enhances microbial diversity. SIGNIFICANCE AND IMPACT OF THE STUDY: This study fills a knowledge gap and aids in the design of improved reduced NaCl cucumber fermentations.


Assuntos
Bactérias/isolamento & purificação , Cucumis sativus , Alimentos e Bebidas Fermentados/microbiologia , Microbiota , Sais/química , Bactérias/classificação , Bactérias/genética , Bactérias/crescimento & desenvolvimento , Cloreto de Cálcio/análise , Cucumis sativus/microbiologia , Fermentação , Microbiologia de Alimentos , Concentração de Íons de Hidrogênio , Cloreto de Sódio/análise
17.
Phys Chem Chem Phys ; 22(4): 2142-2156, 2020 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-31912070

RESUMO

There are several important phenomena in chemistry, biology, and physics where molecules (or parts of a molecule) having charges of the same sign come closer together and become stable. DNA condensation, RNA folding, colloid-colloid interactions are some of the examples of this kind. In the current work, we have investigated how ß-lactoglobulin, a protein found in milk, in spite of carrying +13 charge, favors the homodimer formation in the presence of salt. We have focussed on calculating the protein-protein binding free energy in the presence of salt and identifying the thermodynamic and microscopic mechanism of the process. Estimation of binding free energy of this salt-dependent process is done by combining molecular dynamics simulation with statistical mechanical theory of three-dimensional reference interaction site model (3D-RISM). Binding free energy is evaluated from the chemical potential of the solutes as opposed to potential of mean force calculation, which gives only a constrained free energy. Our calculated values semi-quantitatively match with the experimental results. By examining the different components of binding free energy, we have found that the role of salt ions (especially of Cl-) is to shift the equilibrium towards the dimer. Non-polar (Lennard-Jones) interactions between the monomers is also favorable to the binding free energy. However, water slightly disfavors the dimer formation. For the microscopic mechanism, heterogeneous of both Na+ and Cl- near the charged residues at the binding interface and change of this charge distribution on dimer formation contribute to the stability. A fine-tuning of enthalpic and entropic effects of salt ions is found to operate at different salt concentrations. Both thermodynamic and microscopic mechanism of dimer formation gives detailed insight into the complex electrostatics of charged protein-protein binding.


Assuntos
Lactoglobulinas/química , Modelos Moleculares , Simulação de Dinâmica Molecular , Sais/química , Dimerização , Lactoglobulinas/metabolismo , Ligação Proteica , Estrutura Terciária de Proteína
18.
Biosensors (Basel) ; 10(1)2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31952195

RESUMO

This review is divided into two parts; the first one summarizes the main features of surface modification by diazonium salts with a focus on most recent advances, while the second part deals with diazonium-based biosensors including small molecules of biological interest, proteins, and nucleic acids.


Assuntos
Técnicas Biossensoriais , Compostos de Diazônio/química , Animais , Humanos , Sais/química , Propriedades de Superfície
19.
J Chromatogr A ; 1609: 460446, 2020 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-31420178

RESUMO

Two new copolymer-grafted silica stationary phases were prepared and employed in hydrophilic interaction chromatography (HILIC). 2-(Dimethylamino)ethyl methacrylate (DMAEMA) are copolymerized with itaconic acid (IA) and acrylic acid (AA) respectively, via thiol-ene click reaction on silica surface with deep eutectic solvents (DES) as new solvents. The obtained poly(DMAEMA-co-itaconic acid)-grafted silica (Sil-PDM-PIA) and poly(DMAEMA-co-acrylic acid)-grafted silica (Sil-PDM-PAA) were characterized by Fourier transform infrared spectroscopy, elemental analysis and solid-state 13C NMR spectra. Their hydrophilic interaction performances were evaluated by separating nucleosides, nucleobases, saccharides, and amino acids. Compared with previous reported poly(itaconic acid)-grafted silica (Sil-PIA) and poly(acrylic acid)-grafted silica (Sil-PAA) stationary phases, these two new copolymer-grafted silica performed higher selectivity and better separation for polar analytes in HILIC.


Assuntos
Cromatografia/métodos , Química Click/métodos , Interações Hidrofóbicas e Hidrofílicas , Polímeros/química , Dióxido de Silício/química , Solventes/química , Compostos de Sulfidrila/química , Acetonitrilos/química , Aminoácidos/isolamento & purificação , Entropia , Concentração de Íons de Hidrogênio , Espectroscopia de Ressonância Magnética , Metacrilatos/química , Nucleosídeos/isolamento & purificação , Nylons/química , Reprodutibilidade dos Testes , Sais/química , Espectroscopia de Infravermelho com Transformada de Fourier , Succinatos/química , Temperatura
20.
Environ Sci Pollut Res Int ; 27(2): 1956-1968, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31768960

RESUMO

Membrane separation processes are being currently applied to produce drinking water from water contaminated with nitrate. The overall process generates a brine with high nitrate/nitrite concentration that is usually send back to a conventional wastewater treatment plant. Catalytic processes to nitrate reduction are being studied, but the main goal of achieving a high selectivity to nitrogen production is still a matter of research. In this work, a two-step process was evaluated, aiming to verify the best combination of operational parameters to efficiently reduce nitrate to nitrogen. In the first step, the nitrate was reduced to nitrite by electroreduction, applying a copper electrode and different cell potentials. A second step of the process was carried out by reducing the generated nitrite with a catalytic process by hydrogenation. The results showed that the highest nitrate reduction (89%) occurred when a cell potential of 11 V was applied. In this condition, the nitrite ion was generated with all experimental conditions evaluated. Then, to reduce the nitrite ion formed by catalytic reduction, activated carbon fibers (ACF) and powder γ-alumina (γ-Al2O3) were tested as supports for palladium (Pd). With both catalysts, the total nitrite conversion was obtained, being the selectivity to gaseous compounds 94% and 97% for Pd/Al2O3 and Pd/ACF, respectively. Considering the results obtained, a two-stage treatment setup to brine denitrification may be proposed. With electrochemistry, an operating condition was achieved in which ammonium production can be controlled to very low values, but the reduction is predominant to nitrite. With the second step, all nitrite is converted to nitrogen gas and just 3% of ammonium is produced with the most selective catalyst. The main novelty of this work is associated to the use of a two-stage process enabling 89% of nitrate reduction and 100% of nitrite reduction.


Assuntos
Desnitrificação , Nitratos/química , Nitritos/química , Sais/química , Catálise , Nitrogênio , Oxirredução
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