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1.
PLoS One ; 15(11): e0240634, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33176336

RESUMO

Bismuth(III) oxide is included as a radio-opacifier in dental materials, including hydraulic silicate cements, the material of choice for several endodontic procedures. It has been implicated in tooth discoloration after contact with endodontic irrigants, in particular NaOCl solution, To date, there has been no work on the chemistry: all reports have been of clinical findings only. The purpose now was to report the reactions leading to colour change from Bi2O3 in contact with solutions used in routine endodontic practice. Ten-gram portions of Bi2O3 were immersed in either water, NaOH, NaCl, NaOCl or HCl solution, either in the dark or exposed to visible light, and samples retrieved at 1, 4, 12 and 24 weeks. After washing, these were exposed to either added CO2 or not, for 1 week while drying, and under the same dark or light conditions. Changes in appearance were monitored by photography and colour measurement, and chemically by X-ray diffraction and Fourier-transform infrared spectroscopy. 24-week material was studied using electron paramagnetic resonance and Raman spectroscopy; NaOCl-treated material was also examined by scanning electron microscopy. With water, NaCl and NaOH, bismuth subcarbonate was formed. With or without added carbon dioxide, discoloration occurred from pale yellow to light brown when exposed to light, and to a lesser extent in the dark, intensifying with time. In contrast, exposure to NaOCl rapidly formed a dark brown-black sodium bismuthate. With HCl, white BiOCl was formed. Bi2O3 is not at all inert in this context as is commonly believed, denying its principle of use. Previously unreported solution-mediated reaction occurs readily even in water and NaCl solution, forming new compounds that discolour. In contact with NaOCl sodium bismuthate is formed; severe darkening occurs rapidly. The reactivity is such that Bi2O3 is not indicated for dental materials and should be withdrawn from use.


Assuntos
Bismuto/química , Materiais Dentários/química , Soluções/química , Cor , Humanos , Ácido Clorídrico/química , Luz , Cloreto de Sódio/química , Hidróxido de Sódio/química , Hipoclorito de Sódio/química , Espectroscopia de Infravermelho com Transformada de Fourier , Difração de Raios X
2.
Phys Chem Chem Phys ; 22(46): 26764-26775, 2020 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-33206736

RESUMO

All atom molecular dynamic modeling was applied in order to determine water molecule and electrolyte ion concentration profiles around and inside the myoglobin molecule at various pH values. Significant penetration of counter ions into the molecule was confirmed. The electric potential distribution within and outside the molecule was quantitatively described using the non-linear Poisson-Boltzmann (PB) approach. Using this model, calculations were performed, yielding the surface and zeta potential for various physicochemical parameters, comprising pH, the electric permittivity, the ion penetration depth and the protein volume fraction (crowding effect). The theoretical results were used for the interpretation of experimental data acquired under different ionic strengths and temperatures by electrophoretic mobility measurements. It is confirmed that the experimental data are adequately reflected for acidic pH values by the non-linear PB model where the nominal molecule charge was calculated from the H++ model. The deviations occurring for larger pH values were accounted for by considering additional non-electrostatic interactions stemming from the van der Waals and ion-induced dipole forces. In this way, it is both experimentally and theoretically confirmed that the effective charge of the myoglobin molecule in electrolyte solutions is considerably smaller than the nominal, structure-based, predicted charge. As a result, under physiological conditions prevailing, e.g. in skeletal muscles, the effective charge of the myoglobin molecule should practically vanish. One can expect that the approach developed in this work can be applied for predicting charging mechanisms of other protein molecules characterized by an analogous charge vs. pH characteristic, e.g., the SARS-CoV-2 virus spike proteins, and for soft particles with pH responsive characteristics.


Assuntos
Eletrólitos/química , Mioglobina/química , Animais , Cavalos , Concentração de Íons de Hidrogênio , Modelos Químicos , Simulação de Dinâmica Molecular , Concentração Osmolar , Soluções/química , Eletricidade Estática
3.
J Chromatogr A ; 1633: 461630, 2020 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-33128971

RESUMO

Industrial separation technologies can be improved and greatly simplified by using the methods of counter-current chromatography (CCC). We have previously proposed the use of currently available solvent extraction equipment (a series of multistage columns, a cascade of centrifugal mixer-settler extractors) as large-scale CCC devices. For industrial separations, the application of closed-loop recycling counter-current chromatography (CLR CCC) methods seems to be the most promising. To improve the performance of the CLR CCC separations, semi-continuous three-stage processes (1 - continuous loading of the mixture solution over a definite time; 2 - separation of solutes in recycling closed-loop; 3 - elution of the fractions of the separated solutes with the mobile phase) can be used. The purpose of this study is to present a simple and easy to use mathematical model allowing the simulation and design of various options for implementing such separation processes and analyze the influence of its main parameters on separation efficiency.


Assuntos
Técnicas de Química Analítica/métodos , Distribuição Contracorrente , Indústrias/métodos , Modelos Teóricos , Técnicas de Química Analítica/instrumentação , Indústrias/instrumentação , Soluções/química
4.
Chemosphere ; 259: 127510, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32650172

RESUMO

Intensive application of biochar requires better understanding of their environmental behaviors such as stability, fate, and mobility. The release of bulk biochar into biochar nanoparticles (NPs) may bring risks because of their potential flowing into downstream water bodies with nutrients/containments attached. Low-temperature pyrolyzed biochars, namely fruit tree branch biochar of 350/450/550 °C (FB350, FB450 and FB550), corn straw biochar of 350 °C (CB350) and peanut straw biochar of 350 °C (PB350), were produced, and their NPs were extracted. The yield, elemental composition, mineral composition, surface functional groups and zeta potential of biochar NPs were characterized. Subsequently their suspension stability was evaluated in NaCl and CaCl2 solutions by dynamic light scattering technique. The Hamaker constants and particle interaction energy of the biochar NPs were calculated by adopting Derjaguin-Landau-Verwey-Overbeek theory. For biochar NPs of same feedstock, the stability of FB350/450/550-NPs could be predicted well by their zeta potential values. The types of their surface functional groups were the same while their adsorption intensity differed. The scenarios for biochar NPs of different feedstock sources were different, that is, inconsistent variation was observed between their zeta potential and suspension stability, which were rooted in the variable type and quantity of surface functional groups. In conclusion, feedstock was the most significant factor that influenced the suspension stability of biochar NPs, followed by the pyrolysis temperature and solution chemistry, which were highly dependent on surface potential. The findings provide references for the environmental risk evaluation of biochar NPs and reasonable application of biochar in field.


Assuntos
Carvão Vegetal/química , Nanopartículas/química , Temperatura , Adsorção , Difusão Dinâmica da Luz , Pirólise , Soluções/química , Propriedades de Superfície , Suspensões/química
5.
Food Chem ; 333: 127460, 2020 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-32673953

RESUMO

Arbutus unedo L. (strawberry tree) has showed considerable content in phenolic compounds, especially flavan-3-ols (catechin, gallocatechin, among others). The interest of flavan-3-ols has increased due their bioactive actions, namely antioxidant and antimicrobial activities, and by association of their consumption to diverse health benefits including the prevention of obesity, cardiovascular diseases or cancer. These compounds, mainly catechin, have been showed potential for use as natural preservative in foodstuffs; however, their degradation is increased by pH and temperature of processing and storage, which can limit their use by food industry. To model the degradation kinetics of these compounds under different conditions of storage, three kinds of machine learning models were developed: i) random forest, ii) support vector machine and iii) artificial neural network. The selected models can be used to track the kinetics of the different compounds and properties under study without the prior knowledge requirement of the reaction system.


Assuntos
Ericaceae/química , Conservantes de Alimentos/química , Aprendizado de Máquina , Extratos Vegetais/química , Antioxidantes/química , Catequina/análise , Catequina/química , Flavonoides/análise , Flavonoides/química , Armazenamento de Alimentos , Frutas/química , Concentração de Íons de Hidrogênio , Cinética , Redes Neurais de Computação , Pós/análise , Pós/química , Soluções/química , Máquina de Vetores de Suporte , Temperatura
6.
Sci Rep ; 10(1): 9685, 2020 06 16.
Artigo em Inglês | MEDLINE | ID: mdl-32546801

RESUMO

It has long been observed that trimethylamine N-oxide (TMAO) and urea demonstrate dramatically different properties in a protein folding process. Even with the enormous theoretical and experimental research work on these two osmolytes, various aspects of their underlying mechanisms still remain largely elusive. In this paper, we propose to use the weighted persistent homology to systematically study the osmolytes molecular aggregation and their hydrogen-bonding network from a local topological perspective. We consider two weighted models, i.e., localized persistent homology (LPH) and interactive persistent homology (IPH). Boltzmann persistent entropy (BPE) is proposed to quantitatively characterize the topological features from LPH and IPH, together with persistent Betti number (PBN). More specifically, from the localized persistent homology models, we have found that TMAO and urea have very different local topology. TMAO is found to exhibit a local network structure. With the concentration increase, the circle elements in these networks show a clear increase in their total numbers and a decrease in their relative sizes. In contrast, urea shows two types of local topological patterns, i.e., local clusters around 6 Å and a few global circle elements at around 12 Å. From the interactive persistent homology models, it has been found that our persistent radial distribution function (PRDF) from the global-scale IPH has same physical properties as the traditional radial distribution function. Moreover, PRDFs from the local-scale IPH can also be generated and used to characterize the local interaction information. Other than the clear difference of the first peak value of PRDFs at filtration size 4 Å, TMAO and urea also shows very different behaviors at the second peak region from filtration size 5 Å to 10 Å. These differences are also reflected in the PBNs and BPEs of the local-scale IPH. These localized topological information has never been revealed before. Since graphs can be transferred into simplicial complexes by the clique complex, our weighted persistent homology models can be used in the analysis of various networks and graphs from any molecular structures and aggregation systems.


Assuntos
Ligação de Hidrogênio , Estrutura Molecular , Soluções/química , Entropia , Metilaminas/química , Modelos Químicos , Simulação de Dinâmica Molecular , Dobramento de Proteína , Ureia/química
7.
Biochem Pharmacol ; 181: 114082, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-32524995

RESUMO

The role of voltage-gated sodium (NaV) channels in pain perception is indisputable. Of particular interest as targets for the development of pain therapeutics are the tetrodotoxin-resistant isoforms NaV1.8 and NaV1.9, based on animal as well as human genetic studies linking these ion channel subtypes to the pathogenesis of pain. However, only a limited number of inhibitors selectively targeting these channels have been reported. HSTX-I is a peptide toxin identified from saliva of the leech Haemadipsa sylvestris. The native 23-residue peptide, stabilised by two disulfide bonds, has been reported to inhibit rat NaV1.8 and mouse NaV1.9 with low micromolar activity, and may therefore represent a scaffold for development of novel modulators with activity at human tetrodotoxin-resistant NaV isoforms. We synthetically produced this hydrophobic peptide in high yield using a one-pot oxidation and single step purification and determined the three-dimensional solution structure of HSTX-I using NMR solution spectroscopy. However, in our hands, the synthetic HSTX-I displayed only very modest activity at human NaV1.8 and NaV1.9, and lacked analgesic efficacy in a murine model of inflammatory pain.


Assuntos
Espectroscopia de Ressonância Magnética/métodos , Peptídeos/farmacologia , Bloqueadores dos Canais de Sódio/farmacologia , Toxinas Biológicas/farmacologia , Canais de Sódio Disparados por Voltagem/metabolismo , Sequência de Aminoácidos , Analgésicos/química , Analgésicos/farmacologia , Animais , Células Cultivadas , Humanos , Hiperalgesia/prevenção & controle , Sanguessugas/química , Sanguessugas/metabolismo , Camundongos Endogâmicos C57BL , Camundongos Knockout , Neurônios/citologia , Neurônios/efeitos dos fármacos , Neurônios/fisiologia , Técnicas de Patch-Clamp , Peptídeos/química , Ratos Sprague-Dawley , Bloqueadores dos Canais de Sódio/química , Soluções/química , Toxinas Biológicas/química , Canais de Sódio Disparados por Voltagem/genética
8.
Pharm Res ; 37(6): 93, 2020 May 11.
Artigo em Inglês | MEDLINE | ID: mdl-32394114

RESUMO

PURPOSE: Here, first experiences with a prototype tool for high throughput (passive) permeability profiling, a 96-well plate comprising the Permeapad® membrane, are reported. The permeabilities of a set of drugs were determined and compared to published measures of oral absorption, such as human fraction absorbed (Fa) and in vitro permeability values obtained using other tools. METHODS: The tool consists of a 96-well bottom and screen plate with the artificial, phospholipid-based barrier (Permeapad®) mounted between the plates' lower and upper compartments. The permeability of 14 model compounds including high- and low-absorption drugs, cationic, anionic, zwitterionic and neutral molecules, was determined by quantifying the compounds' transport over time, deriving the steady-state flux from the linear part of the cumulative curves and calculating the apparent permeability (Papp). The membrane structure was investigated in a high-resolution digital light microscope. RESULTS: The Permeapad® 96-well plate was found suited to distinguish high and low absorption drugs and yielded a hyperbolic correlation to Fa. The Papp values obtained were congruent with those determined with in-house prepared Permeapad® in the Franz cell set-up. Furthermore, good to excellent correlations were seen with Caco-2 permeability (R2 = 0.70) and PAMPA permeability (R2 = 0.89). Microscopic investigation of the Permeapad® barrier revealed the formation of phospholipid vesicles and myelin figures in aqueous environment. CONCLUSION: The Permeapad® 96-well plate permeation set-up is a promising new tool for rapid and reproducible passive permeability profiling.


Assuntos
Portadores de Fármacos/química , Ensaios de Triagem em Larga Escala/métodos , Preparações Farmacêuticas/metabolismo , Fosfolipídeos/química , Células CACO-2 , Humanos , Membranas Artificiais , Modelos Biológicos , Modelos Químicos , Estrutura Molecular , Permeabilidade , Polivinil/química , Soluções/química , Relação Estrutura-Atividade
9.
Food Chem ; 326: 126981, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32416420

RESUMO

Water activity is a physical property measured in the food industry which helps predict shelf life and microbial activity. Honey normally has a water activity less than 0.6, but this can vary with the amount of crystallization in solution. The aim of this work was to obtain relationships, as fundamental as possible, that can be used to predict the water activity of solutions with compositions similar to honey. Water activity measurements of aqueous sucrose solutions have been well analysed in literature using hydration theory. The analysis based on hydration numbers was easily able to show the quality of data previously published, and hence relationships were proposed for the hydration numbers of glucose, fructose, maltose and glycerol. A model was proposed in this study, to predict the water activity of food systems containing high concentrations of sugars and some electrolytes. The model was analysed and validated using mostly literature data supplemented with new experimental data.


Assuntos
Mel/análise , Soluções/química , Açúcares/química , Água/química , Cristalização , Eletrólitos/química , Glucose/química , Maltose/química , Modelos Teóricos , Sacarose/química
10.
Yakugaku Zasshi ; 140(4): 577-584, 2020.
Artigo em Japonês | MEDLINE | ID: mdl-32238640

RESUMO

Elneopa NF No. 1 and No. 2 infusions are complete parenteral nutrition solutions packaged as four-chambered bags. They have been used for home parenteral nutrition, with insulin injected into the bags for patients whose blood glucose becomes elevated. In this study, the stability of insulin in No. 1 and No. 2 bags was investigated. The quantity of insulin in Elneopa NF No. 2 was significantly lower than that in Elneopa NF No. 1. When insulin was injected into the upper chamber of either product, decreases in insulin levels were not observed. In contrast, the levels of insulin injected into the lower chamber of both products significantly decreased, with a larger difference in Elneopa NF No. 2. As the amino acid content is different between No. 1 and No. 2, amino acids may be considered a potential cause for the degradation of insulin in the bags. In addition, decreases in insulin levels were observed as the solutions passed through infusion sets just after flushing began, with both Elneopa NF No. 1 and No. 2. In conclusion, the concentration of insulin injected into the Elneopa infusion bags decreases, especially in No. 2 bags, and insulin is absorbed by the infusion sets.


Assuntos
Estabilidade de Medicamentos , Insulina/análise , Nutrição Parenteral Total , Soluções/química , Embalagem de Medicamentos , Insulina/administração & dosagem
11.
Langmuir ; 36(16): 4405-4415, 2020 04 28.
Artigo em Inglês | MEDLINE | ID: mdl-32243164

RESUMO

This paper presents sols of uncoated and citric acid-coated Fe3O4 nanoparticles obtained by a combination of coprecipitation and sonochemistry methods. A stable concentrated CA-Fe3O4 sol synthesized by a combination of coprecipitation with an inconvenient Fe2+/Fe3+ ratio, modification with citric acid and US treatment was obtained for the first time. A comparative analysis of the composition and morphology of nanoparticles was performed. The sols are oppositely charged and behave as a typical ferrofluid. The citric acid-modified sol is aggregatively stable over wider ranges of pH and electrolyte concentration, but it becomes less stable with the temperature increase. DLVO calculations showed that steric repulsion forces are a vital factor contributing to increased aggregative stability in a modified Fe3O4 sol. The experiments have revealed the magneto-optical effect in a modified Fe3O4 sol with an electrolyte concentration of 0.025-0.075 M caused by a high potential barrier and a deep secondary minimum in pairwise interaction curves. The "pK spectroscopy" mathematical model to describe the potentiometric curves of synthesized magnetite sols was used for the first time. According to potentiometric titration, the ions of the electrolyte practically do not contribute to formation of a surface charge in modified Fe3O4 with a change in pH due to blocking the magnetite surface by citric acid molecules. Drosophila melanogaster was used as a model to show that Fe3O4 in chronic exposure has a low toxic effect.


Assuntos
Drosophila melanogaster/efeitos dos fármacos , Longevidade/efeitos dos fármacos , Nanopartículas de Magnetita/química , Soluções/química , Animais , Ácido Cítrico/química , Ácido Cítrico/toxicidade , Feminino , Fenômenos Magnéticos , Nanopartículas de Magnetita/toxicidade , Masculino , Fenômenos Ópticos , Tamanho da Partícula , Soluções/toxicidade
12.
Molecules ; 25(7)2020 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-32272570

RESUMO

Titanium dioxide (TiO2) thin films were rapidly coated on Corning glass substrates from the precursor solution using the wire-bar technique at the room temperature and then post-annealed at 400, 500 and 600 °C for 1 h under atmospheric conditions. The structural, morphological, optical, wettability and photocatalytic properties of the films were studied. X-ray diffraction analysis confirmed the formation of an anatase TiO2 structure irrespective of the post-annealing temperatures. The optical transparency of the films in the visible range was measured to be > 70%. A water contact angle (WCA) of ~0° was observed for TiO2 thin-film, post-annealed at 400 °C and 500 °C. However, WCA of 40.3° was observed for post-annealed at 600 °C. The photocatalytic dye-degradation using post-annealed thin-film was investigated indicating a steady improvement in the dye-degradation percentage (from 24.3 to 29.4%) with the increase of post-annealing temperature. The demonstrated TiO2 thin-films deposited by wire-bar coating technique showed promises for the manufacturing of large-area cost-effective self-cleaning window glass.


Assuntos
Corantes/química , Titânio/química , Catálise , Vidro/química , Fotoquímica/métodos , Soluções/química , Temperatura , Molhabilidade , Difração de Raios X/métodos
13.
Mater Sci Eng C Mater Biol Appl ; 109: 109918, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32228997

RESUMO

Solid solutions of sparingly water-soluble drugs and highly water-soluble excipients are widely used for enhancing the drug delivery rate into the blood stream. The basic physico-chemical mechanisms, however, are not well understood. To delineate the mechanisms, therefore, in this work solid-solution fibers are immersed in a small volume of dissolution fluid and the drug concentration is monitored versus time. Two formulations are considered: ibuprofen drug and low-molecular-weight hydroxypropyl methyl cellulose (HPMC) excipient; and ibuprofen and HPMC and polyoxyl stearate (POS) excipients. The fibers dissolved in the dissolution fluid and the drug was released up to three orders of magnitude faster than by ibuprofen particles, yielding a maximum supersaturation in the fluid up to 6.5 in 10-15 minutes. Past the maximum, when the fiber was fully dissolved, the drug concentration gradually decreased to terminal solubility, up to a factor of 10 greater than that of pure ibuprofen. Models suggest that the drug release rate is proportional to the drug concentration at the fiber-fluid interface, which is enhanced due to both supersaturation and solubility-increase. The interface supersaturates because the drug-molecule release rate from the fast-eroding HPMC fibers is greater than the precipitation rate within; the solubility increases proportionally to the concentration of micelle-forming POS. Similarly, the dissolution fluid supersaturates, and due to the presence of POS in the solution the terminal solubility is increased. Thus the solid-solution fibers with dual, low-molecular-weight HPMC-POS excipient enhance the release rate, supersaturation, and solubility of sparingly-soluble drugs, and their delivery rate into the blood stream.


Assuntos
Derivados da Hipromelose/química , Soluções/química , Micelas , Peso Molecular , Solubilidade
14.
Phys Chem Chem Phys ; 22(13): 6919-6927, 2020 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-32181454

RESUMO

The amino acid lysine has been shown to prevent water crystallization at low temperatures in saturated aqueous solutions [S. Cerveny and J. Swenson, Phys. Chem. Chem. Phys., 2014, 16, 22382-22390]. Here, we investigate two ratios of water and lysine (5.4 water molecules per lysine (saturated) and 11 water molecules per lysine) by means of the complementary use of computer simulations and neutron diffraction. By performing a detailed structural analysis we have been able to explain the anti-freeze properties of lysine by the strong hydrogen bond interactions of interstitial water molecules with lysine that prevent them from forming crystalline seeds. Additional water molecules beyond the 1 : 5.4 proportion are no longer tightly bonded to lysine and therefore are free to form crystals.


Assuntos
Simulação por Computador , Crioprotetores/química , Lisina/química , Modelos Moleculares , Difração de Nêutrons , Água/química , Cristalização , Ligação de Hidrogênio , Soluções/química
15.
Vox Sang ; 115(5): 388-394, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32166752

RESUMO

BACKGROUND: Red blood cell (RBC) units accumulate morphologic and metabolic lesions during storage before transfusion. Pyruvate-inosine-phosphate-adenine (PIPA) solutions (Rejuvesol, Biomet, Warsaw, IN) can be incubated with RBC units to mitigate storage lesions. This study proposes a PIPA treatment process, termed cold 'rejuvenation', using Rejuvesol as an adjunct additive solution, to prevent biomechanical storage lesions while avoiding the 1 h PIPA incubation required with standard PIPA treatment. We compared the efficacy of cold to standard 'rejuvenation' in improving metabolic lesions that occur during cold storage of RBCs, without altering function. METHODS: Twelve leucoreduced, A-positive RBC units were obtained. Each unit was aliquoted into either control (standard storage), washed (W), standard rejuvenation (SR) or cold rejuvenation (CR) groups, the latter two requiring washing. A volume-adjusted dose of Rejuvesol was instilled into the CR group upon receipt (Day 3). After 15 days of storage, p50, RBC deformability, in-bag haemolysis and mechanical fragility were analysed. 'Any treatment' is defined as W, SR and CR, with comparisons in reference to control. RESULTS: Higher p50s were seen in rejuvenated groups (>30 mmHg vs. <19 mmHg; P < 0·0001). Any treatment significantly increased elongation index (P = 0·034) but did not significantly increase in-bag haemolysis (P = 0·062). Mechanical fragility was not significantly different between groups (P = 0·055) at baseline, but the control (CTL) group was more fragile after 2 h in a cardiac bypass simulation than any treatment (P < 0·0001). CONCLUSIONS: This study demonstrates that rejuvenation (standard or cold) prevents the leftward p50 shift of storage lesions without detrimental effect on RBC deformity, in-bag haemolysis or mechanical fragility.


Assuntos
Preservação de Sangue/métodos , Temperatura Baixa , Eritrócitos/metabolismo , Adenina , Hemoglobinas/metabolismo , Hemólise , Humanos , Inosina , Oxigênio/sangue , Ácido Pirúvico , Soluções/química
16.
Nature ; 579(7799): 379-384, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32188949

RESUMO

Automated synthesis platforms accelerate and simplify the preparation of molecules by removing the physical barriers to organic synthesis. This provides unrestricted access to biopolymers and small molecules via reproducible and directly comparable chemical processes. Current automated multistep syntheses rely on either iterative1-4 or linear processes5-9, and require compromises in terms of versatility and the use of equipment. Here we report an approach towards the automated synthesis of small molecules, based on a series of continuous flow modules that are radially arranged around a central switching station. Using this approach, concise volumes can be exposed to any reaction conditions required for a desired transformation. Sequential, non-simultaneous reactions can be combined to perform multistep processes, enabling the use of variable flow rates, reuse of reactors under different conditions, and the storage of intermediates. This fully automated instrument is capable of both linear and convergent syntheses and does not require manual reconfiguration between different processes. The capabilities of this approach are demonstrated by performing optimizations and multistep syntheses of targets, varying concentrations via inline dilutions, exploring several strategies for the multistep synthesis of the anticonvulsant drug rufinamide10, synthesizing eighteen compounds of two derivative libraries that are prepared using different reaction pathways and chemistries, and using the same reagents to perform metallaphotoredox carbon-nitrogen cross-couplings11 in a photochemical module-all without instrument reconfiguration.


Assuntos
Técnicas de Química Sintética/instrumentação , Técnicas de Química Sintética/métodos , Triazóis/síntese química , Anticonvulsivantes/síntese química , Anticonvulsivantes/química , Automação/instrumentação , Automação/métodos , Carbono/química , Indicadores e Reagentes/química , Nitrogênio/química , Oxirredução , Processos Fotoquímicos , Bibliotecas de Moléculas Pequenas/síntese química , Bibliotecas de Moléculas Pequenas/química , Software , Soluções/química , Triazóis/química
17.
Food Chem ; 320: 126566, 2020 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-32203841

RESUMO

In this study, the solubility, density and viscosity of sorbitol as a sugar alcohol in the ([mmim](MeO)2PO2) ionic liquid (IL) were measured. The results indicated that sorbitol is highly soluble in this IL. The Flory-Huggins model with an average value for the χ parameter was successfully applied to predict the solubility of sorbitol in IL. The thermodynamic properties such as enthalpy, entropy and Gibbs free energy of dissolution were obtained using experimental solubility data, which demonstrated that the dissolution process is endothermic and non-spontaneous and includes an entropy increase. In addition, the apparent molar volume, apparent molar expansion and thermal expansion coefficient were calculated. The study of the rheological behavior revealed that the sorbitol/IL solution is Newtonian and the Arrhenius, Litovitz, Orrick-Erbar-Type and Vogel-Fulcher-Tamman models were used to correlate the viscosity data.


Assuntos
Líquidos Iônicos/química , Reologia , Sorbitol/química , Solubilidade , Soluções/química , Termodinâmica , Viscosidade
18.
Sci Adv ; 6(5): eaax5785, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-32064336

RESUMO

Mimicking the cellular environment, metal-organic frameworks (MOFs) are promising for encapsulating enzymes for general applications in environments often unfavorable for native enzymes. Markedly different from previous researches based on bulk solution synthesis, here, we report the synthesis of enzyme-embedded MOFs in a microfluidic laminar flow. The continuously changed concentrations of MOF precursors in the gradient mixing on-chip resulted in structural defects in products. This defect-generating phenomenon enables multimodal pore size distribution in MOFs and therefore allows improved access of substrates to encapsulated enzymes while maintaining the protection to the enzymes. Thus, the as-produced enzyme-MOF composites showed much higher (~one order of magnitude) biological activity than those from conventional bulk solution synthesis. This work suggests that while microfluidic flow synthesis is currently underexplored, it is a promising strategy in producing highly active enzyme-MOF composites.


Assuntos
Enzimas/química , Estruturas Metalorgânicas/química , Microfluídica , Microambiente Celular , Estabilidade Enzimática/efeitos dos fármacos , Soluções/síntese química , Soluções/química , Soluções/farmacologia
19.
Soft Matter ; 16(8): 2128-2134, 2020 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-32016274

RESUMO

In globular protein systems, upper critical solution temperature (UCST) behavior is common, but lower critical solution temperature (LCST) phase transitions are rare. In addition, the temperature sensitivity of such systems is usually difficult to tune. Here we demonstrate that the charge state of globular proteins in aqueous solutions can alter their temperature-dependent phase behavior. We show a universal way to tune the effective protein interactions and induce both UCST and LCST-type transitions in the system using trivalent salts. We provide a phase diagram identifying LCST and UCST regimes as a function of protein and salt concentrations. We further propose a model based on an entropy-driven cation binding mechanism to explain the experimental observations.


Assuntos
Lactoglobulinas/química , Soroalbumina Bovina/química , Soluções/química , Animais , Bovinos , Entropia , Transição de Fase , Temperatura
20.
Artigo em Inglês | MEDLINE | ID: mdl-31991318

RESUMO

Meiguihua oral solution (MOS), a classical Chinese medicinal formula, was approved by the China Food and Drug Administration for production. However, the quality evaluation of MOS has not been reported. In this present study, qualitative and quantitative analysis of MOS were conducted by ultra high performance liquid chromatography coupled to quadrupole-orbitrap high resolution mass spectrometry (UHPLC-Q-orbitrap-HRMS) and high performance liquid chromatography-tri-quadrupole linear ion trap mass spectrometry (HPLC-tri-Q-LIT-MS). Totally 46 phenolic compounds (21 flavonoids and 25 tannins) were identified in the MOS, among them 14 polyphenols were not reported in raw plant materials of MOS. The simultaneous quantification of ten compounds including gallic acid, quercetin-3-O-sophoroside, ellagic acid, sophoraflavonoloside, hyperoside, isoquercitrin, avicularin, astragalin, quercitrin and juglanin, which were completed in 16 min in the negative electrospray ionization (ESI) mode under multiple reaction monitoring (MRM) method. Linearity was reached fine determination coefficient (r2 > 0.9995). Precisions, repeatability, stability (inter-day and intra-day), and recovery were validated and the relative standard deviations (RSD) were less than 2.9%, 4.7%, 3.6% and 1.79%, respectively. This result proved the high sensitivity and efficiency of the method. The quantitative and qualitative analysis of MOS would provide the substantial basis for further quality control and medicinal values.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Medicamentos de Ervas Chinesas/análise , Medicamentos de Ervas Chinesas/química , Espectrometria de Massas em Tandem/métodos , Flavonoides/análise , Flavonoides/química , Flavonoides/isolamento & purificação , Limite de Detecção , Modelos Lineares , Reprodutibilidade dos Testes , Soluções/química
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