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1.
Nat Commun ; 11(1): 541, 2020 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-31992713

RESUMO

The fast development of high-resolution electron microscopy (EM) demands a background-noise-free substrate to support the specimens, where atomically thin graphene membranes can serve as an ideal candidate. Yet the preparation of robust and ultraclean graphene EM grids remains challenging. Here we present a polymer- and transfer-free direct-etching method for batch fabrication of robust ultraclean graphene grids through membrane tension modulation. Loading samples on such graphene grids enables the detection of single metal atoms and atomic-resolution imaging of the iron core of ferritin molecules at both room- and cryo-temperature. The same kind of hydrophilic graphene grid allows the formation of ultrathin vitrified ice layer embedded most protein particles at the graphene-water interface, which facilitates cryo-EM 3D reconstruction of archaea 20S proteasomes at a record high resolution of ~2.36 Å. Our results demonstrate the significant improvements in image quality using the graphene grids and expand the scope of EM imaging.


Assuntos
Grafite/química , Microscopia Eletrônica/instrumentação , Microscopia Eletrônica/métodos , Fenômenos Químicos , Microscopia Crioeletrônica/métodos , Elétrons , Desenho de Equipamento , Processamento de Imagem Assistida por Computador , Membranas , Polímeros , Proteínas
2.
J Agric Food Chem ; 68(2): 503-511, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31869217

RESUMO

Due to nonuniform maturation, some plants may not be at the recommended stage of maturity when preharvest glyphosate is applied. The objective of this study was to determine how preharvest glyphosate timing affects wheat starch physicochemical properties. Two wheat cultivars were grown in three locations, and glyphosate was applied at the soft dough stage (early application) and the ripe stage (commercial standard). Upon harvest, starch chemical characteristics were studied. The proportion of B-type starch granules was lower in treated samples, although the starch molecular weight was not affected. Rapidly digestible starch content was highest when glyphosate was applied at the ripe stage, and lowest in the control, and vice versa for slowly digestible starch. Additionally, flour pasting viscosity was significantly higher in samples treated at the soft dough stage. Overall, the effects on wheat starch physicochemical characteristics were more pronounced when glyphosate was applied at the soft dough stage of maturity.


Assuntos
Glicina/análogos & derivados , Herbicidas/farmacologia , Amido/química , Triticum/efeitos dos fármacos , Triticum/crescimento & desenvolvimento , Fenômenos Químicos , Glicina/farmacologia , Sementes/química , Sementes/efeitos dos fármacos , Sementes/crescimento & desenvolvimento , Sementes/metabolismo , Amido/metabolismo , Triticum/química , Triticum/metabolismo
3.
Food Chem ; 306: 125517, 2020 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-31606624

RESUMO

Pasting properties indicated that the yellowing process led to a reduced peak viscosity and breakdown value of the postharvest yellowing (PHY) rice compared to corresponding normal one. More importantly, the current study revealed that both moduli of G' and G″ of the gel formed from the PHY rice was lower than that of its corresponding rice and the yellowing significantly reduced the area of the hysteresis curve. Thus, it is proposed that PHY may inhibit the formation of a continuous network structure. Studies of moisture absorption dynamics and low-field NMR suggested that the yellowing process led to a faster moisture absorption and de-absorption, indicating a faster moisture fluidity in rice kernels induced by yellowing process. Potent of the "capillary channels" might be formed during rice yellowing, and these structural characteristics may be associated with its higher digestibility due to the accelerated diffusion of the digestive enzymes in rice kernels.


Assuntos
Oryza/química , Fenômenos Químicos , Cor , Amido/química , Viscosidade
4.
Food Chem ; 307: 125543, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31634760

RESUMO

Phosphate fertilisation affects the growth, development and quality of Tartary buckwheat. In this study, the effect of different phosphorus levels, including 0, 15, 75, and 135 kg/ha (non-, low-, medium-, and high-phosphorus levels, respectively), on the characteristics of starch from Tartary buckwheat were investigated in 2015 and 2017. With increased phosphorus level, the median diameter of starch granules and the apparent amylose content initially decreased and then increased. All starch samples showed the features of A-type X-ray diffraction patterns. Starches under medium-phosphorus treatment showed higher relative crystallinity than those under non-phosphorus treatment, as well as the highest solubility, gelatinisation enthalpy and transmittance among all starches. Starches under low-phosphorus treatment exhibited higher pasting properties than those under non-phosphorus treatment. This research revealed that phosphorus treatments and year significantly affected the physicochemical properties of Tartary buckwheat starch, and can provide information for the applications of starch in the food and non-food industries.


Assuntos
Fagopyrum/química , Fertilizantes , Fosfatos/farmacologia , Amido/química , Amilose/química , Fenômenos Químicos , Fagopyrum/efeitos dos fármacos , Solubilidade
5.
Food Chem ; 303: 125344, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31446363

RESUMO

The effect of annealing on structure and physicochemical properties of four different waxy starches were investigated to understand the mechanism of annealing in the absence of amylose. Granule morphology, X-ray pattern, molecular order, and gelatinization enthalpy remained unchanged upon annealing. Relative crystallinity of waxy corn starch increased from 42.4 to 46.1% on annealing, while it remained unchanged in other starches. Annealing increased the gelatinization temperatures, while it decreased the temperature range. Waxy potato starch showed the highest increase in To, where it was 8.1 °C after 72 h of annealing. Viscosity profiles were only slightly affected by the annealing treatment. Susceptibility towards amylolysis increased in waxy corn and waxy barley, while it decreased in waxy potato and waxy rice. This study demonstrated that even in the absence of amylose, annealing caused changes in the structure and properties, however, the extents of these changes varied depending on the botanical origin.


Assuntos
Fenômenos Químicos , Amido/química , Ceras/química , Amilopectina/química , Amilose/química , Oryza/química , Solanum tuberosum/química , Temperatura Ambiente , Viscosidade , Zea mays/química
6.
Food Chem ; 308: 125676, 2020 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-31655476

RESUMO

In this study, the improving effects of green tea powder, soluble tea, and tea polyphenols on the mixing and tensile qualities of dough and texture of tea-enriched noodles, as well as the physico-chemical and structural properties of gluten proteins were progressively investigated. Dough strength and noodle texture were significantly increased by all the three tea products. Tea polyphenols in particular presented the most effective improvement with highest dough stability, resistance, and noodle chewiness. SEM indicated that tea products all induced a more developed gluten network, and polyphenol noodle showed the most continuous and ordered structure. FT-IR and fluorescence spectrum indicated that tea polyphenols promoted an enhancement in α-helix structure and the hydrophobic interactions. Tea polyphenols induced the SH/SS interchange during processing and cooking, and enhanced the water-solids interaction in noodles. AFM results showed that polyphenols induced the polymerization of gluten protein molecular chains, with increased chain height and width.


Assuntos
Polifenóis/química , Chá/química , Triticum/química , Fenômenos Químicos , Culinária , Glutens/química , Espectroscopia de Infravermelho com Transformada de Fourier
7.
J Dairy Res ; 86(4): 477-482, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31823833

RESUMO

The work described in this Research Communication concerns the production of Dulce de leche (DL), that is a traditional product from South America obtained by concentration. Maillard reaction (MR) products are mainly responsible for the formation of color and flavor in this product. Lactose-hydrolyzed products have been developed to supply consumer demand, but this hydrolysis may affect the flavor, color, taste, texture and even some nutritional aspects of the product. We studied the influence of different levels of lactose-hydrolysis, sucrose addition and initial pH on the development of MR, appraised by the determination of 5-hydroxymethylfurfural (HMF). A process simulator with multi-monitoring system was used to produce 15 DL. Box-Behnken 33 experimental design was applied for the three factors: pH, lactose-hydrolysis level and sucrose concentration. Lipids, protein, ashes, carbohydrates, water activity, dissolved solids, colorimetric analysis and HMF (free and total) are among the physicochemical attributes and MR indicators analyzed in this work. The products showed significant differences in composition but all the values were in agreement with the literature. Moreover, higher levels of lactose hydrolysis and higher pH presented a direct relation with the development of MR, observed by an increase in coloration (lower luminosity) and more formation of HMF, both free and total. The present study expands the knowledge about DL spread made of lactose-hydrolyzed milk, allowing the food industries to produce a lactose free DL with nutritional and sensory characteristics closer to the traditional product.


Assuntos
Furaldeído/análogos & derivados , Lactose/química , Leite/química , Animais , Fenômenos Químicos , Cor , Manipulação de Alimentos/métodos , Furaldeído/química , Concentração de Íons de Hidrogênio , Hidrólise , Reação de Maillard , América do Sul , Sacarose/análise , Sacarose/química , Paladar
8.
J Food Sci ; 84(11): 3099-3108, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31645089

RESUMO

In this work, different chemometric tools were compared to classify n = 26 conventional (CONV) and n = 19 organic (ORG) coffees from the main Brazilian producing regions based on the chemical composition, physicochemical properties, and antioxidant activity. Principal component analysis separated ORG and CONV coffees but the distinction among the producing regions of Brazilian coffee was not possible. Partial least squares discriminant analysis classified all ORG and CONV coffees in the external validation. Similarly, linear discriminant analysis was able to discriminate 100% and 81% of ORG and CONV coffees in the external validation, respectively, in which total phenolic content (TPC), ferric reducing antioxidant activity, and caffeic acid were the main discriminant variables. Overall 100% of samples from Paraná, Minas Gerais, and blended samples were correctly classified, where TPC, flavonoids, inhibition of lipid peroxidation, caffeic acid, pH, and soluble solids were the main discriminant variables. Support vector machines classified 95% ORG and 88% CONV, 100% Coffea arabica, and 88% and 78% coffees produced in São Paulo and Minas Gerais. k-Nearest neighbors was effective in distinguishing 100% CONV, 89% ORG, 100% coffees from São Paulo, and 100% C. arabica coffees. Overall, HPLC data and simple physicochemical parameters allied to chemometrics were effective in authenticating the cultivation system and the botanical origin of Brazilian coffees. PRACTICAL APPLICATION: Coffee adulteration is a serious problem in the food chain as some fraudsters replace coffee powder by other cheaper products. In the case of organic coffee, this scenario is even worse as still there is not a universal method to differentiate conventionally grown coffee from its organic counterpart. In addition, Brazilian coffee is produced in different regions and the commercial value varies. Therefore, we analyzed some physicochemical, chemical, and antioxidant properties of Brazilian coffees from distinct origins and classified the samples using chemometrics. Our approach seems to be interesting for quality control purposes.


Assuntos
Coffea/química , Café/química , Contaminação de Alimentos/análise , Antioxidantes/análise , Antioxidantes/farmacologia , Brasil , Ácidos Cafeicos/análise , Fenômenos Químicos , Análise Discriminante , Flavonoides/análise , Concentração de Íons de Hidrogênio , Análise dos Mínimos Quadrados , Fenóis/análise , Análise de Componente Principal , Sementes/química
9.
J Food Sci ; 84(11): 3156-3162, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31599973

RESUMO

This research is aimed to observe the impact of pulsed electric field (PEF) application on the free amino acids, physicochemical characteristics, and bioactive components of alcoholic beverages processed from date palm fruits. The fruits were treated by PEF (frequency: 10 Hz, treatment time: 100 µs, pulses number: 40 µs for electric field: 1.38, 2.02, and 2.92 kV/cm, respectively). A significant increase (P < 0.05) in the total free amino acids and phenolic and flavonoid contents (2.92 > 2.02 > 1.38 kV/cm) was observed. There was a minor significant difference among the treated samples in the total soluble solid, alcohol, and total sugar contents, while there were no significant changes in the other parameters, including the color attributes. PRACTICAL APPLICATION: This study observed whether PEF treatment has a positive impact on the processing of alcoholic beverages of date palm fruits. PEF was found to improve the bioactive components and nutritional value of alcoholic beverages processed from date palm fruits. This finding suggests that PEF can be a better technique to enhance the quality characteristics of date palm fruit alcoholic beverages.


Assuntos
Bebidas Alcoólicas/análise , Aminoácidos/análise , Manipulação de Alimentos/métodos , Frutas/química , Phoeniceae/química , Compostos Fitoquímicos/análise , Fenômenos Químicos , Eletricidade , Flavonoides/análise , Fenóis/análise
10.
Water Environ Res ; 91(10): 1350-1377, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31529571

RESUMO

The review scans research articles published in 2018 on physico-chemical processes for water and wastewater treatment. The paper includes eight sections, that is, membrane technology, granular filtration, flotation, adsorption, coagulation/flocculation, capacitive deionization, ion exchange, and oxidation. The membrane technology section further divides into six parts, including microfiltration, ultrafiltration, nanofiltration, reverse osmosis/forward osmosis, and membrane distillation. PRACTITIONER POINTS: Totally 266 articles on water and wastewater treatment have been scanned; The review is sectioned into 8 major parts;  Membrane technology has drawn the widest attention from the research community.


Assuntos
Purificação da Água , Fenômenos Químicos , Filtração , Floculação , Membranas Artificiais , Osmose , Eliminação de Resíduos Líquidos , Águas Residuárias
11.
Int J Nanomedicine ; 14: 6589-6600, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31496700

RESUMO

Background: The RAS family of oncogenes (KRAS, HRAS, NRAS) are the most frequent mutations in cancers and regulate key signaling pathways that drive tumor progression. As a result, drug delivery targeting RAS-driven tumors has been a long-standing challenge in cancer therapy. Mutant RAS activates cancer cells to actively take up nutrients, including glucose, lipids, and albumin, via macropinocytosis to fulfill their energetic requirements to survive and proliferate. Purpose: We exploit macropinocytosis pathway to deliver nanoparticles (NPs) in cancer cells harboring activating KRAS mutations. Methods: NPs were synthesized by the desolvation method. The physicochemical properties and stability of NPs were characterized by dynamic light scattering and transmission electron microscopy. Uptake of fluorescently labelled NPs in wild-type and mutant KRAS cells were quantitively determined by flow cytometry and qualitatively by fluorescent microscopy. NP uptake by KRAS-driven macropinocytosis was confirmed by pharmacological inhibition and genetic knockdown. Results: We have synthesized stable albumin NPs that demonstrate significantly greater uptake in cancer cells with activating mutations of KRA S than monomeric albumin (ie, dissociated form of clinically used nab-paclitaxel). From pharmacological inhibition and semi-quantitative fluorescent microscopy studies, these NPs exhibit significantly increased uptake in mutant KRAS cancer cells than wild-type KRAS cells by macropinocytosis. Conclusions: The uptake of albumin nanoparticles is driven by KRAS. This NP-based strategy targeting RAS-driven macropinocytosis is a facile approach toward improved delivery into KRAS-driven cancers.


Assuntos
Espaço Intracelular/metabolismo , Nanopartículas/administração & dosagem , Oncogenes , Pinocitose , Proteínas Proto-Oncogênicas p21(ras)/metabolismo , Linhagem Celular Tumoral , Fenômenos Químicos , Humanos , Nanopartículas/química , Nanopartículas/ultraestrutura , Tamanho da Partícula , Soroalbumina Bovina/metabolismo
12.
Molecules ; 24(18)2019 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-31487833

RESUMO

Nü-Er-Cha, produced from the leaves of Rhamnus heterophylla Oliv., is known as an herbal tea and used in the treatment of bleeding, irregular menstruation and dysentery. A method was developed for the quality assessment of herbal tea, Nü-Er-Cha, adopting physical parameters, chemical constituents and sensory profiles as various potential factors. Their inner relationship was mined by multivariate statistical analysis tools, and the three factors were integrated by a technique for order preference by a similarity to ideal solution (TOPSIS) approach to comprehensively analyze the characters of Nü-Er-Cha. Viscosity was also introduced to the physical parameter determination besides conductivity, pH and color. Seven common peaks of eight batches of Nü-Er-Cha were marked by a high performance liquid chromatography (HPLC) fingerprint. They were further identified by HPLC mass spectrometry/mass spectrometry (HPLC-MS/MS) as hydroxybenzoic acids and flavanol glycosides. Fifty trained members participated in the sensory evaluation. Significant correlations between total sensory scores and conductivity, viscosity as well as pH were observed, a relatively innovative result for the quality assessment of herbal teas. The common peaks, belonging to hydroxybenzoic acids and flavanol glycosides, were mainly related to the color of infusions and leaves. The result of the TOPSIS analysis showed that S3 and S4 ranked as the top two in the comprehensive quality assessment. This may be related to rhamnetin triglycoside with a galactose/glucose and two rhamnoses, which had a higher peak response in S3 and S4 than that in the other samples. The present study may contribute to a better understanding of the relationship regarding physical properties, chemical composition and sensory profiles, and it may supply ideas for the comprehensive quality assessment of the herbal tea Nü-Er-Cha.


Assuntos
Extratos Vegetais/química , Extratos Vegetais/farmacologia , Rhamnus/química , Fenômenos Químicos , Cromatografia Líquida de Alta Pressão , Medicamentos de Ervas Chinesas/química , Flavonoides/química , Flavonoides/farmacologia , Glicosídeos/química , Glicosídeos/farmacologia , Análise Espectral , Espectrometria de Massas em Tandem
13.
Environ Monit Assess ; 191(10): 626, 2019 Sep 09.
Artigo em Inglês | MEDLINE | ID: mdl-31501951

RESUMO

Two kitchen garden soils (A and B) sampled in contaminated areas were amended using phosphates in sustainable quantities in order to reduce the environmental availability of potentially toxic inorganic elements (PTEs) and to favour the availability of alkali, alkali earth and micronutrients. The environmental availability of PTEs was evaluated using a potential plant for revegetation of contaminated soils (ryegrass) and a mixture of low molecular weight organic acids. Despite the highest contamination level of B, the concentration of metals was highest in the ryegrass shoots grown on A for the two harvests. These results correlated well with those obtained using low molecular weight organic acids for Cd, Zn and Cu, whereas this mixture failed to represent the transfer of nutrients due to the presence of biological and physiological mechanisms. The statistical differences between the biomass of ryegrass obtained at the first and the second harvests were attributed to the decrease of available potassium, implicated in the growth and development of plants. Phosphates increased the ratios Zn/Cd, Zn/Pb and Zn/Cu up to 176 ± 48, 38 ± 6 and 80 ± 12, respectively, and made possible the reduction of the concentration of Cd and Pb in the shoots of ryegrass by 22% and 25%, respectively. The concentration of Zn in the shoots of ryegrass from the first and the second harvests grown on soil A were in the range 1050-2000 mg kg-1, making this plant a potential biomass to (i) produce biosourced catalysts for organic chemistry applications in a circular economy concept and (ii) limit human exposure to commercial Lewis acids. A preliminary application was identified.


Assuntos
Lolium/crescimento & desenvolvimento , Metais Pesados/metabolismo , Fosfatos/administração & dosagem , Poluentes do Solo/química , Solo/química , Biodegradação Ambiental , Biomassa , Cádmio/metabolismo , Fenômenos Químicos , Cobre/metabolismo , Poluição Ambiental , Humanos , Chumbo/metabolismo , Lolium/metabolismo , Desenvolvimento Sustentável , Zinco/metabolismo
14.
Adv Exp Med Biol ; 1148: 115-129, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31482497

RESUMO

Therapeutic proteins are a rapidly growing class of drugs in clinical settings. The pharmacokinetics (PK) of therapeutic proteins relies on their absorption, distribution, metabolism, and excretion (ADME) properties. Moreover, the ADME properties of therapeutic proteins are impacted by their physicochemical characteristics. Comprehensive evaluation of these characteristics and their impact on ADME properties are critical to successful drug development. This chapter summarizes all relevant physicochemical characteristics and their effect on ADME properties of therapeutic proteins.


Assuntos
Proteínas/farmacologia , Proteínas/farmacocinética , Fenômenos Químicos , Proteínas/química , Relação Estrutura-Atividade
15.
Bull Soc Pathol Exot ; 112(2): 105-113, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31478623

RESUMO

Mosquitoes occupy a major health problem, as a potential vector for the transmission of many pathogens, the most important of which in Morocco are Plasmodium parasites and West Nile fever virus. Acquiring knowledge about the biotypology of these mosquitoes is an essential step in any control strategy. Thus, the objective of this study is to draw up an inventory of the culicidian fauna in the Fez region (North-central part of Morocco) and to determine the physicochemical parameters influencing the production of mosquito larvae of aquatic habitats in this area. Mosquito larvae of the extant biotopes were sampled every two months between November 2015 and December 2016, by means of the "dipping" method. The physicochemical parameters of the various larval biotopes were collected six times during the year of follow-up. Mosquito species were identified using morphological criteria. The results were analyzed using ecological indices and the generalized linear model (Poisson model) on R software. The identification of the 1,122 mosquito larvae collected from the various studied breeding areas revealed the presence of 11 species belonging to two subfamilies (Culicinae and Anophelinae) and five genera (Anopheles, Culex, Culiseta, Aedes, and Uranotaenia). Anopheles were observed in small numbers in permanent, stagnant, and shallow habitats. The larvae of An. maculipennis s. l. (major vector of malaria in Morocco) were collected. Culex larvae, especially Cx. pipiens (the main vector of WNV in Morocco), were collected in the majority of the larval habitats and on the different types of environments. Two other species of Culex, which plays a significant role in the transmission of WNV, were also collected, particularly, Cx. perexiguus and Cx. theileri. The results found, via this first study of its kind at the regional level, also made it possible to update the list of Culicidae species reported in the Fez region. Four new species have been recorded: Aedes flavescens, Uranotaenia unguiculata, Culiseta longiareolata, and Culex perexiguus. The results of this study will contribute to the provision of information for entomological surveillance and to better plan and guide vector control activities at local and national levels.


Assuntos
Culicidae/citologia , Ecossistema , Larva/citologia , Microbiologia da Água , Água/análise , Água/parasitologia , Animais , Contagem de Células , Fenômenos Químicos , Culicidae/crescimento & desenvolvimento , Vetores de Doenças , Humanos , Larva/crescimento & desenvolvimento , Marrocos/epidemiologia , Mosquitos Vetores , Urbanização , Poluição da Água/análise , Poluição da Água/estatística & dados numéricos
16.
Molecules ; 24(16)2019 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-31412609

RESUMO

Nanotechnologies are increasingly being developed for medical purposes. However, these nanomaterials require ultrastability for better control of their pharmacokinetics. The present study describes three types of ultrastable gold nanoparticles stabilized by thiolated polyethylene glycol groups remaining intact when subjected to some of the harshest conditions described thus far in the literature, such as autoclave sterilization, heat and freeze-drying cycles, salts exposure, and ultracentrifugation. Their stability is characterized by transmission electron microscopy, UV-visible spectroscopy, and dynamic light scattering. For comparison purposes, two conventional nanoparticle types were used to assess their colloidal stability under all conditions. The ability of ultrastable gold nanoparticles to encapsulate bimatoprost, a drug for glaucoma treatment, is demonstrated. MTS assays on human corneal epithelial cells is assessed without changing cell viability. The impact of ultrastable gold nanoparticles on wound healing dynamics is assessed on tissue engineered corneas. These results highlight the potential of ultrastable gold nanoparticles as a drug delivery system in ocular therapy.


Assuntos
Portadores de Fármacos , Sistemas de Liberação de Medicamentos , Ouro , Nanopartículas Metálicas , Linhagem Celular , Sobrevivência Celular , Fenômenos Químicos , Técnicas de Química Sintética , Portadores de Fármacos/química , Ouro/química , Humanos , Ligantes , Nanopartículas Metálicas/química , Nanopartículas Metálicas/ultraestrutura , Análise Espectral , Cicatrização
17.
Molecules ; 24(16)2019 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-31412646

RESUMO

Organosilanes (e.g., R'-SiOR3) provide hydrophobic functionality in thin-film coatings, porous gels, and particles. Compared with tetraalkoxysilanes (SiOR4), organosilanes exhibit distinct reaction kinetics and assembly mechanisms arising from steric and electronic properties of the R' group on the silicon atom. Here, the hydrolysis and condensation pathways of n-propyltrimethoxy silane (nPM) and a tri-fluorinated analog of nPM, 3,3,3-trifluoropropyl trimethoxy silane (3F), were investigated under aqueous conditions at pH 1.7, 2.0, 3.0, and 4.0. Prior to hydrolysis, 3F and nPM are insoluble in water and form a lens at the bottom (3F) or top (nPM) of the solutions. This phase separation was employed to follow reaction kinetics using a Turbiscan instrument to monitor hydrolysis through solubilization of the neat silane lens while simultaneously tracking condensation-induced turbidity throughout the bulk solution. Dynamic light scattering confirmed the silane condensation and particle aggregation processes reported by the turbidity scanning. Employing macroscopic phase separation of the starting reactants from the solvent further allows for control over the reaction kinetics, as the interfacial area can be readily controlled by reaction vessel geometry, namely by controlling the surface area to volume. In-situ turbidity scanning and dynamic light scattering revealed distinct reaction kinetics for nPM and 3F, attributable to the electron withdrawing and donating nature of the fluoro- and organo-side chains of 3F and nPM, respectively.


Assuntos
Difusão Dinâmica da Luz , Géis/química , Transição de Fase , Silanos/química , Soluções/química , Fenômenos Químicos , Difusão Dinâmica da Luz/métodos , Concentração de Íons de Hidrogênio , Hidrólise , Interações Hidrofóbicas e Hidrofílicas , Cinética , Nanopartículas/química
18.
Molecules ; 24(16)2019 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-31412647

RESUMO

The aim of this study was to compare the physicochemical, the microbiological, and the antioxidant characteristics of unifloral honey, polyfloral honey, honeydew, and hay meadows honey. Hay meadow is type of semi-natural grassland with a great floral diversity, an important resource for pollinators. Grasslands are the source of the spring nectar honey obtained in May and June. Water content, sugars (fructose, glucose, sucrose, trehalose, melezitose, maltose, erlose, turanose, and raffinose), electrical conductivity, phenolic content (gallic acid, protocatechuic acid, 4-hydrxybenzoic acid, vanilic acid, chlorogenic acid, caffeic acid, p-coumaric acid, rosmarinic acid, myricetin, quercitin, luteolin, kaempferol), color, viscosity, and microbiological characteristics were performed for all samples of honey. The total polyphenols content was significant for grassland honey (21.50 mg/100 g) and honeydew (30.49 mg/100 g) and less significant for acacia (0.08 mg/100 g) and rape honey (0.14 mg/100 g). All samples were microbiologically safe, and standard plate count (SPC) values were <10 cfu/g for all the samples, but the grassland honey had the highest microbiological quality: 33.3% of samples without microorganisms, 50.0% with the presence of yeast under limit, and 16.7% with yeast and mold under limit, a situation that does not meet other types of honey. The results of statistical analysis obtained with principal component analysis (PCA) showed a major difference between the grassland honey and the other types of honey.


Assuntos
Anti-Infecciosos/química , Anti-Infecciosos/farmacologia , Fenômenos Químicos , Flores , Pradaria , Mel/análise , Condutividade Elétrica , Testes de Sensibilidade Microbiana , Fenóis/análise , Fenóis/química , Açúcares/análise , Açúcares/química
19.
Int J Mol Sci ; 20(16)2019 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-31412656

RESUMO

The generic term "melanin" describes a black pigment of biological origin, although some melanins can be brown or even yellow. The pigment is characterized as a heterogenic polymer of phenolic or indolic nature, and the classification of eu-, pheo- and allo- melanin is broadly accepted. This classification is based on the chemical composition of the monomer subunit structure of the pigment. Due to the high heterogeneity of melanins, their analytical characterization can be a challenging task. In the present work, we synthesized the current information about the analytical methods which can be applied in melanin analysis workflow, from extraction and purification to high-throughput methods, such as matrix-assisted laser desorption/ionization mass-spectrometry or pyrolysis gas chromatography. Our thorough comparative evaluation of analytical data published so far on melanin analysis has proven to be a difficult task in terms of finding equivalent results, even when the same matrix was used. Moreover, we emphasize the importance of prior knowledge of melanin types and properties in order to select a valid experimental design using analytical methods that are able to deliver reliable results and draw consistent conclusions.


Assuntos
Melaninas/análise , Melaninas/isolamento & purificação , Animais , Fracionamento Químico , Fenômenos Químicos , Humanos , Estrutura Molecular , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , Análise Espectral
20.
Molecules ; 24(16)2019 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-31412665

RESUMO

The aim of the study was to characterize the antioxidant properties; establish the profile of polyphenolic compounds and evaluate the content of tocopherols in walnuts of three varieties (Leopold; Apollo; Resovia) differing in the degree of maturity (harvest date). The profile of polyphenolic compounds was established by UPLC-PDA-ESI-MS. The content of tocopherols was determined by HPLC-FLD. It was found that the content of dry matter and fat increased and the antioxidant properties decreased with the maturation of nuts. Walnuts of the Leopold cultivar harvested in July exhibited the highest content of total polyphenol (2149.08 mg/100 g dry mass). In their polyphenolic profile; 26 compounds were identified; mainly belonging to the class of ellagitannins. The polyphenolic content decreased with the maturation of nuts. The total content of tocopherols in the tested nuts increased with ripening and ranged from 1.76 mg/100g (Apollo VII) to 18.30 mg/100g (Resovia IX).


Assuntos
Antioxidantes/química , Antioxidantes/farmacologia , Juglans/química , Polifenóis/química , Polifenóis/farmacologia , Tocoferóis/química , Tocoferóis/farmacologia , Fenômenos Químicos , Cromatografia Líquida de Alta Pressão , Extratos Vegetais/química , Extratos Vegetais/farmacologia
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