Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 8.441
Filtrar
1.
Am J Dent ; 32(5): 240-244, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31675192

RESUMO

PURPOSE: To evaluate the effect of different thicknesses of CAD-CAM ceramic sections on the polymerization of two different resin cements. METHODS: Three CAD-CAM all-ceramic restorative materials were sectioned with four different thicknesses. A total of 240 resin cement specimens were prepared from light cured and dual cure resin cements and absorption peaks were recorded. 10 samples of each resin cement were examined before and after polymerization and served as the control group. Data were analyzed using one-way ANOVA, independent t- and Tukey HSD tests (P< 0.05). RESULTS: Control group showed the highest DOC values while samples cured under Vita Enamic section with a thickness of 2 mm presented the lowest values (P< 0.05). Polymerization performed under sections of 0.5 and 1 mm thicknesses provided statistically higher values. Dual cured resin cement samples showed higher DOC values compared to light cured resin cement samples. IPS Empress CAD sections with 0.5 and 1 mm thickness exhibited statistically higher values than other ceramics of the same thickness for light cured resin cement samples. A significant difference was observed between IPS Empress CAD and Vita Enamic while comparing ceramic sections of the same thickness (P< 0.05). There was no difference for sections of 1.5 and 2 mm (P>> 0.05). CLINICAL SIGNIFICANCE: Thickness of the restorative material for an indirect restoration is a key element to determine the type of resin cement.


Assuntos
Porcelana Dentária , Cimentos de Resina , Cerâmica , Projeto Auxiliado por Computador , Teste de Materiais , Polimerização
2.
Indian J Dent Res ; 30(4): 583-589, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31745057

RESUMO

Purpose: The study aimed to compare the effect of different materials, thicknesses, and polymerization methods and cycles, on the surface porosity of acrylic denture base resins. Materials and Methods: Conventional heat-polymerized polymethyl methacrylate (PMMA) and specially designed acrylic resin (Acron MC) were used to make 84 rectangular samples. They were divided into three groups to evaluate and compare the polymerization techniques, curing cycles, and thicknesses of the two denture base materials (28 samples each). Group A contained PMMA samples polymerized using water bath method (control group); Group B contained Acron MC samples polymerized by microwave method, and Group C contained PMMA samples polymerized by microwave method. Each group was further divided based on sample thickness and polymerization cycles. Each sample was scanned for surface porosity and area of each pore was measured using optical microscope. Data was analyzed using ANOVA, Bonferroni, and student t-tests. Unpaired student t-test was performed to compare the means of surface porosity with polymerization cycles and thicknesses among the groups. The power of study was kept at 80%. Results: Group C showed highest mean % of porosity depending on method of polymerization, different polymerization cycles (short and long) and polymerization cycles within the group. Group B showed the highest mean % of porosity depending on thickness and thickness within the groups. Conclusions: Microwavable acrylic resin polymerized by microwave energy exhibited statistically insignificant increase in porosity when compared to conventional heat cured acrylic resin by water bath method. Conventional acrylic resin polymerized by microwave energy exhibited high statistically significant porosity irrespective of sample thickness. There was statistically insignificant increase in porosity depending on sample thickness irrespective of material and method of polymerization.


Assuntos
Bases de Dentadura , Polimetil Metacrilato , Humanos , Teste de Materiais , Polimerização , Porosidade
3.
Water Sci Technol ; 80(4): 620-633, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31661441

RESUMO

The treatment of toxic and difficult-to-degrade phenolic compounds has become a key issue in the coking, pharmaceutical, and chemical industries. Considering the polymerization and oxidation of phenolic compounds in supercritical water partial oxidation/supercritical water oxidation (SCWPO/SCWO), the present study reviewed the removal efficiency and reaction pathway of phenolic compounds and phenolic waste/wastewater under different reaction conditions. Temperature is the dominant factor affecting the SCWO reaction. When the oxidizing ability is insufficient, the organics polymerize to form phenolic compounds. The gradual increase of oxidant equivalent causes the intermediate product to gradually oxidize to CO2 and H2O completely. Finally, the free radical reaction mechanism is considered to be a typical SCWO reaction mechanism.


Assuntos
Purificação da Água , Água , Oxirredução , Fenóis , Polimerização
4.
Medicine (Baltimore) ; 98(39): e17357, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31574880

RESUMO

Preoperative autologous blood donation is a well-established procedure to reduce the need for allogeneic blood transfusion. We hypothesized that coagulation activity is maintained in cold-stored whole blood, because the fundamental polymerization properties of fibrin are preserved.Fifty adult patients who underwent elective cardiothoracic surgery were enrolled.Autologous whole blood collected 2 to 4 times at almost 1-week intervals before surgery was stored at approximately 4°C until reinfusion at the time of surgery. Blood samples were drawn just before reinfusion, and rotational thromboelastometry variables and fibrinogen levels were measured.A total of 158 samples were analyzed. The mean duration of cold storage was 16.7 ±â€Š7.4 days (range: 6-33 days). Platelet counts were very low due to collection through a leukoreduction filter. The mean fibrinogen level was 2.3 ±â€Š0.6 g/L. Amplitude at 10 minutes after CT (A10), amplitude at 20 minutes after CT (A20), and maximum clot firmness (MCF) values as determined by FIBTEM analysis were 10.8 ±â€Š3.8, 12.2 ±â€Š4.2, and 13.1 ±â€Š4.7 mm, respectively. Fibrinogen levels were strongly correlated with A10, A20, and FIBTEM-MCF values (ρ = 0.83, P < .0001, ρ = 0.84, P < .0001, ρ = 0.85, P < .0001, respectively). Fibrinogen levels were not correlated with the duration of cold storage (ρ = 0.06, P = .43).The results of the present study demonstrate that fibrin polymerization occurs in cold-stored autologous whole blood, and that such activity is strongly correlated with fibrinogen levels. Furthermore, our data suggest that cold-stored leukoreduced autologous whole blood retains fibrin polymerization properties throughout 33 days.


Assuntos
Coagulação Sanguínea , Transfusão de Sangue/métodos , Tromboelastografia/métodos , Tempo de Coagulação do Sangue Total , Idoso , Testes de Coagulação Sanguínea , Temperatura Baixa , Feminino , Fibrina/química , Humanos , Masculino , Pessoa de Meia-Idade , Contagem de Plaquetas , Polimerização , Estudos Prospectivos
5.
Se Pu ; 37(10): 1090-1097, 2019 Oct 08.
Artigo em Chinês | MEDLINE | ID: mdl-31642288

RESUMO

A partially filled monolith was prepared by in situ polymerization, and then carrier ampholytes (CAs, pH 3-10) were immobilized on its surface. For effective utilization of capillary isoelectric focusing (cIEF) with the monolithic immobilized pH gradient (M-IPG), a new online platform was established by the introducing of an eight-way injection valve, a three-way valve and a cross-shaped unit. Besides, a capillary coated with hydroxypropyl cellulose (HPC capillary) was prepared and used to determine the isoelectric points (pI) of trastuzumab and etanercept. In parallel, using the newly built capillary isoelectric focusing platform, the pI values of trastuzumab and etanercept were measured with the M-IPG column, and compared with the results obtained using the HPC capillary. It was found that these two cIEF columns can be effectively used to separate proteins and determine the pI values of monoclonal antibodies and fusion proteins in protein drugs. Moreover, the measured pI values were consistent with those estimated using the HPC capillary.


Assuntos
Focalização Isoelétrica , Proteínas/química , Força Próton-Motriz , Anticorpos Monoclonais/química , Concentração de Íons de Hidrogênio , Ponto Isoelétrico , Polimerização
6.
J Chromatogr A ; 1604: 460478, 2019 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-31474467

RESUMO

In this study, fabrication of a stir bar sorbent is presented by electropolymerization of pyrrole via cyclic voltametry for the first time. The fabricated stir bar was applied as an efficient sorbent for extraction and pre-concentration of trace amounts of estradiol in urine samples through stir bar sorptive extraction (SBSE) method followed by gas chromatography-flame ionization detector. For this purpose, first the surface of stainless steel rod was modified by hyroxide functional group. Then electropolymerization of pyrrole monomers took place on the surface of functionalized steel rod under the optimized conditions including pyrrole concentration of 0.03 mol L-1, equal concentration ratio of pyrrole to sodium dodecyl sulfate, 10 cycles of cyclic voltammetry and potential scan rate of 10 mV s-1. Characterization of the produced sorbent was confirmed by scanning electron microscope imaging and energy-dispersive X-ray and infrared spectroscopy. Evantually, under the optimized conditions, the stir bar sorbent was used for extraction of estradiol from human urine samples. The presented SBSE method showed a good linearity range of 50-700 ng mL-1 with coefficient of determination 0.9910, limit of detection 10 ng mL-1 and theoretical limit of quantification 33 ng mL-1. Moreover, better enrichment factor (87) and extraction recovery (43%) were obtained using the fabricated stir bar compared with two commercial stir bars for estradiol. The intra- and inter-bar relative recoveries were obtained 92.0% and their coefficient of variations were less than 5.4%.


Assuntos
Cromatografia Gasosa/métodos , Eletroquímica/métodos , Estradiol/isolamento & purificação , Polimerização , Pirróis/química , Eletrodos , Humanos , Concentração de Íons de Hidrogênio , Padrões de Referência , Reprodutibilidade dos Testes , Fatores de Tempo
7.
Top Curr Chem (Cham) ; 377(5): 26, 2019 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-31529210

RESUMO

Lignin, one of the main components of lignocellulosic biomass, is the largest renewable source of aromatics on the planet and presents an extraordinary opportunity for being used in the production of bio-based products. It can be transformed for the substitution of aromatic chemical-derived petrol as BTXs. The wide range of applications that it can be obtained from BTXs building blocks makes the selective depolymerization of lignin a great scientific challenge. This review emphasizes the different strategies for the fragmentation of lignin to monomers or aromatics hydrocarbons. Thus, a by-product traditionally discarded or used for energy generation, it could be valorized into high added-value products.


Assuntos
Benzeno/química , Lignina/química , Tolueno/química , Xilenos/química , Líquidos Iônicos/química , Estrutura Molecular , Polimerização
8.
J Agric Food Chem ; 67(40): 11044-11052, 2019 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-31545599

RESUMO

Persimmon condensed tannins (PT) are highly polymerized (mDP = 26) and highly galloylated (72%) proanthocyanidins. Its pleiotropic effects in oxidation resistance, neuroprotection, hypolipidemia, and cardio-protection both in vitro and in vivo were widely reported. Because large proanthocyanidins are unlikely to be absorbed in the gastrointestinal tract, it is believed that the interaction of PT with biological membranes may play a crucial role in its biological activities. In the present study, the capacities of PT adsorbing to membrane, partitioning into membrane, and its influence on the membrane fluidity were investigated by fluorescence quenching, isothermal titration calorimetry (ITC) and fluorescence anisotropy measurements in a biomembrane-mimetic system composed of 1-palmitoyl-2-oleoylphosphatidylcholine (POPC), 1-palmitoyl-2-oleoylphosphatidylethanolamine (POPE), sphingomyelin (SPM), and cholesterol (CHOL). Besides, the effects of PT on the morphology and integrity of the cell membrane were studied by scanning electron microscopy (SEM) and fluorescence staining in the 3T3-L1 cell model. The results suggested that PT could affect cell membrane rafts domains, destroy the cell membrane morphology, and regulate cell membrane fluidity, which might contribute to its biological effects.


Assuntos
Membrana Celular/química , Diospyros/química , Extratos Vegetais/química , Proantocianidinas/química , Animais , Fenômenos Biofísicos , Membrana Celular/metabolismo , Colesterol/química , Colesterol/metabolismo , Frutas/química , Fluidez de Membrana , Camundongos , Células NIH 3T3 , Fosfatidilcolinas/química , Fosfatidilcolinas/metabolismo , Extratos Vegetais/metabolismo , Polimerização , Proantocianidinas/metabolismo , Esfingomielinas/química , Esfingomielinas/metabolismo
9.
Bioresour Technol ; 291: 121878, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31377047

RESUMO

Lignin is one of the most promising renewable sources for aromatic hydrocarbons, while effective depolymerization towards its constituent monomers is a particular challenge because of the structural complexity and stability. Intensive research efforts have been directed towards exploiting effective valorization of lignin for the production of bio-based platform chemicals and fuels. The present contribution aims to provide a critical review of key advances in the identification of exact lignin structure subjected to various fractionation technologies and demonstrate the key roles of lignin structures in depolymerization for unique functionalized products. Various technologies (e.g., thermocatalytic approaches, photocatalytic conversion, and mechanochemical depolymerization) are reviewed and evaluated in terms of feasibility and potential for further upgrading. Overall, advances in pristine lignin structure analysis and conversion technologies can facilitate recovery and subsequent utilization of lignin towards tailored commodity chemicals and fungible fuels.


Assuntos
Lignina/química , Polimerização
10.
Bioresour Technol ; 291: 121839, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31376673

RESUMO

Inorganic salt treatment is a novel, high-yield, and environmentally friendly approach for the production of xylo-oligosaccharides from Sugarcane bagasse with degree of polymerization of 2-5. A xylo-oligosaccharides yield of 53.79% was obtained with 0.1 M MgCl2 treatment at 180 °C/10 min, and 41.89% with 0.1 M FeCl2 treatment at 140 °C/30 min. The xylo-oligosaccharides yield from the co-catalysis of 0.05 M FeCl2 + 0.05 M MgCl2 reached 54.68% (29.34% xylobiose and 20.94% xylotriose) at 140 °C/30 min. The co-catalysis not only effectively improved the xylobiose and xylotriose contents but also increased the total yield of xylo-oligosaccharides under mild reaction conditions. Additionally, the glucose yield observed from the solid residue after inorganic salt treatment was 71.62% by enzymatic hydrolysis. Mg2+ and Fe2+ are essential for good human health without separation from the system, therefore, the inorganic salt treatment can be potentially applied in the co-production of xylo-oligosaccharides and glucose.


Assuntos
Celulose/química , Compostos Ferrosos/química , Cloreto de Magnésio/química , Oligossacarídeos/química , Saccharum/química , Catálise , Glucose/química , Hidrólise , Polimerização
11.
Chem Commun (Camb) ; 55(66): 9833-9836, 2019 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-31363722

RESUMO

Herein, through using electropolymerized pyrrole (PPy) to coat near-infrared upconversion nanoparticles (UCNPs) on an indium tin oxide (ITO) electrode, the as-prepared PPy/UCNPs photoelectrode could generate an interfacial electric field, release rare earth ions and induce reactive oxygen species (ROS) in PC12 cells under NIR irradiation, which could realize wireless neurite development and outgrowth.


Assuntos
Estimulação Elétrica , Crescimento Neuronal , Tecnologia sem Fio , Animais , Raios Infravermelhos , Células PC12 , Polimerização , Pirróis/química , Ratos , Espectrofotometria Ultravioleta
12.
Acta Crystallogr D Struct Biol ; 75(Pt 8): 718-732, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31373571

RESUMO

Pili in Gram-positive bacteria are flexible rod proteins associated with the bacterial cell surface, and they play important roles in the initial adhesion to host tissues and colonization. The pilus shaft is formed by the covalent polymerization of major pilins, catalyzed by sortases, a family of cysteine transpeptidases. Here, X-ray structures of the major pilins from Clostridium perfringens strains 13 and SM101 and of sortase from strain SM101 are presented with biochemical analysis to detect the formation of pili in vivo. The major pilin from strain 13 adopts an elongated structure to form noncovalently linked polymeric chains in the crystal, yielding a practical model of the pilus fiber structure. The major pilin from strain SM101 adopts a novel bent structure and associates to form a left-handed twist like an antiparallel double helix in the crystal, which is likely to promote bacterial cell-cell interactions. A modeling study showed that pilin with a bent structure interacts favorably with sortase. The major pilin from strain SM101 was considered to be in an equilibrium state between an elongated and a bent structure through dynamic conformational change, which may be involved in pili-mediated colonization and sortase-mediated polymerization of pili.


Assuntos
Clostridium perfringens/química , Proteínas de Fímbrias/química , Fímbrias Bacterianas/química , Aminoaciltransferases/química , Proteínas de Bactérias/química , Clonagem Molecular/métodos , Cristalografia por Raios X , Cisteína Endopeptidases/química , Escherichia coli/genética , Modelos Moleculares , Polimerização , Domínios Proteicos
13.
Food Chem ; 301: 125298, 2019 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-31387044

RESUMO

A synthetic scenario for functionalization of ß-lactoglobulin (ßLg) with polymeric units containing caffeic acid (ßLg-polyCA) was developed; and all intermediates and final products were structurally confirmed using nuclear magnetic resonance spectroscopy, matrix assisted laser desorption ionization time-of-flight mass spectrometry, and physico-chemically characterized using differential scanning calorimetry and circular dichroism. The antioxidant properties and emulsion stability of ßLg, ßLg-CA conjugate and ßLg-polyCA based systems containing high percentage of fish oil (50%) were evaluated; and ßLg-polyCA presented the highest antioxidant and free radical-scavenging activity based on DPPH, ABTS and HS scavenging assays (92.4, 87.92 and 67.35% respectively). Thiobarbituric acid (TBARS) test demonstrated that compared to native ßLg, ßLg-polyCA afford up 4-5 fold of inhibition of oxidative rancidity and displayed drastic secondary structure changes. Compared to native ßLg based emulsions, ßLg-polyCA had larger oil droplet sizes, stronger negative zeta potentials (-69.9 mv), narrower size distributions (PDI: 0.22) and less creaming index.


Assuntos
Antioxidantes/farmacologia , Emulsões/química , Óleos de Peixe/química , Lactoglobulinas/química , Fenóis/química , Antioxidantes/química , Ácidos Cafeicos/química , Varredura Diferencial de Calorimetria , Dicroísmo Circular , Difusão Dinâmica da Luz , Peroxidação de Lipídeos , Espectroscopia de Ressonância Magnética , Oxirredução , Polimerização , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz
14.
Bioelectrochemistry ; 130: 107287, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31400567

RESUMO

This work reports the first electrochemical molecularly imprinted polymer (MIP) sensor for Interleukin-1beta (IL-1ß) detection, based on modified commercial screen-printed carbon electrode (SPCE) was successfully demonstrated. For this purpose, the carbon support was modified with a PEDOT/4-aminothiophenol layer prior to the MIP film to enhance sensitivity and signal stability. The MIP layer was constructed on top of this by electropolymerization of Eriochrome black T (EBT) in the presence of IL-1ß. The several steps of the biosensor assembly was followed by Raman spectroscopy and electroanalytical techniques. Using electrochemical impedance spectroscopy (EIS), a linear response in the range of 60 pM to 600 nM, with a LOD of 1.5 pM with (S/N = 3) was obtained in neutral PBS. Selectivity tests of the MIP biosensor made in spiked synthetic serum samples as well as against other structurally related (Myoglobin, of similar shape and size) or competing compounds (Immunoglobulin G, also present in the human serum) confirmed the good selectivity of the biosensor. Overall, the biosensor described herein has the potential to provide a simple and quick way for on-site screening of IL-1ß, with low sample/reagent consumption and enabling direct serum analysis, which constitutes a valuable alternative to other conventional methods.


Assuntos
Técnicas Biossensoriais/métodos , Interleucina-1beta/sangue , Impressão Molecular/métodos , Compostos Azo/química , Técnicas Biossensoriais/instrumentação , Carbono/química , Espectroscopia Dielétrica/instrumentação , Espectroscopia Dielétrica/métodos , Eletrodos , Desenho de Equipamento , Humanos , Interleucina-1beta/análise , Impressão Molecular/instrumentação , Polimerização , Polímeros/química
15.
Bioresour Technol ; 291: 121885, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31377049

RESUMO

Lignin is the most abundant, renewable aromatic resource on earth and holds great potential for the production of value-added chemicals. The efficient valorization of lignin requires to deal with several formidable challenges, especially to prevent it from re-condensation reactions during its depolymerization. Recently, a strategy involving the activation of lignin side chains by selective oxidation of the benzylic alcohol in ß-O-4 linkages to facilitate lignin degradation to aromatic monomers has become very popular. This strategy provides great advantages for lignin selective degradation to high yields of aromatics under mild conditions, but requires an additional pre-oxidation step. The purpose of this review is to provide the latest cutting-edge innovations of this novel approach. Various catalytic systems, including those using chemo-catalytic methods, physio-chemo catalytic methods, and/or bio-catalytic methods, for the oxidative activation of lignin side chains are summarized. By analyzing the current situation of lignin depolymerization, certain promising directions are emphasized.


Assuntos
Lignina/química , Catálise , Oxirredução , Polimerização
16.
J Appl Oral Sci ; 27: e20180351, 2019 Jul 29.
Artigo em Inglês | MEDLINE | ID: mdl-31365707

RESUMO

OBJECTIVE: Since the transmittance of ceramics can influence the degree of conversion (DC) of resin cements, ceramics composition and shade should be considered in the selection of resin cement. This in vitro study aimed to evaluate the effect of the transmittance of different composition, opacities and shades of ceramics on the degree of conversion of two dual-cured resin cements. METHODOLOGY: Sixty discs were prepared from low translucency (LT) and medium opacity (MO) lithium disilicate ceramic, and zirconia ceramic (Z). Each group was subdivided into 5 subgroups (n=4) in shades A2, A3.5, B2, C2 and D3. The transmittance measurement was performed in a spectrophotometer. The Variolink II and Rely X U200 resin cements were photoactivated by LED (1400 mW/cm2) for 40 s through the ceramic discs and without the discs (control group). The DC was measured with infrared FTIR spectroscopy, immediately after light activation. Data were analyzed with Kruskall-Wallis and one-way ANOVA, following post-hoc comparisons by Tukey test and Pearson's correlation test (P<0.05). RESULTS: LT ceramic exhibited higher transmittance values compared to MO and Z ceramics. LTA2 and LTB2 showed statistically higher transmittance values compared to MOA2, MOA3.5 and ZA3.5. For Variolink II, the ceramic interposition did not influence the DC, since there were no statistical differences between groups with ceramic interposition and the control group. For Rely X U200 cement, the interposition of some ceramics types/shades (LTA3.5, MOA2, MOA3.5 and ZA3.5) significantly decreased the DC values compared to control group. A positive correlation was found between the ceramic transmittance and DC values of both tested cements. Conclusions. The transmittance and DC values of the cements were influenced by composition and shades of the ceramics. The higher the transmittance of ceramics, the higher the DC values for both cements.


Assuntos
Porcelana Dentária/química , Cimentos de Resina/química , Zircônio/química , Análise de Variância , Luzes de Cura Dentária , Cura Luminosa de Adesivos Dentários , Teste de Materiais , Transição de Fase , Polimerização , Valores de Referência , Reprodutibilidade dos Testes , Espectrofotometria/métodos , Estatísticas não Paramétricas
17.
Food Chem ; 299: 125132, 2019 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-31299519

RESUMO

Protein oxidation of beef patties stored in high oxygen modified atmosphere packaging for 9 days was investigated. Meat was either stored in the dark, under light, or in the dark with addition of FeCl2/H2O2/myoglobin (forced oxidation). SDS-PAGE analysis showed high degree of protein polymerization for meat exposed to light, compared to the other samples. Light exposure induced reducible (disulfide) and non-reducible cross-links, while mainly disulfides were formed in meat stored in the dark. Light exposure was responsible for 58% loss of free thiols (Cys residues). No significant loss of other amino acid residues was observed and none of the most common oxidation products of tryptophan, tyrosine, and phenylalanine were detected. Intrinsic fluorescence measurements of tryptophan showed 27% loss in samples exposed to light, which was ascribed to loss of protein solubility via protein polymerization rather than tryptophan oxidation. Protein carbonyls were mainly detected in forced oxidized samples at Day 0.


Assuntos
Armazenamento de Alimentos/métodos , Proteínas de Carne/química , Carne Vermelha , Animais , Bovinos , Dissulfetos/química , Embalagem de Alimentos , Peróxido de Hidrogênio/química , Luz , Mioglobina/química , Oxirredução , Oxigênio , Polimerização , Carne Vermelha/análise , Carne Vermelha/efeitos da radiação , Compostos de Sulfidrila/química , Triptofano/química , Tirosina/química , Raios Ultravioleta
18.
J Chromatogr A ; 1603: 269-277, 2019 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-31279475

RESUMO

In this study, a hydroxypropyl-ß-cyclodextrin (HP-ß-CD) functionalized monolithic capillary column was prepared by one-pot sequential reaction for the first time. The preparation of the HP-ß-CD functionalized monolithic column involves two sequential reactions in one pot: (1) the ring opening reaction between HP-ß-CD and glycidyl methacrylate (GMA) catalyzed by 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU); (2) the copolymerization of GMA-HP-ß-CD, ethylene dimethacrylate (EDMA) and 2-acrylamido-2-methyl propane sulfonic acid (AMPS). A series of monolithic columns were successfully prepared by varying the temperature of the ring opening reaction or several copolymerization parameters (the type and composition of porogenic solvents, ratio of GMA-HP-ß-CD to EDMA and polymerization temperature). Then, the morphologies and structures of the resulting monolithic stationary phases were characterized by optical microscopy, scanning electron microscopy (SEM) and nitrogen adsorption analysis. Raman spectroscopy clearly indicated the successful bonding of HP-ß-CD onto the monolith. When the prepared chiral stationary phase (CSP) was applied for the separation of a set of racemic compounds by capillary electrochromatography (CEC), including racemic anticholinergic drugs, ß-adrenergic drugs, meptazinol and its intermediates, satisfactory separation selectivities were obtained. Additionally, the column also showed excellent separation abilities towards four flavanone glycosides epimers. Furthermore, the prepared monolithic columns exhibited satisfactory stability and reproducibilities of retention time, resolution and column efficiency. These results demonstrated the potential and usefulness of the developed one-pot sequential strategy in the preparation of other derivatized CD functionalized monolithic columns.


Assuntos
2-Hidroxipropil-beta-Ciclodextrina/química , Eletrocromatografia Capilar/métodos , Adsorção , Compostos de Epóxi/química , Metacrilatos/química , Nitrogênio/química , Permeabilidade , Polimerização , Polímeros/química , Espectroscopia de Prótons por Ressonância Magnética , Reprodutibilidade dos Testes , Análise Espectral Raman , Estereoisomerismo , Temperatura Ambiente
19.
Nat Commun ; 10(1): 2946, 2019 07 03.
Artigo em Inglês | MEDLINE | ID: mdl-31270421

RESUMO

The capability to encapsulate designated live cells into a biologically and mechanically tunable polymer layer is in high demand. Here, an approach to weave functional DNA polymer cocoons has been proposed as an encapsulation method. By developing in situ DNA-oriented polymerization (isDOP), we demonstrate a localized, programmable, and biocompatible encapsulation approach to graft DNA polymers onto live cells. Further guided by two mutually aided enzymatic reactions, the grafted DNA polymers are assembled into DNA polymer cocoons at the cell surface. Therefore, the coating of bacteria, yeast, and mammalian cells has been achieved. The capabilities of this approach may offer significant opportunities to engineer cell surfaces and enable the precise manipulation of the encapsulated cells, such as encoding, handling, and sorting, for many biomedical applications.


Assuntos
Células Imobilizadas/citologia , DNA/química , Polímeros/química , Membrana Celular/metabolismo , Sobrevivência Celular , Células Imobilizadas/metabolismo , Humanos , Células MCF-7 , Polimerização
20.
J Agric Food Chem ; 67(32): 8938-8949, 2019 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-31361121

RESUMO

Polymeric pigments formed via ethyl linkages between grape tannins and anthocyanins are important to the development of stable red wine color. To determine the effect of tannin structure on the stability and color properties of ethyl-linked polymeric pigments, tannin fractions with average polymerization between 4 and 43 units were prepared from grape skins and seeds and combined with malvidin-3-glucoside (M3G) in model wine containing acetaldehyde. As tannin molecular mass increased, the reaction rate with M3G increased. Compared with skin tannins of comparable molecular mass, seed tannins reacted more rapidly with M3G but were prone to precipitation. This resulted in a loss of polymeric pigments formed from seed tannins, which was greater as tannin molecular mass increased. Aggregation occurred following the reaction of seed tannin with M3G, concomitant with precipitation. The aggregation-precipitation phenomenon was not observed for skin tannin-derived pigments, indicating a greater stability in solution than those formed from seed tannins.


Assuntos
Acetaldeído/química , Antocianinas/química , Pigmentos Biológicos/química , Extratos Vegetais/química , Sementes/química , Taninos/química , Vitis/química , Precipitação Química , Cor , Frutas/química , Cinética , Peso Molecular , Polimerização , Polímeros/química
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA