Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 777
Filtrar
Mais filtros










Intervalo de ano de publicação
1.
Nucleic Acids Res ; 47(16): 8860-8873, 2019 09 19.
Artigo em Inglês | MEDLINE | ID: mdl-31310308

RESUMO

Interactions between proteins and DNA are crucial for all biological systems. Many studies have shown the dependence of protein-DNA interactions on the surrounding salt concentration. How these interactions are maintained in the hypersaline environments that halophiles inhabit remains puzzling. Towards solving this enigma, we identified the DNA motif recognized by the Halobactrium salinarum ROS-dependent transcription factor (hsRosR), determined the structure of several hsRosR-DNA complexes and investigated the DNA-binding process under extreme high-salt conditions. The picture that emerges from this work contributes to our understanding of the principles underlying the interplay between electrostatic interactions and salt-mediated protein-DNA interactions in an ionic environment characterized by molar salt concentrations.


Assuntos
Proteínas Arqueais/química , DNA Arqueal/química , Halobacterium salinarum/genética , Cloreto de Potássio/química , Tolerância ao Sal/genética , Fatores de Transcrição/química , Proteínas Arqueais/genética , Proteínas Arqueais/metabolismo , Sequência de Bases , Sítios de Ligação , Clonagem Molecular , Cristalografia por Raios X , DNA Arqueal/genética , DNA Arqueal/metabolismo , Expressão Gênica , Vetores Genéticos/química , Vetores Genéticos/metabolismo , Halobacterium salinarum/metabolismo , Haloferax/genética , Haloferax/metabolismo , Cinética , Modelos Moleculares , Conformação de Ácido Nucleico , Cloreto de Potássio/metabolismo , Ligação Proteica , Conformação Proteica em alfa-Hélice , Conformação Proteica em Folha beta , Domínios e Motivos de Interação entre Proteínas , Espécies Reativas de Oxigênio/metabolismo , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Alinhamento de Sequência , Estresse Fisiológico , Termodinâmica , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo
3.
Environ Sci Pollut Res Int ; 26(23): 23279-23291, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31197670

RESUMO

The use of alunite as an adsorbent for the removal of dye was the aim of this report. Mixing the alunite with different salts may allow adsorption with higher efficiency. In the present study, the thermal decomposition product of alunite-potassium chloride mixture (TDPA-KCl) was used efficiently and inexpensively to remove Reactive Blue 49 (RB49) dye. The adsorption capacity of TDPA-KCl was found to be affected by pH, temperature, adsorbent amount, calcination temperature, dye concentration, and ionic strength. The highest RB49 adsorption yield was obtained at an initial pH of 2 and an equilibrium was reached within 20 min using 80 mg of adsorbent. The most suitable kinetic model was found as the pseudo-second-order and compatible isotherm was determined as the Langmuir model. The optimum adsorption capacity was found as 119.10 mg g-1 at 40 °C. ∆G°, ∆H°, and ∆S° values were calculated. A positive value of ∆H° stated that the adsorption is exothermic and spontaneous. In addition, ∆G° showed a more negative value when temperature was increased. Column studies indicated that TDPA-KCl could be effectively used for five cycles without any loss in its desorption potential. Breakthrough studies also supported a favorable adsorption of RB49 onto TDPA-KCl. This study showed that TDPA-KCl is a practical, efficient, and inexpensive adsorbent to remove reactive dyes from wastewater.


Assuntos
Compostos de Alumínio/química , Corantes/análise , Cloreto de Potássio/química , Compostos de Potássio/química , Sulfatos/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Temperatura Ambiente , Têxteis , Águas Residuárias/química
4.
Meat Sci ; 156: 205-213, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31202095

RESUMO

The effect of partial replacement of NaCl by using sodium substitutes (SS) on the physical, microbial and sensory characteristics of Harbin dry sausage was investigated. There were three salt formulations, including control (100% NaCl), NaCl partly substituted by KCl (SS1) (70% NaCl and 30% KCl), and NaCl partly substituted by KCl combined with other components (SS2) (70% NaCl, 20% KCl, 3.5% maltodextrin, 4% L-Lys, 1% L-Ala, 0.5% citric acid and 1% Ca-lactate). After a 12-day fermentation, the higher moisture content and Aw and lower pH were found in the SS2 treatment, compared to the control and SS1 treatments (P < .05). A decreased microbial diversity during fermentation was found in all sausages, and Staphylococcus spp. and Lactobacillus spp. became the dominant genera. Additionally, the SS2 treatment showed a higher L*-value and lower hardness and chewiness values (P < .05). Therefore, the formulation of SS2 could achieve a NaCl reduction of 30% in Harbin dry sausages with a better sensory acceptability.


Assuntos
Produtos da Carne/análise , Cloreto de Sódio na Dieta/análise , Animais , Cor , Feminino , Fermentação , Manipulação de Alimentos , Humanos , Concentração de Íons de Hidrogênio , Lactobacillus , Masculino , Produtos da Carne/microbiologia , Cloreto de Potássio/química , Staphylococcus , Suínos , Paladar
5.
Anaesthesia ; 74(11): 1374-1380, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31066048

RESUMO

The use of uncoated aluminium-heated plates in an intravenous fluid-warming system has been shown to produce high levels of aluminium in Sterofundin 1/1E, a balanced crystalloid solution. However, the effect of this fluid-warming device on other balanced crystalloid solutions and blood products has not been studied. Using mass spectrometry we measured aluminium levels in Plasma-Lyte 148, compound sodium lactate solution, 4% human albumin solution, expired resuspended packed red cells and fresh frozen plasma that were pumped through an enFlow® fluid-warming system at 2 ml.min-1 . Samples were taken at baseline before heating and then at 10-min intervals up to 60 min with the system set to warm the fluids to 40 °C. High concentrations of aluminium were found for Plasma-Lyte 148 and compound sodium lactate solutions (mean (SD) 223 (0.6) µmol.l-1 and 163 (0.2) µmol.l-1 at 60 min, respectively); both concentrations were significantly greater than the United States Food and Drug Administration recommended maximum limit for aluminium in intravenous nutrition of 25 µg.l-1 (0.9 µmol.l-1 ). Lower aluminium levels were found in 4% human albumin solutions, expired resuspended red cells and fresh frozen plasma at 60 min (mean (SD) 5.7 (0.1) µmol.l-1 , 2.7 (0.0) µmol.l-1 and 2.3 (0.4) µmol.l-1 , respectively). The process allowing addition of aluminium to be added to Sterofundin 1/1E by the enFlow fluid warmer also occurs in Plasma-Lyte 148 and compound sodium lactate solutions and to a lesser degree in blood products. The exact mechanism facilitating this process and its clinical significance remain unclear.


Assuntos
Alumínio/metabolismo , Análise Química do Sangue/métodos , Soluções Cristaloides/química , Calefação/instrumentação , Desenho de Equipamento , Eritrócitos/química , Gluconatos/química , Humanos , Soluções Isotônicas/química , Cloreto de Magnésio/química , Espectrometria de Massas/métodos , Plasma/química , Cloreto de Potássio/química , Albumina Sérica Humana/química , Acetato de Sódio/química , Cloreto de Sódio/química , Lactato de Sódio/química , Fatores de Tempo
6.
Pharm Res ; 36(7): 98, 2019 May 13.
Artigo em Inglês | MEDLINE | ID: mdl-31087169

RESUMO

PURPOSE: To study the effect of mannitol or trehalose on the crystallization behavior of solutes in phosphate buffered saline (PBS) when the solutions were frozen and freeze-dried. METHODS: PBS (pH 7.5 at RT) either alone, or with trehalose (5% w/v) or mannitol (1% w/v), were frozen and characterized using low temperature differential scanning calorimetry (DSC), X-ray diffractometry (XRD), and pH measurement. Freeze dried lyophiles were characterized by XRD. RESULTS: In the absence of cosolutes, upon freezing PBS, a pH shift of ~ 4 units was observed due to crystallization of Na2HPO4•12H2O. XRD indicated sequential crystallization of Na2HPO4•12H2O, NaCl•2H2O and KCl during cooling. When the frozen solutions were heated, two eutectics were observed - the first at ~ -24°C (ternary, NaCl•2H2O-KCl-ice) and the second at ~ -22°C (binary, NaCl•2H2O-ice). Trehalose completely inhibited buffer salt crystallization, whereas mannitol suppressed it partially thereby attenuating the magnitude of pH shift. The two eutectic meltings were also suppressed by the cosolutes. XRD of final lyophiles from PBS alone revealed peaks of anhydrous Na2HPO4, NaCl, and KCl. Trehalose rendered the lyophiles completely XRD amorphous, whereas in presence of mannitol, all the solutes except KH2PO4 crystallized. CONCLUSIONS: Freezing of PBS solution caused a pronounced pH shift due to selective crystallization of Na2HPO4•12H2O. The addition of trehalose or mannitol suppressed the buffer salt crystallization and attenuated the magnitude of pH shift. The potential instability of biologics due to pH shift in PBS, can be potentially mitigated with the cosolutes.


Assuntos
Manitol/química , Fosfatos/química , Solução Salina/química , Trealose/química , Tampões (Química) , Cristalização , Liofilização , Congelamento , Concentração de Íons de Hidrogênio , Cloreto de Potássio/química , Cloreto de Sódio/química , Temperatura Ambiente
7.
Meat Sci ; 156: 33-43, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31125945

RESUMO

The effects of partially replacing NaCl with sodium substitutes (SS) on the lipid and protein oxidation and flavor development of Harbin dry sausage was investigated. There were three salt formulations, including a control (100% NaCl), NaCl partially substituted with KCl (SS1) (70% NaCl and 30% KCl), and NaCl partially substituted with KCl combined with other components (SS2) (70% NaCl, 20% KCl, 4% lysine, 1% alanine, 0.5% citric acid, 1% Ca-lactate and 3.5% maltodextrin). The levels of lipid and protein oxidation increased in all sausages during fermentation (P < 0.05). In addition, lower oxidation of lipids and proteins were found in the SS2 treatment (P < 0.05) due to the lower NaCl concentration. The SS, especially the SS2, promoted the formation of volatile compounds originated from carbohydrate and amino acid metabolism, ß-lipid oxidation and esterification; however, this substitute inhibited the formation of volatile compounds originated from lipid autooxidation (P < 0.05). Overall, SS2 could improve the flavor development of Harbin dry sausage and reduce NaCl by 30%.


Assuntos
Manipulação de Alimentos/métodos , Produtos da Carne/análise , Cloreto de Sódio na Dieta , Animais , Fermentação , Aromatizantes/química , Lipídeos/química , Oxirredução , Cloreto de Potássio/química , Proteínas/química , Suínos , Paladar
8.
PLoS One ; 14(3): e0213598, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30901332

RESUMO

Phosphorylation of the C-terminal domain (CTD) of the large subunit of human RNA polymerase II (Pol II) is regulated during the transcription cycle by the combined action of specific kinases and phosphatases. Pol II enters into the preinitiation complex (PIC) unphosphorylated, but is quickly phosphorylated by Cdk7 during initiation. How phosphatases alter the pattern and extent of CTD phosphorylation at this early stage of transcription is not clear. We previously demonstrated the functional association of an early-acting, magnesium-independent phosphatase with early elongation complexes. Here we show that Ssu72 is responsible for that activity. We found that the phosphatase enters the transcription cycle during the formation of PICs and that Ssu72 is physically associated with very early elongation complexes. The association of Ssu72 with elongation complexes was stable to extensive washing with up to 200 mM KCl. Interestingly, Ssu72 ceased to function on complexes that contained RNA longer than 28 nt. However, when PICs were washed before initiation, the strict cutoff at 28 nt was lost. This suggests that factor(s) are important for the specific regulation of Ssu72 function during the transition between initiation and pausing. Overall, our results demonstrate when Ssu72 can act on early transcription complexes and suggest that Ssu72 may also function in the PIC prior to initiation.


Assuntos
Proteínas de Transporte/química , RNA Polimerase II/química , Elongação da Transcrição Genética , Iniciação da Transcrição Genética , Proteínas de Transporte/metabolismo , Quinases Ciclina-Dependentes/química , Quinases Ciclina-Dependentes/metabolismo , Humanos , Fosforilação , Cloreto de Potássio/química , Domínios Proteicos , RNA Polimerase II/metabolismo
9.
Environ Geochem Health ; 41(5): 2081-2091, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30838487

RESUMO

This study evaluated the feasibility of combining potassium chloride (KCl) leaching and electrokinetic (EK) treatment for the remediation of cadmium (Cd) and other metals from contaminated soils. KCl leaching was compared at three concentrations (0.2%, 0.5%, and 1% KCl). EK treatment was conducted separately to migrate the metals in the topsoil to the subsoil. The combined approach using KCl leaching before or after EK treatment was compared. For the single vertical EK treatment, the removal of Cd, lead (Pb), copper (Cu) and zinc (Zn) from the topsoil (0-20 cm) was 9.38%, 4.80%, 0.95%, and 10.81%, respectively. KCl leaching at 1% KCl removed 84.06% Cd, 9.95% Pb, 4.34% Cu, and 19.93% Zn from the topsoil, with higher removal efficiency than that of the 0.2% and 0.5% KCl leaching treatments. By combining the KCl leaching and EK treatment, the removal efficiency of heavy metals improved, in particular for the 1% KCl + EK treatment, where the removal rate of Cd, Pb, Cu, and Zn from the upper surface soil reached 97.79%, 17.69%, 14.37%, and 41.96%, respectively. Correspondingly, the soil Cd content decreased from 4 to 0.21 mg/kg, and was below the Chinese standard limit of 0.3 mg/kg soil. These results indicate that 1% KCl + EK treatment is a good combination technique to mitigate Cd pollution from contaminated soils used for growing rice and leafy vegetables.


Assuntos
Cádmio/isolamento & purificação , Recuperação e Remediação Ambiental/métodos , Cloreto de Potássio/química , Poluentes do Solo/isolamento & purificação , Cádmio/análise , Cádmio/química , Técnicas Eletroquímicas , Poluição Ambiental/prevenção & controle , Metais Pesados/análise , Metais Pesados/química , Metais Pesados/isolamento & purificação , Solo/química , Poluentes do Solo/análise , Poluentes do Solo/química
10.
Biomolecules ; 9(2)2019 02 14.
Artigo em Inglês | MEDLINE | ID: mdl-30769878

RESUMO

Amyloid fibrils, highly ordered protein aggregates, play an important role in the onset of several neurological disorders. Many studies have assessed amyloid fibril formation under specific solution conditions, but they all lack an important phenomena in biological solutions-buffer specific effects. We have focused on the formation of hen egg-white lysozyme (HEWL) fibrils in aqueous solutions of different buffers in both acidic and basic pH range. By means of UV-Vis spectroscopy, fluorescence measurements and CD spectroscopy, we have managed to show that fibrillization of HEWL is affected by buffer identity (glycine, TRIS, phosphate, KCl-HCl, cacodylate, HEPES, acetate), solution pH, sample incubation (agitated vs. static) and added excipients (NaCl and PEG). HEWL only forms amyloid fibrils at pH = 2.0 under agitated conditions in glycine and KCl-HCl buffers of high enough ionic strength. Phosphate buffer on the other hand stabilizes the HEWL molecules. Similar stabilization effect was achieved by addition of PEG12000 molecules to the solution.


Assuntos
Amiloide/síntese química , Muramidase/síntese química , Acetatos/química , Amiloide/química , Amiloide/metabolismo , Animais , Tampões (Química) , Ácido Cacodílico/química , Glicina/química , Ácido Clorídrico/química , Concentração de Íons de Hidrogênio , Muramidase/química , Muramidase/metabolismo , Fosfatos/química , Cloreto de Potássio/química
11.
Molecules ; 24(4)2019 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-30781833

RESUMO

Enzymatic activity assays are essential and critical for the study of enzyme kinetics. Adenylate kinase (Adk) plays a fundamental role in cellular energy and nucleotide homeostasis. To date, assays based on different principles have been used for the determination of Adk activity. Here, we show a spectrophotometric analysis technique to determine Adk activity with bromothymol blue as a pH indicator. We analyzed the effects of substrates and the pH indicator on the assay using orthogonal design and then established the most optimal assay for Adk activity. Subsequently, we evaluated the thermostability of Adk and the inhibitory effect of KCl on Adk activity with this assay. Our results show that this assay is simple, rapid, and precise. It shows great potential as an alternative to the conventional Adk activity assay. Our results also suggest that orthogonal design is an effective approach, which is very suitable for the optimization of complex enzyme reaction conditions.


Assuntos
Adenilato Quinase/química , Espectrofotometria/métodos , Azul de Bromotimol/química , Homeostase , Concentração de Íons de Hidrogênio , Cinética , Fosforilação , Cloreto de Potássio/química
12.
J Agric Food Chem ; 67(49): 13718-13727, 2019 Dec 11.
Artigo em Inglês | MEDLINE | ID: mdl-30614702

RESUMO

The effects of chelating agents and salts on the interfacial characteristics and oxidative stability of oil-in-water emulsions containing an endogenous concentration of metal ions were investigated. Emulsions were fabricated by high-pressure homogenization of 10% oil phase (sacha inchi oil) and 90% aqueous phase (1% Tween 60 in phosphate buffer solution, pH 7, 50 mM). The oxidative stability of the emulsions was characterized by measuring peroxide values and thiobarbituric acid reactive substances throughout storage. Endogenous iron and copper ion levels in the emulsions were detected by atom absorption spectroscopy as 1.99 and 0.86 ppm, respectively. Incorporation of chelating agents, either ethylenediaminetetraacetic acid or sodium citrate, into the emulsions effectively inhibited lipid oxidation, showing that even these low levels of endogenous metal ions ( parts per million) were sufficient to promote oxidation. Conversely, the addition of monovalent salts, NaCl or KCl, slightly increased the rate of lipid oxidation in the emulsions, which was attributed to their impact on the physical properties of the surfactant layer at the oil droplet surfaces. The impact of chelating agents and salts on the electrical characteristics (ξ potential) and relaxation time (TR) of the surfactant-coated lipid droplets were characterized by particle electrophoresis and nuclear magnetic resonance spectroscopy, respectively. The chelating agents and salts altered the surface potential of the droplets, indicative of a change in the adsorption of metal ions to the droplet surfaces. Moreover, they altered the arrangement of surface-active molecules at the droplet surfaces, thereby impacting the contact of pro-/antioxidants with the oil phase. These results have important implications for the formulation of emulsion-based materials that are more stable to lipid oxidation.


Assuntos
Quelantes/química , Lipídeos/química , Óleos/química , Sais/química , Água/química , Adsorção , Emulsões/química , Oxirredução , Cloreto de Potássio/química , Cloreto de Sódio/química , Substâncias Reativas com Ácido Tiobarbitúrico/química
13.
Paediatr Anaesth ; 29(2): 186-192, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30472805

RESUMO

BACKGROUND: Plasma-Lyte 148® is a balanced, crystalloid intravenous (IV) fluid which is both calcium-free and isotonic. It prevents the hyperchloremic metabolic acidosis and iatrogenic hyponatremia seen with use of 0.9% sodium chloride and hypotonic solutions, respectively. However, data on compatibility with commonly used drugs are lacking. AIMS: To investigate the stability of Plasma-Lyte 148® and Plasma-Lyte 148® + 5% Glucose with eight commonly used therapeutic agents when compared with 5% glucose and 0.9% sodium chloride as diluents. We aimed to provide vital data which may facilitate the introduction of what appears to be a safer and more economic fluid. METHODS: Plasma-Lyte 148® and Plasma-Lyte 148® + 5% Glucose were mixed with morphine, midazolam, fentanyl, ketamine, clonidine, aminophylline, salbutamol, and furosemide at set concentrations. Comparisons were made to 0.9% sodium chloride and 5% glucose fluid controls. Six repeats of each IV fluid and drug admixture were analyzed through high-performance liquid chromatography at three time points: 0, 2, and 24 hours. A concentration change of <5% was defined as chemically stable. Physical stability was assessed by observation of precipitate formation or color change. pH changes were measured using a Fisherbrand Hydrus 300 pH meter. RESULTS: Relative to starting concentration, all drugs except midazolam were stable to ±3%. All examined therapeutic agents were chemically stable at 2 and 24 hours relative to control solutions. No precipitate formed in any of the samples. All Plasma-Lyte 148® and Plasma-Lyte 148® + 5% Glucose drug admixtures remained in a safe, peripheral administration pH range of 5-9 and were closer to the pH of blood than standard fluid-drug admixtures. CONCLUSION: Morphine, fentanyl, ketamine, salbutamol, aminophylline, and clonidine are stable for 24 hours when mixed with Plasma-Lyte 148® and Plasma-Lyte 148®+5% Glucose for administration at concentrations equivalent to those found at a typical Y-site with maintenance fluid. Furosemide is stable at lower concentrations than those seen at a Y-site, but midazolam displayed instability.


Assuntos
Administração Intravenosa , Incompatibilidade de Medicamentos , Estabilidade de Medicamentos , Gluconatos/administração & dosagem , Gluconatos/química , Glucose , Concentração de Íons de Hidrogênio , Cloreto de Magnésio/administração & dosagem , Cloreto de Magnésio/química , Soluções Oftálmicas/administração & dosagem , Soluções Oftálmicas/química , Substitutos do Plasma/uso terapêutico , Cloreto de Potássio/administração & dosagem , Cloreto de Potássio/química , Acetato de Sódio/administração & dosagem , Acetato de Sódio/química , Cloreto de Sódio/administração & dosagem , Cloreto de Sódio/química
14.
Food Chem ; 273: 99-105, 2019 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-30292382

RESUMO

Wet salting is an old preservation method however the NaCl has been frequently associated to high blood pressure issues. The KCl has been used as partial replacement without affecting the acceptability of the final product. In this study, the simultaneous diffusion of NaCl and KCl in champignon mushrooms in static brine and brine under agitation was modeled based on the generalization of Fick's second diffusion law and simulated using the finite element method. Main and crossed diffusion coefficients, as well as the Biot number, were determined using the super modified simplex optimization method by means of percentage error minimization. Deviations between the simulated and experimental data were 5.78% for NaCl and 4.78% for KCl in static brine and 4.95% for NaCl and 4.35% for KCl in brine with agitation and, the main diffusion coefficients 2.692 × 10-10 m2s-1 for sodium and 2.953 × 10-10 m2s-1 for potassium were obtained.


Assuntos
Agaricus/química , Manipulação de Alimentos/métodos , Modelos Teóricos , Cloreto de Potássio/química , Cloreto de Sódio/química , Difusão , Potássio/química , Sais , Sódio/química
15.
Radiat Prot Dosimetry ; 184(1): 90-97, 2019 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-30428076

RESUMO

The aim of this work was to investigate the optically-stimulated luminescence (OSL) properties of potassium chloride (KCl) and its potential use in radiation dosimetry. The optimal condition for OSL readout with blue light stimulation were designated using a commercially available Risø TL/OSL reader. KCl was studied in three sample forms: crystals, powder and pellets. The following OSL characteristics were determined: signal reproducibility, OSL measurement-induced sensitivity changes, temperature dependence of OSL and signal stability over time. The results show a high reproducibility of KCl samples and strong sensitivity changes, which can be corrected for by using a test-dose. The long-term OSL studies confirmed the occurrence of both inverse fading and fading phenomena in KCl. In addition, a comparison with corresponding measurements using sodium chloride (NaCl) were carried out. Although it was confirmed that NaCl is more suitable for dosimetry, there might be benefits of combining NaCl with KCl for more accurate absorbed dose determinations.


Assuntos
Dosimetria por Luminescência Estimulada Opticamente/métodos , Cloreto de Potássio/química , Exposição à Radiação/análise , Radiação Ionizante , Radiometria/métodos , Cloreto de Sódio/química , Humanos , Luminescência , Medições Luminescentes , Dosimetria por Luminescência Estimulada Opticamente/instrumentação , Cloreto de Potássio/efeitos da radiação , Doses de Radiação , Radiometria/instrumentação , Cloreto de Sódio/efeitos da radiação
16.
Meat Sci ; 150: 14-22, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30562639

RESUMO

This work investigated protein oxidation, proteolysis and their interrelationship during the manufacturing process of low-sodium Chinese traditional bacon. The bacons were prepared by four different salting treatments: substituting sodium chloride (NaCl) using 0, 30, 50, and 70% of potassium chloride (KCl). Protein oxidation was evaluated by total carbonylation, thiol oxidation, and tryptophan fluorescence changes. Proteolysis was detected by non-protein nitrogen, free amino acid, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In the manufacturing process of low-sodium Chinese bacon, protein oxidation and protein proteolysis were simultaneously observed. Electrophoresis pattern showed that 70% substitution of KCl could promote proteolysis, meanwhile, protein oxidation possibly facilitated by 70% KCl replacement resulted in reduced tryptophan fluorescence and increased total carbonyl content. Additionally, a good correlation between protein oxidation and proteolysis was observed.


Assuntos
Produtos da Carne/análise , Cloreto de Potássio/química , Proteínas/química , Proteólise , Cloreto de Sódio/química , Animais , Manipulação de Alimentos/métodos , Oxirredução , Sus scrofa
17.
Food Chem ; 266: 110-118, 2018 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-30381165

RESUMO

The density (ρ), speed of sound (u), viscosity (η) and enthalpy of dilution (q) measurements for methylxanthines (caffeine, theophylline and theobromine) in aqueous medium and in aqueous solutions of (0.10-1.00) mol·kg-1 KCl covering a temperature range T = (288.15-318.15) K and at p = 101.325 kPa have been accomplished using a density and sound velocity meter, Micro-Ubbelohde type capillary viscometer and Isothermal Titration Calorimetry, respectively. Transfer parameters evaluated from the data suggest that competition among various interactions exists at low and high molalities of KCl(aq.) solutions. The increase in bitterness and decrease in hydration number of methylxanthines with the mB values have been observed. The dehydration effect of KCl(aq.) at low molalities on the methylxanthines has also been established using ITC. Positive change in the chemical shifts (1H NMR) and increase in absorption intensity (UV-vis) of methylxanthines in the presence of KCl(aq.) further support our results.


Assuntos
Cafeína/química , Cloreto de Potássio/química , Teobromina/química , Teofilina/química , Calorimetria , Espectroscopia de Ressonância Magnética , Espectrofotometria , Temperatura Ambiente , Termodinâmica , Viscosidade , Água/química
18.
Nano Lett ; 18(12): 7816-7821, 2018 12 12.
Artigo em Inglês | MEDLINE | ID: mdl-30456959

RESUMO

Biological membranes possess intrinsic asymmetry. This asymmetry is associated not only with leaflet composition in terms of membrane species but also with differences in the cytosolic and periplasmic solutions containing macromolecules and ions. There has been a long quest for understanding the effect of ions on the physical and morphological properties of membranes. Here, we elucidate the changes in the mechanical properties of membranes exposed to asymmetric buffer conditions and the associated curvature generation. As a model system, we used giant unilamellar vesicles (GUVs) with asymmetric salt and sugar solutions on the two sides of the membrane. We aspirated the GUVs into micropipettes and attached small beads to their membranes. An optical tweezer was used to exert a local force on a bead, thereby pulling out a membrane tube from the vesicle. The assay allowed us to measure the spontaneous curvature and the bending rigidity of the bilayer in the presence of different ions and sugar. At low sugar/salt (inside/out) concentrations, the membrane spontaneous curvature generated by NaCl and KCl is close to zero, but negative in the presence of LiCl. In the latter case, the membrane bulges away from the salt solution. At high sugar/salt conditions, the membranes were observed to become more flexible and the spontaneous curvature was enhanced to even more negative values, comparable to those generated by some proteins. Our findings reveal the reshaping role of alkali chlorides on biomembranes.


Assuntos
Membranas Artificiais , Cloreto de Potássio/química , Cloreto de Sódio/química , Lipossomas Unilamelares/química
19.
J Phys Chem B ; 122(49): 11662-11676, 2018 12 13.
Artigo em Inglês | MEDLINE | ID: mdl-30351123

RESUMO

We introduce a global, collective coordinate bias into molecular dynamics simulations that partially unfolds a protein, in order to predict misfolding-specific epitopes based on the regions that locally unfold. Several metrics are used to measure local disorder, including solvent exposed surface area (SASA), native contacts ( Q), and root mean squared fluctuations (RMSF). The method is applied to Cu, Zn superoxide dismutase (SOD1). For this protein, the processes of monomerization, metal loss, and conformational unfolding due to microenvironmental stresses are all separately taken into account. Several misfolding-specific epitopes are predicted, and consensus epitopes are calculated. These predicted epitopes are consistent with the "lower-resolution" peptide sequences used to raise disease-specific antibodies, but the epitopes derived from collective coordinates contain shorter, more refined sequences for the key residues constituting the epitope.


Assuntos
Epitopos/química , Dobramento de Proteína , Superóxido Dismutase-1/química , Humanos , Modelos Moleculares , Cloreto de Potássio/química , Cloreto de Sódio/química , Propriedades de Superfície
20.
ACS Sens ; 3(10): 2129-2137, 2018 10 26.
Artigo em Inglês | MEDLINE | ID: mdl-30284814

RESUMO

Solid-state nanopores have a huge potential in upcoming societal challenging applications in biotechnologies, environment, health, and energy. Nowadays, these sensors are often used within bulky fluidic devices that can cause cross-contaminations and risky nanopore chips manipulations, leading to a short experimental lifetime. We describe the easy, fast, and cheap innovative 3D-printer-helped protocol to manufacture a microfluidic device permitting the reversible integration of a silicon based chip containing a single nanopore. We show the relevance of the shape of the obtained channels thanks to finite elements simulations. We use this device to thoroughly investigate the ionic transport through the solid-state nanopore as a function of applied voltage, salt nature, and concentration. Furthermore, its reliability is proved through the characterization of a polymer-based model of protein-urea interactions on the nanometric scale thanks to a hairy nanopore.


Assuntos
Microfluídica/métodos , Nanoporos , Proteínas/química , Ureia/química , Transporte de Íons , Dispositivos Lab-On-A-Chip , Cloreto de Lítio/química , Cloreto de Potássio/química , Impressão Tridimensional , Conformação Proteica , Reciclagem , Compostos de Silício/química
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA