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1.
Phys Chem Chem Phys ; 22(8): 4788-4792, 2020 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-32068201

RESUMO

Precipitation and dissolution of calcium oxalate monohydrate (CaOx) crystals are relevant due to their major role in kidney stone diseases. To such an extent, small molecules and ions can act as inhibitors to prevent the formation of calcium oxalate monohydrate crystals. Herein, we explored the role of citrate and the counter cation Na+ ions in the dissolution of CaOx crystals. Citrate binds on the Ca2+ sites of the CaOx crystals to form calcium citrate. Dissolution of CaOx increases with the increase in the concentration of citrate ions and time of incubation. We observed that corrugations were formed on the surface of the CaOx crystals after the sodium citrate treatment during the dissolution process. Theoretical studies revealed that Na+ occupies the vacant site of Ca2+ in CaOx making a strain on the surface which leads to the subsequent deformation of the crystal.


Assuntos
Oxalato de Cálcio/química , Citratos/química , Sódio/química , Cristalização
2.
PLoS One ; 15(1): e0227338, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31935229

RESUMO

Soil particles and bound nutrients that erode from agricultural land may end up in surface waters and cause undesirable changes to the environment. Various measures, among them constructed wetlands have been proposed as mitigation, but their efficiency varies greatly. This work was motivated by the assumption that the induced coagulation of particles may accelerate sedimentation in such wetlands and by that help reduce the amount of material that is lost from the vicinity of the diffuse source. Our specific aim was to laboratory-test the effectiveness of various salt-based coagulants in accelerating the process of sedimentation. We tested the effect of Na+, Mg2+, Ca2+, Fe3+ and Al3+ cations in 10, 20, 40 and 80 mg L-1 doses added to a soil solution in select, soluble forms of their chlorides, sulphates and hydroxides. We mixed such salts with 1 gram of physically dispersed, clay and silt rich (>85% in total) soil material in 500 mL of solution and used time-lapse photography and image analysis to evaluate the progress of sedimentation over 3 hours. We found that 20-40 mg L-1 doses of Mg2+, Ca2+ in their chloride or sulphate forms appeared to provide the best consensus in terms of efficiently accelerating sedimentation using environmentally present and acceptable salts but keeping their dosage to a minimum. Comprehensive in-field efficiency and environmental acceptability testing is warranted prior to any practical implementation, as well as an assessment of small scale economic and large-scale environmental benefits by retaining soil and nutrients at/near the farm.


Assuntos
Agricultura , Metais/química , Solo/química , Poluentes Químicos da Água/química , Cloretos/química , Humanos , Sódio/química , Soluções/química , Sulfatos/química , Suspensões/química , Água/química , Áreas Alagadas
3.
Chemosphere ; 246: 125710, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31891842

RESUMO

The aim of this study was to investigate the adsorption of Ni(II) from aqueous solutions onto Cloisite Na+ clay. The effects of the initial concentration of Ni(II), adsorbent dose, pH, and temperature on adsorption capacity were studied using response surface methodology. A second-order regression model was determined based on the experimental results. Analysis of variance used to evaluate the individual and combined effects of process variables showed that initial Ni(II) concentration and adsorbent dose were more significant than solution pH and temperature. Moreover, the interaction effects of the initial concentration of nickel and the adsorbent dose, as well as the solution pH and adsorbent dose were significant. High coefficient of determination (R2 = 0.93) and low probability values signify the validity of the model for predicting the adsorption capacity of Cloisite Na+ for Ni(II) ions. The optimal conditions for pH and adsorbent dose were found to be 6.9 and 0.21 g/L, respectively at a constant temperature of 25 °C and initial Ni(II) concentration of 50 mg/L. Under these conditions, the adsorption capacity of clay was found to be 31.43 mg/g. Moreover, the adsorption isotherms results indicated that these data could be best fitted to the Langmuir isotherm model (R2 = 0.99). The Langmuir maximum adsorption capacity was estimated to be 32.05 mg/g for an adsorbent dose of 0.2 g/L at pH 7 and 25 °C. In conclusion, the results showed that Cloisite Na+ clay can be utilized as an effective adsorbent for the removal of Ni(II) from aqueous solutions.


Assuntos
Argila/química , Níquel/química , Sódio/química , Poluentes Químicos da Água/química , Adsorção , Concentração de Íons de Hidrogênio , Íons , Cinética , Modelos Químicos , Temperatura , Água , Purificação da Água/métodos
4.
Food Chem ; 310: 125815, 2020 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-31757491

RESUMO

Developing green solvents with low toxicity and low energy consumption is an important issue for edible oil production. In this study, a novel extraction system, specifically a citric acid/citric acid sodium mixture, was developed for oil extraction from seed crops. Peanut and pumpkin seeds were used to evaluate extraction efficiency and more than 70% and 57% oils, respectively, were extracted from peanut and pumpkin seeds at 4 °C. After extraction, the oils floated on the surface of the solution and could be separated from the solvent system without evaporation. The extraction of edible oils was achieved without the use of toxic chemicals or energy-intensive equipment. This study provided a green and efficient method, and showed the potential of the proposed citric acid/citric acid sodium extraction system for production of edible oils from natural sources.


Assuntos
Fracionamento Químico/métodos , Óleos Vegetais/isolamento & purificação , Sementes/química , Solventes/química , Arachis/química , Ácido Cítrico/química , Cucurbita/química , Química Verde , Sódio/química
5.
Forensic Sci Int ; 306: 110044, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31734575

RESUMO

The identification of phenidate new psychoactive substances (NPS) by implementing MS (Mass spectrometry) techniques is a challenging task. Phenidate analogues present information-poor mass spectra, both in GC-EI-MS and LC-ESI-MS/MS of the protonated molecules [M+H]+, with a high abundance fragment/product ion representing the secondary amine-containing residue. This lack of EI-MS and ESI-MS/MS information is attributed to the strong tendency of the amine residue to stabilize the positive charge and leads to unavoidable ambiguity in the identification process. Moreover, thermal decomposition of these compounds occurs in the injection port and/or on the column under standard GC conditions. Herein, we demonstrate how structural information can be attained instantaneously through the LC-ESI-MS/MS fragmentation of the accompanied sodium adducts [M+Na]+. The sodium cation alters the charge distribution during ESI-MS/MS fragmentation, generating a major product ion corresponding to the Na+ adduction of the carbonyl group, providing new structural information of the main core of phenidate derivatives (alkylaryl acetate/acetic acid), enabling their reliable structural elucidation. This quick, simple and easy technique can be implemented to confirm the identity or identify various structurally related phenidate analogues in forensic toxicology and doping analysis without the need for sample handling.


Assuntos
Íons/química , Metilfenidato/análogos & derivados , Metilfenidato/química , Sódio/química , Cromatografia Líquida , Cromatografia Gasosa-Espectrometria de Massas , Humanos , Estrutura Molecular , Espectrometria de Massas por Ionização por Electrospray
6.
Am J Nurs ; 120(1): 51-56, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31880730

RESUMO

Nurses need to have a firm grasp of normal and pathophysiological mechanisms of sodium and water balance to fully understand assessment findings and establish a rationale for a patient's plan of care. While multiple mechanisms control sodium and water balance, antidiuretic hormone and aldosterone are the most important hormonal influences. This article, the first in a new series designed to improve nurses' understanding of the physiological abnormalities underlying many disorders, reviews the common etiologies and symptoms of hyponatremia and hypernatremia, as well as the role of nursing care in patients with imbalances of sodium and water. Case studies guide the reader through relevant medical history and examination findings to an understanding of both the nursing and medical plans of care.


Assuntos
Composição Corporal/fisiologia , Hipernatremia/fisiopatologia , Hiponatremia/fisiopatologia , Sódio/química , Equilíbrio Hidroeletrolítico/fisiologia , Água/química , Humanos
7.
Nucleic Acids Res ; 48(3): 1406-1422, 2020 02 20.
Artigo em Inglês | MEDLINE | ID: mdl-31863586

RESUMO

Recent advances in gene editing have been enabled by programmable nucleases such as transcription activator-like effector nucleases (TALENs) and CRISPR-Cas9. However, several open questions remain regarding the molecular machinery in these systems, including fundamental search and binding behavior as well as role of off-target binding and specificity. In order to achieve efficient and specific cleavage at target sites, a high degree of target site discrimination must be demonstrated for gene editing applications. In this work, we studied the binding affinity and specificity for a series of TALE proteins under a variety of solution conditions using in vitro fluorescence methods and molecular dynamics (MD) simulations. Remarkably, we identified that TALEs demonstrate high sequence specificity only upon addition of small amounts of certain divalent cations (Mg2+, Ca2+). However, under purely monovalent salt conditions (K+, Na+), TALEs bind to specific and non-specific DNA with nearly equal affinity. Divalent cations preferentially bind to DNA over monovalent cations, which attenuates non-specific interactions between TALEs and DNA and further stabilizes specific interactions. Overall, these results uncover new mechanistic insights into the binding action of TALEs and further provide potential avenues for engineering and application of TALE- or TALEN-based systems for genome editing and regulation.


Assuntos
Cálcio/química , Cátions Bivalentes/química , DNA/química , Magnésio/química , Nucleases dos Efetores Semelhantes a Ativadores de Transcrição/química , Sistemas CRISPR-Cas/genética , Proteínas de Ligação a DNA/química , Edição de Genes , Potássio/química , Ligação Proteica , Sódio/química , Soluções/química , Nucleases dos Efetores Semelhantes a Ativadores de Transcrição/metabolismo
8.
Food Chem ; 305: 125456, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31525594

RESUMO

This work developed a new technique and an application of an existing approach to determine sodium in food sauces, involving enthalpimetric reactions in the infrared. Infrared Thermometric Titration (TT-IR) was utilized, with simple analyzers and low-cost measurement instruments for the acquisition of the surface temperature generated in the sodium precipitation reaction and development of software for the acquisition and processing of data using Raspberry Pi. The sodium was also quantified by Thermal Infrared Enthalpimetry (TIE), a recently developed technique. The rapid and simple quantification of sodium by the TT-IR and TIE showed the possibility of a selective reaction for sodium, using aluminum nitrate, potassium and ammonium fluoride in an acid medium, with reduction of the reagents and without the digestion step in the sample preparation. The results acquired through TT-IR and TIE corroborated the Flame Atomic Emission Spectrometry (FAES) with 96 to 103% and 95 to 102%, respectively.


Assuntos
Análise de Alimentos/métodos , Raios Infravermelhos , Sódio/análise , Produtos Vegetais/análise , Compostos de Alumínio/química , Limite de Detecção , Nitratos/química , Sódio/química , Espectrofotometria Atômica , Temperatura , Termometria/métodos
9.
Food Chem ; 306: 125622, 2020 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-31610330

RESUMO

This study investigated the potential of pulsed electric field (PEF) as a sodium-reduction strategy for processed meat. Beef jerky was used as a model and prepared using different levels of NaCl, viz. 2.0% (control), 1.2% (T1) and 1.2% along with PEF processing (T2). A significant (p < 0.05) effect of PEF was observed on shear force (N) and toughness (N/mm s) of the products, which was also reflected in sensory scores. No effects for PEF were observed on colour, yield (%) and oxidative and microbial stability. PEF-treated samples (T2) had significantly (p < 0.05) lower sodium content than the control, however, the sensory scores were comparable (p > 0.05) with control and >84% of the panellists preferred T2 samples over T1 for saltiness. Results suggest that PEF treatment improved saltiness by influencing the salt diffusion and sodium delivery that led to better perception during chewing. PEF could be a novel method to produce healthier reduced-sodium meat products.


Assuntos
Produtos da Carne/análise , Carne Vermelha/análise , Sódio/química , Animais , Bovinos , Eletricidade , Manipulação de Alimentos
10.
Food Chem ; 306: 125578, 2020 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-31622835

RESUMO

Oleosomes are storage vehicles of TAGs in plant seeds. They are protected with a phospholipid-protein monolayer and extracted with alkaline aqueous media; however, pH adjustment intensifies the extraction process. Therefore, the aim of this work was to investigate the extraction mechanism of rapeseed oleosomes at pH 7 and at the presence of monovalent and divalent cations (Na+, K+, Mg2+, and Ca+2). The oleosome yield at pH 9.5 was 64 wt%, while the yield at pH 7 with H2O was just 43 wt.%. The presence of cations at pH 7, significantly enhanced the yield, with K+ giving the highest yield (64 wt.%). The cations affected the oleosome interface and their interactions. The presence of monovalent cations resulted in aggregation and minor coalescence, while divalent cations resulted in extensive coalescence. These results help to understand the interactions of oleosomes in their native matrix and design simple extraction processes at neutral conditions.


Assuntos
Brassica/química , Cálcio/química , Magnésio/química , Extratos Vegetais/química , Potássio/química , Sódio/química , Cátions Bivalentes/química , Cátions Monovalentes/química , Concentração de Íons de Hidrogênio , Gotículas Lipídicas , Sementes/química , Água
11.
Elife ; 82019 12 24.
Artigo em Inglês | MEDLINE | ID: mdl-31868580

RESUMO

Human-based modelling and simulations are becoming ubiquitous in biomedical science due to their ability to augment experimental and clinical investigations. Cardiac electrophysiology is one of the most advanced areas, with cardiac modelling and simulation being considered for virtual testing of pharmacological therapies and medical devices. Current models present inconsistencies with experimental data, which limit further progress. In this study, we present the design, development, calibration and independent validation of a human-based ventricular model (ToR-ORd) for simulations of electrophysiology and excitation-contraction coupling, from ionic to whole-organ dynamics, including the electrocardiogram. Validation based on substantial multiscale simulations supports the credibility of the ToR-ORd model under healthy and key disease conditions, as well as drug blockade. In addition, the process uncovers new theoretical insights into the biophysical properties of the L-type calcium current, which are critical for sodium and calcium dynamics. These insights enable the reformulation of L-type calcium current, as well as replacement of the hERG current model.


Assuntos
Potenciais de Ação/fisiologia , Modelos Cardiovasculares , Miócitos Cardíacos , Algoritmos , Biofísica , Cálcio/química , Cálcio/metabolismo , Canais de Cálcio/química , Canais de Cálcio/metabolismo , Calibragem , Simulação por Computador , Eletrocardiografia , Fenômenos Eletrofisiológicos , Eletrofisiologia , Acoplamento Excitação-Contração , Cardiopatias/fisiopatologia , Ventrículos do Coração/patologia , Humanos , Sódio/química , Sódio/metabolismo
12.
Environ Monit Assess ; 191(12): 754, 2019 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-31734742

RESUMO

In peri-urban areas, the use of wastewater for crop production is a common practice due to water scarcity. Moreover, in the recent years, large quantity of wastewater generation and discharge as industrial effluent in water resources is another issue for reduction of water quality. The leather industries are significantly contributing chromium (Cr) in effluent, whereas, other industries may have salt and cationic load in their discharges are mixed up. Therefore, it is mandatory to study the interactive effect of different effluent constituents on crop plants. In this connection, a pot culture experiment was conducted at the ICAR-Indian Institute of Soil Science, Bhopal to compute the effect of application of calcium (Ca) and sodium (Na) ions on Cr uptake by spinach crop in Vertisol of central India. Three levels of Cr (0, 50, 100 mg kg-1), calcium (0, 2, 4 mM), and sodium (0, 40, 80 mM) were applied in combinations. The spinach variety All Green was used as a test crop and harvested at full maturity. Results showed that application of Ca and Na reduced the Cr uptake in spinach crop. The reduction of Cr uptake was more in the root than shoot. Applied calcium acted as an essential plant nutrient and enhanced the crop biomass. Sole applications of Na adversely affected the crop biomass and Cr uptake in both root and shoot of spinach. In conclusion, application of Ca fertilizers reduced the Cr toxicity in spinach and could be used as a strategy for the safe utilization of tannery industrial effluents for crop production.


Assuntos
Cálcio/química , Cromo/metabolismo , Produção Agrícola/métodos , Sódio/química , Poluentes do Solo/análise , Spinacia oleracea/química , Biomassa , Monitoramento Ambiental , Fertilizantes/análise , Índia , Raízes de Plantas/química , Águas Residuárias/química
13.
Biochemistry (Mosc) ; 84(11): 1280-1295, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31760918

RESUMO

Maintenance of non-equilibrium Na+ and K+ distribution between cytoplasm and extracellular medium suggests existence of sensors responding with conformational transitions to the changes of these monovalent cations' intracellular concentration. Molecular nature of monovalent cation sensors has been established in Na,K-ATPase, G-protein-coupled receptors, and heat shock proteins structural studies. Recently, it was found that changes in Na+ and K+ intracellular concentration are the key factors in the transcription and translation control, respectively. In this review, we summarize results of these studies and discuss physiological and pathophysiological significance of Na+i,K+i-dependent gene expression regulation mechanism.


Assuntos
Potássio/metabolismo , ATPase Trocadora de Sódio-Potássio/metabolismo , Sódio/metabolismo , Animais , Cátions Monovalentes/química , Citoplasma/metabolismo , Proteínas de Choque Térmico/metabolismo , Potássio/química , Biossíntese de Proteínas , Sódio/química , Transcrição Genética
14.
Pharmacol Rev ; 71(4): 571-595, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31551350

RESUMO

Endogenous ions play important roles in the function and pharmacology of G-protein coupled receptors (GPCRs). Historically the evidence for ionic modulation of GPCR function dates to 1973 with studies of opioid receptors, where it was demonstrated that physiologic concentrations of sodium allosterically attenuated agonist binding. This Na+-selective effect was distinct from effects of other monovalent and divalent cations, with the latter usually counteracting sodium's negative allosteric modulation of binding. Since then, numerous studies documenting the effects of mono- and divalent ions on GPCR function have been published. While ions can act selectively and nonselectively at many sites in different receptors, the discovery of the conserved sodium ion site in class A GPCR structures in 2012 revealed the unique nature of Na+ site, which has emerged as a near-universal site for allosteric modulation of class A GPCR structure and function. In this review, we synthesize and highlight recent advances in the functional, biophysical, and structural characterization of ions bound to GPCRs. Taken together, these findings provide a molecular understanding of the unique roles of Na+ and other ions as GPCR allosteric modulators. We will also discuss how this knowledge can be applied to the redesign of receptors and ligand probes for desired functional and pharmacological profiles. SIGNIFICANCE STATEMENT: The function and pharmacology of GPCRs strongly depend on the presence of mono and divalent ions in experimental assays and in living organisms. Recent insights into the molecular mechanism of this ion-dependent allosterism from structural, biophysical, biochemical, and computational studies provide quantitative understandings of the pharmacological effects of drugs in vitro and in vivo and open new avenues for the rational design of chemical probes and drug candidates with improved properties.


Assuntos
Receptores Acoplados a Proteínas-G/antagonistas & inibidores , Receptores Acoplados a Proteínas-G/metabolismo , Sódio/metabolismo , Sítio Alostérico , Ânions/química , Ânions/metabolismo , Sítios de Ligação , Cátions Bivalentes/química , Cátions Bivalentes/metabolismo , Cátions Monovalentes/química , Cátions Monovalentes/metabolismo , Cloretos/química , Cloretos/metabolismo , Cristalografia por Raios X , Humanos , Ligantes , Conformação Proteica , Receptores Acoplados a Proteínas-G/química , Sódio/química , Relação Estrutura-Atividade , Zinco/química , Zinco/metabolismo
15.
Nucleic Acids Res ; 47(19): 10282-10295, 2019 11 04.
Artigo em Inglês | MEDLINE | ID: mdl-31511899

RESUMO

We perform molecular dynamics simulations, based on recent crystallographic data, on the 8-17 DNAzyme at four states along the reaction pathway to determine the dynamical ensemble for the active state and transition state mimic in solution. A striking finding is the diverse roles played by Na+ and Pb2+ ions in the electrostatically strained active site that impact all four fundamental catalytic strategies, and share commonality with some features recently inferred for naturally occurring hammerhead and pistol ribozymes. The active site Pb2+ ion helps to stabilize in-line nucleophilic attack, provides direct electrostatic transition state stabilization, and facilitates leaving group departure. A conserved guanine residue is positioned to act as the general base, and is assisted by a bridging Na+ ion that tunes the pKa and facilitates in-line fitness. The present work provides insight into how DNA molecules are able to solve the RNA-cleavage problem, and establishes functional relationships between the mechanism of these engineered DNA enzymes with their naturally evolved RNA counterparts. This adds valuable information to our growing body of knowledge on general mechanisms of phosphoryl transfer reactions catalyzed by RNA, proteins and DNA.


Assuntos
Biocatálise , DNA Catalítico/química , RNA Catalítico/genética , Soluções/química , Sequência de Bases , Domínio Catalítico/genética , DNA/química , DNA/genética , DNA Catalítico/genética , Cinética , Chumbo/química , Simulação de Dinâmica Molecular , Conformação de Ácido Nucleico , Clivagem do RNA/genética , Sódio/química
16.
Molecules ; 24(16)2019 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-31405189

RESUMO

The influence of Li+, Na+ and Cs+ cations on the surface excess and structure of dodecyl sulfate (DS-) anions at the air-water interface was investigated with the vibrational sum-frequency generation (SFG) and surface tensiometry. Particularly, we have addressed the change in amplitude and frequency of the symmetric S-O stretching vibrations as a function of electrolyte and DS- concentration in the presence of Li+, Na+ and Cs+ cations. For the Li+ and Na+ ions, we show that the resonance frequency is shifted noticeably from 1055 cm-1 to 1063 cm-1 as a function of the surfactants' surfaces excess, which we attribute to the vibrational Stark effect within the static electric field at the air-water interface. For Cs+ ions the resonance frequency is independent of the surfactant concentration with the S-O stretching band centered at 1063 cm-1. This frequency is identical to the frequency at the maximum surface excess when Li+ and Na+ ions are present and points to the ion pair formation between the sulfate headgroup and Cs+ counterions, which reduces the local electric field. In addition, SFG experiments of the O-H stretching bands of interfacial H2O molecules are used in order to calculate the apparent double layer potential and the degree of dissociation between the surfactant head group and the investigated cations. The latter was found to be 12.0%, 10.4% and 7.7% for lithium dodecyl sulfate (LiDS), sodium dodecyl sulfate (SDS) and cesium dodecyl sulfate (CsDS) surfactants, which is in agreement with Collins 'rule of matching water affinities'.


Assuntos
Lítio/química , Dodecilsulfato de Sódio/química , Sódio/química , Tensoativos/química , Álcalis/química , Cátions Monovalentes/química
17.
Molecules ; 24(15)2019 Jul 29.
Artigo em Inglês | MEDLINE | ID: mdl-31362426

RESUMO

One of the most intriguing findings highlighted from G protein-coupled receptor (GPCR) crystallography is the presence, in many members of class A, of a partially hydrated sodium ion in the middle of the seven transmembrane helices (7TM) bundle. In particular, the human adenosine A2A receptor (A2A AR) is the first GPCR in which a monovalent sodium ion was crystallized in a distal site from the canonical orthosteric one, corroborating, from a structural point of view, its role as a negative allosteric modulator. However, the molecular mechanism by which the sodium ion influences the recognition of the A2A AR agonists is not yet fully understood. In this study, the supervised molecular dynamics (SuMD) technique was exploited to analyse the sodium ion recognition mechanism and how its presence influences the binding of the endogenous agonist adenosine. Due to a higher degree of flexibility of the receptor extracellular (EC) vestibule, we propose the sodium-bound A2A AR as less efficient in stabilizing the adenosine during the different steps of binding.


Assuntos
Adenosina/química , Simulação de Acoplamento Molecular , Simulação de Dinâmica Molecular , Receptor A2A de Adenosina/química , Sódio/química , Adenosina/metabolismo , Regulação Alostérica , Sítio Alostérico , Sítios de Ligação , Humanos , Conformação Molecular , Ligação Proteica , Receptor A2A de Adenosina/metabolismo , Sódio/metabolismo
18.
Molecules ; 24(16)2019 Aug 18.
Artigo em Inglês | MEDLINE | ID: mdl-31426565

RESUMO

A series of ditopic ion pair receptors equipped with 4-nitrophenylurea and 1-aza-18-crown-6-ether linked by ortho-(1), meta-(2), and para-(3) substituted benzoic acid were readily synthesized in three steps from commercially available materials. The binding properties of these regioisomeric receptors were determined using UV-vis and 1H NMR spectroscopy in MeCN and in the solid state by single-crystal X-ray diffraction crystallography. The solution studies revealed that, apart from carboxylates, all the anions tested formed stronger complexes in the presence of sodium cations. Receptors 2 and 3 were found to interact with ion pairs with remarkably higher affinity than ortho-substituted 1. 1H NMR titration experiments showed that both urea NH protons interacted with anions with comparable strength in the case of receptors 2 and 3, but only one of the NHs was effective in anion binding in the case of receptor 1. X-ray analysis of the crystal structure of receptor 1 and 1·NaPF6 complex showed that binding was hampered due to the formation of an intramolecular hydrogen bond. Analysis of the crystal structures of 2·NaBr and 3·NaBr complexes revealed that proper mutual orientation of binding domains was responsible for the improved binding of the sodium salts.


Assuntos
Ânions/química , Benzoatos/química , Carbanilidas/química , Éteres de Coroa/química , Receptores Artificiais/química , Sódio/química , Cátions Monovalentes , Cristalografia por Raios X , Ligação de Hidrogênio , Cinética , Espectroscopia de Ressonância Magnética , Modelos Moleculares , Prótons , Receptores Artificiais/síntese química , Estereoisomerismo
19.
Carbohydr Polym ; 223: 115062, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31426967

RESUMO

Nata de coco was chemically modified to afford the bacterial cellulose hydrogels carrying terminal alkynes. The resultant hydrogels were then converted into hydrogels carrying lactosides or those carrying α-2,3-sialyllactosides by the Cu+-catalyzed alkyne-azide cyclization. The stable homo association of the hydrogels carrying lactosides was observed in an aqueous solution containing Ca2+, thereby demonstrating the Ca2+-mediated lactoside-lactoside interactions. Ca2+ also stabilized the hetero associations among the hydrogels carrying lactosides and those carrying α-2,3-sialyllactosides, thereby also demonstrating the Ca2+-induced interactions between the lactosides and the α-2,3-sialyllactosides. The sizes of these hydrogels were of the order of ca. 5 mm, and their associations could thus be readily monitored with the naked eye.


Assuntos
Celulose/química , Hidrogéis/química , Oligossacarídeos/química , Polissacarídeos Bacterianos/química , Alquinos/química , Azidas/química , Cálcio/química , Cocos/química , Cocos/microbiologia , Hidrogéis/síntese química , Magnésio/química , Lectinas de Plantas/química , Ricinus/química , Sódio/química
20.
Nutrients ; 11(8)2019 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-31366099

RESUMO

This report provides an update from the U.S. Department of Agriculture - Centers for Disease Control and Prevention Sentinel Foods Surveillance Program, exploring changes in sodium and related nutrients (energy, potassium, total and saturated fat, and total sugar) in popular, sodium-contributing, commercially processed and restaurant foods with added sodium. In 2010-2013, we obtained 3432 samples nationwide and chemically analyzed 1654 composites plus label information for 125 foods, to determine baseline laboratory and label sodium concentrations, respectively. In 2014-2017, we re-sampled and chemically analyzed 43 of the Sentinel Foods (1181 samples), tested for significant changes of at least ±10% (p < 0.05), in addition to tracking changes in labels for 108 Sentinel Foods. Our results show that the label sodium levels of a majority of the Sentinel Foods had not changed since baseline (~1/3rd of the products reported changes, with twice as many reductions as increases). Laboratory analyses of the 43 Sentinel Foods show that eight foods had significant changes (p < 0.05); sodium content continues to be high and variable, and there was no consistent pattern of changes in related nutrients. Comparisons of changes in labels and laboratory sodium shows consistency for 60% of the products, i.e., similar changes (or no changes) in laboratory and label sodium content. The data from this monitoring program may help public health officials to develop strategies to reduce and monitor sodium trends in the food supply.


Assuntos
Análise de Alimentos , Manipulação de Alimentos , Sódio/química , United States Department of Agriculture , Fast Foods , Rotulagem de Alimentos , Humanos , Valor Nutritivo , Saúde Pública , Restaurantes , Sódio na Dieta , Estados Unidos
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