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1.
Environ Sci Pollut Res Int ; 31(19): 28379-28391, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38536573

RESUMO

To enhance the adsorption performance of municipal sludge biochar on Cd(II), modified sludge biochar was prepared by sodium hydroxide/magnesium chloride (NaOH/MgCl2) graded activation, and the Cd(II) adsorption performance on sludge biochar (BC), NaOH-activated sludge biochar (NBC) and NaOH/MgCl2 activated sludge biochar (NBC-Mg) was investigated. The results showed that NaOH/MgCl2 graded activation upgraded the surface structure and enhanced the graphitization of sludge biochar. The adsorption experiments indicated that the adsorption kinetic and adsorption isotherm for Cd(II) were in accordance with the pseudo second-order kinetic and Langmuir model. The adsorption capacity of NBC-Mg (143.49 mg/g) for Cd(II) was higher than that of BC (50.40 mg/g) and NBC (85.20 mg/g). The mechanism of Cd(II) adsorption included ion exchange, complexation, cation-π interaction, and mineral precipitation. After five regeneration, the removal efficiency of Cd(II) by NBC-Mg remained above 90%. This work indicated that sludge biochar prepared by multistage activation could be an effective material for Cd-containing wastewater treatment.


Assuntos
Cádmio , Carvão Vegetal , Cloreto de Magnésio , Esgotos , Hidróxido de Sódio , Adsorção , Cádmio/química , Carvão Vegetal/química , Esgotos/química , Cloreto de Magnésio/química , Hidróxido de Sódio/química , Cinética , Poluentes Químicos da Água/química
2.
Biochim Biophys Acta Biomembr ; 1864(5): 183883, 2022 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-35181295

RESUMO

Cells are dynamic systems with complex mechanical properties, regulated by the presence of different species of proteins capable to assemble (and disassemble) into filamentous forms as required by different cells functions. Giant unilamellar vesicles (GUVs) of DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine) are systems frequently used as a simplified model of cells because they offer the possibility of assaying separately different stimuli, which is no possible in living cells. Here we present a study of the effect of acting protein on mechanical properties of GUVs, when the protein is inside the vesicles in either monomeric G-actin or filamentous F-actin. For this, rabbit skeletal muscle G-actin is introduced inside GUVs by the electroformation method. Protein polymerization inside the GUVs is promoted by adding to the solution MgCl2 and the ion carrier A23187 to allow the transport of Mg+2 ions into the GUVs. To determine how the presence of actin changes the mechanical properties of GUVs, the vesicles are deformed by the application of an AC electric field in both cases with G-actin and with polymerized F-actin. The changes in shape of the vesicles are characterized by optical microscopy and from them the bending stiffness of the membrane are determined. It is found that G-actin has no appreciable effect on the bending stiffness of DMPC GUVs, but the polymerized actin makes the vesicles more rigid and therefore more resistant to deformations. This result is supported by evidence that actin filaments tend to accumulate near the membrane.


Assuntos
Actinas/química , Dimiristoilfosfatidilcolina/química , Eletricidade , Lipossomas Unilamelares/química , Citoesqueleto de Actina/química , Actinas/metabolismo , Animais , Calcimicina/química , Cloreto de Magnésio/química , Cloreto de Magnésio/metabolismo , Microscopia , Músculo Esquelético/metabolismo , Coelhos , Tensão Superficial , Lipossomas Unilamelares/metabolismo , Viscosidade
3.
Arch Biochem Biophys ; 713: 109045, 2021 11 30.
Artigo em Inglês | MEDLINE | ID: mdl-34627750

RESUMO

The standard isothermal titration calorimetry (ITC) curve, characterized as a typical sigmoid is strictly confined by the so-called c value, which is a ratio of titrand concentration to KD. The proper c value with a range from 5 to 500 is commonly recommended as a standard protocol in routine detection process for acquiring the reliable fitting results in 1:1 binding mode. However, if the c value is less than "1" due to the weak binding or low concentration of analyte, fitting precision gets unstable and susceptible to the data noise. Herein, we first got a deep discussion into the reliability of the fitting procedure for 1:1 binding mode by data simulation, then quantized the effect of several affecting factors on the precision of parameters estimation through mathematical analysis. Finally, we proposed the value of 2~4 times KD for final ligand concentration is optimal for the ITC titration in low c system (c < 1). All the theoretical derivations were further verified by a practical experiment of Magnesium-EDTA binding test.


Assuntos
Calorimetria/estatística & dados numéricos , Ácido Edético/química , Cloreto de Magnésio/química , Termodinâmica
4.
Int J Mol Sci ; 22(20)2021 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-34681747

RESUMO

Hydration plays a fundamental role in DNA structure and functioning. However, the hydration shell has been studied only up to the scale of 10-20 water molecules per nucleotide. In the current work, hydration shells of DNA were studied in a solution by terahertz time-domain spectroscopy. The THz spectra of three DNA solutions (in water, 40 mm MgCl2 and 150 mM KCl) were transformed using an effective medium model to obtain dielectric permittivities of the water phase of solutions. Then, the parameters of two relaxation bands related to bound and free water molecules, as well as to intermolecular oscillations, were calculated. The hydration shells of DNA differ from undisturbed water by the presence of strongly bound water molecules, a higher number of free molecules and an increased number of hydrogen bonds. The presence of 40 mM MgCl2 in the solution almost does not alter the hydration shell parameters. At the same time, 150 mM KCl significantly attenuates all the found effects of hydration. Different effects of salts on hydration cannot be explained by the difference in ionic strength of solutions, they should be attributed to the specific action of Mg2+ and K+ ions. The obtained results significantly expand the existing knowledge about DNA hydration and demonstrate a high potential for using the THz time-domain spectroscopy method.


Assuntos
DNA/química , Espectroscopia Terahertz/métodos , Cátions/química , Ligação de Hidrogênio , Magnésio/química , Cloreto de Magnésio/química , Plasmídeos/genética , Potássio/química , Soluções/química , Água/química
5.
Nucleic Acids Res ; 49(19): 10835-10850, 2021 11 08.
Artigo em Inglês | MEDLINE | ID: mdl-34614184

RESUMO

Liposomes are widely used as synthetic analogues of cell membranes and for drug delivery. Lipid-binding DNA nanostructures can modify the shape, porosity and reactivity of liposomes, mediated by cholesterol modifications. DNA nanostructures can also be designed to switch conformations by DNA strand displacement. However, the optimal conditions to facilitate stable, high-yield DNA-lipid binding while allowing controlled switching by strand displacement are not known. Here, we characterized the effect of cholesterol arrangement, DNA structure, buffer and lipid composition on DNA-lipid binding and strand displacement. We observed that binding was inhibited below pH 4, and above 200 mM NaCl or 40 mM MgCl2, was independent of lipid type, and increased with membrane cholesterol content. For simple motifs, binding yield was slightly higher for double-stranded DNA than single-stranded DNA. For larger DNA origami tiles, four to eight cholesterol modifications were optimal, while edge positions and longer spacers increased yield of lipid binding. Strand displacement achieved controlled removal of DNA tiles from membranes, but was inhibited by overhang domains, which are used to prevent cholesterol aggregation. These findings provide design guidelines for integrating strand displacement switching with lipid-binding DNA nanostructures. This paves the way for achieving dynamic control of membrane morphology, enabling broader applications in nanomedicine and biophysics.


Assuntos
DNA de Cadeia Simples/metabolismo , DNA/metabolismo , Lipossomos/metabolismo , Fosfatidilcolinas/metabolismo , Fosfatidiletanolaminas/metabolismo , Colesterol/química , Colesterol/metabolismo , DNA/química , DNA de Cadeia Simples/química , Concentração de Íons de Hidrogênio , Cinética , Lipossomos/química , Cloreto de Magnésio/química , Cloreto de Magnésio/metabolismo , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Conformação de Ácido Nucleico , Fosfatidilcolinas/química , Fosfatidiletanolaminas/química , Cloreto de Sódio/química , Cloreto de Sódio/metabolismo , Soluções , Termodinâmica
6.
Int J Mol Sci ; 22(18)2021 Sep 17.
Artigo em Inglês | MEDLINE | ID: mdl-34576237

RESUMO

Previous studies reported on the broad-spectrum antiviral function of heparin. Here we investigated the antiviral function of magnesium-modified heparin and found that modified heparin displayed a significantly enhanced antiviral function against human adenovirus (HAdV) in immortalized and primary cells. Nuclear magnetic resonance analyses revealed a conformational change of heparin when complexed with magnesium. To broadly explore this discovery, we tested the antiviral function of modified heparin against herpes simplex virus type 1 (HSV-1) and found that the replication of HSV-1 was even further decreased compared to aciclovir. Moreover, we investigated the antiviral effect against the new severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) and measured a 55-fold decreased viral load in the supernatant of infected cells associated with a 38-fold decrease in virus growth. The advantage of our modified heparin is an increased antiviral effect compared to regular heparin.


Assuntos
Antivirais/farmacologia , Heparina/farmacologia , Cloreto de Magnésio/farmacologia , Aciclovir/farmacologia , Adenovírus Humanos/efeitos dos fármacos , Adenovírus Humanos/fisiologia , Animais , Antivirais/química , Células CHO , Linhagem Celular Tumoral , Chlorocebus aethiops , Cricetulus , Avaliação Pré-Clínica de Medicamentos , Fibroblastos , Heparina/química , Herpesvirus Humano 1/efeitos dos fármacos , Herpesvirus Humano 1/fisiologia , Humanos , Cloreto de Magnésio/química , Espectroscopia de Ressonância Magnética , Testes de Sensibilidade Microbiana , Estrutura Molecular , Cultura Primária de Células , SARS-CoV-2/efeitos dos fármacos , SARS-CoV-2/fisiologia , Relação Estrutura-Atividade , Células Vero , Carga Viral/efeitos dos fármacos , Replicação Viral/efeitos dos fármacos
7.
Int J Biol Macromol ; 188: 670-677, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34400229

RESUMO

Key factors in the salting-in effects on proteins of additives are their interactions with aromatic groups. We studied the interaction of four aromatic solutes, benzyl alcohol (BA), phenol, 4-hydroxybenzyl alcohol (4-HBA) and methyl gallate (MG), with different salting-in additives, arginine hydrochloride (ArgHCl), magnesium chloride (MgCl2), ethylene glycol (EG), and guanidine hydrochloride (GdnHCl) using solubility measurements. We used sodium chloride (NaCl) as a control. MgCl2 decreased the solubility of the four aromatic solutes with weak solute dependence. In contrast, ArgHCl, GdnHCl, and EG increased the solubility of four aromatic solutes with a similar solute dependence. Their salting-in effects were weaker on BA and 4-HBA and stronger on phenol and MG. These results indicate that attached groups alter the aromatic properties, affecting the interactions between the benzene ring and these three additives. More importantly, the observed results demonstrate that the salting-in mechanism is different between MgCl2, EG and ArgHCl, which should play a role in their effects on protein solubility.


Assuntos
Arginina/química , Etilenoglicol/química , Cloreto de Magnésio/química , Proteínas/química , Sais/química , Solventes/química , Álcoois Benzílicos/química , Dicetopiperazinas/química , Ácido Gálico/análogos & derivados , Ácido Gálico/química , Guanidina/química , Solubilidade , Termodinâmica , Água/química
8.
Int J Mol Sci ; 22(12)2021 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-34205441

RESUMO

The article shows that the type and concentration of inorganic salt can be translated into the structure of the bulk phase and the performance properties of ecological all-purpose cleaners (APC). A base APC formulation was developed. Thereafter, two types of salt (sodium chloride and magnesium chloride) were added at various concentrations to obtain different structures in the bulk phase. The salt addition resulted in the formation of spherical micelles and-upon addition of more electrolyte-of aggregates having a lamellar structure. The formulations had constant viscosities (ab. 500 mPa·s), comparable to those of commercial products. Essential physical-chemical and performance properties of the four formulations varying in salt types and concentrations were evaluated. It was found that the addition of magnesium salt resulted in more favorable characteristics due to the surface activity of the formulations, which translated into adequately high wettability of the investigated hydrophobic surfaces, and their ability to emulsify fat. A decreasing relationship was observed in foaming properties: higher salt concentrations lead to worse foaming properties and foam stability of the solutions. For the magnesium chloride composition, the effect was significantly more pronounced, as compared to the sodium chloride-based formulations. As far as safety of use is concerned, the formulations in which magnesium salt was used caused a much lesser irritation compared with the other investigated formulations. The zein value was observed to decrease with increasing concentrations of the given type of salt in the composition.


Assuntos
Detergentes/toxicidade , Detergentes/química , Cloreto de Magnésio/química , Cloreto de Sódio/química , Tensão Superficial , Molhabilidade
9.
Nucleic Acids Res ; 49(8): 4574-4585, 2021 05 07.
Artigo em Inglês | MEDLINE | ID: mdl-33823552

RESUMO

We used stopped-flow to monitor hypochromicity for 43 oligonucleotide duplexes to study nucleic acid kinetics and extract transition-state parameters for association and dissociation. Reactions were performed in 1.0 M NaCl (for literature comparisons) and 2.2 mM MgCl2 (PCR conditions). Dissociation kinetics depended on sequence, increased exponentially with temperature, and transition-state parameters inversely correlated to thermodynamic parameters (r = -0.99). Association had no consistent enthalpic component, varied little with temperature or sequence, and poorly correlated to thermodynamic parameters (r = 0.28). Average association rates decreased 78% in MgCl2 compared to NaCl while dissociation was relatively insensitive to ionic conditions. A nearest-neighbour kinetic model for dissociation predicted rate constants within 3-fold of literature values (n = 11). However, a nearest-neighbour model for association appeared overparameterized and inadequate for predictions. Kinetic predictions were used to simulate published high-speed (<1 min) melting analysis and extreme (<2 min) PCR experiments. Melting simulations predicted apparent melting temperatures increase on average 2.4°C when temperature ramp rates increased from 0.1 to 32°C/s, compared to 2.8°C reported in the literature. PCR simulations revealed that denaturation kinetics are dependent on the thermocycling profile. Simulations overestimated annealing efficiencies at shorter annealing times and suggested that polymerase interactions contribute to primer-template complex stability at extension temperatures.


Assuntos
DNA/química , Ácidos Nucleicos/química , Análise por Conglomerados , Simulação por Computador , Cinética , Cloreto de Magnésio/química , Modelos Químicos , Conformação de Ácido Nucleico , Desnaturação de Ácido Nucleico , Oligonucleotídeos , Reação em Cadeia da Polimerase , Cloreto de Sódio/química , Temperatura , Termodinâmica
10.
Int J Mol Sci ; 22(5)2021 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-33652657

RESUMO

Formation of stable actin filaments, critically important for actin functions, is determined by the ionic strength of the solution. However, not much is known about the elements of the actin fold involved in ionic-strength-dependent filament stabilization. In this work, F-actin was destabilized by Cu2+ binding to Cys374, and the effects of solvent conditions on the dynamic properties of F-actin were correlated with the involvement of Segment 227-235 in filament stabilization. The results of our work show that the presence of Mg2+ at the high-affinity cation binding site of Cu-modified actin polymerized with MgCl2 strongly enhances the rate of filament subunit exchange and promotes the filament instability. In the presence of 0.1 M KCl, the filament subunit exchange was 2-3-fold lower than that in the MgCl2-polymerized F-actin. This effect correlates with the reduced accessibility of the D-loop and Segment 227-235 on opposite filament strands, consistent with an ionic-strength-dependent conformational change that modulates involvement of Segment 227-235 in stabilization of the intermonomer interface. KCl may restrict the mobility of the α-helix encompassing part of Segment 227-235 and/or be bound to Asp236 at the boundary of Segment 227-235. These results provide experimental evidence for the involvement of Segment 227-235 in salt-induced stabilization of contacts within the actin filament and suggest that they can be weakened by mutations characteristic of actin-associated myopathies.


Assuntos
Citoesqueleto de Actina/química , Actinas/química , Cobre/química , Cloreto de Magnésio/química , Doenças Musculares , Citoesqueleto de Actina/metabolismo , Actinas/metabolismo , Animais , Cobre/metabolismo , Cloreto de Magnésio/metabolismo , Coelhos
11.
Int J Biol Macromol ; 180: 299-310, 2021 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-33737183

RESUMO

Effects of Elm tree sawdust pretreatments using alkali and alkaline earth metals (NaCl, KCl, CaCl2, MgCl2 and Elm tree ash) and deashing solutions (water, HCl, HNO3 and aqua regia) before the carbonization process on the porosity of produced activated carbons and Pb (II) and Cr (VI) adsorption were studied. The activated carbons were characterized by pore size distribution, surface area, FTIR, and SEM-EDX analysies. Based on the results, HCl leaching pretreatment of the biomass increased the activated carbon adsorption capacity of Cr (VI) from 114 to 190 mg g-1. The treatment of biomass with alkali and alkali earth metal salts, especially MgCl2, remarkably increased the activated carbon adsorption capacity of Pb (II) from 233 to 1430 mg g-1. The results indicated that Pb (II) adsorption was attributed to both the mesoporous structure of activated carbon and the abundance of Mg on the activated carbon's surface. On the other hand, the micropores played a major role in Cr (VI) adsorption capacity. The development of the micro- or mesoporous structure of activated carbons through pretreatment of lignocellulosic precursor could be an approach for providing high performance activated carbons for Pb (II) and Cr (VI) removal from aqueous solutions.


Assuntos
Carvão Vegetal/química , Carvão Vegetal/síntese química , Cromo/química , Chumbo/química , Lignina/química , Poluentes Químicos da Água/química , Água/química , Adsorção , Biomassa , Ácido Clorídrico/química , Concentração de Íons de Hidrogênio , Cinética , Cloreto de Magnésio/química , Modelos Químicos , Porosidade , Soluções , Ulmus/química , Purificação da Água/métodos
12.
ACS Appl Mater Interfaces ; 13(3): 4583-4592, 2021 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-33448218

RESUMO

A salt-responsive nanoplatform is constructed through a simple tactic by tethering zwitterionic nanohydrogels (NGs) on a carboxylated silica (SiO2-COOH) framework. Chondroitin sulfate (CS), with a specific recognition effect for low-density lipoprotein (LDL), is modified to NGs by amidation reaction. Water retention and swelling properties of NGs are greatly enhanced in a saline environment attributed to the anti-polyelectrolyte effect. It endows the SiO2-NGs-CS framework a sensitive salt-responsive property, and thus, more CS moieties are exposed. The controlled adsorption of LDL with an adsorption efficiency of 7.2 to 93% is achieved by adjusting the concentration of MgCl2 from 0 to 0.1 mol L-1. SiO2-NGs-CS exhibits excellent adsorption capacity for fishing LDL, acquiring the highest adsorption capacity of 898.1 mg g-1. Moreover, SiO2-NGs-CS shows superior selectivity to the other three proteins with similar isoelectric points (pIs) to LDL. The captured LDL is readily stripped by 0.2% (m/m) SDS with a recovery of 95.4%. The superior separation performance of SiO2-NGs-CS is demonstrated by the isolation and selective discrimination of LDL from the simulated serum of hypercholesterolemia patients, as illustrated by sodium dodecyl sulfate polyacrylamide gel electrophoresis assays.


Assuntos
Sulfatos de Condroitina/química , Hidrogéis/química , Lipoproteínas LDL/isolamento & purificação , Nanogéis/química , Dióxido de Silício/química , Adsorção , Animais , Bovinos , Eletroforese em Gel de Poliacrilamida , Humanos , Lipoproteínas LDL/sangue , Cloreto de Magnésio/química
13.
Int J Biol Macromol ; 167: 1273-1280, 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-33189753

RESUMO

Caseinolytic protease-associated chaperones (Clp chaperones) are HSP100 proteins belonging to the family of ATPases having diverse cellular functions, and they occur in various organisms ranging from bacteria to plants and mammals. Most Clp chaperones have a hexameric organization and associate with tetradecameric Clp proteases to recognize and unfold protein substrates that get degraded within the cellular milieu. Vascular plants have a diverse family of Clp chaperones compared to other organisms; wherein, the chloroplasts of Arabidopsis thaliana alone contain four distinct Clp chaperones, such as ClpC1, ClpC2, ClpD, and ClpB3. The paralogs AtClpC1 and AtClpC2 are more than 90% identical, though the extent of functional overlap between the two is not clear. Moreover, in vitro characterization reports are available only for AtClpC2, as AtClpC1 could not be expressed in recombinant form in the past. Herein, using a bacterial expression system, we have successfully expressed and purified AtClpC1 with a short N-terminal truncation, employing a three-step chromatographic purification strategy. We show that AtClpC1 exists as a hexamer in the presence of ATP and MgCl2, as known for other functional Clp chaperones. Further, our SAXS analyses provide a low-resolution envelope structure for the hexameric AtClpC1, which very well fits a ClpC hexamer model.


Assuntos
Proteínas de Arabidopsis/química , Arabidopsis/química , Proteínas de Cloroplastos/química , Proteínas de Choque Térmico/química , Proteínas Recombinantes/química , Trifosfato de Adenosina/química , Sequência de Aminoácidos , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Proteínas de Cloroplastos/genética , Proteínas de Cloroplastos/metabolismo , Cromatografia em Gel , Dicroísmo Circular , Expressão Gênica , Proteínas de Choque Térmico/genética , Proteínas de Choque Térmico/metabolismo , Cloreto de Magnésio/química , Filogenia , Domínios Proteicos , Estrutura Secundária de Proteína , Proteínas Recombinantes/genética , Proteínas Recombinantes/isolamento & purificação , Proteínas Recombinantes/metabolismo , Espalhamento a Baixo Ângulo , Difração de Raios X
14.
Int J Mol Sci ; 21(24)2020 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-33334011

RESUMO

HU is a nucleoid-associated protein expressed in most eubacteria at a high amount of copies (tens of thousands). The protein is believed to bind across the genome to organize and compact the DNA. Most of the studies on HU have been carried out in a simple in vitro system, and to what extent these observations can be extrapolated to a living cell is unclear. In this study, we investigate the DNA binding properties of HU under conditions approximating physiological ones. We report that these properties are influenced by both macromolecular crowding and salt conditions. We use three different crowding agents (blotting grade blocker (BGB), bovine serum albumin (BSA), and polyethylene glycol 8000 (PEG8000)) as well as two different MgCl2 conditions to mimic the intracellular environment. Using tethered particle motion (TPM), we show that the transition between two binding regimes, compaction and extension of the HU protein, is strongly affected by crowding agents. Our observations suggest that magnesium ions enhance the compaction of HU-DNA and suppress filamentation, while BGB and BSA increase the local concentration of the HU protein by more than 4-fold. Moreover, BGB and BSA seem to suppress filament formation. On the other hand, PEG8000 is not a good crowding agent for concentrations above 9% (w/v), because it might interact with DNA, the protein, and/or surfaces. Together, these results reveal a complex interplay between the HU protein and the various crowding agents that should be taken into consideration when using crowding agents to mimic an in vivo system.


Assuntos
Proteínas de Bactérias/química , Proteínas de Ligação a DNA/química , Modelos Moleculares , Conformação Proteica , Algoritmos , DNA/química , DNA Bacteriano/química , DNA Bacteriano/metabolismo , Cloreto de Magnésio/química , Cloreto de Magnésio/farmacologia , Modelos Teóricos , Polietilenoglicóis/química , Ligação Proteica
15.
J Dairy Sci ; 103(11): 9923-9935, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32921475

RESUMO

In casein micelle (CM), Ca is either precipitated in the colloidal calcium phosphate (CCP) stabilized by clusters of phosphoserine (SEP) residues, or is directly bound to SEP (or glutamic and aspartic acids) of caseins without inorganic phosphate. However, it is currently not possible to titrate separately the different micellar Ca forms, making it difficult to assess their respective importance for CM properties and behavior. Both Ca2+ and Mg2+ have the same binding constants with SEP. Moreover, MgHPO4 is more soluble than CaHPO4, and its natural concentration in milk is lower. Thus, upon addition of MgCl2, Mg is mainly exchanged with CM in the bound form, whereas upon addition of CaCl2, Ca is mainly exchanged in the precipitated form. Our objective was to assess the role of the 2 forms of micellar cations (bound and precipitated) during the enzymatic coagulation of cow milk. Magnesium chloride, CaCl2, or KCl (10 mM) were added to milk and pH was adjusted to 6.6 after overnight equilibration. The KCl-supplemented milk was a positive control to assess the effect of the increased ionic strength after MgCl2 and CaCl2 addition. Mineral partition between soluble and colloidal phases after salt addition was assessed both experimentally and by using computer simulation. Enzymatic coagulation was proceeded at 30°C. Hydrolysis of κ-casein was followed by the quantitative determination of caseinomacropeptide released by RP-HPLC, aggregation of para-κ-casein micelles was measured through the evolution of backscattering properties of milk and the gel time and gel firming kinetics were determined using a Chymograph (Chr. Hansen, Horsholm, Denmark). The KCl addition did not affect mineral partition. As expected, CaCl2 addition mainly increased the CCP content, whereas the addition of MgCl2 mainly increased the bound divalent cations content. The kinetics of κ-casein hydrolysis was slowed down after CaCl2 and MgCl2 addition, and was negatively correlated with the concentration of divalent cations in the soluble phase of milk. Aggregation and gel firming curves plotted versus the progress of κ-casein hydrolysis were similar for both CaCl2- and MgCl2-supplemented milk. In view of the dual-binding model for CM assembly, this means that both Ca forms reduce electronegative repulsions between para-micelles by specific charge shielding. Inclusion of 2 Ca forms in structural models for CM allows a more detailed comprehension of how mineral equilibria affect CM properties.


Assuntos
Cloreto de Cálcio/química , Fosfatos de Cálcio/química , Caseínas/química , Cloreto de Magnésio/química , Leite/química , Fragmentos de Peptídeos/química , Animais , Cálcio da Dieta/análise , Simulação por Computador , Micelas , Minerais/química , Fosfatos/química
16.
Bioanalysis ; 12(12): 857-866, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32603603

RESUMO

Aim: Antidrug antibody (ADA) assessment may be challenged in studies that involve the administration of high doses of biotherapeutics and/or with long half-lives. In such cases, ADA assays with optimized drug tolerance are desired. Material & Methods: We evaluated the use of MgCl2 to develop high ionic strength dissociation assays in two investigational examples (bridging enzyme-linked immunosorbent ADA assays) to attain high drug tolerance while maintaining best possible structural integrity of ADAs. Results: Both ADA-bridging assays treated with MgCl2 showed improved drug tolerance and higher signal-to-blank values compared with overnight incubation or acid treatment. Conclusion: The use of MgCl2 treatment in ADA-bridging assays provides a sensitive, drug tolerant and easy-to-use alternative in cases where acid dissociation is not possible or unwanted.


Assuntos
Anticorpos Monoclonais/imunologia , Tolerância a Medicamentos/imunologia , Ensaio de Imunoadsorção Enzimática , Cloreto de Magnésio/química , Humanos , Concentração de Íons de Hidrogênio , Concentração Osmolar
17.
Chemosphere ; 256: 126968, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32428738

RESUMO

The recycling of nutrients from wastewater and their recovery in the form of valuable products is an effective strategy to accelerate the circular economy concept. Phosphorus recovery from wastewater by struvite crystallization (MgNH4PO4·6H2O) is one of the most applied techniques to compensate for the increasing demand and to slow down the depletion rate of phosphate rocks. Using low-cost magnesium sources, such as seawater, improves the financial sustainability of struvite production. In this study, the potential of seawater for struvite crystallization versus the commonly used magnesium source, MgCl2, was tested by crystal growth and kinetic experiments. The impact of ammonium concentration, magnesium concentration and pH on the growth kinetics of struvite in synthetic and real reject water were studied. The results showed that simultaneous precipitation of calcium phosphate was insignificant when using seawater, while presence of struvite seeds diminished it further. Among the supersaturation regulators, pH had the most significant effect on the struvite growth with both MgCl2 and seawater, while high N:P molar ratios further improved the struvite crystal growth by seawater. The N:P molar ratios higher than 6 and Mg:P molar ratios higher than 0.2 are recommended to improve the crystal growth kinetics. It was concluded that seawater is a promising alternative magnesium source and the control of supersaturation regulators (i.e., Mg:P, N:P and pH) is an effective strategy to control the reaction kinetics and product properties.


Assuntos
Modelos Químicos , Água do Mar/química , Estruvita/química , Fosfatos de Cálcio , Cristalização , Cinética , Magnésio/química , Cloreto de Magnésio/química , Compostos de Magnésio/química , Minerais , Fosfatos/química , Fósforo/química , Reciclagem , Águas Residuárias/química
18.
Chem Commun (Camb) ; 56(25): 3613-3616, 2020 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-32107514

RESUMO

Rapid aging tests (70 °C, 50% RH) of solid state DNA dried in the presence of various salt formulations, showed the strong stabilizing effect of calcium phosphate, calcium chloride and magnesium chloride, even at high DNA loadings (>20 wt%). A DNA-based digital information storage system utilizing the stabilizing effect of MgCl2 was tested by storing a DNA file, encoding 115 kB of digital data, and the successful readout of the file by sequencing after accelerated aging.


Assuntos
Cloreto de Cálcio/química , Fosfatos de Cálcio/química , DNA/química , Armazenamento e Recuperação da Informação , Cloreto de Magnésio/química , DNA/síntese química , Tamanho da Partícula , Sais/química , Propriedades de Superfície
19.
Molecules ; 25(2)2020 Jan 12.
Artigo em Inglês | MEDLINE | ID: mdl-31940875

RESUMO

The xylitol ester of hydrogenated rosin (XEHR) was obtained for the first time from biomass-based hydrogenated rosin and xylitol using an environmentally friendly, high-pressure CO2 catalytic synthesis. This compound is intended for use as an emulsifier for food. Analyses by ICP-AES showed the absence of heavy metal residues in the product, such that it met food standards. Fourier transform infrared and nuclear magnetic resonance spectroscopies together with gel permeation chromatography confirmed the successful esterification and the formation of a monoester and diester with molar masses of 427 and 772 g/mol. The emulsification of water/soybean oil mixtures by adding the XEHR was assessed at pH values of 4, 6.86, and 10 and in the presence of NaCl, KCl, MgCl2, and CaCl2. The XEHR was found to act as an emulsifier by reducing the interfacial tension of such mixtures to less than 2 mN/m under all conditions. The highest emulsifying activity index (9.52 m2/g) and emulsifying stability index (94.53%) were obtained after adding MgCl2 (100 mM). Particle size and confocal microscopy showed that the presence of salts gave a more uniform droplet size and a finer emulsion structure. The high viscosities of the emulsions containing salts also suggested a more cohesive oil droplet network.


Assuntos
Emulsificantes/síntese química , Ésteres/química , Aditivos Alimentares/síntese química , Resinas Vegetais/química , Xilitol/química , Biomassa , Dióxido de Carbono/química , Emulsificantes/análise , Ésteres/análise , Aditivos Alimentares/análise , Humanos , Concentração de Íons de Hidrogênio , Hidrogenação , Cloreto de Magnésio/química , Tamanho da Partícula , Pressão , Óleo de Soja/química , Tensão Superficial , Água/química , Xilitol/análise
20.
J Hazard Mater ; 383: 121099, 2020 02 05.
Artigo em Inglês | MEDLINE | ID: mdl-31518808

RESUMO

High CO2 emissions during the production process of ordinary Portland cement (OPC) promoted greener-cement development, wherein the application of magnesium oxychloride cement (MOC) can add value to waste in potash industry and reduce environmental hazards. However, its application was restricted by its inferior water resistance. It's a challenge to remarkably increase both the compressive strength and water resistance of MOC. Herein, we demonstrate that cornstarch/sodium polyacrylate (PAAS) MOC composites exhibit increased compressive strength and water resistance. Moreover, the biomineralization process encourages the growth and alignment of phase 5 crystals by a cornstarch template with hydroxyl groups, thus enhancing the compressive strength of MOC. The chelation of magnesium ions and the transformation of phase 5 crystal structure by PAAS can significantly enhance the water resistance of MOC. This composite exhibits a 21.0% increase in compressive strength, and the softening coefficient is also increased from 0.48 to 0.81 in comparison with unmodified-MOC. Meanwhile, the hydrogen bonds between cornstarch and elemental Cl obviously decrease the efflorescence phenomena of the MOC. This MOC composite with a markedly increased compressive strength and water resistance, which was prepared by a facile and green method, may have potential applications in building development and the replacement of OPC.


Assuntos
Força Compressiva , Materiais de Construção , Cloreto de Magnésio/química , Teste de Materiais , Água/química , Microscopia Eletrônica de Varredura
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