Influence Of Magnesium Ions Research Articles

Synthesis of eco-sustainable seawater sea-sand geopolymer mortars from ternary solid waste: Influence of microstructure evolution on mechanical performance

To fully utilize abundant marine resources and reduce the carbon footprint in the construction sector, this study developed a seawater sea-sand geopolymer mortar (SSGM) using seawater, sea-sand, and ternary solid waste. Three different alkaline content levels (4%, 5%, and 7%) were tailored for the SSGM, in addition to freshwater river sand mixed geopolymer mortars (FRGM), seawater sea-sand ordinary Portland cement mortar (SSCM), and SSGM without additional fibres (SSGM-0). The workability, setting time, mechanical performance, and drying shrinkage of all samples were studied. The microstructural characteristics of each mortar were meticulously scrutinized through techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and mercury intrusion porosimetry (MIP). The results showed that as alkaline content increased, SSGM formed more hybrid sodium, calcium aluminosilicate hydrate (N, C-A-S-H) gels, resulting in a denser matrix. Under the influence of magnesium ions and sulfate ions in seawater, the formation of magnesium aluminosilicate hydrates, magnesium silicate hydrates, and silica gels filled the pores, making SSGM has more mesopores and gel pores compared to FRGM, thus exhibiting superior mechanical properties. However, the Ca/Si ratio of the primary hydration products of SSGM was lower than that of SSCM and FRGM, indicating a more disordered microstructure of SSGM, leading to greater shrinkage. Despite moisture migration reaching a stable state, SSGM exhibited persistent shrinkage, revealing their inherent time-dependent (creep) response to drying conditions, indicative of typical viscoelastic/visco-plastic matrix behavior.

Microscopic mechanisms of MgCl2 affecting anionic surfactant adsorption kinetics on the air[sbnd]water interface

Inorganic salts can significantly affect the interfacial tension (IFT) of surfactant solutions, which is a key factor influencing the interphase mass transfer and reaction in multiphase systems. The change in IFT is directly related to the adsorption behavior of surfactants. However, the mechanisms underlying the effects of salt on surfactant IFT and adsorption kinetics are not yet clear. Here, taking MgCl2 and sodium dodecyl sulfate (SDS) as examples, the IFT characteristics of surfactant solutions under different salt concentrations were investigated, and the adsorption behavior and interface characteristics of SDS with or without MgCl2 were further analyzed by molecular dynamics simulations. We find that surfactant adsorption involves mixed diffusion-kinetic controlled adsorption. The addition of MgCl2 can obviously accelerate the adsorption kinetics and increase the adsorption capacity of SDS. Under the influence of magnesium ions, more “vacant sites” exist on the interface. Meanwhile, the orientation of the headgroups can be rapidly changed during the adsorption process to achieve a reasonable adsorption configuration faster, and the double electric layer (EDL) becomes thinner, reducing the electrostatic barrier. In addition, our findings offer new insights into anionic surfactant adsorption kinetics in a saline environment.

Influence of Magnesium Ions on the Preparation and Storage of DNA Tetrahedrons in Micromolar Ranges.

The DNA tetrahedron (Td), as one of the novel DNA-based nanoscale biomaterials, has been extensively studied because of its excellent biocompatibility and increased possibilities for decorating precisely. Although the use of Td in laboratories is well established, knowledge surrounding the factors influencing its preparation and storage is lacking. In this research, we investigated the role of the magnesium ions, which greatly affect the structure and stability of DNA. We assembled 1, 2, 5, 10 and 20 μM Td in buffers containing different Mg2+ concentrations, demonstrating that 2 and 5 mM Mg2+ is optimal in these conditions, and that yields decrease dramatically once the DNA concentration reaches 20 μM or the Mg2+ concentration is lower than 0.5 mM. We also verified that the Td structure is retained better through freeze-thawing than lyophilization. Furthermore, a lower initial Mg2+ (≤2 mM) benefited the maintenance of Td structure in the process of lyophilization. Hence, our research sheds light on the influence of Mg2+ in the process of preparing and storing Td, and also provides some enlightenment on improving yields of other DNA nanostructures.

Evaluation of the Transepidermal Penetration of a Carnosine Complex in Gel Formulation by 3D Skin Models

Carnosine has several physiological roles, from intracellular pH buffering to antioxidant activities, which all depend on bioavailability. This study was conducted in a human skin 3D model and focuses on the effects of the topical delivery of carnosine, from a dermo-cosmetic gel, through the stratum corneum in the presence of a magnesium ion as a complexing agent. To evaluate possible enhancement for small peptide delivery to the skin from simple cosmetic formulations, we discovered that complexation was able to improve the delivery of carnosine into human skin 3D models by application in gel formulation. The concentrations of carnosine released in the underlying media and those that remained in the reconstructed human epidermis (RHE) tissues after 24 and 48 h exposure were measured. Moreover, the influence of magnesium ions was also evaluated comparing the same formulation with and without the salt. The results obtained in this study support hypothesis that magnesium can influence the delivery of small peptides and that the gel formulation based on the carnosine-magnesium complex allows for superior delivery of carnosine in the lower skin layer at a concentration up to 60% more than carnosine alone.

Influence of Magnesium Ions in the Seawater Environment on the Improvement of the Corrosion Resistance of Low-Chromium-Alloy Steel.

This study examined the synergic effect of alloying the element Cr and the environmental element Mg2+ ions on the corrosion property of a low-alloy steel in seawater at 60 °C, by means of electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) tests and weight-loss tests. The Mg2+ ions in seawater played an important role in lowering the electron transfer of the rust layer in the Cr-containing steel. The corrosion resistance of the Cr-containing steel is superior to that of blank steel in Mg2+ ions containing seawater. XPS and XRD results indicated that the formation of MgFe2O4 and a mixed layer (Cr oxide + FeCr2O4 + MgCr2O4) improved the corrosion resistance of the low-alloy steel in the seawater.

Transducin-activated cGMP-specific phosphodiesterase of external segments of bovine retinal rods: The influence of magnesium ions

The kinetic behavior of phosphodiesterase activated by transducin in a complex with a non-hydrolyzable GTP analogue (guanosine-5′-O-thiotriphosphate) was studied by the pH-metric method in preparations of light-adapted external segments of bovine retinal rods in a range of magnesium ion concentrations from 0.4 to 20 mM. These results indicate that when using the reaction media containing 10–15 mM Mg2+ ions, introduction of 2–4 mM ethylene glycol tetraacetic acid (a chelator of calcium ions) in the reaction medium induces only relatively small changes in the concentration of free magnesium ions that are not able to significantly influence the phosphodiesterase activity.

Development of a new product: egg white albumen gels with differentiated magnesium release

Commercial egg white isolates (EWI) or concentrates contain substantial quantities of minerals and they easily form heat-induced gels. An innovative, low mineral EWI was used in the present research to investigate the influence of magnesium ions on the gelation process and on the release of these ions in simulated gastric conditions. Heat-induced gelation of egg white proteins was monitored by using an ultrasound viscometer and an oscillatory rheometer. Samples behaved as weak gels with the storage modulus about 5 times larger than the loss modulus. Both methods revealed two phases of gelation. More elastic behavior of gels with an increased magnesium ion concentration can be explained by a higher number of bonds between protein molecules observed in transmission electron microscopy images. An increased concentration of magnesium ions in gel caused an increased release rate of these ions in simulated gastric conditions, which was probably caused by a higher surface roughness of the gel. Higher roughness of the gel surface enlarges the contact area and enables faster hydrolysis. The egg white isolate gels with a high bioavailability organic form of magnesium could be used as food supplement with a regulated magnesium release rate in the human stomach.

Influence of magnesium ions and amino acids on the nucleation and growth of hydroxyapatite

It has long been known that magnesium (Mg) ions are effective inhibitors of hydroxyapatite (HAP) crystal nucleation and growth. During the HAP nucleation, it is now generally recognized that the involvement of assembled amorphous calcium phosphate (ACP) nuclei and prenuclei may be of greater importance in the overall crystallization mechanism. In the calcium-phosphate (Ca–P) biomineralization process significant amounts of Mg ions are present in animal skeletons where they are thought to stabilize ACP mineral phases. However, there is still some uncertainty concerning the precise roles of Mg in the nucleation and growth of apatite minerals. Herein, a slow, well-controlled, Ca–P crystallization study under a precisely defined thermodynamic driving force shows that Mg ions are able to prevent the nucleation of HAP in supersaturated Ca–P solutions by stabilizing gel-like ACP phases, prolonging the induction and subsequent transformation times, under near-physiological conditions (pH 7.400, ionic strength (I) = 0.150 mol L−1, 37.0 °C). Relatively large HAP crystals growing from the ACP surfaces were characterized by HRTEM and SEM. Surprisingly, EDS spectra revealed that no Mg ions were present in either the gel-like ACP or final crystalline phase. Following the addition of amino acids to the supersaturated solutions both in the presence and absence of Mg ions, the nucleation of HAP was promoted by shortening the induction and transformation times, and at the same time, the sizes of ACP and HAP crystals decreased as compared with the controls. Our results suggest that the formation of magnesium-phosphate (Mg–P) ion pairs may reduce the thermodynamic driving force for nucleation and phase transformation to HAP.

Influence of Magnesium Ions on Spontaneous Opening of DNA Base Pairs

Influence of Magnesium Ions on Spontaneous Opening of DNA Base Pairs

Magnesium-Mediated Nanocrystalline Mosaics of Calcite

Magnesium ions are widely found in calcium-based biominerals as an accessory component. In this report, the influence of magnesium ions on the crystal growth of CaCO3 was investigated on the basis of the nanostructure. The morphology of calcite grown in a supersaturated solution was drastically changed from a regular rhombohedron into a spherical architecture consisting of nanocrystalline mosaics in the presence of a large number of magnesium ions. While magnesium ions were substituted for ca. 6% of calcium ions in the crystal lattice at a maximum, an excess amount of magnesium produced an amorphous phase leading to the nanostructure with modulation of the crystal growth of calcite.

Influence of magnesium ions on spontaneous opening of DNA base pairs.

A large amount of experimental evidence is available for the effects of magnesium ions on the structure and the stability of the DNA double helix. Less is known, however, on how these ions affect the dynamics of the molecule and the stability of each individual base pair. The present work addresses these questions by a study of the DNA duplex [dCGCAGATCTGCG]2, and its interactions with magnesium ions using nuclear magnetic resonance (NMR) spectroscopy and proton exchange. Two-dimensional NMR experiments indicate that binding of magnesium to this DNA duplex does not affect its structure. However, even in the absence of structural changes, magnesium ions specifically affect the exchange properties of imino protons in the four GC/CG base pairs that are located in the interior of the double helix. These specific changes do not result from alterations in the rates of spontaneous opening of these base pairs. Instead, the changes most likely reflect an enhancement in the energetic propensity for spontaneous opening of the GC/CG base pairs that is induced by the binding of magnesium ions.

Nickel‐catalyzed electrochemical carboxylation of epoxides: mechanistic aspects

The electrochemical incorporation of carbon dioxide into epoxides catalyzed by nickel(II) complexes afforded cyclic carbonates in good yields under very mild conditions (p atm, room temperature). Mechanistic and electrochemical studies revealed the cooperative role of reduced nickel species in the activation of CO2 and the influence of magnesium ions as Lewis acids in the activation of the oxirane ring. Both the presence of nickel catalysts and Mg2+ ions were necessary for the electrocarboxylation of epoxides under mild conditions. Copyright © 2001 John Wiley & Sons, Ltd.

Nickel-catalyzed electrochemical carboxylation of epoxides: mechanistic aspects

The electrochemical incorporation of carbon dioxide into epoxides catalyzed by nickel(II) complexes afforded cyclic carbonates in good yields under very mild conditions (p atm, room temperature). Mechanistic and electrochemical studies revealed the cooperative role of reduced nickel species in the activation of CO2 and the influence of magnesium ions as Lewis acids in the activation of the oxirane ring. Both the presence of nickel catalysts and Mg2+ ions were necessary for the electrocarboxylation of epoxides under mild conditions. Copyright © 2001 John Wiley & Sons, Ltd.

Magnesium as a Stress-Protectant for Industrial Strains of Saccharomyces Cerevisiae

During brewery fermentations, individual yeast cells may be con-fronted with a variety of environmental stresses that impair yeast growth and fermentative metabolism. An understanding of the stress physiology of industrial yeasts is therefore important in order to counteract deleterious effects of stress on fermentation and, ultimately, product quality. The present study describes the influence of magnesium ions in preventing cell death caused by temperature shock and ethanol toxicity in Saccharomyces cerevisiae yeast strains employed in brewing, distilling, and wine fermentations. Results obtained show that, by increasing the extracellular availability of magnesium ions, physiological protection may be conferred on temperature- and ethanol-stressed yeast cells with respect to culture viability and growth. This practical approach is envisaged to offer benefits to alcoholic fermentation processes in terms of enhancing the viability of the yeasts employed. It is proposed that magnesium prevents stress-induced damage to yeast cells by protecting the structural and functional integrity of the plasma membrane.

Influence of Magnesium Ions on Duplex DNA Structural, Dynamic, and Solvation Properties

Molecular dynamics (MD) simulations were performed on the DNA dodecamer comprising the EcoRI recognition site in aqueous solution. Three simulations, each of 1 ns duration, were performed that included no salt, 0.26 M Mg+2, and 0.50 M Mg2+ and 0.59 M Cl-. The simulations yielded stable structures that were intermediate to the canonical A and B conformations of DNA. Certain aspects of the MD solution structures are similar to the EcoRI dodecamer crystal structure. Interactions of the phosphates with Mg2+ occur primarily with Mg+2 fully hydrated, although direct ion−phosphate contact pairs are observed. The presence of Mg2+ leads to decreased root mean square fluctuations of the DNA phosphate backbone and the waters hydrating the DNA major groove and phosphate backbone. Calculations also indicate a small increase in hydration of the minor groove and phosphate backbone due to the presence of Mg2+. These results suggest that decreased water mobility rather than decreased hydration number is responsible for Mg2+-induced dehydration of DNA associated with decreased water activity.

IR lattice vibrational study on Mg-containing zeolite A

The influence of magnesium ions on the lattice vibration spectra of zeolite A is studied. The observed changes in position, shape and intensity of vibration bands as well as in the course of the background are discussed in terms of framework distortion and of changes in the covalency of the zeolite lattice.

The influence of magnesium ions during the formation of stromatolitic phosphorites of Udaipur, Rajasthan, India

Abstract The stromatolites of the Precambrian Aravalli Supergroup outcropping around Udaipur City are composed of carbonate (dominantly dolomite) and/or phosphate (carbonate-fluorapatite). The phosphate present in these stromatolites occurs in varying proportions, from traces levels to a major constituent. Compositional variation is attributed to the differences in the original magnesium contents stromatolites which reflects their different of the depositional environments, Intertidal stromatolites had primary magnesium calcite mineralogies, while those deposited in subtidal areas were composed of aragonite and/or lower magnesium calcite. The Mg/Ca ratio in the stromatolites appears to have been controlled by microorganisms which, it is argued, also played an important role in the process of phosphate fixation. It is inferred that the high Mg content of intertidal stromatolites prevented extensive phosphatisation in this facies.

The Influence of Magnesium Ions on the NMDA Mediated Responses of Ventral Rhythmic Neurons in the Spinal Cord of Xenopus Embryos.

Xenopus embryos immobilized in tubocurarine respond to natural skin stimulation with fictive swimming. This can also occur in saline without Mg2+ and is blocked by NMDA antagonists. Ventral spinal cord neurons which are rhythmically active during swimming are depolarized by bath applied N-methyl-D-aspartate (NMDA) (in 1 microM tetrodotoxin (TTX) to block indirect effects). By using current clamp techniques this depolarization is shown to be partially blocked by 0.5 and 1 mM Mg2+ in a voltage-dependent manner similar to that described in cultured neurons. Mg2+ partially and reversibly reduces the slow NMDA-mediated component of excitatory post-synaptic potentials (EPSPs) in ventral neurons. However, in 1 mM Mg2+ fictive swimming can still be evoked by natural stimulation. The frequency of swimming is slightly lower than in nominally 0 mM Mg2+, but the pattern of ventral root activity and synaptic drive to ventral neurons seems little affected. Fictive swimming can also be induced by applying NMDA to spinal preparations. In 0 mM Mg2+, such rhythmic activity is unstable and transient over a narrow NMDA concentration range. In 0.5 mM Mg2+, continuous rhythmic activity is induced over a wide range of NMDA concentrations. Lower spinal preparations need higher NMDA concentrations to induce activity. We conclude that the neurons rhythmically active in swimming have NMDA receptor channels which show a voltage dependent block in the presence of Mg2+. However, while Mg2+ exerts a powerful stabilizing influence on rhythmic activity induced in spinal embryos by exogenous NMDA, its influence on 'naturally' evoked fictive swimming is less clear. The fictive swimming machinery in the brain and spinal cord can produce stable swimming with or without Mg2+ induced voltage dependency of the NMDA channels.

Influence of magnesium ions on cotton plant pyrophosphatase

Influence of magnesium ions on cotton plant pyrophosphatase

The influence of magnesium ion on the kinetics of crystal growth and dissolution of strontium fluoride

The influence of magnesium ion on the growth and dissolution of strontium fluoride crystals has been studied over an ionic strength range, 0.071–0.150 mol dm −3, in aqueous solutions at constant super- and under-saturation using a constant composition method. The rates of reaction, expressed in terms of the relative super- and under-saturations show an effective order, n, of 3.7±0.1 at relative super-saturations 0.95 to 1.86 and 1.1±0.1 at relative under-saturations of 0.06 to 0.2. However, under conditions close to equilibrium, both growth and dissolution approach a parabolic rate law probably reflecting surface controlled reactions. The addition of magnesium ions, even at relatively low concentration (10 −6 mol dm −3), reduced the rates of both growth and dissolution. Moreover, the effect was enhanced in the regions of parabolic kinetics. The influence of magnesium ions on the strontium fluoride reactions may be interpreted in terms of a Langmuir-type adsorption isotherm.