Apical acidity decreases inhibitory effect of omeprazole on Mg2+ absorption and claudin-7 and -12 expression in Caco-2 monolayers

Clinical studies reported hypomagnesaemia in long-term omeprazole usage that was probably due to intestinal Mg²⁺ wasting. Our previous report demonstrated the inhibitory effect of omeprazole on passive Mg²⁺ transport across Caco-2 monolayers. The present study aimed to identify the underlying mechanism of omeprazole suppression of passive Mg²⁺ absorption. By using Caco-2 monolayers, we demonstrated a potent inhibitory effect of omeprazole on passive Mg²⁺, but not Ca²⁺, transport across Caco-2 monolayers. Omeprazole shifted the %maximum passive Mg²⁺ transport-Mg²⁺ concentration curves to the right, and increased the half maximal effective concentration of those dose-response curves, indicating a lower Mg²⁺ affinity of the paracellular channel. By continually monitoring the apical pH, we showed that omeprazole suppressed apical acid accumulation. Neomycin and spermine had no effect on passive Mg²⁺ transport of either control or omeprazole treated monolayers, indicating that omeprazole suppressed passive Mg²⁺ transport in a calcium sensing receptor (CaSR)-independent manner. The results of western blot analysis showed that omeprazole significantly suppressed claudin (Cldn)-7 and -12, but not Cldn-2, expression in Caco-2 cells. By using apical solution of pH 5.5, 6.0, 6.5, and 7.0, we found that apical acidity markedly increased passive Mg²⁺ transport, Mg²⁺ affinity of the paracellular channel, and Cldn-7 and -12 expression in Caco-2 monolayers. Apical acidity abolished the inhibitory effect of omeprazole on passive Mg²⁺ transport and Cldn-7 and -12 expression. Our results provided the evidence for the regulation of intestinal passive Mg²⁺ absorption by luminal acidity-induced increase in Cldn-7 and -12 expression.     

Strukturchemische und impedanzspektroskopische Untersuchungen an Mg2+-stabilisierten Na+/Pr3+-β″-Al2O3-Kristallen

Structural Chemistry and Impedance Spectroscopy of Mg²⁺ stabilized Na⁺/Pr³⁺-β″-Aluminas The structure with the ionic distribution in the conduction planes of a Pr³⁺-exchanged Mg²⁺ stabilized Na⁺-β″-alumina crystal, composition determined by electron microprobe analysis to Na_1.19Pr_0.13Mg_0.49Al_10.49O₁₇ (degree of exchange ξ = 25%, related to Na⁺ content), has been investigated by single crystal X-ray diffraction methods at room temperature (R3 m, Z = 3, a = 561.8(2) pm, c = 3 361.5(11) pm). Pr³⁺ is slightly shifted in the ab-plane from the centrosymmetric 9 d (mO) into a 18 h site. Na⁺ occupies 18 h as well as 6 c (BR) positions. Ionic conductivity data of Mg²⁺ stabilized Na⁺/Pr³⁺-β″-Al₂O₃ crystals with varying degree of exchange determined by impedance spectroscopy are given in an Arrhenius diagram. With growing Pr³⁺ content the conductivity σ decreases with increasing activation energy.     

Chemical composition and crystal structure of β-alumina type R+-gallate (R+ = K+, NH+4)

The crystal structures of β-alumina type K⁺-gallate (K⁺-β-gallate), Mg²⁺-doped K⁺-β-gallate, and NH⁺₄-β-gallate were refined by the single crystal X-ray diffraction method. The positive charges of excess K⁺ ions in K⁺-β-gallate were compensated by O^2? ions in the mO site which coordinated with interstitial Ga³⁺ ions. The charge compensation mechanism mentioned above was changed by doping with Mg²⁺ ions. The excess charges in Mg²⁺-doped K⁺-β-gallate were compensated by the replacement of Mg²⁺ ions for Ga³⁺ ions at the middle of spinel block. No defects were found in NH⁺₄-β-gallate for the charge compensation, which was completely consistent with the result of thermal analysis that indicated a stoichiometric composition of NH⁺₄-β-gallate.     

Ca2+- and Mg2+-doped covalent organic frameworks exhibiting high hydrogen and acetylene storage

A multiscale theoretical investigation has been performed to study the hydrogen and acetylene storage in Ca²⁺- and Mg²⁺-doped COFs (COF-105 and COF-108). The first-principles calculations show that the Ca²⁺ and Mg²⁺ can be immobilized at the COFs surfaces, and the doped Ca and Mg cations can adsorb five H₂ molecules and three C₂H₂ molecules with ideal binding energies. The Grand Canonical Monte Carlo (GCMC) simulations were carried out to obtain the hydrogen and acetylene uptakes of Ca²⁺- and Mg²⁺-doped COFs at room temperature in the different pressure ranges. Our results demonstrate that, at T = 298 K and p = 100 bar, the total gravimetric uptakes of H₂ in Ca²⁺-doped COF-105 and COF-108 reach 6.78 and 6.54 wt%, respectively, and a higher uptakes of 7.14 and 7.27 wt% have been reached for Mg²⁺-doped COF-105 and COF-108, respectively. At T = 298 K and p = 1 bar, the acetylene uptakes of Ca²⁺-doped COF-105, Ca²⁺-doped COF-108, Mg²⁺-doped COF-105, and Mg²⁺-doped COF-108 are 406.42, 366.24, 308.07, and 319.88 cm³/g (corresponding to the excess uptakes of 358.37, 316.38, 236.7109, and 245.42 cm³/g), respectively. The Ca²⁺-doped COF-105 displays a highest acetylene storage capacity among all materials reported. The Ca²⁺- and Mg²⁺-doped COFs can be very practical hydrogen or acetylene storage medium in the future.     

Ionophore vom Typ der 3-Oxapentandiamide

Ionophores of the Type of 3-Oxapentane Diamides A series of lipophilic 3-oxapentane diamides were prepared and their selectivity in membranes was studied. N, N, N′, N′-Tetracyclohexyl-3-oxapentane diamide forms 1:2- and 1:3-metal/ligand-complexes with Mg²⁺ and Ca²⁺ respectively and induces a selectivity in membranes for Ca²⁺ over Mg²⁺ by a factor of about 10⁴.     

金属离子(Na~+、K~+、Ca~(2+)、Mg~(2+)、Zn~(2+))与鸟嘌呤异构体配合物的稳定性

在B3LYP/6-311++G**水平上用极化连续介质模型(PCM)系统研究了金属离子(M+/2+=Na+,K+,Ca2+,Mg2+,Zn2+)和十三种鸟嘌呤异构体形成的配合物GnxM+/2+(n为鸟嘌呤异构体的编号,x表示M+/2+与鸟嘌呤异构体的结合位点)在气(g)液(a)两相中的稳定性顺序.着重探讨了液相中配合物的稳定性差异,并且从溶质-溶剂效应、结合能、形变能及异构体的相对能量等几个方面分析了造成稳定顺序发生变化的原因.报道了溶液中这五种金属离子与鸟嘌呤异构体结合形成的六种基态配合物:aG1N2,N3Na+,aG1N2,N3K+,aG1O6,N7Ca2+,aG1N2,N3Mg2+(aG1O6,N7Mg2+),aG2N3,N9Zn2+.可以看出,除了在Zn2+配合物中鸟嘌呤异构体为G2外,构成其余四种金属离子配合物的鸟嘌呤异构体都是G1,但结合位点不同.同时对气相中各类配合物稳定性也进行了系统的排序,并报道了几种较稳定的配合物,如:gG3N1,O6K+,gG5N1,O6K+,gG3N1,O6Ca2+/Mg2+,gG4O6,N7Ca2+/Mg2+.     

Effect of Mg2+ Ions on the Stability of PolyA/2PolyU Three-Stranded Helices in Aqueous Solutions

The influence of Mg²⁺, Na⁺ and temperature on the conformational state of three-stranded helical polyA/2polyU (A2U) has been studied by the thermal denaturation method. At Na⁺ concentrations of 0.01–0.1 M , on heating the transition A2U→AU+U (the 3→2 transition) and then AU→A+U transition (the 2→1 transition) are observed. (AU is double helix polyA/polyU; A and U are single-stranded polyA and polyU, respectively.) With 0.01 M and 0.03 M Na⁺ these transitions occur at Mg²⁺ concentrations within (0 ÷ 0.003) M . At these ionic concentrations, there is a narrow temperature region (3 ÷ 5°C) at which double-helical AU formed by the 3→2 transition is resistant to heating. In 0.1 M Na⁺, a rise in the Mg²⁺ concentration leads to a continuous decrease in the temperature range of this region, and above a critical concentration of Mg²⁺ (ca. 3.6×10^–5 M )_cr there is only one transition (the 3→1 transition) instead of the successive transitions 3→2→1. The constants of Mg²⁺ ion association with polyU, polyA and A2U were calculated using equilibrium binding theory. The data obtained helped explain the reasons for the different phase diagrams for A2U + Mg²⁺ complexes in solution at high and low Na⁺ concentrations.     

Tuning the Stability of CaCO3 Crystals with Magnesium Ions for the Formation of Aragonite Thin Films on Organic Polymer Templates

Thin‐film growth of aragonite CaCO₃ on annealed poly(vinyl alcohol) (PVA) matrices is induced by adding Mg²⁺ into a supersaturated solution of CaCO₃. Both the growth rate and surface morphology of the aragonite thin films depend upon the concentration of Mg²⁺ in the mineralization solution. In the absence of PVA matrices, no thin films are formed, despite the presence of Mg²⁺. Molecular dynamics simulation of the CaCO₃ precursor suggests that the transition of amorphous calcium carbonate to crystals is suppressed in the presence of Mg²⁺. The role for ionic additives in the crystallization of CaCO₃ on organic templates obtained in this study may provide useful information for the development of functional hybrid materials.     

New strained ferrocenophane-based receptors for the selective electrochemical recognition of Mg in the presence of Ca cations

Ferrocenophane derivatives 3 act as electrochemical sensors of Mg²⁺ ions: a new redox peak appears in the CVs anodically shifted compared to the E_1/2 of the free receptors by 268-382 mV. Receptors 3a, 3c and 3d are selective for Mg²⁺, whilst 3b is also responsive to Ca²⁺ ion (302 mV shift). Receptor 3c also gave a highly visual output response in the presence of Mg²⁺ consisting of a deep purple colour.     

Studies on Synthetic Inorganic Ion Exchangers-III Quantitative Separations of Mg2+ -Pb2+, Zn2+ - Pb2+ Cu2+ - Pb2+, Al3+ - Pb2+, Zn2+ - Cd2+, and Mg2+ - Cd2+ on Lead Antimonate Columns

Abstract

A new inorganic ion exchanger, lead antimonate has been synthesized having an Pb:Sb ratio of 1:5 and cation exchange capacity of 1.46 mequiv./g. It is fairly stable in water and dilute solutions of acids, bases and salts. Ion distribution studies on twenty metal ions have been determined on this gel at pH 1,2,3 and 5. The following mixtures have been separated: Mg²⁺ - Pb²⁺, Zn²⁺ - Pb²⁺, Zn²⁺ - Pb²⁺, Cu²⁺ - Pb²⁺, Al³⁺ - Pb²⁺, Zn²⁺ - Cd²⁺ and Mg²⁺ - Cd²⁺. Mg²⁺ and Al³⁺ were removed with 0.4 M ammonium nitrate, Cu²⁺ and Zn²⁺ with 0.4 M ammonium nitrate + 0.1M nitric acid (1:1), Pb²⁺ with 0.5M nitric acid and Cd²⁺ with 0.25M nitric acid. A tentative structure of this material is proposed on the basis of chemical analysis, pH titrations, thermogravimetry and IR spectrophotometry.     

Mg<Superscript>2+</Superscript>/Ca<Superscript>2+</Superscript> binding to DNA bases: a quantum chemical method and ABEEMσπ/MM fluctuating charge model study

The interactions of Mg²⁺ and Ca²⁺ binding to adenine, cytosine, guanine, and thymine at various binding sites were studied by a high-level quantum chemical method and ABEEMσπ/MM fluctuating charge model. The geometries and binding energies of M²⁺-bases complexes were determined at CCSD(T)/6-311 ++G(2d,2p)//MP2/6-311 ++G(2d,2p) level of theory, with the basis set superposition error corrections for the binding energy calculations. In comparison with the ab initio results, an accurate classical metal cation–base interaction potential was constructed and parameterized in terms of ABEEMσπ/MM model. It is revealed that Mg²⁺/Ca²⁺ prefers to bind with bases at the bidentate position (between two nitrogen atoms or oxygen and nitrogen atoms in purine and pyrimidine), where the binding energy is the largest. Moreover, the distance between M²⁺ and the base increases from Mg²⁺ to Ca²⁺, while the binding energy of Mg²⁺–base is greater than that of Ca²⁺-base. The ABEEMσπ/MM potential gives reasonable geometries and binding energies compared with the present quantum chemical calculations, and the overall percentage RMSDs are 1.4 and 1.6% for geometries and binding energies, respectively. Furthermore, the transferability of the parameters of the new potential is validated by investigation of Mg²⁺/Ca²⁺ binding to tautomer of bases, and results from our potential also show quite good consistency with those of MP2/6-311 ++G(2d,2p)//B3LYP/6-311 ++G(d,p) method, with the overall percentage RMSDs of 2.2 and 4.7% for geometries and binding energies, respectively. This work will serve as a basis for further investigations of the mechanisms of cation effects on the structure and property of nucleic acids.     

A new Schiff base fluorescent indicator for the detection of Mg<Superscript>2+</Superscript> and its application to real samples

A new Schiff base fluorescence probe, 3-Allylsalicylaldehyde salicylhydrazone (L), for Mg²⁺ was designed and synthesized. The fluorescence of the sensor L was enhanced remarkably by Mg²⁺ with 2:1 binding ratio, and the binding constant was determined to be 1.02 × 10⁷ M^?1. Probe L had high sensitivity for Mg²⁺ in a solution of DMF/water (4:1, v/v, pH 7.5), and the detection limit was 4.88 × 10^?8 mol/L. Common coexistent metal ions, such as K⁺, Na⁺, Ag⁺, Ca²⁺, Zn²⁺, Ba²⁺, Bi²⁺, Cu²⁺, Ni²⁺, Hg²⁺, Fe³⁺ , and Al³⁺, showed little or no interference on the detection of Mg²⁺ in solution. The fluorescence probe L, which was successfully used for the determination of trace Mg(II) in real samples, was shown to be promising for liquid-phase extraction coupled with fluorescence spectra.     

Dynamics of magnesium-bicarbonate interactions

The complexation kinetics of Mg²⁺ with CO ₃ ⁼ and HCO ₃ ^? has been studied in methanol and water by means of the stopped-flow and temperature-jump methods. Kinetic parameters were obtained in methanol by coupling the magnesium-carbonato reactions with the metal-ion indicator Murexide. Relatively high stability constants were found in methanol (K=1.0×10⁵ liters-mole^?1 for Mg²⁺-Murexide,K=7.0×10⁴ liters-mole^?1 for Mg²⁺?HCO ₃ ^? , andK=2.0×10⁵ for Mg²⁺?CO ₃ ⁼ liters-mole^?1). The corresponding, observed formation rate constants were determined to be $$\begin{gathered} k_f = 4.0 \times 10^6 M^{ - 1} - sec^{ - 1} (Mg^{2 + } - Murexide) \hfill \\ k_f = 5.0 \times 10^5 M^{ - 1} - sec^{ - 1} (Mg^{2 + } - HCO_3^ - ) \hfill \\ k_f = 6.8 \times 10^5 M^{ - 1} - sec^{ - 1} (Mg^{2 + } - CO_3^ = ) \hfill \\ \end{gathered} $$ The relaxation times were found to be much shorter (τ≈5–20 μsec) in aqueous solutions, primarily due to the relatively high dissociation rate constants. The data could be interpreted on the basis of a coupled reaction scheme in which the protolytic equilibria are established relatively rapidly, followed by a single relaxation process due to the formation of MgHCO ₃ ⁺ and MgCO₃ between pH 8.7 and 9.3. The observed formation rate constants were determined to be $$\begin{gathered} k_f = 5.0 \times 10^5 M^{ - 1} - sec^{ - 1} (Mg^{2 + } - HCO_3^ - ) \hfill \\ k_f = 1.5 \times 10^6 M^{ - 1} - sec^{ - 1} (Mg^{2 + } - CO_3^ = ) \hfill \\ \end{gathered} $$ These results, in conjunction with NMR solvent exchange rate constants, are analyzed in terms of a dissociative (S _N1) mechanism for the rate of complex formation. The significance of these kinetic parameters in understanding the excess sound absorption in seawater is discussed.     

Crown-ether styryl dyes

The surface enhanced Raman scattering (SERS) spectra of styryl dyes containing a crown-ether group and a heteroaromatic residue with sulfoalkyl (1a) or alkyl (1b)N-substituent and of their complexes with Mg²⁺ cations were recorded in the 10^–4–10^–8 mol L^–1 concentration range. A model for the interaction of compoundsla,b with a silver surface during their adsorption on an electrochemically treated electrode was suggested. Fastcis-trans relaxation of the adsorbed molecules1a,b and complexes (1a,b)Mg²⁺ was found. It was shown that at [1a] = 10^–5 mol L^–1 and moderate molar ratios (C _Mg/[1a] = 3/1 to 9/1) in acetonitrile solutions, (trans-1a)Mg²⁺ complexes are joined into head-to-tail type dimers. An excess of Mg²⁺ cations (C_Mg/[1a] > 100) leads to dissociation of the dimers yielding (trans-1a)(Mg²⁺)₂ complexes. The formation of dimers from complexes (trans-1a)Mg²⁺ is accompanied by a substantial distortion of the planar structure oftrans-1a. This may be an important factor influencing the efficiency of photocycloaddition involving dimers of (trans-1a)Mg²⁺.For part 15, see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2429–2436, December, 1995.The work was carried out with financial support of the Russian Foundation for Basic Research (Project No. 94-03-08760) and, to some extent, of INTAS (Grant No. 93-1829) and of the International Science Foundation (Grant No. MHAOOO).     

Response of poly(vinyl chloride) electrodes based on the neutral carrier 1,4,7,10-tetraoxacyclododecane

Ion-selective electrodes based on the neutral carrier, 12-crown-4, in a poly(vinyl chloride) matrix were found to respond ideally, or almost ideally, to potassium, sodium, barium, strontium, magnesium, cobalt(II), nickel(II) and aluminum ions. The electrode showed good selectivity for Al³⁺ over Co²⁺ and Mg²⁺, and for Co²⁺ over Mg²⁺. Little selectivity was found for the other ions tested.     

DFT/MRCI assessment of the excited-state interplay in a coumarin-schiff Mg2+ fluorescent sensor

Fluorescent sensors with selectivity and sensitivity to metal ions are an active field in supramolecular chemistry for biochemical, analytical, and environmental problems. Mg²⁺ is one of the most abundant divalent ions in the cell, and it plays a critical role in many biological processes. Coumarin-based sensors are widely used as desirable fluorophore and binding moieties showing a remarkable sensitivity and fluorometric enhancement for Mg²⁺. In this work, density functional theory/multireference configuration interaction (DFT/MRCI) calculations were performed in order to understand the sensing behavior of the organic fluorescent sensor 7-hydroxy-4-methyl-8-((2-(pyridin-2-yl)hydrazono)methyl)-2H-chromen-2-one (PyHC) in ethanol to solvated Mg²⁺ ions. The computed optical properties reproduce well-reported experimental data. Our results suggest that after photoexcitation of the free PyHC, a photo-induced electron transfer (PET) mechanism may compete with the fluorescence decay to the ground state. In contrast, this PET channel is no longer available in the complex with Mg²⁺ making the emissive decay more efficient. © 2019 Wiley Periodicals, Inc.     

MgFe-Cl-LDHs的合成、结构及其插层组装性能研究

合成出了层间含Cl-的MgFe型层状双羟基氢氧化物（MgFe-Cl-LDHs），通过X射线衍射(XRD)、红外光谱(FT-IR)、热重及差热分析(TG-DTA)和元素分析等手段对其组成和结构特征进行了分析。研究表明：在共沉淀条件下，可制得晶体结构规整的MgFe-Cl-LDHs，且其结构规整性随组成中Mg²⁺/Fe³⁺物质的量比的增大而增强；LDHs层板六配位的金属离子与层板羟基层、层板羟基层与层间结构水的相互作用不随Mg²⁺/Fe³⁺物质的量比的改变而改变，而层板主体与层间客体阴离子之间的静电引力随Mg²⁺/Fe³⁺物质的量比的增大而降低。另外，其超分子结构特征使层间Cl^-能与有机阴离子CH₂CHC₆H₄SO₃^-和CH₃(CH₂)₁₁SO₃^-发生离子交换，形成以双分子层垂直于层板的交错有序的排布结构模式。     

High-entropy Electrolyte Enables High Reversibility and Long Lifespan for Magnesium Metal Anodes

The stable cycling of Mg-metal anodes is limited by several problems, including sluggish electrochemical kinetics and passivation at the Mg surface. In this study, we present a high-entropy electrolyte composed of lithium triflate (LiOTf) and trimethyl phosphate (TMP) co-added to magnesium bis(trifluoromethane sulfonyl)imide (Mg(TFSI)₂/1,2-dimethoxyethane (DME) to significantly improve the electrochemical performance of Mg-metal anodes. The as-formed high-entropy Mg²⁺-2DME-OTf⁻-Li⁺-DME-TMP solvation structure effectively reduced the Mg²⁺-DME interaction in comparison with that observed in traditional Mg(TFSI)₂/DME electrolytes, thereby preventing the formation of insulating components on the Mg-metal anode and promoting its electrochemical kinetics and cycling stability. Comprehensive characterization revealed that the high-entropy solvation structure brought OTf⁻ and TMP to the surface of the Mg-metal anode and promoted the formation of a Mg₃(PO₄)₂-rich interfacial layer, which is beneficial for enhancing Mg²⁺ conductivity. Consequently, the Mg-metal anode achieved excellent reversibility with a high Coulombic efficiency of 98 % and low voltage hysteresis. This study provides new insights into the design of electrolytes for Mg-metal batteries.     

Chromatographic separation of magnesium isotopes by monoazacrown bonded Merrifield peptide resins

Magnesium isotope separation was investigated by chemical ion exchange with the 1-aza-12-crown-4 (I) and the 1-aza-18-crown-6 (II) bonded Merrifield peptide resin using an elution chromatographic technique. The capacities of each novel monoazacrown ion exchanger were 1.0 meq/g for (I) and 2.3 meq/g for (II) bonded Merrifield peptide resins, respectively. The single stage separation factor was determined according to the method of Glueckauf from the elution curves and isotopic assays. The separation factors of magnesium isotope pairs, ²⁴Mg²⁺–²⁵Mg²⁺, ²⁴Mg²⁺–²⁶Mg²⁺ and ²⁵Mg²⁺–²⁶Mg²⁺ were 1.015, 1.029, and 1.014 for (I) and 1.012, 1.024, and 1.009 for (II) bonded Merrifield peptide resins, respectively.     

FT-IR and FT-Raman spectroscopy study of di-urethanesil hybrids doped with Mg(CF3SO3)2

In the present work di-urethane cross-linked poly(oxyethylene) (POE)/siloxane hybrids (di-urethanesils) incorporating magnesium triflate (Mg(CF₃SO₃)₂) with 100 ≥ n ≥ 2 (where n, composition, is the molar ratio of oxyethylene repeat units per Mg²⁺ ion) have been characterized by Fourier transform infrared and Raman spectroscopy to elucidate the Mg²⁺/POE, Mg²⁺/urethane, Mg²⁺/CF₃SO₃⁻ and hydrogen bonding interactions. The Mg²⁺ ions bond to POE chains and to the carbonyl oxygen atoms of the urethane linkages over the whole range of salt content studied. A crystalline POE/Mg(CF₃SO₃)₂ complex of unknown stoichiometry is formed at n = 5. “Free” and weakly coordinated CF₃SO₃⁻ ions are present in all the materials examined. Contact ion pairs emerge at n ≤ 20 and higher ionic aggregates appear at n ≤ 5.