Increase In Mg Research Articles

Effect of microwave sintering on synthesis and structural properties of nanocrystalline Mg–Cd ferrites

The magnesium–cadmium ferrites with chemical composition MgxCd1−xFe2O4 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) were synthesized by oxalate co-precipitation method using AR grade sulfates. The precipitates of oxalates were sintered using microwave sintering technique at optimized power 560 W for 10 min. These ferrites were characterized by X-ray diffraction, scanning electron microscope, field effect scanning electron microscope and Fourier transform infrared spectroscopy techniques. The formation of single phase cubic spinel structure of all the ferrites was confirmed by XRD analysis. The lattice constant of Mg–Cd ferrites was found to decrease with increasing Mg2+ content. The morphological study showed that the grain size of the ferrites was decreased with increase in Mg2+ content. The existence of two main strong absorption bands around 600 and 400 cm−1 corresponding to tetrahedral and octahedral complexes in the FTIR spectra confirmed the formation of ferrites. The remarkable change was observed in the parameters like lattice constant, average crystallite size, grain size and the porosity of the ferrites as compared to that reported by conventional sintering technique. The most useful outcome of microwave sintering technique was to yield the phase pure ferrites within short duration and low energy consumption.

Unraveling Mg2+-RNA binding with atomistic molecular dynamics.

Interaction with divalent cations is of paramount importance for RNA structural stability and function. We report here a detailed molecular dynamics study of all the possible binding sites for Mg2+ on an RNA duplex, including both direct (inner sphere) and indirect (outer sphere) binding. In order to tackle sampling issues, we develop a modified version of bias-exchange metadynamics, which allows us to simultaneously compute affinities with previously unreported statistical accuracy. Results correctly reproduce trends observed in crystallographic databases. Based on this, we simulate a carefully chosen set of models that allows us to quantify the effects of competition with monovalent cations, RNA flexibility, and RNA hybridization. Our simulations reproduce the decrease and increase of Mg2+ affinity due to ion competition and hybridization, respectively, and predict that RNA flexibility has a site-dependent effect. This suggests a nontrivial interplay between RNA conformational entropy and divalent cation binding.

Laboratory study of the influence of scCO2 injection on metals migration, precipitation, and microbial growth

Laboratory experiments were conducted to evaluate the impact of supercritical carbon dioxide (scCO2) injection on aqueous and solid phase geochemistry, and subsequent changes in permeability. These experiments showed that brine displacement from the Mount Simon Sandstone cores (∼1200m depth) by scCO2 was inefficient by advection, because the low viscosity scCO2 flows predominantly in larger pores, leaving a significant amount of brine in smaller pores. Acidification caused by scCO2 injection resulted in significant increases in Mg2+, K+, Na+, SO42− Al3+, and silica concentrations are likely from differing rates of carbonate, clay, albite, and K-feldspar dissolution. The mass of precipitates that formed over 1.2 years (NaCl, KCl, lead oxide, and forsterite) was small, as observed by electron microprobe analysis and did not influence permeability. Trace metals that increased during scCO2 injection included Ba, Mn, Sr, Ni, Sn, Bi, Cu, Li, P, and Zn, and trace metals that decreased included Hg, Pb, and Co. The scCO2 injection experiments also showed a moderate amount of particulate (iron oxide) movement correlated with the fraction of scCO2, but the sandstone permeability did not change, even after substantial (i.e., 115 pore volumes) scCO2 injection. Anaerobic and aerobic microbial growth was observed (23 and 14 times, respectively) correlated with higher scCO2 concentration, but the calculated change in pore space occupied by the increase in biomass is insignificant. The small observed geochemical and microbial changes are not expected to reduce the ability to inject scCO2 into the reservoir, but significant increases in trace metal concentrations could magnify the water quality impact of a potential leak of reservoir fluids into an overlying aquifer.

Influence of Mg components in hydroxylated calcined dolomite to (co-)precipitation of fluoride with apatites

Hydroxylated calcined dolomite (HCD) is practically used as a mineralizer to immobilize fluoride by co-precipitation with hydroxyapatite (HAp) and precipitation as fluoroapatite (FAp). It has an advantage to remove fluoride without stagnation, which is always observed with Ca(OH)2 alone. HCD includes a certain content of MgO and Mg(OH)2 as well as Ca(OH)2. In the present work, the mechanism to explain the enhancing role of Mg components on removal kinetics of fluoride was aimed to elucidate. Nano-domain observation approaches were conducted by TEM when Ca(OH)2 is added as a Ca source in the presence of different Mg2+ concentrations, instead of HCD. With increase in Mg2+ concentrations in the presence of Ca(OH)2, removal rate of fluoride was enhanced. The enhancement was also observed with HCD. Mg2+ and [Mg(OH)]+ species, which can be derived from HCD, are adhered to the negatively charged c-plane of freshly formed amorphous HAp/FAp and CaCO3. As a result, the surface of Ca(OH)2 particles are gotten rid of hetero-coagulation with HAp/FAp and CaCO3 in the presence of Mg2+ and [Mg(OH)]+ species, and maintained to release Ca2+ and OH− ions, facilitating to precipitate HAp and FAp for immobilization of fluoride. Without Mg2+ additives the Ca(OH)2 surfaces are blocked by insoluble HAp/FAp through hetero-coagulation. This interpretation is also supported by TEM observation, which is well consistent with XRD results. The findings indicate that MgO and Mg(OH)2 contents in HCD influence the removal kinetics of fluoride by (co-)precipitation as apatites in industrial water treatment. Understanding the surface science in nano-domain is important in parallel reactions of dissolution and precipitation.

Influence of Mg concentration on physico-chemical properties of Cd ferrites (CdMg1.5xFe2−xO4) synthesized by sol–gel combustion method

The nanofabrication, characterization, microstructural and magnetic properties of pure and Mg2+ doped cadmium ferrite (CdFe2−xMg1.5xO4; x=0.0–0.7) have been carried out. Morphology and the microstructure of the nanostructured oxide materials obtained through sol–gel process using hydrated metal-citrate precursor were studied by powder X-ray diffraction (XRD), electron microscopy (SEM, TEM) and N2-physisorption (BET) showing an ordered cubic arrangement of 11–23nm diameter pores with single-phase spinel grains averaging 13–38nm in diameter. Room temperature magnetic measurements using magnetometer (VSM) demonstrate that the nature and concentration of dopant both control the site preference in the crystal lattices, suggesting the partial inverted spinel structure of soft Cd ferrites, which differs from bulk CdFe2O4 showing practically no inversion in structure. An increase in Mg2+ substitution leads to a decrease in the lattice parameter, an increase in saturation magnetization as well as BET surface area of the as-synthesized ferrites.

An Investigation of Renal Function and Serum Magnesium Levels in Patients Receiving Day-Before Low-Volume Sodium Picosulfate and Magnesium Citrate Bowel Preparation

Introduction: Serum magnesium (Mg2+) levels are strictly maintained with a narrow range (0.7-1.05 mmol/L) via excretion by the kidney. Although rare, hypermagnesemia has been reported in patients receiving Mg2+-containing cathartics. Certain factors such as impaired renal function or age may be attributed to a higher risk for increases in serum Mg2+ levels. We performed a post hoc analysis using data from a pivotal clinical trial to assess whether renal function affects the safety of a Mg2+-containing bowel preparation. Methods: SEE CLEAR II was a phase 3 randomized, multicenter, assessor-blinded study that investigated day-before administration of a nonphosphate, dual-action, low-volume bowel preparation containing sodium picosulfate, magnesium oxide, and citric acid (P/MC) compared with conventional dosing of 2L polyethylene glycol solution and 2 5-mg bisacodyl tablets (2L PEG + bisacodyl tablets) in adults preparing for colonoscopy. In this post hoc analysis, serum Mg2+ levels in patients who received P/MC were analyzed and stratified by renal function (measured by creatinine clearance [CrCl] on the day of colonoscopy). Results: A total of 294 patients received day-before P/MC in the SEE CLEAR II study and were included in this analysis. Based on CrCl, patients were stratified into the following groups: ≥ 90 mL/min (63%), 60 to 89 mL/min (32%), and 30 to 59 mL/min (3%); patients with CrCl <30 mL/min were excluded from the study. On the day of colonoscopy, 91% of patients had serum Mg2+ concentrations within the normal range (see table). The mean Mg2+ concentration for patients with abnormal levels on the day of colonoscopy was just above the upper limit of normal (1.05 mmol/L). Of the 25 patients with abnormal Mg2+ on the day of colonoscopy, 10 were considered to have normal renal function (CrCl ≥ 90), while 15 had mild to moderate impairment (CrCl 30-90); however, mean Mg2+ concentrations were similar between these groups. Increases in Mg2+ were transient and returned to baseline for both the normal and abnormal Mg2+ groups within 24 to 48 hours post colonoscopy, regardless of renal function. Additionally, there were no reported adverse events due to hypermagnesemia. Conclusion: Serum Mg2+ concentrations in patients receiving P/MC are generally not affected by renal function. Moreover, elevated serum Mg2+ levels are not associated with an increase in adverse events. Disclosure: Supported by funding from Ferring Pharmaceuticals Inc, Parsippany, New Jersey. Editorial support was provided by The JB Ashtin Group, Inc. Disclosure - Dr Epstein has received grant/research support, participated in speakers’ bureaus, and/or acted as a consultant for Abbott Laboratories, Otsuka Pharmaceuticals, Promethius, and Sucampo. Dr Jones serves on the board of directors for Cytosorbents, Inc. Dr Bertiger has served as a consultant for Ferring Pharmaceuticals Inc. Dr Dahdal and Dr Joseph are employees of Ferring Pharmaceuticals Inc.Table 1: Serum Mg2+ Status on the Day of Colonoscopy, mmol/L

Performance of Proton Exchange Membrane in the Presence of Mg2+

Proton exchange membrane (PEM) fuel cell is regarded as one of the potential renewable energy which may provide a possible long-term solution to reduce carbon dioxide emissions, reduce fossil fuel dependency and increase energy efficiency. Even though great progress has been made, long-term stability and durability is still an issue. The contamination ion plays an important role on the electrical performance of PEM fuel cell. This paper investigates the effect of Mg2+ contamination on PEM fuel cell performance as a function of Mg2+ concentration. Two levels of Mg2+ concentration was chose. From the experimental results, it can be obtained that a significant drop in fuel cell performance occurred when Mg2+ was injected into the anode fuel stream. The voltage and power density of fuel cell decreased larger and larger with increase of Mg2+ concentration over time. The Mg2+ mainly caused the concentration polarization loss from the anode catalyst to the membrane in fuel cell.

Influence of scCO2 Injection on Precipitation and Metals Migration, and Changes in Electrical Resistivity

Laboratory experiments showed that low viscosity scCO2 displacement of the brine into Mt Simon Sandstone and Eau Clair formation cores (FutureGen 2.0 Geologic Sequestration site, Jacksonville, Illinois, USA) was slow by advection, as scCO2 travels predominantly in larger pores, leaving significant brine in smaller pores. As the scCO2 displaces the brine in larger pores and carbonate partitions into the brine, the resulting acidification (pH 3 to 4) causes short-term mineral dissolution, ion desorption, and iron oxide particulate movement. Major aqueous biogeochemical changes observed over 1.2 years from core/brine/scCO2 interactions includes: a) significant increase in Mg2+, K+, and SO4 concentrations (10s to 100s of mmol/L), b) dissolution of the hematite coating on the quartz grains, c) significant precipitation of NaCl and KCl, and d) some anaerobic microbial growth. Electron microprobe analysis showed the formation of some NaCl and KCl, but precipitates were too small a volume to significantly change permeability. Anaerobic microbial growth correlated with scCO2 (23.5x in 1300h), was also too small to influence permeability. Iron oxide particulate movement was observed as a result of scCO2 injection (acidification), but results could not conclusively correlate with formation permeability change. The electrical resistivity change of the rock core from 100% brine to 100% scCO2 was in the expected range (3x to 5x), with most of the change observed between 70% to 100% scCO2. Field scale conditions simulated using these laboratory-measured electrical resistivity changes indicated insufficient resolution was likely at the field site using surface electrodes due to the depth of injection (1200 m). Overall, injection of scCO2 into the brine-filled Mt Simon sandstone cores resulted in small geochemical and microbial changes over the short-term (< 1.5 years) with some iron oxide particulate movement.

The effect of medium chemistry on the solubility and morphology of brushite crystals

An experimental study of the particulars of the solubility and crystallization of brushite Ca(HPO4) · 2H2O from aqueous solution in conditions of a variable pH (6.0–3.0) and the contents of impurity ions (K+, Na+, NH 4 + , Mg2+, SO 4 2− , CO 3 2− ) has been conducted. It is established that brushite solubility markedly rises with a decrease in pH from 6 to 3 and slightly rises with an increase in Mg2+ and SO 4 2− concentrations. The enrichment in K+, Na+, and NH 4 + does not affect brushite solubility. The changeable chemistry of the medium results in variation of the synthetic crystal habit, from rhombic tabular to thickened prismatic crystals.

The Dead Sea Ecosystem Influenced by Red Sea – Dead Sea Conduit Project (Peace Conduit)

ABSTRACT Recently, the rapid drying out of the Dead Sea is one of the most challenging problems facing the scientists and governments of the region. Its level has dropped more than 20 m in the past decade. Massive precipitation of halite from the water column has led to a decrease in Na+ concentration, concomitant with an increase in Mg2+, making the lake supersaturated with NaCl. This situation presents a big challenge to the microbial life of the lake. However, despite these harsh conditions in the lake, several microorganisms, including members of the groups bacteria, unicellular algae, fungi, viruses, and Archaea, have been able to survive. To understand the factors that affect the microbes in the Dead Sea and to predict the possible effects of the planned conveyance of Red Sea water to the Dead Sea, a series of experiments were performed in the field, as well as in the laboratory. The results of the laboratory experiments showed that the growth of the Dunaliella was possible only when Dead Sea water was diluted with a minimum of 10% (by volume) Red Sea water. Addition of phosphate was essential for the algae to grow and growth rates and yields increased with increasing phosphate concentration and decreasing salinity. Field experiments revealed that the growth of algae was rapidly followed by the development of dense blooms of red halophilic Archaea. Although it should be realized that the closed system formed by the shallow ponds differs from the conditions in the lake, the results suggest that a microbial bloom, once formed, can remain present in the Dead Sea for months to years. These observations are important when attempting to predict how the biological properties of the lake may change in the future and they have important implications for the planning of the Red Sea- Dead Sea conduit. The “Peace Conduit”, a water carrier between the Red Sea and the Dead Sea, has been proposed to prevent the drying out of the lake and to restore the water level to a desired elevation. The present simulation experiments were designed at the Al Hussein bin Talal University (AHU) field station atMa’an to get information on the ecological impacts of the Dead Sea when the “Peace Conduit” plans are implemented and massive quantities of Red Sea water will enter the Dead Sea and lower the salinity of the upper water layers. Preliminary analysis was carried out of Fluorescence In Situ Hybridization (FISH) and Polar lipid of Archaea and Bacteria collected from the experimental ponds containing different Dead Sea-Red Sea water ratios, in order to analyze how they affect the microbial communities of the ponds. The Archaea community changed significantly according to the water mixture, presenting the greatest diversity when 30% Red Sea water was added to Dead Sea water.

Effect of magnesium content on structure and dielectric properties of cubic bismuth magnesium niobate pyrochlores

Structure and dielectric properties of cubic pyrochlore Bi1.5MgNNb2.5−NO8.5−1.5N (BMN) compositions with N=0.6–1.3 have been studied. X-ray diffraction (XRD), infrared reflectivity spectra and Raman spectra were employed to analyze the crystal structures and phonon vibration modes of BMN compositions. The vibration spectra were sensitive to the content of Mg2+ ions, which is caused by the randomness of Mg2+ ions partially filling both the cubic pyrochlore A and B sites. The intensity of A3O stretching vibrations became stronger with increasing Mg2+ content, but B3O stretching vibrations were quite opposite. With the increase of Mg2+ content, the dielectric constant and loss tangent both increased. Temperature dependent dielectric constant was observed in the samples with N>0.8. The tendency of the dielectric constant with the increasing temperature showed a quick drop in the samples with higher Mg2+ content, which seems to be associated with the disorder in the A2O′ network.

OH− absorption and nonvolatile holographic storage properties in Mg:Ru:Fe:LiNbO3 crystal as a function of Mg concentration

Mg:Ru:Fe:LiNbO3 crystals with various concentrations of MgO (in mole) and fixed content of RuO2 and Fe2O3 (in mass) are grown with the Czochralski method from the congruent melt. Their infrared transmission spectra are measured and discussed to investigate the defect structure. With the increase of Mg2+ concentration the blue nonvolatile holographic storage capability is enhanced. The nonvolatile holographic storage properties of dual-wavelength recording of Mg(7 mol%):Ru:Fe:LiNbO3 nonvolatile diffraction efficiency, response time, and nonvolatile sensitivity reach 59.8%, 70 s, and 1.04 cm/J, respectively. Comparing Mg(7 mol%):Ru:Fe:LiNbO3 with Ru:Fe:LiNbO3 crystal, the response time is shortened apparently. The nonvolatile diffraction efficiency and sensitivity are raised largely. The mechanism in blue photorefractive nonvolatile holographic storage is discussed.

Factors influencing urease driven struvite precipitation

The concern about phosphorus depletion is driving more efficient phosphorus use and recycling. In this context the precipitation of phosphate as struvite from wastewaters has recently gained considerable traction. This study investigates the influence of different parameters on the ureolytic phosphate precipitation (pH increase by means of urease activity). Wastewater with a high phosphate concentration (>50mgL−1 PO4–P) and low volatile suspended solids (⩽3.0gL−1 VSS) resulted in a high phosphate removal efficiency (87%) and struvite crystals that could be separated from the sludge. An increase in ionic strength resulted in a decrease in ureolytic activity. An increase in Mg2+:PO43- molar ratio increases the degree of supersaturation with respect to struvite formation, which enhances the phosphate removal. Above a Mg2+:PO43- molar ratio of 3, additional Mg2+ dosage did not significantly affect the phosphate removal efficiency. Wastewater containing low phosphate concentrations (<50mgL−1 PO4–P), needed disproportionally large chemical additions and are thus not economically rewarding. For those wastewaters the presence of calcium interfered with the struvite precipitation rendering the precipitation of calcium phosphate a better option.

Ионы Mg2+влияют на структуру центрального домена 18S рРНК вблизи участка связывания рибосомного белка S13

It is known that Mg2+ ions at high concentrations stabilize the structure of the 16S rRNA in a conformation favorable for binding to the ribosomal proteins in the course of the eubacterial 30S ribosomal subunits assembly in vitro. Effect of Mg2+ on the formation of the 18S rRNA structure at the 40S subunit assembly remains poorly explored. In this paper, we show that the sequentional increase of the Mg2+ concentration from 0.5 mM to 20 mM leads to a significant decrease of the affinity of recombinant human ribosomal protein S13 (rpS13e) to a RNA transcript corresponding to the central domain fragment of the 18S rRNA (18SCD). The regions near the rpS13e binding site in 18SCD (including the nucleotides of helices H20 and H22), whose availabilities to hydroxyl radicals were dependent on the Mg2+ concentration, were determined. It was found that increase of the concentrations of Mg2+ results in the enhanced accessibilities of nucleotides G933-C937 and C1006-A1009 in helix H22 and reduces those of nucleotides A1023, A1024, and A1028-S1026 in the helix H20. Comparison of the results obtained with the crystallographic data on the structure of the central domain of 18S rRNA in the 40S ribosomal subunit led to conclusion that increase of Mg2+ concentrations results in the reorientation of helices H20 and H24 relatively helices H22 and H23 to form a structure, in which these helices are positioned the same way as in 40S subunits. Hence, saturation of the central domain of 18S rRNA with coordinated Mg2+ ions causes the same changes in its structure as rpS13e binding does, and leads to decreasing of this domain affinity to the protein.

Preliminary Study on Cytotoxic Effect of Biodegradation of Magnesium on Cancer Cells

Biodegradation of magnesium (Mg) based metals in body fluid can lead to a strong alkalinity as well as an increase of Mg2+ concentration in its surrounding environment. In vitro cytotoxic effects of the extracts of pure Mg with and without micro arc oxidation (MAO) coating on osteosarcoma U2-OS cells, a kind of bone cancer cells, were preliminarily studied, independently considering the increase of either alkalinity or Mg2+ concentration. The results indicated that the high alkalinity, i.e., a great increase of pH value, caused by the degradations of Mg with and without MAO coating in the culture medium all showed strong cytotoxic effects on U2-OS cells. However, the increase of Mg2+ concentration had no such cytotoxic effect. This finding may provide an alternative way to cure bone cancers through creating a high alkalinity surrounding the cancer cells.

Abstract 218: TRPM7 Kinase - A Novel Signaling Pathway for Ang II-induced MAPK Activation in Vascular Smooth Muscle Cells.

Transient receptor potential melastatin 7 (TRPM7) cation channel is a unique protein, which regulates transmembrane magnesium (Mg2+) transport through its channel domain, and intracellular signaling through its kinase domain. We previously demonstrated that TRPM7, is expressed on vascular smooth muscle cells (VSMC), controls Mg2+ influx, and is regulated by angiotensin II (Ang II). Low Mg2+ levels are among the many factors leading to hypertension, where intracellular Mg2+ deficiency and TRPM7 downregulation is observed. Despite the advancement in the understanding of Mg2+ and TRPM7 biology, the role of TRPM7, and its kinase, in hypertension remains elusive. In this study, we investigated whether deletion of TRPM7 kinase domain alters Ang II-induced Mg2+ influx and signaling in VSMCs. Cultured VSMCs from mesenteric arteries obtained from heterozygous mice for the TRPM7 kinase deletion (+/-) and WT mice were used. Mg2+ influx was assessed by fluorescence microscopy. Activation of MAP kinases was evaluated by immunoblotting. Ang II (10-7M) increase in Mg2+ influx was similar in VSMC from both, WT and TRPM7+/- mice (2.5-fold; p&lt;0.001). Ang II increased phosphorylation of JNK (10-fold), p38MAPK (4-fold) and ERK1/2 (6.4-fold) in VSMC from WT mice (p&lt;0.001). Ang II-induced MAPK activation was blunted in TRPM7+/- VSMC. Moreover, Ang II treatment induced PDGF-R (2-fold) and Akt phosphorylation (3-fold) in VSMC from WT mice (p&lt;0.05), an effect that was also blunted in TRPM+/- VSMC. Ang II induced SMAD2/3 activation in VSMC from WT (1.5-fold; p&lt;0.05) and, with a greater extent, TRPM7+/- mice (3.5-fold; p&lt;0.05). To understand whether the blunted effects of Ang II on intracellular signaling in VSMC from TRPM7+/- mice could be attributed to downregulation of Ang II receptors, AT1R and AT2R expression was assessed. No differences in receptor expression were observed between VSMC from WT and TRPM+/-. In conclusion, our findings identify that TRPM7 kinase domain is not necessary for Mg2+ influx, but it seems to be a novel and important player in Ang II-induced signaling in VSMCs.

Study on the Effect of Magesium Ion on the Crystal Phase of Calcium Carbonate

Morphology and crystal phase of calcium carbonate, which formed with the presence of Mg2+, were characterized by SEM and XRD. The effect of Mg2+ on crystallization and crystal phase of calcium carbonate was studied. The results showed that the crystal phase of calcium carbonate were mainly calcite and aragonite and the content of aragonite was higher after adding Mg2+ to the blank solution. With the increase of Mg2+ concentration, the content of aragonite increased. The calcium carbonate crystals grain became more fine and the content of aragonite was higher by synergistic treatment between Mg2+ and magnetic field. There was a strong inhibitory effect on calcite when the concentration of Mg2+ was more than 0.50mmol.L-1. The calcite could be transformed into aragonite in the presence of Mg2+ in solution.

Differential Effects of Cyclosporin A and Tacrolimus on Magnesium Influx in Caco2 Cells

Hypomagnesemia with urinary magnesium (Mg) wasting is a well acknowledged side effect of cyclosporin A (CsA) and tacrolimus (FK506) treatments. TRPM6, TRPM7 and MagT1 are involved in the active transcellular Mg transport processes in intestine and kidney. Since Mg homeostasis is tightly controlled by the dynamic action of intestinal absorption of dietary Mg and renal excretion of Mg, we investigated whether CsA and FK506 in commercially available solutions for clinical use decrease the expression and the function of TRPM6, TRPM7 or MagT1 in the intestinal epithelial cell line Caco2. Changes of intracellular free Mg concentrations were measured by Mag-fura-2 imaging in Mg-free medium after the addition of 1 mM MgCl2. TRPM6, TRPM7 and MagT1 were evidenced in cells by immunofluorescence. Proteins and mRNAs were quantified after 18 hours of treatment with CsA or FK506 by western-blot and real-time RT-PCR analyses, respectively. TRPM6 and MagT1 were evidenced on all cell membranes, TRPM7 only on the inner membranes. CsA was responsible for a profound decrease in Mg2+ influx in intestinal epithelial cells, which may result in a decrease of intestinal Mg absorption, whereas FK506 was responsible for a marked increase in Mg2+ influx. Neither CsA nor FK506 altered TRPM6, TRPM7 or MagT1 mRNA levels or MagT1 protein level. In Caco2 cells, Mg2+ influx was inhibited by CsA solutions whereas enhanced by FK506 solutions, without alteration of MagT1, TRPM6 and TRPM7 expression, leading to the conclusion that CsA and FK506 have opposite effects in the functional activity of the Mg transporters herein examined. In clinical use, FK506 should be preferred for patients at risk for hypomagnesemia.

Thermodynamic examination of U6 ISL bulged RNA

A highly conserved bulge in the internal stem‐loop (ISL) of the U6 subunit of the spliceosome is responsible for its assembly and catalysis. This pH dependent bulge has an unpaired U80 nucleotide stacked within the helix that causes a bend in the RNA at pH 7.0. At a lower pH the flanking A•C base pair becomes protonated (forming an A+•C base pair) causing U80 to be flipped out into the major groove allowing the RNA to take up a conformation close to A‐form helix. We tested constructs containing the conserved bulged nucleotides as well as those with modifications in both the bulged and flanking helical nucleotides in 1 M KCl and in varying Mg2+ concentrations at pH of 5.5 and 7.5. Only constructs containing the A•C pair showed a gain in stability at pH 5.5 over 7.5. All constructs, with one exception, showed an increase in stability with increase in Mg2+ concentrations. RNA constructs also show greater gain in stability in the presence of Mg2+ than DNA constructs. Our results confirm that lowering the pH allows for the formation of an A+•C base pair in 1 M KCl and in 0.5 to 9.5 mM Mg2+ giving an extra stability of more than 1 kcal/mol in the wild type construct. This work was funded by NSF Grant MCB‐ 0950582 to NG.

Adsorption of Low-Concentration Ammonium Onto Vermiculite from Hebei Province, China

AbstractVermiculite is a common layered silicate clay mineral which has good adsorption and ion-exchange properties, and which is used to remove pollutants from groundwater. The adsorption by vermiculite from Heibei Province, China, of low-concentration ammonium in water was assessed here to evaluate the effects of adsorption time, particle size, adsorbent dose, pH, and temperature. Using Fourier-transform infrared spectroscopy, the concentration of NH4+ at 1430 cm−1 was evaluated after ammonium was adsorbed by vermiculite. Based on Langmuir-model analysis, the adsorption capacity of the Chinese vermiculite (in the particle-size range 0.025–0.075 mm) for ammonium was 18 mg/g after 3 h of equilibration. Optimal adsorption occurred at pH 6–7 and 60°C, which is different from that at high ammonium concentrations. Smaller particle-size fractions showed greater degrees of adsorption. Increase in Mg2+, K+, or Na+ concentrations influenced ammonium adsorption and, therefore, indicated that cation exchange was the mechanism for ammonium uptake from low-concentration solutions.