The concentration of chloride ions in the cytoplasm and subcellular organelles of living cells spans a wide range (5-130 mM), and is tightly regulated by intracellular chloride channels or ...transporters. Chloride-sensitive protein reporters have been used to study the role of these chloride regulators, but they are limited to a small range of chloride concentrations and are pH-sensitive. Here, we show that a DNA nanodevice can precisely measure the activity and location of subcellular chloride channels and transporters in living cells in a pH-independent manner. The DNA nanodevice, called Clensor, is composed of sensing, normalizing and targeting modules, and is designed to localize within organelles along the endolysosomal pathway. It allows fluorescent, ratiometric sensing of chloride ions across the entire physiological regime. We used Clensor to quantitate the resting chloride concentration in the lumen of acidic organelles in Drosophila melanogaster. We showed that lumenal lysosomal chloride, which is implicated in various lysosomal storage diseases, is regulated by the intracellular chloride transporter DmClC-b.
Chloride binding is investigated for Portland cement–metakaolin–limestone pastes exposed to CaCl2 and NaCl solutions. The phase assemblages and the amount of Friedel's salt are evaluated using TGA, ...XRD and thermodynamic modeling. A larger amount of Friedel's salt is observed in the metakaolin blends compared to the pure Portland cement. A higher total chloride binding is observed for the pastes exposed to the CaCl2 solution relative to those in the NaCl solution. This is reflected by the fact that calcium increases the quantity of Friedel's salt in the metakaolin blends by promoting the transformation of strätlingite and/or monocarbonate to Friedel's salt. Calcium increases also the amount of chloride in the diffuse layer of the C-S-H for the pure cement. A linear correlation between the total bound chloride and the uptake of calcium from the CaCl2 solution is obtained and found to be independent on the type of cement blend.
Benzalkonium chlorides (BACs) are chemicals with widespread applications due to their broad-spectrum antimicrobial properties against bacteria, fungi, and viruses. This review provides an overview of ...the market for BACs, as well as regulatory measures and available data on safety, toxicity, and environmental contamination. We focus on the effect of frequent exposure of microbial communities to BACs and the potential for cross-resistant phenotypes to emerge. Toward this goal, we review BAC concentrations in consumer products, their correlation with the emergence of tolerance in microbial populations, and the associated risk potential. Our analysis suggests that the ubiquitous and frequent use of BACs in commercial products can generate selective environments that favor microbial phenotypes potentially cross-resistant to a variety of compounds. An analysis of benefits versus risks should be the guidepost for regulatory actions regarding compounds such as BACs.
CLC family genes, comprising anion channels and anion/H+ antiporters, are widely represented in nearly all prokaryotes and eukaryotes. CLC proteins carry out a plethora of functions at the cellular ...level. Here the coding sequences of the SaCLCa2 and SaCLCc2 genes, homologous to Arabidopsis thaliana CLCa and CLCc, were cloned from the euhalophyte Suaeda altissima (L.) Pall. Both the genes cloned belong to the CLC family as supported by the presence of the key conserved motifs and glutamates inherent for CLC proteins. SaCLCa2 and SaCLCc2 were heterologously expressed in Saccharomyces cerevisiae GEF1 disrupted strain, Δgef1, where GEF1 encodes the only CLC family protein, the Cl− transporter Gef1p, in undisrupted strains of yeast. The Δgef1 strain is characterized by inability to grow on YPD yeast medium containing Mn2+ ions. Expression of SaCLCa2 in Δgef1 cells growing on this medium did not rescue the growth defect phenotype of the mutant. However, a partial growth restoration occurred when the Δgef1 strain was transformed by SaCLCa2(C544T), the gene encoding protein in which proline, specific for nitrate, was replaced with serine, specific for chloride, in the selectivity filter. Unlike SaCLCa2, expression of SaCLCc2 in Δgef1 resulted in a partial growth restoration under these conditions. Analysis of SaCLCa2 and SaCLCc2 expression in the euhalophyte Suaeda altissima (L.) Pall by quantitative real-time PCR (qRT-PCR) under different growth conditions demonstrated stimulation of SaCLCa2 expression by nitrate and stimulation of SaCLCc2 expression by chloride. The results of yeast complementation assay, the presence of both the “gating” and “proton” glutamates in aa sequences of both the proteins, as well results of the gene expression in euhalophyte Suaeda altissima (L.) Pall suggest that SaCLCa2 and SaCLCc2 function as anion/H+ antiporters with nitrate and chloride specificities, respectively. The general bioinformatic overview of seven CLC genes cloned from euhalophyte Suaeda altissima is given, together with results on their expression in roots and leaves under different levels of salinity.
Well hydrated cement paste was exposed to MgCl2, CaCl2 and NaCl solutions at 20°C. The chloride binding isotherms for free chloride concentrations ranging up to 1.5mol/l were determined ...experimentally. More chlorides were found to be bound when the associated cation was Mg2+ or Ca2+ compared to Na+. The chloride binding capacity of the paste appeared to be related to the pH of the exposure solution. In order to explain the cation dependency of the chloride binding a selection of samples was investigated in detail using experimental techniques such as TG, XRD and SEM–EDS to identify the phases binding the chlorides. The experimentally obtained data were compared with the calculations of a thermodynamic model, GEMS. It was concluded that the measured change in chloride binding depending on the cation was mainly governed by the pH of the exposure solution and thereby the binding capacity of the C-S-H.
An experimental investigation has been performed where the influence of metal salts on soot formation has been studied. By combining two-dimensional laser-induced incandescence (LII) and elastic ...light scattering (ELS), two-dimensional information could be obtained on soot properties in the flames. For these studies, seven metal salts (NaCl, MgCl2, AlCl3, KCl, CaCl2, FeCl3 and ZnCl2) were dissolved in water and aspirated into a premixed ethylene/air flame. At lower flame heights, in the soot inception region, the LII signal (representing soot volume fraction) was marginally affected by all additives, whereas the ELS signal strongly decreased with increasing additive concentration for the alkali salts. At higher heights, in the soot growth region, the soot volume fractions were lowered for the addition of potassium, calcium and sodium chloride, in order of significance. Some of the salts (MgCl2, AlCl3 and FeCl3) resulted in negligible influence on LII signals and slightly higher ELS signals throughout the flames, and we relate the increased ELS signals to salt particles propagating through the flame. Main focus in our study was on the addition of potassium chloride for which several parameters were investigated. For example, soot primary particle sizes were evaluated using combined LII and ELS, showing decreasing particle sizes for increasing concentrations of potassium, in reasonable agreement with particle sizes evaluated using transmission electron microscopy. Also, CARS thermometry showed slightly higher flame temperature, ∼30 K, for the potassium-seeded flame compared to the reference flame.
Acid-sensing ion channels have important functions in physiology and pathology, but the molecular composition of acid-activated chloride channels had remained unclear. We now used a genome-wide siRNA ...screen to molecularly identify the widely expressed acid-sensitive outwardly-rectifying anion channel PAORAC/ASOR. ASOR is formed by TMEM206 proteins which display two transmembrane domains (TMs) and are expressed at the plasma membrane. Ion permeation-changing mutations along the length of TM2 and at the end of TM1 suggest that these segments line ASOR's pore. While not belonging to a gene family, TMEM206 has orthologs in probably all vertebrates. Currents from evolutionarily distant orthologs share activation by protons, a feature essential for ASOR's role in acid-induced cell death. TMEM206 defines a novel class of ion channels. Its identification will help to understand its physiological roles and the diverse ways by which anion-selective pores can be formed.
A poly(vinyl chloride) (PVC) main chain was grafted with poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) containing a quaternary amine group using atom transfer radical polymerization. The ...successful synthesis of a PVC-g-PDMAEMA graft copolymer was confirmed by Fourier transform infrared, nuclear magnetic resonance, thermogravimetric analysis, and transmission electron microscopy. The PVC-g-PDMAEMA graft copolymer was used as a structure-directing agent (SDA) for the fabrication of a mesoporous thin film containing a titanium dioxide (TiO sub(2)) layer. To control the porosity of the resultant inorganic layer, the ratio of SDA to TTIP as well as the concentration of the sol-gel was varied. The structure and porosity of the mesoporous film were characterized by XRD and SEM analysis. The mesoporous TiO sub(2) film fabricated on the FTO surface was used as a photoanode for the dye-sensitized solar cell (DSSC). DSSC performance was the greatest when using TiO sub(2) film with a higher porosity and lower interfacial resistance. The highest energy conversion efficiency reached 3.2 % at 100 mW/cm super(2), which was one of the highest reported values for a quasi-solid-state DSSC with 600-nm-thick TiO sub(2) film.
The translational diffusivity of water in solutions of alkali halide salts depends on the identity of ions, exhibiting dramatically different behavior even in solutions of similar salts of NaCl and ...KCl. The water diffusion coefficient decreases as the salt concentration increases in NaCl. Yet, in KCl solution, it slightly increases and remains above bulk value as salt concentration increases. Previous classical molecular dynamics simulations have failed to describe this important behavior even when polarizable models were used. Here, we show that inclusion of dynamical charge transfer among water molecules produces results in a quantitative agreement with experiments. Our results indicate that the concentration-dependent diffusivity reflects the importance of many-body effects among the water molecules in aqueous ionic solutions. Comparison with quantum mechanical calculations shows that a heterogeneous and extended distribution of charges on water molecules around the ions due to ion-water and also water-water charge transfer plays a very important role in controlling water diffusivity. Explicit inclusion of the charge transfer allows us to model accurately the difference in the concentration-dependent water diffusivity between Na(+) and K(+) ions in simulations, and it is likely to impact modeling of a wide range of systems for medical and technological applications.
Light-driven chloride-pumping rhodopsins actively transport anions, including various halide ions, across cell membranes. Recent studies using time-resolved serial femtosecond crystallography ...(TR-SFX) have uncovered the structural changes and ion transfer mechanisms in light-driven cation-pumping rhodopsins. However, the mechanism by which the conformational changes pump an anion to achieve unidirectional ion transport, from the extracellular side to the cytoplasmic side, in anion-pumping rhodopsins remains enigmatic. We have collected TR-SFX data of
rhodopsin-3 (NM-R3), derived from a marine flavobacterium, at 10-µs and 1-ms time points after photoexcitation. Our structural analysis reveals the conformational alterations during ion transfer and after ion release. Movements of the retinal chromophore initially displace a conserved tryptophan to the cytoplasmic side of NM-R3, accompanied by a slight shift of the halide ion bound to the retinal. After ion release, the inward movements of helix C and helix G and the lateral displacements of the retinal block access to the extracellular side of NM-R3. Anomalous signal data have also been obtained from NM-R3 crystals containing iodide ions. The anomalous density maps provide insight into the halide binding site for ion transfer in NM-R3.
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