Low Salt Solution Research Articles

Electrostatic Environment of Proteorhodopsin Affects the pKa of Its Buried Primary Proton Acceptor

The protonation state of embedded charged residues in transmembrane proteins (TMPs) can control the onset of protein function. It is understood that interactions between an embedded charged residue and other charged or polar residues in the moiety would influence its pKa, but how the surrounding environment in which the TMP resides affects the pKa of these residues is unclear. Proteorhodopsin (PR), a light-responsive proton pump from marine bacteria, was used as a model to examine externally accessible factors that tune the pKa of its embedded charged residue, specifically its primary proton acceptor D97. The pKa of D97 was compared between PR reconstituted in liposomes with different net headgroup charges and equilibrated in buffer with different ion concentrations. For PR reconstituted in net positively charged compared to net negatively charged liposomes in low-salt buffer solutions, a drop of the apparent pKa from 7.6 to 5.6 was observed, whereas intrinsic pKa modeled with surface pH calculated from Gouy-Chapman predictions found an opposite trend for the pKa change, suggesting that surface pH does not account for the main changes observed in the apparent pKa. This difference in the pKa of D97 observed from PR reconstituted in oppositely charged liposome environments disappeared when the NaCl concentration was increased to 150 mM. We suggest that protein-intrinsic structural properties must play a role in adjusting the local microenvironment around D97 to affect its pKa, as corroborated with observations of changes in protein side-chain and hydration dynamics around the E-F loop of PR. Understanding the effect of externally controllable factors in tuning the pKa of TMP-embedded charged residues is important for bioengineering and biomedical applications relying on TMP systems, in which the onset of functions can be controlled by the protonation state of embedded residues.

Validation of preferred salt concentration in soup based on a randomized blinded experiment in multiple regions in Japan\u2014influence of umami (l-glutamate) on saltiness and palatability of low-salt solutions

Sodium reduction is an important public health goal. Individual and population approaches are necessary for reducing the sodium content of processed foods and meals. The aim of the present study is to affirm the effect of monosodium l-glutamate (MSG), an umami substance, on the saltiness or palatability of low-salt solutions and to explore the preferred salt concentration in soup. Five hundred and eighty-four healthy participants from nineteen regions in Japan tasted 0.3, 0.6, and 0.9% NaCl solutions with or without 0.3% MSG. Evaluations of saltiness and palatability for each solution were conducted using a visual analog scale in a double-blinded randomized manner. Saltiness gradually increased depending on the concentration of NaCl. The saltiness of the 0.3% NaCl solution with MSG was rated significantly higher than that without MSG. The palatability ratings were higher for the solutions with MSG than for those without MSG for all NaCl concentrations. In particular, the palatability rating of the 0.3% NaCl solution with MSG was twice as high as that without MSG and was significantly higher than that of the other five test solutions. Furthermore, these results were observed to be approximately the same, irrespective of sex, age, region, etc. Salt reduction is believed to result in a loss of palatability. However, our results suggest that umami can compensate for the loss of palatability caused by salt reduction and that the addition of an appropriate amount of an umami substance can facilitate salt reduction from 0.9 to 0.3% without sacrificing palatability.

Hybrid capacitor with anthraquinone-grafted carbon as a battery-type electrode operating in a low pH aqueous salt solution

The aqueous hybrid capacitor made of a positive EDL carbon electrode and its battery-type counterpart obtained by grafting of anthraquinone moieties competes advantageously in terms of energy, safety and cost with traditional symmetric EDLCs in organic electrolyte.

Viruses Of Extreme Environments

Abstract Extremophilic viruses inhabit even the most extreme environments, such as underwater and terrestrial hydrothermal vents, deserts, subpolar areas, deep subsurface sediments, hypersaline environments, and alkaline lakes. These are mainly viruses that infect bacteria (belonging to the Myoviridae and Siphoviridae families) and archaea (classified to the families Lipothrixviridae, Rudiviridae, Yueviridae, Ampullaviridae, Globuloviridae, Sphaerolipoviridae, Bicaudaviridae, Fuselloviridae, Guttaviridae, Clavaviridae, and Turriviridae), some of which have not been fully classified. Extremoviruses have genetic material mainly in the form of dsDNA, both circular and linear, whose average length varies between 14 and 80kbp and is optimal because it is not degraded by high or low temperature, salt solutions or elevated pressure, and encodes all features necessary to function in extreme conditions. This also confirms the much higher resistance of DNA to external factors compared to delicate RNA. Further studies on extremophilic viruses can lead to full sequencing of their genomes, recognition of genes determining resistance traits to unfavorable environmental conditions, and a closer understanding of the full history of the evolution of organisms on Earth. 1. Introduction. 2. Viruses of extremely high temperatures. 2.1. Viruses of hot terrestrial springs. 2.2. Viruses of deep-sea hydrothermal vents. 3. Viruses of deserts. 4. Viruses of subpolar areas. 5. Viruses of subsurface sediments. 6. Viruses of hypersaline areas. 6.1. Viruses of freshwater lakes. 6.2 Viruses of alkaline lakes. 7. Conclusions

Transport of biochar colloids in saturated porous media in the presence of humic substances or proteins

Application of biochar in the field has received considerable attention in recent years, but there is still little known about the fate and transport of biochar colloids (BCs) in the subsurface. Natural organic matter (NOM), which mainly consists of humic substance (HS) and proteins, is ubiquitous in the natural environment and its dissolved fraction is active and mobile. In this study, the transport of BCs in saturated porous media has been examined in the presence of two HS (humic and fulvic acids) and two proteins. Bull serum albumin (BSA) and Cytochrome c (Cyt) were selected to present the negatively and positively charged protein, respectively. At low and high salt concentration and different pH conditions, the transport of BCs was strongly promoted by HS. HS significantly increased the mobility of BCs in porous media under both low and high salt conditions due to the enhanced electrostatic repulsion and modification of surface roughness and charge heterogeneity. While BC mobility in porous media was suppressed by both BSA and Cyt in the low salt solution, the presence of BSA largely promoted and Cyt slightly enhanced the transport of BCs in high salt solutions. BSA and Cyt adsorption onto BC surface decreased the negative charge of BC and resulted in a less repulsive interaction in low salt solutions. In high salt solutions, the adsorbed BSA layers disaggregated BCs and reduced the strength of the interaction between BC and the sand. Adsorbed Cyt on BCs caused more attractive patches between BC and sand surface, and greater retention than BSA.

Delivery of nucleic acids to ex vivo porcine airways using electrospray

Aim of the Study: Nucleic acid-based therapies have the potential to provide clinically meaningful benefit across a wide spectrum of lung disease. However, in vivo delivery remains a challenge. Here we examined the feasibility of using electrospray to deliver nucleic acids to both porcine tracheal tissue sections and whole lung ex vivo. Materials and Methods: The effect of electrospray solution, emitter gauge, flow rate and voltage on plasmid DNA integrity was examined by analyzing supercoiled:open circle structure ratio by gel electrophoresis. Optimal parameters were used to deliver luciferase DNA and mRNA and siRNA-FITC to tracheal tissue sections. Luciferase mRNA was delivered to whole porcine lungs ex vivo using a catheter and bronchoscope system. Luciferase activity and fluorescence were analyzed by luminometry and microscopy respectively. Results: The incidence of DNA plasmid nicking was greatest in a low salt solution without ethanol compared with 1% and 20% ethanol with salt. From a range of emitters tested, a 32 gauge emitter produced the best supercoiled:open circle structure ratio, likely because less voltage was required to produce a stable electrospray with this emitter. Lower flow rates also showed a trend towards reduced DNA nicking. GFP DNA electrosprayed at 5 kV and 6 kV resulted in lower levels of GFP expression in A549 lung cells following lipofection compared with 3 kV and 4 kV. Optimised parameters of 20% ethanol solution, 32 gauge emitter, low flow rates and voltages of 3–5 kV, nucleic acid molecules were successful for delivery of luciferase DNA and mRNA as well as siRNA-FITC to porcine tracheal tissue sections and for delivery of luciferase mRNA to whole porcine lungs via bronchoscope. Conclusions: We report ex vivo delivery of nucleic acids to porcine lung tissue via electrospray and bronchoscopic electrospray delivery of nucleic acid to an ex vivo porcine lung model.

Functional roles of C-terminal extension (CTE) of salt-dependent peptidase activity of the Natrialba magadii extracellular protease (NEP)

Nep (Natrialba magadii extracellular protease) is a halolysin-like peptidase secreted by the haloalkaliphilic archaeon Natrialba magadii. Many extracellular proteases have been characterized from archaea to bacteria as adapted to hypersaline environments retaining function and stability until 4.0M NaCl. As observed in other secreted halolysins, this stability can be related to the presence of a C-terminal extension (CTE) sequence. In the present work, we compared the biochemical properties of recombinant Nep protease with the truncated form at the 134 amino acids CTE (Nep∆CTE), that was more active in 4M NaCl than the non-truncated wild type enzyme. Comparable to the wild type, Nep∆CTE protease is irreversibly inactivated at low salt solutions. The substrate specificity of the truncated Nep∆CTE was similar to that of wild type form as demonstrated by a combinatorial library of FRET substrates. The enzyme stability, the effect of different salts and the thermodynamics assays using different lengths of substrates demonstrated similarities between the two forms. Altogether, these data provide further information on the stability and structural determinants of halolysins under different salinities, especially concerning the enzymatic behavior.

Ionic Conductivity of Polyelectrolyte Hydrogels.

Polyelectrolytes have many important functions in both living organisms and man-made applications. One key property of polyelectrolytes is the ionic conductivity due to their porous networks that allow the transport of water and small molecular solutes. Among polyelectrolytes, zwitterionic polymers have attracted huge attention for applications that involve ion transport in a polyelectrolyte matrix; however, it is still unclear how the functional groups of zwitterionic polymer side chains affect their ion transport and swelling properties. In this study, zwitterionic poly(carboxybetaine acrylamide), poly(2-methacryloyloxyethyl phosphorylcholine), and poly(sulfobetaine methacrylate) hydrogels were synthesized and their ionic conductivity was studied and compared to cationic, anionic, and nonionic hydrogels. The change of the ionic conductivity of zwitterionic and nonionic hydrogels in different saline solutions was investigated in detail. Zwitterionic hydrogels showed much higher ionic conductivity than that of the widely used nonionic poly(ethylene glycol) methyl ether methacrylate hydrogel in all tested solutions. For both cationic and anionic hydrogels, the presence of mobile counterions led to high ionic conductivity in low salt solutions; however, the ionic conductivity of zwitterionic hydrogels surpassed that of cationic and ionic hydrogels in high salt solutions. Cationic and anionic hydrogels showed much higher water content than that of zwitterionic hydrogels in deionized water; however, the cationic hydrogels shrank significantly with increasing saline concentration. This work provides insight into the effects of polyelectrolyte side chains on ion transport. This can guide us in choosing better polyelectrolytes for a broad spectrum of applications, including bioelectronics, neural implants, battery, and so on.

Novel melamine modified metal-organic frameworks for remarkably high removal of heavy metal Pb (II)

Novel melamine modified metal-organic frameworks (melamine-MOFs) were synthesized and then used as an absorbent for the removal of heavy metal Pb (II) from a low-salt solution. The melamine-MOFs showed high-intensity x-ray diffraction peaks and a UiO-66-like structure. It has a sphere-like morphology and a diameter of ~50nm. The interactions between melamine and the MOFs were calculated by time dependent density function theory (TD-DFT), showing that there were charge transfer and orbital switching. Fourier transform infrared (FTIR) analysis showed successful incorporation of the melamine into the MOFs upon chemical reaction. Thermal gravimetric analysis (TGA) showed a limited weight-loss before 350°C, indicating that the melamine was not physically mixed with the MOFs. Effects of adsorption time, pH, and temperature (T) were also investigated. The melamine-MOFs showed higher adsorption capacity (122.0mgg−1) than that of the pristine MOFs (72.1mgg−1) at 120min, 40°C and pH=5. The adsorption capacity was remarkably high (about 205mgg−1) at pH of 6. The pseudo-second-order kinetic model fit the adsorption data best (R2>0.99). The adsorption mechanisms were confirmed as the coordination interaction between the amino groups (–NH2) and Pb (II). Therefore, the melamine-MOFs demonstrated a great potential in the treatment of heavy metal wastewater.

The Effect of Concentration on the Pressure of a Sodium Chloride Solution Inside Dialysis Tubing

High blood pressure causes significant medical problems around the world such as strokes, blindness and even death. Many people with high blood pressure are asked to lower their intake of salt in their diet which led us to wonder how blood pressure changes with more salt in the body and how the kidney diffuses water in response to salt concentration in the blood. Chemically, the salt outside of the blood vessels affects the pressure inside of the blood vessels due to the movement of water across the vessel walls. We used dialysis tubing containing a 0.9% salt-water solution to simulate the standard concentration of sodium chloride in the blood vessels. These simulated blood vessels were then placed in high and low salt solutions and a gas pressure sensor was used to monitor pressure changes in the dialysis tubing. The results showed that when the dialysis tubing was immersed in a solution that contained less salt, the pressure increased, and when it was immersed in a solution that contained more salt, the pressure decreased. Almost no change was recorded in the 0.9% solution. These findings suggest that salt concentration in the blood would impact the rate of osmosis, changing the pressure within the blood vessels.

A Tube Electrode High-speed Electrochemical Discharge Drilling Method without Recast Layer

The tube electrode high-speed electrochemical discharge drilling (TEECDD) is a hybrid process that combines electrical discharge high-speed drilling and electrochemical machining (ECM). By using a low conductivity salt solution as the working fluid, electrical discharge high-speed drilling takes place mainly in the frontal gap, and the recast layer at the side gap can be removed electrochemically at the same time. The machining voltage and current waveforms were recorded in the experiments. The tool wear performances were compared with pure electrical discharge machining (EDM). The results of removing the recast layer and the machining quality were analysed. Finally, a small hole can be fabricated with low tool wear and almost no recast layer by the hybrid process.

The importance of an efficient extraction protocol for the use of fish muscle cholinesterases as biomarkers

Esterase activity found in muscle extracts is useful to evaluate harmful effects of anticholinesterase pollutants. Yet, most procedures applied in the extraction of fish muscle esterases in order to investigate their activity as a biomarker of environmental exposure comprise the homogenization of muscle tissue in low-salt solutions, followed by centrifugation to separate the supernatant as the enzyme source. However, acetylcholinesterase (AChE), the main target in these monitoring efforts, is a membrane-bound protein and is only present in muscle extracts if homogenization is carried out using chaotropic high-salt solutions. In this context, four extraction procedures using muscle tissue from six fish species were evaluated in order to establish a reproducible and reliable AChE assay for the determination of this biomarker. Results indicate that over 80% of AChE activity might be lacking in low-salt supernatants, and that the highest activities are obtained after extraction with solutions containing either 1molL−1 NaCl or 1molL−1 NaCl plus 3% Triton X-100, preserving almost 100% esterase activity over acetylthiocholine as substrate after centrifugation. Thus, many studies in the literature suffer from theoretical flaws and report erroneous AChE activity, since typical muscle AChE activity, the end-point biomarker for anticholinesterase pollutants, may have not been consistently assayed.

Thirst Increases Chorda Tympani Responses to Sodium Chloride.

In nature, water is present as a low-salt solution, thus we hypothesized that thirst would increase taste responses to low-salt solutions. We investigated the effect of thirst on the 2 different salt detection mechanisms present in the rat chorda tympani (CT) nerve. The first mechanism is dependent upon the epithelial sodium channel (ENaC), is blocked by benzamil, and is specific to the cation sodium. The second mechanism, while undefined, is independent of ENaC, and detects multiple cations. We expected thirst to increase benzamil-sensitive sodium responses due to mechanistically increasing the benzamil-sensitive ENaC. We recorded CT whole-nerve electrophysiological responses to lingual application of NaCl, KCl (30, 75, 150, 300, 500, and 600 mM), and imitation rainwater in both control and 24-h water-restricted male rats. NaCl solutions were presented in artificial saliva before and after lingual application of 5µM benzamil. Water restriction significantly increased the integrated CT responses to NaCl but not to KCl or imitation rainwater. Consistent with our hypothesis, only the benzamil-sensitive, and not the benzamil-insensitive, CT sodium response significantly increased. Additionally, CT responses to salt were recorded following induction of either osmotic or volemic thirst. Both thirsts significantly enhanced the integrated CT responses to NaCl and KCl, but not imitation rainwater. Interestingly, osmotic and volemic thirsts increased CT responses by increasing both the benzamil-sensitive and benzamil-insensitive CT sodium responses. We propose that thirst increases the sensitivity of the CT nerve to sodium.

Elasticity at Swelling Equilibrium of Ultrasoft Polyelectrolyte Gels: Comparisons of Theory and Experiments

We have studied the elasticity of low volume fraction hyaluronic acid polyelectrolyte gels in swelling equilibrium as a function of salt concentration and strand length. By measuring the shear modulus at different salt concentrations for a constant volume fraction, and for different volume fractions at constant salt concentrations, we uniquely identify the physical parameters responsible for swelling, the chain hydrophobicity, χ, and the degree of ionization of the network, α, for our experimental conditions. Using these parameters, we predict the complex relationship between the elasticity of the network and the polymer volume fraction. The relationship is nonmonotonic due to the internal pressure of the system, and we predict that even in the equilibrium linear-elastic regime, polyelectrolyte gels stiffen as they swell in low salt solutions. For higher salt concentrations, the relationship is reversed, and the modulus increases with polymer volume fraction as expected. Using dynamic light scattering and...

Effect of Tumbling Marination on Marinade Uptake of Chicken Carcass and Parts Quality

ABSTRACT The objectives of this study were to evaluate the effect of marination on marinade uptake of chicken carcasses and to determine the meat quality of carcass parts. In total, 45 eviscerated chicken carcasses were divided into three marinating treatments: no marination, marination in water, marination in non-phosphate and low-salt solution (NPLS). The study showed that the marinade uptake of chicken carcasses was higher than 4.0% for NPLS marination and than 3.5% for water marination when compared with the non-marinated treatment. However, raw chicken meat yield after cut-up was not significantly different (p≥0.05) among treatments. Carcasses marinated in NPLS solution presented higher water-holding capacity (WHC). The results showed that NPLS marination may reduce cooking loss and expressible water of chicken meat after cooking. Based on the Warner-Bratzler Shear (WBSF) results, NPLS marination had a stronger effect on textural quality of cooked breast meat than thighs and drumsticks. However, no significant differences of texture profile analysis (TPA) parameters were observed (p≥0.05). In the sensory evaluation, NPLS marination influenced the sensory quality of cooked meat, particularly texture and appearance attributes, but not the taste and aftertaste attributes of cooked meat. It is concluded that NPLS marination effectively increased carcass weight, despite its effects on meat quality varied according to the anatomical location of the parts.

Technetium Leaching from Cementitious Materials

ABSTRACTAt the Savannah River Site (SRS) low activity salt solution is stabilized via encapsulation within a grout termed saltstone. Saltstone is emplaced into large (multi-million gallon) concrete storage facilities referred to as Saltstone Disposal Units (SDUs). Technetium-99 (99Tc) is a long-lived radionuclide contained in the low activity salt waste and subsequently incorporated into the grout waste form: it is considered a significant contributor to risk with respect to the long-term radiation exposure of the environment surrounding the SDUs. In the reducing, high pH environment within the grout,99Tc is expected to be relatively immobile since it exists in a reduced Tc(IV) oxidation state in the form of sparingly soluble sulfides (TcSx) or hydrated oxides (TcO2.xH2O). However, in the presence of O2(associated with the future infiltration of air or oxygenated ground waters into the saltstone monolith) it is possible for redox-sensitive Tc(IV) to transition into highly soluble (and mobile) Tc(VII) species, pertechnetate (TcO4-), which is more readily transported to the surrounding environment. Traditional approaches to quantifying the leaching behavior of99Tc from cementitious matrices have involved partitioning experiments using size-reduced (crushed/ground) saltstone samples, and determination of the99Tc fraction immobilized by the cementitious solids. Such experiments create artificially high solid-solution contact areas that likely result in higher99Tc leachate concentrations than would be expected for intact, monolithic samples. In the current study a new technique, termed the Dynamic Leaching Method (DLM), is being used to investigate the99Tc leaching behavior of monolithic saltstone samples. The data derived using this technique is intended to inform the SRS Saltstone Disposal Facility (SDF) Performance Assessment (PA) which models the long-term transport of radionuclides from the SDUs to the environment. The DLM utilizes a flexible-wall permeameter to achieve saturated leaching under an elevated hydraulic gradient in an effort to simulate the transport of groundwater through saltstone. Initial findings indicate that the99Tc concentrations in the leachate are on the order of 1E-08 mol/L which suggests that the saltstone leaching behavior is controlled by the solubility of TcO2.xH2O compounds.

Purification and cytotoxicity of glycoprotein isolated from Dendrobium huoshanense

Dendrobium huoshanense is a rare traditional Chinese medicinal herb, and the anti-tumor activity of its polysaccharides is a research hotspot in traditional Chinese medicine resources domain. This study aims to explore the material basis for the anti-tumor activity of polysaccharide. D. huoshanense was used as raw material in the experiment, and the different protein components were obtained through low salt solution extraction and ammonium sulfate fractional precipitation. Then glycoprotein components were determined by SDS-PAGE electrophoresis staining, and were further isolated and purified by DEAE ion column and Sephadex gel column. At the same time, MTT assay was used in detecting the cytotoxicity of different products on HepG2 cells in vitro. As a result, three kinds of glycoprotein components RG1, RG2, RG3 with relative molecular mass of 22.5, 19.8, 15.6 kDa were gained, and the IC₅₀ of three compounds on human liver cancer cell HepG2 was 534.23 mg•L⁻¹, meanwhile IC₅₀ of single glycoprotein component RG1, RG2 was 432.96, 413.91 mg•L⁻¹ respectively, and glycoprotein component RG3 had no cytotoxicity on HepG2 cells. All in all, the experiment results suggested that two kinds of glycoproteins components with relative molecular mass of 22.5, 19.8 kDa may be one of the material basis for anti-tumor activity of D. huoshanense polysaccharide, and they had a synergistic effect.

Early nucleation events in the polymerization of actin, probed by time-resolved small-angle x-ray scattering.

Nucleators generating new F-actin filaments play important roles in cell activities. Detailed information concerning the events involved in nucleation of actin alone in vitro is fundamental to understanding these processes, but such information has been hard to come by. We addressed the early process of salt-induced polymerization of actin using the time-resolved synchrotron small-angle X-ray scattering (SAXS). Actin molecules in low salt solution maintain a monomeric state by an electrostatic repulsive force between molecules. On mixing with salts, the repulsive force was rapidly screened, causing an immediate formation of many of non-polymerizable dimers. SAXS kinetic analysis revealed that tetramerization gives the highest energetic barrier to further polymerization, and the major nucleation is the formation of helical tetramers. Filaments start to grow rapidly with the formation of pentamers. These findings suggest an acceleration mechanism of actin assembly by a variety of nucleators in cells.

Study of ion-exchange properties of hydrated titanium dioxide towards cesium and strontium cations

Acid-base and sorption properties of spherically granulated material based on hydrated titanium dioxide were studied. It was shown that the sorption capacity of the ion exchanger is due both to the structure (cross-linking density of gels and, consequently, their porosity) and to the number of active acid centers. The kinetic specific features of the sorption of cations were considered and it was found that the sorption kinetics is limited by the intraparticle diffusion. It was shown that the sorbent can be used to purify low-salt technological solutions of liquid radioactive wastes.

Modified Mason number for charged paramagnetic colloidal suspensions.

The dynamics of magnetorheological fluids have typically been described by the Mason number, a governing parameter defined as the ratio between viscous and magnetic forces in the fluid. For most experimental suspensions of magnetic particles, surface forces, such as steric and electrostatic interactions, can significantly influence the dynamics. Here we propose a theory of a modified Mason number that accounts for surface forces and show that this modified Mason number is a function of interparticle distance. We demonstrate that this modified Mason number is accurate in describing the dynamics of a rotating pair of paramagnetic colloids of identical or mismatched sizes in either high or low salt solutions. The modified Mason number is confirmed to be pseudoconstant for particle pairs and particle chains undergoing a stable-metastable transition during rotation. The interparticle distance term can be calculated using theory or can be measured experimentally. This modified Mason number is more applicable to magnetorheological systems where surface forces are not negligible.