High Salt Solution Research Articles

Hydrophobic Interaction Chromatography: A Key Method for Protein Separation

This review's main goal is to increase theoretical knowledge and comprehension of the techniques used to separate important enzymes using chromatography. Protein separation, purification, and analysis frequently involve the use of hydrophobic interaction chromatography (HIC), in which the molecules are separated based on differences in hydrophobicity. It is conducted using a weakly hydrophobic, nonpolar stationary phase to which the proteins bind in an aqueous highsalt solution as the mobile phase. The protein integrity is thereby conserved during the process. HIC is usually used with a gradient from high to low concentrations of salt as an eluent and can be applied in a wide range of biotechnological processes. In this study, after a brief overview of hydrophobic interaction chromatography, we explain the HIC procedure, protein retention mechanism, factors affecting HIC, and applications of HIC.

Countercurrent Salting-out Homogenous Liquid-Liquid Extraction and Dispersive Liquid-Liquid Microextraction Based on the Solidification of Floating Organic Drop Followed by High-Performance Liquid Chromatography for the Isolation and Preconcentration of Pesticides from Fruit Samples.

Pesticides are widely used to control pests and prevent diseases in crops, including cereals, vegetables, and fruits. Due to factors such as the persistence of pesticides, bioaccumulation, and potential toxicity, pesticide residue monitoring in foodstuffs is very important. In the current research, we proposed a novel approach using countercurrent salting-out homogenous liquid-liquid extraction combined with dispersive liquid-liquid microextraction based on the solidification of floating organic droplets (DLLME-SFO) for isolation and preconcentration of pesticides from aqueous samples for analysis by high-performance liquid chromatography-ultraviolet detection (HPLC-UV). In brief, sodium chloride was used as a separation reagent, in a small glass column, through which was passed a mixture of an aqueous solution of, for example, fruit juice and acetonitrile. In this process, the droplets rose through the column and a separated layer would be formed on the remained an aqueous phase. Following that, acetonitrile as the organic phase was mixed with 50.0 µL of 1-undecanol (extraction solvent). To further enrich the analytes, the mixture was injected into 5 mL of a 4% w/v sodium chloride solution and placed in a tube for the DLLME-SFO. Under optimal conditions, a dynamic linear range of 0.5-500 μg/L, extraction recovery of 65-85%, enrichment factors of 108-142, and limit of detection of 0.2-0.4 μg/L were obtained for the organophosphorus pesticides analysed. In addition, the repeatability and reproducibility from five replicate measurements of the pesticides (100 μg/L) were within the ranges of 3.5-5.1% and 4.5-6.3%, respectively . In this research, a new extraction method based on countercurrent salting out homogeneous liquid-liquid extraction combined with DLLME-SFO has been applied for the determination of pesticide residues in fruits, juice and environmental samples before using HPLC-UV analysis. The combined method not only leads to high enrichment factors, but can also be used in complex matrices (such as fruits, juices and high-salt solutions) without pre-treatment or dilution. Compared with other sample preparation methods, this analysis procedure has many advantages, including simplicity, ease of operation, high pre-enrichment factor, low detection limit and relatively short analysis time. Combination of CCSHLLE and DLLME-SFO was applied for the analysis of organophosphorous pesticide residues in fruit, fruit juices and environmental samples. The DLLME-SFO method avoided using high density and toxic extraction solvents. LODs are achievable at ng L-1 using CCSLLE-DLLME-SFO-HPLC-UV.

A microfluidic study of oil displacement in porous media at elevated temperature and pressure

Microfluidics methods offer possibilities for visual observations of oil recovery processes. Good control over test parameters also provides the opportunity to conduct tests that simulate representative reservoir conditions. This paper presents a setup and procedure development for microfluidic oil recovery tests at elevated temperature and pressure. Oil recovery factors and displacement patterns were determined in single- or two-step recovery tests using two crude oils, high salinity salt solutions and low salinity surfactant solutions. Neither the displacement pattern nor the recovery factor was significantly affected by the pressure range tested here. Increasing temperature affected the recovery factor significantly, but with opposite trends for the two tested crude oils. The difference was justified by changes in wettability alteration, due to variations in the amounts and structure of the acidic and basic oil fractions. Low salinity surfactant solutions enhanced the oil recovery for both oils.

Insights into the free energy landscape and salt-controlled mechanism of the conformational conversions between human telomeric G-quadruplex structures

G-quadruplexes have become attractive drug targets in cancer therapy. However, due to the polymorphism of G-quadruplex structures, it is difficult to experimentally verify the relevant structures of multiple intermediates and transition states in dynamic equilibrium. Hence, understanding the mechanism by which structural conversions of G-quadruplexes occur is still challenging. We conducted targeted molecular dynamics simulation with umbrella sampling to investigate how salt affects the conformational conversion of human telomeric G-quadruplex. Our results explore a unique view into the structures and energy barrier of the intermediates and transition states in the interconversion process. The pathway of G-quadruplex conformational interconversion was mapped out by a free energy landscape, consisting of branched parallel pathways with multiple energy basins. We propose a salt-controlled mechanism that as the salt concentration increases, the conformational conversion mechanism switches from multi-pathway folding to sequential folding pathways. The hybrid-I and hybrid-II structures are intermediates in the basket-propeller transformation. In high-salt solutions, the conformational conversion upon K+ binding is more feasible than upon Na+ binding. The free energy barrier for conformational conversions ranges from 1.6 to 4.6 kcal/mol. Our work will be beneficial in developing anticancer agents.

Layer-by-layer self-assembly preparation and desalination performance of graphene oxide membrane

Abstract Unlike previous utilization of ultrafiltration membranes as supporters of graphene oxide (GO) composite membranes, this study first adopts microporous nylon membranes as substrates. The cationic polyelectrolyte/GO composite membranes are prepared by the layer-by-layer self-assembly method via electrostatic attraction. The introduction of polycations between nanochannels in the GO membranes effectively suppresses the swelling and improves the stability of the membranes. It is found that the polyelectrolytes' charge density and the surface potential of the composite membranes jointly determine the membranes' properties. The experimental results show that the novel GO membranes can obtain high flux and considerable desalination performance under low operating pressure. Typically, the salt rejection rate reaches 66.8% for 1.0 g/L MgSO4, and the flux is 39.8 L·m−2·h−1·bar−1. Benefitting from the GO composite membranes keeping similar retention for both high and low concentration salt solutions, the ideal desalination performance could be obtained through multi-stage processes on the premise of ensuring high flux, which is more suitable for industry.

Morphologies and Structure of Brain Lipid Membrane Dispersions.

This study aims to explore the variety of previously unknown morphologies that brain lipids form in aqueous solutions. We study how these structures are dependent on cholesterol content, salt solution composition, and temperature. For this purpose, dispersions of porcine sphingomyelin with varying amounts of cholesterol as well as dispersions of porcine brain lipid extracts were investigated. We used cryo-TEM to investigate the dispersions at high-salt solution content together with small-angle (SAXD) and wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) for dispersions in the corresponding salt solution at high lipid content. Sphingomyelin forms multilamellar vesicles in large excess of aqueous salt solution. These vesicles appear as double rippled bilayers in the images and as split Bragg peaks in SAXD together with a very distinct lamellar phase pattern. These features disappear with increasing temperature, and addition of cholesterol as the WAXD data shows that the peak corresponding to the chain crystallinity disappears. The dispersions of sphingomyelin at high cholesterol content form large vesicular type of structures with smooth bilayers. The repeat distance of the lamellar phase depends on temperature, salt solution composition, and slightly with cholesterol content. The brain lipid extracts form large multilamellar vesicles often attached to assemblies of higher electron density. We think that this is probably an example of supra self-assembly with a multiple-layered vesicle surrounding an interior cubic microphase. This is challenging to resolve. DSC shows the presence of different kinds of water bound to the lipid aggregates as a function of the lipid content. Comparison with the effect of lithium, sodium, and calcium salts on the structural parameters of the sphingomyelin and the morphologies of brain lipid extract morphologies demonstrate that lithium has remarkable effects also at low content.

Ultrasensitive colorimetric miRNA detection based on magnetic 3D DNA walker and unmodified AuNPs

Abstract Gold nanoparticles (AuNPs) based colorimetric assay is a promising platform for simple and low-cost point-of-care (POC) testing, but tends to have low sensitivity, which limits their clinical applications for trace nucleic acid assays. Herein, a simple colorimetric assay was developed by using unmodified AuNPs and magnetic 3D DNA walker, which could detect as few as 16.7 fM of miRNA-155, thus easily solves the main technical challenge of AuNPs-based colorimetric nucleic acid assays. In this platform, hundreds of substrate sing-stranded DNA (DNA tracks) and dozens of blocked walking strands were attached on an Au-Fe3O4 nanocomposite, applied as a magnetic 3D DNA walker. The target could activate this DNA walker powered by DNAzyme cleavage mechanism, generating a great deal of single-stranded product (displaced ssDNA). After magnetic separation, the generated displaced ssDNA (supernatant) was incubated with AuNPs to protect the unmodified nanoparticles from aggregation in high-salt solutions. Based on this, the concentration of miRNA-155 could be visualized through a color change from grayish black to purple and quantitatively determined by UV–vis spectroscopy. Furthermore, we demonstrated that our approach could be used to detect target miRNA-155 in real human serum samples without complicated sample pretreatment. Thus, the magnetic 3D DNA walker-AuNPs colorimetric method is a facile, sensitive and specific detection platform that shows great potential for development of next-generation POC nucleic acids diagnostics.

A novel smartphone-based colorimetric aptasensor for on-site detection of Escherichia coli O157:H7 in milk

Effective testing tools for Escherichia coli O157:H7 can prevent outbreaks of foodborne illness. In this paper, a smartphone-based colorimetric aptasensor was developed using functionalized gold nanoparticles (GNP) and multi-walled carbon nanotubes (MWCNT) for monitoring E. coli O157:H7 in milk. The maximum absorption peak of GNP bonded with aptamer (Apt) generated evident transformation from 518 to 524 nm. The excess GNP-Apt was removed by functionalized MWCNT magnetized with carbonyl iron powder (CIP) and hybridized with a DNA probe, whereas the GNP-Apt immobilized on E. coli O157:H7 remained in the system. In the presence of a high-salt solution, the GNP-Apt that captured E. coli O157:H7 remained red, but the free GNP-Apt aggregated and appeared blue. The chromogenic results were analyzed by a smartphone-based colorimetric device that was fabricated using acrylic plates, a light-emitting diode, and a mobile power pack. To our knowledge, this was the first attempt to use a smartphone-based colorimetric aptasensor employing the capture of GNP-Apt coupled with separation of MWCNT@CIP probe to detect E. coli O157:H7. The aptasensor exhibited good reproducibility and no cross-reaction for other bacteria. A concentration of 8.43 × 103 cfu/mL of E. coli O157:H7 could be tested in pure culture, and 5.24 × 102 cfu/mL of E. coli O157:H7 could be detected in artificially contaminated milk after 1 h of incubation. Therefore, the smartphone-based colorimetric aptasensor was an efficient tool for the detection of E. coli O157:H7 in milk.

Kaolin based protective barrier in municipal landfills against adverse chemo-mechanical loadings

In this work, we assess the self-sealing and swelling ability of the compacted granular bentonite (GB) under an inorganic salt environment and induced overburden stresses from the landfill waste. The laboratory permeation tests with high ionic strength salt solutions reveal that the GB fails to seal and exhibits a significant mechanical collapse under different applied stresses. The applicability of GB in the form of geosynthetic clay liners as the bottom liner facilities in landfills that produce high ionic strength salt leachates, therefore, remains a serious concern. We propose an additional barrier system based on kaolin, for the first time, to address this problem. The proposed kaolin-GB layered system performs satisfactorily in terms of its sealing and swelling ability even in adverse saline conditions and low overburden stresses. The kaolin improves the osmotic efficiency of the self and also helps the underlying GB layer to seal the inter-granular voids. The estimated design parameters by through-diffusion test suggest that the kaolin-GB layered system effectively attenuates the permeant flux and suitable as a landfill liner.

Highly transparent conductive ionohydrogel for all-climate wireless human-motion sensor

• A transparent conductive ionohydrogel was developed by employing hydrated [EMIM]Cl. • The hydrated [EMIM]Cl simultaneously provides free-ions and rich hydrogen bonds. • The ionohydrogel exhibits excellent water-retention and mechanical toughness. • All-climate ionohydrogel-based wireless sensing system was fabricated. Conductive hydrogels combined the electronic properties and soft nature of tissue-like materials can mimic the functions of human skin with mechanical and sensory properties and thus considered as one of the most promising platforms for fabricating human-motion sensors. However, the bottlenecks in inevitable water evaporation, low transparency and constraints on conductivity seriously hinder their practical application. The traditional strategies employing water-locking agent or high concentrated salt solutions are difficult to reconcile the paradox of ionic conductivity, mechanical and optical properties due to the phase separation. Herein, a novel ionohydrogel platform is prepared by employing hydrated ionic liquid as multifunctional solvent, which synchronously realize the high conductivity, transparency and wide temperature window. The multifunctional hydrated ionic liquids (HILs) ensure the ionohydrogel with high ionic conductivity (38.86 mS·cm −1 at 25 °C) and transparency (94.36% at 550 nm, 3 times of traditional hydrogels). Moreover, multiple hydrogen bonds formed by polymer chains, water and ionic liquid greatly improve the long-term stability (＞30 days) and broaden the working window (−40 °C to 80 °C). Furthermore, the wearable sensor device was fabricated through integrating ionohydrogel and silicon circuits to realize real-time motion monitoring with excellent durability (>5000 cycles) and high sensitivity ( GF = 6.78 at 800% strain). This work provides a promising and versatile method to construct the next generation of gel platform for strain sensors.

Proteoglycans contribute to the functional integrity of the glomerular endothelial cell surface layer and are regulated in diabetic kidney disease

All capillary endothelia, including those of the glomeruli, have a luminal cell surface layer (ESL) consisting of glycoproteins, glycolipids, proteoglycans (PGs) and glycosaminoglycans. Previous results have demonstrated that an intact ESL is necessary for a normal filtration barrier and damage to the ESL coupled to proteinuria is seen for example in diabetic kidney disease (DKD). We used the principles of ion exchange chromatography in vivo to elute the highly negatively charged components of the ESL with a 1 M NaCl solution in rats. Ultrastructural morphology and renal function were analyzed and 17 PGs and hyaluronan were identified in the ESL. The high salt solution reduced the glomerular ESL thickness, led to albuminuria and reduced GFR. To assess the relevance of ESL in renal disease the expression of PGs in glomeruli from DKD patients in a next generation sequencing cohort was investigated. We found that seven of the homologues of the PGs identified in the ESL from rats were differently regulated in patients with DKD compared to healthy subjects. The results show that proteoglycans and glycosaminoglycans are essential components of the ESL, maintaining the permselective properties of the glomerular barrier and thus preventing proteinuria.

Terminal Sequence-Specific Interparticle Attraction between DNA Duplex-Carrying Polystyrene Microparticles in Aqueous Salt Solution Assessed by Optical Tweezers.

The dispersion behavior of DNA duplex-carrying colloidal particles in aqueous high-salt solutions shows extraordinary selectivity against the duplex terminal sequence. We investigated the interparticle force between DNA duplex-carrying polystyrene (dsDNA-PS) microparticles in aqueous salt solutions and examined their behavior in relation to the duplex terminal sequences. Force-distance (F-D) curves for a pair of dsDNA-PS particles were recorded with a dual-beam optical tweezers system with the two optically trapped particles closely approaching each other. Interestingly, only 3-5% of the oligo-DNA strands on the dsDNA-PS particles formed a duplex with complementary DNAs, and the F-D curves showed a distinct specificity to the duplex terminal sequences in the interparticle force at a high-NaCl concentration; a clear attraction peak was observed in F-D curves only when the duplex terminal was a complementary base pair. The attractive strength reached 2.6 ± 0.5 pN at 500 mM NaCl and 4.3 ± 1.0 pN at 750 mM NaCl. By sharp contrast, no significant attraction occurred for the particles with mismatched duplex terminals even at 750 mM NaCl. Similar duplex terminal-specificity in the interparticle force was also confirmed for dsDNA-PS particles in divalent MgCl2 solutions. Considering that the duplex terminal sequences on the dsDNA-PS particles showed only a negligible difference in their surface charges under identical salt conditions, we concluded that the interparticle attraction observed only for the dsDNA-PS particles with complementary duplex terminals is attributable to the salt-facilitated stacking interaction between the paired terminal nucleobases (i.e., blunt-end stacking) on the dsDNA-PS surfaces. Our results thus demonstrate the occurrence of a duplex terminal-specific interparticle force between dsDNA-PS particles under high-salt conditions.

Wettable copper hydroxide cotton fabric for oil-water separation made by surface micro-dissolution

Cotton textiles with special surface wettability, high adsorption capacity and low cost have a promising future for oily wastewater purification. A facile and efficient surface microdissolution technology was used to generate micro-nanostructure copper hydroxide on the surface of cotton fabric, and super-hydrophilic and underwater superoleophobic functional textiles were prepared. The underwater contact angle of the developed Cu(OH)2@Cotton Fabric is more than 152.9°. Driven by gravity, the oil/water mixture can be successfully separated by CH@CF with high flux of 2043–3843 L/m2h and high separation efficiency of 98.75%. After soaking in the harsh environment (high alkali and salt solution) for 24 h, CH@CF still keep good oil-water separation ability. The prepared fabric is efficient in the separation of water-in-oil emulsion driven by a constant current pump (200 mL/min) and the efficiency is greater than 99.1%. After repeated separation experiments for 25 times, the separation efficiency of the CH@CF for oil-water mixture keep more than 98.93%. This method can produce fabrics made of low-cost and available materials, expected to be a potential and feasible and efficient solution for oily wastewater purification, which has a promising future for oil/water separation.

Charged Poly(N-isopropylacrylamide) Nanogels for the Stabilization of High Isoelectric Point Proteins.

Storage and transportation of protein therapeutics using refrigeration is a costly process; a reliable electrical supply is vital, expensive equipment is needed, and unique transportation is required. Reducing the reliance on the cold chain would enable low-cost transportation and storage of biologics, ultimately improving accessibility of this class of therapeutics to patients in remote locations. Herein, we report on the synthesis of charged poly(N-isopropylacrylamide) nanogels that efficiently adsorb a range of different proteins of varying isoelectric points and molecular weights (e.g., adsorption capacity (Q) = 4.7 ± 0.2 mg/mg at 6 mg/mL initial IgG concentration), provide protection from external environmental factors (i.e., temperature), and subsequently release the proteins in an efficient manner (e.g., 100 ± 1% at 2 mg/mL initial IgG concentration). Both cationic and anionic nanogels were synthesized and selectively chosen based on the ability to form electrostatic interactions with adsorbed proteins (e.g., cationic nanogels adsorb low isoelectric point proteins whereas anionic nanogels adsorb high isoelectric point proteins). The nanogel-protein complex formed upon adsorption increases the stabilization of the protein's tertiary structure, providing protection against denaturation at elevated temperatures (e.g., 84 ± 4% of the protected IgG was stabilized when exposed to 65 °C). The addition of a high molar salt solution (e.g., 40 mM CaCl2 solution) to protein-laden nanogels disrupts the electrostatic interactions and collapses the nanogel, ultimately releasing the protein. The versatile materials utilized, in addition to the protein loading and release mechanisms described, provide a simple and efficient strategy to protect fragile biologics for their transport to remote areas without necessitating costly storage equipment.

METAL ORGANIC FRAMEWORKS LOADED POLYMERIC MEMBRANES IN PERVAPORATIVE DESALINATION APPLICATIONS: A MINI REVIEW

Pervaporative desalination is an efficacious method to obtain fresh water from saline water sources. High salt rejection and capacity to cope with high-salt concentration water solutions are important advantages of pervaporation process. To improve pervaporative desalination performance, researches concentrate on novel membrane types. Water stable metal organic frameworks loaded membranes attract substantial attention among novelty membrane applications. This study focuses on pervaporative desalination with MOF loaded polymeric membrane. First of all, the features of MOFs, synthesis methods, usage areas are explained. Then, MOFs loaded mixed matrix membranes, production methods, used MOF types in membranes and applications in pervaporative desalination are examined. At the end of the study, future expectation on the desalination applications of MOF loaded membranes are presented as concluding remarks. Metal organic framework loaded polymeric membranes are seen as promising candidates to obtain drinking water with high separation yield in pervaporative desalination process.

Results accuracy of the simultaneous Na, K, Li, Rb and Cs determination in geochemical objects using the flame atomic emission spectrometry

One of the most important challenges in the simultaneous determination of the five alkaline elements is that their abundance differs thousands of times in natural samples. Therefore, usually the analysis of the same samples is performed using several analytical methods or techniques. An atomic emission spectrometry is the most selective method for the determination of alkaline elements in wide ranges of their contents. The reliable and correct simultaneous determination of major and trace elements contents by one method is economically attractive for classifying rocks, reconstructing the conditions of their formation, etc. The atomic emission spectrometry technique of the simultaneous determination of the five alkaline elements was developed with the use of the modern equipment. The accuracy and trueness of the developed technique results were evaluated in the current study. The technique features were the preparation and the analysis of the high-salt solutions of the geochemical samples, and the use of a low-temperature propane-butane flame and multichannel photoelectric recording of the spectra for the simultaneous determination of alkali metals contents. A specific data processing ensured accounting for the spectral background and minimizing the interferences when calibrating by CRMs with various compositions and genesis. The determined concentrations ranges of alkaline elements in natural and man-made environments had been expanded by improving the detection limits and using several analytical lines of Na, K and Rb with different spectral features. FAES results were compared with the results of XRF, ICP-MS, the standard addition and dilution methods, and its accuracy and trueness were found to be satisfactory for the requirements of geological and geochemical studies.

Анализ современных методов переработки кубовых остатков атомных электрических станций

To date, more than 600 thousand m3 of liquid radioactive waste has been accumulated at Russian nuclear power plants (NPPs). In addition to radioactive components, they contain a large amount of mineral salts, organic matter, oil products, and suspensions. The problem of overfilling the storage facilities for liquid waste at some NPPs is critical and has to be solved urgently. The article presents modern methods for processing vat residues and the existing prerequisites for modernizing ion-selective purification plants, which are based on the results of research works carried out by various teams. A technological analysis of the methods for evaporation and ion-selective purification of vat residues with identified shortcomings of individual stages of the technologies is carried out. Decontamination of secondary products of liquid radioactive waste processing implies the possibility of subsequently separating valuable components for reusing them. Their decontamination is necessary, since these wastes are essentially high-salt solutions with a specific activity of 106-107 Bq/l contaminated with fission products, radionuclides of corrosion origin, and various substances used to decontaminate the equipment and maintain the water chemistry. It is proposed to apply the electrodialysis method for separating a multicomponent solution of the decontaminated NPP vat residue and to use the obtained products at the plant. Owing to the partial extraction of valuable components from decontaminated vat residues, it becomes possible to reduce the amount of waste and return the separated substances into the main process cycle, thereby reducing the expenditures for initial reagents. To implement the developed technology for component-wise separation of the initial solution, a laboratory electrodialysis facility was manufactured. The project implementation feature was that in dealing with boric acid salts, it is necessary to take into account the danger of their precipitation at certain pH values. It was found that to minimize the escape of boric components, the process should be conducted at low pH values, i.e., the solution should be acidified with the nitric acid obtained in the process. The obtained study results can be used to modernize the cementation plants.

Metal Organic Frame-Upconverting Nanoparticle Assemblies for the FRET Based Sensor Detection of Bisphenol A in High-Salt Foods.

To resolve the occurrence of unfulfillable detection in high-salts foods, we used fluorescence resonant energy transfer (FRET) sensors based on nanoparticle upconversion. In this study, we developed a novel FRET sensor for the detection of bisphenol A (BPA) in high-salt foods. We based this approach on the assembly of aptamer modified upconversion nanoparticles (DNA1-UCNPs) and complementary DNA modified metal organic frames (DNA2-MOFs), which possessed corresponding wavelength absorption. Targeting BPA signal transduction was performed using the BPA aptamer, via competitive recognition between the BPA analyte and complementary DNA sequences in a high-salt solution. Sensor adaption in high-salt samples was attributed to functional hydrophilic groups, modified in the MOFs, and the enhanced colloidal stability of these MOFs. The MOF-UCNP assembly displayed considerable analytical performance in terms of BPA detection, with a linear range of 0.1–100 nM, and a limit of detection (LOD) of 0.02 nM, in a 340 mM NaCl food sample (the energy drink, Gatorade). Thus, this method provides a solid basis for small molecules detection in high-salt foods.

Effect of NaCl concentration on the dispersion, stability and rheological properties of MWNTs by CMC

A detailed study of the dispersion, rheological and adsorption behaviors between multi-walled carbon nanotubes (MWNTs) and sodium carboxymethylcellulose (CMC) at different NaCl concentration were presented. The experimental results suggested that NaCl concentration governed the dispersion and stability of MWNTs. A small amount of NaCl was contributed to the dispersion and stability of MWNTs, while as the NaCl concentration increased, the MWNTs formed aggregates and the MWNTs suspension became unstable. Adsorption amount, Raman spectroscopy, zeta potential, and adsorption conformation were investigated systematically to elucidate the mechanism of this interesting phenomenon. Surprisingly, results from thermogravimetric analysis (TGA) shown that adsorption amount of CMC on MWNTs didn’t change under any circumstances. The value of zeta potential increased slightly at first and then dropped sharply as the increasing of NaCl concentration. The microstructures were measured by TEM. It was found that uniform CMC adsorption layers were formed on the surface of MWNTs at low NaCl concentrations. However, for the high-salt solution, the MWNTs were wrapped by CMC agglomerates, resulting in poor dispersion stability.

Na+ Efflux from Apple Dwarfing Rootstocks is Associated with High-Salt Resistance of Their Scions

In apple (Malus) cultivation, the adaptability of rootstocks has a fundamental influence on multiple abiotic-stress resistance properties of their scions. Here, we investigated the high-salt resistance of apple rootstocks, by treating 2-year-old apple trees consisting of the ‘Fuji’ cultivar grafted onto three different dwarfing rootstocks (SH6, M9-T337 and G935) with a high-salt solution for 30 days. We found that the high-salt stress caused leaf yellowing and growth inhibition to all apple plants, and that the most serious reduction in relative chlorophyll content, plant height and biomass accumulation was associated with the SH6 rootstock. In addition, based on the salt injury index, the high-salt resistance of the ‘Fuji’ scion on the three dwarfing rootstocks was ranked as G935 > M9-T337 > SH6. In addition, analysis of mineral elemental composition showed that the Na+ content in ‘Fuji’ leaves on the G935 rootstock increased less than twofold compared to the control, whereas those on the SH6 rootstock increased nearly 20-fold, accompanied with reduced K and Fe element absorption under high-salt treatments. Expression analysis of nine Na+ transport-related genes indicated that in the salt overly sensitive (SOS) pathway, the SOS1, SOS2 and SOS3 genes showed considerably greater induction by high-salt stress in G935 roots than in SH6 roots. Given the Na+ content detected in roots of different rootstocks, we propose that more efficient Na+ extracellular efflux in G935 roots, rather than intracellular Na+ compartmentalization, contributed to the improved characteristics of the G935 rootstock under high-salt conditions.