Presence Of Inorganic Salts Research Articles

Experimental and Modeling Study on Methane Hydrate Equilibrium Conditions in the Presence of Inorganic Salts.

The aim of this study was to determine the influence of four inorganic salts, KCl, NaCl, KBr and NaBr, on the thermodynamic conditions of methane hydrate formation. In order to achieve this, the vapor-liquid water-hydrate (VLWH) equilibrium conditions of methane (CH4) hydrate were measured in the temperature range of 274.15 K-282.15 K by the isothermal pressure search method. The results demonstrated that, in comparison with deionized water, the four inorganic salts exhibited a significant thermodynamic inhibition on CH4 hydrate. Furthermore, the inhibitory effect of Na+ on methane hydrate is more pronounced than that of K+, where there is no discernible difference between Cl- and Br-. The dissociation enthalpy (∆Hdiss) of CH4 hydrate in the four inorganic salt solutions is comparable to that of deionized water, indicating that the inorganic salt does not participate in the formation of hydrate crystals. The Chen-Guo hydrate model and N-NRTL-NRF activity model were employed to forecast the equilibrium conditions of CH4 hydrate in electrolyte solution. The absolute relative deviation (AARD) between the predicted and experimental values were 1.24%, 1.08%, 1.18% and 1.21%, respectively. The model demonstrated satisfactory universality and accuracy. This study presents a novel approach to elucidating the mechanism and model prediction of inorganic salt inhibition of hydrate.

Platinum-modified bismuth molybdate flake balls as visible-light-responsive photocatalyst

Solar photocatalysis is considered as one of the best methods for “green” purification of environment. Accordingly, efficient, stable, and low-price materials must be developed for possible commercial application. Herein, flower-like bismuth molybdate (Bi2MoO6) photocatalysts were successfully synthesized by CTAB-assisted hydrothermal process, and then surface modified with platinum by photodeposition. The obtained materials were characterized by various methods, including XRD, DRS, XPS, SEM, TEM, ESR, photoluminescence spectroscopy and photoelectrochemical tests. Photocatalytic activity was tested mainly for tetracycline (TC) antibiotic degradation under visible-light irradiation (λ > 420 nm), including scavenger tests and experiments for different operation conditions (TC concentration, photocatalyst dose, pH value, in the presence of inorganic salts, water taken from different reservoirs). It has been found that the best photocatalyst containing 0.5 wt% of platinum exhibits 94.2 % TC removal during 60-min visible-light irradiation, reaching the reaction rate constant of 0.0392 min−1 (exceeding the data reported up to now). It is proposed that exceptional photocatalytic performance is caused by the synergy between the uniform flower structure (efficient light harvesting and large specific surface area) and double function of platinum deposits, i.e., as a sink for electrons (hindering charge carriers’ recombination) and a plasmonic sensitizer (allowing energy transfer from excited platinum to oxygen). Superoxide radicals (•O2−) are the main oxidation species, as proven by the quenching experiments and EPR analysis. However, in the case of platinum-modified samples, singlet oxygen plays also an important role, and thus an energy transfer from plasmonic platinum to oxygen could be expected. Additionally, TC degradation pathways, elucidated by the detection of intermediates, and the toxicity data (TC and its degradation products), assessed by a quantitative structure–activity relationship (QSAR) method, have confirmed that photocatalytic degradation of TC is indeed an environmental-friendly method, highly recommended for the decomposition of persistent organic compounds.

Influences of carboxymethyl chitosan upon stabilization and gelation of O/W Pickering emulsions in the presence of inorganic salts

The objective of this study was to investigate the effects of carboxymethyl chitosan (CMCS) on the stabilization and gelation of oil-in-water (O/W) Pickering emulsions (PEs) with polyphenol-amino acid particles in the presence of inorganic salts. The results revealed that the CMCS-induced depletion interactions contributed to improving the emulsification ability and interfacial adsorption efficiency of polyphenol-amino acid particles as well as constructing the network structures in the continuous phase. These relevant changes collectively resulted in elevating stability, viscosity and moduli of PEs. The additional effects of different inorganic salts with varying additions were further investigated, and the addition-dependent phenomena were observed. At low additions of inorganic salts, the occurrence of the chelation of inorganic salts with CMCS consolidated the constructed network structure, favorable to the gelation of PEs. With increasing additions, this chelation effect became stronger which compromised the CMCS-induced depletion, gradually leading to destabilization of PEs. In terms of ion species, the more pronounced effect on emulsion stability was achieved with calcium ions than with potassium and iron ions. This study expects to provide a new perspective on the extending application of cationic CMCS for improving the stability of O/W PEs in the food industry.

Surfactant foamulsion stability in the absence and presence of salt

Foamulsions are widely used in many fields but the stability of them is still not fully understood. We investigate the evolution of foamulsions in the absence and presence of inorganic salt. For the system without salt, it is found that the effect of oil on the foamulsion properties depends on the critical threshold concentration of surfactant (300 mM), below which the foamulsion aging is slowed down and above it its evolution is facilitated. When salt is added, the surfactant molecules precipitates to form crystals, foamulsions tend to be generated in regions where the surfactant concentration is not less than the salt concentration, but it is difficult to foam at salt concentrations higher than 200 mM, independent of the oil concentration, unless the surfactant concentration is very high. For the prepared stable foamulsions, the stabilization mechanism is due to the inhibition of coarsening and coalescence of bubbles and oil droplets by the adsorption of surfactant molecules and crystal particles onto their surfaces. The investigation of adsorption kinetics show that maybe the crystals move to the surface of bubbles is faster than oil droplets. The system consisting of surfactant, oil, salt and water is simple and temperature sensitivity, which could have many potential applications.

Effect of MgCl2 on CO2 sequestration as hydrates in marine environment: A thermodynamic and kinetic investigation with morphology insights

Oceanic hydrate-based CO2 sequestration (HBCS) holds great promise for achieving carbon neutrality. However, the presence of inorganic salts, particularly MgCl2 besides NaCl, in seawater can significantly impact the formation rate and the stability of CO2 hydrate. In this study, experimental investigations were conducted to examine the thermodynamics, kinetics, and the resulting morphological features of CO2 hydrate in the presence of MgCl2, covering mass fractions ranging from 0 to 5.0 wt%. The experimental findings reveal that MgCl2 exerts a thermodynamic inhibitory effect with its inhibitory capacity increasing with higher mass fractions. The solubility model of CO2 in MgCl2 solution was modified, demonstrating a gradual weakening of CO2 solubility as MgCl2 mass fraction increases. Additionally, the growth kinetics of CO2 hydrate decreases with increasing MgCl2 mass fraction. Regarding CO2 hydrate morphology, it was observed that at low mass fractions of MgCl2 (<1.0 wt%), a dense hydrate film rapidly formed at the gas-liquid interface after CO2 hydrate nucleation, hindering the further conversion of CO2 into hydrate. Conversely, at higher mass fractions (>3.0 wt%), CO2 hydrate exhibits a more porous and slurry-like structure, facilitating more gas-liquid contact and mass transfer, thereby enhancing the conversion of CO2 into hydrate. During hydrate dissociation, a salt-removal effect associated with CO2 hydrate formation was observed, leading to the accumulation of concentrated electrolyte (MgCl2) and facilitating CO2 hydrate dissociation. These findings have implications for understanding the CO2 hydrate formation and dissociation in the presence of MgCl2 relevant in the subsea environment and can contribute to the development of effective hydrate-based CO2 sequestration strategies.

REMOVAL OF CA2+ AND MG2+ FROM PRODUCED WATER USING SERIGUELA RESIDUE (SPONDIAS PURPUREA L.) AS POTENTIAL BIOSORBENT

Produced Water (PW) represents a problematic residue for the petroleum industry because it is generated in high amounts and it presents varied chemical composition can be toxic to organisms. The presence of inorganic salts, as calcium and magnesium, classify the PW in terms of its total hardness (TH) and this characteristic is an indication of the capacity to scale formation in pipelines and equipment. Thus, the adsorption treatment has been highlighted as an alternative method, mainly due to its low cost, high selectivity, and application of biodegradable adsorbents. In this context, the objective of this work is to evaluate the removal of Ca2+ and Mg2+ from PW using seriguela seeds (SS) as potential biosorbent. This work characterizes SS by chemical composition, surface groups, PZC (PZC) and SEM. The adsorption tests in batch resulted in levels of efficiency and TH adsorption capacity of 25 % and 8 mg g-1.

A sustainable and fast methodology based on magnetic activated carbon for removal of imidacloprid from aqueous solution

The occurrence of neonicotinoid insecticides in environmental waters represents a potential risk for the ecosystems and human health. Herein, an efficient procedure based on an activated carbon/magnetite (AC/Fe3O4) mixture adsorbent is proposed for fast removal of imidacloprid (IMI) as target molecule. The effects of contact time, adsorbent dosage and presence of inorganic salts on the adsorption characteristics of IMI on AC/Fe3O4 were evaluated by using a simple flow-system. Under optimal conditions, IMI was satisfactorily removed in only 10 min using AC/Fe3O4 (90:10 mass:mass ratio) at pH 7.0. The adsorption capacity was 192 mg g−1 at 25 °C. IMI only adsorbed on AC, but Fe3O4 was necessary to impart magnetic properties to AC. A comparative analysis of adsorption isotherms of several carbon-based adsorbents for IMI demonstrates that not only the maximum adsorption capacity of the adsorbent but also the affinity of the surface for the insecticide (given by the adsorption constant) needs to be considered when choosing an adsorbent. Materials with high maximum adsorption capacities are good for concentrated solutions, such as wastewaters; materials with high adsorption constants are especially good for more dilute solutions, such as environmental samples. Desorption of IMI was also tested under different pH conditions and effective desorption was achieved at pH 11.5 (25 °C), allowing the reuse of the material for subsequent adsorption runs without losing its capacity. Thus, an efficient, sustainable and low-cost adsorption procedure is proposed for fast removal of IMI from aqueous solution. These results demonstrate the potential applications of the studied mixture as adsorbent for developing alternative water cleaning technologies and analytical systems.

Effect of Additives on Decomposition of Methyl Orange and Congo Red Dyes Found in Industrial Wastewater

A number of textile industries are using different types of dyes which can be a threat to the environment when they are directly exposed without any treatment. The advanced oxidation process (AOP) has become one of the popular methods in which the dye molecules are degraded using microwave irradiation. This method has become popular due to its eco-friendly and cost-efficient characteristics. In this article, the author has reported the degradation of two azo dyes, named methyl orange (MO) and congo red (CR), in the presence of inorganic salts, some additives like charcoal, H2O2, CCl4, tert-butyl alcohol (TBA), glucose and sucrose. A comparative study was conducted to find out the relative degradation rate enhanced by various additives. For both of the dyes, it was found that charcoal was the most effective additive and significantly enhanced the degradation rate mainly due to its high adsorption capability. TBA was found to be the least enhancer. The order of effectiveness based on the irradiation period for MO was 0.01g charcoal &gt; 20 ml NaCl &gt; 20 ml Na2SO4 &gt; 20ml glucose&gt; 10 ml sucrose &gt; 100 μL CCl4 &gt; 200 μL H2O2 &gt; pure MO &gt; TBA. On the other hand, the order of effectiveness for CR for the same condition of irradiation was Combined additives&gt;0.01g charcoal &gt; TBA &gt; 100 μL CCl4&gt; pure CR.

Electrophilically Trapping Water for Preventing Polymerization of Cyclic Ether Towards Low-Temperature Li Metal Battery.

Cyclic ether, such as 1,3-dioxolane (DOL), are promising solvent for low-temperature electrolytes because of the low freezing point. Their use in electrolytes, however, is severely limited since it easily polymerizes in the presence of lithium inorganic salts. The trace water plays a key role via providing the source (proton) for chain initiation, which has, unfortunately, been neglected in most cases. In this work, we present an electrophile, trimethylsilyl isocyanate (Si-NCO), as the water scavenger, which eliminates moisture by a nucleophilic addition reaction. Si-NCO allows DOL to maintain liquid over a wide temperature range even in high-concentration electrolyte. Electrolyte with Si-NCO additive shows promising low-temperature performance. Our finding expands the use of cyclic ether solvents in the presence of inorganic salts and highlights a large space for unexplored design of water scavenger with electrophilic feature for low-temperature electrolytes.

Electrophilically Trapping Water for Preventing Polymerization of Cyclic Ether Towards Low‐Temperature Li Metal Battery

AbstractCyclic ether, such as 1,3‐dioxolane (DOL), are promising solvent for low‐temperature electrolytes because of the low freezing point. Their use in electrolytes, however, is severely limited since it easily polymerizes in the presence of lithium inorganic salts. The trace water plays a key role via providing the source (proton) for chain initiation, which has, unfortunately, been neglected in most cases. In this work, we present an electrophile, trimethylsilyl isocyanate (Si−NCO), as the water scavenger, which eliminates moisture by a nucleophilic addition reaction. Si−NCO allows DOL to maintain liquid over a wide temperature range even in high‐concentration electrolyte. Electrolyte with Si−NCO additive shows promising low‐temperature performance. Our finding expands the use of cyclic ether solvents in the presence of inorganic salts and highlights a large space for unexplored design of water scavenger with electrophilic feature for low‐temperature electrolytes.

Preparation of nano zero-valent aluminum for one-step removal of methylene blue from aqueous solutions: cost analysis for scaling-up and artificial intelligence

Methylene blue (MB) is a heterocyclic aromatic dye that is difficult to biodegrade due to its complex chemical structure. In this study, chemically prepared nano zero-valent aluminum (nZVAl) was investigated for the first time for one-step removal of MB from aqueous solutions under different experimental factors (pH, dosage, time, MB concentration, stirring rate, temperature, detergents, and ionic strength). The prepared nZVAl material was characterized using XRD, TEM, SEM, EDS, and FTIR. Results indicated that at an initial MB concentration of 10 mg/L, pH 10, nZVAl dosage 1.0 g/L, stirring rate 200 rpm, and temperature 30 °C, the removal efficiency of approximately 99.0% was achieved within an equilibrium time of 90 min. An improvement in MB removal efficiency was observed in the presence of inorganic salts, while the presence of detergents resulted in a reduction in MB removal efficiency. The isotherm adsorption data were best fitted by the Freundlich isotherm model (R2: 0.9569), while the kinetic data were well described by the pseudo-second-order (PSO) model (R2: 0.9999). Based on the thermodynamic study, the MB adsorption process is physically diffusion-controlled. The adsorption of MB onto nZVAl was accurately described using an artificial neural network (ANN) with a structure of 11–10–1 and R2 of 0.97. The overall cost of scaling up the adsorption unit to be used for MB removal from aqueous solutions under the optimum conditions is about US$1.31/m3. Consequently, this study opens the door for other researchers to test nZVAl in treating real textile wastewater.

Effect of salt on the adsorption of ionic surfactants at the air-water interface

• NaCl has significant effect on the equilibrium and dynamic surface tension of ionic surfactant solutions. • The SRT model predicts the adsorption dynamics more accurately than the DKC model. • Salt bridging leads to the compact packing of ionic surfactant at the air-water interface. The combined effect of ionic surfactants and inorganic salts on the interfacial properties is of great importance to various industrial processes. In this work, the effect of ionic surfactants (SDS and CTAB), in the presence of inorganic salt (NaCl), on the surface tension is systematically investigated using experiments, theoretical models, and all-atom molecular dynamics simulations. The equilibrium and dynamic surface tension of surfactant-salt-water systems in a salinity range of 0.01–0.1 M are measured using the pendant drop method. The theoretical models viz., statistical rate theory and diffusion kinetic controlled, suggest that adsorption drives the migration of surfactant molecules to the interface. Finally, the molecular dynamics simulations illustrate increased surfactant packing at the air-liquid interface in the presence of salt due to counterions bridging between the surfactant molecules, which results in a lower value of surface tension for both the surfactants.

Inorganic Salt Catalysed Hydrothermal Carbonisation (HTC) of Cellulose

The presence of inorganic salts either as part of the substrate or added to the reaction medium are known to significantly affect the reaction pathways during hydrothermal carbonisation (HTC) of biomass. This work aims to understand the influence of salts on hydrothermal carbonisation by processing cellulose in the presence of one or more inorganic salts with different valency. Batch experiments and Differential Scanning Calorimetry were used to investigate the change in reaction pathways during hydrothermal conversion. The effect of salts on the rate of HTC of cellulose can be correlated with the Lewis acidity of the cation and the basicity of the anion. The effect of the anion was more pH-dependent than the cation because it can protonate during the HTC process as organic acids are produced. The introduction of salts with Lewis acidity increases the concentration of low molecular weight compounds in the process water. The addition of a second salt can influence the catalytic effect of the first salt resulting in greater levulinic acid yields at the expense of hydrochar formation. Salts also play an important role in cellulose dissolution and can be used to modify the yield and composition of the hydrochars.

Assembly of recombinant tau into filaments identical to those of Alzheimer's disease and chronic traumatic encephalopathy.

Abundant filamentous inclusions of tau are characteristic of more than 20 neurodegenerative diseases that are collectively termed tauopathies. Electron cryo-microscopy (cryo-EM) structures of tau amyloid filaments from human brain revealed that distinct tau folds characterise many different diseases. A lack of laboratory-based model systems to generate these structures has hampered efforts to uncover the molecular mechanisms that underlie tauopathies. Here, we report in vitro assembly conditions with recombinant tau that replicate the structures of filaments from both Alzheimer's disease (AD) and chronic traumatic encephalopathy (CTE), as determined by cryo-EM. Our results suggest that post-translational modifications of tau modulate filament assembly, and that previously observed additional densities in AD and CTE filaments may arise from the presence of inorganic salts, like phosphates and sodium chloride. In vitro assembly of tau into disease-relevant filaments will facilitate studies to determine their roles in different diseases, as well as the development of compounds that specifically bind to these structures or prevent their formation.

Characterization of a surfactant-stable α-amylase produced by solid-state fermentation of cassava (Manihot esculenta Crantz) tubers using Rhizopus oligosporus: Kinetics, thermal inactivation thermodynamics and potential application in laundry industries

α-Amylase is a foremost hydrolytic enzyme used for various industrial processes. In the present study, Rhizopus oligosporus α-amylase (ROAA) produced during solid state fermentation of cassava ( Manihot esculenta ) tubers by the fungus was partially purified and biochemically characterized. The kinetic and thermal inactivation thermodynamics properties of the partially purified enzyme were also evaluated as well as the potential application in cloth washing. The ROAA was purified by 4.11-fold and had a molecular weight of 60 kDa. ROAA was optimally active at 60 °C, pH 5.0 and had a salt tolerance of 1–100 mM NaCl for 120 min. The activity of the α-amylase was significantly (p < 0.05) increased in the presence of various inorganic salts especially at 10 mM. Ethylenediaminetetraacetic acid (EDTA), urea and thiourea enhanced ROAA activity. Triton X-100 enhanced ROAA activity by 141.97%, whereas sodium dodecyl sulphate (SDS) decreased it by 28.58%. Tween 20 and Tween 80 did not significantly affect ROAA activity at 1 mM. V max , K m and K cat of ROAA were 37.59 U/mg protein, 16.39 mg/mL and 0.016 s −1 , respectively. Thermal stability indicators such as half-life, D-value at 70 °C and Z-value were 101.91 min, 338.70 min, and 48.78 °C, respectively. Cloth washing efficiency of a mixture of the isolated enzyme and commercial detergents was high relative to detergent-only trial. The enzyme had high thermal stability, optimized activity in the presence of some inorganic salts, and resistance to several surfactants and a chelating agent. The fungal α-amylase reported in this study would find relevance not only in starch-based industries but also in laundry. • R. oligosporus secreted α-amylase during the SSF of cassava tubers. • The α-amylase was optimally active at 60 °C and pH 5, activated by EDTA. • Thermal inactivation thermodynamics followed first order kinetics. • The α-amylase (ROAA) produced was moderately thermally stable (D-value, Z-value). • ROAA showed resistance to the inhibitory action of some surfactants.

Assessing the hydrotropic effect in the presence of electrolytes: competition between solute salting-out and salt-induced hydrotrope aggregation.

Water solubility enhancement is a long-standing challenge in a multitude of chemistry-related fields. Hydrotropy is a simple and efficient method to improve the solubility of hydrophobic molecules in aqueous media. However, the mechanism behind this phenomenon remains controversial. Herein the impact of salt doping on the hydrotropy phenomenon is determined experimentally using the ionic liquid (IL) 1-butyl-3-methylimidazolium chloride ([C4mim]Cl) as a hydrotope and vanillin as a solute. Hydrophobic interactions were found to be central to the aggregation of the hydrotrope around the solute, and seem to drive hydrotropy. Furthermore, 1H-NMR analysis indicates that hydrotrope-solute interactions present a degree of site-specificity. The addition of chloride salts in the presence of higher IL concentrations promotes a greater relative decrease of the vanillin solubility than in the corresponding system without the IL. This was assigned to the negative impact of increased hydrotrope pre-aggregation in the presence of inorganic salts. The results were rationalised using statistical thermodynamics through which hydrotrope aggregation prior to solute addition is shown to be detrimental to the hydrotropic effect, seemingly confirming solute-induced clustering of the hydrotrope to be the predominant mechanism of hydrotropy.

Prediction of Phase State of Secondary Organic Aerosol Internally Mixed with Aqueous Inorganic Salts.

In the presence of inorganic salts, secondary organic aerosol (SOA) undergoes liquid-liquid phase separation (LLPS), liquid-solid phase separation, or a homogeneous phase in ambient air. In this study, a regression model was derived to predict aerosol phase separation relative humidity (SRH) for various organic and inorganic mixes. The model implemented organic physicochemical parameters (i.e., oxygen to carbon ratio, molecular weight, and hydrogen-bonding ability) and the parameters related to inorganic compositions (i.e., ammonium, sulfate, nitrate, and water). The aerosol phase data were observed using an optical microscope and also collected from the literature. The crystallization of aerosols at the effloresce RH (ERH) was semiempirically predicted with a neural network model. Overall, the greater SRH appeared for the organic compounds with the lower oxygen to carbon ratios or the greater molecular weight and the higher aerosol acidity or the larger fraction of inorganic nitrate led to the lower SRH. The resulting model has been demonstrated for three different chamber-generated SOA (originated from β-pinene, toluene, and 1,3,5-trimethylbenzene), which were internally mixed with the inorganic aqueous system of ammonium-sulfate-water. For all three SOA systems, both observations and model predictions showed LLPS at RH <80%. In the urban atmosphere, LLPS is likely a frequent occurrence for the typical anthropogenic SOA, which originates from aromatic and alkane hydrocarbon.

Synergetic effect of ZnCo2O4/inorganic salt as a sustainable catalyst system for CO2 utilization

Currently, it is essential to consider the rapidly increasing emission of CO2 into the atmosphere, causing major environmental issues such as climate change and global warming. In this work, we have developed the binary catalyst system (ZnCo2O4/inorganic salt) for chemical fixation of CO2 with epoxides into cyclic carbonates without solvent, and all reactions were performed on a large scale using a 100 ml batch reactor. Two mesoporous catalysts of ZnCo2O4 with different architecture, such as flakes (ZnCo–F) and spheres (ZnCo–S) were synthesized and utilized as a heterogeneous catalyst for cycloaddition reaction. The bifunctional property of catalysts is mainly attributed to strong acidic and basic properties confirmed by TPD (NH3 & CO2) analysis. The ZnCo–F catalyst exhibited excellent conversion of propylene oxide (99.9%) with good corresponding selectivity of propylene carbonate (≥99%) in the presence of inorganic salt (KI) at 120 °C, 2 MPa, 3 h. In addition, ZnCo–F catalyst demonstrated good catalytic applicability towards the various substrates scope of the epoxide. Furthermore, the catalytic properties were examined by evaluating the reaction parameter such as catalyst loading, pressure, temperature and time. The proposed catalyst exhibited good reusability for cycloaddition reaction without significant change in its catalytic activity and proposed a possible reaction mechanism for chemical fixation of CO2 with epoxide into cyclic carbonate over ZnCo–F/KI.

Preparation of Poly(acrylate)/Poly(diallyldimethylammonium) Coacervates without Small Counterions and Their Phase Behavior upon Salt Addition towards Poly-Ions Segregation.

In this work, we report the phase behavior of polyelectrolyte complex coacervates (PECs) of poly(acrylate) (PA−) and poly(diallyldimethylammonium) (PDADMA+) in the presence of inorganic salts. Titrations of the polyelectrolytes in their acidic and alkaline forms were performed to obtain the coacervates in the absence of their small counterions. This approach was previously applied to the preparation of polymer–surfactant complexes, and we demonstrate that it also succeeded in producing complexes free of small counterions with a low extent of Hofmann elimination. For phase behavior studies, two different molar masses of poly(acrylate) and two different salts were employed over a wide concentration range. It was possible to define the regions at which associative and segregative phase separation take place. The latter one was exploited in more details because the segregation phenomenon in mixtures of oppositely charged polyelectrolytes is scarcely reported. Phase composition analyses showed that there is a strong segregation for both PA− and PDADMA+, who are accompanied by their small counterions. These results demonstrate that the occurrence of poly-ion segregation in these mixtures depends on the anion involved: in this case, it was observed with NaCl, but not with Na2SO4.

Membrane fusion of phospholipid bilayers under high pressure: Spherical and irreversible growth of giant vesicles

Membrane fusion of giant vesicles (GVs) for binary bilayers of unsaturated phospholipids, dioleoylphosphatidyl-ethanolamine (DOPE) having an ability to promote membrane fusion, and its homolog dioleoylphosphatidylcholine (DOPC) having an ability to form GV, was investigated under atmospheric and high pressure. While DOPC formed GVs in the presence of inorganic salts with a multivalent metal ion under atmospheric pressure, an equimolar mixture of DOPE and DOPC formed GVs both in the absence and the presence of LaCl3. We examined the change in size and shape of the GVs of this binary mixture in the absence and presence of LaCl3 as a function of time under atmospheric and high pressure. The size and shape of the GVs in the absence of LaCl3 under atmospheric and high pressure and those in the presence of LaCl3 under atmospheric pressure hardly changed with time. By contrast, the GV in the presence of LaCl3 under high pressure gradually changed in the size and shape with time on a time scale of several hours. Namely, the GV became larger than the original GV due to accelerated membrane fusion and its shape became more spherical. This pressure-induced membrane fusion was completely irreversible, and the growth rate was correlated with the applied pressure. The reason for the GV growth by applying pressure was considered on the basis of thermodynamic phase diagrams. We concluded that the growth is attributable to a closer packing of lipid molecules in the bilayer resulting from their preference of smaller volumes under high pressure. Furthermore, the molecular mechanism of the pressure-induced membrane fusion was explored by observing the fusion of two GVs with almost the same size. From their morphological changes, we revealed that the fusion is caused by the actions of Laplace and osmotic pressure.