Formation Of Membrane Structures Research Articles

Mechanism, structural and functional insights into nidovirus-induced double-membrane vesicles.

During infection, positive-stranded RNA causes a rearrangement of the host cell membrane, resulting in specialized membrane structure formation aiding viral genome replication. Double-membrane vesicles (DMVs), typical structures produced by virus-induced membrane rearrangements, are platforms for viral replication. Nidoviruses, one of the most complex positive-strand RNA viruses, have the ability to infect not only mammals and a few birds but also invertebrates. Nidoviruses possess a distinctive replication mechanism, wherein their nonstructural proteins (nsps) play a crucial role in DMV biogenesis. With the participation of host factors related to autophagy and lipid synthesis pathways, several viral nsps hijack the membrane rearrangement process of host endoplasmic reticulum (ER), Golgi apparatus, and other organelles to induce DMV formation. An understanding of the mechanisms of DMV formation and its structure and function in the infectious cycle of nidovirus may be essential for the development of new and effective antiviral strategies in the future.

The Influence of Physical Properties on the Membrane Morphology Formation during the Nonisothermal Thermally Induced Phase Separation Process.

The physical properties of a polymer solution that are composition- and/or temperature-dependent are among the most influential parameters to impact the dynamics and thermodynamics of the phase separation process and, as a result, the morphology formation. In this study, the impact of composition- and temperature-dependent density, heat capacity, and heat conductivity on the membrane structure formation during the thermally induced phase separation process of a high-viscosity polymer solution was investigated via coupling the Cahn-Hilliard equation for phase separation with the Fourier heat transfer equation. The variations of each physical property were also investigated in terms of different boundary conditions and initial solvent volume fractions. It was determined that the physical properties of the polymer solution have a noteworthy impact on the membrane morphology in terms of shorter phase separation time and droplet size. In addition, the influence of enthalpy of demixing in this case is critical because each physical property showed a nonhomogeneous pattern owing to the heat generation during phase separation, which in turn influenced the membrane morphology. Accordingly, it was determined that investigating spinodal decomposition without including heat transfer and the impact of physical properties on the morphology formation would lead to an inadequate understanding of the process, specifically in high-viscosity polymer solutions.

Effect of air gap induction on the morphological microstructure of polyether sulfone hollow fiber membrane

AbstractPolyether sulfone hollow fiber membrane was prepared via nonsolvent‐induced phase separation process using dimethylacetamide (DMAc) as a solvent, Polyvinylpyrrolidone (PVP‐K30) and water as additives. The mechanism of air gap environment in the membrane structure formation was studied. The scanning electron microscope microstructure morphology revealed that the air gap environment induced the microstructure formation of membranes. The low humidity air gap environment was not conducive to the surface pore formation and hard to obtain surface pores until lowering the dope solution temperature. The high humidity can easily induce the formation of large out surface pore structure along with the decreases of the surface pore uniformity. As air gap humidity and distance increased, the membrane cross section structure near the outer surface tends to be looser and that near the inner surface became denser, while the proportion of finger‐like pores in the cross section initially increased and stabilized. At 100 RH, the average outer surface pore size increased from 0.192 μm at an air gap distance of 20 cm to 0.351 μm at 50 cm, the corresponding pore density decreased from 2.66 to 1.13 pores/μm2, and the percentage of the inner skin layer thickness increased from 3.26% to 7.69%.

Experimental phase diagram for the PVDF – DMAc– water ternary system with new topology: Method of construction, thermodynamics, and structure formation of membranes

Ternary mixtures of a semicrystalline (SC) polymer with a solvent and a nonsolvent are widely used primarily for preparation of membranes by nonsolvent induced phase separation (NIPS). A detailed analysis of the published studies devoted to phase equilibrium in such systems showed that the phase diagrams were either incomplete or presented in a schematic form. In the present paper, we propose a new method of plotting the ternary phase diagrams for the SC polymer – solvent – nonsolvent mixtures. This method is based on finding the location of the isotherm intersection with the curves on the temperature–composition pseudobinary phase diagrams for the SC polymer mixtures with solvent and binary mixtures of solvent and nonsolvent of different composition. The coordinates of the intersection points were used to plot for the first time the complete ternary phase diagram for the widely used mixture of polyvinylidene fluoride (PVDF) with dimethyl acetamide (DMAc) and water. The curves on the phase diagram separate the regions of homogeneous mixtures, coexistence of two liquids, macroscopically uniform gels (swollen SC polymer) and coexistence of such gels with liquid. Using the plotted phase diagram, a new understanding of the NIPS mechanism was proposed and confirmed by direct microscopic observation of the NIPS process and SEM analysis of the membranes obtained following this way. An unexpected result of the study is discovery of the crystalline complexes in the mixtures of PVDF and DMAc, which was confirmed using both DSC and XRD techniques.

High hydrogen permselective carbon molecular sieve membrane and its structural formation mechanism

A novel hydroxyl-containing polyetherimide (named BAHPPF-ODPA) with highly aromatic backbone and contorted chain conformation was designed and synthesized as the precursor to fabricate carbon molecular sieve membranes (CMSMs) for H2/N2 separation. The structural evolution from polymeric precursor to carbon during pyrolysis was investigated using characterization techniques combined with pyrolysis simulation. And the relationship between membrane structure formation and their separation performance was explored here. Results indicate that the generation and evolution of pyrolysis products including formed fragments and gases, which depend on the precursor chemistry and pyrolysis conditions, exhibited a significant influence on microstructure and performance of derived CMSMs. Designing precursors with an aromatic backbone and contorted structure and precisely tuning pyrolysis temperature allows the fabrication of CMSMs with controllable micropore structure and excellent H2 separation performance. The BAHPPF-ODPA derived CMSM pyrolyzed at 600 °C exhibited the high H2 permeability of about 3500 Barrer and the superior H2/N2 selectivity of more than 400 were obtained after 750 h of long-term mixed gas (75:25 mixture of H2/N2) testing, showing promising application prospects. The experimental and simulation results obtained here would be beneficial to understand the CMS formation and reasonable to design the precursor molecular structure for fabrication of high-performance CMSMs.

Study on Improving Loess Properties with Permeable Polymer Materials.

Loess has strong water sensitivity, strong collapsibility, and low strength resulting in failures such as landslides, due to its loose structure. In order to improve the loess characteristics and to better meet the needs of engineering, a colorless, transparent, and permeable composite material is proposed in this paper. Water stability, erosion, unconfined compression, and triaxial tests were conducted to investigate the change of the strength properties and soil erosion resistance. The water sensitivity and strength properties of the loess are significantly improved as the stabilizer concentration increases. When scoured for 20 min, the erosion rates of the reinforced and the unreinforced soil were 95% and 6.25%, respectively, and demonstrated a 15.12 times reduction in erosion rates. The optimal concentration of the mixed solution is 0.6%. The triaxial test, CT, and SEM scanning tests were used to reveal the intrinsic mechanisms. The results demonstrated that the internal friction angle of the reinforced soil increases from 28.09° to 30.57°, and the cohesion changes from 25 kPa to 37.4 kPa. A large number of pores with a diameter of 900–1000 μm are reduced to 0–200 μm, and some pores with a length greater than 600 μm reduce to a length of less than 200 μm; The agglomeration and cementation, the filling of pores, and the formation of membrane structures have contributed greatly to the improvement of loess properties. Furthermore, the newly composite material has significant application potential needed to stabilize soil.

β2-Integrins - Regulatory and Executive Bridges in the Signaling Network Controlling Leukocyte Trafficking and Migration.

Leukocyte trafficking is an essential process of immunity, occurring as leukocytes travel within the bloodstream and as leukocyte migration within tissues. While it is now established that leukocytes can utilize the mesenchymal migration mode or amoeboid migration mode, differences in the migratory behavior of leukocyte subclasses and how these are realized on a molecular level in each subclass is not fully understood. To outline these differences, first migration modes and their dependence on parameters of the extracellular environments will be explained, as well as the intracellular molecular machinery that powers migration in general. Extracellular parameters are detected by adhesion receptors such as integrins. β2-integrins are surface receptors exclusively expressed on leukocytes and are essential for leukocytes exiting the bloodstream, as well as in mesenchymal migration modes, however, integrins are dispensable for the amoeboid migration mode. Additionally, the balance of different RhoGTPases – which are downstream of surface receptor signaling, including integrins – mediate formation of membrane structures as well as actin dynamics. Individual leukocyte subpopulations have been shown to express distinct RhoGTPase profiles along with their differences in migration behavior, which will be outlined. Emerging aspects of leukocyte migration include signal transduction from integrins via actin to the nucleus that regulates DNA status, gene expression profiles and ultimately leukocyte migratory phenotypes, as well as altered leukocyte migration in tumors, which will be touched upon.

The effect of 3D printing parameters on electrochemical properties of heterogeneous cation exchange membrane

PurposeThe study aims to focus on the preparation of a heterogeneous cation exchange membrane by a three-dimensional (3D) method – fused filament fabrication using a series of nozzles of various diameters (0.4–1.0 mm). Polypropylene random copolymer (PPR) as a polymeric binder was mixed with 50 Wt.% of the selected conventional cation exchange resin, and a filament was prepared using a single screw mini extruder. Then filament was processed by FFF into the membranes with a defined 3D structure.Design/methodology/approachElectrochemical properties, morphology, mechanical properties and water absorption properties were tested.FindingsDependence of the tested properties on the used nozzle diameter was found. Both areal and specific resistances increased with increasing nozzle diameter. The same trend was also found for permselectivity. The optimal membrane with permselectivity above 90%, areal resistance of 8 O.cm2 and specific resistance of 124 O.cm2 was created using a nozzle diameter of 0.4 mm.Originality/valueUsing new materials for 3D print of cation exchange membrane with production without waste. The possibility of producing 3D membranes with a precisely defined structure and using a cheap 3D printing method. New direction of membrane structure formation. 3D-printed heterogeneous cation exchange membranes were prepared, which can compete with commercial membranes produced by conventional technologies. 3D-printed heterogeneous cation exchange membranes were prepared, which can compete with commercial membranes produced by conventional technologies.

Фотоабляция с рибофлавином как альтернатива применению Митомицина-С в эксимерной лазерной хирургии роговицы

Purpose. To substantiate the advantages of photoablation with riboflavin as an alternative to the use of Mitomycin-C in excimer laser surgery of the cornea. Material and methods. The work is based on clinical observations of the results of 598 photorefractive and phototherapeutic operations. In all cases, keratoablation was performed after drip, aerosol, or combined saturation of the stroma with 0.1% or 0.25% isotonic riboflavin solution. Corneal OCT was performed on RTVue 100 and RTVue XR100 devices. Keratotopographic and densitometric studies were performed on a TMS-5 device. Results. With photokeratoablation of the stroma saturated with riboflavin, the response aseptic inflammatory and regenerative reactions, the severity and duration of the corneal syndrome decreased. In densitometry and OCT studies, an increase in optical density was noted with the formation of a membrane structure on the ablation surface and the effect of cross-linking in the stromal layers adjacent to the ablation zone. Shielding of induced secondary radiation by riboflavin and the formation of a Bowman-like membrane structure made it possible to avoid the development of an irreversible form of fibroplasia and a decrease in visual acuity. The formed membrane structure with cross-linking in the underlying stromal layers was a barrier between pro-inflammatory epithelial and stromal cytokines, which predetermine the development of fibroplasia during photokeratoablation. Conclusion. Photokeratoablation with riboflavin prevents the development of an irreversible form of fibroplasia and can be considered as an alternative to the use of Mitomycin-C in photorefractive and phototherapeutic operations on the cornea by radiation from an argon-fluorine excimer laser. Key words: Mitomycin-C, riboflavin, fibroplasia, excimer laser corneal surgery, laser-induced crosslinking.

Structure control of hydrophilized PVDF hollow-fiber membranes using amphiphilic copolymers: PMMA-co-P (HEMA-co-MEA)

An amphiphilic copolymer was used in the fabrication of hydrophilized poly (vinylidene fluoride) (PVDF) membranes. The amphiphilic copolymer was synthesized via the catalytic chain transfer radical polymerization (CCTP) of poly (methyl methacrylate) macromonomer (PMMA-MM), 2-hydroxyethyl methacrylate (HEMA), and 2-methoxyethyl acrylate (MEA). The copolymer, PMMA-co-P (HEMA-co-MEA) with various copolymerization ratios of HEMA and MEA was added to a stock solution containing PVDF, poly (vinylpyrrolidone) (PVP) and N,N-Dimethylacetamide (DMAc) in the preparation of hollow-fiber membranes via the non-solvent induction phase separation (NIPS) method. The resultant membrane had various porous structures and hydrophilicity. The permeability of the resultant membrane tended to be higher when a copolymer with a lower HEMA copolymerization ratio was added. The membrane was prepared using a copolymer with a high composition ratio of HEMA and had a structure that featured a smaller pore diameter and less connectivity in the inner surface, which reduced the water permeability. Amphiphilic copolymers would interfere with the formation of membrane structure. On the other hand, the surface hydrophilicity was better than that of a blank PVDF membrane, which revealed an interesting trade-off between hydrophilicity and water permeability.

Plasma Polymer Layers with Primary Amino Groups for Immobilization of Nano- and Microparticles

The assembly of nano- and micro-scale building blocks on surface has been the focus of intense interest in materials science for years. In this work, (3-aminopropyl)triethoxysilane (APTES) carrying one primary amino group was deposited on various substrate surfaces using the plasma polymerization method. The key plasma parameters i.e. pressure and power were varied to obtained the highest density of primary amino groups. The influence of such parameters on the characteristics of deposited layers (e.g. chemical structure, adhesion strength, growth rate, etc.) was systemically investigated using various characterization methods such as XPS, FTIR, ellipsometry and so on. Meanwhile, three types of particles (AuNPs, zeolites and gold@zeolites) with sizes from nano- to submicro-range were synthesized and further used as model building blocks. Subsequently, the prepared particles were deposited onto cyclic olefin copolymer (COC) substrate surfaces, which were pre-functionalized by deposition of the plasma polymer layer using the parameters of pressure = 1.0 mbar and power = 30 W. The results confirmed the formation of membrane structures consisting of highly packed particles on the COC surface, and such immobilized structures showed high stability against flowing water, evidencing the good immobilization ability of deposited APTES layers with amino groups.

Unconfined Compressive Strength of Aqueous Polymer-Modified Saline Soil

Saline soil is a special soil that consists of fine particles and has poor engineering properties. It causes salt heaving and is collapsible and corrosive. The treatment of this type of soil for the use as a resource for roadbed fillings has been one of the most important engineering topics in highway construction near coastal areas. This study introduces a new type of aqueous polymer, called ZM, which is used to amend and stabilize saline soil. To test the effects of ZM-solidified saline soil, unconfined compressive strength (UCS) tests were carried out on unmodified and ZM-modified saline soil specimens, respectively. The test results show that the ZM additive significantly improves the UCS. Based on the increase of the ZM admixture, the UCS increases with the curing time. The main increment of the UCS occurs within the first seven days of curing. In addition, the salt content has a great influence on the UCS. With increasing ZM concentration and curing time, the water stability and wetting-drying cycling resistance improve. Based on the X-ray diffraction results, the diffraction peaks of ZM-modified saline soil insignificantly change compared with those of unmodified saline soil. However, the SEM images indicate the formation of membrane structures in ZM-modified saline soil. The modification process produces denser and more stable soil because the reaction products fill voids inside the soil and form a viscous membrane structure on the soil surface.

Comparison of artificial dermis Lando® versus Pelnac® combined with induced membrane technique in treatment of composite trauma in rabbit bilateral femurs

Objective To compare 2 kinds of artificial dermis Lando® versus Pelnac® combined with induced membrane technique in the treatment of composite trauma in rabbit bilateral femurs. Methods Twenty-seven male rabbits, weighing from 1.92 kg to 2.21 kg (average, 2.04 kg), were used in the experiments. After models of composite trauma were created in the bilateral femurs of all the rabbits, the bilateral femurs of 9 random rabbits were subjected to the treatment of artificial dermis Lando® plus induced membrane (Lando® group), the bilateral femurs of another 9 random rabbits to the treatment of artificial dermis Pelnac® plus induced membrane (Pelnac® group), the left femur of the remaining 9 rabbits to the treatment of induced membrane (control group) and the right femur of the remaining 9 rabbits to no treatment (sham operation group). Three rabbits from each group (the same for the control and sham operation groups) were randomly sacrificed at 2, 4 and 6 weeks after operation. Samples from the operation sites were taken for gross observation of the induced membrane and observation of the microstructure of the membrane by conventional hematoxylin-eosin staining. In addition, the microvessel density (MVD) was counted under microscopy taking CD34 immunohistochemistry as the standard. The data were statistically analyzed. Results The collagen sponge layer was completely degraded 2 weeks after operation in the Lando® group but not in the Pelnac® group. The MVD [(0.90±0.55)/HPF] in the Lando® group was significantly greater than that in the Pelnac® group [(0.28±0.13)/HPF] (P 0.05). At 6 weeks postoperatively, the MVD [(4.97±0.76)/HPF] in the Lando® group was significantly smaller than that in the Pelnac® group [(7.06±1.03)/HPF] (P 0.05). The MVD at 4 and 6 weeks after operation in the control and the sham operation groups were all significantly different from those in the Lando® and the Pelnac® groups (P<0.05). Conclusions In the treatment of composite trauma in rabbits, the 2 kinds of artificial dermis combined with the induction membrane technique can lead to formation of induced membrane structure, providing a new alternative treatment for patients with bone and soft tissue defects caused by various causes in the clinic. The Lando® artificial dermis may accelerate the vascularization of induced membrane at 2 weeks while the Pelnac® may accelerate the vascularization at 4 and 6 weeks. Key words: Femur; Dermis; Soft tissue injuries; Artificial dermis; Bone defect

Effect of Pluronic F127 on porous and dense membrane structure formation via non-solvent induced and evaporation induced phase separation

Novel porous and dense membranes based on polysulfone (PSF) modified by poly(ethylene glycol)–b–poly(propylene glycol)–b– poly(ethylene glycol) (Pluronic F127) were developed. The influence of Pluronic F127 introduction to the casting solution on different types of polymer membrane formation via two different phase inversion techniques—non-solvent induced phase separation (NIPS) for porous membranes and evaporation induced phase separation (EIPS) for dense membranes—was investigated. According to the triangular phase diagram obtained, PSF-Pluronic F127-N,N-dimethylacetamide (DMAc) systems feature lower critical solution temperature and have a tendency to micelle formation due to Pluronic F127 self-assembly. The structure, hydrophilic-hydrophobic balance and physicochemical properties of PSF-Pluronic F127 membranes were characterized by water contact angle measurements, scanning electron microscopy, nuclear magnetic resonance, small-angle X-ray scattering, and atomic force microscopy. The performance of dense membranes in pervaporation separation of water-ethyl acetate mixtures was investigated to reveal the effect of Pluronic F127 on the structure and free volume of the PSF-Pluronic F127 membranes. It was shown that Pluronic F127 introduction to the casting solution during membrane formation via two different techniques (NIPS and EIPS) leads to the increase in the pore size of the porous membranes and free volume of the dense membranes, as well as the increase in flux and surface hydrophilicity for both membrane types. Pluronic F127 was found to improve the antifouling performance of porous PSF-Pluronic F127 membranes in the BSA solution ultrafiltration. The introduction of 3 wt% Pluronic F127 into dense PSF membrane improved permeation flux in 1.7 and 2.7 times (15.1 and 27.3 g/(m2h)) at high selectivity level (100 wt% water in the permeate) during the separation of ethyl acetate-water mixtures (2 and 4 wt% ethyl acetate) compared to pristine PSF membrane.

Flory-Huggins Based Model to Determine Thermodynamic Property of Polymeric Membrane Solution

Flory-Huggins (F-H) model has been widely used to analyze the thermodynamic behavior of polymeric membrane solution during the formation of membrane structure in a phase inversion process. The F-H model involves concentration and binary interaction parameter of components in membrane solution. Those parameters are used to calculate the composition of membrane solution at equilibrium which is then plotted on ternary diagram known as a binodal curve. The binodal curve is used to determine the type of demixing of the polymeric membrane solution and to predict the structure of resulted membrane. Several modifications of F-H model have been conducted in relation to composition (ternary or quaternary) and temperature of the membrane solution. In this paper, the development of F-H model used in designing polymeric membrane by phase inversion method, particularly immersion precipitation method, will be reviewed. The structure and performance of membranes that are governed by the thermodynamic property of the membrane solution based on F-H model will be discussed.

Activation of aryl hydrocarbon receptor regulates the LPS/IFNγ-induced inflammatory response by inducing ubiquitin-proteosomal and lysosomal degradation of RelA/p65

Several studies have identified the aryl hydrocarbon receptor (AhR) as a negative regulator of the innate and adaptive immune responses. However, the molecular mechanisms by which this transcription factor exerts such modulatory effects are not well understood. Interaction between AhR and RelA/p65 has previously been reported. RelA/p65 is the major NFκB subunit that plays a critical role in immune responses to infection. The aim of the present study was to determine whether the activation of AhR disrupted RelA/p65 signaling in mouse peritoneal macrophages by decreasing its half-life. The data demonstrate that the activation of AhR by TCDD and β-naphthoflavone (β-NF) decreased protein levels of the pro-inflammatory cytokines TNF-α, IL-6 and IL-12 after macrophage activation with LPS/IFNγ. In an AhR-dependent manner, TCDD treatment induces RelA/p65 ubiquitination and proteosomal degradation, an effect dependent on AhR transcriptional activity. Activation of AhR also induced lysosome-like membrane structure formation in mouse peritoneal macrophages and RelA/p65 lysosome-dependent degradation. In conclusion, these results demonstrate that AhR activation promotes RelA/p65 protein degradation through the ubiquitin proteasome system, as well as through the lysosomes, resulting in decreased pro-inflammatory cytokine levels in mouse peritoneal macrophages.

Tuning the ion selectivity of porous poly(2,5-benzimidazole) membranes by phase separation for all vanadium redox flow batteries

Porous polybenzimidazole membranes have been suggested by far as the most promising candidate to replace perfluorinated ionomer membranes in all vanadium redox flow batteries (VRFB). These porous membranes can simply be prepared from a phase separation process induced by water vapor. In this work, the influence of the material properties of poly(2,5-benzimidazole) (ABPBI) on the membrane structure formation and ion transport characteristics is systematically investigated. Two batches of ABPBI polymers (intrinsic viscosity 2.0 and 1.4 dL g−1) are used; concentrations of polymer solution, the water vapor activity (temperature and relative humidity), and the exposure time of polymer solution to the water vapor are varied. It is found that high viscosity of ABPBI solution, among other factors, is essential in obtaining membranes with very low interconnectivity between macropores in the membrane bulk, therefore very low vanadium ion permeability suitable for VRFB applications. The porous ABPBI membranes in dry state have a low amount of pores ranging from 1 to ~ 200 nm. Due to the benzimidazole moieties in ABPBI polymers, the acid in vanadium electrolytes has two positive effects on ABPBI membranes: fixed positive charges, and absorption of acid in the membranes. The ion exchange capacity of ABPBI membranes increases with the increase in solution acid concentration, and reaches striking values as high as 8 mequ g−1 in 4.0 M H2SO4. This makes the Donnan exclusion towards positively charged vanadium ions very profound. The macropores in the porous membranes increase the absorption amount of free acid, therefore significantly increase the membrane ionic conductivity. These properties make porous ABPBI membranes very efficient separators for VRFB applications.

Autophagy in the context of the cellular membrane-trafficking system: the enigma of Atg9 vesicles.

Macroautophagy is an intracellular degradation system that involves the de novo formation of membrane structures called autophagosomes, although the detailed process by which membrane lipids are supplied during autophagosome formation is yet to be elucidated. Macroautophagy is thought to be associated with canonical membrane trafficking, but several mechanistic details are still missing. In this review, the current understanding and potential mechanisms by which membrane trafficking participates in macroautophagy are described, with a focus on the enigma of the membrane protein Atg9, for which the proximal mechanisms determining its movement are disputable, despite its key role in autophagosome formation.

Dissipative particle dynamics simulation on the membrane formation of polymer–solvent system via nonsolvent induced phase separation

A new dissipative particle dynamics (DPD) simulation methodology adopting a mass transfer algorithm was established to investigate the membrane formation process via nonsolvent induced phase separation (NIPS). The effect of the interphase mass transfer between the casting solution and the nonsolvent bath on the membrane formation process and the membrane morphology was elaborately analyzed. Factors including the solvent–nonsolvent interaction, the polymer concentration and the nonsolvent temperature were considered. The results showed that as the solvent-nonsolvent interaction got better, the mass transfer was intensified which contributed to an intense phase separation. Thereby asymmetric membrane morphology with a thick dense surface layer and a porous sub-layer would be formed. With the nonsolvent temperature raising, the relatively symmetric morphology with small pores was obtained due to the declined polymer aggregation rate and the increased phase separation rate caused by the accelerated mass transfer. As the polymer concentration increased, the flexibility of the system reduced. Thereby the phase separation slowed down, resulting in highly asymmetric morphology with a thicker and denser surface layer and a more porous sub-layer. The analysis of the phase separation in this study benefits to a better understanding on the mechanism of the membrane structure formation via NIPS.

Membrane lipids and soluble sugars dynamics of the alkaliphilic fungus Sodiomyces tronii in response to ambient pH.

Alkaliphily, the ability of an organism to thrive optimally at high ambient pH, has been well-documented in several lineages: archaea, bacteria and fungi. The molecular mechanics of such adaptation has been extensively addressed in alkaliphilic bacteria and alkalitolerant fungi. In this study, we consider an additional property that may have enabled fungi to prosper at alkaline pH: altered contents of membrane lipids and cytoprotectant molecules. In the alkaliphilicSodiomyces tronii, we showed that at its optimal growth pH 9.2, the fungus accumulates abundant cytosolic trehalose (4-10% dry weight) and phosphatidic acids in the membrane lipids, properties not normally observed in neutrophilic species. At a very high pH 10.2, the major carbohydrate, glucose, was rapidly substituted by mannitol and arabitol. Conversely, lowering the pH to 5.4-7.0 had major implications both on the content of carbohydrates and membrane lipids. It was shown that trehalose dominated at pH 5.4. Fractions of sphingolipids and sterols of plasma membranes rapidly elevated possibly indicating the formation of membrane structures called rafts. Overall, our results reveals complex dynamics of the contents of membrane lipids and cytoplasmic sugars in alkaliphilicS. tronii, suggesting their adaptive functionality against pH stress.