Characterization Of Membranes Research Articles

Experimental Determination of the Gas Transport Characteristics of Polysuflone and Polyphenyleneoxide Hollow-Fiber Membranes in Relation to Noble Gases

This paper presents an an experimental study of commercially available hollow fiber membranes made of two polymers, polysulfone and polyphenylene oxide. The main objective is to determine the gas transport characteristics of these membranes with respect to air components and noble gases. Therefore, the permeabilities of the membranes for nitrogen, oxygen, helium, argon, xenon and krypton were determined as part of this study. Particular attention is paid to the xenon-containing air mixture, since the problem of capturing medical xenon seems to be an urgent chemical and technological problem due to the high cost of the process of obtaining this gas. In the course of the study, the values of the permeability of two membranes for pure gases were determined and the values of ideal selectivity were calculated. Thus, the membrane permeability values for argon, krypton, and xenon were 20.8, 8.4, and 6.8 GPU for the polysulfone membrane and 19.5, 6.2, and 4.8 GPU for the polyphenylene oxide membrane. It was found that the xenon permeability of these membranes decreases in the case of separation of a gas mixture consisting of oxygen nitrogen and xenon and is 5.9 and 4.1 GPU for polysulfone and polyphenylene oxide, respectively. The dependence of the performance of membrane modules based on polysulfone and polyphenylene oxide on the total area of the membrane has also been established.

Rational synthesis of total damage during cryoprotectant equilibration: modelling and experimental validation of osmomechanical, temperature, and cytotoxic damage in sea urchin (Paracentrotus lividus) oocytes.

Sea urchins (e.g., Paracentrotus lividus) are important for both aquaculture and as model species. Despite their importance, biobanking of urchin oocytes by cryopreservation is currently not possible. Optimized cryoprotectant loading may enable novel vitrification methods and thus successful cryopreservation of oocytes. One method for determining an optimized loading protocol uses membrane characteristics and models of damage, namely osmomechanical damage, temperature damage (e.g., chill injury) and cytotoxicity. Here we present and experimentally evaluate existing and novel models of these damage modalities as a function of time and temperature. In osmomechanical damage experiments, oocytes were exposed for 2 to 30 minutes in hypertonic NaCl or sucrose supplemented seawater or in hypotonic diluted seawater. In temperature damage experiments, oocytes were exposed to 1.7°C, 10°C, or 20°C for 2 to 90 minutes. Cytotoxicity was investigated by exposing oocytes to solutions of Me2SO for 2 to 30 minutes. We identified a time-dependent osmotic damage model, a temperature-dependent damage model, and a temperature and time-dependent cytotoxicity model. We combined these models to estimate total damage during a cryoprotectant loading protocol and determined the optimal loading protocol for any given goal intracellular cryoprotectant concentration. Given our fitted models, we find sea urchin oocytes can only be loaded to 13% Me2SO v/v with about 50% survival. This synthesis of multiple damage modalities is the first of its kind and enables a novel approach to modelling cryoprotectant equilibration survival for cells in general.

Analysis of the Sound Pressure in Membrane-Sealed Pistonphone

Compared with the clearance-sealed pistonphone, the membrane-sealed pistonphone can realize the sound pressure at very low frequency and very high sound pressure for its lower leakage. However, the membrane-sealed pistonphone also brings the problem that the compressed volume cannot be decided precisely because of the deformation of the membrane, which results in the inaccurate calculation for the sound pressure in the chamber. In this paper, a sound pressure formula for the membrane-sealed pistonphone is derived according to an analysis of the characteristics of the ideal membrane. The static and the dynamic deformation of the membrane are studied. Then, the effects of the thickness, the sealed width, the extension ratio, and the modal vibration of the membrane are studied through the finite element method. The results show that the deviation of the sound pressure level obtained from the ideal sound pressure formula can be reduced to less than 0.1[Formula: see text]dB when the sound pressure level is lower than 174[Formula: see text]dB and the membrane is specially designed, which indicates that the influence of the membrane on the sound pressure is almost negligible.

A Control Method for Output Voltage Stability of Proton Exchange Membrane Fuel Cells

The widely used PEMFC (Proton Exchange Membrane Fuel Cell) analysis found that when the REMFC load is changed, its instantaneous output voltage fluctuates, and it causes voltage loss. The main reason is that it is activated by activation. The characteristics of the three-proton exchange membrane fuel battery characteristics of Ohm overvoltage and thickness cause voltage loss. By using the corresponding empirical formula in the Matlab / Simulink environment, the study designs the PID and the Fuzzy PID Controllers. After the established dynamic model of PEMFC, it controls the hydrogen supply module, changes the ratio of hydrogen and oxygen input, and indirectly controls the output voltage. Through experiments, it was found that Fuzzy PID Controller can achieve faster and smoother voltage stability than an ordinary PID Controller and less overshoot when load change, The controller can control the system voltage to reach a set point and to stabilize the supply voltage for the load.

Novel hexa-fluorinated intrinsically porous polyimide membranes for the desalination of high saline water by air-gap membrane distillation

Hexa-fluorinated porous membranes were prepared from 4,4′-(hexafluoroisopropylidene) diphtalic anhydride (6FDA)- 2,3,5,6- tetramethyl-p-phenylenediamine (TMPD) (6FDA-TMPD), which prepared by a polycondensation reaction between the dianhydride 6FDA and the diamine TMPD at 200 °C, by nonsolvent induced phase inversion process for the desalination of highly saline water (70,000 mg L−1) via membrane distillation (MD) technology. Here, for the first time, we demonstrate the significance of the intrinsic porosity of 6FDA-TMPD polyimide membranes, that not only result in an excellent performance in MD without the addition of porogen chemicals but also outperform other membranes including commercially available membranes. The membrane characteristics were optimized by varying the coagulation bath, dope solution concentration, and thickness. Notably, the developed membranes possess high porosity which can be attributed to the high BET surface area (550 m2 g−1) of 6FDA-TMPD. Membranes developed from an ethanol-based coagulation bath resulted in spongy-like morphology and demonstrated excellent desalination performance with a high flux (∼ 18.20 kg m−2 h−1) and stable salt rejection (> 99.96 %). The reported fabrication approach can be used to delineate the key design parameters for the fabrication of highly efficient intrinsically porous polyimide-based membranes which may pave the way for the practical application of MD for the desalination of highly saline water.Graphical abstract.

PREPARATION AND CHARACTERIZATION OF FLY ASH ADDITIVE MODIFIED POLIESTER BASED MEMBRANE

Recently, Polyethersulfone (PES) polymer material based on flat sheet membranes reached much attention in membrane technology. However, PES polymer has low hydrophilicity. This study describes PES-based membranes incorporating fly ash as an additive. The first analysis was conducted by Fourier Transform Infrared, Scanning Electron Microscope, tensile strength, and porosity tests. Four membranes, including pure PES membranes, were prepared via the phase inversion process, namely MA–0, MA–0.1, MA–1, and MS–1. The characteristics of the membrane samples were analyzed in terms of chemical group, morphology, mechanical and membrane surface hydrophilicity. The characterization results show that additive incorporation increased pure water flux performance, and the highest pure water permeability increased up to 70% by the MA–1 membrane. Moreover, it increased by 19% compared to pure silica-modified PES membrane (MS–1). In addition, the MA-1 membrane at a pressure of 3 bar reached significant performance in the trend of pure water flux values because of these improvements in membrane characteristics. The membrane also shows a higher tensile strength with adding additives to the membrane prepared.

Cutting characteristics of viscoelastic membranes under hypodermic needle insertion

Cutting characteristics of thin membranes and the mechanics of their interactions with sharp aggressors like needles are critical in many industrial and medical applications. In this study, we performed needle insertion experiments to study the cutting behaviour of membranes made with polyethylene (PE) and nitrile butadiene rubber (NBR) and investigated different stages of the procedure by analyzing the needle reaction force. Moreover, using a detailed parametric study, we investigated the effect of different insertion and membrane parameters on the most important features of the insertion process. The results showed that, in most cases, the crack size, maximum insertion force, puncture displacement, kinetic frictional force, and static frictional force increase with the increase of needle diameter, increase of membrane thickness, or inclining of the needle. On the other hand, the effect of the velocity on features of the insertion process is negligible except for the kinetic frictional force which increases with the insertion velocity. We also showed although lubrication cannot considerably change the maximum needle insertion force into thin membranes, it can substantially decrease the puncture displacement and frictional forces. Furthermore, we observed that the maximum insertion force, puncture displacement, and frictional forces for PE are greater than the values obtained for NBR, while the crack sizes obtained for PE are smaller than those for NBR. Additionally, we proposed a combined experimental-numerical approach using finite-element (FE) modelling to calculate fracture toughness. The fracture toughness values obtained for PE and NBR are 6.66 ± 1.16 kJ/m2 and 3.98 ± 0.56 kJ/m2, respectively. We also exploited the developed finite-element model to predict the whole-field membrane deformation and its mechanical stress.

The Changes of Phenotypic Characteristics of Shewanella putrefaciens under Cold Adaptation

Shewanella putrefaciens (S. putrefaciens) is frequently detected as a serious threat to food safety because it causes spoilage of aquatic products during cold chain transportation. Here, we studied phenotypic changes in S. putrefaciens at low temperatures to discuss the specific behavior of its spoiled aquatic products. S. putrefaciens was found to grow considerably through the growth curve at 0–30°C. In order to investigate the strong putrefaction of aquatic significant amounts under cold storage at 0–10°C, SEM was used to examine the microstructure of S. putrefaciens that had been cultivated at various temperatures. At low temperatures, it was discovered that the cell membrane surface of S. putrefaciens was smoother. FITC-labeled fluorescence microscope was used to view the results. Analysis of S. putrefaciens cultivated at various temperatures revealed that the integrity and permeability of the cell membrane deteriorated with the drop of culture temperature; however, the downward trend slowed down when the temperature was below 10°C. In addition, as the temperature continued to drop below 10°C, the capacity of S. putrefaciens to build biofilms did not diminish noticeably. The findings demonstrate that S. putrefaciens’s cold adaptation mechanism at low temperatures involves modifications to the morphological and phenotypic characteristics of cell membranes, plays a significant role in the organism’s ability to corrode aquatic products at low temperatures, and provides an important target for prevention and control of S. putrefaciens’ ability to contaminate aquatic products and cause financial losses.

Investigation of the performance parameters for a PEMFC by thermodynamic analyses: Effects of operating temperature and pressure

In the present study, thermodynamic performance characteristics of the proton exchange membrane fuel cell (PEMFC) at ranging operating temperatures and pressures were examined through energy and exergy analyses. The energy and exergy figures of the reactants and products were taken into account by thermodynamic analysis. In addition, the significant parameters such as destroyed exergy, entropy generation, thermal efficiency, and exergy efficiency were calculated at the aforementioned conditions to give more knowledge regarding the PEMFC. In conclusion, the power density and exergy efficiency improved as the operating temperature of the FC boosted. When the current density was 1, the exergy efficiency increased by 13.17% as the operating temperature ascended from 303 K to 363 K. At all operating temperatures, the augmentation in current density caused irreversibility, so entropy generation ascended. Since the increase in operating temperature led to an increase in power density, amount of exergy that was destroyed declined. Augmentation of the working pressure at constant temperature did not remarkably enhance the exergy efficiency. In the case of a current density of 1, the exergy efficiency values at the operating pressures of 3 atm and 12 atm were found to be 54.42% and 53.79%, respectively.

KH550‐SiO2/polyimide insulating paper preparation and characterisation

AbstractOil‐paper insulation material is an essential component for oil‐filled transformers, and polyimide (PI) insulation paper is a novel material in the field of electricity. The improvement of insulation class for insulation paper has gained significant attention in recent years. In this study, SiO2 nanoparticles were modified with a silane coupling agent (KH550), and the KH550‐SiO2 was added to the fibre membrane through in situ polymerisation. The chemical composition and microcosmic characteristics of the PI porous fibre membrane were characterised using FT‐IR and SEM FT‐IR and SEM. Consequently, the dielectric constant of the composite paper was reduced to 2.3 upon adding 3 wt% of KH550‐SiO2, and the dielectric strength reached its maximum value of 85 kV/mm. The results demonstrate that the insulation performance of the KH550‐SiO2/PI composite was significantly improved due to the incorporation of nano‐SiO2. This establishes an efficient approach for achieving excellent electrical and thermal properties in practical applications using the KH550‐SiO2/PI fibre membrane.

In situ synchrotron quantitative analysis of competitive adsorption tendency of human serum protein to different clinical hemodialysis membranes and assessment of potential impacts

Protein adsorption on hemodialysis (HD) membrane matrices and surfaces is a highly undesirable process, as it triggers complement activation and leads to severe health complications for HD patients. However, there is a lack of systematic research investigating the correlation between membrane characteristics and their performance in the dialysis process. This study aims to provide a comprehensive understanding of the competitive adsorption tendencies of three human serum proteins (albumin (HSA), fibrinogen (FB), and transferrin (TRF)) on clinical dialysis membranes composed of polyethersulfone (PES), polyacrylonitrile (PAN), and polyvinyl fluoride (PVDF) polymers. To assess membrane morphology across the membrane cross-section, in situ synchrotron radiation micro-computed tomography (SR-µCT) imaging was conducted at the Canadian Light Source (CLS). Protein adsorption was analyzed qualitatively and quantitatively using an innovative synchrotron-based X-ray tomography technique. To determine the mutual influence of protein species on overall protein adsorption, adsorption from single-protein solutions was compared to adsorption from a protein mixture. Regarding single-protein adsorption, the PVDF membrane exhibited 40% less adsorption of HSA compared to the PES membrane. Conversely, FB adsorption was approximately 25% higher on the PVDF membrane compared to the PES membrane. The PAN membrane showed similar levels of HSA adsorption as the PES membrane and similar levels of FB adsorption as the PVDF membrane. In the case of adsorption from the protein mixture, a suppression of HSA adsorption and replacement of HSA with FB were observed. Consequently, the initial solution with a HSA content of 92% resulted in an adsorbed layer containing approximately 75–80% HSA across all the studied membranes. TRF adsorption remained unaffected by the presence of other proteins, consistent across all three membranes. Notably, the PES membrane exhibited the most significant change in the adsorbed protein composition between single-protein and multi-protein adsorption. In addition, this study comprehensively assesses the impact of fibrinogen adsorption on dialysis, including its consequences, blood activation, and implications for quality of life.

Seeing the Membrane from Both Sides Now: Lipid Asymmetry and Its Strange Consequences.

Almost all biomembranes are constructed as lipid bilayers and, in almost all of these, the two opposing monolayers (leaflets) have distinct lipid compositions. This lipid asymmetry arises through the concerted action of a suite of energy-dependent enzymes that maintain living bilayers in a far-from-equilibrium steady-state. Recent discoveries reveal that lipid compositional asymmetry imparts biophysical asymmetries and that this dualistic organization may have major consequences for cellular physiology. Importantly, while transbilayer asymmetry appears to be an essential, near-ubiquitous characteristic of biological membranes, it has been challenging to reproduce in reconstituted or synthetic systems. Although recent methodological developments have overcome some critical challenges, it remains difficult to extrapolate results from available models to biological systems. Concurrently, there are few experimental approaches for targeted, controlled manipulation of lipid asymmetry in living cells. Thus, the biophysical and functional consequences of membrane asymmetry remain almost wholly unexplored. This perspective summarizes the current state of knowledge and highlights emerging themes that are beginning to make inroads into the fundamental question of why life tends toward asymmetry in its bilayers.

Fabrication and modification of PVDF membrane by PDA@ZnO for enhancing hydrophilic and antifouling property

There is an urgent need for an antifouling membrane to treat the large volume of dye-containing wastewater generated annually by the dyeing and printing industry. PDA@ZnO/PVDF membranes were synthesized by doping polydopamine (PDA) and zinc oxide (ZnO) nanoparticles into the polyvinylidene fluoride (PVDF) membranes via non-solvent induced phase separation (NIPS) method in which polyvinylpyrrolidone (PVP) and lithium chloride (LiCl) were chosen as the porogens respectively. Their microstructures were characterized, and the membranes were examined for antifouling properties and membrane separation performance. The presence of PDA@ZnO nanoparticles on the PVDF membrane was evidenced by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) measurements. The addition of PDA@ZnO enhanced the mechanical strength and hydrophilicity of the nanocomposite membranes. The PVDF membranes' water permeability and antifouling properties improved following mixing modification, according to the dye filtration test. The pure water flux of PDA@ZnO/PVDF hybrid membranes changed from 260.0 L·m−2·h−1·bar−1 to 1339.2 L·m−2·h−1·bar−1 by varying the concentration of PDA@ZnO nanoparticles from 0 wt% to 1.6 wt%. The retention performance of the modified membranes was shown to be significantly superior to the pure PVDF membrane. The modified membranes with the addition of 2.0 wt% PVP and 1.6 wt% PDA@ZnO nanoparticles had highly disperse blue 79 (DB 79) retentions (88.5%), indicating that the modified membrane possessed the characteristics of a promising membrane for the purification of dye. Tests found that PDA@ZnO significantly improved the membrane's antifouling performance.

Anion-Exchange Membrane “Polikon A” Based on Polyester Fiber Fabric (Functionalized by Low-Temperature High-Frequency Plasma) with Oxidized Metal Nanoparticles

An experimental laboratory set of samples of composite heterogeneous anion-exchange membranes was obtained by us for the development of our original method of polycondensation filling. Anion-exchange membranes were prepared on plasma-treated and non-plasma-treated polyester fiber fabrics. The fabric was treated with low-temperature argon plasma at a power of 400 W for 10 min at a pressure of 5 × 10−5 mbar. On the surface and bulk of the polyester fiber, a polyfunctional anionite of mixed basicity was synthesized and formed. The anion-exchange membrane contained secondary and tertiary amino groups and quaternary ammonium groups, which were obtained from polyethylene polyamines and epichlorohydrins. At the stage of the chemical synthesis of the anion matrix, oxidized nanoparticles (~1.5 wt.%) of silicon, nickel, and iron were added to the monomerization composition. The use of ion-plasma processing of fibers in combination with the introduction of oxidized nanoparticles at the synthesis stage makes it possible to influence the speed and depth of the synthesis and curing processes; this changes the formation of the surface morphology and the internal structure of the ion-exchange polymer matrix, as well as the hydrophobic/hydrophilic balance and—as a result—the different operational characteristics of anion-exchange membranes.

Nanomorphogenesis of template-induced crumpled polyamide nanofiltration membranes

Tailored thin-film composite (TFC) nanofiltration (NF) membranes can potentially achieve high permeance and effective salt separation during wastewater reclamation and water reuse. Recently, customized polyamide (PA) nanofilms with crumpled structures have received considerable attention owing to their outstanding separation performance; however, the underlying mechanism of the formation of crumpled features at the nanoscale remains poorly understood. Herein, we report the use of a particulate polydopamine (PDA) interlayer as a regulator for modulating chemical inhomogeneity (i.e., the diffusion and distribution of amine monomers) during the interfacial polymerization (IP) process, in which the characteristic spatial patterns of PA nanostructures are formed following a diffusion–reaction dynamics model in the Turing theory. Furthermore, the nanomorphologies and separation performance of PA membranes can be effectively controlled by tuning the physical inhomogeneity (i.e., the roughness of the organic–aqueous reaction interface) of the particulate interlayer. The interlayer-mediated TFC NF membrane exhibits crumpled nanosized stripes with three times higher permeance and four times higher Cl−/SO42− selectivity (up to 82.1) than those of pristine PA membranes. We have also identified an array of topographical parameters for both the PDA interlayer and PA nanostructures based on experimental observations and multiscale simulations (i.e., molecular dynamics and dissipative particle dynamics) to establish quantitative relationships between the interlayer morphology, PA morphology, and performance characteristics of NF membranes. Our work provides molecular insights into the nanomorphogenesis of crumpled PA nanofilms and interlayer effects on the IP reaction and final separation performance.

Graphene-based stand-alone nanomechanical membrane production and mass-acoustic hybrid-sensor application

In this article, experimental studies were carried out for the preparation, characterization, and nanomechanical membrane application of Graphene-based nanomechanical mass and acoustic hybrid sensors. The purpose of this study was to prepare facile and low-cost nanomechanical membrane-based mass-acoustic hybrid sensors by set-ups developed on the exfoliation and membrane transfer methods, and to examine their morphological, spectroscopical, and nanomechanical-vibrational properties, as well as the membrane characteristics like mass and acoustic sensitivities and durability over time. For the experiments, equipment and items such as optical, digital, atomic force and scanning electron microscopes, Raman spectroscope, acoustic signal source and amplifier, data-logger, sound pressure level meter, and laser Doppler vibrometer were used. Graphene-based nanomechanical membrane sensor chips with varying acoustic pressure levels and mass-loadings were tested. It was observed that the acoustic sensitivity of the produced 706.5 µm2 nanomechanical membranes increased with increasing sound pressure levels and decreased with increasing mass-loads. With 67.8 ± 5 nm/Pa, the unloaded nanomechanical membrane was the most sensitive sample. Experimental challenges and sensor development solutions were discussed. Existing application examples were examined and discussions were made on the current challenges and the future prospects of the nanomechanical membrane sensors.

Selectivity and permeability of gas separation in SILMs: Effect of collapsed structure

In this work, the influence of the intramembrane structure of SILMs on gas separation was demonstrated by molecular dynamics simulations. The five morphological characteristics of separation membranes bring different separation effects. For the selection process, interfacial characteristics have a significant effect on the selectivity by the analysis of density and energy barrier. The difference in the blocking effect on CO2 is the key to the separation. For the permeation process, the analysis of free volume and interaction energy revealed that the residence time and penetration of gas molecules in membranes are sensitive to distribution characteristics of ionic liquids. Lastly, the interaction energy and pressure difference were analyzed to reveal the influence of the membrane structure on the persistence of separation and flow interruption. This work can provide theoretical support for the high efficiency control of membrane separation and the development of two-dimensional membrane materials.

Study of the Thermochemical Effect on the Transport and Structural Characteristics of Heterogeneous Ion-Exchange Membranes by Combining the Cell Model and the Fine-Porous Membrane Model.

For the first time, based on the joint application of the fine-porous and cell models, a theoretical analysis of the changing transport and structural characteristics of heterogeneous polymeric ion-exchange membranes (IEMs) MK-40, MA-40, and MA-41 after exposure to elevated temperatures in water and aggressive media (H2SO4 and NaOH solutions), as well as after long-term processing in electrodialyzers of various types, was carried out. The studied membranes are composites of ion-exchange polymers with polyethylene and nylon reinforcing mesh. The external influences provoke the aging of IEMs and the deterioration of their characteristics. The transport properties of IEMs are quantitatively described using five physicochemical parameters: counterion diffusion and equilibrium distribution coefficients in the membrane, characteristic exchange capacity, which depends on the microporosity of ion-exchanger particles, and macroscopic porosity at a known exchange capacity of IEMs. Calculations of the physicochemical parameters of the membranes were performed according to a specially developed fitting technique using the experimental concentration dependences of integral diffusion permeability and specific electrical conductivity, and their model analogs. This made it possible to identify and evaluate changes in the membrane micro- and macrostructure and examine the process of artificial aging of the IEM polymer material due to the abovementioned external impacts.

Proof of concept of using a membrane-sensing peptide for sEVs affinity-based isolation.

Introduction: One main limitation in biomarker studies using EVs is the lack of a suitable isolation method rendering high yield and purity samples in a quick and easily standardized procedure. Here we report an affinity isolation method with a membrane-sensing peptide (MSP) derived from bradykinin. Methods: We designed a protocol based on agarose beads carrying cation chelates to specifically bind to the 6His-tagged membrane-sensing peptide. This approach presents several advantages: 1) cation-carrying agaroses are widely used and standardized for His-tagged protein isolation, 2) the affinity protocol can be performed in small volumes, feasible and manageable for clinical routine and 3) elution with imidazole or EDTA allows a gentle and easy recovery without EV damage, facilitating subsequent characterization and functional analyses. Results: The optimized final procedure incubates 0.5mg of peptide for 10min with 10µL of Long-arm Cobalt agarose before an overnight incubation with concentrated cell conditioned medium. EV downstream analyses can be directly performed on the agarose beads adding lysis or nucleic-acid extraction buffers, or gently eluted with imidazole or EDTA, rendering a fully competent EV preparation. Discussion: This new isolation methodology is based on the recognition of general membrane characteristics independent of surface markers. It is thus unbiased and can be used in any species EV sample, even in samples from animal or plant species against which no suitable antibodies exist. Being an affinity method, the sample handling protocol is very simple, less time-consuming, does not require specialized equipment and can be easily introduced in a clinical automated routine. We demonstrated the high purity and yield of the method in comparison with other commercially available kits. This method can also be scale up or down, with the possibility of analyzing very low amounts of sample, and it is compatible with any downstream analyses thanks to the gentle elution procedure.

Biophysical Properties of Lipid Membranes from Barley Roots during Low-Temperature Exposure and Recovery.

Glycerolipid remodeling, a dynamic mechanism for plant subsistence under cold stress, has been posited to affect the biophysical properties of cell membranes. In barley roots, remodeling has been observed to take place upon exposure to chilling stress and to be partially reverted during stress relief. In this study, we explored the biophysical characteristics of membranes formed with lipids extracted from barley roots subjected to chilling stress, or during a subsequent short- or long-term recovery. Our aim was to determine to what extent barley roots were able to offset the adverse effects of temperature on their cell membranes. For this purpose, we analyzed the response of the probe Laurdan inserted in bilayers of different extracts, the zeta potential of liposomes, and the behavior of Langmuir monolayers upon compression. We found important changes in the order of water molecules, which is in agreement with the changes in the unsaturation index of lipids due to remodeling. Regarding Langmuir monolayers, we found that films from all the extracts showed a reorganization at a surface pressure that depends on temperature. This reorganization occurred with an increase in entropy for extracts from control plants and without entropy changes for extracts from acclimated plants. In summary, some membrane properties were recovered after the stress, while others were not, suggesting that the membrane biophysical properties play a role in the mechanism of plant acclimation to chilling. These findings contribute to our understanding of the impact of lipid remodeling on biophysical modifications in plant roots.