Changes In Membrane Structure Research Articles

Investigation of diabetes-related molecular changes in embryo-endometrium crosstalk

The primary aim of this study was to explore the impact of diabetes on matrix metalloproteases and tissue inhibitors, crucial factors for successful implantation, and to elucidate the molecular mechanisms that undergo changes in the endometrium and the embryo during diabetic pregnancies. In this investigation, we established a streptozotocin-induced diabetic pregnant rat model. Microarray analysis followed by RT-PCR was utilized to identify gene regions exhibiting expression alterations. Subsequently, we assessed the effects of MMPs and tissue inhibitors using ELISA and immunohistochemistry techniques, in addition to analyzing changes at the genetic level. Diabetes led to the upregulation of MMP3, MMP9, and MMP20 on the 6.5th day of pregnancy, while causing the downregulation of MMP3, MMP9, and MMP11 on the 8.5th day of pregnancy. TIMP1 expression was downregulated on the 8.5th day compared to the control group. No statistically significant differences were observed between the groups regarding other TIMP expressions. KEGG pathway analysis revealed that diabetes induced alterations in the expression of genes associated with certain microRNAs, as well as signaling pathways such as cAMP, calcium, BMP, p53, MAPK, PI3K-Akt, Jak-STAT, Hippo, Wnt, and TNF. Additionally, gene ontology analysis unveiled changes in membrane structures, extracellular matrix, signaling pathways, ion binding, protein binding, cell adhesion molecule binding, and receptor-ligand activity. This study serves as a valuable guide for investigating the mechanisms responsible for complications in diabetic pregnancies. By revealing the early-stage effects of diabetes, it offers insight into the development of new diagnostic and treatment approaches, ultimately contributing to improved patient care.

Pervaporation Membranes Based on Polyelectrolyte Complex of Sodium Alginate/Polyethyleneimine Modified with Graphene Oxide for Ethanol Dehydration.

Pervaporation is considered the most promising technology for dehydration of bioalcohols, attracting increasing attention as a renewable energy source. In this regard, the development of stable and effective membranes is required. In this study, highly efficient membranes for the enhanced pervaporation dehydration of ethanol were developed by modification of sodium alginate (SA) with a polyethylenimine (PEI) forming polyelectrolyte complex (PEC) and graphene oxide (GO). The effect of modifications with GO or/and PEI on the structure, physicochemical, and transport characteristics of dense membranes was studied. The formation of a PEC by ionic cross-linking and its interaction with GO led to changes in membrane structure, confirmed by spectroscopic and microscopic methods. The physicochemical properties of membranes were investigated by a thermogravimetric analysis, a differential scanning calorimetry, and measurements of contact angles. The theoretical consideration using computational methods showed favorable hydrogen bonding interactions between GO, PEI, and water, which caused improved membrane performance. To increase permeability, supported membranes without treatment and cross-linked were developed by the deposition of a thin dense layer from the optimal PEC/GO (2.5%) composite onto a developed porous substrate from polyacrylonitrile. The cross-linked supported membrane demonstrated more than two times increased permeation flux, higher selectivity (above 99.7 wt.% water in the permeate) and stability for separating diluted mixtures compared to the dense pristine SA membrane.

Protopanaxadiol Targeting Membrane Induces HepG2 Cell Apoptosis Via Raft-like Formation and Tubulation Disruption.

Protopanaxadiol (PPD), which has a molecular structure similar to cholesterol, is a potent anticancer agent that has been proposed to target the lipid membrane for the pharmacological effects. However, the underlying mechanism by which PPD modulates the cell membrane leading to cancer cell death is not be fully understood. In this work, we used single cell infrared spectroscopy, scanning electron microscopy and confocal microscopy to investigate the effects of PPD on human hepatocellular carcinoma (HepG2) cells, focusing on the change in membrane structure. We found that PPD significantly reduced the number of membrane tubules over the course of treatment. Interestingly, the addition of PPD could promote the formation of lipid raft-like domains (PPD rafts) and even restore the domain disruption caused by methyl-beta-cyclodextrin depletion of membrane cholesterol. In addition, PPD pre-treatment may increase the induction effect of FasL, which impairs cell viability, although it does not appear to be beneficial for Fas clustering in the PPD rafts. Collectively, these results highlight a non-classical mechanism by which PPD induces HepG2 apoptosis by directly affecting the physical properties of the cell membrane, providing a novel insight into understanding membrane-targeted therapy.

Enhanced Separation Performance of Graphene Oxide Membrane through Modification with Graphitic Carbon Nitride

The treatment of tritiated nuclear wastewater is facing greater challenges with the continuous expansion of the nuclear industry. The key to solving the issue of detritium in low-abundance tritium water lies in developing highly efficient and cost-effective hydrogen isotope separation technology. Graphene oxide (GO) membrane separation method exhibits greater potential compared to other existing energy-intensive technologies for the challenging task of hydrogen isotope separation in nuclear wastewater. In recent years, researchers have explored few strategies to enhance the performance of graphene oxide (GO) membranes in hydrogen isotope water treatment, recognizing the current limitations in separation efficiency. In this study, the GO/g-C3N4 composite membrane has been successfully employed for the first time in the separation of hydrogen isotopes in water. A series of GO membranes were prepared and their performances were tested by a self-made experimental device. As a result, the separation performance of the GO membrane was enhanced by the modification with graphitic carbon nitride (g-C3N4). The permeation rate of the GO/g-C3N4 membrane was higher than that of the GO membrane, while maintaining a high separation factor. Our study also demonstrated that this phenomenon can be attributed to the changes in membrane structure at the microscopic scale. The H/D separation factor and the permeate flux of the composite membrane containing g-C3N4 of 6.7% by mass were 1.10 and 7.2 × 10−5 g·min−1·cm−2 are both higher than that of the GO membrane under the same experimental conditions, which is promising for the isotope treatment.

Modulation of Phospholipase A2 Membrane Activity by Anti-inflammatory Drugs.

The phospholipase A2 (PLA2) superfamily consists of lipolytic enzymes that hydrolyze specific cell membrane phospholipids and have long been considered a central hub of biosynthetic pathways, where their lipid metabolites exert a variety of physiological roles. A misregulated PLA2 activity is associated with mainly inflammatory-derived pathologies and thus has shown relevant therapeutic potential. Many natural and synthetic anti-inflammatory drugs (AIDs) have been proposed as direct modulators of PLA2 activity. However, despite the specific chemical properties that these drugs share in common, little is known about the indirect modulation able to finely tune membrane structural changes at the precise lipid-binding site. Here, we use a novel experimental strategy based on differential scanning calorimetry to systematically study the structural properties of lipid membrane systems during PLA2 cleavage and under the influence of several AIDs. For a better understanding of the AIDs-membrane interaction, we present a comprehensive and comparative set of molecular dynamics (MD) simulations. Our thermodynamic results clearly demonstrate that PLA2 cleavage is hindered by those AIDs that significantly reduce the lipid membrane cooperativity, while the rest of the AIDs oppositely tend to catalyze PLA2 activity to different extents. On the other hand, our MD simulations support experimental results by providing atomistic details on the binding, insertion, and dynamics of each AID on a pure lipid system; the drug efficacy to impact membrane cooperativity is related to the lipid order perturbation. This work suggests a membrane-based mechanism of action for diverse AIDs against PLA2 activity and provides relevant clues that must be considered in its modulation.

Effect of citric acid on cell membrane structure and function of Issatchenkia terricola WJL-G4.

This study aimed to investigate the changes of cell membrane structure and function of Issatchenkia terricola under citric acid by performing physiological analysis. The membrane integrity, surface hydrophobicity, structure, fluidity, apoptosis, and fatty acid methyl esters composition of I. terricola WJL-G4 cells were determined by propidium iodide staining, microbial adhesion to hydrocarbon test, transmission electron microscopy analysis, fluorescence anisotropy, flow cytometry, and gas chromatography-mass, respectively. The results showed that with the increasing of citric acid concentrations, the cell vitality, membrane integrity, and fluidity of I. terricola reduced; meanwhile, apoptosis rate, membrane permeable, hydrophobicity, and ergosterol contents augmented significantly. Compared to control, the activities of Na+, K+-ATPase, and Ca2+, Mg2+-ATPase increased by 3.73-fold and 6.70-fold, respectively, when citric acid concentration increased to 20g l-1. The cells cracked and their cytoplasm effused when the citric acid concentration reached 80g l-1. I. terricola could successfully adjust its membrane structure and function below 60g l-1 of citric acid. However, for citric acid concentrations above 80g l-1, its structure and function were dramatically changed, which might result in reduced functionality.

DP1, a multifaceted synthetic peptide: Mechanism of action, activity and clinical potential

AimsMicrobial infections remain a leading cause of mortality worldwide, with Staphylococcus aureus (S. aureus) being a prominent etiological agent, responsible for causing persistent bacterial infections in humans. It is a nosocomial, opportunistic pathogen, capable to propagate within the bloodstream and withstand therapeutic interventions. In the current study, a novel, indigenously designed synthetic antimicrobial peptide (sAMP) has been evaluated for its antimicrobial potential to inhibit the growth and proliferation of S. aureus. Main methodsThe sAMP, designed peptide (DP1) was evaluated for its minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against a panel of pathogenic bacterial strains. Membrane mechanistic studies were performed by measuring membrane conductivity via dielectric spectroscopy and visualizing changes in bacterial membrane structure through field emission scanning electron microscopy (FE-SEM). Further, DP1 was tested for its in vivo antimicrobial potential in an S. aureus-induced systemic infection model. Key findingsThe results indicated that DP1 has the potential to inhibit the growth and proliferation of a broad spectrum of Gram-positive, Gram-negative and multidrug-resistant (MDR) bacterial strains. Strong bactericidal effect attributed to change in electrical conductivity of the bacterial cells leading to membrane disruption was observed through dielectric spectroscopy and FE-SEM micrographs. Further, in the in vivo murine systemic infection study, 50 % reduction in S. aureus bioburden was observed within 1 day of the administration of DP1. SignificanceThe results indicate that DP1 is a multifaceted peptide with potent bactericidal, antioxidant and therapeutic properties. It holds significance as a novel drug candidate to effectively combat S. aureus-mediated systemic infections.

Mechanistic insights into microwave-accelerated permeation through graphene-based membranes

Two-dimensional (2D) membranes, composed of stacked 2D nanomaterials, are increasingly utilized in separation fields due to their structured interlayer channels and ease of modification. The application of microwave technology to 2D membrane separation enhances permeability, but the unclear strengthening mechanism limits the further applications of this technique. This study aims to elucidate the fundamental principle behind microwave-accelerated permeability by investigating the performance of two distinct 2D membranes in response to microwaves: a microwave-transparent graphene oxide (GO) membrane and a microwave-absorbing GO-based membrane doped with molybdenum disulfide (MoS2-GO). Experimental results demonstrate that compared to conventional heating, microwave irradiation amplifies water and ethanol permeation flux through the GO membrane by 122% and 154%, respectively, without observed changes in membrane structure via SEM, XRD, and Raman analyses. In addition, the microwave accelerated permeation also occurs (by 110%) when Rhodamine B - aqueous solution was used as feed liquid, while the rejection rate was remained at above 99%, indicating the promising applications of microwave technology in sewage treatment. Further experiments show that the microwave-induced augmentation of water/ethanol permeation through the GO membrane was primarily governed by the dielectric loss values of the feed liquid. In contrast, this dependence vanished in the MoS2-GO membrane, indicating that accelerated permeation was mainly determined by the interaction between microwaves and diffusing molecules in the 2D channels, disrupted by microwave absorbing MoS2 in the latter case. These findings offer comprehensive insights into the enhancement of membrane permeation induced by microwave irradiation.

Dynamic modeling of chemical membrane degradation in polymer electrolyte membrane fuel cells: Effect of precipitated Pt particles

Chemical membrane degradation in polymer electrolyte membrane fuel cells operated under real conditions is often accompanied and affected by Pt catalyst degradation. This study investigates the effects of both artificially impregnated Pt particles and Pt migration on chemical membrane degradation are numerically investigated. For the first time, the impact of Pt migration is numerically analyzed. Membrane structural changes with coupled chemical membrane and Pt degradations are proposed. For Pt particles that are artificially impregnated in the membrane, yielding a Pt content of up to 50 mol% Pt, the membrane degrades at the fastest rate at moderate Pt contents (2 mol% Pt). The impregnated Pt particles promote the conversion of Fe3+ to Fe2+, which adversely impacts the membrane durability. The decrease in Pt content leads to reduction in both the Fe2+ conversion time and trend. In comparison, the naturally precipitated Pt particles in the membrane from the degraded Pt catalysts in the CL, have demonstrated a Pt content consistently lower than 2 mol% Pt. As a result, the chemical degradation rate of real fuel cells accelerates significantly with increasing Pt particle concentration. The chemical degradation rate increases with the gas solubility at the pore/electrolyte interface. With higher gas solubility, the peak location of chemical membrane degradation shifts from the anode side to the cathode side.

The intricate link between membrane lipid structure and composition and membrane structural properties in bacterial membranes.

It is now evident that the cell manipulates lipid composition to regulate different processes such as membrane protein insertion, assembly and function. Moreover, changes in membrane structure and properties, lipid homeostasis during growth and differentiation with associated changes in cell size and shape, and responses to external stress have been related to drug resistance across mammalian species and a range of microorganisms. While it is well known that the biomembrane is a fluid self-assembled nanostructure, the link between the lipid components and the structural properties of the lipid bilayer are not well understood. This perspective aims to address this topic with a view to a more detailed understanding of the factors that regulate bilayer structure and flexibility. We describe a selection of recent studies that address the dynamic nature of bacterial lipid diversity and membrane properties in response to stress conditions. This emerging area has important implications for a broad range of cellular processes and may open new avenues of drug design for selective cell targeting.

Molecular mechanism of calcitriol enhances membrane water permeability

Helicobacter pylori (H. pylori) exhibits a unique membrane lipid composition, including dimyristoyl phosphatidylethanolamine (DMPE) and cholesterol, unlike other Gram-negative bacteria. Calcitriol has antimicrobial activity against H. pylori, but cholesterol enhances antibiotics resistance in H. pylori. This study explored the changes in membrane structure and the molecular mechanisms of cholesterol/calcitriol translocation using well-tempered metadynamics (WT-MetaD) simulations and microsecond conventional molecular dynamics (CMD) simulations. Calcitriol facilitated water transport across the membrane, while cholesterol had the opposite effect. The differing effects might result from the tail 25-hydroxyl group and a wider range of orientations of calcitriol in the DMPE/dimyristoyl phosphatidylglycerol (DMPG) (3:1) membrane. Calcitriol moves across the bilayer center without changing its orientation along the membrane Z-axis, becomes parallel to the membrane surface at the membrane-water interface, and then rotates approximately 90° in this interface. The translocation mechanism of calcitriol is quite different from the flip-flop of cholesterol. Moreover, calcitriol crossed from one layer to another more easily than cholesterol, causing successive perturbations to the hydrophobic core and increasing water permeation. These results improve our understanding of the relationship between cholesterol/calcitriol concentrations and the lipid bilayer structure and the role of lipid composition in water permeation.

Probing the Onset of the Bacterial Membrane Photodamage in Time using a Raman Optical Tweezer

Laser-induced photo damage of the optically confined microorganism is known to affect the bacterial membrane. We record the Raman spectra of a live, optically trapped Bacillus subtilis at different trapping time lapses to determine the changes in the bacterial membrane, which in turn impacts the flagellar rotation. A 1064 nm tightly focused laser traps a single de-flagellated bacterium and Surface Enhanced Raman Scattering (SERS) signals are recorded with silver nanoparticles (AgNPs) inserted into bacteria via the internal colloid method. The internal colloid method, albeit resulting in a modest signal increase, is employed in preference here to prevent undesirable cell aggregation or instabilities in trapping or compromised cell integrity resulting from the conventional nanoparticle dressing of the cell membrane. The second derivative of the Raman spectrum reveals subtle changes in the molecular structure of the bacterial membrane manifested by shifts in the phospholipid peak (1462 cm−1), amide III peak (1245 cm−1) and cytosine peak (792 cm−1), with increased trapping duration. This is followed by a Principal Component Analysis (PCA) to examine the changes occurring in the Raman spectral range (600 cm−1–1800 cm−1). By comparing the spectral shifts at specific time lapses from the moment of trapping, with the diminishing frequency of rotation of the body and flagella of the trapped flagellated counterpart bacterium at these same time lapses, we establish a direct correlation between the changes in membrane structure and compromised rotation of the bacterium during photodamage. Our results confirm that the subtle changes that occur at the biomolecular level in a cell when subjected to photodamage can be identified with good sensitivity, and moreover, that the changes occurring at the biomembrane have a role to play in reduced rotation of the trapped bacterium during exposure to the laser.

Advances in the study of exosome-derived miRNAs in the pathogenesis, diagnosis, and treatment of systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is an inflammatory disease caused by autoantibodies, with high morbidity and mortality. It involves multiple systems, particularly the renal, which can lead to lupus nephritis (LN); its multi-system effects have a significant impact on the physical and mental health of patients. Exosomes are vesicles that are secreted during cell activity and carry a variety of nucleic acids, proteins, and lipids. They are distributed through body fluids for cellular communication. MicroRNAs (miRNAs) are nucleic acids that are packaged within the exosome that are taken up and released in response to changes in plasma membrane structure. MiRNAs are potential participants in immune and inflammatory responses, which are transported to target cells and can inhibit gene expression in receptor cells. It has been suggested that exosomal miRNA can regulate the pathogenesis of SLE and, as such, they are of value in diagnosis and treatment. In this paper, we focus on the research progress into exosomal miRNA in SLE and inspire new directions for SLE related research.

Bacteriophage steering of Burkholderia cenocepacia toward reduced virulence and increased antibiotic sensitivity.

Antibiotic resistance in bacteria is a growing global concern and has spurred increasing efforts to find alternative therapeutics, such as the use of bacterial viruses, or bacteriophages. One promising approach is to use phages that not only kill pathogenic bacteria but also select phage-resistant survivors that are newly sensitized to traditional antibiotics, in a process called "phage steering." Members of the bacterial genus Burkholderia, which includes various human pathogens, are highly resistant to most antimicrobial agents, including serum immune components, antimicrobial peptides, and polymixin-class antibiotics. However, the application of phages in combination with certain antibiotics can produce synergistic effects that more effectively kill pathogenic bacteria. Herein, we demonstrate that Burkholderia cenocepacia serum resistance is due to intact lipopolysaccharide (LPS) and membranes, and phage-induced resistance altering LPS structure can enhance bacterial sensitivity not only to immune components in serum but also to membrane-associated antibiotics such as colistin. IMPORTANCE Bacteria frequently encounter selection pressure from both antibiotics and lytic phages, but little is known about the interactions between antibiotics and phages. This study provides new insights into the evolutionary trade-offs between phage resistance and antibiotic sensitivity. The creation of phage resistance through changes in membrane structure or lipopolysaccharide composition can simultaneously be a major cause of antibiotic sensitivity. Our results provide evidence of synergistic therapeutic efficacy in phage-antibiotic interactions and have implications for the future clinical use of phage steering in phage therapy applications.

The influence of temperature on dynamic membrane structure

This study investigated the influence of cold source water temperature (0.3, 5 and 10 °C) on dynamic changes in membrane structure and the effectiveness of subsequent recovery treatment using warm water. The experimental results indicate that statistically significant shrinkage of membrane pores occurred under cold temperatures. After the exposure to cold temperatures for 24 h, a reduction in d50 (medium of membrane pores) by 25%, 20% and 11% compared to the virgin membranes (control) was observed at 0.3 °C, 5 °C and 10 °C, respectively. The change in membrane structure caused by cold source water could influence membrane plant performance.Warm water recovery treatment of membranes following exposure to cold temperatures was able to restore the membrane pores. Warm water at 35 °C could fully recover the shrunken pores to those of virgin membranes within 8 h, while the membrane pore sizes were not able to reach the original status even with prolonged treatment at room temperature.

Novel variant in CADM3 causes Charcot–Marie–Tooth disease

Abstract CADM3 has been recently reported causing a rare axonal Charcot–Marie–Tooth disease in three independent Caucasian families carrying a recurrent change. We describe the first alternative causative mutation in CADM3 in a family from black African and also observed de novo in a patient of Caucasian ancestry. The disease inheritance was consistent with autosomal dominant and sporadic patterns, respectively. Eight patients and their relatives were enroled from both families. The mean age at diagnosis was 33.9 years, and walking difficulty was commonly the first symptom. Neurological examination showed distal muscle weakness and atrophy, sensory loss and foot and hand deformities. A high clinical variability was noted, but as seen in CADM3-associated neuropathy, symptoms were more pronounced in the arms in some patients. Nerve conduction studies showed no response in most of the examined nerves, and an axonal type of neuropathy, where recorded. Whole exome sequencing revealed a novel missense variant (c.1102G>T; Gly368Cys) in CADM3, segregating with the disease. Functional analyses showed a significant decrease in CADM3-Gly368Cys protein levels in the membrane and major structural changes in its predicted secondary structure. Therefore, we extend the genotype spectrum of CADM3, underlining the need for genetic studies in underrepresented populations like in Africa.

Skin Extracellular Matrix Breakdown Following Paclitaxel Therapy in Patients with Chemotherapy-Induced Peripheral Neuropathy.

The chemotherapeutic agent paclitaxel causes peripheral neuropathy, a dose-limiting side effect, in up to 68% of cancer patients. In this study, we investigated the impact of paclitaxel therapy on the skin of breast cancer patients with chemotherapy-induced peripheral neuropathy (CIPN), building upon previous findings in zebrafish and rodents. Comprehensive assessments, including neurological examinations and quality of life questionnaires, were conducted, followed by intraepidermal nerve fiber (IENF) density evaluations using skin punch biopsies. Additionally, RNA sequencing, immunostaining for Matrix-Metalloproteinase 13 (MMP-13), and transmission electron microscopy provided insights into molecular and ultrastructural changes in this skin. The results showed no significant difference in IENF density between the control and CIPN patients despite the presence of patient-reported CIPN symptoms. Nevertheless, the RNA sequencing and immunostaining on the skin revealed significantly upregulated MMP-13, which is known to play a key role in CIPN caused by paclitaxel therapy. Additionally, various genes involved in the regulation of the extracellular matrix, microtubules, cell cycle, and nervous system were significantly and differentially expressed. An ultrastructural examination of the skin showed changes in collagen and basement membrane structures. These findings highlight the presence of CIPN in the absence of IENF density changes and support the role of skin remodeling as a major contributor to CIPN.

Interactions of Oleanolic Acid, Apigenin, Rutin, Resveratrol and Ferulic Acid with Phosphatidylcholine Lipid Membranes—A Spectroscopic and Machine Learning Study

Biologically active compounds present in the diet can interact with biological membranes (such as cell membranes), changing their properties. Their mutual interactions can influence their respective activities. In this study, we analyzed the interactions of oleanolic acid and phenolic compounds such as apigenin, rutin, resveratrol and ferulic acid with phosphatidylcholine membranes. Spectroscopic methods (fluorescence spectroscopy, dynamic light scattering) and machine learning were applied. The results of structural studies were compared with the antioxidant activity of the investigated substances in lipid membranes. In liposomes loaded with oleanolic acid, the pro-oxidant activity of resveratrol arises from changes in membrane structure, leading to an increased exposure of its hydrophilic region to external radicals. A similar mechanism may be involved in the pro-oxidant action of oleanolic acid. By contrast, apigenin, rutin and ferulic acid are present at the membrane surface. Their presence in this region protects the bilayer from radicals generated in the aqueous phase. Lower antioxidant activity observed in the case of ferulic aid is probably related to weaker interactions of this compound with the membrane, compared to the investigated flavonoids. Appropriate machine learning models for predicting oleanolic acid and phenolic compounds have been developed for the future application of intelligent predictive systems to optimizing manufacturing processes involving liposomes. The most effective regression model turned out to be the MLP 1:1-100-50-50-6:1, identifying resveratrol with a determination index of 0.83.

Effect of Hydroxyl-Containing Fragments on the Structure and Properties of Membrane-Forming Polyamide-Imides.

The structural features and thermophysical and transport properties of dense nonporous membranes of the casting type from (co)polyamide-imides synthesized by the polycondensation of the diacid chloride of 2-(4-carboxyphenyl)-1,3-dioxoisoindoline-5-carboxylic acid and diamines 5,5'-methylene-bis (2-aminophenol) (DADHyDPhM) and 4,4'-methylenebis(benzeneamine) (DADPhM), taken in molar ratios of 7:3, 1:1, and 3:7, have been studied. The effect of hydroxyl-containing modifying fragments of dihydroxy diphenylmethane introduced in various amounts into the main polymer chain on the pervaporation properties of the formed films is discussed. It has been shown that the presence of the residual solvent N-methyl-2-pyrrolidone in the films not only has a plasticizing effect on the characteristics of film membranes but also promotes the preferential transmembrane transport of polar liquids, primarily methanol (permeation rate over 2 kg for a copolymer with a ratio of DADHyDPhM:DADPhM = 7:3). The removal of the residual solvent from the polymer film, both thermally (heating to 200 °C) and by displacement with another solvent as a result of sequential pervaporation, led to a significant decrease in the rate of transfer of polar liquids and a decrease in the selectivity of the membrane. However, the dehydrocyclization reaction resulted in more brittle films with low permeability to penetrants of different polarities. The results of our comprehensive study made it possible to assume the decisive influence of structural changes in membranes occurring in connection with the competitive formation of intra- and intermolecular hydrogen bonds.

Amyloid Precursor Protein Changes Arrangement in a Membrane and Its Structure Depending on the Cholesterol Content.

One of the hallmarks of Alzheimer's disease (AD) is the accumulation of amyloid beta (Aβ) peptides in the brain. The processing of amyloid precursor protein (APP) into Aβ is dependent on the location of APP in the membrane, membrane lipid composition and, possibly, presence of lipid rafts. In this study, we used atomic force microscopy (AFM) to investigate the interaction between transmembrane fragment APP672-726 (corresponding to Aβ1-55) and its amyloidogenic mutant L723P with membranes combining liquid-ordered and liquid-disordered lipid phases. Our results demonstrated that most of the APP672-726 is located either in the liquid-disordered phase or at the boundary between ordered and disordered phases, and hardly ever in rafts. We did not notice any major changes in the domain structure induced by APP672-726. In membranes without cholesterol APP672-726, and especially its amyloidogenic mutant L723P formed annular structures and clusters rising above the membrane. Presence of cholesterol led to the appearance of concave membrane regions up to 2 nm in depth that were deeper for wild type APP672-726. Thus, membrane cholesterol regulates changes in membrane structure and permeability induced by APP that might be connected with further formation of membrane pores.