Interactions of Brominated Flame Retardants with Membrane Models of Dehalogenating Bacteria: Langmuir Monolayer and Grazing Incidence X-ray Diffraction Studies.

Brominated flame retardants (BFRs) are small organic molecules containing several bromine substituents added to plastics to limit their flammability. BFRs can constitute up to 30% of the weight of some plastics, which is why they are produced in large quantities. Along with plastic waste and microplastic particles, BFRs end up in the soil and can easily leach causing contamination. As polyhalogenated molecules, multiple BFRs were classified as persistent organic pollutants (POPs), meaning that their biodegradation in the soils is especially challenging. However, some anaerobic bacteria as Dehaloccocoides can dehalogenate BFRs, which is important in the bioremediation of contaminated soils. BFRs are hydrophobic, can accumulate in plasma membranes, and disturb their function. On the other hand, limited membrane accumulation is necessary for BFR dehalogenation. To study the BFR-membrane interaction, we created membrane models of soil dehalogenating bacteria and tested their interactions with seven legacy and novel BFRs most common in soils. Phospholipid Langmuir monolayers with appropriate composition were used as membrane models. These membranes were doped in the selected BFRs, and the incorporation of BFR molecules into the phospholipid matrix and also the effects of BFR presence on membrane physical properties and morphology were studied. It turned out that the seven BFRs differed significantly in their membrane affinity. For some, the incorporation was very limited, and others incorporated effectively and could affect membrane properties, while one of the tested molecules induced the formation of bilayer domains in the membranes. Thus, Langmuir monolayers can be effectively used for pretesting BFR membrane activity.

Organization of Carotenoid Aggregates in Membranes Studied Selectively using Resonance Raman Optical Activity.

In living organisms, carotenoids are incorporated in biomembranes, remarkably modulating their mechanical characteristics, fluidity, and permeability. Significant resonance enhancement of Raman optical activity (ROA) signals of carotenoid chiral aggregates makes resonance ROA (RROA), a highly selective tool to study exclusively carotenoid assemblies in model membranes. Hence, RROA is combined with electronic circular dichroism (ECD), dynamic light scattering (DLS), molecular dynamics, and quantum-chemical calculations to shed new light on the carotenoid aggregation in dipalmitoylphosphatidylcholine (DPPC) liposomes. Using representative members of the carotenoid family: apolar α-carotene and more polar fucoxanthin and zeaxanthin, the authors demonstrate that the stability of carotenoid aggregates is directly linked with their orientation in membranes and the monomer structures inside the assemblies. In particular, polyene chain distortion of α-carotene molecules is an important feature of J-aggregates that show increased orientational freedom and stability inside liposomes compared to H-assemblies of more polar xanthophylls. In light of these results, RROA emerges as a new tool to study active compounds and drugs embedded in membranes.

Study of the correlation between the structure of selected triester of phosphatidylcholine and their impact on physicochemical properties of model mammalian membranes.

Cationic lipids are synthetic compounds of amphiphilic character used in Drug Delivery Systems (DDS), especially in gene therapy, as the carriers of genetic material. As it is known, the main limitation of the application of cationic lipids in DDS is their high cytotoxicity after in vivo administration and low bioactivity. This is probably related to not fully known the relationship between the lipid structure and its activity as well as the mechanism of lipofection or drug delivery. Therefore, in this work we determined the impact of a selected group of cationic lipids - triesters of phosphatidylcholine (Et-PCs) - differing in their hydrophobic structure on model mammalian membranes. In the research, as model systems, Langmuir monolayers and liposomes were applied. It was shown that the incorporation of Et-PCs into model mammalian membranes weakens interactions between lipids, causing the increase of fluidity, disordering degree and permeability of membrane. The destabilization of the membrane in this way can facilitate the entry of drugs, carried inside cationic liposomes, into the pathological cell. Moreover, the studies prove that the structure of the hydrophobic part of cationic lipids also affects the properties of lipid membranes.

Persistent organic pollutants in model fungal membranes. Effects on the activity of phospholipases.

Soils are the final sink for multiple organic pollutants emitted to the environment. Some of these chemicals which are toxic, recalcitrant and can bioaccumulate in living organism and biomagnify in trophic chains are classified persistent organic pollutants (POP). Vast areas of arable land have been polluted by POPs and the only economically possible means of decontamination is bioremediation, that is the utilization of POP-degrading microbes. Especially useful can be non-ligninolytic fungi, as their fast-growing mycelia can reach POP molecules strongly bond to soil minerals or humus fraction inaccessible to bacteria. The mobilized POP molecules are incorporated into the fungal plasma membrane where their degradation begins. The presence of POP molecules in the membranes can change their physical properties and trigger toxic effects to the cell. To avoid these phenomena fungi can quickly remodel the phospholipid composition of their membrane with employing different phospholipases and acyltransferases. However, if the presence of POP downregulates the phospholipases, toxic effects and the final death of microbial cells are highly probable. In our studies we applied multicomponent Langmuir monolayers with their composition mimicking fungal plasma membranes and studied their interactions with two different microbial phospholipases: phospholipase C (α-toxin) and phospholipase A1 (Lecitase ultra). The model membranes were doped with selected POPs that are frequently found in contaminated soils. It turned out that most of the employed POPs do not downregulate considerably the activity of phospholipases, which is a good prognostics for the application of non-ligninolytic fungi in bioremediation.

Studies on the interactions of tiny amounts of common ionic surfactants with unsaturated phosphocholine lipid model membranes.

In order to provide the fundamental information about the interactions of common anionic surfactants with the basic unsaturated phospholipids the influence of three cationic (dodecyltrimethylammonium bromide, DTAB; tetradecyltrimethylammonium bromide, TTAB and hexadecyltrimethylamonium bromide, CTAB) and one anionic (sodium dodecylsulfate, SDS) surfactants on the properties of the 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine (POPC) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) layers was investigated. The studies proved that a tiny amount of the ionic surfactant added to the already synthesized liposome suspension is sufficient to change the zeta potential of the POPC and DOPC liposomes significantly. This impact increases with the surfactant concentration, the alkyl chain length of the surfactant and the degree of lipid saturation. Moreover, this effect is greater for the anionic surfactant than for the cationic one of the same alkyl chain length. The observed findings were confirmed in the course of the research carried out with the use of the corresponding Langmuir monolayers where the surface pressure - mean area isotherms, the compressibility modulus - surface pressure dependences, the monolayer penetration tests, the surface potential - mean molecular area isotherms and Brewster angle microscopy were discussed. It was found that the presence of the surfactants shifts the isotherms towards larger molecular area, to the higher extent for the SDS than DTAB. This effect increases with the increasing surfactant concentration in the subphase. Moreover, the investigated surfactants remain in the monolayer even at high surface pressure. Nevertheless, no effect on the morphology of the POPC and DOPC monolayers was detected from the BAM images. The surface potential and surface charge of the liposomes calculated on the basis of the zeta potential results reflected the interactions between the surfactant and the lipid layers.

The studies on the membrane activity of triester of phosphatidylcholine in artificial membrane systems.

Due to the increasing number of infections together with the appearance of bacteria exhibiting multi-drug resistance, new antibiotics are being sought. In this context the interest of the cationic lipoids increases because of their amphiphilic structure and positive charge that can stimulates the antibacterial action of these compounds. Thus, in this work we have performed the studies on the effect of one selected triesters of phosphatidylcholine, namely 1,2-dipalmitoyl-sn-glycero-3-ethylphosphocholine (EDPPC), on the model lipid membranes. The investigations included the analysis of the impact of EDPPC on multicomponent monolayers and bilayers consisting of the lipids naturally occurring in bacterial membranes (phosphatidylethanolamines (PE), phosphatidylglycerols (PG) and cardiolipin (CL)), mixed in proportions reflecting the lipid composition of these biomembranes. In the study, the Langmuir monolayers (registered on water and PBS buffer) and liposomes as model bacterial biomembranes were applied. The obtained results demonstrate that the presence of cationic lipoid in PE/PG and PE/PG/CL systems significantly modifies their properties and molecular organization. The incorporation of EDPPC into model bacterial membranes primarily impact on the intermolecular interactions. It was shown that the strength of the interaction between the cationic lipid and the components of the model membranes depends both on the composition of the membrane as well as on the type of subphase. Furthermore, the investigated cationic lipoid leads to the decrease of the ordering of acyl chains and thus to the increase of fluidity of membranes. The obtained results allow one to propose that EDPPC may behave as antibiotic active at the level of membrane.

Effect of trace amounts of ionic surfactants on the zeta potential of DPPC liposomes.

Surfactants are commonly found in today's world as an essential component of cleaning detergents, cosmetics and drug delivery systems. They can penetrate into lipid membranes, thus changing their properties. The aim of this paper is to compare the effect of addition of small amounts of cationic (DTAB) and anionic surfactants (SDS) with the same alkyl chain length on the zeta potential of DPPC liposomes with their influence on the corresponding DPPC monolayers. It was found that the addition of ionic surfactants with an initial concentration in the solution equal to 2.3, 4.5 and 9.1 µM to the liposome suspension changes their electrokinetic potential significantly. These changes increase with the increasing surfactant concentration and are greater for the anionic surfactant. This indicates the incorporation of surfactants into the structure of liposomes. Based on the analysis of π-area isotherms of DPPC monolayers it was proved that the ionic surfactant molecules are irreversibly integrated into the DPPC monolayer.

The composition of phospholipid model bacterial membranes determines their endurance to secretory phospholipase A2 attack - The role of cardiolipin.

Soil bacteria are decomposer organisms crucial for the biodegradation of organic pollutants, mineralization of dead organic matter and the turnover of biogenic elements. In their environment they are constantly exposed to membrane-lytic enzymes emitted to the soil by other microorganisms competing for the same niche. Therefore, the composition and structure of their membranes is of utmost importance for survival in the harsh environment. Although soil bacteria species can be Gram-negative or Gram-positive and their membranes differ significantly, they are formed by phospholipids belonging mainly to three classes: phosphatidylethanolamines (PE), phosphatidylglycerols (PG) and cardiolipins (CL). The correlation of the membrane phospholipid composition and its susceptibility to secretory membrane-lytic enzymes is widely unknown; thus, to shed light on these phenomena we applied the Langmuir monolayer technique to construct models of soil bacteria membranes differing in the mutual proportion of the main phospholipids. To characterize the systems we studied their elasticity, mesoscopic texture, 2D crystalline structure and discussed the thermodynamics of the interactions between their components. The model membranes were exposed to secretory phospholipase A2. It turned out that in spite of the structural similarities the model membranes differed significantly in their susceptibility to s-PLA2 attack. The membranes devoid of cardiolipin were completely degraded, whereas, these containing cardiolipin were much more resistant to the enzymatic hydrolysis. It also turned out that the sole presence of cardiolipin in the model membrane did not guarantee the membrane durability and that the interplay between cardiolipin and the zwitterionic phosphatidylethanolamine was here of crucial importance.

The role of phospholipid composition and ergosterol presence in the adaptation of fungal membranes to harsh environmental conditions-membrane modeling study.

Soil fungi play an important role in the environment decomposing dead organic matter and degrading persistent organic pollutants (POP). The presence of hydrophobic POP in the soil and membrane-lytic substances excreted by competing microorganism to the soil solution is the constant threat to these organisms. To survive in the harsh environment and counteract these hazards the fungal cells have to strictly control the composition of the lipids in their cellular membranes. However, in the case of fungal membranes the correlation between their composition and physical properties is not fully understood. In our studies we applied Langmuir monolayers formed by phospholipids typical to fungal membranes and ergosterol as versatile model membranes. These membranes were characterized by the Langmuir technique, Brewster Angle Microscopy and Grazing Incidence X-ray Diffraction, as well as were exposed to the action of phospholipase A2 treated as a model membrane-lytic protein. We started our studies from the equimolar mixture of phosphatidylethanolamine with phosphatidylcholine and doped this matrix with phosphatidylserine (PS) or phosphatidylinositol (PI). It turned out that the membranes with PS were much more condensed at the mesoscale and periodically organized at the molecular level. Starting from these models we derived two families of model fungal membranes adding to these phospholipid matrices ergosterol. It turned out that the level of ergosterol content is of crucial importance for the model membrane structure and its durability. Changing the ergosterol mole ratio from 0 to 0.5 we defined and described in detail four different 2D crystalline phases.

The influence of cationic lipoid - 1-palmitoyl-2-oleoyl-sn-glycero-3-ethylphosphocholine - on model lipid membranes.

The triesters of phosphatidylcholine as the derivatives of natural phosphatidylcholines are less cytotoxic than the other cationic lipoids, therefore they can be applied in lipofection and in drug delivery. However, a successful and effective use of these compounds requires detailed information of their mechanism of action, which is probably highly complex and multi-stages. However, the first barrier in the way to cell and thus the first side of action of these compounds is the cellular membrane. The aim of this work was to investigate the effect of one cationic lipoid, namely 1-palmitoyl-2-oleoyl-sn-glycero-3-ethylphosphocholine (EPOPC) on model POPC/SM/Chol = 1:1:1 membranes. The experiments were performed on monolayer and bilayer systems and they involved the surface pressure measurements, Brewster angle microscopy studies, dynamic light scattering and zeta potential measurements and the experiments with the surfactant solution and steady-state fluorescence anisotropy of DPH and TMA-DPH. Moreover, to perform the studies systematically also the properties of the binary (POPC/EPOPC, SM/EPOPC, Chol/EPOPC) and ternary (POPC/Chol/EPOPC, SM/Chol/EPOPC) model systems were investigated. The obtained results indicated that even low concentration of EPOPC alters properties and organization of model membranes. Namely, EPOPC makes the interactions in model membrane weaker and increases fluidity and permeability of the lipid system. Finally, based on these data it can be proposed that the mechanism of action of EPOPC in lipofection/drug delivery involves the modifications in membrane organization, which facilitates the incorporation of drug or other material into the cell.

Studies on the Interactions of 2-Hydroxyoleic Acid with Monolayers and Bilayers Containing Cationic Lipid: Searching for the Formulations for More Efficient Drug Delivery to Cancer Cells.

Drug delivery in cationic liposomes seems to be a promising therapeutic approach in cancer treatment. The rational design of the positively charged lipid vesicles as anticancer drug carriers should be supported by a detailed analysis of the interactions of the carrier components with anticancer drugs. In the present work, 2-hydroxyoleic acid (2OHOA; Minerval), a membrane lipid therapy drug, was incorporated into positively charged mono- and bilayer membranes containing 1-palmitoyl-2-oleoyl- sn-glycero-3-ethylphosphocholine (EPOPC), the synthetic cationic lipid, and 1,2-dioleoyl- sn-glycero-3-phosphocholine (DOPC). The intermolecular interactions, fluidity, and miscibility of the studied monolayers were analyzed by utilizing Langmuir balance experiments. The morphology of two-dimensional films was inspected using a Brewster angle microscopy technique. The properties of the liposomes were investigated by dynamic light scattering (DLS) and zeta potential measurements, steady-state fluorescence anisotropy experiments, and the spectrofluorimetric titration of calcein-encapsulated vesicles with a lysis-inducing agent. According to the collected results, 2OHOA intercalation into films of pure phospholipids or a binary EPOPC/DOPC film is thermodynamically favorable. Surprisingly, no significant effect of the presence of unsaturated 2OHOA chains on the EPOPC/DOPC monolayer order was observed. The experiments carried out for 2OHOA-inserted cationic EPOPC/DOPC (1:4) liposomes indicate effective incorporation of the drug into the liposome bilayer and the formation of stable vesicles without affecting their properties markedly. On the basis of the obtained results, EPOPC/DOPC/2OHOA cationic liposomes with 15% 2OHOA content in the phospholipid bilayer seem to be the most suitable for potential biomedical applications.

Complex Behavior of Phosphatidylcholine-Phosphatidic Acid Bilayers and Monolayers: Effect of Acyl Chain Unsaturation.

Phosphatidic acids (PAs) have many biological functions in biomembranes, e.g., they are involved in the proliferation, differentiation, and transformation of cells. Despite decades of research, the molecular understanding of how PAs affect the properties of biomembranes remains elusive. In this study, we explored the properties of lipid bilayers and monolayers composed of PAs and phosphatidylcholines (PCs) with various acyl chains. For this purpose, the Langmuir monolayer technique and atomistic molecular dynamics (MD) simulations were used to study the miscibility of PA and PC lipids and the molecular organization of mixed bilayers. The monolayer experiments demonstrated that the miscibility of membrane components strongly depends on the structure of the hydrocarbon chains and thus on the overall lipid shape. Interactions between PA and PC molecules vary from repulsive, for systems containing lipids with saturated and unsaturated acyl tails (strongly positive values of the excess free energy of mixing), to attractive, for systems in which all lipid tails are saturated (negative values of the excess free energy of mixing). The MD simulations provided atomistic insight into polar interactions (formation of hydrogen bonds and charge pairs) in PC-PA systems. H-bonding between PA monoanions and PCs in mixed bilayers is infrequent, and the lipid molecules interact mainly via electrostatic interactions. However, the number of charge pairs significantly decreases with the number of unsaturated lipid chains in the PA-PC system. The PA dianions weakly interact with the zwitterionic lipids, but their headgroups are more hydrated as compared to the monoanionic form. The acyl chains in all PC-PA bilayers are more ordered compared to single-component PC systems. In addition, depending on the combination of lipids, we observed a deeper location of the PA phosphate groups compared to the PC phosphate groups, which can alter the presentation of PAs for the peripheral membrane proteins, affecting their accessibility for binding.

The influence of terpinen-4-ol and eucalyptol - The essential oil components - on fungi and plant sterol monolayers.

Antifungal and herbicidal activity of terpenes, being the components of the essential oils, is directly related to the incorporation of these compounds into cellular membranes. Thus, the differences in the lipid composition of various pathogenic membranes may be the factor determining the activity of these molecules. One of the class of lipids, which form the membrane environment are sterols. The aim of this work was to compare the effect of two terpenes: terpinen-4-ol and eucalyptol on the monolayers formed by ergosterol and ß - sitosterol, which are the components of fungi and plant membranes, respectively. The modifications in the sterol monolayer properties were investigated in the surface pressure-area measurements and penetration studies as well as in a micrometer scale (Brewster angle microscopy experiments) and in nanoscale (GIXD technique). It was evidenced that although at higher surface pressure the terpene molecules are in part removed from the interface, they are able to substantially modify the condensation, morphology and molecular organization of the sterol film. It was also found that the incorporation of terpenes into sterol films is comparable for both sterols, however, ß - sitosterol monolayers properties are affected more strongly than ergosterol films. Finally, the analysis of the results of the studies performed on model membrane systems and the results of antimicrobial studies reported in literature, enabled us to suggest that the activity of terpenes depends on the membrane composition and that the sterol concentration may be important from the point of view of antifungal effect of terpinen-4-ol and eucalyptol.

The effect of chlorination degree and substitution pattern on the interactions of polychlorinated biphenyls with model bacterial membranes.

Polychlorinated biphenyls (PCB) are persistent organic pollutants that due to their chemical resistivity and inflammability found multiple applications. In spite of the global ban for PCB production, due to their long half-lives periods, PCB accumulate in the soils, so effective bioremediation of the polluted lands is of crucial importance. Some of the 209 PCB congeners exhibit increased toxicity to soil bacteria and their presence impoverish the soil decomposer community and slows down the degradation of environmental pollutants in the soils. The exact mechanism of PCB antimicrobial activity is unknown, but it is strictly related with the membrane activity of PCB. Therefore, to shed light on these interactions we applied Langmuir monolayers formed by selected phospholipids as model bacterial membranes. In our studies we tested 5 PCB congeners differing in the degree of chlorination and the distribution of the chlorine substituents around the biphenyl frame. Special attention was paid to tetra-substituted PCB because of their increased presence in the environment and disubstituted PCB being their degradation products. To characterize the model membranes as Langmuir monolayers, we used surface pressure measurements, Brewster angle microscopy and Grazing Incidence X-ray Diffraction. It turned out that among the tetra-substituted PCB the ortho-substituted non-dioxin like compound was much more membrane destructive than the flat dioxin-like congener. On the contrary, among the di-substituted PCB the flat para-substituted 2,2'-dichlorobiphenyl turned out to exhibit high membrane activity.

Effects of Polychlorinated Pesticides and Their Metabolites on Phospholipid Organization in Model Microbial Membranes.

Polychlorinated pesticides (PPs) were classified as persistent organic pollutants because of their toxicity, limited degradability in the environment, bioaugmentation, and accumulation in animal tissues. PPs accumulate in the environment mainly in the soils and water sediments where they are toxic to the decomposer organisms including soil bacteria and fungi. Therefore, there is an urgent need to search for the microorganisms capable of PP biodegradation which could be applied for soil bioremediation. The exact mechanism of PP microbial toxicity is unknown; however, there is evidence that it can be membrane related. To shed light on the interactions of PPs with microbial membranes, we applied Langmuir monolayers formed by phospholipids as model biomembranes. The model membranes were formed by phospholipids typical to microbial membranes: cardiolipins and phosphatidylglycerols the main components of Gram positive bacteria membranes, phosphatidylcholine typical to fungal membranes, as well as phosphatidylethanolamine found in the inner membranes of Gram negative bacteria. For the studies, the most ecotoxic PPs and their water-soluble metabolites were chosen. The monolayers were studied with the application of mutually complementary techniques: Langmuir technique, grazing incidence X-ray diffraction, and PM-IRRAS spectroscopy. It turned out that the cyclodiene PPs are more membrane active than monocyclic PPs and that the possibility of their incorporation is strictly related to the phospholipid structure. The membranes prepared with cardiolipin turned out to be especially resistant to PP incorporation. Regarding the metabolites, pentachlorophenol turned out to be especially structure breaking, affecting the molecular organization of all of the investigated phospholipids.

Effects of water soluble perfluorinated pollutants on phospholipids in model soil decomposer membranes.

Water soluble perfluorinated compounds (PFCs) as perfluorooctanesulfonate (PFOS), perfluorooctanoate (PFOA) and their shorter chain homologues are persistent organic pollutants widely distributed in the environment. PFCs accumulate in soils and sediments and because of their toxicity endanger the decomposer organisms. PFCs are toxic to a wide spectrum of soil bacteria and their biocide activity was related with their membrane activity; however, the exact mechanism of PFCs - bacterial membrane interactions is unknown. Therefore, to shed light on these questions we applied phospholipid Langmuir monolayers as simplified models of bacterial membranes and studied their interactions with selected environmentally relevant PFCs. The mechanical properties of the monolayers were characterized by surface pressure-mean molecular area isotherms and the analysis of compression modulus. The effects of PFC on the texture of the model membranes were studied with Brewster angle microscopy, whereas their influence on molecular packing in the 2D crystal lattice was searched by the Grazing Incidence X-ray diffraction technique. The effects of PFCs on the phospholipid polar heargroup conformation were studied by PM-IRRAS spectroscopy, whereas the effectivenes of the incorporation of PFCs into the model membrane was monitored in penetration tests. It turned out that the membranes rich in phosphatidylethanolamine typical to Gram negative bacteria are much PFCs susceptible than the cardiolipin rich membranes imitating Gram positive species. Moreover, the studies indicated that the switch from eight­carbon atom perfluorinated chains to shorter chain homologues is not necessarily environmentally benign as perfluorobutane sulfonate caused also significant structural changes in the model membranes.

Label-Free Infrared Spectroscopy and Imaging of Single Phospholipid Bilayers with Nanoscale Resolution.

Mid-infrared absorption spectroscopy has been used extensively to study the molecular properties of cell membranes and model systems. Most of these studies have been carried out on macroscopic samples or on samples a few micrometers in size, due to constraints on sensitivity and spatial resolution with conventional instruments that rely on far-field optics. Properties of membranes on the scale of nanometers, such as in-plane heterogeneity, have to date eluded investigation by this technique. In the present work, we demonstrate the capability to study single bilayers of phospholipids with near-field mid-infrared spectroscopy and imaging and achieve a spatial resolution of at least 40 nm, corresponding to a sample size of the order of a thousand molecules. The quality of the data and the observed spectral features are consistent with those reported from measurements of macroscopic samples and allow detailed analysis of molecular properties, including orientation and ordering of phospholipids. The work opens the way to the nanoscale characterization of the biological membranes for which phospholipid bilayers serve as a model.

Interactions of Long-Chain Perfluorotelomer Alcohol and Perfluorinated Hydrocarbons with Model Decomposer Membranes.

Perfluorinated hydrocarbons and their polar derivatives are produced annually in high quantities and find multiple industrial and technological applications due to their chemical and physical durability, significant hydro- and lipophobicity and excellent surface activity. Unfortunately, multiple perfluorinated compounds are recognized as persistent organic pollutants as they are completely nonbiodegradable and accumulate in soils and sediments. In our studies, we applied Langmuir monolayers formed by different structural phospholipids as models of soil bacteria and fungi membranes and investigated the effects exerted by long-chain perfluorinated pollutants, perfluorotelomer alcohol and two structurally different perfluorinated hydrocarbons, on the artificial membranes. Various mutually complemental methods such as surface pressure-mean molecular area isotherm registration, Brewster angle microscopy (BAM), and grazing incidence X-ray diffraction (GIXD) were applied. It turned out that the presence of the perfluorinated chemicals profoundly affected the phospholipid monolayers. The miscibility of the phospholipid with the perfluorotelomer alcohol depended strongly on the size and charge of the polar headgroup. Additionally, it was observed by BAM that the presence of the perfluorinated molecules significantly changed the texture of all the investigated phospholipid monolayers. On the basis of the BAM and GIXD results and other studies described in the scientific literature, we postulated that the perfluorinated hydrocarbons form an additional monolayer anchored on top of the phospholipid film. Our studies prove that both polar and nonpolar perfluorinated pollutants can be toxic to decomposer organisms and that their toxicity is strictly correlated with the phospholipid composition of the cellular membrane.

Studies on the interactions of anticancer drug - Minerval - with membrane lipids in binary and ternary Langmuir monolayers.

2-Hydroxyoleic acid (2OHOA, Minerval), a derivative of oleic acid, is the lipid used in Membrane Lipid Therapy. This compound is of confirmed anticancer effect, however its exact mechanism of action has not been fully elucidated. In this work the interactions of 2OHOA with cholesterol, sphingomyelin and phosphatidylcholine in Langmuir films were investigated. Moreover, the influence of this drug on SM/Chol and POPC/Chol films was studied. The collected results evidenced that 2OHOA substantially increases fluidity of lipid monolayers and modifies membrane organization, however, its influence depends on drug concentration and membrane properties. It was found that the condensation of model membrane is a critical factor determining the effect of 2OHOA. Moreover, the drug molecules added into SM/Chol film treated as model raft system drastically decrease molecular packing, weaken the interactions between raft components, destabilize the system and alter its morphology. This allows one to suggest that alterations made directly in membrane and microdomains architecture can be treated as one of the areas of Minerval activity.