Myelin sheaths are the differentiated membrane assemblies in the central and peripheral nervous systems (CNS; PNS) that wrap nerve fibers in a jelly-roll-like arrangement. The regular organization along fibers of these electrically-insulating, multilamellar, lipid-rich sheaths is responsible for the rapid conduction of electrical signals from one node of Ranvier to the next node. The...
The Alzheimer’s disease (AD) is a devastating neurodegenerative disease caused by the formation of senile plaques, primarily consisting of Amyloid-beta peptides. The crucial role in this process at its pre-clinical stage is likely imparted by peptide-membrane interactions [1], though the further details are yet to be understood. Our recent experimental data for example revealed several...
Small membrane lipid domains are important in cell signaling. We investigate modulation of lipid domains by volatile anesthetics. Many volatile compounds produce anesthesia. With no molecular target identified, mechanisms remain puzzling. Large membrane concentrations (~100 mM) are required to produce anesthesia. Hyperbaric pressures (~100 bar) reverse anesthesia.
Using neutron/x-ray...
Plant cell membranes glycerolipids can be classified in two groups: phospholipids containing phosphate, mainly synthesized in the endoplasmic reticulum (ER), and glycolipids – galactolipids and sulfolipids - without phosphate, synthesized in chloroplasts, and being the major constituents of photosynthetic membranes. When plants are deprived of phosphate, a frequent natural situation that...
Life places extreme demands on the material properties of the membranes that surrounds cells. These thin bilayers must be both rigid enough to define the cell structure yet flexible enough to undergo dramatic changes in cell shape in processes like endocytosis and cell division. In turn, the properties of the biomembranes are determined by the unique characteristics of the thousands of...
Curved cell membranes are important for the function of the cell, both for compartmentalization in organelles within the cell as well as for cellular mitosis. It has also been shown that the curvature of a lipid membrane can affect the concentration of membrane bound proteins. In this project we have used semiconductor nanowires to study the effect of curvature on phospholipid bilayers and...
DNA origami is emerged as a powerful and versatile method to fabricate highly controllable 3-dimensional structures at the nanometer-scale. One example of those powerful DNA nanostructures is a membrane-spanning DNA channel, which exhibited the ability to mimic the biological channels in transporting of ions and biomolecules across the lipid membrane (Burns et...
The skin barrier function is primarily located in the outermost layer of the skin, the stratum corneum (SC) and is comprised of corneocytes (dead cells) and intercellular lipids. The main lipid classes in the SC are ceramides, free fatty acids, and cholesterol. These lipids form two crystalline lamellar phases, with a repeat distance of 13 nm and 6 nm, respectively. The composition and...
Membranes exhibit thermal fluctuations, but transmembrane protein activity breaks the fluctuation-dissipation theorem leading to out-of-equilibrium fluctuations. Active fluctuations have been widely described theoretically [1], but to a lesser extent experimentally.
We will present our recent results on the investigation of out-of-equilibrium fluctuations of phospholipid membranes induced by...
Deuteration is a useful strategy to modulate the visibility of specific components of the sample using neutron scattering techniques as it offers increased contrast with no significant impact on the physico-chemistry of the membrane. In this context, mass production of biologically relevant deuterated phospholipids of varying head groups and acyl chain compositions is currently the limiting...
Mixtures of the phospholipid 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and the saponin beta-aescin spontaneously form monodisperse, bilayered discoidal micelles (also known as "bicelles" or "nanodisks") in aqueous solution. Such bicelles form below the melting temperature of DMPC when the phospholipids are in the rigid state and are precursors of spontaneously formed vesicles. The...
We are presenting transmission electron microscopy (TEM) imaging as an advanced tool for characterization freestanding crystalline metalorganic networks (MONs) [1]. As an example of creation of ultrathin material, the two-dimensional (2D) layer of the monomolecular thickness amphiphilic derivatives of calix[4]arenes are selected [1, 2]. The methyl-carboxy-functionalized calix[4]arenes can...
The cell membrane is a universal component found in both prokaryotic and eukaryotic cells, which is composed mainly of a series of lipid mixtures that act as a physical barrier against various pathogens, in addition to other functions that remain unknown. There is a large difference in the lipid composition of bacterial and mammalians cytoplasmic membranes, a fact that can be used to obtain...
Lipids are found widely in biological systems because of their unique interfacial properties. They are the primary component of cell membranes, which act as barriers containing the contents of the cells and protecting them from external threats. In fulfilling their function, the lipid membranes are exposed to oxidation processes that change their molecular structure. Such processes occur...
The current tree of life is divided into three domains: Bacteria, Eukarya and Archaea. While bacterial and eukaryotic lipids are constituted of sn-3 glycerol on which straight fatty acids are ester-bound, archaeal lipids contain ramified isoprenoid hydrocarbons that are linked through ether bounds on a sn-1 glycerol. As a results, plasma membranes are spatially organized into domains of...
Fundamental understanding of the solubilisation process in self-assembly systems is important for many applications including membrane solubilization and protein extraction. The kinetic processes involved in mixtures of surfactants and block copolymer micelles are not well understood. However, it is commonly known that surfactants exhibit rather fast equilibration kinetics, in the order of...
Antimicrobial peptides (AMPs) are found in nature to selectively kill microbes by disrupting their cell membranes. Because of the rapid physical action, pathogens are less likely to develop the relative resistance mechanism to the AMPs. Therefore, AMPs are the potential candidates for the multiple-drug resistance (MDR) treatments. We have designed a series of surfactant-like AMPs based on the...
In humans, dihydroorotate dehydrogenase (DHODH) is an flavoprotein found in the inner mitochondrial membrane (IMM). DHODH catalyzes the oxidation of dihydroorotic acid with the concomitant reduction of ubiquinone Q10 (coenzyme Q10), thus acting as a link between the de novo pyrimidine biosynthesis and the mitochondrial respiratory chain. DHODH is a well validated target for immunosuppressive...
A central event in pathogenesis of Alzhaimer’s diseases are thought to be intracellular and extracellular accumulation, aggregation and misfolding of low molecular mass peptides such as β-amyloid (Aβ1-42), tau protein (Tau) and s100A9 [1,2, 6]. Small size aggregates-oligomers were found to be extremely neurotoxic in vitro and in vivo with the ability to disrupt the major neuron membranes...
Using elementary building blocks to mimic and reconstruct biological structures is intriguing both from fundamental aspects, providing a simple model to study a complex environment, as well as from the applicative point of view, opening the possibility of utilizing such constructs for the creation of new functional materials. Understanding the key parameters governing the interaction between...
Surfactant N,N-dimethyl-1-dodecanamine-N-oxide (DDAO) possess a wide range of biological effects (antimicrobial, phytotoxic, antiphotosynthetic, immunomodulatory). Interaction of non-ionic form of DDAO with DOPC and DOPC-CHOL (CHOL:DOPC =0.5:1 mol/mol) model membranes was studied by SANS. Unilamellar liposomes were prepared by extrusion in PBS buffer. Aggregation of DOPC and DOPC-CHOL...
Due to alarming increase in the number of cases of antibiotic-resistant bacterial infections, it is necessary to develop new antibiotics, explore relationships between structure and observed effect and study the mechanism of antimicrobial action. Amphipathic antimicrobial peptides are perspective compounds which display antimicrobial effects. Dermaseptins represent a large group of cationic...
Membrane protein solubilization implies the use of amphipathic detergents that form protective belts around hydrophobic patches to maintain the protein’s structural integrity outside of the lipid environment. Consequently, the resulting SANS signal includes both protein and detergent belt signatures leading to a global outer shell larger than the envelope expected for the protein alone;...
The location of n-decane molecules within the model biological membrane consisting of dioleoyl-phosphocholine (DOPC) bilayers has been investigated via small angle neutron diffraction (SAND) method. Diffraction patterns of the samples containing varied amounts of labeled and unlabeled n-decane have been obtained at various H2O:D2O scattering contrasts and utilized in the reconstruction of...
Metallacarboranes are a unique class of inorganic polyhedral clusters containing carbon, boron, hydrogen, and metal atoms. A typical metallacarborane is the nanometric size anion [COSAN]-: a Co3+ metal ion sandwiched between two [C2B9H11]2− (dicarbollide) clusters. In the last ten years we have shown that COSAN and its derivatives have all the properties of classical surfactants (surface...
Cationic lipids are widely used in modern drug delivery systems such as lipid nano-particles (LNPs). These drug carriers are multi-component systems (containing novel cationic lipids, cholesterol, phospholipids, siRNA/mRNA) with strognly pH-dependent structures, which are poorly characterized. Earlier experimental methods could provide the information about optimal sizes of LNPs, but their...
Lipid bilayers are self-assembling structures constituting the membranes of every animal cell and many others cell-derived nanoparticles like Extracellular vesicles (EVs). EVs are vesicles with dimensions ranging from 50 to 500nm produced and released by cells to act as cargoes for biological material (proteins, nucleic acids) which play a pivotal role in intercellular communication and in...
Developments in the field of X-ray diffraction, such as XFEL (X-ray Free Electron Laser) has become advantageous in studying Membrane Protein’s structure and dynamics. For in-vitro studies, membrane protein needs to be reconstituted in a more native like hydrophobic environment. A novel membrane model system, Nanodisc due to its defined size and low mass-ratio of lipid to protein, proves to...
The study of active membrane proteins requires an environment which is as close as possible to their natural environment to retain protein function, while at the same time keeping the system as simple as possible to allow for an experimental characterization and to be able to identify factors which influence the system. Tethered lipid bilayers (tBLMs) represent an experimentally accessible and...
Deuteration is a useful strategy to modulate the visibility of specific components of the sample using neutron scattering techniques as it offers increased contrast with no significant impact on the physico-chemistry of the membrane. In this context, mass production of biologically relevant deuterated phospholipids of varying head groups and acyl chain compositions is currently the limiting...
PolyElectrolyte-Surfactant Complexes (PESCs) are interesting colloidal systems characterized by a complex, mesoscopically ordered inter- and intra-particle structure. Depending on their composition such assemblies are often sensitive to environmental stimuli, e.g. T and pH. One building block of such a potentially functional material can be the naturally derived polycation chitosan and the...
Supported lipid bilayers (SLBs) are often used for investigation in biophysics. They can be a good model system because it is not difficult to compose them at different scales of complexity. In fact, by using mixtures of lipids, or the addition of other proteins, the interactions between those bilayer components can be investigated. Alternatively, polymers can be attached to a defined...
Phosphate starvation is a frequent nutrient stress encountered by plants to which they adapt by exerting different mechanisms. The partial degradation of phospholipids, a common constituent of cellular membranes, is a widespread response observed in plants to increase the intracellular phosphate availability. To maintain membrane integrity, the degraded phospholipids have to be replaced by a...
Polymers with balanced hydrophilicity can translocate through biological membranes without doing damage. In the case of synthetic polymers there are only few reports of translocation using charged polymers [1-2]. For non-charged polymers translocation phenomena were predicted theoretically [3] but not verified experimentally.
We have synthesized such balanced, alternating...
It has been known for a long time that adsorbed bilayers of n-alkyl trimethylammonium bromide surfactants, CnTAB, at aqueous solution/hydrophilic solid interfaces are thin, much less than two extended hydrocarbon chains. These materials are bactericidal but the mechanism is not well-understood although differences in behaviour with chain length are established. For these reasons...
Histatin 5 (Hst5) is a histidine-rich, 24 amino acid protein, classified as an intrinsically disordered protein (IDP). It is a cationic salivary protein found to play a crucial role in fungicidal activity, and its activity to inhibit the growth and viability of Candida albicans has been evaluated using a variety of techniques. The underlying mechanism is however not very well known. The aim of...
Pulmonary surfactant consists on an adsorbed phospholipid-based monolayer at the alveolar air-liquid interface connected to a membrane reservoir placed in the aqueous subphase. Its main function is to minimize the surface tension stabilizing the mammalian respiratory surface, enabling breathing dynamics and preventing alveolar collapse during expiration. Pulmonary surfactant is mainly composed...
G-protein coupled receptors (GPCRs) are a large receptor protein family that sense molecules outside the cell and activate intracellular signal transduction pathways and modulate cellular responses. Since they are activated by extracellular stimuli of varied size and nature such as light, odors, hormones, and neurotransmitters, these receptors are extremely important therapeutic targets. Over...
New therapeutic modalities, such as RNA-based drugs, have shown promising results in treating diseases that are currently difficult to tackle with standard small molecule drugs. One type of RNA therapeutic, mRNA, is especially promising due to its ability to induce protein production in target cells, where it can replace damaged or missing proteins. However, clinical progress is often limited...
Lipid bilayers and lipid-associated proteins play a crucial role in biology. Since studies and manipulation in vivo are inherently challenging, several in vitro membrane-mimetic systems have been developed to enable the study of lipidic phases, lipid-protein interactions and membrane protein function. Controlling the size and shape or introducing functional elements in a programmable way is,...
Bacterial resistance is presently a major public health concern, due to excessive and misuse of antibiotics. This has stressed the research on new antibiotics with new mechanisms of action [1]. Antimicrobial peptides are part of our innate immune system and represent a new antibiotic paradigm, as they aim the bacterial membrane, have been studied in the past decade [2]. Within this research...
Biological membranes often contain considerable amounts of glycolipids or membrane-anchored polysaccharides. Both can strongly influence the membrane characteristics in terms of their interactions with ions [1] and molecular components of the aqueous medium [2], their interactions with adjacent membranes [2, 3], and their in-plane organization [1], among others. We use various scattering...
In Gram negative bacteria, the inner membrane is suspended from a thin peptidoglycan layer and contains embedded membrane proteins. This composite layer controls the shape of the cell and the flux of materials into and out of the cell. Mechanosensitive ion channels act as safety valves, protecting bacteria from osmotic shock, by opening when the membrane is subject to a stress. In addition to...
Mucus is a highly viscoelastic secretion, covering the epithelia surfaces of the gastrointestinal, pulmonary, oral, nasal and genital tracts. Its function and composition differs at different locations of our body, but the general task of mucus is to protect mucosal tissues from dehydration, mechanical stress, and to act as barrier against microorganisms and toxic substances. Mucus is mainly...
Oxidation of membrane lipids in biology is a very important field because it may impact ageing, cell apoptosis and cancer[1]. It is unclear what the chemical identity of the oxidant is and there is plenty of discussion in the literature. Consequently, the term ROS (reactive oxygen species) is invoked and that may include the oxidants OH, O$_2$($^1\Delta_g$), HO$_2$, O$_2^-$ etc. Studies of the...
The increasing emergence of resistant bacteria is a great concern in terms of public health as available conventional antibiotics drugs are not able to kill them. One strategy proposed is the use of bacterial membranes as a therapeutic target so that their basic properties are perturbed, altering the membrane potential and inhibiting the control functions on the signalling, communication or...
Lipid asymmetry is a hallmark of biological membranes [1]. In particular, prototypical mammalian plasma membranes are known to be composed of an outer leaflet enriched in cholinephospholipids, while the majority of the aminophospholipids are confined to the inner leaflet [2]. Asymmetric large unilamellar lipid vesicles (aLUVs), produced via cyclodextrin-mediated lipid exchange [3], are a new...
Over the past few years, our lab has put forth an effort to measure the rate and energetics of the diffusion of cholesterol and lipids. Using small angle neutron scattering (SANS), we found that the diffusion rate of cholesterol was much slower (hundreds of minutes) rather than the accepted value of under a second. Our group’s work showed that the discrepancy was likely due to artifacts...
Non-lamellar lipid aqueous phases, such as reverse cubic or hexagonal phases, can be used to entrap smaller biomolecules. The curvature of the lipid aqueous interfaces in these phases and hence the size of the aqueous cavities depends on the composition, water content and temperature. Normally the size of the cavities is similar or smaller than biomacromolecules, such as large enzymes. This...
The rise of antimicrobial resistance is a major challenge for future healthcare needs. To date antibiotic resistant bacterial strains have been reported in every country with prevalence growing annually. One promising line of treatment is antimicrobial peptides (AMPs), small cationic peptides, similar to the innate antimicrobial peptide defense in humans. It has been shown that AMPs can be...
It is generally believed that antimicrobial peptides, AMPs, are able to evade much of the bacterial resistance because they disturb the fundamental integrity of the entire cell by interfering with the life-defining cell membrane. However, there is no clear general consensus for the molecular basis by which AMPs act, although various structural modifications such as membrane deformation or pore...
The metabolism of fats including lipids and cholesterol involves the production, in the liver, of lipid carrying particles known as lipoproteins. Lipoproteins are nanoemulsion-like particles composed of fats and proteins (named apolipoproteins). The complexity of lipoproteins is great, with different compositions not only in terms of the amounts of the fat and proteic components, but also on...
Pulmonary surfactant (PS) is a mixture of lipids (~90 %) and 8-10 % specific surfactant associated proteins. PS lines the interior of the lung alveoli and acts to lower interfacial tension. The absence of PS due to prematurity, or its damage, is treated by exogeneous PS in neonatal medicine. Curosurf (Cur) is one such clinically used replacement surfactants. It is an extract of porcine lung...
Photosynthetic membranes, also called thylakoids, have a unique and unusual lipid composition. They contain an extremely high amount of unique classes of glycolipids, constituted of galactolipids, i.e. mono- and digalactosyldiacylglycerol (MGDG and DGDG) and of a sulfolipid, i.e. sulfoquinovosediacylglycerol (SQDG). A remarkable feature of the evolution from cyanobacteria to higher plants is...
The existence and role of lateral lipid organization in biological membranes has been studied and contested for more than 30 years. Lateral lipid domains, or rafts, are hypothesized as scalable compartments within biological membranes, providing appropriate physical environments to their resident membrane proteins. This implies that lateral lipid organization is associated with a range of...
Most of Earth’s biotopes are hold under extreme environmental conditions, namely distant from the optimal life conditions of humans. Nevertheless, a large biological diversity of organisms inhabit such environments, i.e. extremophiles. For instance, many living organisms reside at hydrothermal sources of deep oceans: temperatures above 100°C, high concentrations of reduced metals, absence of...
Given the probable extremely contrasted environmental conditions at the origins of life (high temperature, pressure and pH), the origin and nature of the first cell membranes is still an open question. Due to complex organic carbon limitations, the first membranes were most likely composed of simpler, single chain fatty acids [1], which raises questions as how they could withstand the very...
The development of stimuli-sensitive, particularly pH-sensitive, liposomal nanocontainers for targeted drug delivery is of great value nowadays. The pH-sensitivity of liposomes can be achieved by embedding the pH-switcher into the lipid bilayer, thus the decrease of the pH value would result in release of the entrapped compound.
In this study we examined the pH-dependent kinetics of changes in...
The early impairments appearing in Alzheimer's disease are related to neuronal membrane damage. Both,aberrant A$\beta$ species and specific membrane components play a role in promoting aggregation, deposition and signal dysfunction. Ganglioside GM1, present with cholesterol and sphingomyelin in lipid rafts, seems to be able to initiate A$\beta$ aggregation on membrane [1]. In general,...
Styrene-maleic acid lipid particles (SMALPs) are self-assembled discoidal structures composed of a polymer belt and a segment of lipid bilayer, which are capable of encapsulating membrane proteins directly from the cell membrane. In recent years a number of different nanodisc forming polymers with varying properties have been developed and characterised. For example, Styrene-maleic imide lipid...
Amphiphilic copolymers enable a fundamentally new approach for investigating membrane proteins, as they obviate the use of conventional detergents. These polymers extract proteins and surrounding lipids directly from cellular membranes to form nanosized discs, where the polymer wraps around a lipid-bilayer patch. Such nanodiscs are amenable to a broad range of methods requiring nanosized...
There are numerous techniques able to gauge diffusion in biomembranes. For instance, quasi-elastic neutron scattering measures diffusion in a non-perturbative manner over nanosecond time scales, yet sampling is space is here done over large distances. Meanwhile, single-particle tracking allows one to track the dynamics of individual molecules in almost nanometer resolution, but these...
