Herbal remedies containing root extracts of Panax ginseng are commonly used for complementary or alternative therapies. Ginsenosides, the major components of root extracts, are responsible for ginseng's pharmacological and biological effects; however, their mechanisms of action are unclear. We examined whether membrane cholesterol was involved in the mechanism of action ...

Sphingomyelins (SMs) and sterols are important constituents of the plasma membrane and have also been identified as major lipid components in membrane rafts. Using SM analogs with decreasing headgroup methylation, we systemically analyzed the effect of headgroup size on membrane properties and interactions with cholesterol. An increase in headgroup size ...

We report here our differential scanning calorimetry measurements investigating the thermotropic phase behaviour of binary dipalmitoylphosphatidylcholine (DPPC)/sterol mixtures containing two saturated sterols with different ring configurations (5β-H and either 3α-OH or 3β-OH). These measurements differ in the proportions of sharp and broad components in the heating endotherms, representing the melting ...

It is commonly believed that all membrane sterols are rigid all-trans ring systems with a fully extended alkyl side-chain and that they similarly influence phospholipid bilayer physical properties. Here, we report the sterol concentration-dependent, thermotropic phase behaviour of binary dipalmitoylphosphatidylcholine (DPPC)/sterol mixtures containing two similar 5α-H sterols with different functional ...

The high sterol concentration in eukaryotic cell membranes is thought to influence membrane properties such as permeability, fluidity and microdomain formation. Drosophila cannot synthesize sterols, but do require them for development. Does this simply reflect a requirement for sterols in steroid hormone biosynthesis, or is bulk membrane sterol also essential ...

Cholesterol is an essential and representative lipid in higher eukaryotic cellular membranes and is often found distributed nonrandomly in domains in biological membranes. A large body of literature exists on the organization of cholesterol in plasma membranes or membranes with high cholesterol content. However, very little is known about organization ...

Borrelia burgdorferi, the agent of Lyme disease, is unusual as it contains free cholesterol and cholesterol glycolipids. It is also susceptible to complement-independent bactericidal antibodies, such as CB2, a monoclonal IgG1 against outer surface protein B (OspB). We find that the bactericidal action of CB2 requires the presence of cholesterol glycolipids ...

Solid state NMR techniques have been used to investigate the effect that two serotonin receptor 1a agonists (quipazine and LY-165,163) have on the phase behavior of, and interactions within, cholesterol/phosphocholine lipid bilayers. The presence of agonist, and particularly LY-165,163, appears to widen the phase transitions, an effect that is much ...

This study focuses on the mechanism of interaction of sitamaquine with Leishmania donovani membranes, and its accumulation within the parasites. A biomimetic model of the outer layer of a Leishmania plasma membrane was used to examine the interactions of sitamaquine with lipids. The plasma membranes of L. donovani promastigotes were ...

We investigated the mobility and phase-partitioning of the fluorescent oxidized phospholipid analogue 1-palmitoyl-2-glutaroyl-sn-glycero-3-phospho-N-Alexa647-ethanolamine (PGPE-Alexa647) in supported lipid bilayers. Compared to the conventional phospholipid dihexadecanoylphosphoethanolamine (DHPE)-Bodipy we found consistently higher diffusion constants. The effect became dramatic when immobile obstacles were inserted into the bilayer, which essentially blocked the diffusion of DHPE-Bodipy ...

Annexin A6 (AnxA6) belongs to a conserved family of Ca(2+)-dependent membrane-binding proteins. Like other annexins, the function of AnxA6 is linked to its ability to bind phospholipids in cellular membranes in a dynamic and reversible fashion, in particular during the regulation of endocytic and exocytic pathways. High amounts of AnxA6 ...

The ligands of certain G-protein coupled receptors (GPCRs) are membrane soluble and reach their target from the lipid bilayer. Lipid composition and dynamics will therefore modulate the activity of these receptors, but specific roles of lipid components, including the ubiquitous cholesterol (Chol), are not clear. We have probed the organization ...

The studies on the influence of cholesterol on phospholipids accumulated in inner leaflet of membrane are performed rather rarely, especially in the presence of electrolytes, which are present in membrane environment. Therefore, in this work the interactions between cholesterol and saturated phosphatidylethanolamine (PE) and phosphatidylserine (PS) were studied in binary ...

7-Hydroperoxycholesterol is considered to be an intermediate compound of the cholesterol oxidation path as the first product formed when cholesterol is oxidized by triplet oxygen. However, there is a limitation on cholesterol mechanism studies because of the lack of 7-hydroperoxycholesterol analytical standard due to its low stability. To verify the ...

The interaction of beta-cyclodextrin (beta-CD) with mixed bilayers composed of sphingomylein and cholesterol (Chol) above and below the accepted stable complexation ratio (67:33) was investigated. Membranes with the same (symmetric) and different (asymmetric) compositions in their inner and outer leaflets were deposited at surface pressures of 20, 30, and 40 ...

Single-point fluorescence correlation spectroscopy (FCS) of membrane-bound molecules suffers from a number of limitations leading to inaccurate estimation of diffusion parameters. To overcome such problems and with the overall goal of addressing membrane heterogeneities, we performed z-scan FCS (zFCS) of the serotonin(1A) receptor. We analyzed the results according to FCS ...

Using neutron diffraction Harroun et al. [(2006) Biochemistry 45, 1227-1233; (2008) Biochemistry 47, 7090-7096] carried out studies that unequivocally demonstrated cholesterol preferentially sequestering in the middle of bilayers (i.e., flat orientation) made of lipids with polyunsaturated fatty acids (PUFA), in contrast to its "usual" position where its hydroxyl group locates ...

The nonsteroidal anti-inflammatory drug indomethacin exhibits diverse biological effects, many of which have no clear molecular mechanism. Membrane-bound receptors and enzymes are sensitive to their phospholipid microenvironment. Amphipathic indomethacin could therefore potentially modulate cell signaling by changing membrane properties. Here we examined the effect of indomethacin on membrane lateral heterogeneity. ...

A detailed and thorough characterization of nystatin-induced permeability on lipid bilayers of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)-containing ergosterol or cholesterol is presented. The results show that the same collection of transmembrane pores appears in membranes containing either sterol. The concentration range for the appearance of these pores is sterol-dependent. Another mechanism of action, ...

Pores formed by the polyene antibiotic nystatin were studied in solvent-free lipid membranes. The membranes were formed by the tip-dip technique using 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) with different mol fractions (0-50%) of cholesterol or ergosterol. The effects of the mol fraction of sterol and of temperature variation (15-35°C) on the activity of ...

Doping DMPC/DHPC bicelles with cholesterol sulfate broadens the temperature range over which stable alignment occurs, forming an aligned phase at lower temperatures even with high lipid concentrations. Cholesterol sulfate appears to combine the advantages of cholesterol with those of charged amphiphiles, stabilizing the aligned phase and preventing precipitation. This allows ...

Glycosphingolipids (GSLs) accumulate in cholesterol-enriched cell membrane domains and provide receptors for protein ligands. Lipid-based "aglycone" interactions can influence GSL carbohydrate epitope presentation. To evaluate this relationship, Verotoxin binding its receptor GSL, globotriaosyl ceramide (Gb(3)), was analyzed in simple GSL/cholesterol, detergent-resistant membrane vesicles by equilibrium density gradient centrifugation. Vesicles separated ...

Tissue-nonspecific alkaline phosphatase (TNAP), present on the surface of chondrocyte- and osteoblast-derived matrix vesicles (MVs), plays key enzymatic functions during endochondral ossification. Many studies have shown that MVs are enriched in TNAP and also in cholesterol compared to the plasma membrane. Here we have studied the influence of cholesterol on ...

The goal of the present study is to elucidate the effect of lipid domain formation on activities of Naja naja atra and Bungarus multicinctus phospholipase A(2) (PLA(2)) enzymes. Sphingomyelin inhibited enzymatic activity and membrane-damaging activity of PLA(2) against egg yolk phosphatidylcholine (EYPC), while cholesterol and cholesterol sulfate abrogated the inhibitory ...

A set of different biophysical approaches has been used to explore the phase behavior of palmitoylsphingomyelin (pSM)/cholesterol (Chol) model membranes in the presence and absence of palmitoylceramide (pCer). Fluorescence spectroscopy of di-4-ANEPPDHQ-stained pSM/Chol vesicles and atomic force microscopy of supported planar bilayers show gel L(beta)/liquid-ordered (L(o)) phase coexistence within the ...

Clearance of synaptically released dopamine is regulated by the plasmalemmal dopamine transporter (DAT), an integral membrane protein that resides within a complex lipid milieu. Here we demonstrate that cholesterol, a major component of the lipid bilayer, can modulate the conformation of DAT and alter cocaine binding to DAT. In striatal ...

Reported herein is a method that can be used to study the role of cholesterol in the microclustering of a ubiquitous class of membrane receptors, termed integrins. Integrin microclustering was measured using a fluorescence resonance energy transfer assay that does not require direct attachment of fluorescent donors or acceptors onto ...

Systems composed of a monoalkylated amphiphile and a sterol have been shown to form stable liquid-ordered (lo) lamellar phases; these include negatively charged mixtures of unprotonated palmitic acid/cholesterol (Chol) or cholesterol sulfate (Schol) and mixtures of positively charged cetylpyridinium chloride/Schol. Large unilamellar vesicles (LUVs) could be formed by these systems, ...

Experiments on frog neuromuscular preparations using electrophysiological (two-electrode voltage clamping) and optical (with the fluorescent endocytic stain FM1-43) methods were performed to study the importance of membrane cholesterol in the exo- and endocytic cycle of synaptic vesicles (SV) in motor nerve endings in conditions of prolonged rhythmic stimulation of the ...

Electron spin echo (ESE) study was performed for a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayer containing an admixture of lipids (of 1:100 molar ratio) spin-labeled at the polar head or at different positions along the acyl chain and optionally containing additionally cholesterol that substituted POPC lipids in a 50:50 molar ratio. ESE signal ...

We have created a stable bicelle system capable of forming micrometer-scale lipid domains that orient in a magnetic field, suitable for structural biology determination in solid-state NMR. The bicelles consisted of a mixture of cholesterol, saturated lipid (DMPC), and unsaturated lipid (POPC), a mixture commonly used to create domains in ...

The activity of phytosterols on human organism includes the ability of these compounds to incorporate into membranes. In the consequence the plant sterols are able to increase total sterol concentration in membrane or/and to replace cholesterol molecules. The aim of this work was to compare the influence of both these ...

Cholesterol is distributed unevenly between different cellular membrane compartments, and the cholesterol content increases from the inner bilayers toward the plasma membrane. It has been suggested that this cholesterol gradient is important in the sorting of transmembrane proteins. Cholesterol has also been to shown play an important role in lateral ...

Tethered bilayer lipid membranes (tBLM) are formed on 1) pure tether lipid triethyleneoxythiol cholesterol (EO(3)C) or on 2) mixed self-assembled monolayers (SAMs) of EO(3)C and 6-mercaptohexanol (6MH). While EO(3)C is required to form a tBLM with high resistivity, 6MH dilutes the cholesterol content in the lower leaflet of the bilayer ...

By employing poly(ethylene glycol) (PEG) shielding and a polymer cushion to achieve air stability of the lipid membrane, we have analyzed PEG influence on dried membranes and the interaction with cholesterol. Small unilamellar vesicles (SUVs) formed by the mixture of 1,2-dimyristoylphosphatidylcholine (DMPC) with different molar fraction of 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(poly(ethylene glycol))-2000] (DSPE-PEG(2000)) ...

Photodynamic therapy (PDT) is considered one efficient treatment against retinoblastoma. The specificity of a photosensitizer and its penetration into cancerous cells are crucial for achieving tumor necrosis. The selection of photosensitizers such as porphyrin derivatives by tumor cells thus depends to a large extent on their ability to interact with ...

A comparison of the molecular interaction of natural Scyphozoan lysins with their bioactivity in a haemolytic assay was performed by establishing an efficient, automatable and reproducible procedure for the measurement of protein-membrane interactions. The toxin-membrane interactions were analyzed utilising a chip-based technology with immobilized liposomes as artificial cell membranes. The ...

In the present series of papers, we describe the results of a systematic study on the anchoring of cholesterol-tagged oligonucleotides to phospholipids bilayers followed by membrane-assisted hybridization of the complementary strand in solution. This paper describes the anchoring of novel cholesterol-modified DNA-18mers in supported lipid bilayers (SLB) of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine: we ...

Oxidized analogs of cholesterol (oxysterols) are produced through both enzymatic and non-enzymatic pathways and have been shown to perturb membrane properties in vitro and in vivo. In the present study, the membrane behavior of two naturally occurring oxysterols, 25-hydroxycholesterol and 7-ketocholesterol, was examined in two model systems. The presence of ...

RATIONALE: Unrepaired cardiomyocyte membrane injury causes irreplaceable cell loss, leading to myocardial fibrosis and eventually heart failure. However, the cellular and molecular mechanisms of cardiac membrane repair are largely unknown. MG53, a newly identified striated muscle-specific protein, is involved in skeletal muscle membrane repair. But the role of MG53 in ...

Alkylphospholipid (APL) analogues constitute a new class of synthetic anti-tumour agents that act directly on cell membranes. We have previously demonstrated that hexadecylphosphocholine (HePC) alters intracellular cholesterol traffic and metabolism in HepG2 cells. We now extended our studies to analyse the effects of other clinically relevant APLs, such as edelfosine, ...

The present work was devoted to the exploration of the role of sterols in the functioning of membranes in root cells. Membrane characteristics and composition of the membrane lipids in the roots of wheat (Triticum aestivum L.) seedlings treated with exogenous cholesterol and antibiotic nystatin, which specifically binds with endogenous ...

Type II phosphatidylinositol 4-kinase IIalpha (PI4KIIalpha) is the dominant phosphatidylinositol kinase activity measured in mammalian cells and has important functions in intracellular vesicular trafficking. Recently PI4KIIalpha has been shown to have important roles in neuronal survival and tumorigenesis. This study focuses on the relationship between membrane cholesterol levels, phosphatidylinositol 4-phosphate ...

Cholesterol and sphingomyelin form together a highly ordered membrane phase, which is believed to play important biological functions in plasma membranes of mammalian cells. Since sphingomyelin is present mainly at the outer leaflet of cell membranes, monitoring its lipid order requires molecular probes capable to bind specifically at this leaflet ...

Lipid rafts are often considered as microdomains enriched in sphingomyelin and cholesterol, predominantly residing in the plasma membrane but which originate in earlier compartments of the cellular secretory pathway. Within this pathway, the membranes of the Golgi complex represent a transition stage between the cholesterol-poor membranes of the endoplasmic reticulum ...

We have studied the packing and collective dynamics of the phospholipid acyl chains in a model membrane composed of 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC) and cholesterol in varied phase state. After a structural characterization of this two-component model bilayer using X-ray reflectivity, we have carried out coherent inelastic neutron scattering to investigate the ...

In this study, we have examined the membrane properties and sterol interactions of phosphatidyl alcohols varying in the size of the alcohol head group coupled to the sn-3-linked phosphate. Phosphatidyl alcohols of interest were dipalmitoyl derivatives with methanol (DPPMe), ethanol (DPPEt), propanol (DPPPr), or butanol (DPPBu) head groups. The Phosphatidyl ...

We have used atomistic molecular dynamics simulations to consider 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescent probes in a fluid dipalmitoylphosphatidylcholine bilayer with 5 and 20 mol % cholesterol (CHOL). We show that while DPH affects a number of membrane properties, the perturbations induced by DPH depend on the concentration of cholesterol in a ...

We examined the effect of Niemann-Pick disease type 2 (NPC2) protein and some late endosomal lipids [sphingomyelin, ceramide and bis(monoacylglycero)phosphate (BMP)] on cholesterol transfer and membrane fusion. Of all lipid-binding proteins tested, only NPC2 transferred cholesterol at a substantial rate, with no transfer of ceramide, GM3, galactosylceramide, sulfatide, phosphatidylethanolamine, or ...

The effect of cholesterol on the formation and hydration behavior of solid-supported polysorbate 20 (Tween 20)/cholesterol self-assemblies was investigated by means of in situ energy-dispersive X-ray diffraction in a wide range of relative humidity (0.4 < RH < 1). At low hydration, Tween 20 and cholesterol were found to demix, ...