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  • Physical states and thermodynamic properties of model Gram-negative bacterial inner membranes
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-12-06
    Javier Hoyo, Juan Torrent-Burgués, Tzanko Tzanov

    Novel antimicrobial agents are focused to interact with the bacterial membrane whose lipid composition (number and position of unsaturations and lipid headgroup) is adapted according to environmental signals. The anticipation of the adapted membrane properties is of high relevance to increase the targetability of such drugs. Herein, natural lipids extracted from Escherichia coli -phosphatidylethanolamine (PE), phosphatidylglycerol (PG) and cardiolipin (CL)- are used to form biomimetic membranes constituted by several PE:lipid ratios using the Langmuir and Langmuir-Blodgett techniques. The use of these techniques and the natural myriad of each lipid structures that constitute the biological E.coli membrane establishes a simple and reproducible model to evaluate the lipid-lipid interactions. PE and PG present similar shape and size, thus establish ideal and fluid -liquid expanded (LE) state - mixtures, whereas the differences between PE and CL motivate the formation of non-ideal and fluid (LE state) mixtures. The same physical state and the minor differences in elasticity (differences in the inverse of the compressibility modulus < 15 mN·m-1) between both systems regardless the PE content in the (PE:lipid) mixture suggest that the changes in the lipid composition influence the membrane proteins function rather than affecting the rigidity of the bacterial membrane.

    更新日期:2018-12-07
  • Cabazitaxel and Thymoquinone co-loaded Lipospheres as a Synergistic Combination for Breast Cancer
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-12-04
    Nagavendra Kommineni, Raju Saka, Upendra Bulbake, Wahid Khan

    Cabazitaxel as microtubule inhibitor and thymoquinone as HDAC inhibitor affects the important genes like p53, STAT3, Bax, BCL-2, p21 and down regulation of NF-κB are reported for potential activity against breast tumors. However, poor aqueous solubility and permeability hinders the delivery of these drugs to target site. To address the delivery challenges cabazitaxel and thymoquinone co-loaded lipospheres were developed. Lipospheres are the lipid based self-assemblies of particle size below 150 nm were prepared with more than 90% entrapment efficiency for both the drugs. In vitro drug release studies revealed there was a sustained diffusion controlled drug release from liposphere matrix leading to decrease in particle size with increase in zeta potential. Cytotoxicity studies on MCF-7 and MDA-MB-231 cells demonstrated cabazitaxel and thymoquinone as synergistic combination for the treatment of breast cancer which was proved by CompuSyn software. Enhanced efficacy of developed lipospheres can be due to rapid cellular internalization which was observed in confocal laser scanning microscopy. Drastic changes in cancer cell morphology such as nuclear fragmentation were observed upon treatment with these lipospheres in comparison to combination solution as observed in fluorescent imaging which are the hall marks of apoptosis. Cell cycle analysis and apoptosis studies confirmed the increased Sub G1 phase arrest as well as cell death due to apoptosis. Thus, as per observed results, it can be concluded that cabazitaxel and thymoquinone co-loaded lipospheres are the efficient delivery vehicles in management of breast cancer.

    更新日期:2018-12-04
  • Characterizing the structure of styrene-maleic acid copolymer-lipid nanoparticles (SMALPs) using RAFT polymerization for membrane protein spectroscopic studies
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-12-04
    Benjamin D. Harding, Gunjan Dixit, Kevin M. Burridge, Indra D. Sahu, Carole Dabney-Smith, Richard E. Edelmann, Dominik Konkolewicz, Gary A. Lorigan

    Membrane proteins play an important role in maintaining the structure and physiology of an organism. Despite their significance, spectroscopic studies involving membrane proteins remain challenging due to the difficulties in mimicking their native lipid bilayer environment. Membrane mimetic systems such as detergent micelles, liposomes, bicelles, nanodiscs, lipodisqs have improved the solubility and folding properties of the membrane proteins for structural studies, however, each mimetic system suffers from its own limitations. In this study, using three different lipid environments, vesicles were titrated with styrene-maleic acid (StMA) copolymer leading to a homogeneous SMALP system (~10 nm) at a weight ratio of 1:1.5 (vesicle: StMA solution). A combination of Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM) was used to characterize these SMALPs. We used a controlled synthesis mechanism to synthesize StMA based block copolymers called reversible addition-fragmentation chain transfer polymerization (RAFT) SMALPs. Incorporation of the Voltage sensor Domain of KCNQ1 (Q1-VSD) into RAFT SMALPs indicates that this is a promising application of this system to study membrane proteins using different biophysical techniques. V165C in Q1-VSD corresponding to the hydrophobic region was incorporated into the SMALP system. Continuous Wave-Electron Paramagnetic Resonance (CW-EPR) line shape analysis showed line shape broadening, exposing a lower rigid component and a faster component of the spin label.

    更新日期:2018-12-04
  • PEG-grafted phospholipids in vesicles: Effect of PEG chain length and concentration on mechanical properties
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-12-03
    Amit Mahendra, Honey Priya James, Sameer Jadhav

    Incorporation of low molecular weight poly-ethylene glycol (PEG) - grafted phospholipids in vesicle bilayers is known to increase the circulation time of liposomal drug delivery vehicles. Mechanical properties of giant unilamellar DPPC vesicles containing varying concentrations of DSPE-PEG (PEG MW: 550, 1000 and 2000) were measured by micropipette aspiration assay or osmotic swelling. While the area compressibility modulus did not change significantly, the bending modulus and water permeability of the bilayer was found to increase with increasing mole fraction of DSPE-PEG. This increase was more pronounced for higher molecular weight PEG. The measured bending modulus agreed with that predicted by scaling theory only at low mole fractions of DSPE-PEG. The water permeability was also measured as a function of the increase in area per lipid (due to steric repulsion between PEG chains), and for the same area per lipid, the PEG chain with MW 550 provided a greater resistance to water transport across the vesicle membrane compared to PEG 1000 and 2000. Lysis tension of the membrane, determined by osmotic lysis method at different loading rates showed a decrease in membrane strength on inclusion of the polymer lipid. These results suggest that liposome lifetime in the circulation and the rate of drug delivery are affected by the molecular weight and concentration of PEG in the bilayer.

    更新日期:2018-12-03
  • Research articleMolecular interactions and physico-chemical characterization of quercetin-loaded magnetoliposomes
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-11-30
    Sandra Cruz dos Santos, Nichole Osti Silva, João Batista dos Santos Espinelli, Marcelo Augusto Germani Marinho, Zeane Vieira Borges, Natália Bruzamarello Caon Branco, Fabrício Luiz Faita, Bruno Meira Soares, Ana Paula Horn, Alexandre Luís Parize, Vânia Rodrigues de Lima

    The bioflavonoid quercetin may prevent magnetoliposomes oxidation, preserving their stability. In this work, the interaction between quercetin and asolectin-based magnetoliposomes was investigated by monitoring the hydration degree, vibrational, rotational and translational mobility parameters of the system as well as its thermodynamic properties. The efficiency of the encapsulation of maghemite magnetic nanoparticles was detected by high resolution-continuum source flame atomic absorption spectrometry (HR-CS FAAS). The magnetic behavior of the system was studied by vibrating sample magnetometry (VSM) technique. The size and surface charge of magnetoliposomes were detected by dynamic light scattering (DLS) and zeta potential (ζ-potential) measurements. The influence of quercetin on the physico-chemical parameters of the magnetoliposomes was evaluated by Fourier transform infrared spectroscopy (FTIR), 31P and 1H nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSC) techniques. In vitro antioxidant and antitumoral assays were also performed for the magnetoliposomes. An insertion of quercetin into magnetoliposomes reduced the efficiency of the encapsulation of maghemite nanoparticles by 11%, suggesting a significant interaction between flavonoid and nanoparticles in a specific region of the system. Quercetin discreetly decreased the saturation magnetization of magnetoliposomes, but did not affect the superparamagnetic behavior of the system. 31P and 1H NMR results showed that quercetin did not alter the inverted hexagonal system phase state but decreased lipid polar head mobility. The flavonoid also seems to reorient the choline group above the bilayer phosphate membrane plane, as indicated by ζ-potential system values. FTIR, NMR and DSC responses showed that quercetin disordered the carbonyl and the methylene regions of the magnetoliposomes. Quercetin, as the nanoparticles, seems to be located in the polar head regions of magnetoliposomes, ordering it and diminishing the lipid intermolecular communication in the membrane carbonyl and non-polar regions. The lipid peroxidation of the magnetoliposomes was prevented 8-fold by the presence of quercetin in the system. Also, the flavonoid was responsible for a 45% reduction in the viability of glioma cells. Location and interactions between quercetin and magnetoliposomes components were discussed in order to be correlated with the results of biological activity, contributing to the design of more stable and efficient magnetoliposomes to be applied as contrast and antitumoral agents.

    更新日期:2018-12-01
  • Memtein: the fundamental unit of membrane:protein structure and function
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-11-30
    Michael Overduin, Mansoore Esmaili

    The concept of a memtein as the minimal unit of membrane function is proposed here, and refers to the complex of a membrane protein together with a continuous layer of biological lipid molecules. The elucidation of the atomic resolution structures and specific interactions within memteins remains technically challenging. Nonetheless, we argue that these entities are critical endpoints for the postgenomic era, being essential units of cellular function that mediate signal transduction and trafficking. Their biological mechanisms and molecular compositions can be resolved using native nanodiscs formed by poly(styrene-co-maleic acid) (SMA) copolymers. These amphipathic polymers rapidly and spontaneously fragment membranes into water-soluble discs holding a section of bilayer. This allows structures of complexes found in vivo to be prepared without resorting to synthetic detergents or artificial lipids. The ex situ structures of memteins can be resolved by methods including cryo-electron microscopy (cEM), X-ray crystallography (XRC), NMR spectroscopy and mass spectrometry (MS). Progress in the field demonstrates that memteins are better representations of how biology actually works in membranes than naked proteins devoid of lipid, spurring on further advances in polymer chemistry to resolve their details.

    更新日期:2018-12-01
  • A simple and convenient method for the hydrolysis of styrene-maleic anhydride copolymers to styrene-maleic acid copolymers
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-12-01
    Adrian H. Kopf, Martijn C. Koorengevel, Cornelis A. van Walree, Timothy R. Dafforn, J. Antoinette Killian

    Styrene-maleic acid (SMA) copolymers are increasingly gaining attention in the membrane protein field due to their ability to solubilize lipid membranes into discoidal nanoparticles. The copolymers are synthesized as styrene-maleic anhydride (SMAnh), and need to be converted to the free acid form (SMA) before they are capable of solubilizing membranes. This hydrolysis reaction is traditionally performed under rather cumbersome reflux conditions. Here we report an alternative method for the hydrolysis reaction using simple and readily available equipment found in virtually all biochemical laboratories, namely an autoclave. Based on the results we propose an optimum set of standard conditions for the hydrolysis reaction, that should make the method easily accessible to a wide scope of researchers.

    更新日期:2018-12-01
  • The interaction of lipid-liganded gold clusters (Aurora TM) with lipid bilayers
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-11-28
    Jesús Sot, Sebastião A. Mendanha-Neto, Jon V. Busto, Aritz B. García-Arribas, Shengrong Li, Stephen W. Burgess, Walt A. Shaw, David Gil-Carton, Félix M. Goñi, Alicia Alonso

    Lipid bilayers of different phospholipid compositions have been prepared, in the form of vesicles, or of supported lipid bilayers, and doped with AuroraTM at 0.1 mol%. AuroraTM consists of an Au55 gold nanoparticle (about 1.4 nm in diameter) capped with triphenylphosphine ligands and a single diglyceride (distearoyl glycerol) ligand. Gold nanoparticles have been incorporated in the past inside liposomes, or grafted onto their surfaces, with diagnostic or therapeutic aims. Including the gold nanoparticles in a stable form within the lipid bilayers has serious technical difficulties. We have tested the hypothesis that, because of the diglyceride ligand, AuroraTM would allow the easy incorporation of gold nanoclusters into cell membranes or lipid bilayers. Our results show that AuroraTM readily incorporates into lipid bilayers, particularly when they are in the fluid phase, i.e. the state in which cell membranes exist. Calorimetric, fluorescence polarization or fluorescence confocal microscopy concur in showing that bilayer-embedded AuroraTM hardly changes the physical properties of the bilayers, nor does it perturb the phase equilibrium in lipid mixtures giving rise to lateral phase separation in the plane of the membrane. Atomic force microscopy shows, in fluid bilayers, well-resolved particles, 1.2 – 2.9 nm in height, that are interpreted as single AuroraTM conjugates. Cryo-transmission electron microscopy allows the clear observation of lipid bilayers with an enhanced contrast due to the AuroraTM gold nanoparticles; the single particles can be resolved at high magnification. Our studies support the applicability of AuroraTM as a membrane-friendly form of nano-gold particles for biological research or clinical applications.

    更新日期:2018-11-28
  • “Rafts”: a nickname for putative transient nanodomains
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-11-23
    Félix M. Goñi

    The membrane raft hypothesis, proposed in 1997 by K. Simons and E. Ikonen, has played a paradoxical role in the history of biomembrane research. While it has generated a large amount of investigations, thus helping to increase our understanding of membranes, the object that gives name to the hypothesis, i.e. the raft itself, has been and still is an object of controversy, in which its very reality is often questioned. In this contribution I review the history of the hypothesis and its reception by membrane biologists, and summarize some of the valuable physico-chemical results that have been obtained while testing the raft hypothesis. To save a useful concept from its many misuses I propose that the expression “(transient) nanodomains” be employed instead of “rafts”.

    更新日期:2018-11-24
  • Calculating the ‘Chain Splay’ of Amphiphilic Molecules: Towards Quantifying the Molecular Shapes
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-11-23
    Chandrashekhar V. Kulkarni

    We report the first method to calculate a very important molecular level parameter of amphiphilic molecules– the ‘chain splay’. The calculations employed a truncated cone geometry, as it is the most probable configuration adopted by various amphiphiles. This approach utilized known parameters including lipid length, cross-sectional area at the head group and molecular volume. This new parameter, i.e. the area at the chain end, perceived to be more sensitive than Israelachvili’s famous shape factor or critical packing parameter (CPP). With relevant calculations, we demonstrate the fundamental roles of ‘chain splay’ to: a) reveal the critical contribution of molecular structure on average molecular shape and consequent self-assemblies, b) track the finest changes in molecular shapes within different bicontinuous cubic phases, c) obtain non-zero areas at the chain ends of amphiphiles that form normal (type 1) phases, d) back-calculate molecular volumes close to theoretical values, and e) find the link between molecular shapes and global curvatures of self-assemblies. This powerful feature advances our abilities towards quantitative estimation of spatial configurations adopted by amphiphilic molecules; moreover, it has a strong impact on predicting biomembrane structuring and nanoscale design of corresponding self-assemblies for a range of emerging applications.

    更新日期:2018-11-24
  • Visualizing Sphingolipid biosynthesis in cells
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-11-23
    Seetharaman Parashuraman, Giovanni D’Angelo

    Biosynthetic pathways play a fundamental role in the building and operation of the cell by synthesizing the constituents by which the cell is constructed, and by producing signalling intermediates that play a key role in cell regulation. While a lot is known about the metabolite profile of the cells and about the biochemical pathways through which these metabolites are produced, the cellular localization of the biosynthetic machineries and the importance of this localization to the regulation of the metabolism has often been given less attention. This derives from the fact that, for several of these pathways, the enzymes involved are found colocalized in one compartment where their specific localization is unlikely to influence their function. The sphingolipid (SL) metabolic pathway is a notable exception to this as SL synthetic enzymes are laid out on a specific pattern across the secretory compartments. Such compartmentalized organization of the SL synthesis has functional implications as it makes the fine-tuned regulation of the process possible by allowing cells to regulate specific segments of the pathway in response to stimuli and for adaptation. The organization, dynamics, and regulation of the SLs and their biosynthetic machinery have been investigated using imaging-based methods. Here we provide a brief introduction to the techniques that have been or that could be employed to visualize the SL biosynthetic machinery and SLs themselves and discuss the insights provided by these studies in understanding this metabolism.

    更新日期:2018-11-24
  • The effects of SDS at subsolubilizing concentrations on the planar lipid bilayer permeability: two kinds of current fluctuations
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-11-20
    A.A Anosov, E.Yu. Smirnova, E.A. Korepanova, I.M. Shogenov

    Detergent effects on lipid bilayers of artificial and biological membranes at subsolubilizing concentrations are known to include the membrane permeabilization which manifests itself through both a flip-flop of detergent molecules from the outer monolayer to the inner monolayer and the membrane leakage of entrapped solutes. We have explored the current fluctuations occurring in planar BLM of asolectin in the presence of ionic detergent SDS at subsolubilizing concentration. Two groups of current fluctuations which the average duration differs by two orders of magnitude can be distinguished. We assume that these differences in the duration of current fluctuations are associated with a different number of SDS molecules in the walls of the putative toroidal hydrophilic pores. We associated short pulses with the formation of short-lived lipid hydrophilic pores. Impulses of greater duration (steps) were associated with the formation of hydrophilic pores, the walls of which contain detergent. Taking into account the characteristics of these pores, we estimated the pore energy, as well as the edge energy of these two kinds of pores. We believe that the flip-flop of SDS molecules in liposomes is provided by long-lived pores, and the contents of the liposome leakage occurs through all pores.

    更新日期:2018-11-21
  • Lipid composition and salt concentration as regulatory factors of the anion selectivity of VDAC studied by coarse-grained molecular dynamics simulations
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-11-15
    F. Van Liefferinge, E.-M. Krammer, D. Sengupta, M. Prévost

    The voltage-dependent anion channel (VDAC) is a mitochondrial outer membrane protein whose fundamental function is to facilitate and regulate the flow of metabolites between the cytosol and the mitochondrial intermembrane space. Using coarse-grained molecular dynamics simulations, we investigated the dependence of VDAC selectivity towards small inorganic anions on two factors: the ionic strength and the lipid composition. In agreement with experimental data we found that VDAC becomes less anion selective with increasing salt concentration due to the screening of a few basic residues that point into the pore lumen. The molecular dynamics simulations provide insight into the regulation mechanism of VDAC selectivity by the composition in the lipid membrane and suggest that the ion distribution is differently modulated by POPE compared to the POPC bilayer. This occurs through the more persistent interactions of acidic residues located at both rims of the β-barrel with head groups of POPE which in turn impact the electrostatic potential and thereby the selectivity of the pore. This mechanism occurs not only in POPE single component membranes but also in a mixed POPE/POPC bilayer by an enrichment of POPE over POPC lipids on the surface of VDAC. Thus we show here that computationally-inexpensive coarse-grained simulations are able to capture, in a semi-quantitative way, essential features of VDAC anion selectivity and could pave the way toward a molecular level understanding of metabolite transport in natural membranes.

    更新日期:2018-11-15
  • Membrane-binding domains in autophagy
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-11-08
    Takuo Osawa, Jahangir Md. Alam, Nobuo N. Noda

    Autophagy is an intracellular degradation system conserved among eukaryotes that mediates the degradation of various biomolecules and organelles. During autophagy, a double membrane-bound organelle termed an autophagosome is synthesized de novo and delivers targets from the cytoplasm to the lysosomes for degradation. Autophagosome formation involves complex and dynamic membrane rearrangements, which are regulated by dozens of autophagy-related (Atg) proteins. In this review, we summarize our current knowledge of membrane-binding domains and motifs in Atg proteins and discuss their roles in autophagy.

    更新日期:2018-11-09
  • Altering the Edge Chemistry of Bicelles with Peptoids
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-11-02
    Helya Najafi, Shannon L. Servoss

    Cell function is tied to the interactions that occur within and across the cell membrane. Therefore, understanding membrane-affiliated interactions is important to many biomedical applications. Advancing the body of knowledge about these interactions will lead to discoveries in biomarker detection and therapeutic targets for disease detection and treatment. Model membrane systems are an effective way to study membrane proteins for such discoveries, allowing for stable protein structure and maintaining native activity. Bicelles, disc-shaped lipid bilayers created by combining long- and short-chain phospholipids, are the model membrane system of focus in this study. Bicelles are accessible from both sides and have a wide size range, which makes them attractive for studying membrane interactions without affecting function. In this work, bicelles were functionalized with peptoids to alter the edge chemistry. Peptoids are suitable for this application because of the large diversity of available side chain chemistries that can be easily incorporated in a sequence-specific manner. The peptoid sequence consists of three functional regions to promote insertion into the edge of bicelles. The insertion sequence at the C-terminus contains two alkyl chains and two hydrophobic, chiral aromatic groups that anchor into the bicelle edge. The facially amphipathic helix contains chiral aromatic groups on one side that interact with the lipid tails and positively charged groups on the other side, which interact with the lipid head groups. Thiol groups are included at the N-terminus to allow for visualization of peptoid location in the bicelle. Bicelle morphology and size were assessed by transmission electron microscopy (TEM) and dynamic light scattering (DLS). Peptoid location in the bicelle was determined by attachment of gold nanoparticles, which confirmed preferential incorporation of the peptoid into the bicelle edge with 82% specificity. Additionally, the peptoid-functionalized bicelles are of similar size and morphology to non-functionalized bicelles. Results from this study show that peptoid-functionalized bicelles are a promising model membrane system with potential applications in biosensors or bioseparations.

    更新日期:2018-11-05
  • Coronin-1 Derived Tryptophan-Aspartic Acid Containing Peptides Inhibit Membrane Fusion
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-10-29
    Gourab Prasad Pattnaik, Hirak Chakraborty
    更新日期:2018-10-30
  • EXPERIMENTAL AND COMPUTATIONAL STUDIES OF THE EFFECTS OF FREE DHA ON A MODEL PHOSPHATIDYLCHOLINE MEMBRANE
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-10-22
    A.R. Verde, M.B. Sierra, L.M. Alarcón, V.I. Pedroni, G.A. Appignanesi, M.A. Morini
    更新日期:2018-10-23
  • The fatty acids of sphingomyelins and ceramides in mammalian tissues and cultured cells: biophysical and physiological implications
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-10-22
    Marco M. Manni, Jesús Sot, Enara Arretxe, Rubén Gil-Redondo, Juan M Falcón-Pérez, David Balgoma, Cristina Alonso, Félix M. Goñi, Alicia Alonso

    Sphingolipids consist of a sphingoid base N-linked to a fatty acyl chain. Among them, sphingomyelins (SM) are major components of mammalian cells, while ceramide (Cer) plays an important role as a lipid second messenger. We have performed a quantitative lipidomic study of Cer and SM species in different mammalian tissues (adipose tissue, liver, brain and blood serum of human, mice, rat and dog), as well as in cell cultures of mammalian origin (primary hepatocytes, immortalized MDCK cells, mice melanoma b16 cells, and mice primary CD4 + T lymphocytes) using an ultra-high performance liquid chromatography coupled to time-of-flight mass spectrometry (UHPLC-ToF-MS)-based platform. The data have been compared with published, in general semi-quantitative, results from 20 other samples, with good agreement. The sphingoid base was predominantly d18-1 sphingosine (2-amino-4-octadecene-1,3-diol) in all cases. The fatty acid composition of SM was clearly different from that of Cer. In virtually all samples the most abundant Cer species were those containing C24:0 and C24:1 in their N-acyl chains, while the main species contained in SM was C16:0. Brain was the most divergent tissue, in which Cer and SM C18:0 were very abundant.

    更新日期:2018-10-23
  • 更新日期:2018-10-17
  • DISRUPTIVE EFFECT OF TOCOPHEROL OXALATE ON DPPC LIPOSOME STRUCTURE: DSC, SAXS, AND FLUORESCENCE ANISOTROPY STUDIES
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-10-09
    Grażyna Neunert, Jolanta Tomaszewska-Gras, Przemyslaw Siejak, Zuzanna Pietralik, Maciej Kozak, Krzysztof Polewski
    更新日期:2018-10-09
  • 更新日期:2018-10-09
  • State of the Art in Stratum Corneum Research: The Biophysical Properties of Ceramides
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-10-03
    Thomas Schmitt, Reinhard H.H. Neubert
    更新日期:2018-10-04
  • Low density lipoprotein oxidation by ferritin at lysosomal pH
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-10-01
    Oluwatosin O. Ojo, David S. Leake

    Oxidation of low density lipoprotein (LDL) has been proposed to be involved in the pathogenesis of atherosclerosis. We have previously shown that LDL can be oxidised by iron in lysosomes. As the iron-storage protein ferritin might enter lysosomes by autophagy, we have investigated the ability of ferritin to catalyse LDL oxidation at lysosomal pH. LDL was incubated with ferritin at 37 °C and pH 4.5 and its oxidation monitored spectrophotometrically at 234 nm by the formation of conjugated dienes and by measuring oxidised lipids by HPLC or a tri-iodide assay. Iron released from ferritin was measured using the ferrous iron chelator bathophenanthroline and by ultrafiltration followed by atomic absorption spectroscopy. LDL was oxidised effectively by ferritin (0.05 - 0.2 µM). The oxidation at lysosomal pH (pH 4.5) was much faster than at pH 7.4. Ferritin increased cholesteryl linoleate hydroperoxide, total lipid hydroperoxides and 7-ketocholesterol. Iron was released from ferritin at acidic pH. The iron chelators, diethylenetriaminepentaacetate and EDTA, and antioxidant N,N׳-diphenyl-p-phenylenediamine inhibited the oxidation considerably, but not entirely. The antioxidant tempol did not inhibit the initial oxidation of LDL, but inhibited its later oxidation. Cysteamine, a lysosomotropic antioxidant, inhibited the initial oxidation of LDL in a concentration-dependent manner, however, the lower concentrations exhibited a pro-oxidant effect at later times, which was diminished and then abolished as the concentration increased. These results suggest that ferritin might play a role in lysosomal LDL oxidation and that antioxidants that accumulate in lysosomes might be a novel therapy for atherosclerosis.

    更新日期:2018-10-02
  • Mechanistic studies on the effect of membrane lipid acyl chain composition on daptomycin pore formation
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-09-29
    David Beriashvili, Robert Taylor, Braden Kralt, Nooran Abu Mazen, Scott D. Taylor, Michael Palmer

    Daptomycin is a lipopeptide antibiotic that binds and permeabilizes the cell membranes of Gram-positive bacteria. Membrane permeabilization requires both calcium and phosphatidylglycerol (PG) in the target membrane, and it correlates with the formation of an oligomer that likely comprises eight subunits, which are evenly distributed between the two membrane leaflets. In both bacterial cells and model membranes, changes in the fatty acyl composition of the membrane phospholipids can prevent permeabilization. We here used liposomes to study the effect of phospholipids containing oleoyl and other fatty acyl residues on daptomycin activity, and made the following observations: 1) Oleic acid residues inhibited permeabilization when part not only of PG, but also of other phospholipids (PC or cardiolipin). 2) When included in an otherwise daptomycin-susceptible lipid mixture, even 10% of dioleoyl lipid (DOPC) can strongly inhibit permeabilization. 3) The inhibitory effect of fatty acyl residues appears to correlate more with their chain length than with unsaturation. 4) Under all conditions tested, permeabilization coincided with octamer formation, whereas tetramers were observed on membranes that were not permeabilized. Overall, our findings further support the notion that the octamer is indeed the functional transmembrane pore, and that fatty acyl residues may prevent pore formation by preventing the alignment of tetramers across the two membrane leaflets.

    更新日期:2018-09-29
  • Physicochemical characterization of 6-O-acyl trehalose fatty acid monoesters in desiccated system
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-09-29
    Shigesaburo Ogawa, Koji Honda, Taro Tsubomura, Kiichiro Totani, Isao Takahashi, Setsuko Hara
    更新日期:2018-09-29
  • Visualizing Bioactive Ceramides
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-09-25
    Daniel Canals, Silvia Salamone, Yusuf A. Hannun

    In the last 30 years, ceramides have been found to mediate a myriad of biological processes. Ceramides have been recognized as bioactive molecules and their metabolizing enzymes are attractive targets in cancer therapy and other diseases. The molecular mechanism of action of cellular ceramides are still not fully established, with insights into roles through modification of lipid rafts, creation of ceramide platforms, ceramide channels, or through regulation of direct protein effectors such as protein phosphatases and kinases. Recently, the ‘Many Ceramides’ hypothesis focuses on distinct pools of subcellular ceramides and ceramide species as potential defined bioactive entities. Traditional methods that measure changes in ceramide levels in the whole cell, such as mass spectrometry, fluorescent ceramide analogues, and ceramide antibodies, fail to differentiate specific bioactive species at the subcellular level. However, a few ceramide binding proteins have been reported, and a smaller subgroup within these, have been shown to translocate to ceramide-enriched membranes, revealing these localized pools of bioactive ceramides. In this review we want to discuss and consolidate these works and explore the possibility of defining these binding proteins as new tools are emerging to visualize bioactive ceramides in cells. Our goal is to encourage the scientific community to explore these ceramide partners, to improve techniques to refine the list of these binding partners, making possible the identification of specific domains that recognize and bind ceramides to be used to visualize the ‘Many Ceramides’ in the cell.

    更新日期:2018-09-26
  • Forgotten fatty acids—Surface properties supply conclusive evidence for including carotenoic acids
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-09-25
    Asma Zaidi, Inger Lise Alsvik, Christer L. Øpstad, Daniel Martin, Eduard Rebman, Georg Voss, Hans-Richard Sliwka, Vassilia Partali
    更新日期:2018-09-25
  • The effect of pH on the Lytic Activity of a Synthetic Mastoparan-like peptide in Anionic Model Membranes
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-09-22
    Dayane S. Alvares, Taisa Giordano Viegas, João Ruggiero Neto

    Peptide sequences containing acidic and basic residues could potentially have their net charges modulated by bulk pH with a possible influence on their lytic activity in lipid vesicles. The present study reports on a biophysical investigation of these modulatory effects on the synthetic mastoparan-like peptide L1A (IDGLKAIWKKVADLLKNT-NH2). At pH 10.0 L1A was 6 times more efficient in lysing large anionic (1-palmitoyl-oleoyl-sn-glycero-3-phosphocholine (POPC):1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol (POPG) / (8:2)) unilamellar vesicles (LUVs) than at pH 4.0. Despite the reduction of 60% in the L1A net charge in basic pH its affinity for this vesicle was almost insensitive to pH. On the other hand, L1A insertion into monolayers was dramatically influenced by subphase condition, showing that, in the neutral and basic subphases, the peptide induced surface pressure changes that surpassed the membrane lateral pressure, being able to destabilize a bilayer structure. In addition, in the basic subphase, visualization of the compression isotherms of co-spread 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC):POPG (8:2) + 4.8 mol% L1A showed that the peptide induced significant changes in solid lipid domains, indicating its capability in perturbing lipid-packing. An insight into L1A lytic activity was also obtained in giant unilamellar vesicles (GUVs) using phase contrast microscopy. The suppression of L1A lytic activity at acidic pH is in keeping with its lower insertion capability and ability to disturb the lipid monolayer. The lytic activity observed under neutral and basic conditions showed a quick and stochastic leakage following a lag-time. The permeability and the leakage-time averaged over at least 14 single GUVs were dependent on the bulk condition. At basic pH, permeability is higher and quicker than in a neutral medium in good accordance with the lipid-packing perturbation.

    更新日期:2018-09-25
  • Effects of Mono- and Di-valent Metal Cations on the Morphology of Lipid Vesicles
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-09-22
    Jiadan Hong, Huifang Yang, Dongwen Pang, Luxi Wei, Chunlin Deng
    更新日期:2018-09-25
  • FRET probes for measuring sphingolipid metabolizing enzyme activity
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-09-24
    Zainelabdeen H Mohamed, Cosima Rhein, Essa M. Saied, Johannes Kornhuber, Christoph Arenz

    Förster resonance energy transfer (FRET) probes are unique tools in biology, as they allow for a non-destructive monitoring of a certain state of a biomolecule or of an artificial substrate within living cells in real time. FRET substrates indicate their relative cleavage rate and thus the in situ activity of a given enzyme. In contrast to quenched probes or turn-on probes, one of the two separate signals of the FRET probes can be used as internal reference, which makes ratio-imaging and quantitation of cleavage events independent of cellular delivery possible. In this review, we describe the first examples of sphingolipid FRET probes in comparison to different alternative probes. Finally, we give an outlook on future probes and their potential application.

    更新日期:2018-09-25
  • Reorganization of platelet membrane sphingomyelins by adenosine diphosphate and ticagrelor
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-09-14
    Fatemeh Haghighi, Vahideh Rabani, Jean-Paul Pais-De-Barros, Siamak Davani

    Platelets are major targets for the treatment of thrombo-embolic disorders. Their plasma membrane contains specialized microdomains enriched in sphingomyelins and free cholesterol including membrane receptors. P2Y12 receptors need to be situated in these domains to be able to conduct activation signaling by adenosine diphosphate (ADP). We studied the impact of ticagrelor, a P2Y12 antagonist, and ADP on the composition and distribution of sphingomyelins in detergent-resistant membrane (DRM) of platelet membranes. Platelets were obtained from healthy donors. DRMs of platelet membranes were isolated in 4 experimental groups: control; ADP, with platelets stimulated by 20 μM ADP and 5 mM CaCl2; ticagrelor, with platelets incubated by ticagrelor 4µM methanol dissolved; and ticagrelor + ADP, with incubation by ticagrelor followed by stimulation by ADP as above. After mass spectrometry analysis, we found 16 species of sphingomyelins in platelet membrane DRMs. We also found that treatment with ticagrelor and stimulation by ADP could induce changes in the composition, distribution and concentration of sphingomyelins in membranes of platelets. In all groups, the predominant species of sphingomyelins in platelet membrane was d18:1/16:0. Taken together, our results show that stimulation by ADP or inhibition by ticagrelor changed the level and composition of sphingomyelins in platelet membranes. These changes might be considered as reorganization or new recruitment of certain types of sphingomyelins through the membrane.

    更新日期:2018-09-15
  • Temperature triggering of kinetically trapped self-assemblies in citrem-phospholipid nanoparticles
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-09-14
    Rama Prajapati, Stefan Salentinig, Anan Yaghmur
    更新日期:2018-09-15
  • 更新日期:2018-09-15
  • Preparation and Characterization of Nanostructured Lipid Carriers as Drug Delivery System: Influence of Liquid Lipid Types on Loading and Cytotoxicity
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-09-13
    A. Saedi, K. Rostamizadeh, M. Parsa, N. Dalali, N. Ahmadi

    In this study, we aimed to investigate the influence of liquid lipid types on different features of NLC. Four variations of liquid lipids such as coconut oil, fish oil, black seed oil and linseed oil were used, while for all variations, cetyl palmitate was used as the solid lipid. Different NLC were characterized and compared in terms of particle size, zeta potential, polydispersity index (PDI), drug entrapment percentage and drug loading capacity. The results indicated that NLC containing black seed oil has the smallest size. Other features like PDI, zeta potential and entrapment efficiency were the same for all the liquid lipids. By close margins, the NLC containing black seed oil had the highest percent of drug release and antioxidant activity compared to the rest. Diffusion was the major mechanism of the drug release according to the drug release kinetic fitted by Higuchi’s model. Differential scanning calorimetry (DSC) and fourier transform infrared spectroscopy (FT-IR) confirmed no strong interaction between NLC constituents. The particles showed spherical shape morphology under atomic force microscopy (AFM). According to the cell viability assay on MCF-7 cell line, the curcumin loaded NLC composed of linseed oil showed better cytotoxic activity compared to the free curcumin.

    更新日期:2018-09-14
  • A sensitive and improved throughput UPLC-MS/MS quantitation method of total cytochrome P450 mediated arachidonic acid metabolites that can separate regio-isomers and cis/trans-EETs from human plasma
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-09-07
    Maxwell Zeigler, Dale Whittington, Nona Sotoodehnia, Rozenn N. Lemaitre, Rheem A. Totah

    A method for the detection and quantification of hydroxyl and epoxy arachidonic acid (AA) metabolites in human plasma was developed using liquid-liquid extraction, phospholipid saponification followed by derivatization of the acid moiety and liquid chromatographic tandem mass spectrometric detection. Derivatization with a pyridinium analog allowed for detection in the positive ion mode, greatly improving sensitivity and the stability of the more labile AA metabolites. The entire method utilizes a 96-well plate format, increasing sample throughput, and was optimized to measure 5-, 8-, 9-, 11-, 12-, 15-, 19-, and 20- hydroxyeicosatetraenoic acid (HETE), 5,6-, 8,9-, 11,12-, and 14,15- dihydroxyeicosatrienoic acid (DHET), and the regio- and cis-/ trans- isomers of 5,6-, 8,9-, 11,12-, and 14,15-epoxyeicosatrienoic acid (EET). The method was validated for its applicability over the FA concentration range found in human plasma. Using 100 µL aliquots of pooled human plasma, EET levels, particularly 5,6-EET, were observed to be higher than previously reported, with measured concentrations of 23.6 ng/ml for 5,6-EET, 5.6 ng/mL for 5,6-trans-EET, 8.0 ng/mL for 8,9-EET, 1.9 ng/mL for 8,9-trans-EET, 8.8 ng/mL for 11,12-EET, 3.4 ng/mL for 11,12-trans-EET, 10.7 ng/mL for 14,15-EET, and 1.7 ng/mL 14,15-trans- EET. This method is suitable for larger population studies to elucidate the complex interactions between the eicosanoids and various disease states and may be used for quantitation of a wide variety of fatty acids beyond eicosanoids from small volumes of human plasma.

    更新日期:2018-09-09
  • Sphingolipids and lipid rafts: Novel concepts and methods of analysis
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-09-05
    Erhard Bieberich

    About twenty years ago, the functional lipid raft model of the plasma membrane was published. It took into account decades of research showing that cellular membranes are not just homogenous mixtures of lipids and proteins. Lateral anisotropy leads to assembly of membrane domains with specific lipid and protein composition regulating vesicular traffic, cell polarity, and cell signaling pathways in a plethora of biological processes. However, what appeared to be a clearly defined entity of clustered raft lipids and proteins became increasingly fluid over the years, and many of the fundamental questions about biogenesis and structure of lipid rafts remained unanswered. Experimental obstacles in visualizing lipids and their interactions hampered progress in understanding just how big rafts are, where and when they are formed, and with which proteins raft lipids interact. In recent years, we have begun to answer some of these questions and sphingolipids may take center stage in re-defining the meaning and functional significance of lipid rafts. In addition to the archetypical cholesterol-sphingomyelin raft with liquid ordered (Lo) phase and the liquid-disordered (Ld) non-raft regions of cellular membranes, a third type of microdomains termed ceramide-rich platforms (CRPs) with gel-like structure has been identified. CRPs are “ceramide rafts” that may offer some fresh view on the membrane mesostructure and answer several critical questions for our understanding of lipid rafts.

    更新日期:2018-09-05
  • Protein probes to visualize sphingomyelin and ceramide phosphoethanolamine
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-09-05
    Françoise Hullin-Matsuda, Motohide Murate, Toshihide Kobayashi

    Sphingomyelin (SM) is a major sphingolipid in mammalian cells whereas its analog, ceramide phosphoethanolamine (CPE) is found in trace amounts in mammalian cells and in larger amounts in invertebrates such as insect cells like Drosophila melanogaster. To visualize endogenous SM or CPE, we need specific probes able to recognize the chemical structure of the lipid, rather than its physical property. A limited number of proteins is known to specifically and strongly bind SM or CPE. These proteins are either toxins produced by non-mammalian organisms, subunits or fragments of toxins or a protein that has similar structure to a toxin. These proteins labeled with small fluorophore (e.g Alexa Fluor) or conjugated to fluorescent proteins (e.g mCherry) or other types of markers (e.g 125I, maltose-binding protein) are used to detect SM or CPE. Here we summarize the characteristics of specific SM-binding proteins, lysenin and equinatoxin; CPE- and SM/cholesterol (Chol) binding aegerolysin proteins, pleurotolysin A2, ostreolysin and erylysin A and SM/Chol-binding protein, nakanori. Then we give examples of their applications including their limitations related not only to their lipid specificity and binding constants, but also to the lipid organization in the membrane.

    更新日期:2018-09-05
  • How Cardiolipin Peroxidation Alters the Properties of the Inner Mitochondrial Membrane?
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-05-01
    Marjut Vähäheikkilä, Tapio Peltomaa, Tomasz Róg, Mario Vazdar, Sanja Pöyry, Ilpo Vattulainen

    Cardiolipins have multiple vital functions within biological cell membranes, most notably in the energy metabolism associated with the inner mitochondrial membrane. Considering their essential role, peroxidation of cardiolipins may plausibly have significant effects, as peroxidation is known to alter the functionality of lipid molecules. We used atomistic molecular dynamics simulations to study how peroxidation of cardiolipin affects the properties of the inner mitochondrial membrane. To this end, we explored what happens when varying fractions of fatty acid chains of cardiolipin are replaced by its four different oxidized products in systems modeling the inner mitochondrial membrane. We found that the oxidation of cardiolipin leads to a conformational change both in the backbone/head group and in chain regions of oxidized cardiolipin molecules. The oxidized groups were observed to shift closer to the membrane-water interface region, where they formed hydrogen bonds with several other groups. Additionally, the conformational change turned out to decrease bilayer thickness, and to increase the area per lipid chain, though these changes were minor. The acyl chain conformational order of unoxidized lipids exposed to interactions with oxidized cardiolipins was increased in carbons 3–5 and decreased in carbons 13–17 due to the structural reorganization of the cardiolipin molecules. Overall, the results bring up that the conformation of cardiolipin is altered upon oxidation, suggesting that its oxidation may interfere its interactions with mitochondrial proteins and thereby affect cardiolipin-dependent cellular processes such as electron and proton transport.

    更新日期:2018-05-01
  • Highly Effective Solvent Free Esterification of Phytosterols Employing Edible Metal Oxide-Emulsifier as Catalyst
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-05-01
    Huina Ruan, Lujing Xu, Shan Hong, Songbai Liu

    A general highly efficient solvent-free esterification of phytosterols with edible magnesium oxide and Span-60 emulsifier catalyst system has been developed. The edible emulsifier dramatically promotes the catalyzing activity of the metal oxide in the reaction. The loading of the magnesium oxide is as low as 0.1 wt% to phytosterols and far lower than the known ones. As demonstrated by the results of scanning electro-microscopy (SEM), the synergistic effect of emulsifier and magnesium oxide presumably results from elimination of nano-scale interfacial barrier between phytosterols and fatty acids and facilitation of mass transfer of reaction agents. The mild, environmentally benign, and highly effective nature of this catalytic transformation suggests its great potential applications.

    更新日期:2018-05-01
  • Phase behavior of palmitoyl and egg sphingomyelin
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-04-22
    Zoran Arsov, Emilio J. González-Ramírez, Felix M. Goñi, Stephanie Tristram-Nagle, John F. Nagle

    Despite the biological significance of sphingomyelins (SMs), there is far less structural information available for SMs compared to glycerophospholipids. Considerable confusion exists in the literature regarding even the phase behavior of SM bilayers. This work studies both palmitoyl (PSM) and egg sphingomyelin (ESM) in the temperature regime from 3 °C to 55 °C using X-ray diffraction and X-ray diffuse scattering on hydrated, oriented thick bilayer stacks. We observe clear evidence for a ripple phase for ESM in a large temperature range from 3 °C to the main phase transition temperature (TM) of ∼38 °C. This unusual stability of the ripple phase was not observed for PSM, which was in a gel phase at 3 °C, with a gel-to-ripple transition at ∼24 °C and a ripple-to-fluid transition at ∼41 °C. We also report structural results for all phases. In the gel phase at 3 °C, PSM has chains tilted by ∼30° with an area/lipid ∼45 Å2 as determined by wide angle X-ray scattering. The ripple phases for both PSM and ESM have temperature dependent ripple wavelengths that are ∼145 Å near 30 °C. In the fluid phase, our electron density profiles combined with volume measurements allow calculation of area/lipid to be ∼64 Å2 for both PSM and ESM, which is larger than that from most of the previous molecular dynamics simulations and experimental studies. Our study demonstrates that oriented lipid films are particularly well-suited to characterize ripple phases since the scattering pattern is much better resolved than in unoriented samples.

    更新日期:2018-04-25
  • Assessing Topology and Surface Orientation of an Antimicrobial Peptide Magainin 2 using Mechanically Aligned Bilayers and Electron Paramagnetic Resonance Spectroscopy
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-04-22
    Daniel J. Mayo, Indra D. Sahu, Gary A. Lorigan

    Aligned CW-EPR membrane protein samples provide additional topology interactions that are absent from conventional randomly dispersed samples. These samples are aptly suited to studying antimicrobial peptides because of their dynamic peripheral topology. In this study, four consecutive substitutions of the model antimicrobial peptide magainin 2 were synthesized and labeled with the rigid TOAC spin label. The results revealed the helical tilts to be 66° ± 5°, 76° ± 5°, 70° ± 5°, and 72° ± 5° for the TOAC substitutions H7, S8, A9, and K10 respectively. These results are consistent with previously published literature. Using the EPR (electron paramagnetic resonance) mechanical alignment technique, these substitutions were used to critically assess the topology and surface orientation of the peptide with respect to the membrane. This methodology offers a rapid and simple approach to investigate the structural topology of antimicrobial peptides.

    更新日期:2018-04-25
  • Molecular Dynamics Simulations of Glyphosate in a DPPC Lipid Bilayer ☆
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-04-21
    Ezequiel N. Frigini, J.J. López Cascales, Rodolfo D. Porasso

    Extensive Molecular Dynamics simulations have been performed to study the effect of Glyphosate (in their neutral and charged forms, GLYP and GLYP2−, respectively) on fully hydrated DiPalmitoylPhosphatidylCholine (DPPC) lipid bilayer. First, we calculated the free energy profile (using the Umbrella Sampling technique) for both states of charge of glyphosate. The minimum value for the free energy for GLYP is ∼−60 kJ.mol−1 located at z =±1.7 nm (from the lipid bilayer center), and there is almost no maximum at the center of the lipid bilayer. By contrast, the minimum for GLYP2− is ∼−35 kJ.mol−1 located at z =± 1.4 nm (from the lipid bilayer center), and the maximum reaches ∼35 kJ.mol−1 at the center of the lipid bilayer. Then, different lipid bilayer properties were analyzed for different Glyphosate:Lipid (G:L) ratios. The mean area per lipid was slightly affected, increasing only 5% (in the presence of glyphosate at high concentrations), which is in agreement with the slight decrease in deuterium order parameters. As for the thickness of the bilayer, it is observed that the state of charge produces opposite effects. On one hand, the neutral state produces an increase in the thickness of the lipid bilayer; on the other, the charged form produces a decrease in the thickness, which not depend linearly on the G:L ratios, either. The orientation of the DPPC head groups is practically unaffected throughout the range of the G:L ratios studied. Finally, the mobility of the lipids of the bilayer is strongly affected by the presence of glyphosate, considerably increasing its lateral diffusion coefficient noteworthy (one order of magnitude), with increasing G:L ratio.

    更新日期:2018-04-25
  • Morphology, compressibility and viscoelasticity of the mixed lipid monolayers in the presence of β-carotene
    Chem. Phys. Lipids (IF 2.766) Pub Date : 2018-04-05
    Katarzyna Dopierała, Marta Skrzypiec

    The aim of the present study was to investigate the interfacial behaviour of model biomembranes in the presence of β-carotene (βC). The Langmuir monolayer technique was used to form the mixed lipid film at the air/water interface. Using the surface pressure-area isotherms, the surface potential-area curves and the Brewster angle microscopy the nature of interactions between carotenoid and lipid components of the monolayers was investigated. The results were obtained for complex models of the lipid bilayer composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and cholesterol (CHOL). It was found that β-carotene affected the membrane stability, fluidity and rigidity, however this influence varied with the DPPC/CHOL ratio. The membrane permeability which is significant for biological functions was found to be affected by the presence of β-carotene in the membrane. The morphology of mixed films visualized by Brewster angle microscopy was similar for DPPC/CHOL and DPPC/CHOL/βC films indicating incorporation of carotenoid into the film. In contrary to previous reports for individual lipids, we did not observed the aggregation of βC in the mixed lipid monolayer. Moreover, from dilatational rheology experiment we concluded about the significant role of β-carotene in modulation of the elastic behaviour of the membrane, especially in physiologically significant surface pressure, i.e. at π = 30 mN/m.

    更新日期:2018-04-06
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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