TY - JOUR. T1 - Fluorescence modulation sensing of positively and negatively charged proteins on lipid bilayers. AU - Robison, Aaron D.. AU - Huang, Da. AU - Jung, Hyunsook. AU - Cremer, Paul S.. PY - 2013/1/1. Y1 - 2013/1/1. N2 - Background: Detecting ligand-receptor binding on cell membrane surfaces is required to understand their function and behavior. Detection platforms can also provide an avenue for the development of medical devices and sensor biotechnology. The use of fluorescence techniques for such purposes is highly desirable as they provide high sensitivity. Herein, we describe a technique that utilizes the sensitivity of fluorescence without directly tagging the analyte of interest to monitor ligand-receptor interactions on supported lipid bilayers. The fluorescence signal is modulated according to the charge state of the target analyte. The binding event elicits protonation or deprotonation of pH-responsive reporter dyes embedded in the lipid bilayer. Methods: Supported lipid ...
Lipid flip-flop and its associated transient pore formation are key thermodynamic properties of living cell membranes. However, there is a lack of understanding of whether ionic imbalance that exists ubiquitously across cell membranes affects lipid flip-flop and its associated functions. Potential of mean force calculations show that the free-energy barrier of lipid flip-flop on the extracellular leaflet reduces with the presence of ionic imbalance, whereas the barrier on the intracellular leaflet is generally not affected. The linear decrease of the activation energy of lipid flip-flop on the extracellular leaflet is consistent with the experimentally measured conductance-voltage relationship of zwitterionic lipid bilayers. This suggests: 1) lipid flip-flop has a directionality under physiological conditions and phospholipids accumulate at a rate on the order of 105 mu m(-2) h(-1) on the cytoplasmic side of cell membranes; 2) ion permeation across a lipid membrane is moderated by lipid ...
Understanding interactions between functionalized gold nanoparticles (NPs) and lipid bilayers is essential for their use in biomedical applications. Experiments and continuum-scale simulations have suggested that small (~5 nm diameter) cationic NPs aggregate when adsorbed to the surface of zwitterionic lipid bilayers despite being stable in aqueous solution, suggesting that bilayer-mediated interactions facilitate assembly. Determining the origin of these effects and the impact of other bilayer features, such as lipid phase separation, on the interfacial assembly of NPs would enable the design of NPs for applications that require NP assembly, such as photothermal therapy.. In this work, we use chemically specific coarse-grained molecular dynamics simulations to show that cationic NP adsorption to lipid bilayers is driven by a balance between favorable NP-lipid interactions and the unfavorable mechanical deformation of the bilayer to create local curvature. The minimization of induced curvature ...
Defensins are cationic, cysteine-rich peptides (Mr = 3500-4000) found in the cytoplasmic granules of neutrophils and macrophages. These peptides possess broad antimicrobial activity in vitro against bacteria, fungi, tumor cells, and enveloped viruses, and they are believed to contribute to the oxygen-independent antimicrobial defenses of neutrophils and macrophages. Pathophysiologic studies in vitro have pointed to the plasma membrane as a possible target for the cytotoxic action of defensins. We report here that defensins form voltage-dependent, weakly anion-selective channels in planar lipid bilayer membranes, and we suggest that this channel-forming ability contributes to their antimicrobial properties observed in vitro.. ...
Large granular lymphocytes, mediators of NK activity, bind to other cells using both the LFA (lymphocyte function-associated)-1-ICAM and the CD2-LFA-3 adhesion pathways. Here we have studied the motility and ultrastructure of large granule lymphocyte (LGL) on lipid bilayers containing purified LFA-1, ICAM-1, and the transmembrane and glycophosphatidylinositol isoforms of LFA-3. LGLs moved at 8 microns/min on ICAM-1 but poorly (less than 1 microns/min) on its receptor pair LFA-1. TM-LFA-3 promoted locomotion at a rate close to ICAM-1, whereas the cells were less motile on GPI-LFA-3. The difference in the rates of locomotion on the two isoforms of LFA-3 is presumably attributable to their difference in anchoring and lateral mobility in the bilayer. In spite of the variation in motility the ultrastructure of the adhering cells was similar on all four ligands. LGLs contacted the membrane variably, i.e., cells adhering only in a few small areas or in larger areas were detected on each ligand. The relative
Large granular lymphocytes, mediators of NK activity, bind to other cells using both the LFA (lymphocyte function-associated)-1-ICAM and the CD2-LFA-3 adhesion pathways. Here we have studied the motility and ultrastructure of large granule lymphocyte (LGL) on lipid bilayers containing purified LFA-1, ICAM-1, and the transmembrane and glycophosphatidylinositol isoforms of LFA-3. LGLs moved at 8 microns/min on ICAM-1 but poorly (less than 1 microns/min) on its receptor pair LFA-1. TM-LFA-3 promoted locomotion at a rate close to ICAM-1, whereas the cells were less motile on GPI-LFA-3. The difference in the rates of locomotion on the two isoforms of LFA-3 is presumably attributable to their difference in anchoring and lateral mobility in the bilayer. In spite of the variation in motility the ultrastructure of the adhering cells was similar on all four ligands. LGLs contacted the membrane variably, i.e., cells adhering only in a few small areas or in larger areas were detected on each ligand. The ...
TY - JOUR. T1 - Hydrodynamic interaction between overlapping domains during recurrence of registration within planar lipid bilayer membranes. AU - Han, Tao. AU - Bailey, Trevor P.. AU - Haataja, Mikko. PY - 2014/3/26. Y1 - 2014/3/26. N2 - Due to a thermodynamic coupling between the two leaflets comprising a lipid bilayer, compositional lipid domains residing within opposing leaflets are often found in registry. If the system is perturbed by displacing one domain relative to the other, diffusive and advective lipid fluxes are established to restore equilibrium and reestablish domain overlap. In this work, we focus on the advective part of the process, and first derive an analytical expression for the hydrodynamic drag coefficient associated with the advective flow for the special case of perfect domain overlap. The resulting expression identifies parameter regions where sliding friction between the leaflets dominates over viscous dissipation within the leaflets or vice versa. It is shown that in ...
The data here provides the raw data for the calculations of radial distribution functions, hydrogen bond analysis, lateral lipid diffusion and lipid tail order parameters. This raw data was generated using tools from the CPPTRAJ analysis package which is freely available with the AmberTools program (https://ambermd.org/AmberTools.php). The data presented here shows how two drug molecules (propofol and fentanyl) alter the physical and mechanical properties of DOPC and DPPC lipid bilayers, and for the first time, how a general anesthetic and an opioid analgesic/anesthetic differ in their interactions with phospholipid membranes, by direct comparison. Understanding the differences between opioid and anesthetic interactions with phospholipid bilayers will lead to a more complete understanding of general anesthesia at the molecular level ...
Detailed understanding of lipid bilayers are of tremendous importance due to their role in many biological processes. This Thesis focuses on structural and dynamical properties of lipid bilayers and their interactions with locally acting anesthetics, studied by Molecular Dynamics simulations.. The effect of dehydration of a lipid bilayer is a biologically important phenomenon which was investigated by detailed examination of a number of structural and dynamical lipid parameters at different levels of hydration. The result shows that whereas the structural properties of the bilayer only moderately depend on the degree of hydration, the dynamics of the system is affected very strongly.. Related to changes in the bilayer caused by hydration are structural and dynamical changes caused by the presence of anesthetics. Lidocaine is a common, locally acting anesthetic that interacts with lipid bilayers. The difference in position, orientation and diffusional behavior for charged and uncharged lidocaine ...
Lipid bilayers constitute one of the critical parts of all biological membranes, including cell membranes. A nice description of lipid bilayers and their function in biological membranes can be found here. They can be exceptionally complex and contain hundreds of different constituents, so simpler model lipid bilayers are often produced in the laboratory and studied experimentally. They form closed spheroidal structures, called liposomes, with a thickness of a few nm, and characteristic linear dimensions up to several microns. Larger such structures are usually called Giant Unilamellar Vesicles, or GUVs. Why should we care about these structures as mechanicians? For a number of reasons, the elastic properties of lipid membranes are thought to play a crucial role in governing their potential configurations. Recent experimental studies of the role of membrane curvature on domain formation in biomembranes, for example, provide testament to this notion. Images of their work are reproduced (with ...
Lipid bilayers constitute one of the critical parts of all biological membranes, including cell membranes. A nice description of lipid bilayers and their function in biological membranes can be found here. They can be exceptionally complex and contain hundreds of different constituents, so simpler model lipid bilayers are often produced in the laboratory and studied experimentally. They form closed spheroidal structures, called liposomes, with a thickness of a few nm, and characteristic linear dimensions up to several microns. Larger such structures are usually called Giant Unilamellar Vesicles, or GUVs. Why should we care about these structures as mechanicians? For a number of reasons, the elastic properties of lipid membranes are thought to play a crucial role in governing their potential configurations. Recent experimental studies of the role of membrane curvature on domain formation in biomembranes, for example, provide testament to this notion. Images of their work are reproduced (with ...
We investigate the structural changes to lipid membrane that ensue from the addition of aliphatic alcohols with various alkyl tail lengths. Small angle neutron diffraction from flat lipid bilayers that are hydrated through water vapor has been employed to eliminate possible artefacts of the membrane curvature and the alcohols membrane-water partitioning. We have observed clear changes to membrane structure in both transversal and lateral directions. Most importantly, our results suggest the alteration of the membrane-water interface. The water encroachment has shifted in the way that alcohol loaded bilayers absorbed more water molecules when compared to the neat lipid bilayers. The experimental results have been corroborated by molecular dynamics simulations to reveal further details. Namely, the order parameter profiles have been fruitful in correlating the mechanical model of structural changes to the effect of anesthesia.
We present optical observations of phase separation in mixed model membranes in the form of giant unilamellar vesicles. These observations are compared to the phase behavior of lipid mixtures, which we determined by X-ray scattering and differential scanning calorimetry or extracted from the existing literature. The domain properties are affected not only by the bulk phase behavior but also by the membrane lamellarity and phase transition pathways. These observations have important implications for how phase behavior determined by bulk methods using dense, multilamellar lipid bilayers are linked to phase separation in giant, unilamellar lipid bilayers as observed by microscopy ...
Detecting ligand-receptor binding on cell membrane surfaces is required to understand their function and behavior. Detection platforms can also provide an avenue for the development of medical devices and sensor biotechnology. The use of fluorescence techniques for such purposes is highly desirable as they provide high sensitivity. Herein, we describe a technique that utilizes the sensitivity of fluorescence without directly tagging the analyte of interest to monitor ligand-receptor interactions on supported lipid bilayers. The fluorescence signal is modulated according to the charge state of the target analyte. The binding event elicits protonation or deprotonation of pH-responsive reporter dyes embedded in the lipid bilayer. Supported lipid membranes containing ortho-conjugated rhodamine B-POPE (1-hexadecanoyl-2-(9Z-octadecenoyl)-sn-glycero-3-phosphoethanolamine), which fluoresces in its protonated but not in its deprotonated form, were utilized as sensor platforms for biotin-avidin and biotin
Williams, Alan John 1984. The measurement of cardiac membrane channels following their incorporation into planar phospholipid bilayers. In: Harris, P.C. ed ...
The perturbation of model lipid bilayer vesicles by halogenated hydrocarbons was investigated to determine if cellular membrane damage could be evaluated and used as a screening technique for toxicity. A fluorescent probe of 1-anilino-8-naphthalene-sulfonate (82768) (ANS) was bound to synthetic phospholipid vesicles prepared from egg lecithin and dimyristoyl-phosphatidyl-choline (DML). The fluores
This study evaluates the use of the planar lipid bilayer as a functional assay of Ca(2+)-activated K+ channel activity for use in purification of the channel protein. Ca(2+)-activated K+ channels from the plasma membrane of an insulin-secreting hamster Beta-cell line (HIT T15) were incorporated into planar lipid bilayers. The single channel conductance was 233 picoSiemens (pS) in symmetrical 140 mmol/l KCl and the channel was strongly K(+)-selective (PCl/PK = 0.046; PNa/PK = 0.027). Channels incorporated into the bilayer with two orientations. In 65% of cases, the probability of the channel being open was increased by raising calcium on the cis side of the bilayer (to which the membrane vesicles were added) or by making the cis side potential more positive. At a membrane potential of + 20 mV, which is close to the peak of the Beta-cell action potential, channel activity was half-maximal at a Ca2+ concentration of about 15 mumol/l. Charybdotoxin greatly reduced the probability of the channel being open
The influenza M2 protein not only forms a proton channel but also mediates membrane scission in a cholesterol-dependent manner to cause virus budding and release. The atomic interaction of cholesterol with M2, as with most eukaryotic membrane proteins, has long been elusive. We have now determined the cholesterol-binding site of the M2 protein in phospholipid bilayers using solid-state NMR spectroscopy. Chain-fluorinated cholesterol was used to measure cholesterol proximity to M2 while sterol-deuterated cholesterol was used to measure bound-cholesterol orientation in lipid bilayers. Carbon-fluorine distance measurements show that at a cholesterol concentration of 17 mol%, two cholesterol molecules bind each M2 tetramer. Cholesterol binds the C-terminal transmembrane (TM) residues, near an amphipathic helix, without requiring a cholesterol recognition sequence motif. Deuterium NMR spectra indicate that bound cholesterol is approximately parallel to the bilayer normal, with the rough face of the sterol
Using a high throughput screen, we have identified a family of 12-residue long peptides that spontaneously translocate across membranes. These peptides function by a poorly understood mechanism that is very different from that of the well-known, highly cationic cell penetrating peptides such as the tat peptide from HIV. The newly discovered translocating peptides can carry polar cargoes across synthetic bilayers and across cellular membranes quickly and spontaneously without disrupting the membrane. Here we report on the biophysical characterization of a representative translocating peptide from the selected family, TP2, as well as a negative control peptide, ONEG, from the same library. We measured the binding of the two peptides to lipid bilayers, their secondary structure propensities, their dispositions in bilayers by neutron diffraction, and the response of the bilayer to the peptides. Compared to the negative control, TP2 has a greater propensity for membrane partitioning, although it ...
The capability of lipid bilayers to exhibit fluid-phase behavior is a fascinating property, which enables, for example, membrane-associated components, such as lipids (domains) and transmembrane proteins, to diffuse within the membrane. These diffusion processes are of paramount importance for cells, as they are for example involved in cell signaling processes or the recycling of membrane components, but also for recently developed analytical approaches, which use differences in the mobility for certain analytical purposes, such as in-membrane purification of membrane proteins or the analysis of multivalent interactions. Here, models describing the Brownian motion of membrane inclusions (lipids, peptides, proteins, and complexes thereof) in model bilayers (giant unilamellar vesicles, black lipid membranes, supported lipid bilayers) are summarized and model predictions are compared with the available experimental data, thereby allowing for evaluating the validity of the introduced models. It will be
In this article, we investigate fluid-gel transformations of a DPPC lipid bilayer in the presence of nanoparticles, using coarse grained molecular dynamics. Two types of nanoparticles are considered, specifically a 3 nm hydrophobic nanoparticle located in the core of the bilayer and a 6 nm charged nanoparticle located at the interface between the bilayer and water phase. Both negatively and positively charged nanoparticles at the bilayer interface are investigated. We demonstrate that the presence of all types of nanoparticles induces disorder effects in the structure of the lipid bilayer. These effects are characterized using computer visualization of the gel phase in the presence of nanoparticles, radial distribution functions, and order parameters. The 3 nm hydrophobic nanoparticle immersed in the bilayer core and the positively charged nanoparticle at the bilayer surface have no effect on the temperature of the fluid-gel transformation, compared to the bulk case. Interestingly, a negatively ...
1. Wagner ML, Tamm LK (2000) Tethered polymer-supported planar lipid bilayers for reconstitution of integral membrane proteins: silane-polyethyleneglycol-lipid as a cushion and covalent linker. Biophys J 79: 1400-1414.. 2. Sackmann E (1996) Supported membranes: scientific and practical applications. Science 271: 43-48.. 3. Richter RP, Berat R, Brisson AR (2006) Formation of solid-supported lipid bilayers: an integrated view. Langmuir 22: 3497-3505.. 4. Kusters I, Mukherjee N, de Jong MR, Tans S, Koçer A, et al. (2011) Taming Membranes: Functional Immobilization of Biological Membranes in Hydrogels. PLoS ONE 6(5): e20435. doi:10.1371/journal.pone.0020435. 5. Schuler, M. A., Denisov, I. G., Sligar, S. G. (2013) Nanodiscs as a new tool to examine lipid-protein interactions. Methods Mol Biol. 974, 415-433.. 6. Sloan, C. D., Marty, M. T., Sligar, S. G., Bailey, R. C. (2013) Interfacing lipid bilayer nanodiscs and silicon photonic sensor arrays for multiplexed protein-lipid and protein-membrane ...
Read Examining the Origins of the Hydration Force Between Lipid Bilayers Using All-Atom Simulations, The Journal of Membrane Biology on DeepDyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips.
Several techniques to assemble artificial lipid bilayers involve the zipping of monolayers. Their efficiency is determined by the renewal of the saturated monolayers to be zipped and this proceeds by adsorption of lipids dispersed in oil as aggregates. The size of these lipids aggregates is a key parameter to ensure both the stability of the suspension and a fast release of lipids at the interface. We propose a new method inspired from the solvent-shifting nucleation process allowing to control and tune the lipid aggregates size and that improves the production of artificial membranes. It is simpler and faster than current methods starting from a dry lipid film, which are highly sensitive to environmental conditions. This method opens the route to bilayer production processes with new potentialities in membrane composition.
Recently, the transfer method has been shown to be useful for preparing cell-sized phospholipid bilayer vesicles, within which desired substances at desired concentrations can be encapsulated, with a desired asymmetric lipid composition. Here, we investigated the transfer process of water-in-oil (W/O) droplets coat 2013 Hot Papers
A novel solid-state NMR technique for identifying the asymmetric insertion depths of membrane proteins in lipid bilayers is introduced. By applying Mn2+ ions on the outer but not the inner leaflet of lipid bilayers, the sidedness of protein residues in the lipid bilayer can be determined through paramagnetic relaxation enhancement (PRE) effects. Protein-free lipid membranes with one-side Mn2+-bound surfaces exhibit significant residual 31P and lipid headgroup 13C intensities, in contrast to two-side Mn2+-bound membranes, where lipid headgroup signals are mostly suppressed. Applying this method to a cell-penetrating peptide, penetratin, we found that at low peptide concentrations, penetratin is distributed in both leaflets of the bilayer, in contrast to the prediction of the electroporation model, which predicts that penetratin binds to only the outer lipid leaflet at low peptide concentrations to cause an electric field that drives subsequent peptide translocation. The invalidation of the ...
Advances in Planar Lipid Bilayers and Liposomes, Volume 6, continues to include invited chapters on a broad range of topics, covering both main arrangements...
Purchase Advances in Planar Lipid Bilayers and Liposomes, Volume 5 - 1st Edition. Print Book & E-Book. ISBN 9780123736871, 9780080466545
Lipid bilayers form the boundaries of the cell and its organelles. Many physiological processes, such as cell movement and division, involve bending and folding of the bilayer at high curvatures. Currently, bending of the bilayer is treated as an elastic deformation, such that its stress-strain response is i
TY - JOUR. T1 - Vibrational layer eigenmodes of binary phospholipid-cholesterol bilayers at low temperatures. AU - Leonov, D. V.. AU - Adichtchev, S. V.. AU - Dzuba, S. A.. AU - Surovtsev, N. V.. PY - 2019/2/22. Y1 - 2019/2/22. N2 - Raman spectra in the low-frequency spectral range - between 5 and 90cm-1 - were studied for multilamellar bilayers prepared with cholesterol (Chol) and phospholipids of three different types: doubly unsaturated lipids 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), monounsaturated lipids 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), and fully saturated lipids 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). The narrow peak seen below 250 K and positioned between 9 and 18cm-1 - depending on the system and temperature - was attributed to the vibrational eigenmode of a lipid monolayer. For the DOPC-Chol bilayer, the peak position and the peak width were found to monotonically increase and decrease, respectively, with the Chol concentration. For POPC-Chol ...
We will discuss the physics that governs the lipid localization and domain formation in multicomponent lipid bilayers coupled to an elastic substrate. Lipid localization and domain formation has been studied extensively in biological cell membranes. In this talk we will extend a previous model for membrane energetics to account for the coupling between the bending and the local lipid composition of the two leaflets. Our aim is to determine the relationship between the localization and domain formation in the presence of lipid flip-flops between the two leaflets and the effect of intrinsic curvature of the lipids. Using a lattice model for the membrane, we simulate the system and study the effect of lipid flip-flop on lipid organization in the membrane. To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2012.MAR.B41.15. ...
Progress with respect to enrichment and separation of native membrane components in complex lipid environments, such as native cell membranes, has so far been very limited. The reason for the slow progress can be related to the lack of efficient means to generate continuous and laterally fluid supported lipid bilayers (SLBs) made from real cell membranes. We show in this work how the edge of a hydrodynamically driven SLB can be used to induce rupture of adsorbed lipid vesicles of compositions that typically prevent spontaneous SLB formation, such as vesicles made of complex lipid compositions, containing high cholesterol content or being derived from real cell membranes. In particular, upon fusion between the moving edge of a preformed SLB and adsorbed vesicles made directly from 3T3 fibroblast cell membranes, the membrane content of the vesicles was shown to be efficiently transferred to the SLB. The molecular transfer was verified using cholera toxin B subunit (CTB) binding to monosialoganglioside
O:13:\PanistOpenUrl\:36:{s:10:\\u0000*\u0000openUrl\;N;s:6:\\u0000*\u0000idc\;N;s:6:\\u0000*\u0000fmt\;s:7:\journal\;s:6:\\u0000*\u0000doi\;s:0:\\;s:6:\\u0000*\u0000pii\;s:0:\\;s:7:\\u0000*\u0000pmid\;s:0:\\;s:9:\\u0000*\u0000atitle\;s:111:\THEORY OF SPIN-LATTICE RELAXATION IN LIPID BILAYERS AND BIOLOGICAL MEMBRANES. 2H AND 14N QUADRUPOLAR ...
The transport of palmitic acid (PA) across planar lipid bilayer membranes was measured using a high specific activity [14C]palmitate as tracer for PA. An all-glass trans chamber was employed in order to minimize adsorbance of PA onto the surface. Electrically neutral (diphytanoyl phosphatidylcholine) and charged (Azolectin) planar bilayers were maintained at open electric circuit. We found a permeability to PA of (8.8 +/- 1.9) x 10(-6) cm s(-1) (n = 15) in neutral and of (10.3 +/- 2.2) x 10(-6) cm s(-1) (n = 5) in charged bilayers. These values fall within the order of magnitude of those calculated from desorption constants of PA in different vesicular systems. Differences between data obtained from planar and vesicular systems are discussed in terms of the role of solvent, radius of curvature, and pH changes. ...
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Lipid bilayers are unique soft materials operating in general in the low Reynolds limit. While their shape is predominantly dominated by curvature elasticity as in a solid shell, their in-plane behavior is that of a largely inextensible viscous fluid. Furthermore, lipid membranes are extremely responsive to chemical stimuli. Because in their biological context they are continuously brought out-of-equilibrium mechanically or chemically, it is important to understand their dynamics. Here, we introduce Onsagers variational principle as a general and transparent modeling tool for lipid bilayer dynamics. We introduce this principle with elementary examples, and then use it to study the sorption of curved proteins on lipid membranes.. Link to Chapter ...
One of the key lockers to understand mechanisms of biological action of drugs and natural compounds is their capacity to incorporate/cross lipid bilayer membranes. In the light of demanding experimental techniques, in silico molecular modelling has become a powerful alternative to tackle these issues. In the past few years, molecular dynamics (MD) has opened many perspectives, providing an atomistic description of the related intermolecular interactions. Using MD simulations, we have explored the capacity of several compounds (polyphenols, vitamins E and C, plantazolicin, carprofens) to incorporate lipid bilayer membranes. The different compounds were chosen according to their different biological functions, namely (i) antioxidant activity against lipid peroxidation, (ii) antimicrobial activity with the possibility of trans-membrane pore formation, and (iii) inhibition of enzymes involved in Alzheimers disease. In order to rationalize their mechanisms of action, their position and orientation in
Terminal lipophilization of a unique DNA dodecamer by various nucleolipid headgroups: Their incorporation into artificial lipid bilayers and hydrodynamic properties
9] L. Movileanu, D. Popescu, S. I. Popescu, Transbilayer pores induced by thickness fluctuations, Bull. Math. Biol. 68 (2006) 1231-1255. V. Zhelev, D. Needham, Tension-stabilized pores in giant vesicles: Determination of pore size and pore line tension, Biochim. Biophys. Acta 1147 (1993) 89-104. [11] M. Winterhalter, W. Helfrich, Effect of voltage on pores in membranes, Phys. Rev. A 36 (1987) 5874-5876. Random Processes in the Appearance and Dynamics of an Electropore 33 [12] E. Neumann, M. Schaefer-Ridder, Y. Frey, Polymorphism of monolayers of monomeric and macromolecular lipids: On the defect structure of crystalline phases and the possibility of hexatic order formation in physics of amphiphilic layers, in: J. Meunier, D. Langevin, V. ), Physics of amphiphilic layers, Springer, Berlin (1987). [43] M. Langner, H. Pruchnik, K. Kubica, The effect of the lipid bilayer state on fluorescence intensity of fluorescein-PE in a saturated lipid bilayer, Z. Naturforsch. 55 (2000) 418-424. [44] K. Kubica, ...
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Supplementary MaterialsSupplementary Information 41598_2017_4219_MOESM1_ESM. in lipid bilayers. Additionally, the DNP sensitivity-enhanced two-dimensional 13C/13C chemical shift correlations via proton AUY922 inhibition driven spin diffusion offered length constraints to characterize protein-lipid interactions and uncovered the transmembrane topology of cytochrome b5. The outcomes reported in this research would pave methods for high-quality structural and topological investigations of membrane-bound full-duration bitopic proteins complexes under physiological circumstances. Launch Bitopic membrane proteins with an KI67 antibody individual membrane-spanning -helix represent over fifty percent of most membrane proteins, which contain approximately 1 / 3 of all open up reading frames (ORFs), in individual AUY922 inhibition genomes1C3. Their dynamic protein-proteins and protein-ligand interactions in the membrane environment play various vital functions in the cellular procedures connected with ...
Biological membranes mainly constituent lipid molecules along with some proteins and steroles. The properties of the pure lipid bilayers as well as in the presence of other constituents (in case of two or three component systems) are very important to be studied carefully to model these systems and compare them with the realistic systems. Molecular dynamic simulations provide a good opportunity to model such systems and to study them at microscopic level where experiments fail to do. In this thesis we study the structural and dynamic properties of the pure phospholipid bilayers and the phase behavior of phospholipid bilayers when other constituents are present in them. Material and structural properties like area per lipid and area compressibility of the phospholipids show a big scatter in experiments. These properties are studied for different system sizes and it was found that the increasing undulations in large systems effect these properties. A correction was applied to area per lipid and ...
Proteins and lipids are the building blocks of biological membranes. In the past and at present, only the lipids in the form of bilayers, vesicles, and thin films found/find applications in...
Cholesterol, due to its condensing effect, is considered an important regulator of membrane thickness. Other sterols, due to their structural similarities to cholesterol, are often assumed to have a universal effect on membrane properties similar to the condensing effect of cholesterol, albeit possibly to different degrees. We used x-ray diffraction to investigate this assumption. By the combination of lamellar diffraction and grazing-angle scattering, we measured the membrane thickness and the tilt-angle distribution of the lipids hydrocarbon chains. This method is sensitive to phase separation, which is important for examining the miscibility of sterols and phospholipids. Mixtures of ergosterol or cholesterol with dimyristoylphosphatidylcholine, palmitoyloleoylphosphatidylcholine, and dioleoylphosphatidylcholine were systematically studied. We found that mixing ergosterol with phospholipids into a single phase became increasingly difficult with higher sterol concentrations and also with ...
This thesis deals with the study of lipid bilayer systems by solid-state nuclear magnetic resonance. Two-dimensional 1H-13C separated local field experiments under magic-angle spinning were employed to investigate structural and dynamical modifications of cell membranes, resulting from the addition of compounds with some biological relevance. For further interpretation of the segmental order obtained from the 2D experiments other methods, such as 31P-NMR, 2H-NMR and molecular dynamics simulations, were also employed. The work presented in this thesis can be divided into two parts. The first part refers to the setup of experimental conditions. Heating and hydration effects were addressed in order to define both the temperature of the system as well as the number of water molecules per lipid necessary to fully hydrate the bilayer. Application of this experimental setup to lipid membrane systems with biological relevance constitutes the second part. The interaction of monogalactosyl- ...
Biological membranes do not only occur as planar bilayer structures, but bilayers have also been shown to, depending on the lipid composition, curve into intriguing 3D structures. Understanding the biological implication as well as the application of such interfaces, for e.g. drug delivery and other biomedical application, requires the development of well-defined model system.. We have shown that spin-coating the constituting lipids followed by hydration of the lipid layer can be used to form non-lamellar liquid crystalline surfaces of different types on the surface. In order to make the layers more responsive polymer micro-gels with a diameter of about 55 nm can be embedded within the layer. Another way to for non-planar lipid interfaces are to deposit lipids on nanostructured surfaces. Here we demonstrate the formation of fluid supported bilayers on vertical gallium phosphide nanowire (NW) forests using self-assembly from lipid vesicular dispersions.1 The phospholipid mixture used had a ...
The combined effects of the tendency of cholesterol to order lipids in the liquid phase and the coupling between lipids in the two leaves of a bilayer are investigated theoretically utilizing a Landau free energy. We show that as a consequence of these combined effects, lateral phase separation in the outer leaf between cholesterol-rich and -poor liquids causes a similar, but weaker, phase separation in the inner leaf. Just as the areal density of lipids in the outer leaf increases in the cholesterol-rich regions, so the areal density of lipids also increases in the inner leaf. Thus, the areal density in the inner leaf varies spatially, reflecting spatial variations of the areal density in the outer leaf. This provides a mechanism for proteins attached to the inner leaf via a hydrocarbon tether to respond to variations in the composition of the outer leaf. We also note that the effect of coupling between the leaves should be observable in artificial bilayers.. ...
The combined effects of the tendency of cholesterol to order lipids in the liquid phase and the coupling between lipids in the two leaves of a bilayer are investigated theoretically utilizing a Landau free energy. We show that as a consequence of these combined effects, lateral phase separation in the outer leaf between cholesterol-rich and -poor liquids causes a similar, but weaker, phase separation in the inner leaf. Just as the areal density of lipids in the outer leaf increases in the cholesterol-rich regions, so the areal density of lipids also increases in the inner leaf. Thus, the areal density in the inner leaf varies spatially, reflecting spatial variations of the areal density in the outer leaf. This provides a mechanism for proteins attached to the inner leaf via a hydrocarbon tether to respond to variations in the composition of the outer leaf. We also note that the effect of coupling between the leaves should be observable in artificial bilayers.. ...
TY - JOUR. T1 - Diffusion limitation in the block by symmetric tetraalkylammonium ions of anthrax toxin channels in planar phospholipid bilayer membranes. AU - Blaustein, Robert O.. AU - Finkelstein, Alan. PY - 1990/11. Y1 - 1990/11. N2 - Current flow through the channel formed in planar phospholipid bilayer membranes by the PA65 fragment of anthrax toxin is blocked, in a voltage-dependent manner, by tetraalkylammonium ions (at micromolar concentrations), which bind to a blocking site within the channel lumen. We have presented evidence that diffusion plays a significant role in the kinetics of blocking by tetrabutylammonium ion (Bu4N+) from the cis (toxin-containing) side of the membrane (Blaustein, R. O., E. J. A. Lea, and A. Finkelstein. 1990. J. Gen. Physiol. 96:921-942); in this paper we examine the implications and consequences of diffusion control for binding kinetics. As expected for a diffusion-affected reaction, both the entry rate constant (k1cis) of Bu4N+ from the cis solution to the ...
Experimental and computational studies have indicated that hydrophobicity plays a key role in driving the insertion of transmembrane alpha-helices into lipid bilayers. Molecular dynamics simulations allow exploration of the nature of the interactions of transmembrane alpha-helices with their lipid bilayer environment. In particular, coarse-grained simulations have considerable potential for studying many aspects of membrane proteins, ranging from their self-assembly to the relation between their structure and function. However, there is a need to evaluate the accuracy of coarse-grained estimates of the energetics of transmembrane helix insertion. Here, three levels of complexity of model system have been explored to enable such an evaluation. First, calculated free energies of partitioning of amino acid side chains between water and alkane yielded an excellent correlation with experiment. Second, free energy profiles for transfer of amino acid side chains along the normal to a phosphatidylcholine
The effects of the insecticide lindane on the phase transition in multilamellar bilayers of saturated diacylphosphatidylcholines of different acyl chain length (DC14PC, DC16PC, and DC18PC) have been studied by means of differential scanning calorimetry (DSC), as well as computer-simulation calculations on a molecular interaction model. The calorimetric data show that increasing concentrations of lindane lower the transition temperature and lead to a broadening of the specific heat in a systematic way depending on the lipid acyl chain length. Kinetic effects in the observed calorimetric traces indicate that the incorporation of lindane into multilamellar lipid bilayers is slow, but faster for the shorter lipid species. Large unilamellar vesicles do not show such kinetic effects. The transition enthalpy is for all three lipid species found to be independent of the lindane concentration which implies that the entropy of mixing is vanishingly small. This lends support to a microscopic molecular ...
TY - JOUR. T1 - Lipid fluorination enables phase separation from fluid phospholipid bilayers. AU - Webb, S. J.. AU - Greenway, K.. AU - Bayati, M.. AU - Trembleau, Laurent Alain Claude. PY - 2006/5. Y1 - 2006/5. N2 - To probe the effect of lipid fluorination on the formation of lipid domains in phospholipid bilayers, several new fluorinated and non-fluorinated synthetic lipids were synthesised, and the extent of phase separation of these lipids from phospholipid bilayers of different compositions was determined. At membrane concentrations as low as 1% mol/mol, both fluorinated and non-.uorinated lipids were observed to phase separate from a gel-phase ( solid ordered) phospholipid matrix, but bilayers in a liquid disordered state caused no phase separation; if the gel-phase samples were heated above the transition temperature, then phase separation was lost. We found incorporation of perfluoroalkyl groups into the lipid enhanced phase separation, to such an extent that phase separation was ...
The assembly of nucleic acid nanostructures with controlled size and shape has large impact in the fields of nanotechnology, nanomedicine and synthetic biology. The directed arrangement of nano-structures at interfaces is important for many applications. In spite of this, the use of laterally mobile lipid bilayers to control RNA three-dimensional nanostructure formation on surfaces remains largely unexplored. Here, we direct the self-assembly of RNA building blocks into three-dimensional structures of RNA on fluid lipid bilayers composed of cationic 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) or mixtures of zwitterionic 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC) and cationic sphingosine. We demonstrate the stepwise supramolecular assembly of discrete building blocks through specific and selective RNA-RNA interactions, based on results from quartz crystal microbalance with dissipation (QCM-D), ellipsometry, fluorescence recovery after photobleaching (FRAP) and total internal reflection
Progress in theoretical modelling (our group has performed molecularly detailed self-consistent field (SCF) calculations on lipid bilayer membranes) in combination with advanced and cutting-edge techniques have enabled us to perform more advanced experiments on lipid bilayers. This makes it possible to determine on how lipids and other membrane constituents organise the delicate force balances in bilayers that are responsible for the structure and structural (in)stability.. The aim of this PhD project is to develop an experimental membrane platform to determine mechanical properties and topological integrity of lipid membranes of increasing complexity. The experimental platform comprises of a supported double lipid membrane in a flow cell, mounted in a set-up including a TIRF microscope and an AFM dedicated to force measurements. The influence of various perturbing stimuli, such as edge-active agents, antimicrobial peptides and nanoparticles, on these membrane properties will be investigated. ...
TY - JOUR. T1 - Assembly of α-synuclein aggregates on phospholipid bilayers. AU - Lv, Zhengjian. AU - Hashemi, Mohtadin. AU - Banerjee, Siddhartha. AU - Zagorski, Karen. AU - Rochet, Jean Christophe. AU - Lyubchenko, Yuri L.. N1 - Funding Information: The work at the University of Nebraska Medical Center (UNMC) was supported by grants from the National Institutes of Health to Y.L.L. ( R01 GM096039 , R01GM118006 and R21 NS101504 ). J.C.R. was supported by the Branfman Family Foundation . M.H. was partially supported by the UNMC Graduate Fellowship. The computational modeling was partially performed using resources at the Holland Computing Center of the University of Nebraska, which receives support from the Nebraska Research Initiative . Anton 2 computer time was provided by the Pittsburgh Supercomputing Center (PSC) through Grant R01GM116961 from the National Institutes of Health. The Anton 2 machine at PSC was generously made available by D.E. Shaw Research. The authors thank Melody A. ...
Recent literature has shown that buffers affect the interaction between lipid bilayers through a mechanism that involves van der Waals forces, electrostatics, hydration forces and membrane bending rigidity. This talk will highlight our recent work that shows phase coexistence can be a result of Goods buffer charges on the mixed chain 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) lipid bilayers. Since the two phases must be in osmotic equilibrium with one another, this behavior challenges theoretical models of lipid interactions and introduces new variables to consider for the Gibbs phase rule. This model of lipid charging was then used to explain the mechanisms behind phase separation in lipid mixtures containing charged lipid head groups, particularly phosphatidylinositols. Furthermore, this work is then applied to our understanding of underlying mechanisms involved in membrane protein selective association with phosphoinositols, and later re-organization of these membranes. This work ...
HYPOTHESIS It is known that nanoparticles (NPs) in a biological fluid are immediately coated by a protein corona (PC), composed of a hard (strongly bounded) and a soft (loosely associated) layers, which represents the real nano-interface interacting with the cellular membrane in vivo. In this regard, supported lipid bilayers (SLB) have extensively been used as relevant model systems for elucidating the interaction between biomembranes and NPs. Herein we show how the presence of a PC on the NP surface changes the interaction between NPs and lipid bilayers with particular care on the effects induced by the NPs on the bilayer structure. EXPERIMENTS In the present work we combined Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D) and Neutron Reflectometry (NR) experimental techniques to elucidate how the NP-membrane interaction is modulated by the presence of proteins in the environment and their effect on the lipid bilayer. FINDINGS Our study showed that the NP-membrane interaction is
Lipid bilayers are important in biological cells. They are the basis of cell membranes, and they surround most cell organelles. Lipid bilayers form automatically from phospholipids by self-assembly. The phospholipids have heads which mix with water and tails which reject water. So the tails come together in the centre of the double layer, and the heads on the outside are surrounded by water. The lipid bilayers stop most water-soluble (hydrophilic) molecules passing through. They also stop most ions. In cells, proteins are put in the bilayer by enzymes. The proteins decide which molecules come in and which go out of the cell. For example, cells control salt concentrations and pH by pumping ions across their membranes using proteins called ion pumps. ...
Planar solid-supported membranes based on amphiphilic block copolymers represent promising systems for the artificial creation of structural surfaces. Here we introduce a method for engineering functional planar solid-supported membranes through insertion of active biomolecules. We show that membranes based on poly(dimethylsiloxane)-block-poly(2-methyl-2-oxazoline) (PDMS-b-PMOXA) amphiphilic diblock copolymers, which mimic natural membranes, are suitable for hosting biomolecules. Our strategy allows preparation of large-area, well-ordered polymer bilayers via Langmuir-Blodgett and Langmuir-Schaefer transfers, and insertion of biomolecules by using Bio-Beads. We demonstrate that a model membrane protein, the potassium channel from the bacterium Mesorhizobium loti, remains functional after insertion into the planar solid-supported polymer membrane. This approach can be easily extended to generate a platform of functional solid-supported membranes by insertion of different hydrophobic biomolecules, ...
Descrição: We establish and quantify correlations among the molecular structures, interaction forces, and physical processes associated with light-responsive self-assembled surfactant monolayers or bilayers at interfaces. Using the surface forces apparatus (SFA), the interaction forces between adsorbed monolayers and bilayers of an azobenzene-functionalized surfactant can be drastically and controllably altered by light-induced conversion of trans and cis molecular conformations. These reversible conformation changes affect significantly the shape of the molecules, especially in the hydrophobic region, which induces dramatic transformations of molecular packing in self-assembled structures, causing corresponding modulation of electrostatic double layer, steric hydration, and hydrophobic interactions. For bilayers, the isomerization from trans to cis exposes more hydrophobic groups, making the cis bilayers more hydrophobic, which lowers the activation energy barrier for (hemi)fusion. A ...
TY - JOUR. T1 - Chiral Recognition of Lipid Bilayer Membranes by Supramolecular Assemblies of Peptide Amphiphiles. AU - Sato, Kohei. AU - Ji, Wei. AU - Álvarez, Zaida. AU - Palmer, Liam C.. AU - Stupp, Samuel I.. PY - 2019/6/10. Y1 - 2019/6/10. N2 - On the basis of the exclusive existence of homochirality in biomolecules and the well-known phenomenon of chiral recognition, it is obvious that chirality is a crucial factor in biological events. We report here that supramolecular assemblies of peptide amphiphiles interact with lipid bilayer membranes in a stereospecific manner. When negatively charged chiral phospholipid bilayer vesicles were subjected to the assemblies, we found that peptide amphiphiles with l-amino acids show stronger affinity for the liposomes compared to the ones with d-amino acids. To examine their biological functions, we tested the cytotoxicity of nanofibers against mammalian primary cells using human bone marrow mesenchymal stem cells and murine astroglial cells. We ...
Klughammer, B., Benz, B., Betz, M., Thume, M., & Dietz, K. - J. (1992). Reconstitution of vacuolar ion channels into planar lipid bilayers. Biochimica et Biophysica Acta, 1104(2), 308-316. doi:10.1016/0005-2736(92)90045- ...
The authors have studied microstructure evolution during thermally induced phase separation in a class of binary supported lipid bilayers using a quantitative application of imaging ellipsometry. The bilayers consist of binary mixtures consisting of a higher melting glycosphingolipid, galactosylceramide (GalCer), which resides primarily in the outer leaflet, and a lower melting, unsaturated phospholipid, 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC). Three different bilayer compositions of GalCer/DLPC mixtures at 35:65, 20:80, and 10:90 molar ratios were cooled at controlled rates from their high-temperature homogeneous phase to temperatures corresponding to their phase coexistence regime and imaged in real time using imaging ellipsometry. During the thermotropic course of GalCer gelation, we find that two distinct types of morphological features modulate. First, the formation and growth of chain and fractal-like defects ascribed to the net change in molecular areas during the phase transition. The
TY - JOUR. T1 - Theory of modulated phases in lipid bilayers and liquid crystal films. AU - Chen, C. M.. AU - MacKintosh, F. C.. N1 - Copyright: Copyright 2017 Elsevier B.V., All rights reserved.. PY - 1996. Y1 - 1996. N2 - We present a general theory for equilibrium-modulated phases of chiral and achiral bilayer membranes and liquid crystal films. Both bulk smectics as well as freely suspended films are considered. For flexoelectric systems, continuous structural phase transitions are predicted among square-lattice, hexagonal, and distorted two-dimensional modulated phases as a function of the applied electric field. It is also shown that only uniform flat phases are predicted for thin films. One-dimensional ripple phases and two-dimensional square-lattice phases can occur with increasing film thickness.. AB - We present a general theory for equilibrium-modulated phases of chiral and achiral bilayer membranes and liquid crystal films. Both bulk smectics as well as freely suspended films are ...
TY - JOUR. T1 - Impact of cholesterol on voids in phospholipid membranes. AU - Falck, E.. AU - Patra, M.. AU - Karttunen, M.E.J.. AU - Hyvönen, M.T.. AU - Vattulainen, I.. PY - 2004. Y1 - 2004. N2 - Free volume pockets or voids are important to many biological processes in cell membranes. Free volume fluctuations are a prerequisite for diffusion of lipids and other macromolecules in lipid bilayers. Permeation of small solutes across a membrane, as well as diffusion of solutes in the membrane interior are further examples of phenomena where voids and their properties play a central role. Cholesterol has been suggested to change the structure and function of membranes by altering their free volume properties. We study the effect of cholesterol on the properties of voids in dipalmitoylphosphatidylcholine (DPPC) bilayers by means of atomistic molecular dynamics simulations. We find that an increasing cholesterol concentration reduces the total amount of free volume in a bilayer. The effect of ...
TY - JOUR. T1 - Durability of oxygen evolution of photosystem II incorporated into lipid bilayers. AU - Noji, Tomoyasu. AU - Kondo, Masaharu. AU - Kawakami, Keisuke. AU - Shen, Jian Ren. AU - Nango, Mamoru. AU - Dewa, Takehisa. PY - 2014/11. Y1 - 2014/11. N2 - Photosystem II (PSII) has attracted a lot of attention for use in the construction of artificial photosynthetic materials due to its high activity of oxidation of water molecules. However, the robustness of PSII needs to be improved for in vitro application. In this study, we incorporated PSII (Thermosynechococcus vulcanus) into various phospholipid membranes to examine the activity and durability of oxygen evolution. PSII was incorporated into anionic 1,2-dioleoyl-sn-glycero-3-phospho-(1-rac-glycerol) (PSII-DOPG), zwitterionic 1,2-dioleoyl-sn-glycero-3-phosphocholine (PSII-DOPC), and cationic 1,2-dioleoyl-sn-glycero-3-ethylphosphocholine (PSII-EDOPC). Structural integrity of PSII was examined by absorption and fluorescence spectroscopy. ...
We investigated the thermotropic phase behavior of the distearoylphosphatidylcholine (DSPC)-cholesterol binary bilayer membrane as a function of the cholesterol composition (X(ch)) by fluorescence spectroscopy using 6-propionyl-2-(dimethylamino)naphthalene (Prodan) and differential scanning calorimetry (DSC). The fluorescence spectra, each of which has a single maximum, showed that the wavelength at the maximum intensity (lambda(max)) changed depending on the bilayer state: ca. 440 nm for the lamellar gel (L(beta) or L(beta)) and the liquid ordered (L(o)) phases, ca. 470 nm for the ripple gel (P(beta)) phase and ca. 490 nm for the liquid crystalline (L(alpha)) phase, respectively. The transition temperatures were determined from the temperature dependences of the lambda(max) and endothermic peaks of the DSC thermograms. Both measurements showed that the pretransition disappears around X(ch)=0.035. The constructed temperature-X(ch) phase diagram indicated that the phase behavior of the binary ...
Carbohydrate-protein interactions play a major-role in recognition of cells by external macromolecules. Single saccharide ligands, however, bind only weakly to their protein receptors. Sufficient affinity is achieved by appropriate mutual orientation of the saccharide epitopes and their protein receptors, which allows multiple simultaneous interactions. In other words, high affinity binding is achieved through multivalency, where the high number of simultaneous binding events compensates the lack of strength of an individual interaction. Solid-supported methods allowing synthesis of multiantennary glycoconjugates have, hence, been under active development. The present paper is a review of the solid-phase protocols useful for preparation of glycoconjugates. ...
Effects of hydrostatic pressure on the molecular structure and endothermic phase transitions of phosphatidylcholine bilayers: a Raman scattering study
The effects of the cholesterol analog 5α-cholestan-3β-ol-6-one (6-ketocholestanol) on bilayer structure, bilayer cohesive properties, and interbilayer repulsive pressures have been studied by a combination of X-ray diffraction, pipette aspiration, and dipole potential experiments. It is found that 6-ketocholestanol, which has a similar structure to cholesterol except with a keto moiety at the 6 position of the B ring, has quite different effects than cholesterol on bilayer organization and cohesive properties. Unlike cholesterol, 6-ketocholestanol does not appreciably modify the thickness of liquid-crystalline egg phosphatidylcholine (EPC) bilayers, and causes a much smaller increase in bilayer compressibility modulus than does cholesterol. These data imply that 6-ketocholestanol has both its hydroxyl and keto moieties situated near the water-hydrocarbon interface, thus making its orientation in the bilayer different from cholesterols Keywords: ...
TY - JOUR. T1 - Asymmetric phospholipid. T2 - Lipopolysaccharide bilayers; a Gram-negative bacterial outer membrane mimic. AU - Clifton, Luke A.. AU - Skoda, Maximilian W. A.. AU - Daulton, Emma L.. AU - Hughes, Arwel V.. AU - Le Brun, Anton P.. AU - Lakey, Jeremy. H.. AU - Holt, Stephen A.. PY - 2013/12/6. Y1 - 2013/12/6. N2 - The Gram-negative bacterial outer membrane (OM) is a complex and highly asymmetric biological barrier but the small size of bacteria has hindered advances in in vivo examination of membrane dynamics. Thus, model OMs, amenable to physical study, are important sources of data. Here, we present data from asymmetric bilayers which emulate the OM and are formed by a simple two-step approach. The bilayers were deposited on an SiO2 surface by Langmuir-Blodgett deposition of phosphatidylcholine as the inner leaflet and, via Langmuir-Schaefer deposition, an outer leaflet of either Lipid A or Escherichia coli rough lipopolysaccharides (LPS). The membranes were examined using ...
abstract = Monoterpenes are abundant in essential oil extracted from plants. These relatively small and hydrophobic molecules have shown many important biological fucntions, including antimicrobial activity and membrane penetration enhancement. The interaction between the monoterpenes and lipid bilayers is considered important to the understanding of the biological functions of monoterpenes. In this study we investigate the effect of cyclic and linear monoterpenes on the structure and dynamics of lipids in model membrane. We study the ternary system 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) - monoterpene - water as a model with a focus on dehydrated conditions. By combining complementary techniques, including differential scanning calorimetry (DSC), solid-state nuclear magnetic resonance (ss NMR) and small and wide angle X-ray scattering (SAXS and WAXS), bilayer structure, phase transitions and lipid molecular dynamics are investigated at different water contents. Monoterpenes cause ...
P.838 right column 3rd paragraph: The number of all phospholipid and cholesterol molecules per vesicle was calculated to be approximately 7000 and 5600, respectively, with hexosylceramides and gangliosides making only a relatively minor contribution (Table 2). Considering that a single phospholipid molecule occupies a space of approximately 65 Å^2 (0.65 nm^2) (primary source), 7000 phospholipids would build a planar bilayer of 4550 nm^2, i.e., 50% of the outer and inner surfaces of a vesicle possessing an outer diameter of 42 nm ...
Biological membranes define not only the cell boundaries but any compartment within the cell. To some extent, the functionality of membranes is related to the elastic properties of the lipid bilayer and the mechanical and hydrophobic matching with functional membrane proteins. Supported lipid bilayers (SLBs) are valid biomimetic systems for the study of membrane biophys-ical properties. Here, we acquired high-resolution topographic and quantitative mechanics data of phase-separated SLBs using a recent atomic force microscopy (AFM) imaging mode based on force measurements. This technique allows us to quantitatively map at high resolution the mechanical differences of lipid phases at different loading forces. We have applied this approach to evaluate the contribution of the underlying hard support in the determination of the elastic properties of SLBs and to determine the adequate indentation range for obtaining reliable elastic moduli values. At ~200 pN, elastic forces dominated the force-indentation
A study of voltage fluctuations in bilayer lipid membranes during electroporation and under current-clamp conditions is presented. Qualitative considerations based on the electroporation theory are used in order to explain the phenomenon on long time scale. Indeed, the current-clamp condition induces a feedback mechanism on the pore formation and therefore on the macroscopic conductance. Voltage fluctuations can thus be recorded. These fluctuations are nonstationary long-living and have a flicker power spectrum over nearly four decades of frequency between about 10-2 and 102Hz. The study of the fluctuations in the time domain has been performed by introducing an electrical model of the system formed by the membrane and the circuit under current-clamp configuration. The analysis of the time series gives a characteristic time of 100ms for the circuitry response to the fragments of electroporation signals with characteristic times faster than 100ms. During electroporation, the response to an ...
Page contains details about PLGA nanocapsules coated with phosphatidylcholine bilayer . It has composition images, properties, Characterization methods, synthesis, applications and reference articles : nano.nature.com
Two-dimensional gel electrophoresis was used to identify heat-modifiable outer membrane proteins, which were candidates for porins, from Helicobacter pylori membrane preparations. Four such proteins with apparent molecular masses of 48, 49, 50, and 67 kDa were isolated. The four proteins copurified together after selective detergent solubilizations followed by anion-exchange chromatography, and each protein was ultimately purified to homogeneity by gel purification. These proteins were then tested for pore-forming ability with a planar lipid bilayer model membrane system. All four proteins appeared to be present as monomers, and they formed pores with low single-channel conductances in 1.0 M KCl of 0.36, 0.36, 0.30, and 0.25 nS, respectively, for the 48-, 49-, 50-, and 67-kDa proteins which we propose to designate HopA, HopB, HopC, and HopD. N-terminal amino acid sequence analyses showed a high degree of homology among all four proteins, and it appears that these proteins constitute a family of ...
We explore this process through modeling the wrapping of a spherical particle by a model bilayer membrane, using coarse-grained molecular dynamics simulations and a theoretical elastic model. Specifically, we study the kinetics and morphologies of wrapping as a function of the relevant system parameters, including the particle radius, the strength of the membrane-particle interaction, and the membrane bending rigidity. The theoretical model predicts a phase diagram as a function of the system parameters, which is compared to results of the dynamics simulations ...
Dive into the research topics of Softening of membrane bilayers by detergents elucidated by deuterium NMR spectroscopy. Together they form a unique fingerprint. ...
Over the last 25 years one of us (WKS) has been investigating physical properties of lipid bilayer membranes. In 1991 a group led by WKS was organized into the Laboratory of Structure and Dynamics of Biological Membranes, the effective member of which is AW. Using mainly the electron paramagnetic resonance (EPR) spin-labeling method, we obtained unexpected results, which are significant for the better understanding of the functioning of biological membranes. We have developed a new pulse EPR spin-labeling method for the detection of membrane domains and evaluation of lipid exchange rates. This review will be focused on our main results which can be summarized as follows: (1) Unsaturation of alkyl chains greatly reduces the ordering and rigidifying effects of cholesterol although the unsaturation alone gives only minor fluidizing effects, as observed by order and reorientational motion, and rather significant rigidifying effects, as observed by translational motion of probe molecules; (2) ...
The interaction between lipid bilayers in water has been intensively studied over the last decades. Osmotic stress was applied to evaluate the forces between two approaching lipid bilayers in aqueous solution. The force-distance relation between lipid mono- or bilayers deposited on mica sheets using a surface force apparatus (SFA) was also measured. Lipid stabilised foam films offer another possibility to study the interactions between lipid monolayers. These films can be prepared comparatively easy with very good reproducibility. Foam films consist usually of two adsorbed surfactant monolayers separated by a layer of the aqueous solution from which the film is created. Their thickness can be conveniently measured using microinterferometric techniques. Studies with foam films deliver valuable information on the interactions between lipid membranes and especially their stability and permeability. Presenting inverse black lipid membrane (BLM) foam films supply information about the properties of ...
The interaction between lipid bilayers in water has been intensively studied over the last decades. Osmotic stress was applied to evaluate the forces between two approaching lipid bilayers in aqueous solution. The force-distance relation between lipid mono- or bilayers deposited on mica sheets using a surface force apparatus (SFA) was also measured. Lipid stabilised foam films offer another possibility to study the interactions between lipid monolayers. These films can be prepared comparatively easy with very good reproducibility. Foam films consist usually of two adsorbed surfactant monolayers separated by a layer of the aqueous solution from which the film is created. Their thickness can be conveniently measured using microinterferometric techniques. Studies with foam films deliver valuable information on the interactions between lipid membranes and especially their stability and permeability. Presenting inverse black lipid membrane (BLM) foam films supply information about the properties of ...
Phospholipids are essential building blocks of biological membranes. Despite a vast amount of very accurate experimental data, the atomistic resolution structures sampled by the glycerol backbone and choline headgroup in phoshatidylcholine bilayers are not known. Atomistic resolution molecular dynamics simulations have the potential to resolve the structures, and to give an arrestingly intuitive interpretation of the experimental data, but only if the simulations reproduce the data within experimental accuracy. In the present work, we simulated phosphatidylcholine (PC) lipid bilayers with 13 different atomistic models, and compared simulations with NMR experiments in terms of the highly structurally sensitive C-H bond vector order parameters. Focusing on the glycerol backbone and choline headgroups, we showed that the order parameter comparison can be used to judge the atomistic resolution structural accuracy of the models. Accurate models, in turn, allow molecular dynamics simulations to be used as an
Discrete-continuous hybrid models are a popular means for describing elastic membrane-mediated particle interactions in and on lipid bilayers. Here, the continuous part is usually given by an approximation of the lipid membrane by an infinitely thin and sufficiently smooth hypersurface, whose elastic energy is determined by a Canham-Helfrich type functional. The discrete component results from modeling non-membrane particles as rigid discrete entities, which, depending on their configuration, induce local constraints on the membrane along the membrane-particle interfaces. In this context, the interaction potential describes the optimal elastic energy of such hybrid systems with a fixed particle configuration. Correspondingly, the energy minimization principle yields that stationary particle configurations are given by the local minima of the interaction potential. The main goal of this work is the proof of differentiability of the interaction potential for a selected class of models. This is ...
Abstract The capsaicin and mustard oil receptors TRPV1 and TRPA1, respectively, are highly expressed in polymodal nociceptors, ubiquitous thin nerve fibers that can evoke pain and induce neurogenic inflammation by neuropeptide secretion. Reversible oxidation of intracellular cysteine residues of these channel proteins causes activation and sensitization to adequate stimuli. The ion channel activity can be assessed in cultured sensory neurons, transfected cell lines, and in artificial lipid bilayers, using patch-clamp recording, calcium microfluorimetry, and indirectly by single-fiber recording and enzyme immunoassay measurement of stimulated neuropeptide (CGRP) release from isolated organ preparations. Strikingly, we found that ordinary blue light (405 nm) activates human TRPA1 and evokes pain in white human skin. This results from the ubiquitous presence of the heme precursor protoporphyrin IX (Pp IX) that acts as a chromophore to produce singlet oxygen under illumination. The ensuing ...
Abstract: Droplet interface bilayers are a convenient model system to study the physio-chemical properties of phospholipid bilayers, the major component of the cell membrane. The mechanical response of these bilayers to various external mechanical stimuli is an active area of research due to implications for cellular viability and development of artificial cells. In this manuscript we characterize the separation mechanics of droplet interface bilayers under step strain using a combination of experiments and numerical modeling. Initially, we show that the bilayer surface energy can be obtained using principles of energy conservation. Subsequently, we subject the system to a step strain by separating the drops in a step wise manner, and track the evolution of the bilayer contact angle and radius. The relaxation time of the bilayer contact angle and radius, along with the decay magnitude of the bilayer radius were observed to increase with each separation step. By analyzing the forces acting on the ...
The study of membrane proteins (MPs) remains a major challenge in protein biochemistry mainly because of problems of protein aggregation and thermal instability in nonnative preparations of MPs in detergents, or native-like but insoluble preparations in liposomes. As a result, nonconventional surfactants with properties intermediate to lipids and detergents are becoming increasingly popular as alternative platforms for MPs (Bayburt and Sligar, 2002; Boldog et al., 2006; Park et al., 2007; Dalal et al., 2009; Popot, 2010). Discoidal lipoproteins, which include reconstituted high-density lipoprotein particles, nanodiscs, and nanoscale apolipoprotein-bound bilayers (NABBs), constitute a type of nonconventional platform that has enabled novel assays on MPs sequestered in a well-defined, soluble native-like lipid environment, such as single-particle imaging, surface plasmon resonance, nuclear magnetic resonance, and surface-enhanced infrared absorption spectroscopy (Banerjee et al., 2008; Das et al., ...
Model of nanoscale deformation mechanisms of cellular structures could render different results depending on the molecular dynamics (MD) simulator chosen. Also, the comparison of different MD simulators is typically an intricate task, requiring all configurations be converted appropriately with available parameter choices. This study aims to perform and compare MD simulations between two MD programs (GROMACS and LAMMPS), in which a phospholipid bilayer is deformed under different strain states. The two systems produced similar deformation behaviors and strain state effect on bilayer failure. However, GROMACS produced more pores at lower strains, lower stress, and higher damage values. Multiple setting options and algorithm variations have been considered as possible explanations for the differences. Overall, the study aids in the cross-check of parameter settings and simulation results in MD research, particularly on the mechanical damage of bilayer membranes. Besides, based on that, GROMACS and LAMMPS
Abstract: The activity of antimicrobial peptides stems from their interaction with bacterial membranes, which are disrupted according to a number of proposed mechanisms. Here, we investigate the interaction of a model antimicrobial peptide that contains a single arginine residue with vesicles containing model lipid membranes. The surfactant-like peptide Ala6-Arg (A6R) is studied in the form where both termini are capped (CONH-A6R-NH2, capA6R) or uncapped (NH2-A6R-OH, A6R). Lipid membranes are selected to correspond to model anionic membranes (POPE/POPG) resembling those in bacteria or model zwitterionic membranes (POPC/DOPC) similar to those found in mammalian cells. Viable antimicrobial agents should show activity against anionic membranes but not zwitterionic membranes. We find, using small-angle X-ray scattering (SAXS) and cryogenic-TEM (transmission electron microscopy) that, uniquely, capA6R causes structuring of anionic membranes due to the incorporation of the peptide in the lipid bilayer ...