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McMaster, Christopher R. « Lipid metabolism and vesicle trafficking : More than just greasing the transport machinery ». Biochemistry and Cell Biology 79, no 6 (1 décembre 2001) : 681–92. http://dx.doi.org/10.1139/o01-139.
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The movement of lipids from their sites of synthesis to ultimate intracellular destinations must be coordinated with lipid metabolic pathways to ensure overall lipid homeostasis is maintained. Thus, lipids would be predicted to play regulatory roles in the movement of vesicles within cells. Recent work has highlighted how specific lipid metabolic events can affect distinct vesicle trafficking steps and has resulted in our first glimpses of how alterations in lipid metabolism participate in the regulation of intracellular vesicles. Specifically, (i) alterations in sphingolipid metabolism affect the ability of SNAREs to fuse membranes, (ii) sterols are required for efficient endocytosis, (iii) glycerophospholipids and phosphorylated phosphatidylinositols regulate Golgi-mediated vesicle transport, (iv) lipid acylation is required for efficient vesicle transport mediated membrane fission, and (v) the addition of glycosylphosphatidylinositol lipid anchors to proteins orders them into distinct domains that result in their preferential sorting from other vesicle destined protein components in the endoplasmic reticulum. This review describes the experimental evidence that demonstrates a role for lipid metabolism in the regulation of specific vesicle transport events.Key words: vesicle transport, trafficking, lipid, sterol, metabolism.
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Bar, Laure, George Cordoyiannis, Shova Neupane, Jonathan Goole, Patrick Grosfils et Patricia Losada-Pérez. « Asymmetric Lipid Transfer between Zwitterionic Vesicles by Nanoviscosity Measurements ». Nanomaterials 11, no 5 (22 avril 2021) : 1087. http://dx.doi.org/10.3390/nano11051087.
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The interest in nano-sized lipid vesicles in nano-biotechnology relies on their use as mimics for endosomes, exosomes, and nanocarriers for drug delivery. The interactions between nanoscale size lipid vesicles and cell membranes involve spontaneous interbilayer lipid transfer by several mechanisms, such as monomer transfer or hemifusion. Experimental approaches toward monitoring lipid transfer between nanoscale-sized vesicles typically consist of transfer assays by fluorescence microscopy requiring the use of labels or calorimetric measurements, which in turn require a large amount of sample. Here, the capability of a label-free surface-sensitive method, quartz crystal microbalance with dissipation monitoring (QCM-D), was used to monitor lipid transfer kinetics at minimal concentrations and to elucidate how lipid physicochemical properties influence the nature of the transfer mechanism and dictate its dynamics. By studying time-dependent phase transitions obtained from nanoviscosity measurements, the transfer rates (unidirectional or bidirectional) between two vesicle populations consisting of lipids with the same head group and differing alkyl chain length can be estimated. Lipid transfer is asymmetric and unidirectional from shorter-chain lipid donor vesicles to longer-chain lipid acceptor vesicles. The transfer is dramatically reduced when the vesicle populations are incubated at temperatures below the melting of one of the vesicle populations.
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Salac, David, et Michael J. Miksis. « Reynolds number effects on lipid vesicles ». Journal of Fluid Mechanics 711 (31 août 2012) : 122–46. http://dx.doi.org/10.1017/jfm.2012.380.
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AbstractVesicles exposed to the human circulatory system experience a wide range of flows and Reynolds numbers. Previous investigations of vesicles in fluid flow have focused on the Stokes flow regime. In this work the influence of inertia on the dynamics of a vesicle in a shearing flow is investigated using a novel level-set computational method in two dimensions. A detailed analysis of the behaviour of a single vesicle at finite Reynolds number is presented. At low Reynolds numbers the results recover vesicle behaviour previously observed for Stokes flow. At moderate Reynolds numbers the classical tumbling behaviour of highly viscous vesicles is no longer observed. Instead, the vesicle is observed to tank-tread, with an equilibrium angle dependent on the Reynolds number and the reduced area of the vesicle. It is shown that a vesicle with an inner/outer fluid viscosity ratio as high as 200 will not tumble if the Reynolds number is as low as 10. A new damped tank-treading behaviour, where the vesicle will briefly oscillate about the equilibrium inclination angle, is also observed. This behaviour is explained by an investigation on the torque acting on a vesicle in shear flow. Scaling laws for vesicles in inertial flows have also been determined. It is observed that quantities such as vesicle tumbling period follow square-root scaling with respect to the Reynolds number. Finally, the maximum tension as a function of the Reynolds number is also determined. It is observed that, as the Reynolds number increases, the maximum tension on the vesicle membrane also increases. This could play a role in the creation of stable pores in vesicle membranes or for the premature destruction of vesicles exposed to the human circulatory system.
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Yu, Haijia, Yinghui Liu, Daniel R. Gulbranson, Alex Paine, Shailendra S. Rathore et Jingshi Shen. « Extended synaptotagmins are Ca2+-dependent lipid transfer proteins at membrane contact sites ». Proceedings of the National Academy of Sciences 113, no 16 (4 avril 2016) : 4362–67. http://dx.doi.org/10.1073/pnas.1517259113.
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Organelles are in constant communication with each other through exchange of proteins (mediated by trafficking vesicles) and lipids [mediated by both trafficking vesicles and lipid transfer proteins (LTPs)]. It has long been known that vesicle trafficking can be tightly regulated by the second messenger Ca2+, allowing membrane protein transport to be adjusted according to physiological demands. However, it remains unclear whether LTP-mediated lipid transport can also be regulated by Ca2+. In this work, we show that extended synaptotagmins (E-Syts), poorly understood membrane proteins at endoplasmic reticulum–plasma membrane contact sites, are Ca2+-dependent LTPs. Using both recombinant and endogenous mammalian proteins, we discovered that E-Syts transfer glycerophospholipids between membrane bilayers in the presence of Ca2+. E-Syts use their lipid-accommodating synaptotagmin-like mitochondrial lipid binding protein (SMP) domains to transfer lipids. However, the SMP domains themselves cannot transport lipids unless the two membranes are tightly tethered by Ca2+-bound C2 domains. Strikingly, the Ca2+-regulated lipid transfer activity of E-Syts was fully recapitulated when the SMP domain was fused to the cytosolic domain of synaptotagmin-1, the Ca2+ sensor in synaptic vesicle fusion, indicating that a common mechanism of membrane tethering governs the Ca2+ regulation of lipid transfer and vesicle fusion. Finally, we showed that microsomal vesicles isolated from mammalian cells contained robust Ca2+-dependent lipid transfer activities, which were mediated by E-Syts. These findings established E-Syts as a novel class of LTPs and showed that LTP-mediated lipid trafficking, like vesicular transport, can be subject to tight Ca2+ regulation.
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Kisak, E., M. Kennedy et J. A. Zasadzinski. « Self-Limiting Aggregation By Controlled Ligand-Receptor Stoicfflometry and Its Use For a Novel Drug Delivery System ». Microscopy and Microanalysis 5, S2 (août 1999) : 1212–13. http://dx.doi.org/10.1017/s1431927600019383.
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Lipid vesicles are used as drug delivery vehicles for the slow sustained release of a drug compound to a specific site in the body. This translates to more efficient medication with limited side effects. Although unilamellar drug delivery vesicles have progressed greatly, they are still limited in there applications. Our group has designed a second generation drug release system, the “vesosome“ which incorporates an aggregate of lipid vesicles encapsulated in a second lipid membrane. The two separate membranes can be specialized to allow for increased drug encapsulation and better control over drug release rate, which leads to a more general drug delivery system.Lipid vesicle aggregates were formed by using a ligand-receptor system (biotinated lipids protruding from the vesicle surface crosslinked with streptavidin). The streptavidin/biotin system is one of the strongest in nature, providing specific binding.
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Willes, Keith L., Jasmyn R. Genchev et Walter F. Paxton. « Hybrid Lipid-Polymer Bilayers : pH-Mediated Interactions between Hybrid Vesicles and Glass ». Polymers 12, no 4 (28 mars 2020) : 745. http://dx.doi.org/10.3390/polym12040745.
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One practical approach towards robust and stable biomimetic platforms is to generate hybrid bilayers that incorporate both lipids and block co-polymer amphiphiles. The currently limited number of reports on the interaction of glass surfaces with hybrid lipid and polymer vesicles—DOPC mixed with amphiphilic poly(ethylene oxide-b-butadiene) (PEO-PBd)—describe substantially different conclusions under very similar conditions (i.e., same pH). In this study, we varied vesicle composition and solution pH in order to generate a broader picture of spontaneous hybrid lipid/polymer vesicle interactions with rigid supports. Using quartz crystal microbalance with dissipation (QCM-D), we followed the interaction of hybrid lipid-polymer vesicles with borosilicate glass as a function of pH. We found pH-dependent adsorption/fusion of hybrid vesicles that accounts for some of the contradictory results observed in previous studies. Our results show that the formation of hybrid lipid-polymer bilayers is highly pH dependent and indicate that the interaction between glass surfaces and hybrid DOPC/PEO-PBd can be tuned with pH.
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Cummings, Jason E., Donald P. Satchell, Yoshinori Shirafuji, Andre J. Ouellette et T. Kyle Vanderlick. « Electrostatically Controlled Interactions of Mouse Paneth Cell α-Defensins with Phospholipid Membranes ». Australian Journal of Chemistry 56, no 10 (2003) : 1031. http://dx.doi.org/10.1071/ch03110.
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Antimicrobial peptides of the innate immune systems of many organisms are known to interact with lipid membranes, with electrostatic interactions playing an important role. We have studied the interactions of the mouse α-defensin, cryptdin-4, and its precursor, procryptdin-4, with phospholipid model membranes in the form of vesicles. Both peptides induce ‘graded’ leakage of vesicle contents, however procryptdin-4 exhibits only minimal membrane disruptive activity. Vesicles containing a higher fraction of anionic lipid are more susceptible to peptide-induced leakage. Electrophoretic mobility measurements at several vesicle compositions reveal a correlation between the surface potential of vesicles and the peptide-induced vesicle leakage.
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Kamiya, Koki, Toshihisa Osaki et Shoji Takeuchi. « Formation of vesicles-in-a-vesicle with asymmetric lipid components using a pulsed-jet flow method ». RSC Advances 9, no 52 (2019) : 30071–75. http://dx.doi.org/10.1039/c9ra04622d.
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Miyamaru, Chiho, Mao Koide, Nana Kato, Shogo Matsubara et Masahiro Higuchi. « Fabrication of CaCO3-Coated Vesicles by Biomineralization and Their Application as Carriers of Drug Delivery Systems ». International Journal of Molecular Sciences 23, no 2 (12 janvier 2022) : 789. http://dx.doi.org/10.3390/ijms23020789.
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We fabricated CaCO3-coated vesicles as drug carriers that release their cargo under a weakly acidic condition. We designed and synthesized a peptide lipid containing the Val-His-Val-Glu-Val-Ser sequence as the hydrophilic part, and with two palmitoyl groups at the N-terminal as the anchor groups of the lipid bilayer membrane. Vesicles embedded with the peptide lipids were prepared. The CaCO3 coating of the vesicle surface was performed by the mineralization induced by the embedded peptide lipid. The peptide lipid produced the mineral source, CO32−, for CaCO3 mineralization through the hydrolysis of urea. We investigated the structure of the obtained CaCO3-coated vesicles using transmission electron microscopy (TEM). The vesicles retained the spherical shapes, even in vacuo. Furthermore, the vesicles had inner spaces that acted as the drug cargo, as observed by the TEM tomographic analysis. The thickness of the CaCO3 shell was estimated as ca. 20 nm. CaCO3-coated vesicles containing hydrophobic or hydrophilic drugs were prepared, and the drug release properties were examined under various pH conditions. The mineralized CaCO3 shell of the vesicle surface was dissolved under a weakly acidic condition, pH 6.0, such as in the neighborhood of cancer tissues. The degradation of the CaCO3 shell induced an effective release of the drugs. Such behavior suggests potential of the CaCO3-coated vesicles as carriers for cancer therapies.
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Cohen, D. E., M. Angelico et M. C. Carey. « Quasielastic light scattering evidence for vesicular secretion of biliary lipids ». American Journal of Physiology-Gastrointestinal and Liver Physiology 257, no 1 (1 juillet 1989) : G1—G8. http://dx.doi.org/10.1152/ajpgi.1989.257.1.g1.
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We employed quasielastic light scattering, negative-stain, and freeze-fracture electron microscopy to study the time-dependent physicochemical behavior of biliary lipids in fresh rat bile. Three to five minutes after bile collection, the earliest light scattering measurements and electron microscopy revealed unilamellar vesicles (mean hydrodynamic radius, Rh = 430-740 A) coexisting with mixed micelles (Rh = 20-120 A) in all biles. Both percent biliary vesicles (1 to greater than 70%) and micellar sizes varied inversely with bile salt concentration (range 1.6-72 mM) both during endogenous pool drainage and sodium taurocholate infusion. With bile salt concentrations in the vicinity of or below the estimated critical micellar concentration, biliary vesicle concentrations remained constant or increased slightly with passage of time. However, with micellar bile salt concentrations, complete conversion of vesicles to micelles occurred at rates that were directly proportional to bile salt concentration. Back-extrapolation of weighted Rh averages of micelles plus vesicles as functions of time gave sizes of approximately 470 A at 1 min, suggesting the predominance of homogeneously sized unilamellar vesicles at the earliest stages of bile formation. After micellization of lipids, mixed protein aggregates of vesicle size were demonstrated in all biles. These experiments elucidate the dynamic coexistence of lipid vesicles and mixed micelles in cholesterol unsaturated biles and demonstrate that vesicle-to-micelle interconversions of biliary lipid aggregates are normal physiological phenomena within the biliary tree.(ABSTRACT TRUNCATED AT 250 WORDS)
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Castro, Daniel C., Yuxuan Richard Xie, Stanislav S. Rubakhin, Elena V. Romanova et Jonathan V. Sweedler. « Image-guided MALDI mass spectrometry for high-throughput single-organelle characterization ». Nature Methods 18, no 10 (30 septembre 2021) : 1233–38. http://dx.doi.org/10.1038/s41592-021-01277-2.
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AbstractPeptidergic dense-core vesicles are involved in packaging and releasing neuropeptides and peptide hormones—critical processes underlying brain, endocrine and exocrine function. Yet, the heterogeneity within these organelles, even for morphologically defined vesicle types, is not well characterized because of their small volumes. We present image-guided, high-throughput mass spectrometry-based protocols to chemically profile large populations of both dense-core vesicles and lucent vesicles for their lipid and peptide contents, allowing observation of the chemical heterogeneity within and between these two vesicle populations. The proteolytic processing products of four prohormones are observed within the dense-core vesicles, and the mass spectral features corresponding to the specific peptide products suggest three distinct dense-core vesicle populations. Notable differences in the lipid mass range are observed between the dense-core and lucent vesicles. These single-organelle mass spectrometry approaches are adaptable to characterize a range of subcellular structures.
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Pranke, Iwona M., Vincent Morello, Joëlle Bigay, Kimberley Gibson, Jean-Marc Verbavatz, Bruno Antonny et Catherine L. Jackson. « α-Synuclein and ALPS motifs are membrane curvature sensors whose contrasting chemistry mediates selective vesicle binding ». Journal of Cell Biology 194, no 1 (11 juillet 2011) : 89–103. http://dx.doi.org/10.1083/jcb.201011118.
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Membrane curvature sensors have diverse structures and chemistries, suggesting that they might have the intrinsic capacity to discriminate between different types of vesicles in cells. In this paper, we compare the in vitro and in vivo membrane-binding properties of two curvature sensors that form very different amphipathic helices: the amphipathic lipid-packing sensor (ALPS) motif of a Golgi vesicle tether and the synaptic vesicle protein α-synuclein, a causative agent of Parkinson’s disease. We demonstrate the mechanism by which α-synuclein senses membrane curvature. Unlike ALPS motifs, α-synuclein has a poorly developed hydrophobic face, and this feature explains its dual sensitivity to negatively charged lipids and to membrane curvature. When expressed in yeast cells, these two curvature sensors were targeted to different classes of vesicles, those of the early secretory pathway for ALPS motifs and to negatively charged endocytic/post-Golgi vesicles in the case of α-synuclein. Through structures with complementary chemistries, α-synuclein and ALPS motifs target distinct vesicles in cells by direct interaction with different lipid environments.
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Breiden, Bernadette, et Konrad Sandhoff. « Emerging mechanisms of drug-induced phospholipidosis ». Biological Chemistry 401, no 1 (18 décembre 2019) : 31–46. http://dx.doi.org/10.1515/hsz-2019-0270.
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Abstract Drug-induced phospholipidosis is a lysosomal storage disorder characterized by excessive accumulation of phospholipids. Its cellular mechanism is still not well understood, but it is known that cationic amphiphilic drugs can induce it. These drugs have a hydrophilic amine head group that can be protonated in the endolysosomal compartment. As cationic amphiphiles, they are trapped in lysosomes, where they interfere with negatively charged intralysosomal vesicles, the major platforms of cellular sphingolipid degradation. Metabolic principles observed in sphingolipid and phospholipid catabolism and inherited sphingolipidoses are of great importance for lysosomal function and physiological lipid turnover at large. Therefore, we also propose intralysosomal vesicles as major platforms for degradation of lipids and phospholipids reaching them by intracellular pathways like autophagy and endocytosis. Phospholipids are catabolized as components of vesicle surfaces by protonated, positively charged phospholipases, electrostatically attracted to the negatively charged vesicles. Model experiments suggest that progressively accumulating cationic amphiphilic drugs inserting into the vesicle membrane with their hydrophobic molecular moieties disturb and attenuate the main mechanism of lipid degradation as discussed here. By compensating the negative surface charge, cationic enzymes are released from the surface of vesicles and proteolytically degraded, triggering a progressive lipid storage and the formation of inactive lamellar bodies.
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Walde, Peter, et Sosaku Ichikawa. « Lipid Vesicles and Other Polymolecular Aggregates—From Basic Studies of Polar Lipids to Innovative Applications ». Applied Sciences 11, no 21 (3 novembre 2021) : 10345. http://dx.doi.org/10.3390/app112110345.
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Lipid vesicles (liposomes) are a unique and fascinating type of polymolecular aggregates, obtained from bilayer-forming amphiphiles—or mixtures of amphiphiles—in an aqueous medium. Unilamellar vesicles consist of one single self-closed bilayer membrane, constituted by the amphiphiles and an internal volume which is trapped by this bilayer, whereby the vesicle often is spherical with a typical desired average diameter of either about 100 nm or tens of micrometers. Functionalization of the external vesicle surface, basically achievable at will, and the possibilities of entrapping hydrophilic molecules inside the vesicles or/and embedding hydrophobic compounds within the membrane, resulted in various applications in different fields. This review highlights a few of the basic studies on the phase behavior of polar lipids, on some of the concepts for the controlled formation of lipid vesicles as dispersed lamellar phase, on some of the properties of vesicles, and on the challenges of efficiently loading them with hydrophilic or hydrophobic compounds for use as delivery systems, as nutraceuticals, for bioassays, or as cell-like compartments. Many of the large number of basic studies have laid a solid ground for various applications of polymolecular aggregates of amphiphilic lipids, including, for example, cubosomes, bicelles or—recently most successfully—nucleic acids-containing lipid nanoparticles. All this highlights the continued importance of fundamental studies. The life-saving application of mRNA lipid nanoparticle COVID-19 vaccines is in part based on year-long fundamental studies on the formation and properties of lipid vesicles. It is a fascinating example, which illustrates the importance of considering (i) details of the chemical structure of the different molecules involved, as well as (ii) physical, (iii) engineering, (iv) biological, (v) pharmacological, and (vii) economic aspects. Moreover, the strong demand for interdisciplinary collaboration in the field of lipid vesicles and related aggregates is also an excellent and convincing example for teaching students in the field of complex molecular systems.
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Shinoda, Wataru, et Michael L. Klein. « Effective interaction between small unilamellar vesicles as probed by coarse-grained molecular dynamics simulations ». Pure and Applied Chemistry 86, no 2 (1 février 2014) : 215–22. http://dx.doi.org/10.1515/pac-2014-5023.
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Abstract A series of molecular dynamics (MD) simulations has been undertaken to investigate the effective interaction between vesicles including PC (phosphatidylcholine) and PE (phosphatidylethanolamine) lipids using the Shinoda–DeVane–Klein coarse-grained force field. No signatures of fusion were detected during MD simulations employing two apposed unilamellar vesicles, each composed of 1512 lipid molecules. Association free energy of the two stable vesicles depends on the lipid composition. The two PC vesicles exhibit a purely repulsive interaction with each other, whereas two PE vesicles show a free energy gain at the contact. A mixed PC/PE (1:1) vesicle shows a higher flexibility having a lower energy barrier on the deformation, which is caused by lipid sorting within each leaflet of the membranes. With a preformed channel or stalk between proximal membranes, PE molecules contribute to stabilize the stalk. The results suggest that the lipid components forming the membrane with a negative spontaneous curvature contribute to stabilize the stalk between two vesicles in contact.
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Friedrich, Remo, Stephan Block, Mohammadreza Alizadehheidari, Susanne Heider, Joachim Fritzsche, Elin K. Esbjörner, Fredrik Westerlund et Marta Bally. « A nano flow cytometer for single lipid vesicle analysis ». Lab on a Chip 17, no 5 (2017) : 830–41. http://dx.doi.org/10.1039/c6lc01302c.
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Devitt, Andrew, Helen R. Griffiths et Ivana Milic. « Communicating with the dead : lipids, lipid mediators and extracellular vesicles ». Biochemical Society Transactions 46, no 3 (9 mai 2018) : 631–39. http://dx.doi.org/10.1042/bst20160477.
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Apoptosis is a key event in the control of inflammation. However, for this to be successful, dying cells must efficiently and effectively communicate their presence to phagocytes to ensure timely removal of dying cells. Here, we consider apoptotic cell-derived extracellular vesicles and the role of contained lipids and lipid mediators in ensuring effective control of inflammation. We discuss key outstanding issues in the study of cell death and cell communication, and introduce the concept of the ‘active extracellular vesicle’ as a metabolically active and potentially changing intercellular communicator.
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Lai, Ying, et Yeon-Kyun Shin. « The importance of an asymmetric distribution of acidic lipids for synaptotagmin 1 function as a Ca2+ sensor ». Biochemical Journal 443, no 1 (14 mars 2012) : 223–29. http://dx.doi.org/10.1042/bj20112044.
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Syt1 (synaptotagmin 1) is a major Ca2+ sensor for synaptic vesicle fusion. Although Syt1 is known to bind to SNARE (soluble N-ethylmaleimide-sensitive fusion protein-attachment protein receptor) complexes and to the membrane, the mechanism by which Syt1 regulates vesicle fusion is controversial. In the present study we used in vitro lipid-mixing assays to investigate the Ca2+-dependent Syt1 function in proteoliposome fusion. To study the role of acidic lipids, the concentration of negatively charged DOPS (1,2-dioleoyl-sn-glycero-3-phospho-L-serine) in the vesicle was varied. Syt1 stimulated lipid mixing by 3–10-fold without Ca2+. However, with Ca2+ there was an additional 2–5-fold enhancement. This Ca2+-dependent stimulation was observed only when there was excess PS (phosphatidylserine) on the t-SNARE (target SNARE) side. If there was equal or more PS on the v-SNARE (vesicule SNARE) side the Ca2+-dependent stimulation was not observed. We found that Ca2+ at a concentration between 10 and 50 μM was sufficient to give rise to the maximal enhancement. The single-vesicle-fusion assay indicates that the Ca2+-dependent enhancement was mainly on docking, whereas its effect on lipid mixing was small. Thus for Syt1 to function as a Ca2+ sensor, a charge asymmetry appears to be important and this may play a role in steering Syt1 to productively trans bind to the plasma membrane.
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Yang, Qing, Maria Wallstén et Per Lundahl. « Lipid-vesicle-surface chromatography ». Journal of Chromatography A 506 (mai 1990) : 379–89. http://dx.doi.org/10.1016/s0021-9673(01)91593-6.
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Heller, William T., et Piotr A. Zolnierczuk. « Investigation of the Impact of Lipid Acyl Chain Saturation on Fusion Peptide Interactions with Lipid Bilayers ». Biophysica 3, no 1 (28 février 2023) : 121–38. http://dx.doi.org/10.3390/biophysica3010009.
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The interaction of many peptides with lipid bilayer membranes strongly depends on the lipid composition. Here, a study of the impact of unsaturated lipid acyl chains on the interaction of a derivative of the HIV-1 fusion peptide with lipid bilayer vesicles is presented. Lipid bilayer vesicles composed of mixtures of lipids with two saturated acyl chains and lipids and one saturated and one unsaturated acyl chain, but identical head groups, were studied. The dependence of the peptide conformation on the unsaturated lipid content was probed by circular dichroism spectroscopy, while the impact of the peptide on the bilayer structure was determined by small-angle neutron scattering. The impact of the peptide on the lipid bilayer vesicle dynamics was investigated using neutron spin echo spectroscopy. Molecular dynamics simulations were used to characterize the behavior of the systems studied to determine if there were clear differences in their physical properties. The results reveal that the peptide–bilayer interaction is not a simple function of the unsaturated lipid acyl chain content of the bilayer. Instead, the peptide behavior is more consistent with that seen for the bilayer containing only unsaturated lipids, which is supported by lipid-specific interactions revealed by the simulations.
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Almeida, Paulo F. F. « Lipid Transfer Between Vesicles : Effect of High Vesicle Concentration ». Biophysical Journal 76, no 4 (avril 1999) : 1922–28. http://dx.doi.org/10.1016/s0006-3495(99)77351-0.
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Abeysekera, R. M., William Newcomb, W. B. Silvester et John G. Torrey. « A freeze-fracture electron microscopic study of Frankia in root nodules of Alnus incana grown at three oxygen tensions ». Canadian Journal of Microbiology 36, no 2 (1 février 1990) : 97–108. http://dx.doi.org/10.1139/m90-019.
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Nodulated plants of Alnus incana ssp. rugosa and ssp. incana were grown with the roots exposed to 5, 21, and 40 kPa O2. The nodules were studied by freeze-fracture transmission electron microscopy to determine the effect of varying O2 tension on the numbers of lipid laminae in the Frankia envelope. Lipid laminae were present in the cell envelopes of hyphae, stalks, and symbiotic vesicles. The mean number of lipid laminae in hyphal envelopes varied from five to nine. Stalks of symbiotic vesicles contained mean numbers of 35–59 lipid laminae over the range of pO2's studied. Symbiotic vesicle envelopes showed mean numbers of lipid laminae varying from 48 to 94. The numbers of lipid laminae were observed to increase significantly in the distal regions of the symbiotic vesicles in response to raised pO2 while the numbers on the proximal portions remained unchanged. The increase in the numbers of lipid laminae in response to raised pO2 was not sufficient to account for the expected increase in resistance to O2 required at the symbiotic vesicle envelope if lipid laminae formed the exclusive diffusion barrier to O2. These results suggest that lipid laminae surrounding symbiotic vesicles may not constitute the only O2 protection mechanism in Alnus nodules. Key words: Alnus incana, Frankia, nitrogen fixation, actinorhizal nodules, Actinomycetes.
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Chappa, Veronica, Yuliya Smirnova, Karlo Komorowski, Marcus Müller et Tim Salditt. « The effect of polydispersity, shape fluctuations and curvature on small unilamellar vesicle small-angle X-ray scattering curves ». Journal of Applied Crystallography 54, no 2 (25 mars 2021) : 557–68. http://dx.doi.org/10.1107/s1600576721001461.
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Small unilamellar vesicles (20–100 nm diameter) are model systems for strongly curved lipid membranes, in particular for cell organelles. Routinely, small-angle X-ray scattering (SAXS) is employed to study their size and electron-density profile (EDP). Current SAXS analysis of small unilamellar vesicles (SUVs) often employs a factorization into the structure factor (vesicle shape) and the form factor (lipid bilayer electron-density profile) and invokes additional idealizations: (i) an effective polydispersity distribution of vesicle radii, (ii) a spherical vesicle shape and (iii) an approximate account of membrane asymmetry, a feature particularly relevant for strongly curved membranes. These idealizations do not account for thermal shape fluctuations and also break down for strong salt- or protein-induced deformations, as well as vesicle adhesion and fusion, which complicate the analysis of the lipid bilayer structure. Presented here are simulations of SAXS curves of SUVs with experimentally relevant size, shape and EDPs of the curved bilayer, inferred from coarse-grained simulations and elasticity considerations, to quantify the effects of size polydispersity, thermal fluctuations of the SUV shape and membrane asymmetry. It is observed that the factorization approximation of the scattering intensity holds even for small vesicle radii (∼30 nm). However, the simulations show that, for very small vesicles, a curvature-induced asymmetry arises in the EDP, with sizeable effects on the SAXS curve. It is also demonstrated that thermal fluctuations in shape and the size polydispersity have distinguishable signatures in the SAXS intensity. Polydispersity gives rise to low-q features, whereas thermal fluctuations predominantly affect the scattering at larger q, related to membrane bending rigidity. Finally, it is shown that simulation of fluctuating vesicle ensembles can be used for analysis of experimental SAXS curves.
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Somerharju, Pentti. « Is Spontaneous Translocation of Polar Lipids between Cellular Organelles Negligible ? » Lipid Insights 8s1 (janvier 2015) : LPI.S31616. http://dx.doi.org/10.4137/lpi.s31616.
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In most reviews addressing intracellular lipid trafficking, spontaneous diffusion of lipid monomers between the cellular organelles is considered biologically irrelevant because it is thought to be far too slow to significantly contribute to organelle biogenesis. This view is based on intervesicle transfer experiments carried out in vitro with few lipids as well as on the view that lipids are highly hydrophobic and thus cannot undergo spontaneous intermembrane diffusion at a significant rate. However, besides that single-chain lipids can translocate between vesicles in seconds, it has been demonstrated that the rate of spontaneous transfer of two-chain polar lipids can vary even 1000-fold, depending on the number of carbons and double bonds in the acyl chains. In addition, the rate of spontaneous lipid transfer can strongly depend on the experimental conditions such as vesicle composition and concentration. This review examines the studies suggesting that spontaneous lipid transfer is probably more relevant to intracellular trafficking of amphipathic lipids than commonly thought.
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RISKE, KARIN A., NATALYA BEZLYEPKINA, REINHARD LIPOWSKY et RUMIANA DIMOVA. « ELECTROFUSION OF MODEL LIPID MEMBRANES VIEWED WITH HIGH TEMPORAL RESOLUTION ». Biophysical Reviews and Letters 01, no 04 (octobre 2006) : 387–400. http://dx.doi.org/10.1142/s179304800600032x.
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The interaction of electric fields with lipid membranes and cells has been extensively studied in the last decades. The phenomena of electroporation and electrofusion are of particular interest because of their widespread use in cell biology and biotechnology. Giant vesicles, being of cell size and convenient for microscopy observations, are the simplest model of the cell membrane. However, optical microscopy observation of effects caused by electric DC pulses on giant vesicles is difficult because of the short duration of the pulse. Recently this difficulty has been overcome in our lab. Using a digital camera with high temporal resolution, we were able to access vesicle fusion dynamics on a sub-millisecond time scale. In this report, we present some observations on electrodeformation and –poration of single vesicles followed by an extensive study on the electrofusion of vesicle couples. Finally, we suggest an attractive approach for creating multidomain vesicles using electrofusion and present some preliminary results on the effect of membrane stiffness on the fusion dynamics.
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Mikucki, Michael, et Yongcheng Zhou. « Fast Simulation of Lipid Vesicle Deformation Using Spherical Harmonic Approximation ». Communications in Computational Physics 21, no 1 (5 décembre 2016) : 40–64. http://dx.doi.org/10.4208/cicp.oa-2015-0029.
Texte intégralRésumé :
AbstractLipid vesicles appear ubiquitously in biological systems. Understanding how the mechanical and intermolecular interactions deform vesicle membranes is a fundamental question in biophysics. In this article we develop a fast algorithm to compute the surface configurations of lipid vesicles by introducing surface harmonic functions to approximate themembrane surface. This parameterization allows an analytical computation of the membrane curvature energy and its gradient for the efficient minimization of the curvature energy using a nonlinear conjugate gradient method. Our approach drastically reduces the degrees of freedom for approximating the membrane surfaces compared to the previously developed finite element and finite difference methods. Vesicle deformations with a reduced volume larger than 0.65 can be well approximated by using as small as 49 surface harmonic functions. The method thus has a great potential to reduce the computational expense of tracking multiple vesicles which deform for their interaction with external fields.
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Brzustowicz, Michael R., et Axel T. Brunger. « X-ray scattering from unilamellar lipid vesicles ». Journal of Applied Crystallography 38, no 1 (19 janvier 2005) : 126–31. http://dx.doi.org/10.1107/s0021889804029206.
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An improved small-angle X-ray scattering (SAXS) method for determining asymmetric lipid bilayer structure in unilamellar vesicles is presented. From scattering theory, analytic expressions are derived for the bilayer form factor over flat and spherical geometries, assuming the lipid bilayer electron density to be composed of a series of Gaussian shells. This is in contrast to both classic diffraction and Guinier hard-shell SAXS methods which, respectively, are capable only of ascertaining symmetric bilayer structure and limited-resolution asymmetric structure. Using model fitting and direct calculation of the form factor, using only one equation, an asymmetric electron density profile of the lipid vesicle is obtained with high accuracy, as well as the average radius. The analysis suggests that the inner leaflet of a unilamellar lipid vesicle is `rougher' than the outer one.
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Ellis, Terri N., Sara A. Leiman et Meta J. Kuehn. « Naturally Produced Outer Membrane Vesicles from Pseudomonas aeruginosa Elicit a Potent Innate Immune Response via Combined Sensing of Both Lipopolysaccharide and Protein Components ». Infection and Immunity 78, no 9 (6 juillet 2010) : 3822–31. http://dx.doi.org/10.1128/iai.00433-10.
Texte intégralRésumé :
ABSTRACT Pseudomonas aeruginosa is a prevalent opportunistic human pathogen that, like other Gram-negative pathogens, secretes outer membrane vesicles. Vesicles are complex entities composed of a subset of envelope lipid and protein components that have been observed to interact with and be internalized by host cells. This study characterized the inflammatory responses to naturally produced P. aeruginosa vesicles and determined the contribution of vesicle Toll-like receptor (TLR) ligands and vesicle proteins to that response. Analysis of macrophage responses to purified vesicles by real-time PCR and enzyme-linked immunosorbent assay identified proinflammatory cytokines upregulated by vesicles. Intact vesicles were shown to elicit a profoundly greater inflammatory response than the response to purified lipopolysaccharide (LPS). Both TLR ligands LPS and flagellin contributed to specific vesicle cytokine responses, whereas the CpG DNA content of vesicles did not. Neutralization of LPS sensing demonstrated that macrophage responses to the protein composition of vesicles required the adjuvantlike activity of LPS to elicit strain specific responses. Protease treatment to remove proteins from the vesicle surface resulted in decreased interleukin-6 and tumor necrosis factor alpha production, indicating that the production of these specific cytokines may be linked to macrophage recognition of vesicle proteins. Confocal microscopy of vesicle uptake by macrophages revealed that vesicle LPS allows for binding to macrophage surfaces, whereas vesicle protein content is required for internalization. These data demonstrate that macrophage sensing of both LPS and protein components of outer membrane vesicles combine to produce a bacterial strain-specific response that is distinct from those triggered by individual, purified vesicle components.
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Harris, H. W., M. L. Zeidel et C. Hosselet. « Quantitation and topography of membrane proteins in highly water-permeable vesicles from ADH-stimulated toad bladder ». American Journal of Physiology-Cell Physiology 261, no 1 (1 juillet 1991) : C143—C153. http://dx.doi.org/10.1152/ajpcell.1991.261.1.c143.
Texte intégralRésumé :
Antidiuretic hormone (ADH) stimulation of toad bladder granular cells rapidly increases the osmotic water permeability (Pf) of their apical membranes by insertion of highly selective water channels. Before ADH stimulation, these water channels are stored in large cytoplasmic vesicles called aggrephores. ADH causes aggrephores to fuse with the apical membrane. Termination of ADH stimulation results in prompt endocytosis of water channel-containing membranes via retrieval of these specialized regions of apical membrane. Protein components of the ADH water channel contained within these retrieved vesicles would be expected to be integral membrane protein(s) that span the vesicle's lipid bilayer to create narrow aqueous channels. Our previous work has identified proteins of 55 (actually a 55/53-kDa doublet), 17, 15, and 7 kDa as candidate ADH water channel components. We now have investigated these candidate ADH water channel proteins in purified retrieved vesicles. These vesicles do not contain a functional proton pump as assayed by Western blots of purified vesicle protein probed with anti-H(+)-ATPase antisera. Approximately 60% of vesicle protein is accounted for by three protein bands of 55, 53, and 46 kDa. Smaller contributions to vesicle protein are made by the 17- and 15-kDa proteins. Triton X-114-partitioning analysis shows that the 55, 53, 46, and 17 kDa are integral membrane proteins. Vectorial labeling analysis with two membrane-impermeant reagents shows that the 55-, 53-, and 46-kDa protein species span the lipid bilayer of these vesicles. Thus the 55-, 53-, and 46-kDa proteins possess characteristics expected for ADH water channel components. These data show that the 55- and 53- and perhaps the 46-, 17-, and 15-kDa proteins are likely components of aqueous transmembrane pores that constitute ADH water channels contained within these vesicles.
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Marmottant, Philippe, Thierry Biben et Sascha Hilgenfeldt. « Deformation and rupture of lipid vesicles in the strong shear flow generated by ultrasound-driven microbubbles ». Proceedings of the Royal Society A : Mathematical, Physical and Engineering Sciences 464, no 2095 (25 mars 2008) : 1781–800. http://dx.doi.org/10.1098/rspa.2007.0362.
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Considering the elastic response of the membrane of a lipid vesicle (artificial cell) in an arbitrary three-dimensional shear flow, we derive analytical predictions of vesicle shape and membrane tension for vesicles close to a spherical shape. Large amplitude deviations from sphericity are described using boundary integral numerical simulations. Two possible modes of vesicle rupture are found and compared favourably with experiments: (i) for large enough shear rates the tension locally exceeds a rupture threshold and a pore opens at the waist of the vesicle and (ii) for large elongations the local tension becomes negative, leading to buckling and tip formation near a pole of the vesicle. We experimentally check these predictions in the case of strong acoustic streaming flow generated near ultrasound-driven microbubbles, such as those used in medical applications.
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Mareš, Tomáš, Matej Daniel, Aleš Iglič, Veronika Kralj-Iglič et Miha Fošnarič. « Determination of the Strength of Adhesion between Lipid Vesicles ». Scientific World Journal 2012 (2012) : 1–6. http://dx.doi.org/10.1100/2012/146804.
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A commonly used method to determine the strength of adhesion between adhering lipid vesicles is measuring their effective contact angle from experimental images. The aim of this paper is to estimate the interobserver variations in vesicles effective contact angle measurements and to propose a new method for estimating the strength of membrane vesicle adhesion. Theoretical model shows for the old and for the new measure a monotonic dependence on the strength of adhesion. Results obtained by both measuring techniques show statistically significant correlation and high interobserver reliability for both methods. Therefore the conventional method of measuring the effective contact angle gives qualitatively relevant results as the measure of the lipid vesicle adhesion. However, the new measuring technique provides a lower variation of the measured values than the conventional measures using the effective contact angle. Moreover, obtaining the adhesion angle can be automatized more easily than obtaining the effective contact angle.
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Swana, Kathleen W., Terri A. Camesano et Ramanathan Nagarajan. « Formation of a Fully Anionic Supported Lipid Bilayer to Model Bacterial Inner Membrane for QCM-D Studies ». Membranes 12, no 6 (27 mai 2022) : 558. http://dx.doi.org/10.3390/membranes12060558.
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Supported lipid bilayers (SLBs) on quartz crystals are employed as versatile model systems for studying cell membrane behavior with the use of the highly sensitive technique of quartz crystal microbalance with dissipation monitoring (QCM-D). Since the lipids constituting cell membranes vary from predominantly zwitterionic lipids in mammalian cells to predominantly anionic lipids in the inner membrane of Gram-positive bacteria, the ability to create SLBs of different lipid compositions is essential for representing different cell membranes. While methods to generate stable zwitterionic SLBs and zwitterionic-dominant mixed zwitterionic–anionic SLBs on quartz crystals have been well established, there are no reports of being able to form predominantly or fully anionic SLBs. We describe here a method for forming entirely anionic SLBs by treating the quartz crystal with cationic (3-aminopropyl) trimethoxysilane (APTMS). The formation of the anionic SLB was tracked using QCM-D by monitoring the adsorption of anionic lipid vesicles to a quartz surface and subsequent bilayer formation. Anionic egg L-α-phosphatidylglycerol (PG) vesicles adsorbed on the surface-treated quartz crystal, but did not undergo the vesicle-to-bilayer transition to create an SLB. However, when PG was mixed with 10–40 mole% 1-palmitoyl-2-hydroxy-sn-glycero-3-phospho-(1′-rac-glycerol) (LPG), the mixed vesicles led to the formation of stable SLBs. The dynamics of SLB formation monitored by QCM-D showed that while SLB formation by zwitterionic lipids followed a two-step process of vesicle adsorption followed by the breakdown of the adsorbed vesicles (which in turn is a result of multiple events) to create the SLB, the PG/LPG mixed vesicles ruptured immediately on contacting the quartz surface resulting in a one-step process of SLB formation. The QCM-D data also enabled the quantitative characterization of the SLB by allowing estimation of the lipid surface density as well as the thickness of the hydrophobic region of the SLB. These fully anionic SLBs are valuable model systems to conduct QCM-D studies of the interactions of extraneous substances such as antimicrobial peptides and nanoparticles with Gram-positive bacterial membranes.
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Fatima, Sana, Naila Malkani, Muhammad Muzammal, Asghar Ali Khan et Muhammad Usama. « Stable Vesicle Production from Bacterial Total Lipid Extracts ». Volume 4 Issue 1, Volume 4 Issue 1 (11 septembre 2021) : 1–10. http://dx.doi.org/10.34091/ajls.4.1.1.
Texte intégralRésumé :
The current study aims to produce stable liposomes from total lipid extracts from bacteria. Liposomes are the small vesicles that are made up of lipids. On their structural basis, they can be considered as simplified cell structure of cell membrane. Structure of liposomes depends on the pH of preparation buffer, method of preparation and the environmental condition in which they are prepared. Liposomes have importance in the field of medicines for diagnostic and therapeutic purposes. They mainly work as a vehicle for drug delivery. The objective of the current study was to make stable liposomes from two types of bacterial samples i.e., a Gram-positive and a Gram-negative strain. E. coli and Bacillus sp. were selected as representative of Gram-negative and Gram-positive bacteria, respectively. Lipid extraction was performed by various methods, out of which the modified Bligh and Dyer method gave most effective results. Liposomes were prepared by extrusion and their stability and efficiency was tested by fluorescence spectrophotometer using OxanolVI. Our results showed that liposomes formed by lipids extracted from E. coli were more stable than the liposomes formed by lipids extracted from Bacillus sp. Keywords: liposomes, Lipids, diagnostic, therapeutic, purposes, fluorescence, Bacillus sp.
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Raval, Jeel, Aleš Iglič et Wojciech Góźdź. « Investigation of Shape Transformations of Vesicles, Induced by Their Adhesion to Flat Substrates Characterized by Different Adhesion Strength ». International Journal of Molecular Sciences 22, no 24 (14 décembre 2021) : 13406. http://dx.doi.org/10.3390/ijms222413406.
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The adhesion of lipid vesicles to a rigid flat surface is investigated. We examine the influence of the membrane spontaneous curvature, adhesion strength, and the reduced volume on the stability and shape transformations of adhered vesicles. The minimal strength of the adhesion necessary to stabilize the shapes of adhered vesicles belonging to different shape classes is determined. It is shown that the budding of an adhered vesicle may be induced by the change of the adhesion strength. The importance of the free vesicle shape for its susceptibility to adhesion is discussed.
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Pir Cakmak, Fatma, Alex T. Grigas et Christine D. Keating. « Lipid Vesicle-Coated Complex Coacervates ». Langmuir 35, no 24 (16 mai 2019) : 7830–40. http://dx.doi.org/10.1021/acs.langmuir.9b00213.
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Hmam, Ons, et Antonella Badia. « Redox-Induced Lipid Vesicle Fusion Onto Electroactive Self-Assembled Monolayers ». ECS Meeting Abstracts MA2022-01, no 45 (7 juillet 2022) : 1941. http://dx.doi.org/10.1149/ma2022-01451941mtgabs.
Texte intégralRésumé :
Supported lipid bilayers (SLBs) are popular model systems to study cell membrane functionalities and various biomolecular interaction forces. A key advantage of SLBs on metallic surfaces, is the application of spectroscopic, electrochemical, and surface plasmon resonance techniques for biomolecular recognition studies. The most common method for forming SLBs is vesicle fusion, which involves the adsorption, deformation, and rupture of small unilamellar vesicles (SUVs) of lipids from aqueous suspension to the substrate surface.1 The formation of continuous single bilayers by vesicle fusion can be problematic due to the many experimental parameters influencing vesicle rupture and bilayer spreading (i.e., lipid and vesicle properties, physicochemical characteristics of the surface, temperature, and solvent environment)1. Vesicle fusion typically works only with smooth hydrophilic surfaces, such as glass, silica, and mica. Although approaches have been developed to form bilayers on technologically relevant surfaces such gold (e.g., surface functionalization with hydrophilic organic films,2 solvent-assisted lipid bilayer formation3 or the addition of a vesicle-destabilizing agent4), there remains a need for active strategies that are fast, versatile, and scalable. We present a redox-induced approach for the formation of single bilayers on gold functionalized with electroactive self-assembled monolayers (SAMs) of ferrocenylalkanethiolates. The electrochemical oxidation of the SAM-bound ferrocene (Fc) to ferrocenium (Fc+) involves coupled electron transfer and ion pairing reactions. Counteranions from solution pair with the ferroceniums to stabilize the oxidized cations and neutralize the excess positive charge at the SAM/aqueous interface. The surface-confined redox reaction triggers the formation of single bilayer membranes from SUVs of anionic or zwitterionic phospholipids onto gold surfaces modified with the electroactive SAM. The ion pairing association of the charged lipid head groups with the electrogenerated ferroceniums drives the assembly of the phospholipids on the SAM surface to produce solid-supported bilayers of high surface coverage (≳ 90%) from gel- or fluid-phase forming phospholipids within minutes at room temperature. The redox-mediated strategy reported in this work is a conceptual advance in the preparation of solid-supported lipid bilayers. It is fast, insensitive to the phase state of the phospholipid in the vesicle precursor, and not limited to hydrophilic surfaces. References Richter, R. P.; Bérat, R.; Brisson, A. R., Formation of Solid-Supported Lipid Bilayers: An Integrated View. Langmuir 2006, 22 (8), 3497-3505. Silin, V. I.; Wider, H.; Woodward, J. T.; Valincius, G.; Offenhausser, A.; Plant, A. L., The Role of Surface Energy on the Formation of Hybrid Bilayer Membranes. J. Am. Chem. Soc. 2002, 124, 14676-14683. Ferhan, A. R.; Yoon, B. K.; Park, S.; Sut, T. N.; Chin, H.; Park, J. H.; Jackman, J. A.; Cho, N.-J., Solvent-Assisted Preparation of Supported Lipid Bilayers. Nat. Protoc. 2019, 14 (7), 2091-2118. Cho, N.-J.; Cho, S.-J.; Cheong, K. H.; Glenn, J. S.; Frank, C. W., Employing an Amphipathic Viral Peptide to Create a Lipid Bilayer on Au and TiO2. J. Am. Chem. Soc. 2007, 129 (33), 10050-10051. Figure 1
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Smirnova, Y. G., et M. Müller. « How does curvature affect the free-energy barrier of stalk formation ? Small vesicles vs apposing, planar membranes ». European Biophysics Journal 50, no 2 (6 février 2021) : 253–64. http://dx.doi.org/10.1007/s00249-020-01494-1.
Texte intégralRésumé :
AbstractUsing molecular simulations of POPC lipids in conjunction with the calculation of the Minimum Free-Energy Path (MFEP), we study the effect of strong membrane curvature on the formation of the first fusion intermediate—the stalk between a vesicle and its periodic image. We find that the thermodynamic stability of this hourglass-shaped, hydrophobic connection between two vesicles is largely increased by the strong curvature of small vesicles, whereas the intrinsic barrier to form a stalk, i.e., associated with dimple formation and lipid tails protrusions, is similar to the case of two, apposing, planar membranes. A significant reduction of the barrier of stalk formation, however, stems from the lower dehydration free energy that is required to bring highly curved vesicle into a distance, at which stalk formation may occur, compared to the case of apposing, planar membranes.
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ZHAO, HONG, et ERIC S. G. SHAQFEH. « The dynamics of a vesicle in simple shear flow ». Journal of Fluid Mechanics 674 (23 mars 2011) : 578–604. http://dx.doi.org/10.1017/s0022112011000115.
Texte intégralRésumé :
We have performed direct numerical simulation (DNS) of a lipid vesicle under Stokes flow conditions in simple shear flow. The lipid membrane is modelled as a two-dimensional incompressible fluid with Helfrich surface energy in response to bending deformation. A high-fidelity spectral boundary integral method is used to solve the flow and membrane interaction system; the spectral resolution and convergence of the numerical scheme are demonstrated. The critical viscosity ratios for the transition from tank-treading (TT) to ‘trembling’ (TR, also called VB, i.e. vacillating-breathing, or swinging) and eventually ‘tumbling’ (TU) motions are calculated by linear stability analysis based on this spectral method, and are in good agreement with perturbation theories. The effective shear rheology of a dilute suspension of these vesicles is also calculated over a wide parameter regime. Finally, our DNS reveals a family of time-periodic and off-the-shear-plane motion patterns where the vesicle's configuration follows orbits that resemble but are fundamentally different from the classical Jeffery orbits of rigid particles due to the vesicle's deformability.
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Maleki, Mohsen, et Eliot Fried. « Multidomain and ground state configurations of two-phase vesicles ». Journal of The Royal Society Interface 10, no 83 (6 juin 2013) : 20130112. http://dx.doi.org/10.1098/rsif.2013.0112.
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A simple model is used to study the equilibrium of lipid domains on two-phase vesicles. Two classes of configurations are considered: multidomain and ground state configurations. For multidomain configurations, the vesicle has a finite number of identical lipid domains. For ground state configurations, the vesicle is fully phase separated into two coexisting domains. Whereas the volume enclosed by a vesicle with multidomains is fixed, the volume enclosed by a vesicle in a ground state is allowed to vary with the osmotic pressure. Guided by experimental observations, all domains are assumed to be spherical caps. In a multidomain configuration, the line tension is found to decrease with the number of domains present, with possible exceptions when the number of domains is very small. The importance of a critical osmotic pressure and a critical excess radius on ground state configurations is explored. Emphasis is placed on understanding the variations of these critical quantities with relevant parameters.
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Krebs, Anita, Allison Fannon, Thomas J. Racey, Paul Rochon, William T. Depew et Michael A. Singer. « Interaction of hepatic asialoglycoprotein receptor with dimyristoyl phosphatidylcholine vesicles ». Biochemistry and Cell Biology 65, no 1 (1 janvier 1987) : 56–61. http://dx.doi.org/10.1139/o87-008.
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The hepatocyte membrane asialoglycoprotein receptor (ASGP-R) was extracted from rabbit liver, purified, and then incubated with preformed vesicles of dimyristoyl phosphatidylcholine. The association of protein with lipid was dependent on vesicle size and the best results were achieved with small vesicles of about 20 nm diameter. The ligand binding capacity of ASGP-R–vesicle complexes was also measured and found to be approximately sevenfold greater than free receptor in aqueous buffer and twofold greater than receptor solubilized in Triton X-100. Most likely, the reconstitution procedure used in these experiments does not result in transmembrane insertion of the receptor. ASGP-R probably resides on the surface of the vesicle, held there primarily by weak hydrophobic forces.
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Heller, William T. « Small-Angle Neutron Scattering for Studying Lipid Bilayer Membranes ». Biomolecules 12, no 11 (29 octobre 2022) : 1591. http://dx.doi.org/10.3390/biom12111591.
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Small-angle neutron scattering (SANS) is a powerful tool for studying biological membranes and model lipid bilayer membranes. The length scales probed by SANS, being from 1 nm to over 100 nm, are well-matched to the relevant length scales of the bilayer, particularly when it is in the form of a vesicle. However, it is the ability of SANS to differentiate between isotopes of hydrogen as well as the availability of deuterium labeled lipids that truly enable SANS to reveal details of membranes that are not accessible with the use of other techniques, such as small-angle X-ray scattering. In this work, an overview of the use of SANS for studying unilamellar lipid bilayer vesicles is presented. The technique is briefly presented, and the power of selective deuteration and contrast variation methods is discussed. Approaches to modeling SANS data from unilamellar lipid bilayer vesicles are presented. Finally, recent examples are discussed. While the emphasis is on studies of unilamellar vesicles, examples of the use of SANS to study intact cells are also presented.
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Seneviratne, Rashmi, Lars J. C. Jeuken, Michael Rappolt et Paul A. Beales. « Hybrid Vesicle Stability under Sterilisation and Preservation Processes Used in the Manufacture of Medicinal Formulations ». Polymers 12, no 4 (15 avril 2020) : 914. http://dx.doi.org/10.3390/polym12040914.
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Sterilisation and preservation of vesicle formulations are important considerations for their viable manufacture for industry applications, particular those intended for medicinal use. Here, we undertake an initial investigation of the stability of hybrid lipid-block copolymer vesicles to common sterilisation and preservation processes, with particular interest in how the block copolymer component might tune vesicle stability. We investigate two sizes of polybutadiene-block-poly(ethylene oxide) polymers (PBd12-PEO11 and PBd22-PEO14) mixed with the phospholipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) considering the encapsulation stability of a fluorescent cargo and the colloidal stability of vesicle size distributions. We find that autoclaving and lyophilisation cause complete loss of encapsulation stability under the conditions studied here. Filtering through 200 nm pores appears to be viable for sterilisation for all vesicle compositions with comparatively low release of encapsulated cargo, even for vesicle size distributions which extend beyond the 200 nm filter pore size. Freeze-thaw of vesicles also shows promise for the preservation of hybrid vesicles with high block copolymer content. We discuss the process stability of hybrid vesicles in terms of the complex mechanical interplay between bending resistance, stretching elasticity and lysis strain of these membranes and propose strategies for future work to further enhance the process stability of these vesicle formulations.
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Perez-Castiñeira, J. R., et D. K. Apps. « Vacuolar H+-ATPase of adrenal secretory granules. Rapid partial purification and reconstitution into proteoliposomes ». Biochemical Journal 271, no 1 (1 octobre 1990) : 127–31. http://dx.doi.org/10.1042/bj2710127.
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A procedure has been developed for the rapid purification and reconstitution into phospholipid vesicles of the proton-translocating ATPase of bovine adrenal chromaffin-granule membranes. It involves fractionation of the membranes with Triton X-114, resolubilization of the ATPase with n-octyl glucoside, addition of purified lipids and removal of detergent by gel filtration. The entire process can be completed within 2 h. H+ translocation was detected by the ATP-dependent quenching of the fluorescence of a permeant weak base. The effect of varying the lipid composition of the vesicles on ATP hydrolysis and H+ translocation by the reconstituted enzyme was examined. ATPase activity was maximally increased about 4-fold by added lipid, but was relatively insensitive to its composition, whereas vesicle acidification was absolutely dependent on the addition of phospholipids and cholesterol.
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Montecucco, C., G. Schiavo, Z. Gao, E. Bauerlein, P. Boquet et B. R. DasGupta. « Interaction of botulinum and tetanus toxins with the lipid bilayer surface ». Biochemical Journal 251, no 2 (15 avril 1988) : 379–83. http://dx.doi.org/10.1042/bj2510379.
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The interaction of botulinum neurotoxins serotypes A, B and E (from Clostridium botulinum) and of tetanus neurotoxin (from Clostridium tetani) with the surface of liposomes made of different lipid compositions was studied by photolabelling with a radioiodinated photoactive phosphatidylethanolamine analogue [125I-dipalmitoyl (3,4-azidosalicylamido)phosphatidylethanolamine]. When the vesicles were made of negatively charged lipids (asolectin), each of these neurotoxic proteins was radioiodinated, thus providing evidence for their attachment to the membrane surface. The presence of gangliosides on liposome membranes enhanced fixation of the neurotoxic proteins to the lipid vesicle surface. Both the heavy and light chains of the clostridial neurotoxins were involved in the attachment to the lipid bilayer surface. Each of the toxins tested here attached poorly to liposomes made of zwitterionic lipids (egg phosphatidylcholine), even when polysialogangliosides were present. The data suggest that the binding of botulinum and tetanus neurotoxins to their target neuronal cells involves negatively charged lipids and polysialogangliosides on the cell membrane.
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Xu, Baomei, Jianhui Li, Shuai Zhang, Johar Zeb, Shunli Chen, Qunhui Yuan et Wei Gan. « The Transport of Charged Molecules across Three Lipid Membranes Investigated with Second Harmonic Generation ». Molecules 28, no 11 (25 mai 2023) : 4330. http://dx.doi.org/10.3390/molecules28114330.
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Subtle variations in the structure and composition of lipid membranes can have a profound impact on their transport of functional molecules and relevant cell functions. Here, we present a comparison of the permeability of bilayers composed of three lipids: cardiolipin, DOPG (1,2-dioleoyl-sn-glycero-3-phospho-(1′-rac-glycerol), and POPG (1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1′-rac-glycerol)). The adsorption and cross-membrane transport of a charged molecule, D289 (4-(4-diethylaminostyry)-1-methyl-pyridinium iodide), on vesicles composed of the three lipids were monitored by second harmonic generation (SHG) scattering from the vesicle surface. It is revealed that structural mismatching between the saturated and unsaturated alkane chains in POPG leads to relatively loose packing structure in the lipid bilayers, thus providing better permeability compared to unsaturated lipid bilayers (DOPG). This mismatching also weakens the efficiency of cholesterol in rigidifying the lipid bilayers. It is also revealed that the bilayer structure is somewhat disturbed by the surface curvature in small unilamellar vesicles (SUVs) composed of POPG and the conical structured cardiolipin. Such subtle information on the relationship between the lipid structure and the molecular transport capability of the bilayers may provide clues for drug development and other medical and biological studies.
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Barakat, Joseph M., et Eric S. G. Shaqfeh. « Stokes flow of vesicles in a circular tube ». Journal of Fluid Mechanics 851 (30 juillet 2018) : 606–35. http://dx.doi.org/10.1017/jfm.2018.533.
Texte intégralRésumé :
The inertialess motion of lipid-bilayer vesicles flowing through a circular tube is investigated via direct numerical simulation and lubrication theory. A fully three-dimensional boundary integral equation method, previously used to study unbounded and wall-bounded Stokes flows around freely suspended vesicles, is extended to study the hindered mobility of vesicles through conduits of arbitrary cross-section. This study focuses on the motion of a periodic train of vesicles positioned concentrically inside a circular tube, with particular attention given to the effects of tube confinement, vesicle deformation and membrane bending elasticity. When the tube diameter is comparable to the transverse dimension of the vesicle, axisymmetric lubrication theory provides an approximate solution to the full Stokes-flow problem. By combining the present numerical results with a previously reported asymptotic theory (Barakat & Shaqfeh, J. Fluid Mech., vol. 835, 2018, pp. 721–761), useful correlations are developed for the vesicle velocity $U$ and extra pressure drop $\unicode[STIX]{x0394}p^{+}$. When bending elasticity is relatively weak, these correlations are solely functions of the geometry of the system (independent of the imposed flow rate). The prediction of Barakat & Shaqfeh (2018) supplies the correct limiting behaviour of $U$ and $\unicode[STIX]{x0394}p^{+}$ near maximal confinement, whereas the present study extends this result to all regimes of confinement. Vesicle–vesicle interactions, shape transitions induced by symmetry breaking, and unsteadiness introduce quantitative changes to $U$ and $\unicode[STIX]{x0394}p^{+}$. By contrast, membrane bending elasticity can qualitatively affect the hydrodynamics at sufficiently low flow rates. The dependence of $U$ and $\unicode[STIX]{x0394}p^{+}$ on the membrane bending stiffness (relative to a characteristic viscous stress scale) is found to be rather complex. In particular, the competition between viscous forces and bending forces can hinder or enhance the vesicle’s mobility, depending on the geometry and flow conditions.
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Neupane, Shova, George Cordoyiannis, Frank Uwe Renner et Patricia Losada-Pérez. « Real-Time Monitoring of Interactions between Solid-Supported Lipid Vesicle Layers and Short- and Medium-Chain Length Alcohols : Ethanol and 1-Pentanol ». Biomimetics 4, no 1 (22 janvier 2019) : 8. http://dx.doi.org/10.3390/biomimetics4010008.
Texte intégralRésumé :
Lipid bilayers represent the interface between the cell and its environment, serving as model systems for the study of various biological processes. For instance, the addition of small molecules such as alcohols is a well-known process that modulates lipid bilayer properties, being considered as a reference for general anesthetic molecules. A plethora of experimental and simulation studies have focused on alcohol’s effect on lipid bilayers. Nevertheless, most studies have focused on lipid membranes formed in the presence of alcohols, while the effect of n-alcohols on preformed lipid membranes has received much less research interest. Here, we monitor the real-time interaction of short-chain alcohols with solid-supported vesicles of dipalmitoylphosphatidylcholine (DPPC) using quartz crystal microbalance with dissipation monitoring (QCM-D) as a label-free method. Results indicate that the addition of ethanol at different concentrations induces changes in the bilayer organization but preserves the stability of the supported vesicle layer. In turn, the addition of 1-pentanol induces not only changes in the bilayer organization, but also promotes vesicle rupture and inhomogeneous lipid layers at very high concentrations.
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Beck, Rainer, Simone Prinz, Petra Diestelkötter-Bachert, Simone Röhling, Frank Adolf, Kathrin Hoehner, Sonja Welsch et al. « Coatomer and dimeric ADP ribosylation factor 1 promote distinct steps in membrane scission ». Journal of Cell Biology 194, no 5 (5 septembre 2011) : 765–77. http://dx.doi.org/10.1083/jcb.201011027.
Texte intégralRésumé :
Formation of coated vesicles requires two striking manipulations of the lipid bilayer. First, membrane curvature is induced to drive bud formation. Second, a scission reaction at the bud neck releases the vesicle. Using a reconstituted system for COPI vesicle formation from purified components, we find that a dimerization-deficient Arf1 mutant, which does not display the ability to modulate membrane curvature in vitro or to drive formation of coated vesicles, is able to recruit coatomer to allow formation of COPI-coated buds but does not support scission. Chemical cross-linking of this Arf1 mutant restores vesicle release. These experiments show that initial curvature of the bud is defined primarily by coatomer, whereas the membrane curvature modulating activity of dimeric Arf1 is required for membrane scission.
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Caliari, Adriano, Martin M. Hanczyc, Masayuki Imai, Jian Xu et Tetsuya Yomo. « Quantification of Giant Unilamellar Vesicle Fusion Products by High-Throughput Image Analysis ». International Journal of Molecular Sciences 24, no 9 (4 mai 2023) : 8241. http://dx.doi.org/10.3390/ijms24098241.
Texte intégralRésumé :
Artificial cells are based on dynamic compartmentalized systems. Thus, remodeling of membrane-bound systems, such as giant unilamellar vesicles, is finding applications beyond biological studies, to engineer cell-mimicking structures. Giant unilamellar vesicle fusion is rapidly becoming an essential experimental step as artificial cells gain prominence in synthetic biology. Several techniques have been developed to accomplish this step, with varying efficiency and selectivity. To date, characterization of vesicle fusion has relied on small samples of giant vesicles, examined either manually or by fluorometric assays on suspensions of small and large unilamellar vesicles. Automation of the detection and characterization of fusion products is now necessary for the screening and optimization of these fusion protocols. To this end, we implemented a fusion assay based on fluorophore colocalization on the membranes and in the lumen of vesicles. Fluorescence colocalization was evaluated within single compartments by image segmentation with minimal user input, allowing the application of the technique to high-throughput screenings. After detection, statistical information on vesicle fluorescence and morphological properties can be summarized and visualized, assessing lipid and content transfer for each object by the correlation coefficient of different fluorescence channels. Using this tool, we report and characterize the unexpected fusogenic activity of sodium chloride on phosphatidylcholine giant vesicles. Lipid transfer in most of the vesicles could be detected after 20 h of incubation, while content exchange only occurred with additional stimuli in around 8% of vesicles.
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Boban, Zvonimir, Ivan Mardešić, Sanja Perinović Jozić, Josipa Šumanovac, Witold Karol Subczynski et Marija Raguz. « Electroformation of Giant Unilamellar Vesicles from Damp Lipid Films Formed by Vesicle Fusion ». Membranes 13, no 3 (18 mars 2023) : 352. http://dx.doi.org/10.3390/membranes13030352.
Texte intégralRésumé :
Giant unilamellar vesicles (GUVs) are artificial membrane models which are of special interest to researchers because of their similarity in size to eukaryotic cells. The most commonly used method for GUVs production is electroformation. However, the traditional electroformation protocol involves a step in which the organic solvent is completely evaporated, leaving behind a dry lipid film. This leads to artifactual demixing of cholesterol (Chol) in the form of anhydrous crystals. These crystals do not participate in the formation of the lipid bilayer, resulting in a decrease of Chol concentration in the bilayer compared to the initial lipid solution. We propose a novel electroformation protocol which addresses this issue by combining the rapid solvent exchange, plasma cleaning and spin-coating techniques to produce GUVs from damp lipid films in a fast and reproducible manner. We have tested the protocol efficiency using 1/1 phosphatidylcholine/Chol and 1/1/1 phosphatidylcholine/sphingomyelin/Chol lipid mixtures and managed to produce a GUV population of an average diameter around 40 µm, with many GUVs being larger than 100 µm. Additionally, compared to protocols that include the dry film step, the sizes and quality of vesicles determined from fluorescence microscopy images were similar or better, confirming the benefits of our protocol in that regard as well.