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(a) Temperature–pressure phase diagrams of DPPC bilayer: (blue) in D2O, (black) in H2O. (b) Temperature–pressure phase diagrams of DPPC bilayer: (red) in 0.4 M ethanol solution, (black) in H2O. Phase transitions are the same as those in Figure 2b.
Source publication
Bilayers formed by phospholipids are frequently used as model biological membranes in various life science studies. A characteristic feature of phospholipid bilayers is to undergo a structural change called a phase transition in response to environmental changes of their surroundings. In this review, we focus our attention on phase transitions of s...
Citations
... As described in previous studies [27][28][29], we extracted from these data the pressure-distance curves, i.e., the dehydrating osmotic pressure Π as a function of the repeat distance d. As seen in Fig. 2A, by increasing the humidity, DPPC molecules transit from the gel to the fluid phase via a ripple phase through a narrow window of osmotic pressures as previously reported [30,31]. In contrast, DP-DGTS bilayers show a phase coexistence that can be observed over a wide Π-range and without the appearance of a third phase that could be attributed to a distinct ripple phase (Fig. 2B) before forming a single fluid phase at high humidity (i.e., at low Π). ...
Background
Many organisms rely on mineral nutrients taken directly from the soil or aquatic environment, and therefore, developed mechanisms to cope with the limitation of a given essential nutrient. For example, photosynthetic cells have well-defined responses to phosphate limitation, including the replacement of cellular membrane phospholipids with non-phosphorous lipids. Under phosphate starvation, phospholipids in extraplastidial membranes are replaced by betaine lipids in microalgae. In higher plants, the synthesis of betaine lipid is lost, driving plants to other strategies to cope with phosphate starvation where they replace their phospholipids by glycolipids.
Results
The aim of this work was to evaluate to what extent betaine lipids and PC lipids share physicochemical properties and could substitute for each other. By neutron diffraction experiments and dynamic molecular simulation of two synthetic lipids, the dipalmitoylphosphatidylcholine (DPPC) and the dipalmitoyl-diacylglyceryl-N,N,N-trimethylhomoserine (DP-DGTS), we found that DP-DGTS bilayers are thicker than DPPC bilayers and therefore are more rigid. Furthermore, DP-DGTS bilayers are more repulsive, especially at long range, maybe due to unexpected unscreened electrostatic contribution. Finally, DP-DGTS bilayers could coexist in the gel and fluid phases.
Conclusion
The different properties and hydration responses of PC and DGTS provide an explanation for the diversity of betaine lipids observed in marine organisms and for their disappearance in seed plants.
... At ambient pressure and above 0°C in the fully hydrated state (i.e., at water concentrations above 30 wt %), the following DPPC phases are typically observed: liquid crystalline lamellar Lα, lamellar gel Lβ′, gel with wave-like ripples Pβ′, and lamellar crystalline Lc phases. 23,24 Additional information on the phase relationships in the DPPC/water system can be found in the Supporting Information. Furthermore, relationships have been established between the hydrostatic pressure and DPPC structure. ...
Water-to-ice transformation results in a 10% increase in volume, which can have a significant impact on biopharmaceuticals during freeze–thaw cycles due to the mechanical stresses imparted by the growing ice crystals. Whether these stresses would contribute to the destabilization of biopharmaceuticals depends on both the magnitude of the stress and sensitivity of a particular system to pressure and sheer stresses. To address the gap of the “magnitude” question, a phospholipid, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), is evaluated as a probe to detect and quantify the freeze-induced pressure. DPPC can form several phases under elevated pressure, and therefore, the detection of a high-pressure DPPC phase during freezing would be indicative of a freeze-induced pressure increase. In this study, the phase behavior of DPPC/water suspensions, which also contain the ice nucleation agent silver iodide, is monitored by synchrotron small/wide-angle X-ray scattering during the freeze–thaw transition. Cooling the suspensions leads to heterogeneous ice nucleation at approximately −7 °C, followed by a phase transition of DPPC between −11 and −40 °C. In this temperature range, the initial gel phase of DPPC, Lβ′, gradually converts to a second phase, tentatively identified as a high-pressure Gel III phase. The Lβ′-to-Gel III phase transition continues during an isothermal hold at −40 °C; a second (homogeneous) ice nucleation event of water confined in the interlamellar space is detected by differential scanning calorimetry (DSC) at the same temperature. The extent of the phase transition depends on the DPPC concentration, with a lower DPPC concentration (and therefore a higher ice fraction), resulting in a higher degree of Lβ′-to-Gel III conversion. By comparing the data from this study with the literature data on the pressure/temperature Lβ′/Gel III phase boundary and the lamellar lattice constant of the Lβ′ phase, the freeze-induced pressure is estimated to be approximately 0.2–2.6 kbar. The study introduces DPPC as a probe to detect a pressure increase during freezing, therefore addressing the gap between a theoretical possibility of protein destabilization by freeze-induced pressure and the current lack of methods to detect freeze-induced pressure. In addition, the observation of a freeze-induced phase transition in a phospholipid can improve the mechanistic understanding of factors that could disrupt the structure of lipid-based biopharmaceuticals, such as liposomes and mRNA vaccines, during freezing and thawing.
... There-fore, the regulation of sphingolipid synthesis or actin organization may be important for high-pressure adaptation. Indeed, high pressures stiffen membrane lipid bilayers (Winter, 2002;Matsuki et al., 2013), which may adversely affect membrane protein functions, membrane fusion, or membrane trafficking. Furthermore, hypoosmotic stress causes the depolymerization of the actin cytoskeleton (Gualtieri et al., 2004). ...
The fungal cell wall is the initial barrier for the fungi against diverse external stresses, such as osmolarity changes, harmful drugs, and mechanical injuries. This study explores the roles of osmoregulation and the cell wall integrity (CWI) pathway in response to high hydrostatic pressure in the yeast Saccharomyces cerevisiae. We demonstrate the roles of the transmembrane mechanosensor Wsc1 and aquaglyceroporin Fps1 in a general mechanism to maintain cell growth under high-pressure regimes. The promotion of water influx into cells at 25 MPa, as evident by an increase in cell volume and a loss of the plasma membrane eisosome structure, activates the CWI pathway through the function of Wsc1. Phosphorylation of Slt2, the downstream mitogen-activated protein kinase, was increased at 25 MPa. Glycerol efflux increases via Fps1 phosphorylation, which is initiated by downstream components of the CWI pathway, and contributes to the reduction in intracellular osmolarity under high pressure. The elucidation of the mechanisms underlying adaptation to high pressure through the well-established CWI pathway could potentially translate to mammalian cells and provide novel insights into cellular mechanosensation.
... This material maintains a nanosheet structure even under dilute conditions [53]. Moreover, because the T m of DPPC is 41°C, which is above room temperature, DPPC membranes form a less fluid gel phase under ambient conditions [54] that tends to provide kinetically stable assemblies. Finally, Chol-TEG-C 5 has a low CMC ( < 0.5 mM) as a result of the introduction of hydrophobic end-cap groups, such that dissociation from the edges of the DPPC membranes is suppressed [55]. ...
Two specific concepts have emerged in the field of materials science over the last several decades: nanosheets and supramolecular polymers. More recently, supramolecular nanosheets, in which these two concepts are integrated, have attracted particular attention, and they exhibit many fascinating characteristics. This review focuses on the design and applications of supramolecular nanosheets consisting of tubulin proteins and phospholipid membranes.
... As described in previous studies [22][23][24], we extracted from these data the pressure-distance curves, i.e., the dehydrating osmotic pressure as a function of the repeat distance d. As seen in Figure 2A , by increasing the humidity, DPPC molecules transit from the gel to the fluid phase through a narrow window of osmotic pressures as previously reported [25,26]. In contrast, DP-DGTS bilayers show a phase coexistence that can be observed over a wide -range ( Figure 2B) before forming a single fluid phase at high humidity (i.e., at low ). ...
Phosphate is vital for plant and algae growth, yield, and survival, but in most environments, it is poorly available. To cope with phosphate starvation, photosynthetic organisms used their phospholipids as a phosphate reserve. In microalgae, betaine lipids replace phospholipids whereas, in higher plants, betaine lipid synthesis is lost, driving plants to other strategies. The aim of this work was to evaluate to what extent betaine lipids and PC lipids share physicochemical properties and could thus substitute each other. Using neutron diffraction and molecular dynamics simulations of two synthetic lipids, dipalmitoylphosphatidylcholine (DPPC) and dipalmitoyl-diacylglyceryl-N,N,N-trimethylhomoserine (DP-DGTS), we show that DP-DGTS bilayers are thicker, more rigid, and mutually more repulsive than DPPC bilayers. The different properties and hydration response of PC and DGTS provide an explanation for the diversity of betaine lipids observed in marine organisms and for their disappearance in seed plants.
... 57 Saturated DPPC displays a solidlike gel phase at room temperature, whereas unsaturated DOPC remains fluidlike. 58 By hybridizing PDMS-g-PEO with DPPC/POPC, it was demonstrated that the lipid phase modulated the critical lipid concentration at which phase separation starts to occur. When fluid POPC is used with a majority of polymer (>60% mol), GHUVs were homogeneous while with DPPC, heterogeneous vesicles were obtained for any composition of lipid between 90% and 20% mol. ...
... 69 As mentioned above, the transition temperature of lipids is an important factor to be considered in the preparation of GHUVs with the example of DPPC and DOPC having a different phase at room temperature. 58 Several examples demonstrated that the cooling rate after GHUV formation could be used to control the shape of DPPC domains when mixed with PBD 46 -b-PEO 30 or PDMS-g-PEO to form star-shaped or spherical domains [ Fig. 4(b)]. 67 Block copolymers have been typically incorporated to modify the permeability of GHUVs. ...
Phase separation in biological membranes is crucial for proper cellular functions, such as signaling and trafficking, as it mediates the interactions of condensates on membrane-bound organelles and transmembrane transport to targeted destination compartments. The separation of a lipid bilayer into phases and the formation of lipid rafts involve the restructuring of molecular localization, their immobilization, and local accumulation. By understanding the processes underlying the formation of lipid rafts in a cellular membrane, it is possible to reconstitute this phenomenon in synthetic biomimetic membranes, such as hybrids of lipids and polymers or membranes composed solely of polymers, which offer an increased physicochemical stability and unlimited possibilities of chemical modification and functionalization. In this article, we relate the main lipid bilayer phase transition phenomenon with respect to hybrid biomimetic membranes, composed of lipids mixed with polymers, and fully synthetic membranes. Following, we review the occurrence of phase separation in biomimetic hybrid membranes based on lipids and/or direct lipid analogs, amphiphilic block copolymers. We further exemplify the phase separation and the resulting properties and applications in planar membranes, free-standing and solid-supported. We briefly list methods leading to the formation of such biomimetic membranes and reflect on their improved overall stability and influence on the separation into different phases within the membranes. Due to the importance of phase separation and compartmentalization in cellular membranes, we are convinced that this compiled overview of this phenomenon will be helpful for any researcher in the biomimicry area.
... Lipid molecules can self-assemble into a huge variety of different liquid crystalline phases. 1 These phases can exist as either lamellar phases, where lipids form a bilayer structure, 2 or as more complex non-lamellar structures, such as inverse hexagonal (H II ) 3 and inverse bi-continuous cubic phases (Q II ). 4 Lipid phases are readily and controllably interconvertible through altering parameters which can include chemical composition, 5 temperature, 6 pressure, and pH. 7 This enables cells to modulate protein activity, 8 impact signalling pathways 9 and to facilitate membrane fusion events. ...
Lipid membranes are vital in a wide range of biological and biotechnical systems; they undepin functions from modulation of protein activity to drug uptake and delivery. Understanding the structure, interactions, self-assembly and phase behaviour of lipids is critical to developing a molecular undertanding of biological membrane mediated processes, establishing engineering approaches to biotechnical membrane application development. Small Angle X-ray Scattering (SAXS) is the de facto method used to analyse the structure of self-assembled lipid systems. The resultant diffraction patterns are however extremely difficult to assign automatically with researchers spending considerable time often analysing patterns ex situ from a beamline facility, reducing experimental capacity and optimisation. Furthermore, research projects will often focus on particular lipid compositions and thus would benefit significantly from a method which can be rapidly optimised for a range of samples of interest. We present a generalisable machine learning pipeline that is able to classify lipid phases based on their raw, experimental SAXS spectra, with >99% accuracy and an inference time of <60 ms, enabling high throughput on-site analysis. We achieved this through application of a synthetic data generation system, capable of building synthetic SAXS patterns from the underlying physics which dictate phase behaviour, and we also propose an extension of our system to synthetically generate co-existence phase spectra with known composition ratios. Pre-training our machine learning model on this synthetic data, and fine-tuning on experimental samples empowers the model in achieving state-of-the-art, rapid lipid phase classification, allowing researchers to be able to adapt their experiments on site if needed and hence massively accelerate high throughput lipid research.
... Phosphatidylcholine (PC), one of the essential phospholipids of all cell-membrane, due to its structural composition gives the cellmembrane structural integrity being able to cause fluctuation in cell-membrane characteristics (density, permeability, flexibility, dynamics) and as well, forms lipidic bi-layers with relevance in health sciences and in several bio-processes [21][22][23][24][25]. ...
Absorption and emission monitoring of bioactive flavonols, Hydroxyflavones (HFs), (3-HF, 3,6-diHF and 3,7-diHF), to explore their microenvironments as a function of pH and temperature in lipidic bi-layers of lecithin (EYPC), have been studied. The influence of lipidic bi-layers on the −OH groups deprotonation of HFs with several distribution in the vicinity of the polar phosphate groups of EYPC when pH changed as well as the position of −OH groups in the HFs structure on the excited-state intramolecular proton transfer (ESIPT), have been studied by fluorescence spectroscopy. It was found that at physiological pH, EYPC leads to the increase of the quantum yield of Tautomer fluorescence for HFs with multiple −OH groups. There is a temperature-dependent difference in the ESIPT process which takes place in HFs/EYPC systems. The findings are relevant for in vivo and in vitro studies of the oxidative stress process which involves cell membranes, where HFs are used as sensitive fluorescence probes.
... L'effet des HP sur les membranes lipidiques est très similaire à l'effet des basses températures : augmentation de la compacité, de la rigidité, diminution de la mobilité des lipides, réduction de la perméabilité et, in fine, la transition de phase fluide Þ gel est favorisée (Matsuki et al. 2013;. Dans la mesure où des valeurs de pression modérées causent déjà des effets drastiques et des pertes de fonction biologique, les membranes sont considérées comme le paramètre le plus sensible aux HP. ...
Au carrefour des disciplines, l’exobiologie a pour objet la vie dans l’Univers. Parmi ses thématiques, la question des limites du vivant se pose avec celle de l’habitabilité des environnements extraterrestres. Proches de ces limites, les extrêmophiles terrestres peuplant les environnements extrêmes telles les cheminées hydrothermales ou la Mer Morte, indiquent que la présence d’eau liquide reste une condition nécessaire à la vie. Sa recherche dans le Système Solaire et au-delà demeure donc une priorité en exobiologie, justifiant l’intérêt porté aux océans subglaciaires des lunes glacées ainsi qu’aux saumures Martiennes.Les océans subglaciaires renferment, de loin, la majeure partie de l’eau liquide dans le Système Solaire et certaines, comme Encelade, pourraient présenter des cheminées hydrothermales dans leurs abysses. Sur Terre, les cheminées hydrothermales sont des biotopes indépendants de la surface, complexes et productifs malgré les conditions de pression et de température extrêmes qui les caractérisent. Ils constituent donc des modèles de premier ordre pour une hypothétique vie sur les lunes glacées. Des différences potentielles de conditions physico-chimiques viennent cependant limiter cette analogie. En particulier, la pression dans les abysses d’Europe pourrait excéder celle rencontrée au niveau des cheminées hydrothermales terrestres. La vie est-elle compatible avec de telles conditions ?Dans un premier projet, nous avons étudié les effets des hautes pressions (HP) à une échelle moléculaire en utilisant comme principal modèle l’ADN polymérase (ADNpol) B de l’archée hyperthermophile abyssale Pyrococcus abyssi. En utilisant des rapporteurs fluorescents de diverses natures et un fluorimètre couplé à une enceinte HP, nous avons étudié les effets des pressions allant de 0,1 à 100MPa sur l’activité de cette enzyme et comparé sa sensibilité aux HP à celles d’autres ADNpols thermostables. Nous démontrons que les HP inhibent directement l’activité des ADNpols et que cette inhibition peut être largement compensée par une augmentation de la température. Les implications exobiologiques et concernant l’adaptation aux HP chez les organismes abyssaux sont par ailleurs discutées.Plus proche de la Terre, un autre type d’environnement pourrait abriter de l’eau liquide dans le Système Solaire : les saumures Martiennes. Présentes de manière transitoire à la surface et de façon plus pérenne dans les environnements souterrains, ces saumures se caractérisent par une salinité importante et l’abondance de composés chaotropes comme les ions Mg2+, Ca2+ et ClO42-. Sur Terre, les environnements hypersalins comme la Mer Morte ou les bassins de saumures abyssaux sont peuplés par des microorganismes spécialisés appelés halophiles. Les plus extrêmes d’entre eux sont des archées de la classe Halobacteria qui présentent des traits caractéristiques, comme l’accumulation intracellulaire de KCl et l’acidification des protéines, et constituent des modèles de choix en exobiologie.Dans un deuxième projet, nous avons comparé les propriétés du protéome entier, et non de protéines modèles isolées, entre cinq archées hyperhalophiles issues d’environnements différents. Cette comparaison a été réalisée en utilisant diverses méthodes, analyse statistique des séquences, protéomique, dosage des ions intracellulaires ou encore diffusion des neutrons, et a notamment permis le développement d’une méthode biophysique de caractérisation de la dépendance au sel du protéome. Nous avons révélé des différences significatives de propriétés intrinsèques du protéome et de l’environnement intracellulaire entre les cinq souches qui soulignent le lien entre l’adaptation à l’environnement et l’adaptation moléculaire chez les halophiles. La réponse du protéome à des sels caractéristiques des saumures Martiennes présente également des implications exobiologiques concernant la recherche de traces de vie sur Mars.
... The phase transition of lipid bilayers in biological systems is highly sensitive to high pressure. High pressure and low temperature reorder acyl chains of phospholipids, making the membrane stiffer [29,30]. In dipalmitoylphosphatidylcholine lipid bilayers, the temperature for the transition (T m ) from the ripple gel (P β ') phase to the liquid crystalline (L α ) phase increases by 24 • C with an increase in pressure of 100 MPa [31]. ...
High hydrostatic pressure is common mechanical stress in nature and is also experienced by the human body. Organisms in the Challenger Deep of the Mariana Trench are habitually exposed to pressures up to 110 MPa. Human joints are intermittently exposed to hydrostatic pressures of 3–10 MPa. Pressures less than 50 MPa do not deform or kill the cells. However, high pressure can have various effects on the cell’s biological processes. Although Saccharomyces cerevisiae is not a deep-sea piezophile, it can be used to elucidate the molecular mechanism underlying the cell’s responses to high pressures by applying basic knowledge of the effects of pressure on industrial processes involving microorganisms. We have explored the genes associated with the growth of S. cerevisiae under high pressure by employing functional genomic strategies and transcriptomics analysis and indicated a strong association between high-pressure signaling and the cell’s response to nutrient availability. This review summarizes the occurrence and significance of high-pressure effects on complex metabolic and genetic networks in eukaryotic cells and how the cell responds to increasing pressure by particularly focusing on the physiology of S. cerevisiae at the molecular level. Mechanosensation in humans has also been discussed.
