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Paolo Mariani - One of the best experts on this subject based on the ideXlab platform.
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Sugar-induced stabilization of the monoolein Pn3m bicontinuous cubic phase during dehydration.
Physical review. E Statistical nonlinear and soft matter physics, 2001Co-Authors: Letizia Saturni, Franco Rustichelli, Lorenzo Cordone, G M Di Gregorio, Paolo MarianiAbstract:To explore the molecular mechanism of the protective function of sugars on cubic lipidic systems, the mesomorphic properties of the monoolein-water system, dehydrated in the presence of a series of sugars, have been studied by osmotic stress experiments. Two bicontinuous inverse cubic structures (Pn3m and Ia3d) and a lamellar L(alpha) phase form under dehydration in pure water. In sugar solutions, the Pn3m phase shows an extraordinary stability: as a function of sugar concentration, the lattice parameter decreases to very low values, but no phase transitions occur. Instead, the Pn3m to Ia3d phase transition is obtained by equilibrating the lipid phase with aqueous polymer solutions of increasing osmotic pressure. As a result, the pressure at which the phase transition occurs strongly depends on sugar concentration. The free-energy curves obtained from the osmotic-pressure unit-cell data show that the sugar exerts an additional stabilization on both the cubic phases. The analysis of the structural parameters indicates that sugars alter the interface geometry. We suggest that a consequent release of stretching contributions in the chain packing or a reduction of the inhomogeneity in molecular splay mainly stabilize the Pn3m phase and prevent the transition to the Ia3d phase on dehydration.
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Pressure Induced Cubic-to-Cubic Phase Transition in Monoolein Hydrated System
The Journal of Physical Chemistry B, 2001Co-Authors: Michela Pisani, Sigrid Bernstorff, And Claudio Ferrero, Paolo MarianiAbstract:Synchrotron X-ray diffraction has been used to investigate structure, stability, and transformation of the Pn3m bicontinuous cubic phase in the monoolein−water system under hydrostatic pressure. As a first result, it appears that the full-hydration properties of monoolein are strongly related to the pressure. Moreover, the experimental results show the occurrence of a Pn3m to Ia3d cubic phase transition when the mechanical pressure increases to 1−1.2 kbar, depending on the water concentration. The underlying mechanism for the phase transition has been then explored in searching for relationships between the structural parameters derived from the two cubic phases. The emerging picture is a change in the basic geometrical shape of the monoolein molecule during compression. Moreover, the analysis of the position of the pivotal surface indicates that the interface is bending and stretching simultaneously as a function of pressure. Because the lipid concentration is rather low and the external pressure increas...
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Stabilization of the monoolein Pn3m cubic structure on trehalose glasses
European Biophysics Journal, 1999Co-Authors: Paolo Mariani, Franco Rustichelli, Letizia Saturni, Lorenzo CordoneAbstract:Trehalose is known to protect some organisms from various stresses due to drought and high temperature. To explore the molecular mechanism of the protective function, the mesomorphic properties of the monoolein-water system, dried in the presence of trehalose, were studied by X-ray diffraction. While, in pure water, two bicontinuous inverse cubic structures (the Pn3m and Ia3d phases) and a lamellar Lα phase exist as a function of concentration, only the Pn3m cubic phase has been detected in concentrated trehalose solutions or in trehalose glasses, even under extremely dry conditions. Depending on the sugar concentration, or after glass dehydration, the Pn3m cubic unit cell decreases to very low values, much below the smaller one observed in pure water. However, as no phase transitions occur, a simple osmotic mechanism can be excluded. An additional stabilization of the lipid phase, arising from interfacial free energy changes due to trehalose-water-lipid direct interactions, and large enough to affect the energetic balance between the Pn3m and the Ia3d cubic phases, evidently occurs. Moreover, no differences in the Pn3m cubic structure were observed when the sugar platelets convert to the glassy state; no apparent structural modifications that can be related to mechanical pressure exerted on the lipid phase have been detected.
Raffaele Mezzenga - One of the best experts on this subject based on the ideXlab platform.
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Rheology of Ultraswollen Bicontinuous Lipidic Cubic Phases.
Langmuir : the ACS journal of surfaces and colloids, 2018Co-Authors: Chiara Speziale, Reza Ghanbari, Raffaele MezzengaAbstract:Rheological studies of liquid crystalline systems based on monopalmitolein and 5 or 8% of 1,2 distearoylphosphatidylglycerol are reported. Such cubic phases have been shown to possess unusually large water channels because of their ability of accommodating up to 80 wt % of water, a feature that renders these systems suitable for crystallizing membrane proteins with large extracellular domains. Their mechanical properties are supposed to be substantially different from those of traditional cubic phases. Rheological measurements were carried out on cubic phases of both Pn3m and Ia3d symmetries. It was verified that these ultraswollen cubic phases are less rigid than the normal cubic phases, with the Pn3m being softer that the Ia3d ones. Furthermore, for the Pn3m case, the longest relaxation time is shown to decrease logarithmically with increasing surface area per unit volume, proving the critical role of the density of interfaces in establishing the macroscopic viscoelastic properties of the bicontinuous c...
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Design of ultra-swollen lipidic mesophases for the crystallization of membrane proteins with large extracellular domains.
Nature communications, 2018Co-Authors: Alexandru Zabara, Josephine Tse Yin Chong, Isabelle Martiel, Laura Stark, Brett A. Cromer, Chiara Speziale, Calum J. Drummond, Raffaele MezzengaAbstract:In meso crystallization of membrane proteins from lipidic mesophases is central to protein structural biology but limited to membrane proteins with small extracellular domains (ECDs), comparable to the water channels (3-5 nm) of the mesophase. Here we present a strategy expanding the scope of in meso crystallization to membrane proteins with very large ECDs. We combine monoacylglycerols and phospholipids to design thermodynamically stable ultra-swollen bicontinuous cubic phases of double-gyroid (Ia3d), double-diamond (Pn3m), and double-primitive (Im3m) space groups, with water channels five times larger than traditional lipidic mesophases, and showing re-entrant behavior upon increasing hydration, of sequences Ia3d→Pn3m→Ia3d and Pn3m→Im3m→Pn3m, unknown in lipid self-assembly. We use these mesophases to crystallize membrane proteins with ECDs inaccessible to conventional in meso crystallization, demonstrating the methodology on the Gloeobacter ligand-gated ion channel (GLIC) protein, and show substantial modulation of packing, molecular contacts and activation state of the ensued proteins crystals, illuminating a general strategy in protein structural biology.
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Design of ultra-swollen lipidic mesophases for the crystallization of membrane proteins with large extracellular domains
Nature Communications, 2018Co-Authors: Alexandru Zabara, Josephine Tse Yin Chong, Isabelle Martiel, Laura Stark, Brett A. Cromer, Chiara Speziale, Calum J. Drummond, Raffaele MezzengaAbstract:In meso crystallization of membrane proteins is limited to proteins with small extracellular domains (ECDs). Here, authors combine monoacylglycerols and phospholipids to design stable ultra-swollen bicontinuous cubic phases that allow in meso crystallization of proteins with large ECDs. In meso crystallization of membrane proteins from lipidic mesophases is central to protein structural biology but limited to membrane proteins with small extracellular domains (ECDs), comparable to the water channels (3–5 nm) of the mesophase. Here we present a strategy expanding the scope of in meso crystallization to membrane proteins with very large ECDs. We combine monoacylglycerols and phospholipids to design thermodynamically stable ultra-swollen bicontinuous cubic phases of double-gyroid ( Ia3d ), double-diamond ( Pn3m ), and double-primitive ( Im3m ) space groups, with water channels five times larger than traditional lipidic mesophases, and showing re-entrant behavior upon increasing hydration, of sequences Ia3d → Pn3m → Ia3d and Pn3m → Im3m → Pn3m , unknown in lipid self-assembly. We use these mesophases to crystallize membrane proteins with ECDs inaccessible to conventional in meso crystallization, demonstrating the methodology on the Gloeobacter ligand-gated ion channel (GLIC) protein, and show substantial modulation of packing, molecular contacts and activation state of the ensued proteins crystals, illuminating a general strategy in protein structural biology.
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Enzyme Kinetics in Liquid Crystalline Mesophases: Size Matters, But Also Topology
Langmuir : the ACS journal of surfaces and colloids, 2015Co-Authors: Wenjie Sun, Jijo J. Vallooran, Raffaele MezzengaAbstract:Lyotropic liquid crystalline systems (LLCs) are excellent immobilizing carriers for enzymes, due to their biocompatibility and well-defined pore nanostructure. Here we show that the liquid crystalline mesophase topology can greatly influence the enzymatic activity in a typical peroxidase (Horseradish peroxidase, HRP) enzymatic reaction. Enzyme kinetics was investigated in different LLC mesophases based on monolinolein, with varying symmetries and dimensions such as the 1D cylindrical inverse hexagonal phase (HII), the 2D planar lamellar phase (Lα), and two 3D bicontinuous cubic phases of double diamond (Pn3m) and gyroid (Ia3d) space groups. As expected, the mesophase with largest water channel size shows highest activity, regardless of the topology. Interestingly, however, when mesophases with different topologies have the same water channel size, then the topology plays the dominant role, and the enzyme showed the highest activity in the 3D tetra-fold connected Pn3m, followed by the Ia3d with trifold connectivity, and finally the 1D HII phase. This study demonstrates that the enzymatic activity in LLC mesophases depends on both the water channel size and the topology of the mesophase.
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Perforated Bicontinuous Cubic Phases with pH‐Responsive Topological Channel Interconnectivity
Small (Weinheim an der Bergstrasse Germany), 2013Co-Authors: Alexandru Zabara, Renata Negrini, Ozana Onaca-fischer, Raffaele MezzengaAbstract:Lipidic lyotropic liquid crystals are at the frontline of current research for release of target therapeutic molecules due to their unique structural complexity and the possibility of engineering stimuli-triggered release of both hydrophilic and hydrophobic molecules. One of the most suitable lipidic mesophases for the encapsulation and delivery of drugs is the reversed double diamond bicontinuous cubic phase, in which two distinct and parallel networks of ∼4 nm water channels percolate independently through the lipid bilayers, following a Pn3m space group symmetry. In the unperturbed Pn3m structure, the two sets of channels act as autonomous and non-communicating 3D transport pathways. Here, a novel type of bicontinuous cubic phase is introduced, where the presence of OmpF membrane proteins at the bilayers provides unique topological interconnectivities among the two distinct sets of water channels, enabling molecular active gating among them. By a combination of small-angle X-ray scattering, release and ion conductivity experiments, it is shown that, without altering the Pn3m space group symmetry or the water channel diameter, the newly designed perforated bicontinuous cubic phase attains transport properties well beyond those of the standard mesophase, allowing faster, sustained release of bioactive target molecules. By further exploiting the pH-mediated pore-closing response mechanism of the double amino acid half-ring architecture in the membrane protein, the pores of the perforated mesophase can be opened and closed with a pH trigger, enabling a fine modulation of the transport properties by only moderate changes in pH, which could open unexplored opportunities in the targeted delivery of bioactive compounds.
P. Pieranski - One of the best experts on this subject based on the ideXlab platform.
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Symmetry, topology and faceting in bicontinuous lyotropic crystals
The European Physical Journal E, 2013Co-Authors: L. Latypova, W. Góźdź, P. PieranskiAbstract:Phase diagrams of phytantriol/ethanol/water and phytantriol/DSPG/ethanol/water systems are explored and experiments on facetings of Pn3m-in-L1 and Im3m-in-L1 crystals are performed. Observed crystal habits do not agree with the Friedel-Donnay-Harker rules. We argue that this paradox can be explained in terms of constraints imposed on Pn3m/L1 and Im3m/L1 interfaces by the bicontinuous topology of the cubic phases. We point out that when free edges of the surfactant bilayer are prohibited at these interfaces, the two labyrinthes separated by the bilayer cannot anymore be equivalent. The corresponding $ {\rm Pn3m}\rightarrow {\rm Fd3m}$ and $ {\rm Im3m}\rightarrow {\rm Pm3m}$ symmetry breakings are unveiled by the abnormal facetings. Graphical abstract
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Anisotropic surface melting in lyotropic cubic crystals
The European Physical Journal E, 2006Co-Authors: S. Leroy, D. Rohe, J. Grenier, C. Even, P. PieranskiAbstract:From experiments with metal crystals, in the vicinity of their crystal/liquid/vapor triple points, it is known that melting of crystals starts on their surfaces and is anisotropic. Recently, we have shown that anisotropic surface melting occurs also in lyotropic systems. In our previous paper (Eur. Phys. J. E 19 , 223 (2006)), we have focused on the case of poor faceting at the Pn3m/L1 interface in C12EO2/water binary mixtures. There anisotropic melting occurs in the vicinity of a Pn3m/L3/L1 triple point. In the present paper, we focus on the opposite case of a rich devil's-staircase-type faceting at Ia3d/vapor interfaces in monoolein/water and phytantriol/water mixtures. We show that anisotropic surface melting takes place in these systems in a narrow humidity range close to the Ia3d-L2 transition. As whole ( hkl ) sets of facets disappear one after another when the transition is approached, surface melting occurs in a facet-by-facet type.
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Anisotropic surface melting in lyotropic cubic crystals
The European Physical Journal E, 2006Co-Authors: J. Grenier, T. Plötzing, D. Rohe, P. PieranskiAbstract:From experiments with ice or metal crystals, in the vicinity of their crystal/liquid/vapor triple points, it is known that melting of crystals starts on their surfaces and is anisotropic. It is shown here by direct observations under an optical microscope that this anisotropic surface melting phenomenon occurs also in lyotropic systems. In the case of C12EO2/water mixture, it takes place in the vicinity of the peritectic Pn3m/L3/L1 triple point. Above the peritectic triple point, where the Pn3m and L1 phases coexist in the bulk, the surface of a Pn3m-in-L1 crystal is composed of (111)-type facets surrounded by rough surfaces. The angular junction suggests that rough surfaces are wet by a L3-like layer while facets stay “dry”. This is analogous to the pre-melting at rough surfaces in solid crystals. Upon cooling below the peritectic triple point, where L3 and L1 phases coexist in the bulk, a thick layer of the L3 phase grows from the pre-melted, rough Pn3m/L1 interface. Simultaneously, facets stay dry and their radius decreases. In this tri-phasic configuration, stable in a narrow temperature range, the L3/L1 and L3/Pn3m interfaces have shapes of constant mean curvature surfaces having common borders: edges of facets.
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Ratchet effect in faceting
The European Physical Journal E, 2004Co-Authors: T. Plötzing, P. PieranskiAbstract:The paper deals with a new phenomenon, named ratchet effect, envisioned theoretically as a likely consequence of metastability of crystal facets and expected to occur upon a temperature cycling. In experiments, Pn3m lyotropic crystals surrounded by the isotropic L1 phase in the mixture C_12EO_2/water are used. At equilibrium, the Pn3m/L1 interface contains small (111)-type facets in coexistence with rough surfaces. In agreement with theoretical expectations, it is shown that upon a saw-tooth-shaped temperature cycling, facets are growing until the rough surfaces are completely eliminated. A model of the ratchet effect is proposed.
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A growth of perfect lyotropic crystals by temperature cycles
2004Co-Authors: P. PieranskiAbstract:The paper deals with a new phenomenon, named ratchet effect, envisioned theoretically as a likely consequence of metastability of crystal facets and expected to occur upon a temperature cycling. In experiments, Pn3m lyotropic crystals surrounded by the isotropic L1 phase in the mixture C12EO2/water are used. At equilibrium, the Pn3m/L1 interface contains small (111)-type facets in coexistence with rough surfaces. In agreement with theoretical expectations, it is shown that upon a saw-tooth-shaped temperature cycling, facets are growing until the rough surfaces are completely eliminated. A model of the ratchet effect is proposed.
Pawel Pieranski - One of the best experts on this subject based on the ideXlab platform.
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Facets of lyotropic liquid crystals.
Langmuir : the ACS journal of surfaces and colloids, 2014Co-Authors: L. Latypova, Wojciech T. Góźdź, Pawel PieranskiAbstract:The bicontinuous lyotropic liquid phases surrounded by the isotropic phase form monocrystals with well-developed facets. We investigate the structure and stability of the facets formed by the bicontinuous phase of Pn3m symmetry, at three preferred directions, which are developed on a spherical droplet of Pn3m phase surrounded by the isotropic phase. The structure of the facets is obtained by minimization of the Landau–Brazovskii functional with one scalar order parameter.
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Anisotropic surface melting in lyotropic cubic crystals: part 2: facet-by-facet melting at Ia3d/vapor interfaces.
The European physical journal. E Soft matter, 2006Co-Authors: S. Leroy, D. Rohe, J. Grenier, C. Even, Pawel PieranskiAbstract:From experiments with metal crystals, in the vicinity of their crystal/liquid/vapor triple points, it is known that melting of crystals starts on their surfaces and is anisotropic. Recently, we have shown that anisotropic surface melting occurs also in lyotropic systems. In our previous paper (Eur. Phys. J. E 19 , 223 (2006)), we have focused on the case of poor faceting at the Pn3m/L1 interface in C12EO2/water binary mixtures. There anisotropic melting occurs in the vicinity of a Pn3m/L3/L1 triple point. In the present paper, we focus on the opposite case of a rich devil's-staircase-type faceting at Ia3d/vapor interfaces in monoolein/water and phytantriol/water mixtures. We show that anisotropic surface melting takes place in these systems in a narrow humidity range close to the Ia3d-L2 transition. As whole (hkl ) sets of facets disappear one after another when the transition is approached, surface melting occurs in a facet-by-facet type.
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Anisotropic surface melting in lyotropic cubic crystals. Part 1: Pn3m/L1 interface, poor faceting.
The European physical journal. E Soft matter, 2006Co-Authors: J. Grenier, T. Plötzing, D. Rohe, Pawel PieranskiAbstract:From experiments with ice or metal crystals, in the vicinity of their crystal/liquid/vapor triple points, it is known that melting of crystals starts on their surfaces and is anisotropic. It is shown here by direct observations under an optical microscope that this anisotropic surface melting phenomenon occurs also in lyotropic systems. In the case of C12EO2/water mixture, it takes place in the vicinity of the peritectic Pn3m/L3/L1 triple point. Above the peritectic triple point, where the Pn3m and L1 phases coexist in the bulk, the surface of a Pn3m-in-L1 crystal is composed of (111)-type facets surrounded by rough surfaces. The angular junction suggests that rough surfaces are wet by a L3-like layer while facets stay “dry”. This is analogous to the pre-melting at rough surfaces in solid crystals. Upon cooling below the peritectic triple point, where L3 and L1 phases coexist in the bulk, a thick layer of the L3 phase grows from the pre-melted, rough Pn3m/L1 interface. Simultaneously, facets stay dry and their radius decreases. In this tri-phasic configuration, stable in a narrow temperature range, the L3/L1 and L3/Pn3m interfaces have shapes of constant mean curvature surfaces having common borders: edges of facets.
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anisotropic surface melting in lyotropic cubic crystals part 1 Pn3m l1 interface poor faceting
European Physical Journal E, 2006Co-Authors: J. Grenier, T. Plötzing, D. Rohe, Pawel PieranskiAbstract:From experiments with ice or metal crystals, in the vicinity of their crystal/liquid/vapor triple points, it is known that melting of crystals starts on their surfaces and is anisotropic. It is shown here by direct observations under an optical microscope that this anisotropic surface melting phenomenon occurs also in lyotropic systems. In the case of C12EO2/water mixture, it takes place in the vicinity of the peritectic Pn3m/L3/L1 triple point. Above the peritectic triple point, where the Pn3m and L1 phases coexist in the bulk, the surface of a Pn3m-in-L1 crystal is composed of (111)-type facets surrounded by rough surfaces. The angular junction suggests that rough surfaces are wet by a L3-like layer while facets stay “dry”. This is analogous to the pre-melting at rough surfaces in solid crystals. Upon cooling below the peritectic triple point, where L3 and L1 phases coexist in the bulk, a thick layer of the L3 phase grows from the pre-melted, rough Pn3m/L1 interface. Simultaneously, facets stay dry and their radius decreases. In this tri-phasic configuration, stable in a narrow temperature range, the L3/L1 and L3/Pn3m interfaces have shapes of constant mean curvature surfaces having common borders: edges of facets.
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Ratchet effect in faceting: a growth of perfect lyotropic crystals by temperature cycles.
The European physical journal. E Soft matter, 2004Co-Authors: T. Plötzing, Pawel PieranskiAbstract:The paper deals with a new phenomenon, named ratchet effect, envisioned theoretically as a likely consequence of metastability of crystal facets and expected to occur upon a temperature cycling. In experiments, Pn3m lyotropic crystals surrounded by the isotropic L1 phase in the mixture C12EO2/water are used. At equilibrium, the Pn3m/L1 interface contains small (111)-type facets in coexistence with rough surfaces. In agreement with theoretical expectations, it is shown that upon a saw-tooth-shaped temperature cycling, facets are growing until the rough surfaces are completely eliminated. A model of the ratchet effect is proposed.
Hiroshi Takahashi - One of the best experts on this subject based on the ideXlab platform.
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Water isotope effect on the lipidic cubic phase: Heavy water-Induced interfacial area reduction of monoolein-Water system.
Chemistry and physics of lipids, 2017Co-Authors: Hiroshi Takahashi, Kotaro JojikiAbstract:Heavy water (D2O) affects various functions of cells and living things. In order to gain fundamental insight into the molecular mechanism on biological effects of heavy water, D2O-effects on fully hydrated monoolein (MO) systems were investigated from the structural viewpoints. At room temperature, the MO fully hydrated by pure light water (H2O) forms a bicontinuous cubic (Pn3m) phase, and then, the Pn3m cubic phase transforms into an inverted hexagonal (HII) phase at about 90°C. Temperature-scan X-ray diffraction measurements showed that substitution of D2O for H2O lowers the Pn3m-to-HII phase transition temperature and reduces the lattice constants of both phases. The structural analysis of the Pn3m phase using the diffraction intensity data indicated that D2O reduces the surface occupied area of MO at the interface by 12% in comparison with H2O. This change is probably due to the difference of the strength of hydrogen bond.
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A comparative study of the effects of dimethylsulfoxide and glycerol on the bicontinuous cubic structure of hydrated monoolein and its phase behavior.
Chemistry and physics of lipids, 2007Co-Authors: Satoru Abe, Hiroshi TakahashiAbstract:Both dimethylsulfoxide (DMSO) and glycerol act cryoprotectants for biological systems and materials. Knowledge of molecular interactions of DMSO and glycerol with biological lipids is important for understanding of their cryoprotecitive mechanisms. In this study, the phase behavior and structures of hydrated monoolein were investigated in the presence of DMSO or glycerol, using differential scanning calorimetry (DSC) and simultaneous X-ray diffraction/DSC measurements. Based on the results obtained by this study, partial phase diagrams were constructed as a function of DMSO or glycerol concentrations and temperature. DMSO and glycerol hardly affect the enthalpy value for melting temperature of lamellar crystal phase of monoolein and the structure. On the other hand, DMSO and glycerol greatly affect the phase transformations associated with bicontinuous cubic phases of monoolein and the cubic phase structures. DMSO expands Im3m/Pn3m cubic phase co-existence region in the phase diagram and increases the lattice constant of the Pn3m monoolein cubic phase. Glycerol shows opposite effects. The present study suggests that different mechanisms act in the cryopreservation by DMSO and glycerol.
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effects of salt on the lamellar and bicontinuous cubic phases of fully hydrated monoacylglycerol monoelaidin
Physical Chemistry Chemical Physics, 2002Co-Authors: Hiroshi Takahashi, Akira Matsuo, Ichiro HattaAbstract:The effects of various sodium salts on the phase behavior of monoacylglycerol were investigated for fully hydrated monoelaidin systems by means of X-ray diffraction and differential scanning calorimetry. The hydrated monoelaidin systems form lamellar and bicontinuous cubic phases, depending on the temperature. Calorimetric data showed that the sign and magnitude of the phase transition temperature shifts on addition of salts are consistent with the Hofmeister series which is determined according to the efficiency of salting-out of proteins. Kosmotropic salts, having a great ability for the salting-out of proteins, increase the lamellar gel to lamellar liquid crystalline phase transition temperatures and decrease the primitive cubic to body-centered cubic (Im3m to Pn3m) phase transition temperatures. On the other hand, chaotropic salts, having a weak ability for the salting-out of proteins, exhibit the opposite effect. X-ray diffraction data demonstrated that chaotropic salts expand the lattice constants of fully hydrated monoelaidin in the Pn3m cubic phase whereas kosmotropic salts reduce the lattice constants. The above results are discussed in comparison with previous results reported for phospholipids and glycolipids. In addition, the structures of the cubic phases are discussed, based upon the above results.