A cubic structure consisting of a lipid bilayer forming an infinite periodic minimum surface of the gyroid type in the glycerolmonooleat-water system

Hyde, Stephen T.; Andersson, Sten; Ericsson, Bodil; Larsson, Kåre

doi:10.1524/zkri.1984.168.1-4.213

Cited by 451 publications

(349 citation statements)

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“…[1][2][3][4][5][6][7] Of particular interest are the inverse (or type II) bicontinuous cubic phases Q G II (of cubic symmetry Ia 3d), Q D II (Pn 3m) and Q P II (Im 3m), where the spatial structure is a lipid bilayer draped on a triply-periodic minimal surface; the aqueous domain consists of two network-like components, separated by the bilayer, see Fig. 2.…”

Section: Introductionmentioning

confidence: 99%

Polycontinuous geometries for inverse lipid phases with more than two aqueous network domains

et al. 2013

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Inverse bicontinuous cubic phases with two aqueous network domains separated by a smooth bilayer are firmly established as equilibrium phases in lipid/water systems. The purpose of this article is to highlight the generalisations of these bicontinuous geometries to polycontinuous geometries, which could be realised as lipid mesophases with three or more network-like aqueous domains separated by a branched bilayer. An analysis of structural homogeneity in terms of bilayer width variations reveals that ordered polycontinuous geometries are likely candidates for lipid mesophase structures, with similar chain packing characteristics to the inverse micellar phases (that once were believed not to exist due to high packing frustration). The average molecular shape required by global geometry to form these multi-network phases is quantified by the surfactant shape parameter, v/(al); we find that it adopts values close to those of the known lipid phases. We specifically analyse the 3etc(187 193) structure of hexagonal symmetry P6 3 /mcm with three aqueous domains, the 3dia(24 220) structure of cubic symmetry I 43d composed of three distorted diamond networks, the cubic chiral 4srs(24 208) with cubic symmetry P4 2 32 and the achiral 4srs(5 133) structure of symmetry P4 2 /nbc, each consisting of four intergrown undistorted copies of the srs net (the same net as in the Q G II gyroid phase). Structural homogeneity is analysed by a medial surface approach assuming that the headgroup interfaces are constant mean curvature surfaces. To facilitate future experimental identification, we provide simulated SAXS scattering patterns that, for the 4srs(24 208) and 3dia(24 220) structures, bear remarkable similarity to those of bicontinuous Q G II -gyroid and Q D II -diamond phases, with comparable lattice parameters and only a single peak that cannot be indexed to the wellestablished structures. While polycontinuous lipid phases have, to date, not been reported, the likelihood of their formation is further indicated by the reported observation of a solid tricontinuous mesoporous silicate structure, termed IBN-9, which formed in the presence of surfactants [Han et al

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Section: Introductionmentioning

confidence: 99%

Polycontinuous geometries for inverse lipid phases with more than two aqueous network domains

et al. 2013

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“…The thermally reversible binding of water to the head is a key component of the model, which also influences the head-water and the head-tail interactions. Experimental results on monoolein [8,9] and monolinolein [21] systems suggest that in the bound and hydrated state, the larger state 1 head should interact less favorably with free(unbound) water and lipid tails than a head in the dry state 0.…”

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confidence: 99%

“…While cubic phases are desirable, there is very limited understanding of the relationship between the molecular details of the lipid, its interactions with water, and the presence and placement of cubic phases within the temperature-composition plane. The problem is particularly acute for aqueous solutions of nonionic lipids with a small hydrophilic head, such as the monooleinwater system [8,9]. This class of lipid-water mixtures possesses both a normal phase sequence from inverted hexagonal cylinders to inverted cubic gyroid (H II -Ia 3d II ) and a reverse phase sequence from lamellar to inverted gyroid (L -Ia 3d II ) as the water volume fraction is increased [see Fig.…”

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Anomalous Phase Sequences in Lyotropic Liquid Crystals

2007

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We present a coarse-grained model in order to describe the unusual sequence of mesophases observed in aqueous solutions of nonionic lipids, such as monoolein. The lipid molecules are modeled as a rigid head and a flexible Gaussian tail, and water is treated explicitly. A key component of the model is thermally reversible hydrogen bonding between the lipid head and water resulting in changes in both head volume and the interactions of the hydrated head with its surroundings. Phase diagrams obtained from unit-cell self-consistent field simulations capture the qualitative thermotropic and lyotropic phase behavior of the monoolein-water system. The unusual phase sequences result from a competition between hydrogen bond formation, changes in head volume and interactions, lipid tail entropy, and the hydrophobic effect. [3,4,7]. While cubic phases are desirable, there is very limited understanding of the relationship between the molecular details of the lipid, its interactions with water, and the presence and placement of cubic phases within the temperature-composition plane. The problem is particularly acute for aqueous solutions of nonionic lipids with a small hydrophilic head, such as the monooleinwater system [8,9]. This class of lipid-water mixtures possesses both a normal phase sequence from inverted hexagonal cylinders to inverted cubic gyroid (H II -Ia 3d II ) and a reverse phase sequence from lamellar to inverted gyroid (L -Ia 3d II ) as the water volume fraction is increased [see Fig. 2(a)]. There is currently no satisfactory theoretical model that explains both the normal and reverse lyotropic phase sequences as well as the changing topology of the phase diagram with temperature. It is this challenge that is addressed in the present Letter.The concept of a critical packing parameter (CCP) [10], defined as the ratio of the volume of a lipid tail to the product of the cross-sectional area of a lipid head and the length of a lipid molecule, is a useful tool for anticipating membrane curvature and the stability of various lipid and surfactant phases in solution. Nonetheless, the CCP approach predicts only the normal sequence of phases, reflecting a transition in which the water-lipid interfaces are curved less towards the water domains as the concentration of water is increased. The framework does not provide insight into a reverse phase transition such as L ! Ia 3d II , where the interfaces go from flat to curved towards water upon increasing the amount of water.A membrane elasticity model for lipid bilayers initiated by Canham and Helfrich [11,12] invokes phenomenological parameters such as spontaneous curvature, bending rigidity and saddle splay modulus. The model does not elucidate the dependence of these parameters on molecular details of the lipid and solvent, but it can be used to anticipate certain trends in phase behavior [13]. At the other extreme, fully atomistic simulations have been attempted for the monoolein-water system using a classical force field and explicit water [14]. While some promising ...

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“…That was the first hint I had of the existence of crystalline matter that incorporates the geometry of an enantiomorphic pair of Laves graphs. The first significant report of the gyroid in liquid crystals was an article by Stephen Hyde et al [50]. Additional recommended readings are in [51][52][53].…”

Section: Discussion Triply-periodic Minimal Surfaces a H Schoen 663mentioning

confidence: 99%

Reflections concerning triply-periodic minimal surfaces

Schoen

2012

Interface Focus.

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In recent decades, there has been an explosion in the number and variety of embedded triplyperiodic minimal surfaces (TPMS) identified by mathematicians and materials scientists. Only the rare examples of low genus, however, are commonly invoked as shape templates in scientific applications. Exact analytic solutions are now known for many of the low genus examples. The more complex surfaces are readily defined with numerical tools such as SURFACE EVOLVER software or the Landau -Ginzburg model. Even though table-top versions of several TPMS have been placed within easy reach by rapid prototyping methods, the inherent complexity of many of these surfaces makes it challenging to grasp their structure.

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A cubic structure consisting of a lipid bilayer forming an infinite periodic minimum surface of the gyroid type in the glycerolmonooleat-water system

Cited by 451 publications

References 5 publications

Polycontinuous geometries for inverse lipid phases with more than two aqueous network domains

Polycontinuous geometries for inverse lipid phases with more than two aqueous network domains

Anomalous Phase Sequences in Lyotropic Liquid Crystals

Reflections concerning triply-periodic minimal surfaces

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