“…In this study, we have focused on the product end of the process, that is, MO, OA, and oleate, to facilitate the interpretation of the data. The effect of lipase action on (1) MO− 2 H 2 O-based bicontinuous cubic lc phases, − (2) MO− 2 H 2 O-based cubic dispersions, , and (3) MO− 2 H 2 O-based vesicles 14 in relation to lipid self-assembly has been reported previously. The bicontinuity and the ability to incorporate other molecules are important features of the monoglyceride-based cubic phases that have been suggested to facilitate the lipolysis process…”
This study deals with the interplay between the interfacial structure of lipid liquid crystalline (lc) substrates and the lipolysis rate. Thermomyces (formerly Humicola) lanuginosa lipase (TLL) was added to lamellar (LR), reversed bicontinuous cubic (C), and reversed hexagonal (HII) lc phases, based on monoolein (MO), MO-sodium oleate (NaO), MO-oleic acid (OA), and MO-diolein (DO) with water. The changes in self-assembled structure and lipid composition during lipolytic processes were followed by polarizing microscopy, small-angle X-ray diffraction, and high-performance liquid chromatography (HPLC). Indeed, the observed changes in self-assembled structures could be predicted from either the MO-OA-2 H2O ternary phase diagram, where the lipolysis gives rise to a transition of C f HII f micellar cubic (Cmic) f reversed micellar phase + dispersion, or the MO-NaO-2 H2O ternary phase diagram, where the corresponding sequence is LR f HI. These observations are discussed in terms of the degree of protonation of the fatty acid. The specific activity of TLL on the CD and OA-HII samples as determined from the lipolysis rate was found to be the similar under the employed experimental conditions. The HPLC data showed that the ratio between the substrate (MO/DO) and final product (OA) approached about the same values regardless of the initial substrate composition and structure.
“…In this study, we have focused on the product end of the process, that is, MO, OA, and oleate, to facilitate the interpretation of the data. The effect of lipase action on (1) MO− 2 H 2 O-based bicontinuous cubic lc phases, − (2) MO− 2 H 2 O-based cubic dispersions, , and (3) MO− 2 H 2 O-based vesicles 14 in relation to lipid self-assembly has been reported previously. The bicontinuity and the ability to incorporate other molecules are important features of the monoglyceride-based cubic phases that have been suggested to facilitate the lipolysis process…”
This study deals with the interplay between the interfacial structure of lipid liquid crystalline (lc) substrates and the lipolysis rate. Thermomyces (formerly Humicola) lanuginosa lipase (TLL) was added to lamellar (LR), reversed bicontinuous cubic (C), and reversed hexagonal (HII) lc phases, based on monoolein (MO), MO-sodium oleate (NaO), MO-oleic acid (OA), and MO-diolein (DO) with water. The changes in self-assembled structure and lipid composition during lipolytic processes were followed by polarizing microscopy, small-angle X-ray diffraction, and high-performance liquid chromatography (HPLC). Indeed, the observed changes in self-assembled structures could be predicted from either the MO-OA-2 H2O ternary phase diagram, where the lipolysis gives rise to a transition of C f HII f micellar cubic (Cmic) f reversed micellar phase + dispersion, or the MO-NaO-2 H2O ternary phase diagram, where the corresponding sequence is LR f HI. These observations are discussed in terms of the degree of protonation of the fatty acid. The specific activity of TLL on the CD and OA-HII samples as determined from the lipolysis rate was found to be the similar under the employed experimental conditions. The HPLC data showed that the ratio between the substrate (MO/DO) and final product (OA) approached about the same values regardless of the initial substrate composition and structure.
“…In particular it is the exemplar of those amphiphiles that will form inverse bicontinuous cubic phases − (Figure ). It is this propensity for forming these beautiful, ordered, spongelike phases that has attracted scientists to study the origins of its rich mesomorphic behavior − , for its use in crystalizing membrane proteins and to attempt to make use of the unique potential of the structural properties of the inverse bicontinuous cubic phases found in MO. − 1 The phase diagram of monoolein derived from the data of Briggs, Chung, and Caffrey, where L 2 is the inverse micellar phase; L α is the fluid lamellar phase; L c is the lamellar crystal phase; and are the inverse bicontinuous cubic phases based upon the gyroid and D minimal surfaces, respectively and H II is the inverse hexagonal phase. The regions of phase coexistence are unmarked, except for those regions where coexistence is with excess water. 2 The inverse bicontinuous cubic phases.…”
The bending elasticity of the monoglyceride 1-monoolein (MO) in water has been measured in the inverse
hexagonal (HII) phase at 37 °C. At this temperature, fully hydrated MO is normally in an inverse bicontinuous
cubic phase based on Schwarz's D surface,
. The addition of either of the C23 chainlength hydrocarbons,
tricosane or 9-cis-tricosene, at mole fractions with respect to MO in excess of 0.05, induces a phase transition
into the HII phase. This transition is understood to occur because packing stresses in the hydrophobic
regions of the HII phase are reduced to levels where this phase is at a lower free energy than the
phase.
We have used X-ray diffraction on gravimetrically prepared samples and samples subjected to an osmotic
stress to determine the bending energy of MO in this phase. The evidence suggests that 9-cis-tricosene
can relieve almost all of the packing stress in the HII phase. In this case, we find that the spontaneous
radius of curvature at the pivotal surface, R
0, is −20.0 ± 0.3 Å, and the monolayer bending rigidity, κ, is
(1.2 ± 0.1) × 10-20 J. Comparing these energetics with those of the
phase indicates that the packing
stress for an excess water, HII phase at 37 °C in the absence of 9-cis-tricosene would constitute at least
50% of the total equilibrium free energy. With tricosane, the packing stress cannot be completely relieved
because tricosane melts at 47.6 °C in the bulk. The results from geometric measurements on this system
suggest that when the packing stress is not fully relieved in the HII phase, the polar/apolar interface is
deformed away from being cylindrical. Treating the interface as if it were cylindrical leads to a nonphysical
location of the pivotal surface that is in disagreement with all previous measurements, a 35% increase
in the magnitude of R
0, and a 4-fold increase in the calculated bending rigidity.
“…The fact that lipids hydrated in water may form not only bilayer membranes but also nonlamellar lipid phases, − which could affect the functioning of embedded or adsorbed proteins, has attracted significant research interest. − More often, techniques for the encapsulation of water-soluble (rather than of membrane-soluble) proteins into lyotropic phases formed by nonlamellar lipids have been reported. Thus, a variety of purified proteins, such as cytochrome c, , lysozyme, , casein, α-chymotrypsin, hemoglobin, lipase from Humicola lanuginosa , and so forth have been directly encapsulated into lipid/water phases of cubic symmetries without using detergents. 1 CPK molecular models of n -octyl β- d -glucopyranoside (OG), monoolein (MO), dioleoylphosphatidylethanolamine (DOPE), and dipalmitoylphosphatidylcholine (DPPC).…”
The phase behavior and structural parameters of dioleoylphosphatidylethanolamine (DOPE), monoolein (MO), and dipalmitoylphosphatidylcholine (DPPC) hydrated in excess aqueous phase containing micellar octyl glucoside (OG) were investigated by means of synchrotron X-ray diffraction in a wide range of temperatures. The lipid-to-detergent molar ratios were selected to be equal to those in a recent membraneprotein-reconstitution study. It was established that lipids displaying either nonlamellar (DOPE and MO) or lamellar propensities (DPPC) form mixed supramolecular structures with the detergent OG. The phase states and structures of these mixed assemblies are essentially different from those of the pure lipid components. At full hydration and at the investigated lipid-to-detergent molar ratios, OG destabilizes the inverted-hexagonal (HII) phase organization of DOPE and the inverted cubic (Q 224 ) structure of MO, transforming them into a lamellar liquid crystalline (LR) phase. The fluid DOPE/OG and MO/OG bilayers totally accommodate the micellar OG from the aqueous phase, as evidenced by the absence of diffuse scattering of OG or lipid/OG micelles. In the temperature interval from 0 to 52 °C, the investigated DOPE/ OG/water and MO/OG/water systems are in the lamellar LR state and do not undergo structural phase transitions. The DPPC/OG/water system undergoes a phase transition from a gel to a liquid-crystalline phase state. Due to the particular molar amount of OG in this system, a coexistence of mixed DPPC/OG bilayers and DPPC/OG micelles was found. The structural results suggest that the DOPE/OG and MO/OG systems, which are of lamellar rather than of nonlamellar organizations, are suitable for reconstitution of membrane proteins, as was established for DPPC/OG membranes.
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