X-ray diffraction study of the polymorphic behavior of N-methylated dioleoylphosphatidylethanolamine

Grüner, Sol M.; Täte, Mark W.; Kirk, Gregory; So, Peter T. C.; Turner, David C.; Keane, Denis T.; Tilcock, Colin; Cullis, Pieter R.

doi:10.1021/bi00408a029

Cited by 268 publications

(234 citation statements)

References 59 publications

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“…This plot was utilized to calculate a lattice spacing of 13.7 nm for the Pn3m phase. This value is in the same range as reported previously (12.5-14 nm) for PE lipids adopting the Pn3m space group (Gruner et al 1988). However, besides the Pn3m, remnants of the lamellar phase still were observed.…”

Section: Saxssupporting

confidence: 90%

Serum-free transfection of CHO-cells with tailor-made unilamellar vesicles

et al. 2007

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At present, a number of transfection techniques are available to introduce foreign DNA into cells, but still minimal intrusion or interference with normal cell physiology, low toxicity, reproducibility, cost efficiency and successful creation of stable transfectants are highly desirable properties for improved transfection techniques.For all previous transfection experiments done in our labs, using serum-free cultivated host cell lines, an efficiency value of *0.1% for selection of stable cell lines has not been exceeded, consequently we developed and improved a transfection system based on defined liposomes, so-called large unilamellar vesicles, consisting of different lipid compositions to facilitate clone selection and increase the probability for creation of recombinant high-production clones.DNA and DOTAP/DOPE or CHEMS/DOPE interact by electrostatic means forming so-called lipoplexes (Even-Chen and Barenholz 2000) and the lipofection efficiency of those lipoplexes has been determined via confocal microscopy.In addition, the expression of the EGFP was determined by FACS to investigate transient as well as stable transfection and the transfection efficiency of a selection of different commercially available transfection reagents and kits has been compared to our tailor-made liposomes.

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Section: Saxssupporting

confidence: 90%

Serum-free transfection of CHO-cells with tailor-made unilamellar vesicles

et al. 2007

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“…To date the most convincing evidence has been structural evidence that is consistent with the existence of fusion stalks [14]. As for the structural dynamics, a limited amount of experimental work has been carried out on the lamellar to inverse bicontinuous cubic phase transition [15][16][17][18][19]. The major problem to date with these dynamical studies is the lack of reproducibility in results [20,21].…”

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confidence: 99%

Dynamics of Structural Transformations between Lamellar and Inverse Bicontinuous Cubic Lyotropic Phases

et al. 2006

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The liquid crystalline lamellar (L ) to double-diamond inverse bicontinuous cubic (Q D II ) phase transition for the amphiphile monoelaidin in excess water exhibits a remarkable sequence of structural transformations for pressure or temperature jumps. Our data imply that the transition dynamics depends on a coupling between changes in molecular shape and the geometrical and topological constraints of domain size. We propose a qualitative model for this coupling based on theories of membrane fusion via stalks and existing knowledge of the structure and energetics of bicontinuous cubic phases. DOI: 10.1103/PhysRevLett.96.108102 PACS numbers: 87.16.Dg, 61.10.Eq, 87.17.Ee, 64.70.Md Lyotropic liquid crystalline phases form when amphiphilic molecules are mixed with a polar solvent [1,2]. The many structures they can adopt, their complex phase behavior and their energetics have received a great deal of attention over the past half century. Much is now understood about their equilibrium behavior and this has informed the development of surfactant technologies and our understanding of how amphiphiles in biological membranes can control biochemical activity [3,4]. By comparison the study of the nonequilibrium structure and dynamics of lyotropic liquid crystalline systems is in its infancy and little is understood about the mechanisms by which one phase transforms into another [5,6]. Understanding the dynamics of lyotropic phase transformations is of practical interest for applications where amphiphilic materials are processed and of relevance in biological systems where membrane fusion or division occurs.The present work focuses on a phase transition where membrane fusion occurs: the fluid lamellar to inverse bicontinuous cubic phase transition, Fig. 1. Models for the process of membrane fusion between apposed lipid bilayers have been proposed by a number of groups [7][8][9]. All rely on the formation of transient lipid contacts known as stalks, which subsequently break through to form the beginnings of the tubular connections that are the fundamental connecting element in the inverse bicontinuous cubic phases. Recent theoretical models of the structure and energy of the stalk have incorporated both elastic energy, accounting for the splay, saddle splay, and tilt deformations of the membrane, as well as hydration repulsion acting between the apposing membranes [10 -12]. The models have been used to estimate the energy of stalk formation and mesoscopic models have been used to simulate the entire fusion process [13]. However, very few measurements have been made to test these models. To date the most convincing evidence has been structural evidence that is consistent with the existence of fusion stalks [14]. As for the structural dynamics, a limited amount of experimental work has been carried out on the lamellar to inverse bicontinuous cubic phase transition [15][16][17][18][19]. The major problem to date with these dynamical studies is the lack of reproducibility in results [20,21]. FIG. 1 (color online). In these im...

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“…And on incubation at 55°C, a Qn phase slowly forms without the requirement of thermal cycling. The 31p-NMR spectrum exhibits an isotropic resonance, and the X-ray diffraction pattern is consistent with the Pn3m, or double diamond morphology (Gagne et al, 1985;Gruner et al, 1988 Based on Gruner's model, one would predict that long-chain hydrocarbon added to a Hn phase lipid system would preferentially fill the interstitial voids between the HU tubes, decrease the hydrocarbon packing energy, and thereby decrease TH. In fact this has been observed, and systems with large RO values have been induced to form the Hn phase by the addition of small amounts of such hydrocarbons as dodecane or squalene (Sjolund et al, 1987;Gruner et aI., 1988;Sjolund et al, 1989;.…”

mentioning

confidence: 72%

“…distinguishing between lamellar, inverted hexagonal, and inverted cubic phases) can only be accomplished by analysis of low angle X-ray diffraction patterns or by 31 P NMR. The Hn phase was first observed in the X-ray diffraction studies of Luzzati and coworkers (Luzzati & Reiss-Hudson, 1962;Luzzati & Reiss-Hudson, 1966;Luzzati et al, 1968;Luzzati & Tardieu, 1974) and the technique has since been employed by many others (Rand et al, 1971;Harlos & Eible, 1981;Gruner et al, 1988). The Hn phase has also be detected by 31 P-NMR (Cullis & de Kruijff, 1978;Cullis & de Kruijff, 1979); 2H-NMR (Tilcock et al, 1982); freeze-fracture electron microscopy (Deamer et al, 1970;de Kruijff et al, 1979;Van Venetie & Verkleij, 1981); fluorescence (Ellens et al, 1986a;Bentz et al, 1987;Hong et al, 1988); IR spectroscopy (Mantsch et al, 1981); ESR spectroscopy (Hardman, 1982); and differential scanning 44 calorimetry (Harlos & Eible, 1981;Seddon et al, 1983a;Epand, 1985;Ellens et al, 1986a;Ellens et al, 1986b).…”

Section: Ib3 Nonlamellar Phase Transitionsmentioning

confidence: 99%

“…Hence, isothermal nonlamellar transitions can be induced by small changes in the physicochemical conditions such as hydration, salt concentration, and pH (Seddon, 1990 (Seddon et al, 1983a;Gagne et al, 1985;Brown et al, 1986;Silvius et al, 1986;Gruner et al, 1988); deionizing the head groups (Hope & Cullis, 1980;Seddon et al, 1983b); adding Ca 2 + to charged lipid systems (Tilcock, 1986); increasing the temperature (Seddon et al, 1984;Cullis et al, 1985;Kirk & Gruner, 1985); increasing the unsaturation of the acyl-chains Gruner et al, 1985;Lewis et al, 1989); increasing the length of the acylchains (Seddon et al, 1984;Brown et al, 1986;Epand et al, 1989;Lewis et al, 1989); and dehydrating the system Seddon et al, 1983b;Cvec, 1987). Formation of the Hn phase can also be induced by addition of small amounts of long chain hydrocarbon, sllch as dodecane or squalene, to certain lipid-water systems (Kirk & Gruner, 1985;Sjolund et al, 1987;Sjolund et al, 1989).…”

Section: Ib3 Nonlamellar Phase Transitionsmentioning

confidence: 99%

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Photoinduced Fusion of Liposomes

Bennett¹,

O’Brien²

1994

J. Am. Chem. Soc.

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X-ray diffraction study of the polymorphic behavior of N-methylated dioleoylphosphatidylethanolamine

Cited by 268 publications

References 59 publications

Serum-free transfection of CHO-cells with tailor-made unilamellar vesicles

Serum-free transfection of CHO-cells with tailor-made unilamellar vesicles

Dynamics of Structural Transformations between Lamellar and Inverse Bicontinuous Cubic Lyotropic Phases

Photoinduced Fusion of Liposomes

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