X-ray Diffraction Studies on the Effect of Additives on the Phase Behaviour of Lipids

Rapp, Gert; Funari, Sérgio S.; Richter, Frank M.; Woo, D.

doi:10.1007/978-3-662-04496-4_8

Cited by 3 publications

(3 citation statements)

References 55 publications

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“…For example, the addition of nonionic surfactants into phosphatidylcholine bilayers modifies the structure of the lipid self-assembly when compared with the phospholipid alone (32). Thus, in the presence of C 12 EO 4 (tetraethyleneglycolmono-n-dodecylether), dipalmitoyl phosphatidylcholine (a lamellar-prone lipid) formed a pseudobinary mixture in excess of water (33).…”

Section: Depe Systemsmentioning

confidence: 99%

Effects of oleic acid and its congeners, elaidic and stearic acids, on the structural properties of phosphatidylethanolamine membranes

Funari

Barceló

Escribá

2003

Journal of Lipid Research

140

132

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Section: Depe Systemsmentioning

confidence: 99%

Effects of oleic acid and its congeners, elaidic and stearic acids, on the structural properties of phosphatidylethanolamine membranes

Funari

Barceló

Escribá

2003

Journal of Lipid Research

140

132

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“…Further analysis determined a high solubility of CO 2 in model cell-membrane phospholipids (based on a binary CO 2 −phospholipid system), suggesting that (iii) the enhanced permeability of the membrane in the presence of CO 2 contributed to the inactivation of the cells. While cell membranes are frequently described as being in a fluid state, probing the fluidity of gel and fluid bilayers is of interest in this study as they coexist in biological membranes during many cellular processes, such as cell division . In addition, microbial sterilization and liposome formation can occur over a wide range of temperatures, which may span the gel or fluid phases.…”

Section: Introductionmentioning

confidence: 99%

Liposome Fluidization and Melting Point Depression by Pressurized CO₂ Determined by Fluorescence Anisotropy

et al. 2004

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The influence of CO2 on the bilayer fluidity of liposomes, which are representative of model cellular membranes, was examined for the first time at the elevated pressures (up to 13.9 MPa) associated with CO2-based processing of liposomes and microbial sterilization. Fluidization and melting point depression of aqueous dipalmitoylphosphatidylcholine (DPPC) liposomes by pressurized CO2 (present as an excess phase) were studied by steady-state fluorescence anisotropy using the membrane probe 1,6-diphenyl-1,3,5-hexatriene (DPH). Isothermal experiments revealed reversible, pressure-dependent fluidization of DPPC bilayers at temperatures corresponding to near-gel (295 K) and fluid (333 K) phases at atmospheric pressure, where the gel-to-fluid phase transition (Tm) occurs at approximately 315 K. Isobaric measurements (PCO2 =1.8, 7.0, and 13.9 MPa) of DPH anisotropy demonstrate substantial melting point depression (DeltaTm = -4.8 to -18.5 K) and a large broadening of the gel-fluid phase transition region, which were interpreted using conventional theories of melting point depression. Liposome fluidity is influenced by CO2 accumulation in the hydrocarbon core and polar headgroup region, as well as the formation of carbonic acid and/or the presence of buffering species under elevated CO2 pressure.

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“…Although surface X-ray scattering on supported lipid−water systems is a relatively young field, a great variety of techniques has been employed in aligning synthetic and biological membrane stacks. − Roughly speaking, these may be divided into three categories: first, aligned multilayers hydrated from vapor with relative humidities (RH) below 100% (e.g., refs and ); second, lipid samples under 100% RH condition; third, fully hydrated specimens at an excess of water. , Under low-humidity conditions the samples are very stable and thus easy to handle. Therefore most of the structural and dynamical studies have been carried out at RH below 100%, e.g., investigations on lipid/protein interaction (for a review see ref ) or time-resolved diffraction studies on the effect of additives …”

Section: Introductionmentioning

confidence: 99%

In Situ Sensing of Salinity in Oriented Lipid Multilayers by Surface X-ray Scattering

et al. 2004

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The influence of LiCl solutions on liposomal and surface-supported phosphatidylcholine/water systems (dipalmitoylphosphatidylcholine (DPPC) and 1-palmitoyl-2-oleoylphosphatidylcholine (POPC), respectively) has been studied by small-angle X-ray techniques. In liposomal dispersions of DPPC, an osmotically stressed liquid-crystalline phase, denoted as Lalpha osm, forms readily after rapid mixing with salt solutions. The transition from Lalpha -->Lalpha osm proceeds in two steps. The first step takes place within seconds and is due to water diffusion from the liposome into the bulk solution. The second, slower process (minutes) can be attributed to the relaxation of initially deformed intermediate liposomes into spherical ones. In experiments with aligned lipid bilayers supported on silicon wafers, it was possible to reproducibly exchange different concentrations of LiCl solutions on a single sample and to determine the lattice changes by time-resolved X-ray scattering at grazing incidence. Independently of the deposition technique (spray- or spin-coating, respectively), none of the investigated POPC samples displayed an osmotically stressed liquid-crystalline phase. While liposomes can be considered nearly defect-free, supported bilayer stacks show a high abundance of defects, such as oily streaks typical of the Lalpha phase. Thus, the alkali ions are free to diffuse into the interbilayer water regions and to cause a slight increase of the bilayer separation (about 1 Angstroms). It is concluded that low to medium concentrations of Li+ ions partially screen the attractive van der Waals force between adjacent membrane layers. However, upon annealing the defect regions or regions of high curvature in the oriented lipid matrix, e.g. by low amounts of oleyl alcohol (OA), the system is able to sense osmotic stress upon addition of a salt solution.

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X-ray Diffraction Studies on the Effect of Additives on the Phase Behaviour of Lipids

Cited by 3 publications

References 55 publications

Effects of oleic acid and its congeners, elaidic and stearic acids, on the structural properties of phosphatidylethanolamine membranes

Effects of oleic acid and its congeners, elaidic and stearic acids, on the structural properties of phosphatidylethanolamine membranes

Liposome Fluidization and Melting Point Depression by Pressurized CO₂ Determined by Fluorescence Anisotropy

In Situ Sensing of Salinity in Oriented Lipid Multilayers by Surface X-ray Scattering

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X-ray Diffraction Studies on the Effect of Additives on the Phase Behaviour of Lipids

Cited by 3 publications

References 55 publications

Effects of oleic acid and its congeners, elaidic and stearic acids, on the structural properties of phosphatidylethanolamine membranes

Effects of oleic acid and its congeners, elaidic and stearic acids, on the structural properties of phosphatidylethanolamine membranes

Liposome Fluidization and Melting Point Depression by Pressurized CO2 Determined by Fluorescence Anisotropy

In Situ Sensing of Salinity in Oriented Lipid Multilayers by Surface X-ray Scattering

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Liposome Fluidization and Melting Point Depression by Pressurized CO₂ Determined by Fluorescence Anisotropy