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Lipid bilayers phosphatidylcholine bilayer

Phosphatidylcholine is an important component of cell membranes but cell mem branes are more than simply lipid bilayers Although their composition varies with their source a typical membrane contains about equal amounts of lipid and protein and the amount of cholesterol m the lipid fraction can approximate that of phosphatidylcholine The lipid fraction is responsible for the structure of the membrane Phosphatidyl choline provides the bilayer that is the barrier between what is inside the cell and what IS outside Cholesterol intermingles with the phosphatidylcholine to confer an extra measure of rigidity to the membrane... [Pg.1078]

Liposomes are members of a family of vesicular structures which can vary widely in their physicochemical properties. Basically, a liposome is built of one or more lipid bilayers surrounding an aqueous core. The backbone of the bilayer consists of phospholipids the major phospholipid is usually phosphatidylcholine (PC), a neutral lipid. Size, number of bilayers, bilayer charge, and bilayer rigidity are critical parameters controlling the fate of liposomes in vitro and in vivo. Dependent on the preparation procedure unilamellar or multilamellar vesicles can be produced. The diameter of these vesicles can range from 25 nm up to 50 ym—a 2000-fold size difference. [Pg.261]

In studies with specific phospholipases the asymmetry in the composition of the lipid bilayer was also suggested [102,162]. The requirement of specific phospholipids, which are essential for enzyme activity, however, has not been established. For example, Saccomani et al. [102] demonstrated that readdition of various phospholipids, after phospholipase A2 treatment, results in a restoration of the K -ATPase activity. On the other hand, Nandi et al. [161] observed a restoration of the K -ATPase activity with addition of phosphatidylcholine and not with phosphatidyl-... [Pg.44]

Lessard, J. G. Fragata, M., Micropolarities of lipid bilayers and micelles. 3. Effect of monovalent ions on the dielectric constant of the water-membrane interface of unilamellar phosphatidylcholine vesicles, J. Phys. Chem. 90, 811-817 (1986). [Pg.275]

Figure 1 (Plate 1). A molecular view of a small section of a flat lipid bilayer generated by molecular dynamics simulations. The bilayers are composed of l-stearoyl-2-docosa-hexaenoyl-5M-g]ycero-3-phosphatidylcholine lipids, i.e. the sn 1 chain is 18 C atoms long and the sn2 chain has 22 carbons, including six cis double bonds. The hydrophobic core is in the centre of the picture, and the hydrated head-group regions are both on top and bottom of the view graph. The head group is zwitterionic and no salt has been added. From [102], Reproduced by permission of the American Physical Society. Copyright (2003)... Figure 1 (Plate 1). A molecular view of a small section of a flat lipid bilayer generated by molecular dynamics simulations. The bilayers are composed of l-stearoyl-2-docosa-hexaenoyl-5M-g]ycero-3-phosphatidylcholine lipids, i.e. the sn 1 chain is 18 C atoms long and the sn2 chain has 22 carbons, including six cis double bonds. The hydrophobic core is in the centre of the picture, and the hydrated head-group regions are both on top and bottom of the view graph. The head group is zwitterionic and no salt has been added. From [102], Reproduced by permission of the American Physical Society. Copyright (2003)...
As very accurate input data are needed for a successful MD run on lipid systems, it is not surprising that most of the simulations done are for a very limited number of systems for which these are available. Phosphatidylcholine (PC) bilayers have been and still are popular [31,33-41], but, nowadays, other types of lipid bilayers are under investigation as well [42-46]. MD studies on lipid mixtures, as well as a lipid bilayer including some protein-like object, give all kinds of additional problems that we will touch upon below. [Pg.35]

Hyvonen, M. T., Rantala, T. T. and Ala-Korpela, M. (1997). Structure and dynamic properties of diunsaturated l-palmitoyl-2-linoleoyl-,sM-glycero-3-phosphatidylcholine lipid bilayer from molecular dynamics simulation, Biophys. J., 73, 2907-2923. [Pg.104]

The biological membrane is composed of lipid bilayers and proteins, and it is generally agreed that the lipid bilayer (layer width, 50-70 A) is the basic structural unit (e.g. Brockerhoff, 1977). The most abundant bilayer-forming lipids are the phosphatidylcholines (lecithins). These compounds have a... [Pg.438]

Plots of t0/t for varying [Q]T are first otained for different concentrations of lipid. Then, form the slope and intercept of a plot of k pp against am, the value of the partition coefficient is obtained. This method has been applied to the partitioning of lindane into lipid bilayers.(102 103) An example is shown in Figure 5.4 for the quenching of DPH by 5-DOXYL-decane in dimyristoyl-phosphatidylcholine vesicles(104) the increase in the partition coefficient as the... [Pg.254]

Once synthesized several factors influence the particular leaflet of the membrane lipid bilayer where the lipids reside. One is static interactions with intrinsic and extrinsic membrane proteins which, by virtue of their mechanism of biosynthesis, are also asymmetric with respect to the membrane. The interaction of the cytoplasmic protein, spectrin with the erythrocye membrane has been the subject of a number of studies. Coupling of spectrin to the transmembrane proteins, band 3 and glycophorin 3 via ankyrin and protein 4.1, respectively, has been well documented (van Doit et al, 1998). Interaction of spectrin with membrane lipids is still somewhat conjectural but recent studies have characterized such interactions more precisely. O Toole et al. (2000) have used a fluorescine derivative of phosphatidylethanolamine to investigate the binding affinity of specttin to lipid bilayers comprised of phosphatidylcholine or a binary mixture of phosphatidylcholine and phosphatidylserine. They concluded on the basis... [Pg.45]

Self-diffusion measurements of phosphatidylcholines in lipid bilayers 190... [Pg.163]

In order to provide quantitative information on the elfeets of pressure on eross-peak intensities, we earned out 2D-NOESY experiments on pure POPC (l-palmitoyl-2-oleoyl-x -glyeero-3-phosphatidylcholine (Ci6 o, Cig c )) and DMPC (l,2-dimyristoyl-OT-glyeero-3-phosphatidylcholine (di-Ci4 o)) lipid bilayers.As an example, we present data on POPC, a phospholipid which is also a very important eomponent of animal cell membranes. It has an... [Pg.173]

Our first issue with respect to the lipid bilayer is its composition. This varies from membrane to membrane but generally includes several glycerophospholipids— phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine—as well as... [Pg.258]

The peptide subunit was easily incorporated into lipid bilayers of liposome, as confirmed by absorption and fluorescence spectroscopy. Formation of H-bonded transmembrane channel structure was confirmed by FT IR measurement, which suggests the formation of a tight H-bond network in phosphatidylcholine liposomes. Liposomes were first prepared to make the inside pH 6.5 and the outside pH 5.5. Then the addition of the peptide to such liposomal suspensions caused a rapid collapse of the pH gradient. The proton transport activity was comparable to that of antibiotics gramicidin A and amphotericin B. [Pg.177]

Many phospholipids, including (I) through (IV) above, form lipid bilayers when dispersed in water. These bilayers may take on various shapes, depending on their treatment. When strongly sonicated in aqueous solutions, phosphatidylcholines such as (II) form quite stable singlecompartment vesicles, with outer diameters of the order of 200 to 350 A. [Pg.252]

Figure 8-4 Bimolecular lipid layers and membranes. (Top) A molecule of phosphatidylcholine. (Center) Lipid bilayer structure. (Bottom) Bilayer structure as seen by the electron microscope with osmium tetroxide staining. Figure 8-4 Bimolecular lipid layers and membranes. (Top) A molecule of phosphatidylcholine. (Center) Lipid bilayer structure. (Bottom) Bilayer structure as seen by the electron microscope with osmium tetroxide staining.
Liquid crystals, liposomes, and artificial membranes. Phospholipids dissolve in water to form true solutions only at very low concentrations ( 10-10 M for distearoyl phosphatidylcholine). At higher concentrations they exist in liquid crystalline phases in which the molecules are partially oriented. Phosphatidylcholines (lecithins) exist almost exclusively in a lamellar (smectic) phase in which the molecules form bilayers. In a warm phosphatidylcholine-water mixture containing at least 30% water by weight the phospholipid forms multilamellar vesicles, one lipid bilayer surrounding another in an "onion skin" structure. When such vesicles are subjected to ultrasonic vibration they break up, forming some very small vesicles of diameter down to 25 nm which are surrounded by a single bilayer. These unilamellar vesicles are often used for study of the properties of bilayers. Vesicles of both types are often called liposomes.75-77... [Pg.392]

Lewis RNAH, Winter I, Kriechbaum M et al (2001) Studies of the structure and organization of cationic lipid bilayer membranes calorimetric, spectroscopic, and x-ray diffraction studies of linear saturated P-O-ethyl phosphatidylcholines. Biophys J 80 1329-1342... [Pg.88]


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Bilayer, lipidic

Lipid bilayer

Lipid bilayers

Lipids phosphatidylcholine

Phosphatidylcholin

Phosphatidylcholine

Phosphatidylcholine bilayer

Phosphatidylcholine bilayers

Phosphatidylcholines

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