Liposome single walled

The formation of the liposome (single-walled type) was confirmed by NMR measurements. When europium ion (Eu ) is added to a liposome solution, interacts with the choUne groups of the outward facing phospholipid and shifts the NMR signal of choline methyl groups upfield The same shift was observed for DMPC liposome/lipid-heme with the addition of Eu ". This result means the liposome formation for the hposome-embedded heme solution. The liposome formation was also supported by the sharp P-NMR spectrum (0.8 ppm), which.was caused by the spherical geometry of the phosphatidyl group. 

Artificial lipid bilayer membranes can be made [22,23] either by coating an orifice separating two compartments with a thin layer of dissolved lipid (which afterwards drains to form a bilayered structure—the so-called black film ) or by merely shaking a suspension of phospholipid in water until an emulsion of submicroscopic particles is obtained—the so-called liposome . Treatment of such an emulsion by sonication can convert it from a collection of concentric multilayers to single-walled bilayers. Bilayers may also be blown at the end of a capillary tube. Such bilayer preparations have been very heavily studied as models for cell membranes. They have the advantage that their composition can be controlled and the effect of various phospholipid components and of cholesterol on membrane properties can be examined. Such preparations focus attention on the lipid components of the membrane for investigation, without the complication of protein carriers or pore-forming molecules. Finally, the solutions at the two membrane interfaces can readily be manipulated. Many, but not all, of the studies on artificial membranes support the view developed in the previous sections of this chapter that membranes behave in terms of their permeability properties as fairly structured and by no means extremely non-polar sheets of barrier molecules. 

The electron microscopic photograph (TEM) is shown in Fig. 5. The liposome-embedded heme was able to be prepared as a single-walled, unilameller liposome with the diameter of ca. 400 A (Fig. 5 a) or a multilamellar liposome with the diameter of ca. 700 A (Fig. 5 b). The lipid-heme is embedded in the lipid bilayer of the liposome, i.e., the white roop(s) of vesicle, and one liposome vesicle contains ca. 500 or 2,000 heme... 

Fig, 5. Electron microscopic photographs for the liposome-embedded heme (DMPC liposome/ lipid-heme) a) single-wall, b) multilamellar... 

The first successful example of amino acid transport under neutral conditions, using a receptor designed in such a way as to provide charge complementarity to the zwitterionic form of the ainino acid (Eq. 2). was reported by Sunamoto and eoworkers in 1982. Upon UV irradiation, the photospiran 1 is eonverted to the purple form 2 bearing a merocyanine dye skeleton. When an aqueous suspension of single-walled liposomes containing the amino acid in the interior and I in the bilayer was... 

HPTS fluorescence has been employed in the study of proton diffusion within inverted micelles [24], in liposomes [4a], in apomyoglobin and the inter-membranal hydration layers of multi-lamellar vesicles [4b]. The simplest case for analysis involves the HPTS molecule in the center of a sphere (inverted micelle, liposome) whose walls are impermeable to protons on the timescale of the experiment. This outer wall is therefore described by an additional reflective boundary condition. Inside such a sphere, even a single proton/anion pair ultimately reaches an equilibrium situation The long-time tail approaches a plateau, rather than decaying to zero. The smaller the radius of the sphere, the higher the expected asymptotic plateau. 

Small single-walled liposomes encapsulating [ C]-CoQio were prepared according to the method described previously. Gel-... 

Fig. 3. Spontaneous release of carboxyfluorescein (200 mM) encapsulated in the interior core of liposomes with and without artificial cell wall as a function of time at 50 C and y = 0.20 M (NaCl) in 20 mM Tris-HCl (pH 8.6) top, small single-walled liposomes (30 mg, 2.4 x 10" M as lecithin in the cuvette) without polysaccharides ( —O- ) and as coated with 5 mg of OPP-50(5.6) ( ), OPP-50(1.8)...

Fig. 5. Changes in fluorescence depolarization (p) upon the enzymatic digestion of FITC(0.54)-OPP-50(1.8) as a function of time —/ the free polysaccharide —, the polysaccharide bound to small single-walled liposomes and —0 9 the polysaccharide bound to large multilamellar liposomes, respectively. For detail, see text. Vertical arrows indicate the point when pullulanase was injected after preincubation.

Table 1. Tissue Distribution of [ C]-CoQio (%) 24 hr after Intravenous Injection of Small Single-walled Liposomes into the Femoral Vein of Male Guinea Pigs...

Figure 12 exhibits that incorporation of cholesterol to dication artificial amphiphile induced a transformation of the aggregated structure from monolayer lamellae to monomolecular liposome (multilamellar liposome or single-walled vesicles). The vesicles are 100 200 nm in diameter and their membrane thickness is at least 5 20 nm. It is suspected that cholesterol molecules are mostly located in the outer half of the membrane, thus creating curvature suitable for the vesicle formation. 

The incorporation of lipid-heme in the liposome was confirmed by ultracentrifugation the supernatant did not contain both the phospholipid and the lipid-heme. The liposome solution was also examined by gel permeation chromatography monitored by the absorption at 300 and 415 nm based on the phospholipid and the heme, respectively. The curves coincided with each other, which means that the lipid-heme is included in the liposome. An electron micrograph showed a single-walled unilamellar liposome with a diameter of about 400 A [19]. 

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