Single-walled vesicle

It is above the kink concentration that a large and homogeneous single-walled vesicle is formed after dialysis. Some complicated structure other than original vesicle must be a prerequisite for such a characteristic vesicle. This unknown structure cannot be a solubilization state, since it occurs below the critical micelle concentration of each MEGA-n. We dare to speculate that some MEGA-n-saturated bilayer with open structure may be responsible for the growth. 

If the chains are sufficiently flexible, and repulsive (hydration or other) forces between aggregates sufficiently large and the chains sufficiently hydrophobic, as for double-chained surfactants like phospholipids, single-walled vesicles can occur. 

If we come back to smaller (single-walled) vesicles, we are on more familiar ground. The experimental situation is nevertheless unresolved. Some believe that vesicles are always thermodynamically unstable, the stable state being the lamellar phase. Monodisperse vesicles of the size given by simple... 

These phenomena have been explored elsewhere. Immense variability is allowed, and this depends on the particular surfactant or surfactant mix. So the question whether single-walled vesicles are thermodynamically stable or not depends on the lipid or lipid mix. Their existence does not necessarily require us to invoke non-equilibrium thermodynamics in biology. Some vesicles are stable, some are not, and this variability is exploited by nature. When the bilayer contains defects e.g. mesh structures (section 4.5)), the allowed structures are evidently more variable. 

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. 

Figure 9.13 Videomicrograph of lipid vesicle held by suction micropipet. The single-walled vesicle contains sucrose solution and the bathing solution is glucose, giving an index difference for better visualization in the interference contrast microscope. Dimensions used in calculations of area, volume and tension are shown [84].

Kaler and co-workers [22,23] have done extensive work on the phase diagram of anionic and cationic complexes to determine the vesicular phase region. They have shown that stable single-walled vesicles can form spontaneously from aqueous mixtures of simple, commercially available, single-tailed anionic and cationic surfactants (e.g., sodium dode-... 

Surfactant assemblies are generally utilized as a template to form mesoporous shell. Vesicle-like hollow sihca particles can be prepared by sol-gel reactions in the presence of surfactants. Although most of the materials reported so far have multilamellar structures, hollow mesoporous silica particles with a single-walled vesicle structure have been prepared by the reaction of TEOS in the presence of a fluorinated surfactant (lH,lH,2//,2//-perfluorodecylpyridinium chloride). With... 

Of particular interest are normal bilayers, i.e. paired monolayers embedded in water. If exposed to an excess of water, stable bilayers may form single-walled vesicles and other unilamellar structures including a bicontinuous water/water system. Single bilayers of amphiphilic molecules in water are in some respects very similar to biological model membranes if made of lipid molecules extracted from the latter. 

FIGURE 16.6 Schematic representation of a unilamellar vesicle. Note. Unilamellar means single walled vesicles can form more complex structures with one inside another. (From Fendler, J.FI., Acc. Chem. Res., 13,8,1980, Fig. 2.)... 

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... 

The growth in size of polymer vesicles formed from PS- -PAA BCPs was attribnted to fnsion and fission mechanisms by Eisenberg. Fnsion occnrs by contact and adhesion between the two vesicles. Coalescence, followed by destabilization of the central wall, leads to the formation of a single large vesicle. The reverse fission process was also demonsffated. 

Various forms of vesicles have been characterized, including single-walled (or single-lamellar) vesicles (SLVs) and multi-walled vesicles (MLVs) (see... 

Doody, M. C., Pownall, H. J., Kao, Y. J. and Smith, L. C., Mechanism and kinetics of transfer of a fluorescent fatty acid between single-walled phosphatidylcholine vesicles, Biochemistry, 19, 108-116 (1980). 

The structure of the blood capillary wall is complex and varies in different organs and tissues. It consists of a single layer of endothelial cells joined together by intercellular junctions. Each endothelial cell, on an average, is 20-40 pm long, 10-15 pm wide, and 0.1-0.5 pm thick, and contains 10,000-15,000 uniform, spherical vesicles called plasmalemmal vesicles. These vesicles range in size between 60 and 80 nm in diameter. About 70% of these vesicles open on the luminal side of the endothelial surface, and the remaining open within the cytoplasm. Plasmalemmal vesicles are believed to be involved in the pinocytic transport of substances across the endothelium. The transition time of pinocytic vesicles across the cell is... 

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