Structure vesicles

Fig. 2.18 Vesicle structures with silica wall (A) mesostructured silica vesicle (B) hollow capsule composed of silica particles prepared by LbL assembly.

Vesicles are permeable to apolar non-ionic solutes, and, if ionic, can bind counterions at the inner and outer surfaces. Permeability to ions depends critically upon vesicle structure. 

Semple SC, Klimuk SK, Harasym TO, et al. Efficient encapsulation of antisense oligonucleotides in lipid vesicles using ionizable aminolipids formation of novel small multilamellar vesicle structures. Biochim Biophys Acta 2001 1510 152. 

C Pidgeon. Preparation of MLV by the REV method vesicle structure and optimum solute entrapment. In G Gregoriadis, ed. Liposome Technology. 2nd ed. Vol. I. Liposome Preparation and Related Techniques. Boca Raton, PL CRC Press, 1993, pp 99-110. 

Although not strictly within the scope of this chapter, a few other delivery systems are worth mentioning by virtue of their similarity to liposomes. Bilayer vesicle structures are not limited to phospholipids. For example, cholesterol hemisuccinate vesicles have been proposed as a deliver system for poorly soluble substances (Janoffet al., 1988). Similarly, an Amphotericin B/cholesterol... 

Anholt, R Fredkin, D.R., Deerinck, T., Ellisman, M., Montal, M Lindstrom, J. (1982). Incorporation of acetylcholine receptors into liposomes. Vesicle structure and acetylcholine receptor function. J. Biol. Chem. 257, 7122-7134. 

In our model study reported in this contribution, we have chosen two double-chained C-13 alkylbenzenesulphonate surfactants (SLABS) of closely-related structure, which form micelles in aqueous solution in the absence of salt. However, when small amounts of electrolyte are added (e.g., —20mM NaCl), vesicles are spontaneously formed over a time period of seconds/minutes. These vesicle structures are then reasonably stable over a period of hours/days. The onset of vesicle formation can be readily characterised by the determination of the critical salt concentration (esc), needed to induce the formation of vesicles, from smaller aggregates or monomers. This parameter is easily determined experimentally from the increase in light scattering associated with self-assembly. It has now been determined for a number of electrolyte systems. 

Waninge, R., Nylander, T., Paulsson, M., and Bergenstahl, B. (2003). Milk membrane lipid vesicle structures studied with cryo-TEM. Colloids Surf. .31, 257-264. 

What happens if the lipid molecules of an artificial membrane themselves contain polymerizable groups and are polymerized after a vesicle membrane has been formed from the monomers Will the polymerization chain reaction run through the whole of a monolayer and will the polymer retain the vesicle structure Or will parallel ordered clusters be formed and will the vesicle be ruptured The answers to most of these questions are frustrating domains do... 

Figure 20.5. Transmission electron microscopic (TEM) images of hpid-Uke glycine peptide enclosures. Glycine tail and aspartic acid head peptides formed tube and vesicle structures. Note the growth of the tube opening (A, B, C) and the presumed vesicle division (D). If these dynamic enclosures can encapsulate other biomolecules, this may be one step closer for prebiotic molecular evolution.

Wuthier RE, Lipscomb GF (2011) Matrix vesicles structure, composition, formation and function in calcification. Front Biosci 16 2812-2902... 

In aqueous dispersion DHTDMAC spontaneously adopts the vesicle structure. This is uncommon, as vesicle formation not only requires molecular characteristics (double fatty chain molecules, no strong repulsion) but usually also a strong... 

DHTDMAC is dispersed in water as vesicles, in which fatty chains are sheltered from the solvent. Upon dilution, a modification of the vesicle structure causes the deposition of the DHTDMAC molecules onto the available solid surfaces. Coating cotton by quaternaries leads to the release in the bulk of many water molecules initially interacting with cellulose. As a result, the system entropy increases. This phenomenon is known as hydrophobic interaction. Consequently, the driver of the softener deposition is the hydrophobic ejection out of the aqueous phase and the resulting huge increase of the system entropy. 

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