Composite vesicles

Vesicles (Fig. 7) can be considered as spherical containers with diameters of the order of 10 cm and a thickness of 50 A containing 80 000 to 100 000 surfactant molecules. The surfactants having two alkyl chains with polar groups are able to form these closed bilayers. Once formed, vesicles, unlike micelles do not easily break down into individual surfactants. Depending on their chemical composition, vesicles remain stable for days to weeks. 

Once formed, SUVs, unlike aqueous micelles, do not break down upon dilution there is no equivalent of CMC for SUVs. Additionally, depending on their chemical composition, vesicles remain stable for days to weeks. SUVs, like membranes, are osmotically active addition of electrolytes shrinks the vesicles, while placing them in solutions more dilute than their internal electrolytic concentrations causes swelling. SUVs, like membranes, are destroyed (lysed) by the addition of detergents or alcohols. 

The effects of adding DNA locally to cationic GUVs made of natural lipids have been investigated [29] and DNA induced endo- and exocytosis were observed. The phenomena depend on membrane composition, vesicle membrane tension, and DNA molecule length and conformation. The results support the idea that DNA-lipid interactions should be taken into account when considering problems of cell division and differentiation, as well as cell transfection. 

As plant cells grow, they deposit new layers of cellulose external to the plasma membrane by exocytosis. The newest regions, which are laid down successively in three layers next to the plasma membrane, are termed the secondary cell wall. Because the latter varies in its chemical composition and structure at different locations around the cell, Golgi-derived vesicles must be guided by the cytoskeleton... 

There are a variety of routes currently utilized to fabricate a wide range of hollow capsules of various compositions. Among the more traditional methods are nozzle reactor processes, emnlsion/phase-separation procednres (often combined with sol-gel processing), and sacrificial core techniques [78], Self-assembly is an elegant and attractive approach for the preparation of hollow capsules. Vesicles [79,80], dendrimers [81,82], and block hollow copolymer spheres [83,84] are all examples of self-assembled hollow containers that are promising for the encapsnlation of various materials. 

The lipid content of the membranes can be varied, allowing systematic examination of the effects of varying lipid composition on certain functions. For instance, vesicles can be made that are composed solely of phosphatidylchohne or, alternatively, of known mixtures of different phospholipids, glycohpids, and cholesterol. The fatty acid moieties of the lipids used can also be varied by employing synthetic lipids of known... 

Whittaker, VP (1987) Cholinergic synaptic vesicles from the electromotor nerve terminals of Torpedo composition and life cycle. Ann. NY Acad. Sci. 493 77-91. 

The lipid molecule is the main constituent of biological cell membranes. In aqueous solutions amphiphilic lipid molecules form self-assembled structures such as bilayer vesicles, inverse hexagonal and multi-lamellar patterns, and so on. Among these lipid assemblies, construction of the lipid bilayer on a solid substrate has long attracted much attention due to the many possibilities it presents for scientific and practical applications [4]. Use of an artificial lipid bilayer often gives insight into important aspects ofbiological cell membranes [5-7]. The wealth of functionality of this artificial structure is the result of its own chemical and physical properties, for example, two-dimensional fluidity, bio-compatibility, elasticity, and rich chemical composition. 

Although the drug delivery to the lipid bilayer membrane is just the first step for bioactivities and phopholipid vesicles are rather simple in view of the composite structure of biomembranes, the unambiguous specification of the preferential location of the drug is essential the successive processes of the action are expected to be induced via the delivery site in membranes. We expect more advances in the dynamic NMR study, so that we can get insight into the mechanism of DD in membranes. 

The great importance of minerals in prebiotic chemical reactions is undisputed. Interactions between mineral surfaces and organic molecules, and their influence on self-organisation processes, have been the subject of much study. New results from Szostak and co-workers show that the formation of vesicles is not limited to one type of mineral, but can involve various types of surfaces. Different minerals were studied in order to find out how particle size, particle shape, composition and charge can influence vesicle formation. Thus, for example, montmorillonite (Na and K10), kaolinite, talc, aluminium silicates, quartz, perlite, pyrite, hydrotalcite and Teflon particles were studied. Vesicle formation was catalysed best by aluminium solicate, followed by hydrotalcite, kaolinite and talcum (Hanczyc et al., 2007). 

Instead of the familiar sequence of morphologies, a broad multiphase window centred at relatively high concentrations (ca. 50-70% block copolymer) truncates the ordered lamellar regime. At higher epoxy concentrations wormlike micelles and eventually vesicles at the lowest compositions are observed. Worm-like micelles are found over a broad composition range (Fig. 67). This morphology is rare in block copolymer/homopolymer blends [202] but is commonly encountered in the case of surfactant solutions [203] and mixtures of block copolymers with water and other low molecular weight diluents [204,205]. 

Most transport vesicles bud off as coated vesicles, with a unique set of proteins decorating their cytosolic surface. The coat has two major known functions. First, it concentrates and selects specific membrane proteins in a discrete portion of donor organelle membrane that will serve as origin to the transport vesicle. Second, the assembly of coat proteins into curved structures delineates the area of the forming transport vesicle. The size and curvature is a function of the coat composition. Thus, vesicles with similar vesicle coat have closely similar size and shape [3]. 

COPI-coated vesicles mediate intra-Golgi transport and Golgi to ER retrograde transport. The coats of these vesicles do not show the geometric forms seen with clathrin coats and have a more complex protein composition [3]. Coat protein purification first lead to the identification of a complex composed of seven individual coat-protein subunits, known as COPI or coatomer. Some of these subunits bear a sequence similarity to clathrin adaptors. In addition, there is a small GTP-binding protein, Arfl, present on COPI-coated vesicles. 

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