Vesicles fatty acids

Vesicle self-reproduction described until now can be defined as autopoietic, since growth and eventually reproduction comes from within the structure boundary. One can also induce growth and division of fatty acid vesicles by adding fresh surfactant from the outside, for example as a micellar solution at high alkaline pH. 

The growth of fatty acid vesicles has been re-investigated by Chen and Szostack (2004) who, by the use of stopped-flow and fluorescence resonance energy transfer (FRET) techniques, provided interesting insights into the kinetics of this process. 

Blochiger, E., Blocher, M., Walde, R, and Luisi, R. L. (1998). Matrix effect in the size distribution of fatty acid vesicles. / Phys. Chem., 102,10383-90. 

Lonchin, S., Luisi, P. L., Walde, P, and Robinson, B. H. (1999). A matrix effect in mixed phospholipid/fatty acid vesicle formation. J. Phys. Chem. B, 103, 10910-16. 

Morigaki, K., Dallavalle, S., Walde, P, Colonna, S., and Luisi, P. L. (1997). Autopoietic self-reproduction of chiral fatty acid vesicles. /. Am. Chem. Soc., 119, 292-301. 

Goto, Ayako, Dynamic Aspects of Fatty Acid Vesicles pH-induced Vesicle-Micelle Transition and Dilution-induced Formation of Giant Vesicles, 6, 261. 

Fig. 5 Fatty acid vesicles can grow by addition of fatty acid molecules to the membrane and are then dispersed into smaller vesicles by passage through a porous filter. The cycle of growth and dispersion was repeated several times and presumably could go on...

Even if membranous vesicles were commonplace on the early Earth and had sufficient permeability to permit nutrient transport to occur, these structures would be virtually impermeable to larger polymeric molecules that were necessarily incorporated into molecular systems on the pathway to cellular life. The encapsulation of macromolecules in lipid vesicles has been demonstrated by hydration-dehydration cycles that simulate an evaporating lagoon [53] or by freeze-thaw cycles [54]. Molecules as large as DNA can be captured by such processes. For instance, when a dispersion of DNA and fatty acid vesicles is dried, the vesicles fuse to form a multilamellar sandwich structure with... 

An interesting mechanism for the establishment of a pH gradient in growing fatty acid vesicles was recently shown by Chen and Szostak [62], Fatty acid vesicles are usually very permeable to cations, including H+. Maintenance of a gradient thus requires a non-permeant cation, such as arginine. Incorporation of protonated (neutralised) fatty acid molecules from the external medium results in acidification of the internal milieu, by a flip-flop mechan-... 

Vesicles — (i) In cell biology, a vesicle is a small enclosed compartment, separated from the cytosol of a eukaryotic cell by a membrane of fatty acids. Vesicles are responsible for the transport of various compounds across cell membranes by endocytosis and - exocytosis. 

Chen, I.A., and Szostak, J.W., 2004, Membrane growth can generate a transmembrane pH gradient in fatty acid vesicles. Proc. Natl. Acad. Sci. U.S.A. 101 7965-7970. 

Walde, P, Wick, R., Fresta, M. et al. (1994). Autopoietic self-reproduction of fatty acid vesicles. Journal of the American Chemical Society, 116, 11649-54. 

Two important aspects of Uposome formation must be emphasized here. First, in some cases we observe the formation of ordered supramolecular structures starting from a chaotic disordered mixture of surfactants (as in the ethanol injection method . As noticed before, this increase of order is attended by a simultaneous increase of water entropy and a decrease of overall free energy (Upids and solvent). Secondly, every time a liposome forms, there is the anergence of a division, with an inside world that is different from the external environment, even if the two worlds actually interact with each other. The discrimination between inside and outside, appUcable to lipid vesicles, is the first structural pre-requisite for the living cell. It is therefore clear that lipid or fatty acid vesicles may be considered relevant experimental model of simplified cells, and their role on... 

Liposomes can be prepared according to different methods. Classical discussions" focus on the preparation of phospholipid vesicles, whereas the preparation of fatty acid vesicles has been reviewed only recently. "... 

Fatty acid vesicles, which are stable only in a rather restricted pH range, can be prepared (1) by direct dispersion of fatty acids or their salts in an aqueous phase (2) by the film method (when feasible) or (3) by acidification of an alkaline fatty acid salt micelles solution. In general, all preparation methods lead to a heterogeneous vesicle population in special conditions, however, a narrowly sized vesicle population can be obtained by an autocatalytic process. ... 

The research on biochemical reactions inside vesicles has at least three genealogical lines. The first is related to origins of life studies, where vesicles (in particular fatty acid vesicles) are taken as model of primitive cells. In this studies, vesicles are per se interesting, since their behaviour may reveal interesting pattern that might be at the basis of the... 

Type I system. Self-reproduction of vesicles. The starting point is the concept of vesicle self-reproduction. This important vesicle pattern was observed for the first time in 1994 and thoroughly studied till recently, being one of the most important reactive behaviour of fatty acid vesicles. Figure 17.8a shows the experimental model for autopoietic... 

PNPase has been entrapped inside extruded fatty acid vesicles, which are fed by externally added ADP and oleic anhydride. ADP is polymerized inside the vesicles, producing poly(A), whereas - simultaneously - oleate vesicles self-reproduce at the expenses of oleic anhydride. 

DNA template and primers were entrapped within fatty acid vesicles (e). The substrates, in form of phosphorimidazoyl nucleotides, were added externally and permeate through the vesicle membrane. DNA was therefore duplicated within unextruded fatty acid vesicles in the absence of polymerase. 

Type III system. DNA synthesis inside fatty acid vesicles. DNA is today the cellular macromolecule where the information about the proteins sequence is stored as ordered nucleobases sequence. DNA is thought to appear later than RNA in the molecular evolution, mainly with the function of storage. Its minor reactivity (due to loss of 2 -OH group) favour its chemical stability. The use of DNA polymerization in vesicle-based cell models aims to demonstrate how nucleic acids can be synthesized inside compartments, again in an origin-of-life perspective. However, due to the recent developments of DNA-based biotechnologies, it is possible that DNA-reactions in micro- or submicro-compartments... 

P. Walde, T. Namani, K. Morigaki, H. Hauser, Formation and properties of fatty acid vesicles (liposomes), in Liposome Technology, 3rd ed., Vol. I, G. Gregoriadis (Ed.), Informa Healthcare,... 

Gebricki and Hicks systematically studied vesicular fatty carboxylic acids in 1973 (17). At pH values greater than 10, the fatty acid surfactant is fully ionized and micelles are formed. As the pH is reduced into the region 7.5 to 9, partial protonation of the anion at the surface occurs and there is a transition from micellar to vesicular structures. These vesicles are much less stable than phospholipid vesicles for example, oleic acid vesicles are stable for only a few hours, while capric acid vesicles apparently can last for a few days. The difference is thought to be due to oleic acid being unsaturated and liable to autooxidation. Fatty acid vesicles made from micelles tend to be polydisperse and are multilamellar in structure. They are, however, easy to prepare and relatively inexpensive. 

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