Vesicle giant

The so-called giant vesicles owe their name to the fact that they can reach up to 100 (xm in diameter. Such over-dimensioned structures can be often observed as byproducts in the normal preparation of vesicles, but they can be obtained by specific methods, for example by that dubbed electroformation (Angelova and Dimitrov, 1988). 

By working with giant vesicles, the chemist acquires the working habits of a cell biologist, suffering, however, from being obliged to work with only one 

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While most vesicles are formed from double-tail amphiphiles such as lipids, they can also be made from some single chain fatty acids [73], surfactant-cosurfactant mixtures [71], and bola (two-headed) amphiphiles [74]. In addition to the more common spherical shells, tubular vesicles have been observed in DMPC-alcohol mixtures [70]. Polymerizable lipids allow photo- or chemical polymerization that can sometimes stabilize the vesicle [65] however, the structural change in the bilayer on polymerization can cause giant vesicles to bud into smaller shells [76]. Multivesicular liposomes are collections of hundreds of bilayer enclosed water-filled compartments that are suitable for localized drug delivery [77]. The structures of these water-in-water vesicles resemble those of foams (see Section XIV-7) with the polyhedral structure persisting down to molecular dimensions as shown in Fig. XV-11. 

Poly(A) synthesis also occurred in the second system, but the product remained within the vesicles. Walde also determined the increase of the vesicle concentration, which corresponds to that expected for an autocatalytic process. In this experiment, the enzyme PNPase is first captured by the vesicle envelope, and in the second step, ADP and oleic anhydride are added the anhydride is hydrolysed to the acid. ADP passes through the vesicle double layer and is polymerized in the interior of the vesicle by PNPase to give poly(A). Hydrolysis of the anhydride causes a constant additional delivery of vesicle-forming material, so that the amount of vesicle present increases during the poly(A) synthesis. These experiments demonstrated a model for a minimal cell. Autocatalytically synthesised giant vesicles could be prepared under similar conditions and observed under a microscope (Wik et al., 1995). 

Antimisiaris, S.C., Jayasekera, P., and Gregoriadis, C. (1993) Liposomes are vaccine carriers Incorporation of soluble and particulate antigens in giant vesicles./. Immunol. Meth. 166, 271-280. 

Again, using a lateral dimension of a site, d = 0.2 nm, and the lattice site area as = 3d2, means that y 1 corresponds with about 33mNm 1 lateral tension. In other words, one needs to apply a lateral tension of order 40mNm 1 to double the membrane area. This prediction seems to be a factor of about six lower than estimates that were recently reported by Evans and co-workers [107], These authors use micropipettes to pressurise giant vesicles and obtain values of the order Ka = 8y/Sinn = 230mNm. There are also some data on the compressibility modulus, as found by MD simulations on primitive surfactants [62] Ka = 400 mN m 1. In a molecular detailed simulation study on DPPC lipids, Feller and Pastor [40] report a KA value of about 140 mNm 1. 

Koster G, VanDuijn M, Hofs B, Dogterom M (2003) Membrane tube formation from giant vesicles by dynamic association of motor proteins. Proc. Natl. Acad. Sci. USA 100 15583-15588. 

Dhan F, Galow TH, Gray M, Clavier G, Rotello VM. Giant vesicle formation through self-assemhly of complementary random copolymers. J Am Chem Soc 2000 122 5895-5896. 

The obtained suspension is generally a mixture of liposomes of all sizes (typically from 20 to 2000 nm), and different species are generally observed, as shown in Figure 9.21. We will see later on that giant vesicles, spanning over a 100 p,m diameter, can also be formed. 

Giant vesicles have been the subject of several international meetings and specialized literature (Luisi and Walde, 2000 Fischer et al., 2000). There are several reasons for this interest. One is that, because of their size, they can be observed by normal optical microscopy, without using the much more expensive and indirect electron microscopy. Figure 10.7 shows, as an example, the transformations brought about by the addition of a water-insoluble precursor (oleic anhydride) to oleic acid giant vesicles (Wick et al., 1995). 

A second reason for the interest in giant vesicles is that by special micromanipulation (similar to that used in cell biology) it is possible directly and quantitatively to inject chemicals inside the compartment. An example of the effect of an enzymatic reaction inside giant vesicles is given in the Figure 10.8. 

Figure 10.7 Direct observation of transformations in giant vesicles. This results from the addition of oleic anhydride to giant oleate vesicles. (Adapted from Wick...

T7RNA polymerase within cell-sized giant vesicles formed by natural swelling of phospholipid films... 

DNA template and the enzyme T7RNA polymerase microinjected into a selected giant vesicle nucleotide triphosphates added from the external medium... 

The permeability of giant vesicles increased in an alternating electric field m-RNA synthesis occurred. 

Table 11.5 reports also the work by Fischer et al. (2002) on m-RNA synthesis inside giant vesicles utihzing a DNA template and T7 RNA polymerase and the transcription of DNA hy Tsumoto et al. (2002). 

Eischer, A., Franco, A., and Oberholzer, T. (2002). Giant vesicles as microreactors for enzymatic mRNA synthesis. Chem. Bio. Chem., 3 (5), 409-17. 

Fischer, A., Oberholzer, T., and Luisi, P. L. (2000). Giant vesicles as models to study the interactions between membranes and proteins. Biochim. Biophys. Acta, 1467,... 

Takakura, K., Toyota, T, and Sugawara, T. (2003). A novel system of self-reproducing giant vesicles. J. Am. Chem. Soc., 125, 8134-8140. See also Takakura, K Toyota, T, Yamada, K., et al. (2002). Morphological change of giant vesicles triggered by dehydrocondensation reaction. ChemLett., 31,404-5. 

Walde, P. (2000). Enzymatic reactions in giant vesicles. In Giant Vesicles, Perspectives in Supramolecular Chemistry, eds. P. L. Luisi and P. Walde. John Wiley Sons Ltd., pp. 297-311. 

Akashi, Ken-ichirou, Observation of a Variety of Giant Vesicles under an Optical Microscope, 6, 45 see also Miyata, Hidetake, 6, 319. 

Dimova, Rumiana, Motion of Particles Attached to Giant Vesicles Falling Ball Viscosimetry and Elasticity Measurements on Lipid Membranes, 6, 221. 

Fischer, Aline, Formation of Giant Vesicles from Different Kinds of Lipids Using the Electrothermal Method, 6, 37 see also Oberholzer, Thomas, 6, 285. 

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

Changes in the Morphology of Giant Vesicles Under Various Physicochemical Stresses, 6, 341. 

Lasic, Danilo, D. Giant Vesicles A Historical Introduction, 6, 11. 

Luisi, Pier Luigi, Why Giant Vesicles , 6, 3 see also Fischer, Aline, 6, 37. 

M616ard, Philippe, Electromechanical Properties of Model Membranes and Giant Vesicle Deformations, 6, 185 see also Bivas, Isak, 6, 207. 

Miyata, Hidetake, see Akashi, Kenichirou, 6, 45 see also Cell deformation Mechanisms Studied with Actin-containing Giant Vesicles, a Cell-mimicking System.,... 

Petrov, Peter G., Light-Induced Shape Transitions of Giant Vesicles, 6, 335. 

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