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Cationic vesicles

Weissig V, Torchihn VP. Mitochondriotropic cationic vesicles a strategy towards mitochondrial gene therapy. Curr Pharm Biotechnol 2000 l(4) 325-346. [Pg.338]

Most of the characteristics invoked to explain rate accelerations and rate retardations by micelles are valid for vesicles as well. For example, the alkaline hydrolysis of A-methyl-A-nitroso-p-toluenesulfonamide is accelerated by cationic vesicles (dioctade-cyldimethylammonium chloride). This rate acceleration is the result of a higher local OH concentration which more than compensates for the decreased polarity of the vesicular pseudophase (compared to both water and micelles) resulting in a lower local second-order rate constant. Similar to effects found for micelles, the partial dehydration of OH and the lower local polarity are considered to contribute significantly to the catalysis of the Kemp elimination " by DODAB vesicles. Even the different... [Pg.29]

Fig. 133. Artist s conception of colloidal Fe304 particles incorporated in dioctadecyl-dimethylam-monium cation vesicles containing benzophenone ( ). Positions and dimensions of Fe304 particles need not be taken literally [789]... Fig. 133. Artist s conception of colloidal Fe304 particles incorporated in dioctadecyl-dimethylam-monium cation vesicles containing benzophenone ( ). Positions and dimensions of Fe304 particles need not be taken literally [789]...
Several additional studies were carried out to obtain information about the precise behavior of the various components in the model system. The interplay between the manganese porphyrin and the rhodium cofactor was found to be crucial for an efficient catalytic performance of the whole assembly and, hence, their properties were studied in detail at different pH values in vesicle bilayers composed of various types of amphiphiles, viz. cationic (DODAC), anionic (DHP), and zwitterionic (DPPC) [30]. At pH values where the reduced rhodium species is expected to be present as Rh only, the rate of the reduction of 13 by formate increased in the series DPPC < DHP < DODAC, which is in line with an expected higher concentration of formate ions at the surface of the cationic vesicles. The reduction rates of 12 incorporated in the vesicle bilayers catalyzed by 13-formate increased in the same order, because formation of the Rh-formate complex is the rate-determining step in this reduction. When the rates of epoxidation of styrene were studied at pH 7, however, the relative rates were found to be reversed DODAC DPPC < DHP. Apparently, for epoxidation to occur, an efficient supply of protons to the vesicle surface is essential, probably for the step in which the Mn -02 complex breaks down into the active epoxidizing Mn =0 species and water. Using a-pinene as the substrate in the DHP-based system, a turnover number of 360 was observed, which is comparable to the turnover numbers observed for cytochrome P450 itself. [Pg.155]

Koynova R, MacDonald RC (2005) Lipid transfer between cationic vesicles and lipid-DNA lipoplexes. Effect of serum. Biochim Biophys Acta-Biomembranes 1714 63-70... [Pg.92]

Cationic vesicles have been used to accomplish charge separation (Mon-serrat and Gratzel, 1981). The photosensitiser was a water-soluble porphyrin and electron acceptor was a modified, water-soluble viologen. The porphyrin photo-reduced the viologen which in its reduced form is lipid soluble but water insoluble. Consequently, the reduced species enters the vesicle. So effective is the charge separation that multimer formation of the reduced species in the vesicle can be observed. Another method which has been employed is to immobilise donors and acceptors on the surface of latex particles (Frank et al., 1979). [Pg.100]

The photoionization of zinc tetraphenylporphyrin and chlorophyll a in vesicles was also followed up by the ESR spectroscopy of rapidly frozen vesicles . It was found that the radical cation yield decreases in negatively charged vesicles and increases in positively charged vesicles. The cationic vesicles obviously favour electron escape from the photoproduced cation via the vesicle interface into bulk water negatively charged surfaces hinder the escape. [Pg.72]

The vesicle bilayer acts as a barrier of medium strength for water-soluble, non-ionic organic compounds. Sucrose solutions, for example, were applied as contrast agents in the light microscopy of stearic acid vesicles ". It took hours for the carbohydrate to penetrate this barrier. Efflux rates of radioactive sucrose were measured in cationic vesicles in the presence of different counterions. For this purpose, external sucrose was removed by ultrafiltration through Nucleopore polycarbonate with 0.4, 0.2 and 0.1 xm pores. The efflux rates were then determined by dialysis methods. In the case of dihexadecyldimethyl-... [Pg.75]

Cationic vesicles typically used for DNA delivery often self-aggregate or bind to plasma proteins in vivo. Wu et al. [104] attempted to improve vesicle stability using a cationic lipid with a cross-linkable acrylamide attached to the headgroup (Fig. 16). Vesicles were polymerized using thermal initiation with AAPD. Compared to monomeric vesicles, polymerized vesicles were less cytotoxic, more resistant to aggregation in serum, and comparable in transfection activity using a vector encoding firefly luciferase. [Pg.22]

Cationic vesicles, for example those formed from di-n-hexadecyldimelhylammonium bromide (DHAB) accelerate the decarboxylation by a factor of about 1000 relative to pure water. Dehydration of the carboxylate group at the binding sites is most likely the main factor behind the catalysis. Different isokinetic temperatures (obtained from linear plots of enthalpies v.y. entropies of activation) have been observed above and below the main phase transition temperature. These excellent isokinetic relationships indicate that the catalytic effects are caused by a single important interaction mechanism. ... [Pg.432]

J. E. Klijn, J. B. F. N. Engberts, The Kemp elimination in membrane mimetic reaction media. Probing catalytic properties of cationic vesicles formed from a double-tailed amphiphile and bnear long-tailed alcohols or alkyl p5ranosides, Org. Biomol. Chem., 2004, 2, 1789-1799. [Pg.451]

M. I. Angelova, N. Hristova, I. Tsoneva, DNA-induced endocytosis upon local microinjection to giant unilamellar cationic vesicles, Eur. Biophys. J., 1999, 28, 142-150. [Pg.454]

Finally, the use of vesicles in DNA-transfection is mentioned. Complexes of negatively charged DNA fragments with cationic vesicles appear, in one way or another, capable of passing cell membranes. DNA transfection is used in gene therapy to block or to initiate synthesis of desired (poly)peptides. [Pg.197]

Vesicles can be considered as minimal mimics of enzymes in terms of desolvation effects and entropy factors. If the general property of the vesicle membrane in promot-ing/accelerating chemical reactions is closely related to the one described above with micelles, it usually occurs with improved efficiency because of the higher structural organization of the bilayers. This was shown, for instance, in the study of the acceleration of the Kemp elimination in the presence of cationic micelles or cationic vesicles (Figure 17). ... [Pg.3141]

Regarding cationic micelles (using surfactants such as DTAB (dodecyltrimethylammonium bromide), or CTAB), the reaction rate was increased up to 400 times. With this system, a decrease of the solvent polarity results in an increase of the reaction rate. Chain length and counterions were also shown to influence the rate of the reaction. In cationic vesicles, higher catalytic efficiencies were... [Pg.3141]

Hydride techniques, however, can suffer from many interferences (see Section 3.3). In AAS, these interferences can not only occur as a result of influences on the hydride formation reaction, but also as a result of influences of concomitants on the thermal dissociation of the hydride. Interferences from other volatile hydride-forming elements can also occur [340], Recently, it has been found that still more elements can form volatile hydrides, as demonstrated, e.g., by Cd. Here, the hydride is normally unstable above liquid nitrogen temperatures. However, through the use of didodecyldimethylammonium bromide (DDAB) the cationic vesicles were found to stabilize the volatile species of cadmium formed after reaction with NaBH4 [341], because the detection limit using ICP-OES thus obtained. [Pg.188]

Cationic liposomes are also able to interact with negatively charged cell membranes more readily than classical liposomes. Fusion between cationic vesicles and cell surfaces might result in delivery of the DNA directly across the plasma membrane. This process bypasses the endosomal-lysosomal route which leads to degradation of anionic liposome formulations. Cationic liposomes can be formed from a variety of cationic lipids, and they usually incorporate a neutral lipid such as DOPE (dioleoylphosphatidyl-ethanolamine) into the formulation in order to faciUtate membrane fiision " . A variety of cationic lipids have been developed to interact with... [Pg.352]


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See also in sourсe #XX -- [ Pg.114 ]




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Micelles and Vesicles Based on Cationic Polypeptides

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