Pools, aqueous

At the present time, "interest in reversed micelles is intense for several reasons. The rates of several types of reactions in apolar solvents are strongly enhanced by certain amphiphiles, and this "micellar catalysis" has been regarded as a model for enzyme activity (. Aside from such "biomimetic" features, rate enhancement by these surfactants may be important for applications in synthetic chemistry. Lastly, the aqueous "pools" solubilized within reversed micelles may be spectrally probed to provide structural information on the otherwise elusive state of water in small clusters. 

Reversed micelles 3D 20-40 A diameter Dissolution of surfactant in a nonpolar solvent in the presence of a small amount of water Concentration-, surfactant-, solubili-zate-, and solvent-dependent dynamic equilibria Particles could be generated and derivatized in aqueous pools and, subsequently, separated from surfactants 55, 101... 

Aqueous pools of reversed micelles have been fruitfully employed for the in situ generation of semiconductor particles. The first publication in this area described the formation of CdS in sodium bis(2-ethylhexyl)sulfosuccinate (AOT) aggregates in isooctane [611]. The preparation involved the addition of aqueous CdCl or Cd(N03)2 to isooctane solutions of AOT. Exposure to controlled ammeters of the CdS particles formed. Irradiation of degassed, AOT-reversed-micelle-entrapped, platinized CdS by visible light (450-W Xenon lamp X > 350 nm) in the presence of thiophenol (PhSH) resulted in sustained hydrogen formation. Sacrificial electron transfer occurred from thiophenol to positive holes in the colloidal CdS and, consequently, diminished undesirable electron-hole recombinations (Fig. 101) [611]. 

It has been reported336 that in systems of the kind shown in Figure 15, with a sensitizer and an electron donor in the bulk phase separated from methylviologen in the inner aqueous pools, electron transfer can occur directly across the membrane. Further studies, however, showed that MV2+ was escaping photochemically (perhaps because of localized heating) to the bulk phase where it was reduced.337... 

Extensive studies in reverse micelles revealed a similar water distribution [127-130], which is consistent with the distinct water model proposed by Finer [150]. For example, when the molar ratio (wo) of water to the surfactant is 6.8 in lecithin reverse micelles with a corresponding diameter of 37 A, three solvation time scales of 0.57 (13%), 14 (25%), and 320 ps (62%) were observed using coumarin 343 as the molecular probe. At w0 = 4.8 with a 30-A water core diameter, only a single solvation dynamic was observed at 217 ps, which indicates that all water molecules are well ordered inside the aqueous pool. The lecithin in these reverse micelles have charged headgroups, which have much stronger interactions with water than the neutral headgroups of monoolein in the... 

The fusion process was observed by electron microscopy and remained at a low level, not resulting in an intermixing of the aqueous pools of the liposomes in significant proportion. It seems that fusion resulted from the collapse of mixed triaminopyridine/barbituric acid liposomes with neighbouring liposomes. 

On the other hand, liposomes permit us to mimic cells much better than all other artificial compartments. With their inner aqueous pools that form a perfect boundary with the external medium, liposomes resemble cells or cell organelles much more closely than other artificial compartments. 

This chapter focuses on studies that describe enzymatic reactions occurring in the aqueous pools of conventional liposomes or giant vesicles among all the reactions that have been performed within such aggregates, this chapter summarizes enzymatic reactions that are nucleic acid dependent (various polymerase reactions and protein synthesis) and are, therefore, also relevant to the origin of life. 

Of course, other strategies are conceivable and have also been suggested in the literature. Here, we could mention methods that derive from the classical reverse phase evaporation or formation of liposomes by dialysis. " Another conceivable and proposed (but as yet never applied for such complex enzymatic reactions) approach would be one involving two preparations of liposomes containing, for example, enzyme in the first preparation and nucleic acids/substrate molecules in the second preparation. Then, a fusion process would have to be induced that would create one new compartment containing all the required molecules in the same aqueous pool. 

Some years ago, we began in our laboratory to inject substances into these GVs formed by electroformation, while still in contact with the electrode. These results showed that these GVs permit the injection of hydrophilic substances into the aqueous pool of a selected GV. In this way, substances such as proteins or nucleic acids were loaded into a micropipet, the micropipet was positioned close to the selected GV, then the GV was punctured, and the substances were injected by blasts of air. Depending on the quality of the micropipet and the chemical property of the loaded substance, different pressures were necessary to push the substance into the GV. Once the substance... 

In this brief review we will describe some important encapsulation processes by vesicular aggregates. Encapsulation will be broadly interpreted. Apart from solubilization in the aqueous pool inside the vesicle, the term will also encompass binding of solubilizates to all binding sites available in the vesicular system. We will not discuss bilayer vesicles formed from amphiphiles further functionalized by receptor molecules, such as amphiphilic cyclodextrins. ... 

Liposomes formed from natural phospholipids are either zwitterionic or carry a net negative charge. Using them as gene carriers, nucleic-acid binding must now rely mainly on entrapment into the aqueous pool of the liposomes. 

As with aqueous micelles, catalytic activity in reversed micelles is due to substrate solubilization. The concentrations in a reverse micellar system can be based on either the total reaction volume or the micellar aqueous pool. The former is obviously simpler though somewhat less realistic. 

The elongation of the droplets may also effect a shift to the right of the monomer-droplet equilibrium of the surfactant [41]. Namely, the deviation from sphericity of a droplet with an aqueous pool of constant volume results in an increase of its water/oil interfacial area. The instability that results may be reduced by the entrance of surfactant monomers from the bulk phase, leading to an increase in surfactant aggregation number of the microemulsion particle in the presence of the field. 

Concomitant preparation of the Descemet s membrane (central to the Schwalbe s line) combined with a deep sclerectomy (actually a deep sclerocornectomy) leads to the formation of a small aqueous pool in the scleral sheath which empties... 

Finally, I wish to mention a study of hyperpolarized Xe in living biological cells. The signal corresponding to xenon in the aqueous pool inside the cells was identified and its relaxation time was found to be sufficiently long to open promising perspectives. 

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