Solubilization secondary

The most important property of micelles in aqueous or nonaqueous solvents is their ability to dissolve substances that are insoluble in the pure solvent. In aqueous systems, nonpolar substances are solubilized in the interior of the micelles, whereas polar substances are solubilized in the micellar core in nonaqueous systems. This process is called solubilization. It can be defined as the formation of a thermodynamically stable isotropic solution with reduced activity of the solubilized material (8). It is useful to further differentiate between primary and secondary solubilization. The solubilization of water in tetrachloroethylene containing a surfactant is an example of primary solubilization. Secondary solubilization can be considered as an extension of primary solubilization because it refers to the solution of a substance in the primary solubilizate. 

So far, pseudoprolines have found applications in providing solubilizing, secondary structure-disrupting building blocks for the synthesis of difficult peptide sequences and for the reversible induction of cis-amide bonds into peptide backbones (Fig. 11.15). 

In the first method a secondary acetylenic bromide is warmed in THF with an equivalent amount of copper(I) cyanide. We found that a small amount of anhydrous lithium bromide is necessary to effect solubilization of the copper cyanide. Primary acetylenic bromides, RCECCH Br, under these conditions afford mainly the acetylenic nitriles, RCsCCHjCsN (see Chapter VIII). The aqueous procedure for the allenic nitriles is more attractive, in our opinion, because only a catalytic amount of copper cyanide is required the reaction of the acetylenic bromide with the KClV.CuCN complex is faster than the reaction with KCN. Excellent yields of allenic nitriles can be obtained if the potassium cyanide is added at a moderate rate during the reaction. Excess of KCN has to be avoided, as it causes resinifi-cation of the allenic nitrile. In the case of propargyl bromide 1,1-substitution may also occur, but the propargyl cyanide immediately isomerizes under the influence of the potassium cyanide. 

When secondary or primary amines are used in place of ammonia the corresponding dialkylaminomethylenephosphonic acids (7) or alkyliminobismethyl-enephosphonic acids (8) are formed. These are used as lime soap dispersants and solubilizers of water in organic solvents [131-135]. 

The secondary solubilization of electrolytes, namely, their solubilization into water solubilized in the micelle, has been widely investigated [125-127]. 

As a result of the micellar environment, enzymes and proteins acquire novel conformational and/or dynamic properties, which has led to an interesting research perspective from both the biophysical and the biotechnological points of view [173-175], From the comparison of some properties of catalase and horseradish peroxidase solubilized in wa-ter/AOT/n-heptane microemulsions with those in an aqueous solution of AOT it was ascertained that the secondary structure of catalase significantly changes in the presence of an aqueous micellar solution of AOT, whereas in AOT/n-heptane reverse micelles it does not change. On the other hand, AOT has no effect on horseradish peroxidase in aqueous solution, whereas slight changes in the secondary structure of horseradish peroxidase in AOT/n-heptane reverse micelles occur [176],... 

Nucleophilic substitution reactions of halide anions in aprotic solvents are often accompanied by elimination reactions. For instance, reactions of secondary alkyl halides with potassium fluoride solubilized in acetonitrile with the aid of 18-crown-6 [3] give olefins as the main reaction product (Liotta and Harris, 1974). Similarly, the dicyclohexyl-18-crown-6 complex of potassium iodide acted exclusively as a base in its reaction with 2-bromo-octane in DMF (Sam and Simmons, 1974). The strongly basic character of weakly solvated fluoride has been exploited in peptide synthesis (Klausner and Chorev, 1977 Chorev and Klausner, 1976). It was shown that potassium fluoride solubilized... 

Reactions of potassium superoxide solubilized in apolar solvents with crown ethers (see Oxidation reactions, p. 356) are also frequently accompanied by elimination reactions. Thus, in DMSO solution, secondary alkyl bromides only yield olefins when treated with the K02 complex of dicyclohexyl-18-crown-6 (Johnson et al., 1978). Scully and Davis (1978) have studied the elimination of HC1 from N-chloramines with 18-crown-6-solubilized K02, KOH, and KOAc in ether solution (27). High yields of aldimines were obtained with K02,... 

As with fullerenes, carbon nanotubes are also hydrophobic and must be made soluble for suspension in aqueous media. Nanotubes are commonly functionalized to make them water soluble although they can also be non-covalently wrapped with polymers, polysaccharides, surfactants, and DNA to aid in solubilization (Casey et al., 2005 Kam et al., 2005 Sinani et al., 2005 Torti et al., 2007). Functionalization usually begins by formation of carboxylic acid groups on the exterior of the nanotubes by oxidative treatments such as sonication in acids, followed by secondary chemical reactions to attach functional molecules to the carboxyl groups. For example, polyethylene glycol has been attached to SWNT to aid in solubility (Zhao et al., 2005). DNA has also been added onto SWNT for efficient delivery into cells (Kam et al., 2005). 

Microstructures of CLs vary depending on applicable solvenf, particle sizes of primary carbon powders, ionomer cluster size, temperafure, wetting properties of carbon materials, and composition of the CL ink. These factors determine the complex interactions between Pt/carbon particles, ionomer molecules, and solvent molecules, which control the catalyst layer formation process. The choice of a dispersion medium determines whefher fhe ionomer is to be found in solubilized, colloidal, or precipitated forms. This influences fhe microsfrucfure and fhe pore size disfribution of the CL. i It is vital to understand the conditions under which the ionomer is able to penetrate into primary pores inside agglomerates. Another challenge is to characterize the structure of the ionomer phase in the secondary void spaces between agglomerates and obtain the effective proton conductivity of the layer. 

Silica is also solubilized from the igneous rocks during high-temperature reactions. This causes dissolved silica to become supersaturated, leading to the precipitation of quartz and other secondary silicates, such as albite, within the hydrothermal conduits. The formation of albite is an important reaction because it serves as a sink for Na and and a source of Ca ... 

Because ionic interactions other than hydrophobic ones are taking place, the contribution of electrostatic interactions can be estimated through studies outside the physiological pH ranges. The charge on the drug substance has an important role, along with the altered solubilization properties of the micelles (e.g., formation of secondary micelles at acidic pH see Sec. 

It is commonly agreed that enzymes are inactive in nearly anhydrous dimethyl sulfoxide (DMSO) [55] and that such inactivity might be a direct result of protein solubilization in the organic milieu, which causes deleterious changes in the proteins secondary and tertiary structures [56]. However, different authors have recently reported that some proteases, namely thermolysin (from Bacillus thermo-proteolyticus) and Proleather (from Bacillus subtilis), were still active in pure DMSO, despite the fact that proteins were indeed solubilized. The former enzyme cata-... 

Metal bioavailability is generally increased with decreasing pH. This is due to the presence of phosphoric, sulfuric and carbonic acids, which increasingly solubilize organic- and particulate-bound metals. Particulate-bound metals are considered those bound to secondary minerals, for example, clays, iron and aluminum oxides, carbonates and sulfidic and phosphoric minerals. Due to the heterogeneous nature of soils and sediments, wide fluctuations in pH can exist in a given environment. For instance, metals may be more soluble in surface layers where plant exudates, microbial activity, moisture and leaching lower pH. 

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