Micelles hydration

Hydrated electron probe inverse micelles. Hydrated electrons (e aq) are expected to be a very good probe to test the water pool of reverse micelles. The physical properties of hydrated electrons obtained by pulse radiolysis in AOT reverse micelles were experimentally determined (Calvo-Perezet al., 1981 Pileni,... 

The texture of Cheddar cheese is considered to be more dependent on pH than on any other factor (see Lawrence and Gilles, 1982 Fox et al, 1990, for references) for the same calcium content, the texture of Cheddar varies from curdy (pH 5.3), to waxy (pH 5.3 >5.1), to mealy (pH <5.1). Suggested explanations for this pH dependence include micelle hydration, especially in the presence of NaCl, and the extent to which colloidal calcium phosphate (CCP) is solubilized. 

FIG. 1 Potential between two uncharged rough-surfaced micelles. Hydration of the surface contributes to roughness and this reduces the strength of adhesion from Vq to a lesser value Vq-... 

The majority of practical micellar systems of Tionnal micelles use water as tire main solvent. Reverse micelles use water immiscible organic solvents, altlrough tire cores of reverse micelles are usually hydrated and may contain considerable quantities of water. Polar solvents such as glycerol, etlrylene glycol, fonnamide and hydrazine are now being used instead of water to support regular micelles [10]. Critical fluids such as critical carbon dioxide are... 

Sodium octanoate (NaO) forms reversed micelles not only in hydrocarbons but also in 1-hexanol/water. The hydration of the ionogenic NaO headgroups plays an important role in this case too. For this reason Fujii et al. 64) studied the dynamic behaviour of these headgroups and the influence of hydration-water with l3C and 23Na NMR measurements. Below w0 = [H20]/[NaO] 6 the 23Na line-width... 

As mentioned above, water structure in reversed micelles deviates considerably from the structure in the bulk-phase. Therefore, the hydration shell of macromolecules entrapped in reversed micellar systems should be changed and thus also their conformation. According to the results of several authors this is indeed the case. 

The poor solubility of higher sodium alkanesulfonates cited above is reflected in the surface tension vs. concentration plots of sodium pentadecane 4-sulfonate (Fig. 26). Because below the critical micelle concentration the solubility limit is reached, a break in the a-c plot occurs. The problem of solubility properties of alkanesulfonates below the point at which the hydrated crystals or solid... 

The effects of the intramicellar confinement of polar and amphiphilic species in nanoscopic domains dispersed in an apolar solvent on their physicochemical properties (electronic structure, density, dielectric constant, phase diagram, reactivity, etc.) have received considerable attention [51,52]. hi particular, the properties of water confined in reversed micelles have been widely investigated, since it simulates water hydrating enzymes or encapsulated in biological environments [13,23,53-59]. 

FIG. 4 Onion model of spherical water-containing reversed micelles. Solvent molecules are not represented. A, surfactant alkyl chain domain B, head group plus hydration water domain C, hulk water domain. (For water-containing AOT-reversed micelles, the approximate thickness of layer A is 1.5 nm, of layer B is 0.4 nm, whereas the radius of C is given hy the equation r = 0.17R nm.)... 

For many solubilized enzymes the greatest catalytic activity and/or changes in conformation are found at R < 12, namely, when the competition for the water in the system between surfactant head groups and biopolymers is strong. This emphasizes the importance of the hydration water surrounding the biopolymer on its reactivity and conformation [13], It has been reported that enzymes incorporated in the aqueous polar core of the reversed micelles are protected against denaturation and that the distribution of some proteins, such as chymotrypsine, ribonuclease, and cytochrome c, is well described by a Poisson distribution. The protein state and reactivity were found markedly different from those observed in bulk aqueous solution [178,179],... 

Enzymes are suspended in hydrated microemulsion surrounded by a monolayer of surfactant molecules dispersed in an apolar solvent [53-60,135] [Fig. 1(b)]. Micelles ( 2 nm sphere) are formed when lyophilized or aqueous preparation of enzymes are introduced with stirring or shaking into a solution of synthetic or natural surfactant in an organic solvent. 

Micro- or nanosized polymer particles are generally called microspheres (MSs) or nanospheres (NSs), respectively, and have been used for DDS. The term nanoparticle is more general and includes polymer micelles and nanogels, which are described in Sects. 4-6. Although polymer micelles and nanogels have sufficient surface hydrated layers for dispersion or solubilizaton in aqueous media, MSs and NSs are basically spherical particles of hydrophobic polymers without enough hydrated layers. 

Lipids are mixed with the nanoparticles in an apolar solvent. The mixed film obtained is hydrated. Thereafter, the nanoparticle-containing micelles and empty micelles are separated by centrifugation. 

The classical model, as shown in Figure 1, assumes that the micelle adopts a spherical structure [2, 15-17], In aqueous solution the hydrocarbon chains or the hydrophobic part of the surfactants from the core of the micelle, while the ionic or polar groups face toward the exterior of the same, and together with a certain amount of counterions form what is known as the Stern layer. The remainder of the counterions, which are more or less associated with the micelle, make up the Gouy-Chapman layer. For the nonionic polyoxyethylene surfactants the structure is essentially the same except that the external region does not contain counterions but rather rings of hydrated polyoxyethylene chains. A micelle of... 

The rate of attack of water upon the tri-/>-anisylmethyl cation is unaffected by binding of this cation to anionic micelles of sodium dodecyl sulfate (SDS) (Bunton and Huang, 1972) and equilibrium constants for aldehyde hydration are only slightly reduced by binding to micelles (Albrizzio and Cordes, 1979). These observations are also consistent with substrate binding at a wet micellar surface rather than in the interior of the micelle. 

Figure 10.12 Micelles of sodium dodecyl sulphate (SDS) comprise as many as 80 monomer units. The micelle interior comprises the hydrocarbon chains, and is oil like. The periphery presented to the water of solution is made up of hydrated hydrophilic sulphonic acid groups...

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