Interaction between sodium dodecyl sulfate

Surfactant concentration (varied after polymerization) greatly affects the viscosity of associating polymer systems. Iliopoulos et al. studied the interactions between sodium dodecyl sulfate (SDS) and hydrophobically modified polyfsodium acrylate) with 1 or 3 mole percent of octadecyl side groups [85]. A viscosity maximum occurred at a surfactant concentration close to or lower than the critical micelle concentration (CMC). Viscosity increases of up to 5 orders of magnitude were observed. Glass et al. observed similar behavior with hydrophobically modified HEC polymers. [100] The low-shear viscosity of hydrophobically modified HEC showed a maximum at the CMC of sodium oleate. HEUR thickeners showed the same type of behavior with both anionic (SDS) and nonionic surfactants. At the critical micelle concentration, the micelles can effectively cross-link the associating polymer if more than one hydrophobe from different polymer chains is incorporated into a micelle. Above the CMC, the number of micelles per polymer-bound hydrophobe increases, and the micelles can no longer effectively cross-link the polymer. As a result, viscosity diminishes. 

Iglesias, E., Montenegro, L. Kinetic investigations of the interaction between sodium dodecyl sulfate and the nonionic surfactants C,j,E . Electrical conductivity and fluorescence probe measurements. Phys. Chem. Chem. Phys. 1999, 1(20), 4865 874. 

Where this factor plays a role, the hydrophobic interaction between the hydrocarbon chains of the surfactant and the non-polar parts of protein functional groups are predominant. An example of this effect is the marked endothermic character of the interactions between the anionic CITREM and sodium caseinate at pH = 7.2 (Semenova et al., 2006), and also between sodium dodecyl sulfate (SDS) and soy protein at pH values of 7.0 and 8.2 (Nakai et al., 1980). It is important here to note that, when the character of the protein-surfactant interactions is endothermic (/.< ., involving a positive contribution from the enthalpy to the change in the overall free energy of the system), the main thermodynamic driving force is considered to be an increase in the entropy of the system due to release into bulk solution of a great number of water molecules. This entropy... 

Fusion protein pull-down assays involve the overexpression of bait and/or fusion proteins in bacteria. Often, the expressed fusion proteins are localized in occlusion bodies and not readily soluble under nondenaturing conditions. The expressed proteins can be extracted using urea, sonication, sodium dodecyl sulfate (SDS), or a combination of all the three. The net result is the denaturation of the recombinant protein and it may need to be refolded if the interaction domain is conformationally dependent. A major advantage of the pull-down assay is that high concentrations of proteins can be easily generated thus favoring protein association for a reversible equilibrium between two proteins. 

The Langmuir-Blodgett method has been used to prepare hybrid films of an anionic Ru(ll) cyanide polypyridyl complex with LDHs [170]. An LDH film was formed on mica owing to the interaction between LDHs particles and the Ru(ll) cyanide polypyridyl complex that was pre-dispersed on the surface of mica. Water-in-oU emulsions composed of octane, water and sodium dodecyl sulfate (SDS) have been used to synthesize Mg/Al LDHs with carbonate as the interlayer anion [171] by constant pH or variable pH methods. A floccule or fiber-like LDH material that possesses similar chemical composition and properties to that synthesized using a conventional variable pH method was obtained. The resulting LDH shows high surface area and a narrow distribution of mesopores. 

The best known CE buffer ingredient is sodium dodecyl sulfate (SDS) proposed by Terabe [10,11]. SDS forms micelles and the separation of neutral analytes is achieved by their partitioning between the buffer and the SDS micelles, that is, by their hydrophobicity. This is the basis of MEKC and the mobility of analytes correlates linearly well with logP values, where P is the octanol/water partition ratio. Many other buffer ingredients have been proposed. Most of them implement hydrophobic interactions between the analytes and the buffer ingredients but also ciral selectors have been used as well as various affinity probes. Interest in the ILs used as buffer additives in capillary electromigration methods is due to the fact that they could provide an alternative separation mechanism to two currently implemented mechanisms in CE which are based either on the charge to mass ratio or on the hydrophobicity of the analytes. 

Several studies have dealt with the influence of lipids on conformational equilibria in cytochrome c via hydrophobic and electrostatic interactions. The binding of sodium dodecyl sulfate monomers and micelles was reported to cause a transition of cytochrome c to a state B2 which is of potential physiological relevance. The interplay between heme only state changes and secondary structure changes was analyzed by freeze-quench and stopped-flow experiments.276 The response of the heme spin state to lipid acyl chains in cytochrome c was... 

Recent molecular dynamics simulations of water between two surfactant (sodium dodecyl sulfate) layers, reported by Faraudo and Bresme,14 revealed oscillatory behaviors for both the polarization and the electric fields near a surface and that the two fields are not proportional to each other. While the nonmonotonic behavior again invalidated the Gruen—Marcelja model for the polarization, the nonproportionality suggested that a more complex dielectric response of water might, be at the origin of the hydration force. The latter conclusion was also supported by recent molecular dynamics simulations of Far audo and Bresme, who reported interactions between surfactant surfaces with a nonmonotonic dependence on distance.15... 

Molecular recognition in micelles has been studied by Nowick et al. [84], Sodium dodecyl sulfate (SDS) micelles were used to provide a microenvironment to achieve hydrogen-bonding interactions between appropriate partners solubilized in the micelle. Nowick et al. observed that the adenine and thymine... 

Interaction between the surface-active components in surfactant mixtures and with the solubilizate can both increase and decrease solubilization into the mixed micelles. Thus, the addition of small quantities of sodium dodecyl sulfate sharply decreases the solubilization of Butobarbitone by micellar solutions of a commercial POE nonionic, Ci2H2s(0C2H4)230H. The competitive interaction of the sodium dodecyl sulfate with the oxyethylene groups on the surface of the micelles of the nonionic surfactant is believed to be the cause of this phenomenon (Treiner, 1985). On the other hand, a mixture of sodium dodecyl sulfate and sorbitan monopalmitate in aqueous solution (Span 40) solubilized dimethylaminoazobenzene more than either surfactant by itself, with maximum solubilization observed at a 9 1 molar ratio of the anionic to the nonionic (Fukuda, 1958). 

Interaction between the two surfactants has also been shown both to increase and decrease their adsorption at various interfaces. The addition of a small amount (<20 mol%) of a POE nonionic to an anionic surfactant, sodium dodecyl sulfate, increased the adsorption of the anionic onto carbon at low surfactant concentrations. As the ratio of nonionic to anionic increased this effect was diminished, and at a 1 1 molar ratio the anionic was scarcely adsorbed. It was suggested that inclusion of the POE nonionic in the adsorbed film on the carbon reduces electrical repulsion between adsorbed surfactant molecules and also between them and the negatively charged carbon surface. Increased solution concentration of POE nonionic caused displacement of the anionic from the adsorbed film by the more surface-active nonionic (Schwuger, 1977). 

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