Tl+/Na+Competitive Binding at the Surface of Dodecylsulfate Micelles in Water–Urea Mixtures

Abuín, E.; Lissi, E. A.; Borsarelli, Claudio D.

doi:10.1006/jcis.1996.0662

Cited by 10 publications

(13 citation statements)

References 8 publications

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“…Additional details will be presented elsewhere. As previously shown, the additon of urea into the subphase of DODA monolayers leads to a large increase in A o as well as a loss of ionic selectivity as observed with cationic micelles . Table contains a list of the A o values for the amphiphiles previously mentioned.…”

Section: Resultsmentioning

confidence: 93%

“…Urea increases the cmc of amphiphiles, and the effects are generally greater on cationic than on anionic amphiphiles, but they are also observed with nonionic amphiphiles, e.g., C 12 E 6 8 and zwitterionic amphiphiles 7b. Added urea increases the dissociation degree (α) of ionic surfactants, and this increase is accompanied by a loss of counterion selectivity by the micellar interface in cationic, cetyltrimethylammonium halide (CTAX, X = Cl, Br), anionic, methyl dodecyl sulfate (MeDS, Me = Tl, Na), zwitterionic hexadecyldimethylammoniumpropane sulfonate (HPS) micelles, and also cationic vesicles. , Added urea, as expected, also decreases micellar aggregation numbers . The effect of added urea on ionic micelles is consistent with urea-enhanced stabilization of free ions (hindering of ion pair formation).…”

Section: Resultsmentioning

confidence: 99%

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Effect of Urea on Biomimetic Systems: Neither Water 3-D Structure Rupture nor Direct Mechanism, Simply a More “Polar Water”

et al. 2001

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Analysis of a variety of properties of supramolecular aggregates in aqueous urea supports an explanation for the urea effect that differs from traditional explanations based on the direct mechanism of urea−water solvation or the indirect mechanism via rupture of the three-dimensional (3-D) structure of water. The urea-induced effects investigated are increases in amphiphile critical micelle concentrations, ionization degrees (α), and aggregation numbers; decreases in percolation thresholds of reversed micelles; expansion of minimum areas of monolayers; increases in the radii of gyration of polyelectrolytes; changes in morphologies of sodium bis-2-ethylhexylsulfosuccinate thin films on glass substrates; and direct evidence for urea-induced reduction in ion pairing. All of these effects are attributed to an urea-induced enhancement of the hydrophilic properties of water that results in more strongly solvated polar groups and ions and a reduction in ion pair formation. The implications of this analysis for urea effects on protein 3-D structure are briefly highlighted.

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Section: Resultsmentioning

confidence: 93%

Section: Resultsmentioning

confidence: 99%

Effect of Urea on Biomimetic Systems: Neither Water 3-D Structure Rupture nor Direct Mechanism, Simply a More “Polar Water”

et al. 2001

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“…Fluorescence dyes have attracted much attention owing to their broad use in paint, inks, textiles, and optical devices as a result of their vivid color, broad spectra, strong fluorescence intensity, and high quantum yield. − In addition, they have rather specialized applications in biodiagnostic assays. An appropriate fluorescent probe for micro-heterogeneous media (supramolecular receptors, − micelles, − vesicles, microemulsions, , proteins, − etc.) shows remarkable changes in its one or more fluorescence parameters such as transition maximum, intensity, decay parameters, and anisotropy as it gets into the organized media.…”

Section: Introductionmentioning

confidence: 99%

Supramolecular Recognition Induces Nonsynchronous Change of Dye Fluorescence Properties

et al. 2016

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Fluorescence behavior of 8-anilino-1-naphthalenesulfonate (ANS) reflects a blue-shift and fluorescence enhancement on decreasing solvent polarity, with both properties affected in a synchronous way in solvent mixtures where ANS senses a homogeneous solvation shell. ANS complexation by cyclodextrins or bovine serum albumin (BSA) results in a nonhomogeneous solvation shell that is reflected by nonsynchronous variation of fluorescence properties. Steady-state fluorescence and saturation transfer difference NMR experiments allow us to conclude the formation of 1:1 and 2:1 host/guest complexes through the aniline or naphthalene moieties of ANS with cyclodextrins. This nonhomogeneous solvation shell has been ignored in studies using ANS to sense the microenvironment of proteins, micelles, bilayers, and other organized systems. ANS interaction with BSA reflects the existence of a large number of binding pockets in the surface of the protein that can be classified into two well-differentiated categories.

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“…Just as the delicate balance between hydrophobic and hydrophilic interactions in a solvent plays the most crucial role in case of proteins, so is the case with amphiphilic solutions too. Akin to the use of urea as a denaturation agent for proteins and other biopolymers [7][8][9][10], it is the single most commonly used additive to investigate the effect of nonelectrolytes on the micellization process of amphiphiles [11][12][13][14][15][16][17][18][19][20][21]; the reason being that demicellization is analogous to the denaturation of proteins. Urea has been found to increase the CMC, decrease the size of both ionic and nonionic micelles, and perturb the structure of molecular self-assemblies.…”

Section: Introductionmentioning

confidence: 99%

Effect of Temperature, Salts and Ureas on the Association Behavior of an Amphiphilic Phenothiazine Drug Promethazine Hydrochloride

Kabir-ud-Din

Rub

Naqvi

2012

J Surfact & Detergents

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Association behavior of an amphiphilic phenothiazine drug promethazine hydrochloride in the presence of inorganic salts (LiCl, NaF, NaCl, NaBr, and KCl) and ureas (urea and thiourea) has been studied conductometrically at different additive concentrations (0–100 mmol kg−1) and temperatures (293.15–308.15 K). The critical micelle concentration (CMC) values showed an inverted U‐shaped behavior with temperature; the maximum being at 298.15 K with or without additives. The inorganic salts decreased the CMC which is explained on the basis of nature and ion size. Ureas decreased the CMC at low concentration (0.2 mmol kg−1 urea and 0.1 mmol kg−1 thiourea) but, at higher concentrations, an increase in CMC was observed with both the additives. Relevant thermodynamic parameters were also evaluated and discussed on the basis of the nature of particular types of the additives. The thermodynamic parameters suggest dehydration of the hydrophobic part of the drug at higher temperatures.

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Tl+/Na+Competitive Binding at the Surface of Dodecylsulfate Micelles in Water–Urea Mixtures

Cited by 10 publications

References 8 publications

Effect of Urea on Biomimetic Systems: Neither Water 3-D Structure Rupture nor Direct Mechanism, Simply a More “Polar Water”

Effect of Urea on Biomimetic Systems: Neither Water 3-D Structure Rupture nor Direct Mechanism, Simply a More “Polar Water”

Supramolecular Recognition Induces Nonsynchronous Change of Dye Fluorescence Properties

Effect of Temperature, Salts and Ureas on the Association Behavior of an Amphiphilic Phenothiazine Drug Promethazine Hydrochloride

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