Analysis of Main- and Cross-Term Diffusion Coefficients in Bile Salt Mixtures

Mangiapia, Gaetano; Paduano, Luigi; Ortona, Ornella; Sartorio, Roberto; D’Errico, Gerardino

doi:10.1021/jp309945f

Cited by 5 publications

(2 citation statements)

References 40 publications

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“…(In the context of active colloids, the conditions under which this assumption is expected to hold are discussed in more detail in [92].) Although these crossterms are sometimes important even for dilute solutions [113], our use of this approximation is motivated by previous reports showing that in many cases the diffusion coefficients (accounting for currents driven by concentration gradients, which are the most relevant terms in our system) in ternary mixtures are such that the cross-terms induced contrib utions are much smaller than the ones due to self-diffusion [115][116][117][118][119][120]. (But we note that recently for a ternary mixture crossterm diffusion coefficients have been reported which are of the same order of magnitude as the self-diffusion ones [121]; however, this was found for comparable concentrations and thus far from the dilute solution limit we are considering here.)…”

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confidence: 99%

Active colloids in the context of chemical kinetics

Oshanin

Popescu

Dietrich

2017

J. Phys. A: Math. Theor.

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We study a mesoscopic model of a chemically active colloidal particle which on certain parts of its surface promotes chemical reactions in the surrounding solution. For reasons of simplicity and conceptual clarity, we focus on the case in which only electrically neutral species are present in the solution and on chemical reactions which are described by first order kinetics. Within a self-consistent approach we explicitly determine the steady state product and reactant number density fields around the colloid as functionals of the interaction potentials of the various molecular species in solution with the colloid. By using Teubner's reciprocal theorem, this allows us to compute and to interpret -in a transparent way in terms of the classical Smoluchowski theory of chemical kinetics -the external force needed to keep such a catalytically active colloid at rest (stall force) or, equivalently, the corresponding velocity of the colloid if it is free to move. We use the particular case of triangularwell interaction potentials as a benchmark example for applying the general theoretical framework developed here. For this latter case, we derive explicit expressions for the dependences of the quantities of interest on the diffusion coefficients of the chemical species, the reaction rate constant, the coverage by catalyst, the size of the colloid, as well as on the parameters of the interaction potentials. These expressions provide a detailed picture of the phenomenology associated with catalytically-active colloids and self-diffusiophoresis.

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Section: And By Being Truncated Atmentioning

confidence: 99%

Active colloids in the context of chemical kinetics

Oshanin

Popescu

Dietrich

2017

J. Phys. A: Math. Theor.

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“…Although the off-diagonal diffusivities D as and D sa are often negligible in liquid solutions with weakly interacting components, it has become increasingly clear that, in other mixtures with strongly interacting components, they can be significant. Non-negligible cross diffusivities have been measured in a variety of aqueous surfactant solutions, including systems with ionic surfactant and solute, ,,, nonionic or zwitterionic surfactant and solute, − , and aqueous solutions with mixed surfactants. − …”

Section: Introductionmentioning

confidence: 99%

Multicomponent Diffusion in Aqueous Solutions of Nonionic Micelles and Decane

2019

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Taylor dispersion and dynamic light scattering techniques were used to measure the ternary diffusivity matrix [D] and the micelle gradient diffusion coefficient, respectively, in crowded aqueous solutions of decaethylene glycol monododecyl ether (C12E10) and decane. The results indicate that C12E10 diffused down its own gradient with the micelle gradient diffusivity while decane diffused down a decane gradient at a much slower rate. Furthermore, strong diffusion coupling, comprising decane diffusion down a surfactant gradient and surfactant diffusion up a decane gradient, was also observed with cross diffusivities that were on the order of or larger than the main diffusivities. Measurements of the micelle aggregation number, hydration index, and the hydrodynamic radius, obtained using both static and dynamic light scattering methods, indicate that decane-containing micelles interacted as hard spheres and had radii and aggregation numbers that increased linearly with the molar ratio of solute to surfactant. A theoretical model, developed using Batchelor’s theory for gradient diffusion in a polydisperse system of interacting hard spheres, was effectively used to predict [D] with no adjustable parameters. A comparison with the theory indicates that decane diffused down its own gradient by micelle self-diffusion while surfactant diffused down a surfactant gradient by micelle gradient diffusion. It is also shown that intermicellar interactions drove decane diffusion down a C12E10 gradient by a volume exclusion effect while an increase in the micelle aggregation number and hydrodynamic radius with decane was necessary to drive surfactant diffusion up a decane gradient.

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Structural and Functional Implications of the Interaction between Macrolide Antibiotics and Bile Acids

Glanzer

Pulido

Tutz

et al. 2015

Chemistry A European J

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Macrolide antibiotics, such as azithromycin and erythromycin, are in widespread use for the treatment of bacterial infections. Macrolides are taken up and excreted mainly by bile. Additionally, they have been implicated in biliary system diseases and to modify the excretion of other drugs through bile. Despite mounting evidence for the interplay between macrolide antibiotics and bile acids, the molecular details of this interaction remain unknown. Herein, we show by NMR measurements that macrolides directly bind to bile acid micelles. The topology of this interaction has been determined by solvent paramagnetic relaxation enhancements (solvent PREs). The macrolides were found to be bound close to the surface of the micelle. Increasing hydrophobicity of both the macrolide and the bile acid strengthen this interaction. Both bile acid and macrolide molecules show similar solvent PREs across their whole structures, indicating that there are no preferred orientations of them in the bile micelle aggregates. The binding to bile aggregates does not impede macrolide antibiotics from targeting bacteria. In fact, the toxicity of azithromycin towards enterotoxic E. coli (ETEC) is even slightly increased in the presence of bile, as was shown by effective concentration (EC50) values.

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Analysis of Main- and Cross-Term Diffusion Coefficients in Bile Salt Mixtures

Cited by 5 publications

References 40 publications

Active colloids in the context of chemical kinetics

Active colloids in the context of chemical kinetics

Multicomponent Diffusion in Aqueous Solutions of Nonionic Micelles and Decane

Structural and Functional Implications of the Interaction between Macrolide Antibiotics and Bile Acids

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