A prototype hydrophobic interaction.  The dimerization of benzene in water

Tucker, Edwin E.; Christian, Sherril D.

doi:10.1021/j100466a026

Cited by 74 publications

(47 citation statements)

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“…The osmotic second virial coefficient has so far been the only direct experimental check on the molecular theory of hydrophobic interactions between slightly soluble gases (A) in liquid water (3)(4)(5)(6). Here g AA (r) is the usual radial distribution function of AA pairs at infinite dilution.…”

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confidence: 99%

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Molecular-scale hydrophobic interactions between hard-sphere reference solutes are attractive and endothermic

Chaudhari

Holleran

Ashbaugh

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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The osmotic second virial coefficients, B 2 , for atomic-sized hard spheres in water are attractive (B 2 < 0) and become more attractive with increasing temperature (ΔB 2 /ΔT < 0) in the temperature range 300 K ≤ T ≤ 360 K. Thus, these hydrophobic interactions are attractive and endothermic at moderate temperatures. Hydrophobic interactions between atomic-sized hard spheres in water are more attractive than predicted by the available statistical mechanical theory. These results constitute an initial step toward detailed molecular theory of additional intermolecular interaction features, specifically, attractive interactions associated with hydrophobic solutes.protein folding | self-assembly | Pratt-Chandler theory S olvent-mediated, noncovalent interactions within biomolecular structures are decisive for their stability and functionality over an extended range of conditions (1). Hydrophobic interactions-a principal category of noncovalent interactions in water-exhibit strong and characteristic temperature dependences (2). Molecular-scale theories of hydrophobic interactions are judged by their ability to capture those temperature dependences. Defensible theories might eventually illuminate a valid explanation and might find broader utility in modeling biomolecular structure and function.The osmotic second virial coefficienthas so far been the only direct experimental check on the molecular theory of hydrophobic interactions between slightly soluble gases (A) in liquid water (3-6). Here g AA (r) is the usual radial distribution function of AA pairs at infinite dilution. Because of low solubilities for solutes of interest, the necessary experiments are challenging. The initial comparisons between the only available molecular-scale theory, the Pratt-Chandler (PC) theory (7), and direct measurements of B 2 showed poor agreement (3-5, 8).Explanations for the discrepancy have been suggested (9-11), but the underlying disagreement has persisted (12). One explanation for this discrepancy focused on the differences between the actual interactions for accessible experimental cases and the hard-sphere solute-water interactions natural for the molecular theory. In this setting, direct high-resolution determination of hydrophobic interactions for the hard-sphere models treated by the theory would be a helpful step, but that has not been accomplished so far. The case of atomic-sized hardsphere solutes has not been treated specifically, mostly because hard-sphere models are inconvenient in available molecular dynamics simulations.These problems are of basic importance because hydrophobic interactions are acknowledged as the dominant factor that drives protein folding (13,14). Hydrophobic interactions are also expected to become more favorable with increasing temperature for physiological temperatures. Hydrophobic interactions can then be described as favorable for aggregation and endothermic at moderate temperatures. This is a primary conceptual puzzle that theories of hydrophobic effects should clarify.Summaries of the substa...

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confidence: 99%

“…Because of low solubilities for solutes of interest, the necessary experiments are challenging. The initial comparisons between the only available molecular-scale theory, the Pratt-Chandler (PC) theory (7), and direct measurements of B 2 showed poor agreement (3)(4)(5)8).…”

mentioning

confidence: 99%

Molecular-scale hydrophobic interactions between hard-sphere reference solutes are attractive and endothermic

Chaudhari

Holleran

Ashbaugh

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…7 Limited thermodynamic evaluation of hydrophobic interactions has been experimentally achieved for soluble, but more complex hydrophobic species with higher aqueous solubilities. 14,15 Those experiments set off a substantial modeling effort that has not untangled this complicated issue. 11 Here we show ( Fig.…”

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confidence: 99%

Communication: Direct observation of a hydrophobic bond in loop closure of a capped (–OCH $_2$2CH $_2$2–) $_n$n oligomer in water

Chaudhari

Pratt

Paulaitis

2010

The Journal of Chemical Physics

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The small r variation of the probability density P(r) for end-to-end separations of a –CH \documentclass[12pt]{minimal}\begin{document}$_2$\end{document}2CH \documentclass[12pt]{minimal}\begin{document}$_3$\end{document}3 capped (–OCH \documentclass[12pt]{minimal}\begin{document}$_2$\end{document}2CH \documentclass[12pt]{minimal}\begin{document}$_2$\end{document}2–) \documentclass[12pt]{minimal}\begin{document}$_n$\end{document}n oligomer in water is computed to be closely similar to the CH \documentclass[12pt]{minimal}\begin{document}$_4\cdots$\end{document}4⋯ CH \documentclass[12pt]{minimal}\begin{document}$_4$\end{document}4 potential of mean force under the same circumstances. Since the aqueous solution CH \documentclass[12pt]{minimal}\begin{document}$_4\cdots$\end{document}4⋯ CH \documentclass[12pt]{minimal}\begin{document}$_4$\end{document}4 potential of mean force is the natural physical definition of a primitive hydrophobic bond, the present result identifies an experimentally accessible circumstance for direct observation of a hydrophobic bond which has not been observed previously because of the low solubility of CH \documentclass[12pt]{minimal}\begin{document}$_4$\end{document}4 in water. The physical picture is that the soluble chain molecules carry the capping groups into aqueous solution, and permits them to find one another with reasonable frequency. Comparison with the corresponding results without the solvent shows that hydration of the solute oxygen atoms swells the chain molecule globule. This supports the view that the chain molecule globule might have a secondary effect on the hydrophobic interaction that is of first interest here. The volume of the chain molecule globule is important for comparing the probabilities with and without solvent because it characterizes the local concentration of capping groups. Study of other capping groups to enable x-ray and neutron diffraction measurements of P(r) is discussed.

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“…Benzene interacts favorably with itself under appropriate conditions. For example, it dimerizes in water [42,43]. Furthermore, mass-action models based on the distribution of benzene among SOS micelles, with and without added electrolyte, are consistent with a stabilizing pairwise intramicellar interaction of benzene providing 220 to 230 cal/mol, depending on micellar size [19,36].…”

Section: Origin Of Diffuse Fronts and Sharp Rears Of Peaks In Mekcmentioning

confidence: 73%

Origin of peak asymmetry and isotherm nonlinearity in micellar electrokinetic chromatography: Variation of peak shape with buffer concentration

Williamson¹,

Davis²

2006

Electrophoresis

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The diffuse fronts and sharp rears of peaks of nitrobenzene (nbz) solubilized at high concentrations in 50 mM SDS and 2.5, 25, and 50 mM sodium tetraborate buffers were modeled in MEKC by measurements of, and fits to, concave upward isotherms, and by numerical solution of the continuity equation. The isotherms varied with buffer concentration, with the smallest limiting slope and largest curvature found for the 50 mM tetraborate buffer. The Brunauer, Emmett, and Teller isotherm described the peak profiles in all buffers, with symmetrical peaks observed at sub- and low-mM levels of nbz, anti-Langmuirian peaks observed at 10-20 mM levels, and aquiline peaks resembling curved noses observed at 20-30 mM levels. The variation of the partition coefficient with nbz and buffer concentrations was shown to result from nonideal thermodynamics. High-buffer concentrations salt out nbz from the mobile phase, as quantified by a mobile-phase activity coefficient related to the Setchenov constant of nbz in sodium tetraborate. The activity coefficient of nbz in SDS micelles was shown to resemble that measured by other researchers for benzene in micelles of sodium octyl sulfate, i.e. it decreases with increasing solute concentration and increases with electrolyte concentration. Many examples from the literature are discussed, in which the variation of the intramicellar activity coefficient with solute mole fraction is consistent with peaks having diffuse fronts and sharp rears.

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A prototype hydrophobic interaction. The dimerization of benzene in water

Cited by 74 publications

References 1 publication

Molecular-scale hydrophobic interactions between hard-sphere reference solutes are attractive and endothermic

Molecular-scale hydrophobic interactions between hard-sphere reference solutes are attractive and endothermic

Communication: Direct observation of a hydrophobic bond in loop closure of a capped (–OCH $_2$2CH $_2$2–) $_n$n oligomer in water

Origin of peak asymmetry and isotherm nonlinearity in micellar electrokinetic chromatography: Variation of peak shape with buffer concentration

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