How protein chemists learned about the hydrophobic factor

Tanford, Charles

doi:10.1002/pro.5560060627

Cited by 151 publications

(126 citation statements)

References 56 publications

(38 reference statements)

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“…Tanford did not reply to Hildebrand immediately but he was careful afterwards to refer to the ''hydrophobic effect'' [19] and later to the ''hydrophobic factor'' [20], not to ''hydrophobic bonds''. Eleven years later, he replied [21] to Hildebrand by showing that the cohesive energy of water is large compared either to that of hexane or to the adhesive energy of water and hexane.…”

Section: Hydrophobic Free Energy Is the Sum Of Two Opposing Quantitiesmentioning

confidence: 99%

“…Another reason [27] was the short-range distance dependence of the attractive Lennard-Jones term. Note, however, that the water-ordering effect (which is discussed below) has been used to explain the water-hating behavior of non-polar groups [1,17,18,20] whereas the solute-solvent interaction (E a ) between water and hydrocarbon groups is favorable [15]. In 1974 Tanford and coworkers [27] said ''.…”

Section: The Cavity Work Scales With Molar Volumementioning

confidence: 99%

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The new view of hydrophobic free energy

Baldwin

2013

FEBS Letters

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a b s t r a c tIn the new view, hydrophobic free energy is measured by the work of solute transfer of hydrocarbon gases from vapor to aqueous solution. Reasons are given for believing that older values, measured by solute transfer from a reference solvent to water, are not quantitatively correct. The hydrophobic free energy from gas-liquid transfer is the sum of two opposing quantities, the cavity work (unfavorable) and the solute-solvent interaction energy (favorable). Values of the interaction energy have been found by simulation for linear alkanes and are used here to find the cavity work, which scales linearly with molar volume, not accessible surface area. The hydrophobic free energy is the dominant factor driving folding as judged by the heat capacity change for transfer, which agrees with values for solvating hydrocarbon gases. There is an apparent conflict with earlier values of hydrophobic free energy from studies of large-to-small mutations and an explanation is given. When an alkane solute is transferred from water through vapor to the liquid alkane, the liquid-liquid transfer may be written as two successive gas-liquid transfers [5]: first from water into vapor and then from vapor into liquid alkane. Kauzmann [1] and Tanford [2] expected that removing the hydrocarbon solute from water would account for most of the free energy change in liquid-liquid transfer but this expectation was not correct: data are available for the DG values of both gas-liquid transfers, which show that the ''hydrophobic'' transfer from water to vapor accounts for less than half of the total DG (5-7). This disconcerting fact was realized as early as 1976 when Wolfenden and Lewis [6] studied why water is a poor solvent for liquid hydrocarbons. They found that a strong favorable interaction among alkane molecules in liquid alkanes gives a strongly favorable transfer free energy for passage of an alkane solute from vapor into liquid alkane.Kauzmann [1] made an analogy between the protein folding process and the transfer of a non-polar solute from water into a reference solvent, since folding transfers the non-polar side chains of an unfolded protein out of water into a non-aqueous environment, the protein interior. It was well-known that water is a poor solvent for hydrocarbons, and Kauzmann showed that the DG for transferring a hydrocarbon out of water into a liquid hydrocarbon is substantial compared to the net DG for folding a small protein. For example, the DG for transfer from water to liquid alkane is À4.8 kcal/mol for butane, a hydrocarbon which has four carbon atoms like the side chains of leucine and isoleucine. Thus, he argued, a similar DG should help to fold a protein when a non-polar side chain is buried by folding. The analogy breaks down, however, when the liquid-liquid transfer is divided into two gas-liquid transfers [5], because the ''hydrophobic'' transfer from water into vapor has less than half of the total DG. and the second transfer, from vapor to liquid alkane, is not obviously related to the protein foldi...

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Section: Hydrophobic Free Energy Is the Sum Of Two Opposing Quantitiesmentioning

confidence: 99%

Section: The Cavity Work Scales With Molar Volumementioning

confidence: 99%

The new view of hydrophobic free energy

Baldwin

2013

FEBS Letters

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“…The principal impediment to progress in understanding hydrophobic interactions is the lack of an accessible direct observation of a primitive hydrophobic bond, such as the CH 4 · · · CH 4 potential of mean force. Because simple hydrophobic species, such as CH 4 , are only sparingly soluble in water, direct observations of primitive hydrophobic interactions are difficult to achieve; instead the influence of hydrophobic interactions is inferred in more complex systemssoluble proteins being the foremost example.…”

mentioning

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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“…Thus, mercury is not hydrophobic because it is insoluble in both solvents. Early work leading to the modern view of hydrophobic free energy is summarized by Tanford [11] and a recent discussion by Southall et al [12] provides a valuable perspective.…”

Section: Historymentioning

confidence: 99%

“…The molecular nature of hydrophobic free energy has been controversial for a long time [3,4,11,12]. A long-standing proposal, supported by liquid-liquid transfer data at 25 C [1] and by simulation results [27], is that the arrangement of water molecules in the solvation shell around a dissolved hydrocarbon is entropically unfavorable.…”

Section: 27mentioning

confidence: 99%

Weak Interactions in Protein Folding: Hydrophobic Free Energy, van der Waals Interactions, Peptide Hydrogen Bonds, and Peptide Solvation

Baldwin¹

2005

Protein Folding Handbook

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How protein chemists learned about the hydrophobic factor

Cited by 151 publications

References 56 publications

The new view of hydrophobic free energy

The new view of hydrophobic free energy

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

Weak Interactions in Protein Folding: Hydrophobic Free Energy, van der Waals Interactions, Peptide Hydrogen Bonds, and Peptide Solvation

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