Methane Hydration‐Shell Structure and Fragility

Wu, Xiangen; Lü, Wanjun; Streacker, Louis M.; Ashbaugh, Henry S.; Ben‐Amotz, Dor

doi:10.1002/anie.201809372

Cited by 46 publications

(60 citation statements)

References 40 publications

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“…Figure S7 The hydrophobic related tetrahedral enhancement (Fig. 5(a)), consistent with previous simulation 22,37,38,[40][41][42][43][44][45] and experimental [46][47][48] studies for different hydrophobic molecules and groups, but at odds with neutron diffraction experiments [34][35][36] , is completely lost at high temperatures for methane and neopentane, but not for methanol and neopentanol (see Fig. 5c).…”

Section: Molecular Solvation Analysissupporting

confidence: 88%

“…While not observed through neutron diffraction experiments [34][35][36] a tetrahedral enhancement of some water molecules next to small hydrophobic and amphiphilic molecules has been recently observed through molecular dynamics 22,[37][38][39][40][41][42][43][44][45] , Raman scattering measurements with multivariate curve resolution 46,47 , and infrared spectroscopy 48,49 . The significance of these structural changes on the hydration thermodynamics, including its temperature dependence, remains, however, poorly understood.…”

Section: S T~mentioning

confidence: 99%

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Protein Denaturation, Zero Entropy Temperature, and the Structure of Water around Hydrophobic and Amphiphilic Solutes

Nas

Galamba

2020

J. Phys. Chem. B

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The hydrophobic effect plays a key role in many chemical and biological processes, including protein folding. Nonetheless, a comprehensive picture of the effect of temperature on hydrophobic hydration and protein denaturation remains elusive. Here, we study the effect of temperature on the hydration of model hydrophobic and amphiphilic solutes, through molecular dynamics, aiming at getting insight on the singular behavior of water, concerning the zero-entropy temperature, T S , and entropy convergence, T S *, also observed for some proteins, upon denaturation. We show that, similar to hydrocarbons, polar amphiphilic solutes exhibit a T S , although strongly dependent on solute–water interactions, opposite to hydrocarbons. Further, the temperature dependence of the hydration entropy, normalized by the solvent accessible surface area, is shown to be nearly solute size independent for hydrophobic but not for amphiphilic solutes, for similar reasons. These results are further discussed in the light of information theory (IT) and the structure of water around hydrophobic groups. The latter shows that the tetrahedral enhancement of some water molecules around hydrophobic groups, associated with the reduction of water defects, leads to the strengthening of the weakest hydrogen bonds, relative to bulk water. In addition, a larger tetrahedrality is found in low density water populations, demonstrating that pure water has encoded structural information, similar to that associated with hydrophobic hydration. The reversal of the hydration entropy dependence on the solute size, above T S *, is also analyzed and shown to be associated with a greater loss of water molecules exhibiting enhanced orientational order, in the coordination sphere of large solutes. Finally, the source of the differences between Kauzmann’s “hydrocarbon model” on protein denaturation and hydrophobic hydration is discussed, with relatively large amphiphilic hydrocarbons seemingly displaying a more similar behavior to some globular proteins than aliphatic hydrocarbons.

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Section: Molecular Solvation Analysissupporting

confidence: 88%

Section: S T~mentioning

confidence: 99%

Protein Denaturation, Zero Entropy Temperature, and the Structure of Water around Hydrophobic and Amphiphilic Solutes

Nas

Galamba

2020

J. Phys. Chem. B

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“…Frequency scaling corrections for MP2/aug-cc-pVTZ were applied to all AFM spectra according to the literature. 101 Experimental Raman spectra are shown in black for methane, 102 methanol, 103 ethane, 104 and ethanol. 103 Peak intensities have been scaled arbitrarily to aid viewing.…”

Section: Resultsmentioning

confidence: 99%

Accurate MP2-based force fields predict hydration free energies for simple alkanes and alcohols in good agreement with experiments

Rogers

Wang

2020

The Journal of Chemical Physics

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Force fields for four small molecules, methane, ethane, methanol, and ethanol, were created by force matching MP2 gradients computed with triple-zeta-quality basis sets using the Adaptive Force Matching method. Without fitting to any experimental properties, the force fields created were able to predict hydration free energies, enthalpies of hydration, and diffusion constants in excellent agreements with experiments. The root mean square error for the predicted hydration free energies is within 1 kJ/mol of experimental measurements of Ben-Naim et al. [J. Chem. Phys. 81(4), 2016–2027 (1984)]. The good prediction of hydration free energies is particularly noteworthy, as it is an important fundamental property. Similar hydration free energies of ethane relative to methane and of ethanol relative to methanol are attributed to a near cancellation of cavitation penalty and favorable contributions from dispersion and Coulombic interactions as a result of the additional methyl group.

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“…While not observed through neutron diffraction experiments(30-32) a tetrahedral enhancement of some water molecules next to small hydrophobic and amphiphilic molecules has been recently observed through molecular dynamics (17,(33)(34)(35)(36)(37)(38)(39)(40)(41), Raman scattering measurements with multivariate curve resolution (42,43) and infrared spectroscopy (44,45). Notice that any structural enhancement related to the reorganization of water upon insertion of the solute, while not contributing to the free energy (enthalpy-entropy compensation), still contributes to the hydration entropy and enthalpy.…”

Section: Introductionmentioning

confidence: 99%

Protein Denaturation Zero Entropy Temperature, and the Structure of Water Around Hydrophobic and Amphiphilic Solutes

Tamoliūnas¹,

Galamba

2020

Preprint

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The hydrophobic effect plays a key role in many chemical and biological processes, including protein folding. Nonetheless, a comprehensive picture of the effect of temperature on hydrophobic hydration and protein denaturation remains elusive. Here, we study the effect of temperature on the hydration of model hydrophobic and amphiphilic solutes through molecular dynamics aiming at getting in sight on the singular behavior of water concerning the zero entropy temperature TS and entropic convergence also observed upon protein denaturation. We show that, similar to hydrocarbons and proteins, polar amphiphilic solutes exhibit a TS, although strongly dependent upon solute-water interactions, opposite to hydrocarbons. Further, the temperature dependence of the hydration entropy normalized by the solvent accessible surface area is shown to be nearly solute size independent for hydrophobic but not for amphiphilic solutes, for similar reasons. These results are further discussed in the light of information theory (IT) and the structure of water around hydrophobic groups The latter shows that the tetrahedral enhancement of some water molecules around hydrophobic groups, associated with the reduction of water defects, leads to the strengthening of the weakest hydrogen bonds, relative to bulk water. However, a larger tetrahedrality is found in low density water populations, demonstrating that pure water has encoded structural information similar to that associated with hydrophobic hydration, consistent with IT assumptions. The source of the differences between Kauzmann's "hydrocarbon model" on protein denaturation and hydrophobic hydration is also discussed with relatively large amphiphilic hydrocarbons displaying a more similar behavior to globular proteins, than aliphatic hydrocarbons.<br>

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Methane Hydration‐Shell Structure and Fragility

Cited by 46 publications

References 40 publications

Protein Denaturation, Zero Entropy Temperature, and the Structure of Water around Hydrophobic and Amphiphilic Solutes

Protein Denaturation, Zero Entropy Temperature, and the Structure of Water around Hydrophobic and Amphiphilic Solutes

Accurate MP2-based force fields predict hydration free energies for simple alkanes and alcohols in good agreement with experiments

Protein Denaturation Zero Entropy Temperature, and the Structure of Water Around Hydrophobic and Amphiphilic Solutes

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