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Microscopic Probing...
Microscopic Probing of the Size Dependence in Hydrophobic Solvation
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- Huang, Ningdong (author)
- Stanford Synchrotron Radiat Lab, Stanford, CA 94309 USA
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- Nordlund, Dennis (author)
- Stanford Synchrotron Radiat Lab, Stanford, CA 94309 USA
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- Huang, Congcong (author)
- Stanford Synchrotron Radiat Lab, Stanford, CA 94309 USA
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- Tyliszczak, Tolek (author)
- LBL, Adv Light Source, Berkeley, CA 94720 USA
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- Weiss, Thomas M. (author)
- Stanford Synchrotron Radiat Lab, Stanford, CA 94309 USA
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- Acremann, Yves (author)
- Stanford Synchrotron Radiat Lab, Stanford, CA 94309 USA
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- Pettersson, Lars G.M. (author)
- Stockholms universitet,Fysikum,Kvantkemi
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- Nilsson, Anders (author)
- Stockholms universitet,Fysikum
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- Schlesinger, Daniel (author)
- Stockholms universitet,Fysikum
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(creator_code:org_t)
- AIP Publishing, 2012
- 2012
- English.
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In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 136:7, s. 074507-
- Related links:
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https://urn.kb.se/re...
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https://doi.org/10.1...
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Abstract
Subject headings
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- A dependence on solute size of the hydrophobic effect has been proposed based on theory and simulations, such that small apolar solutes leave the hydrogen (H-) bonding network in water intact or even strengthened, whereas hydration of larger, nanometer-sized apolar solutes breaks hydrogen bonds and creates a liquid-vapor-like interface around the solutes. Here we report the direct experimental microscopic observation of the small-to-large crossover behavior of hydrophobic effects in aqueous solutions of amphiphilic tetraalkyl-ammonium (CnH2n+1)4N + (TAA) cations with increased side chain length by probing the H-bonding network in water through O K-edge x-ray absorption spectroscopy and the solute-solute interaction using small angle x-ray scattering. These results open for unique experimental opportunities to investigate hydrophobic effects for a range of important processes in chemistry and biology.We report small angle x-ray scattering data demonstrating the direct experimental microscopic observation of the small-to-large crossover behavior of hydrophobic effects in hydrophobic solvation. By increasing the side chain length of amphiphilic tetraalkyl-ammonium (CnH2n+1)4N+ (R4N+) cations in aqueous solution we observe diffraction peaks indicating association between cations at a solute size between 4.4 and 5 Å, which show temperature dependence dominated by hydrophobic attraction. Using O K-edge x-ray absorption we show that small solutes affect hydrogen bonding in water similar to a temperature decrease, while large solutes affect water similar to a temperature increase. Molecular dynamics simulations support, and provide further insight into, the origin of the experimental observations.
Subject headings
- NATURVETENSKAP -- Fysik -- Annan fysik (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Other Physics Topics (hsv//eng)
Keyword
- hydrogen bonds
- hydrophobicity
- molecular dynamics method
- organic compounds
- positive ions
- solvation
- solvent effects
- X-ray absorption spectra
- X-ray scattering
- kemisk fysik
- Chemical Physics
Publication and Content Type
- ref (subject category)
- art (subject category)
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