Thermal signature of hydrophobic hydration dynamics
(2008) In Journal of the American Chemical Society 130(31). p.10345-10353- Abstract
- Hydrophobic hydration, the perturbation of the aqueous solvent near an apolar solute or interface, is a fundamental ingredient in many chemical and biological processes. Both bulk water and aqueous solutions of apolar solutes behave anomalously at low temperatures for reasons that are not fully understood. Here, we use 2H NMR relaxation to characterize the rotational dynamics in hydrophobic hydration shells over a wide temperature range, extending down to 243 K. We examine four partly hydrophobic solutes: the peptides N-acetyl-glycine-N′-methylamide and N-acetyl-leucine-N′-methylamide, and the osmolytes trimethylamine N-oxide and tetramethylurea. For all four solutes, we find that water rotates with lower activation energy in the hydration... (More)
- Hydrophobic hydration, the perturbation of the aqueous solvent near an apolar solute or interface, is a fundamental ingredient in many chemical and biological processes. Both bulk water and aqueous solutions of apolar solutes behave anomalously at low temperatures for reasons that are not fully understood. Here, we use 2H NMR relaxation to characterize the rotational dynamics in hydrophobic hydration shells over a wide temperature range, extending down to 243 K. We examine four partly hydrophobic solutes: the peptides N-acetyl-glycine-N′-methylamide and N-acetyl-leucine-N′-methylamide, and the osmolytes trimethylamine N-oxide and tetramethylurea. For all four solutes, we find that water rotates with lower activation energy in the hydration shell than in bulk water below 255 2 K. At still lower temperatures, water rotation is predicted to be faster in the shell than in bulk. We rationalize this behavior in terms of the geometric constraints imposed by the solute. These findings reverse the classical “iceberg” view of hydrophobic hydration by indicating that hydrophobic hydration water is less ice-like than bulk water. Our results also challenge the “structural temperature” concept. The two investigated osmolytes have opposite effects on protein stability but have virtually the same effect on water dynamics, suggesting that they do not act indirectly via solvent perturbations. The NMR-derived picture of hydrophobic hydration dynamics differs substantially from views emerging from recent quasielastic neutron scattering and pump−probe infrared spectroscopy studies of the same solutes. We discuss the possible reasons for these discrepancies. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/1227836
- author
- Qvist, Johan LU and Halle, Bertil LU
- organization
- publishing date
- 2008
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Journal of the American Chemical Society
- volume
- 130
- issue
- 31
- pages
- 10345 - 10353
- publisher
- The American Chemical Society (ACS)
- external identifiers
-
- wos:000258080600057
- scopus:48749129145
- pmid:18624406
- ISSN
- 1520-5126
- DOI
- 10.1021/ja802668w
- language
- English
- LU publication?
- yes
- id
- 5a683876-b9de-4247-8019-b649bafc6471 (old id 1227836)
- alternative location
- http://dx.doi.org/10.1021/ja802668w
- date added to LUP
- 2016-04-01 13:01:59
- date last changed
- 2022-04-13 22:45:36
@article{5a683876-b9de-4247-8019-b649bafc6471,
abstract = {{Hydrophobic hydration, the perturbation of the aqueous solvent near an apolar solute or interface, is a fundamental ingredient in many chemical and biological processes. Both bulk water and aqueous solutions of apolar solutes behave anomalously at low temperatures for reasons that are not fully understood. Here, we use 2H NMR relaxation to characterize the rotational dynamics in hydrophobic hydration shells over a wide temperature range, extending down to 243 K. We examine four partly hydrophobic solutes: the peptides N-acetyl-glycine-N′-methylamide and N-acetyl-leucine-N′-methylamide, and the osmolytes trimethylamine N-oxide and tetramethylurea. For all four solutes, we find that water rotates with lower activation energy in the hydration shell than in bulk water below 255 2 K. At still lower temperatures, water rotation is predicted to be faster in the shell than in bulk. We rationalize this behavior in terms of the geometric constraints imposed by the solute. These findings reverse the classical “iceberg” view of hydrophobic hydration by indicating that hydrophobic hydration water is less ice-like than bulk water. Our results also challenge the “structural temperature” concept. The two investigated osmolytes have opposite effects on protein stability but have virtually the same effect on water dynamics, suggesting that they do not act indirectly via solvent perturbations. The NMR-derived picture of hydrophobic hydration dynamics differs substantially from views emerging from recent quasielastic neutron scattering and pump−probe infrared spectroscopy studies of the same solutes. We discuss the possible reasons for these discrepancies.}},
author = {{Qvist, Johan and Halle, Bertil}},
issn = {{1520-5126}},
language = {{eng}},
number = {{31}},
pages = {{10345--10353}},
publisher = {{The American Chemical Society (ACS)}},
series = {{Journal of the American Chemical Society}},
title = {{Thermal signature of hydrophobic hydration dynamics}},
url = {{http://dx.doi.org/10.1021/ja802668w}},
doi = {{10.1021/ja802668w}},
volume = {{130}},
year = {{2008}},
}