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Molecular origin of time-dependent fluorescence shifts in proteins

Nilsson, Lennart LU and Halle, Bertil LU (2005) In Proceedings of the National Academy of Sciences 102(39). p.13867-13872
Abstract
Time-resolved fluorescence spectroscopy is used increasingly to probe molecular motions at the aqueous interfaces of biological macromolecules and membranes. By recording the time variation of the fluorescence frequency, thermal atomic fluctuations in the vicinity of the chromophore can be probed. From such fluorescence Stokes shift (FSS) experiments, it has been inferred that water motions in the hydration layer are slowed down by 1-3 orders of magnitude. To provide a more secure foundation for the interpretation of FSS data, we use molecular dynamics simulations to examine the molecular origin of the FSS from a tryptophan residue in a protein. By using linear response theory to decompose the FSS into its water and protein components, we... (More)
Time-resolved fluorescence spectroscopy is used increasingly to probe molecular motions at the aqueous interfaces of biological macromolecules and membranes. By recording the time variation of the fluorescence frequency, thermal atomic fluctuations in the vicinity of the chromophore can be probed. From such fluorescence Stokes shift (FSS) experiments, it has been inferred that water motions in the hydration layer are slowed down by 1-3 orders of magnitude. To provide a more secure foundation for the interpretation of FSS data, we use molecular dynamics simulations to examine the molecular origin of the FSS from a tryptophan residue in a protein. By using linear response theory to decompose the FSS into its water and protein components, we find that the water component dominates the static FSS but decays rapidly. Thus, after a few picoseconds, the FSS essentially reflects protein dynamics, including the self-motion of the chromophore. Because of its collective nature, the FSS response is insensitive to the motion of individual water molecules. Collective water displacement by slowly fluctuating protein groups introduces a long-time-tail in the water autocorrelation function, but this dynamic coupling is hardly manifested in the observed FSS. Our analysis reconciles FSS data with the picture of a highly dynamic hydration layer, derived mainly from magnetic relaxation dispersion and simulation studies, and calls for a revision of previous interpretations of FSS decays in terms of slow hydration dynamics at biomolecular and other interfaces. (Less)
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organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Proceedings of the National Academy of Sciences
volume
102
issue
39
pages
13867 - 13872
publisher
National Acad Sciences
external identifiers
  • wos:000232231900030
  • scopus:25444496478
ISSN
1091-6490
DOI
10.1073/pnas.0504181102
language
English
LU publication?
yes
id
2d59d1d6-c8db-4aef-911c-ce6436bf26d4 (old id 151496)
date added to LUP
2007-06-29 14:08:32
date last changed
2017-08-27 03:47:04
@article{2d59d1d6-c8db-4aef-911c-ce6436bf26d4,
  abstract     = {Time-resolved fluorescence spectroscopy is used increasingly to probe molecular motions at the aqueous interfaces of biological macromolecules and membranes. By recording the time variation of the fluorescence frequency, thermal atomic fluctuations in the vicinity of the chromophore can be probed. From such fluorescence Stokes shift (FSS) experiments, it has been inferred that water motions in the hydration layer are slowed down by 1-3 orders of magnitude. To provide a more secure foundation for the interpretation of FSS data, we use molecular dynamics simulations to examine the molecular origin of the FSS from a tryptophan residue in a protein. By using linear response theory to decompose the FSS into its water and protein components, we find that the water component dominates the static FSS but decays rapidly. Thus, after a few picoseconds, the FSS essentially reflects protein dynamics, including the self-motion of the chromophore. Because of its collective nature, the FSS response is insensitive to the motion of individual water molecules. Collective water displacement by slowly fluctuating protein groups introduces a long-time-tail in the water autocorrelation function, but this dynamic coupling is hardly manifested in the observed FSS. Our analysis reconciles FSS data with the picture of a highly dynamic hydration layer, derived mainly from magnetic relaxation dispersion and simulation studies, and calls for a revision of previous interpretations of FSS decays in terms of slow hydration dynamics at biomolecular and other interfaces.},
  author       = {Nilsson, Lennart and Halle, Bertil},
  issn         = {1091-6490},
  language     = {eng},
  number       = {39},
  pages        = {13867--13872},
  publisher    = {National Acad Sciences},
  series       = {Proceedings of the National Academy of Sciences},
  title        = {Molecular origin of time-dependent fluorescence shifts in proteins},
  url          = {http://dx.doi.org/10.1073/pnas.0504181102},
  volume       = {102},
  year         = {2005},
}