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Hydrogen exchange and hydration dynamics in gelatin gels

Vaca Chavez, Fabian LU ; Hellstrand, Erik LU and Halle, Bertil LU (2006) In The Journal of Physical Chemistry Part B 110(43). p.21551-21559
Abstract
Gelatin, derived from the collagen triple helix, is the most widely used functional biopolymer and a prototype for studies of physical gels. Gelatin gels have also served as models for soft biological tissue in efforts to elucidate the molecular basis of the magnetic relaxation phenomena that govern magnetic resonance image contrast. Yet, the microstructure, hydration, and magnetic relaxation behavior of gelatin gels are not well understood. To address these issues, we report here the water H-2 and O-17 magnetic relaxation dispersion (MRD) profiles from gelatin gels over wide ranges of resonance frequency and pH. For the global analysis of this extensive data set, we use a generalized relaxation theory that remains valid for arbitrarily... (More)
Gelatin, derived from the collagen triple helix, is the most widely used functional biopolymer and a prototype for studies of physical gels. Gelatin gels have also served as models for soft biological tissue in efforts to elucidate the molecular basis of the magnetic relaxation phenomena that govern magnetic resonance image contrast. Yet, the microstructure, hydration, and magnetic relaxation behavior of gelatin gels are not well understood. To address these issues, we report here the water H-2 and O-17 magnetic relaxation dispersion (MRD) profiles from gelatin gels over wide ranges of resonance frequency and pH. For the global analysis of this extensive data set, we use a generalized relaxation theory that remains valid for arbitrarily slow molecular dynamics. The strong pH dependence in the H-2 profiles can be rationalized quantitatively as the result of exchange with bulk water of labile hydrogens in gelatin side chains. The global analysis of the MRD data yields hydrogen-exchange rate constants, acid dissociation constants, and orientational order parameters in agreement with independent structural, thermodynamic, and kinetic data. The MRD analysis reveals a highly mobile hydration layer at the surface of the gelatin triple helix and a small number of trapped water molecules with residence times on the order of 10(-8) s, presumably associated with structural defects and branch points in the gel. The MRD data also indicate that similar to 20% of the gelatin residues belong to flexible polypeptide chains, rather than to rigid triple-helical segments. By identifying the molecular species and motions responsible for the H-2 and O-17 dispersion profiles, this study takes a significant step toward a quantitative understanding of water relaxation in aqueous gels and biological tissue. (Less)
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type
Contribution to journal
publication status
published
subject
in
The Journal of Physical Chemistry Part B
volume
110
issue
43
pages
21551 - 21559
publisher
The American Chemical Society (ACS)
external identifiers
  • wos:000241553500025
  • scopus:33751306108
ISSN
1520-5207
DOI
10.1021/jp057567s
language
English
LU publication?
yes
id
263424fd-433d-4e6e-a2b5-eba1b9b80be3 (old id 378762)
date added to LUP
2016-04-01 17:02:31
date last changed
2021-10-06 05:15:41
@article{263424fd-433d-4e6e-a2b5-eba1b9b80be3,
  abstract     = {Gelatin, derived from the collagen triple helix, is the most widely used functional biopolymer and a prototype for studies of physical gels. Gelatin gels have also served as models for soft biological tissue in efforts to elucidate the molecular basis of the magnetic relaxation phenomena that govern magnetic resonance image contrast. Yet, the microstructure, hydration, and magnetic relaxation behavior of gelatin gels are not well understood. To address these issues, we report here the water H-2 and O-17 magnetic relaxation dispersion (MRD) profiles from gelatin gels over wide ranges of resonance frequency and pH. For the global analysis of this extensive data set, we use a generalized relaxation theory that remains valid for arbitrarily slow molecular dynamics. The strong pH dependence in the H-2 profiles can be rationalized quantitatively as the result of exchange with bulk water of labile hydrogens in gelatin side chains. The global analysis of the MRD data yields hydrogen-exchange rate constants, acid dissociation constants, and orientational order parameters in agreement with independent structural, thermodynamic, and kinetic data. The MRD analysis reveals a highly mobile hydration layer at the surface of the gelatin triple helix and a small number of trapped water molecules with residence times on the order of 10(-8) s, presumably associated with structural defects and branch points in the gel. The MRD data also indicate that similar to 20% of the gelatin residues belong to flexible polypeptide chains, rather than to rigid triple-helical segments. By identifying the molecular species and motions responsible for the H-2 and O-17 dispersion profiles, this study takes a significant step toward a quantitative understanding of water relaxation in aqueous gels and biological tissue.},
  author       = {Vaca Chavez, Fabian and Hellstrand, Erik and Halle, Bertil},
  issn         = {1520-5207},
  language     = {eng},
  number       = {43},
  pages        = {21551--21559},
  publisher    = {The American Chemical Society (ACS)},
  series       = {The Journal of Physical Chemistry Part B},
  title        = {Hydrogen exchange and hydration dynamics in gelatin gels},
  url          = {http://dx.doi.org/10.1021/jp057567s},
  doi          = {10.1021/jp057567s},
  volume       = {110},
  year         = {2006},
}