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beta-Casein adsorption at the silicon oxide-aqueous solution interface: Calcium ion effects

Follows, D; Holt, C; Nylander, Tommy LU ; Thomas, R K and Tiberg, Fredrik LU (2004) In Biomacromolecules 5(2). p.319-325
Abstract
Neutron reflectometry was used to investigate effects of calcium ions on the interfacial behavior of beta-casein at the silicon oxide-aqueous solution interface. The structural characteristics of the adsorbed layer were determined from reflectivity curves fitted to three- and two-layer optical models. The results showed that the presence of divalent calcium ions decreased the specific electrostatic adsorption affinity of the protein to silica compared with the calcium-free buffer system studied in an earlier work. In addition, it speeded up the adsorption suggesting that the slow kinetics seen in the calcium-free system are related to conformational adjustments of the beta-casein structure driven by the maximization of the number of... (More)
Neutron reflectometry was used to investigate effects of calcium ions on the interfacial behavior of beta-casein at the silicon oxide-aqueous solution interface. The structural characteristics of the adsorbed layer were determined from reflectivity curves fitted to three- and two-layer optical models. The results showed that the presence of divalent calcium ions decreased the specific electrostatic adsorption affinity of the protein to silica compared with the calcium-free buffer system studied in an earlier work. In addition, it speeded up the adsorption suggesting that the slow kinetics seen in the calcium-free system are related to conformational adjustments of the beta-casein structure driven by the maximization of the number of positive charges on the polypeptide interacting with negative surface charges. In the calcium-free system, a dense inner layer resulted from this process, with cationic segments firmly bound to the negative surface, whereas in the presence of calcium, a less dense inner layer was formed. The difference in binding is also mirrored by the effects on the interfacial layer of a specific proteolytic enzyme, i.e., endoproteinase Asp-N. In the calcium-free case, an inner dense layer remained at the surface after the proteolytic cleavage of the polypeptide, whereas virtually nothing was left after enzymatic action in the presence of calcium ions. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Biomacromolecules
volume
5
issue
2
pages
319 - 325
publisher
The American Chemical Society
external identifiers
  • wos:000220109200010
  • scopus:1642443986
ISSN
1526-4602
DOI
10.1021/bm034301n
language
English
LU publication?
yes
id
64927fc7-6e1e-44b8-a44c-72ad5cb17827 (old id 154134)
date added to LUP
2007-07-11 11:52:13
date last changed
2017-07-02 03:44:15
@article{64927fc7-6e1e-44b8-a44c-72ad5cb17827,
  abstract     = {Neutron reflectometry was used to investigate effects of calcium ions on the interfacial behavior of beta-casein at the silicon oxide-aqueous solution interface. The structural characteristics of the adsorbed layer were determined from reflectivity curves fitted to three- and two-layer optical models. The results showed that the presence of divalent calcium ions decreased the specific electrostatic adsorption affinity of the protein to silica compared with the calcium-free buffer system studied in an earlier work. In addition, it speeded up the adsorption suggesting that the slow kinetics seen in the calcium-free system are related to conformational adjustments of the beta-casein structure driven by the maximization of the number of positive charges on the polypeptide interacting with negative surface charges. In the calcium-free system, a dense inner layer resulted from this process, with cationic segments firmly bound to the negative surface, whereas in the presence of calcium, a less dense inner layer was formed. The difference in binding is also mirrored by the effects on the interfacial layer of a specific proteolytic enzyme, i.e., endoproteinase Asp-N. In the calcium-free case, an inner dense layer remained at the surface after the proteolytic cleavage of the polypeptide, whereas virtually nothing was left after enzymatic action in the presence of calcium ions.},
  author       = {Follows, D and Holt, C and Nylander, Tommy and Thomas, R K and Tiberg, Fredrik},
  issn         = {1526-4602},
  language     = {eng},
  number       = {2},
  pages        = {319--325},
  publisher    = {The American Chemical Society},
  series       = {Biomacromolecules},
  title        = {beta-Casein adsorption at the silicon oxide-aqueous solution interface: Calcium ion effects},
  url          = {http://dx.doi.org/10.1021/bm034301n},
  volume       = {5},
  year         = {2004},
}