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Aggregation in a protein-surfactant system. The interplay between hydrophobic and electrostatic interactions

Stenstam, Anna LU ; Topgaard, Daniel LU and Wennerström, Håkan LU (2003) In The Journal of Physical Chemistry Part B 107(32). p.7987-7992
Abstract
By precipitating a complex salt Ly(OS)(8) of the positively charged protein lysozyme and the anionic surfactant octyl sulfate OS-, one can generate a true ternary system: water-Ly(OS)(8)-NaOS. Using NMR diffusometry and U

spectroscopy measurements the thermodynamic parameters of the association processes have been determined. The solubility product of the complex salt, K-s, is 10-(28) M-9.(1) On addition of excess surfactant the complex salt is solubilized into micelles that form at a critical association concentration of 74 mM which is nearly a factor of 2 lower than the CMC of 133 mM. At higher protein and surfactant concentrations these micelles first coexist with gel aggregates. The thermodynamically stable gel phase is... (More)
By precipitating a complex salt Ly(OS)(8) of the positively charged protein lysozyme and the anionic surfactant octyl sulfate OS-, one can generate a true ternary system: water-Ly(OS)(8)-NaOS. Using NMR diffusometry and U

spectroscopy measurements the thermodynamic parameters of the association processes have been determined. The solubility product of the complex salt, K-s, is 10-(28) M-9.(1) On addition of excess surfactant the complex salt is solubilized into micelles that form at a critical association concentration of 74 mM which is nearly a factor of 2 lower than the CMC of 133 mM. At higher protein and surfactant concentrations these micelles first coexist with gel aggregates. The thermodynamically stable gel phase is observed at protein concentrations higher than 7 wt % and has a stoichiometry of around 28 OS- per protein molecule. Thereafter, in the presence of more than ca. 30 OS- per protein, micelles containing a single lysozyme molecule are formed from the gel aggregates. This rich aggregation pattern can be described as caused by a combination of an attractive hydrophobic interaction between hydrophobic patches on the protein surface and the surfactant hydrocarbon chain, and a composition-dependent electrostati

interaction between charged amino acids and the surfactant headgroup. The net

force is attractive up to a ratio of surfactant to protein of 8, after

which it becomes increasingly repulsive. The gel phase occurs as a

compromise between the attractive hydrophobic interaction and the

relatively weak electrostatic repulsion. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
The Journal of Physical Chemistry Part B
volume
107
issue
32
pages
7987 - 7992
publisher
The American Chemical Society
external identifiers
  • wos:000184665000003
  • scopus:0041887364
ISSN
1520-5207
DOI
10.1021/jp0224158
language
English
LU publication?
yes
id
445ad5e1-f103-4c32-a968-28f7660f5e73 (old id 122218)
date added to LUP
2007-07-12 11:59:54
date last changed
2018-09-30 04:07:19
@article{445ad5e1-f103-4c32-a968-28f7660f5e73,
  abstract     = {By precipitating a complex salt Ly(OS)(8) of the positively charged protein lysozyme and the anionic surfactant octyl sulfate OS-, one can generate a true ternary system: water-Ly(OS)(8)-NaOS. Using NMR diffusometry and U<br/><br>
 spectroscopy measurements the thermodynamic parameters of the association processes have been determined. The solubility product of the complex salt, K-s, is 10-(28) M-9.(1) On addition of excess surfactant the complex salt is solubilized into micelles that form at a critical association concentration of 74 mM which is nearly a factor of 2 lower than the CMC of 133 mM. At higher protein and surfactant concentrations these micelles first coexist with gel aggregates. The thermodynamically stable gel phase is observed at protein concentrations higher than 7 wt % and has a stoichiometry of around 28 OS- per protein molecule. Thereafter, in the presence of more than ca. 30 OS- per protein, micelles containing a single lysozyme molecule are formed from the gel aggregates. This rich aggregation pattern can be described as caused by a combination of an attractive hydrophobic interaction between hydrophobic patches on the protein surface and the surfactant hydrocarbon chain, and a composition-dependent electrostati<br/><br>
 interaction between charged amino acids and the surfactant headgroup. The net<br/><br>
	force is attractive up to a ratio of surfactant to protein of 8, after<br/><br>
	which it becomes increasingly repulsive. The gel phase occurs as a<br/><br>
	compromise between the attractive hydrophobic interaction and the<br/><br>
	relatively weak electrostatic repulsion.},
  author       = {Stenstam, Anna and Topgaard, Daniel and Wennerström, Håkan},
  issn         = {1520-5207},
  language     = {eng},
  number       = {32},
  pages        = {7987--7992},
  publisher    = {The American Chemical Society},
  series       = {The Journal of Physical Chemistry Part B},
  title        = {Aggregation in a protein-surfactant system. The interplay between hydrophobic and electrostatic interactions},
  url          = {http://dx.doi.org/10.1021/jp0224158},
  volume       = {107},
  year         = {2003},
}