Exchange mechanisms for sodium dodecyl sulfate micelles: high salt concentration.
J Am Chem Soc
; 126(19): 6025-34, 2004 May 19.
Article
em En
| MEDLINE
| ID: mdl-15137767
ABSTRACT
Solute exchange experiments for the pyrene-labeled triglyceride TG-Py solubilized in sodium dodecyl sulfate (SDS) micelles in the presence and absence of salt show that the "observed" rate constant k(obs) for solute exchange varies by over 6 orders of magnitude as the free sodium ion concentration [Na(+)](aq) is varied between 10 and 850 mM. There is a sharp break in the log-log plot of k(obs) versus [Na(+)](aq) in the range of [Na(+)](aq) = 200 mM, with the exchange rate showing a weaker dependence on [Na(+)](aq) above this concentration. Up to 100 mM added NaCl, this exchange takes place essentially exclusively by a micelle fission mechanism in which each submicelle carries off one of the solutes. At higher salt concentrations, a bimolecular process becomes increasingly important. This fusion process, which involves formation of a transient supermicelle followed by fission back to two normal micelles, becomes the dominant process at high salt concentrations. The fission rate appears to level off for salt concentrations above 300-400 mM. These fission and fusion processes are related in an intimate way to the changes in the size and shape of the SDS micelles with increasing salt concentration.
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Base de dados:
MEDLINE
Assunto principal:
Dodecilsulfato de Sódio
/
Tensoativos
Idioma:
En
Ano de publicação:
2004
Tipo de documento:
Article