Ion-specific weak adsorption of salts and water/octanol transfer free energy of a model amphiphilic hexapeptide

Christophe Déjugnat 1 Jean-François Dufrêche 2 Thomas Zemb 1
1 LTSM - Tri ionique par les Systèmes Moléculaires auto-assemblés
ICSM - UMR 5257 - Institut de Chimie Séparative de Marcoule
2 LMCT - Modélisation Mésoscopique et Chimie Théorique
ICSM - UMR 5257 - Institut de Chimie Séparative de Marcoule
Abstract : An amphiphilic hexapeptide has been used as a model to quantify how specific ion effects induced by addition of four salts tune the hydrophilic/hydrophobic balance and induce temperature-dependant coacervate formation from aqueous solution. The hexapeptide chosen is present as a dimer with low transfer energy from water to octanol. Taking sodium chloride as the reference state in the Hofmeister scale, we identify water activity effects and therefore measure the free energy of transfer from water to octanol and separately the free energy associated to the adsorption of chaotropic ions or the desorption of kosmotropic ions for the same amphiphilic peptide. These effects have the same order of magnitude: therefore, both energies of solvation as well as transfer into octanol strongly depend on the nature of the electrolytes used to formulate any buffer. Model peptides could be used on separation processes based on criteria linked to “Hofmeister” but different from volume and valency.
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https://hal.umontpellier.fr/hal-02002588
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Soumis le : jeudi 31 janvier 2019 - 17:47:36
Dernière modification le : mardi 19 novembre 2019 - 14:08:01

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Christophe Déjugnat, Jean-François Dufrêche, Thomas Zemb. Ion-specific weak adsorption of salts and water/octanol transfer free energy of a model amphiphilic hexapeptide. Physical Chemistry Chemical Physics, Royal Society of Chemistry, 2011, 13 (15), pp.6914. ⟨10.1039/c0cp01750g⟩. ⟨hal-02002588⟩

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