Adsorption of β-Lactoglobulin on Spherical Polyelectrolyte Brushes: Direct Proof of Counterion Release by Isothermal Titration Calorimetry

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• 作者：Katja Henzler ; Bjrn Haupt ; Karlheinz Lauterbach ; Alexander Wittemann ; Oleg Borisov ; Matthias Ballauff
• 刊名：Journal of the American Chemical Society
• 出版年：2010
• 出版时间：March 10, 2010
• 年：2010
• 卷：132
• 期：9
• 页码：3159-3163
• 全文大小：189K
• 年卷期：v.132,no.9(March 10, 2010)
• ISSN：1520-5126

文摘

The thermodynamics and the driving forces of the adsorption of β-lactoglobulin on spherical polyelectrolyte brushes (SPB) are investigated by isothermal titration calorimetry (ITC). The SPB consist of a polystyrene core onto which long chains of poly(styrene sulfonate) are grafted. Adsorption isotherms are obtained from measurements by ITC. The analysis by ITC shows clearly that the adsorption process is solely driven by entropy while ΔH > 0. This finding is in accordance with the proposed mechanism of counterion release: Patches of positive charges on the surface of the proteins become multivalent counterions of the polyelectrolyte chains, thereby releasing the counterions of the protein and the polyelectrolyte. A simple statistical-mechanical model fully corroborates the proposed mechanism. The present analysis shows clearly the fundamental importance of counterion release for protein adsorption on charged interfaces and charged polymeric layers.