Adsorption Behavior of Hydrophobin and Hydrophobin/Surfactant Mixtures at the Air鈥揥ater Interface

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• 作者：Xiaoli L. Zhang ; Jeffrey Penfold ; Robert K. Thomas ; Ian M. Tucker ; Jordan T. Petkov ; Julian Bent ; Andrew Cox ; Richard A. Campbell
• 刊名：Langmuir
• 出版年：2011
• 出版时间：September 20, 2011
• 年：2011
• 卷：27
• 期：18
• 页码：11316-11323
• 全文大小：877K
• 年卷期：v.27,no.18(September 20, 2011)
• ISSN：1520-5827

文摘

The adsorption of the surface-active protein hydrophobin, HFBII, and the competitive adsorption of HFBII with the cationic, anionic, and nonionic surfactants hexadecyltrimethylammonium bromide, CTAB, sodium dodecyl sulfate, SDS, and hexaethylene monododecyl ether, C₁₂E₆, has been studied using neutron reflectivity, NR. HFBII adsorbs strongly at the air鈥搘ater interface to form a dense monolayer 30 脜 thick, with a mean area per molecule of 400 脜² and a volume fraction of 0.7, for concentrations greater than 0.01 g/L, and the adsorption is independent of the solution pH. In competition with the conventional surfactants CTAB, SDS, and C₁₂E₆ at pH 7, the HFBII adsorption totally dominates the surface for surfactant concentrations less than the critical micellar concentration, cmc. Above the cmc of the conventional surfactants, HFBII is displaced by the surfactant (CTAB, SDS, or C₁₂E₆). For C₁₂E₆ this displacement is only partial, and some HFBII remains at the surface for concentrations greater than the C₁₂E₆ cmc. At low pH (pH 3) the patterns of adsorption for HFBII/SDS and HFBII/C₁₂E₆ are different. At concentrations just below the surfactant cmc there is now mixed HFBII/surfactant adsorption for both SDS and C₁₂E₆. For the HFBII/SDS mixture the structure of the adsorbed layer is more complex in the region immediately below the SDS cmc, resulting from the HFBII/SDS complex formation at the interface.