Simultaneous Control of pH and Ionic Strength during Interfacial Rheology of 尾-Lactoglobulin Fibrils Adsorbed at Liquid/Liquid Interfaces

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• 作者：Patrick A. R眉hs ; Nathalie Scheuble ; Erich J. Windhab ; Raffaele Mezzenga ; Peter Fischer
• 刊名：Langmuir
• 出版年：2012
• 出版时间：August 28, 2012
• 年：2012
• 卷：28
• 期：34
• 页码：12536-12543
• 全文大小：490K
• 年卷期：v.28,no.34(August 28, 2012)
• ISSN：1520-5827

文摘

Proteins can aggregate as amyloid fibrils under denaturing and destabilizing conditions such as low pH (2) and high temperature (90 掳C). Fibrils of 尾-lactoglobulin are surface active and form adsorption layers at fluid鈥揻luid interfaces. In this study, 尾-lactoglobulin fibrils were adsorbed at the oil鈥搘ater interface at pH 2. A shear rheometer with a bicone geometry set up was modified to allow subphase exchange without disrupting the interface, enabling the investigation of rheological properties after adsorption of the fibrils, as a function of time, different pH, and ionic strength conditions. It is shown that an increase in pH (2 to 6) leads to an increase of both the interfacial storage and loss moduli. At the isoelectric point (pH 5鈥?) of 尾-lactoglobulin fibrils, the maximum storage and loss moduli are reached. Beyond the isoelectric point, by further increasing the pH, a decrease in viscoelastic properties can be observed. Amplitude sweeps at different pH reveal a weak strain overshoot around the isoelectric point. With increasing ionic strength, the moduli increase without a strain overshoot. The method developed in this study allows in situ subphase exchange during interfacial rheological measurements and the investigation of interfacial ordering.