Unexpected differences in the behavior of ovotransferrin at the air-water interface at pH 6.5 and 8.0 |
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Authors: | Le Floch-Fouéré Cécile Pezennec Stéphane Pézolet Michel Rioux-Dubé Jean-François Renault Anne Beaufils Sylvie |
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Institution: | INRA, UMR1253 Science et Technologie du Lait et de l'?uf, F-35042 Rennes, France. |
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Abstract: | Adsorption of purified apo-ovotransferrin at the air-water interface was studied by ellipsometry, surface tension, polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS), and shear elastic constant measurements. No significant difference was observed between pH 6.5 and 8.0 as regards the final value of surface concentration and surface pressure. However at low concentration, a weak barrier to adsorption is evidenced at pH 6.5 and confirmed by PM-IRRAS measurements. At a pH where the protein net charge is negative (pH 8.0), the behavior of ovotransferrin at the air-water interface is more influenced by charge effects rather than bulk concentration effects. At this pH, the interface exhibits a low shear elastic constant and a spectral signature not usual for globular proteins. |
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