Unexpected differences in the behavior of ovotransferrin at the air–water interface at pH 6.5 and 8.0
2011
Le Floch-Fouéré, Cécile | Pezennec, Stéphane | Pézolet, Michel | Rioux-Dubé, Jean-François | Renault, Anne | Beaufils, Sylvie
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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