Kinetics of the homogeneous exchange of ?-lactalbumine adsorbed on titanium oxide surface

✍ Scribed by Bentaleb, A. ;Ha�kel, Y. ;Voegel, J. C. ;Schaaf, P.

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 211 KB
• Volume: 40
• Category: Article
• ISSN: 0021-9304
• DOI: 10.1002/(sici)1097-4636(19980605)40:3<449::aid-jbm16>3.0.co;2-e

✦ Synopsis

The homogeneous exchange process whereby ␣lactalbumine molecules adsorbed on hydrophilic titanium oxide particles are replaced by ␣-lactalbumine molecules in solution has been investigated by means of a 125 I radiolabeling technique. ␣-lactalbumine is a compact and highly negatively charged protein, making this study complementary to previous work devoted to the general understanding of the exchange mechanisms of adsorbed proteins on solid surfaces. The isotherm of ␣-lactalbumine exhibits bimodal adsorption shape, and the exchange process whereby adsorbed proteins are replaced by new incoming ones from the bulk solution has been studied at both the upper and the lower plateau of the isotherm. In the upper plateau the exchange process was found to be of first order with respect to the bulk molecules, and the release rate constant was equal to 0.914 L. mol -1 ⅐ s -1 . This behavior is identical to what has been observed with other proteinic systems. In the lower plateau domain, in contrast, the protein release process is independent of the concentration of proteins in the bulk, but the release rates are higher than the pure desorption rates. This constitutes, to our knowledge, a behavior that never before has been observed and that remains to be explained.