Study of the interactions between lysozyme and a fully-fluorinated surfactant in aqueous solution at different surfactant-protein ratios

The interactions of a fluorinated surfactant, sodium perfluorooctanoate, with lysozyme, have been investigated by a combination of UV absorbance. electrical conductivity and dynamic light scattering to detect and to characterize the conformational transitions of lysozyme. By using difference spectroscopy, the transition was followed as a function of surfactant concentration, and the data were analyzed to obtain the Gibbs energy of the transition in water (DeltaG(w)degrees) and in a hydrophobic environment (DeltaG(h)degrees) for saturated protein-surfactant complexes. Electrical conductivity was used to determine the critical micelle concentration of the surfactant in the presence of different lysozyme concentration. From these results, the average number of surfactant monomer per protein molecule was calculated. Finally, dynamic light scattering show that only changes in the secondary structure of the protein can be observed. (C) 2003 Elsevier B.V. All rights reserved.