Study of the interaction between lysozyme and sodium octanoate in aqueous solutions

The interactions of sodium octanoate with lysozyme as a function of temperature have been investigated by a combination of UV absorbance and electrical conductivity 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 analysed to obtain the Gibbs energy of the transition in water ( Δ G w ° ) and in a hydrophobic environment ( Δ G hc ° ) for saturated protein–surfactant complexes. Electrical conductivity was used to determine changes in the protein conformation as a function of temperature. The result indicates that the presence of surfactant do not change drastically the temperature of denaturation. The critical micelle concentration of the surfactant in the presence of different lysozyme concentrations does not show visible changes, but we attribute this fact to the lack of accuracy or the technique used.