Lysozyme effect on oleic acid/oleate vesicles.

We have analysed by means of turbidimetric, dynamic light scattering (DLS), and fluorimetric techniques the effect of lysozyme on negatively charged oleic acid/oleate vesicles. The addition of lysozyme brings about a decrease in optical density of the vesicle population, which finally results in a size distribution of oleate vesicles shifted toward smaller mean diameters. On the contrary, (a) when phosphatidylserine vesicles were used, lysozyme induces an increase of turbidity and a shift toward larger vesicle sizes; and (b) the addition of histone H1 or poly-L-lysine produces an aggregative behavior both in oleate and in phosphatidylserine vesicles. Experiments carried out with calcein-containing vesicles indicate that the observed changes in the lysozyme/oleate system occur with partial leakage of the vesicle content. All this is taken to suggest that the interaction between lysozyme and oleate vesicles is of quite specific nature, and certainly not just due to electrostatic interactions.