been reported to induce strong attractive interactions be-The electrostatic interactions for a particle-containing shell-andtween droplets and cause a decrease in the percolation core system are studied on the basis of the Poisson-Boltzmann threshold as compared to the unfilled reverse micelles (12equation under the Debye-Hu ¨ckel approximation. Analytical ex-15). It is found that the electrostatic interactions between pressions for the electrostatic potential distributions are obtained the surfactant interface and the protein play an important for arbitrary charge distributions on both the shell and the particle role in both the intermicellar interactions and the percolation surfaces. On the basis of a charging process, the electrostatic free onset (8, 15). Structural studies by SAXS showed that mienergy of the system is also obtained. The free energy consists of croemulsions filled by the native and the chemically modithe self-energy and the interaction energy. The self-energy depends fied cytochrome c, differing by their net charge (/8, 03, only on the surface charge density of the particle or the shell itself.
The interaction energy arises from the interactions between the and 012), in AOT (anionic surfactant) reverse micelles same modes on both surfaces when the particle is in concentric (15) behaved quite differently in terms of their intermicellar position with the outer shell. In general, the self-energy dominates potentials. It has been observed that for cytochrome c( 03), over the interaction energy. The effects of surface charge distributhe intermicellar potential remains unchanged compared to tions of the inner particle on the electrostatic free energy of the the unfilled reverse micelles. However, a strong increase of systems are explored. The electrostatic free energy associated with the potential due to the addition of cytochrome c(/8) and the net charge effect in the aqueous core is also investigated. It is a strong decrease of the potential induced by the addition found that when the particle and the shell possess charges of the of the negatively charged cytochrome c(012) are revealed. same sign, the free energy associated with net charge effect is Using different spectroscopic techniques, Vos et al. (8) have lower than that of the opposite sign. The contribution due to net also found that a strong electrostatic interaction between charge effect can be neglected when enough electrolytes are added protein and AOT interface can be observed though the interinto the aqueous core.