SOLUBILIZATION MECHANISM OF CYTOCHROME-C IN SODIUM BIS(2-ETHYLHEXYL) SULFOSUCCINATE WATER OIL MICROEMULSION

The solubilization mechanism of cytochrome c (cytc) in a sodium bis(2-ethylhexyl) sulfosuccinate (AOT) water/oil (w/o) microemulsion (ME) phase was investigated. First, the interaction between cytc and AOT molecules was studied by observing the precipitation behavior of cytc in the aqueous phase. Second, both the solubilization-deposition behavior of cytc in the brine/AOT/n-heptane system and the solubilization of cytc under the nonuniform water distribution in the ME phase were measured. Interactions of two types played an important role in the AOT adsorption on the surface of a cytc molecule; the electrostatic interaction, making the protein surface hydrophobic (type 1), and the hydrophobic interaction, making the protein surface hydrophilic (type 2). Cytc is solubilized in the interfacial zone of the ME droplet as an amphiphilic molecule decorated with AOT. The most important factor for the cytc extraction to the ME phase is the transformation of native hydrophilic cytc into amphiphilic cytc due to the adsorption of AOT. The perturbatioin of the original ME structure is weak when the water-to-surfactant mole ratio is relatively large.