PROTEIN PARTITION AND ION COPARTITION IN AQUEOUS-APOLAR 2-LIQUID-PHASE SYSTEMS

A thermodynamic treatment of protein partitioning in an aqueous-organic two-phase system is presented. The phenomenological analysis interprets the copartitioning of electrolytes. The analysis is supported by experimental results. Solubilization of cytochrome c in trioctylmethylammonium chloride reverse micelles is accompanied by the expulsion and inclusion of electrolytes (HCl) for pH levels below, and respectively above the pH of maximal solubilization. Maximal solubilization occurs when no copartitioning is required. The observations are discussed in terms of the change in Donnan exclusion due to double-layer overlap. © 1990 Steinkopff.