PROTEIN PARTITIONING IN WEAKLY CHARGED POLYMER-SURFACTANT AQUEOUS 2-PHASE SYSTEMS

The study includes partitioning of proteins in aqueous two-phase syste ms consisting of the polymer dextran and the non-ionic surfactant C(12 )E(5) (pentaethylene glycol mono-n-dodecyl ether). In this system a mi celle-enriched phase is in equilibrium with a polymer-enriched phase. Charges can be introduced into the micelles by the addition of charged surfactants. The charge of the mixed micelles is easily varied in sig n and magnitude independently of pH, by the addition of different amou nts of negatively charged surfactant, sodium dodecyl sulphate (SDS), o r positively charged surfactant dodecyl trimethyl ammonium chloride (D oTAC). A series of water-soluble model proteins (BSA, beta-lactoglobul in, myoglobin, cytochrome c and lysozyme), with different net charges at pH 7.1, have been partitioned in non-charged systems and in systems with charged mixed micelles or charged polymer (dextran sulphate). It is shown that partition coefficients for charged proteins in dextran- C(12)E(5) systems can be strongly affected by addition of charged surf actants (SDS, DoTAC) or polymer (dextran sulphate) and that the effect s are directly correlated to protein net charge.