Protein Partitioning in Aqueous Two‐Phase Systems Composed of a pH‐Responsive Copolymer and Poly(ethylene glycol)

Abstract

The effect of pH and salt concentration on the partitioning behavior of bovine serum albumin (BSA) and cytochrome c in an aqueous two-phase polymer system containing a novel pH-responsive copolymer that mimics the structure of proteins and poly(ethylene glycol) (PEG) was investigated. The two-phase system has low viscosity. Depending on pH and salt concentration, the cytochrome c was found to preferentially partition into the pH-responsive copolymer-rich (bottom) phase under all conditions of pH and salt concentrations considered in the study. This was caused by the attraction between the positively charged protein and negatively charged copolymer. BSA partitioning showed a more complex behavior and partitioned either to the PEG phase or copolymer phase depending on the pH and ionic strength. Extremely high partitioning levels (partition coefficient of 0.004) and very high separation ratios of the two proteins (up to 48) were recorded in the new systems. This was attributed to strong electrostatic interactions between the proteins and the charged copolymer.

Phase Diagrams of the Aqueous Two-Phase Systems of Poly(ethylene glycol)/Sodium Polyacrylate/Salts

“…Persson et al have also studied the use of cationic polymers for protein partitioning [13]. Waziri et al showed that PEG can form a two-phase system with relatively low polymer content with an almost neutral ampholyte polydiallyamino-ethanoate-dimethyl-sulfoxide (PAEDS) [14]. For these cited examples the polymers are still non-commercial and have a complex composition which is a strong drawback for developing a reliable bioseparation process.…”

Application of aqueous mixtures of polypropylene glycol or polyethylene glycol with salts in proteomic analysis

“…The attractiveness of the technique is its biocompatibility, *Corresponding author. E-mail: a-salabat@araku.ac.ir simplicity, amenability to linear scale-up, potential for continuous operation and wide range of hydrophobicity differences between the two-phase systems [11][12][13].…”

Aqueous two-phase poly(ethylene glycol)–poly(acrylic acid) system for protein partitioning: Influence of molecular weight, pH and temperature

“…The general properties of the aqueous two-phase system have been studied by several researchers [1][2][3][15][16][17][18][19]. The partitioning of biological materials is a result of Van der Waals and ionic interactions of the biomolecules with the surrounding phase.…”