Application of the aqueous two-phase systems of ethylene and propylene oxide copolymer-maltodextrin for protein purification

Partitioning features of bovine trypsin and α-chymotrypsin in polyethyleneglycol-sodium citrate aqueous two-phase systems

“…In this way, the high K p values observed for TRP or ChTRP (>1) in PEG600/citrate ATPSs might be explained by assuming a strong interaction between the positively-charged amino acid residues (pH < pI) or the exposed tryptophans in both proteins [17] and the ether groups in the PEG molecule. A similar mechanism was postulated for PEG600 and other small proteins such as lysozyme [18]. According to Diamond and Hsu [19] the slope of the plot ln K p versus w PEG (difference in the concentrations of PEG between the coexisting phases) is a function of the resulting interaction parameters between phase components such as protein-water, polymer-water and protein-polymer interactions.…”

Partition features and renaturation enhancement of chymosin in aqueous two-phase systems

“…This dual effect of the salt has been observed for the partition of other proteins [7]. At low salt concentration (between 0 and 0.2 M), the salt modifies the electrical potential ( Ψ ) between the phases, it depends on the cation and anion affinity to the phases, and K will be modified according to the known state equation for the protein partition:…”

“…The systems PEG/Pi were prepared with distilled water according to Ramsch et al [6]. The system PEO-MDX was prepared in 50 mM pH 6.5 phosphate buffer according to binodial diagram previously obtained by Bolognese et al [7]. The pH 10.5, 8 M deionized urea PEG/Pi and PEO/Pi systems were prepared with the previous stock solutions but in deionized urea 8 M, pH 10.5 glycin 50 mM buffer.…”

Protein-flexible chain polymer interactions to explain protein partition in aqueous two-phase systems and the protein–polyelectrolyte complex formation

“…PEO forms aqueous two-phase systems, therefore liquid-liquid extraction can be used [20], while PVS and PAA have been used in the precipitation of proteins [21] by formation of non-soluble polyelectrolyte-protein complexes, being a coulombic mechanism of interaction.…”