Driving forces for phase separation and partitioning in aqueous two-phase systems

Johansson, Helena; Karlström, Gunnar; Tjerneld, Folke; Haynes, Charles A.

doi:10.1016/s0378-4347(97)00585-9

Cited by 199 publications

(147 citation statements)

References 30 publications

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“…The Flory-Huggins model [10] has been extensively used on reproducing both fundamental partitioning effects such as entropic repulsion [18] and more specific effects such as thermoseparation [19] and the electrochemical driving force in aqueous two-phase systems [18,20,21]. The model is based on mean-field statistical mechanical treatment of the combinatorial entropy upon mixing a polymer with a solvent in a lattice system, where the size of the lattice site unit is the same as the smallest component (usually the solvent).…”

Section: Model and Calculation Proceduresmentioning

confidence: 99%

“…The Flory-Huggins theory [18] predicts a linear dependence on the partition driving force (both enthalpic and entropic contributions) accordingly to the relationship M K  ln (16) where M is the polymerization degree of the polymer. The changes in binodal position are shown in Figure 6, where the modeled system contains a -Na 2 SO 4 ‖ type salt.…”

Section: Effect Of Polymer Sizementioning

confidence: 99%

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

2011

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Aqueous two-phase systems consisting of polyethylene glycol (PEG), sodium polyacrylate (NaPAA), and a salt have been studied. The effects of the polymer size, salt type (NaCl, Na 2 SO 4 , sodium adipate and sodium azelate) and salt concentrations on the position of the binodal curve were investigated. The investigated PEG molecules had a molar mass of 2,000 to 8,000 g/mol, while that of NaPAA was 8,000 g/mol. Experimental phase diagrams, and tie lines and calculated phase diagrams, based on Flory-Huggins theory of polymer solutions are presented. Due to strong enthalpic and entropic balancing forces, the hydrophobicity of the added salt has a strong influence on the position of the binodal, which could be reproduced by model calculations.

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Section: Model and Calculation Proceduresmentioning

confidence: 99%

Section: Effect Of Polymer Sizementioning

confidence: 99%

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

2011

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“…According to an thermodynamic approach developed by Johansson [53], a high PEG MW is leading to a protein exclusion from the top phase driven by an entropically unfavorable term in the absence of enthalpic effects [54][55][56]. Hence, this exclusion or entropic effect is a driving force for protein partitioning toward the bottom phase, which is increased for proteins (e.g., BSA/OVA) with self-aggregation or high MW and is more evident at increasing PEG MW [53][54][55][56].…”

Section: Factors Affecting Protein Partitioningmentioning

confidence: 99%

“…Hence, this exclusion or entropic effect is a driving force for protein partitioning toward the bottom phase, which is increased for proteins (e.g., BSA/OVA) with self-aggregation or high MW and is more evident at increasing PEG MW [53][54][55][56]. In general, entropic effects are larger for PEG-salt ATPS, when the polymer is effectively situated in the top phase, causing a lower number density of the top phase compared to the bottom phase [53,56]. On the contrary, a protein transfer in the top phase with a low PEG MW is enthalpically driven mainly due to strong protein-PEG interactions [54,55].…”

Section: Factors Affecting Protein Partitioningmentioning

confidence: 99%

“…Furthermore, the influence of salts on protein partitioning is enhanced by increasing protein net charge [53,74]. Generally, negatively charged proteins (e.g., BSA/OVA at pH 7) prefer the partitioning into the top phase, whereas positively charged proteins (e.g., α-CT/LYZ at pH 7) usually tend to partition into the bottom phase [1,6].…”

Section: Factors Affecting Protein Partitioningmentioning

confidence: 99%

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Evaluation of Driving Forces for Protein Partition in PEG-Salt Aqueous Two- Phase Systems and Optimization by Design of Experiments

Glyk¹,

Solle²,

Scheper³

et al. 2016

J Chromatogr Sep Tech

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Thermoseparating water/polymer system: A novel one-polymer aqueous two-phase system for protein purification

Johansson

Persson

Tjerneld

1999

Biotechnol. Bioeng.

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In this study we show that proteins can be partitioned and separated in a novel aqueous two‐phase system composed of only one polymer in water solution. This system represents an attractive alternative to traditional two‐phase systems which uses either two polymers (e.g., PEG/dextran) or one polymer in high‐salt concentration (e.g., PEG/salt). The polymer in the new system is a linear random copolymer composed of ethylene oxide and propylene oxide groups which has been hydrophobically modified with myristyl groups (C14H29) at both ends (HM–EOPO). This polymer thermoseparates in water, with a cloud point at 14°C. The HM–EOPO polymer forms an aqueous two‐phase system with a top phase composed of almost 100% water and a bottom phase composed of 5–9% HM–EOPO in water when separated at 17–30°C. The copolymer is self‐associating and forms micellar‐like structures with a CMC at 12 μM (0.01%). The partitioning behavior of three proteins (lysozyme, bovine serum albumin, and apolipoprotein A‐1) in water/HM‐EOPO two‐phase systems has been studied, as well as the effect of various ions, pH, and temperature on protein partitioning. The amphiphilic protein apolipoprotein A‐1 was strongly partitioned to the HM‐EOPO‐rich phase within a broad‐temperature range. The partitioning of hydrophobic proteins can be directed with addition of salt. Below the isoelectric point (pI) BSA was partitioned to the HM‐EOPO‐rich phase and above the pI to the water phase when NaClO4was added to the system. Lysozyme was directed to the HM–EOPO phase with NaClO4, and to the water phase with Na‐phosphate. The possibility to direct protein partitioning between water and copolymer phases shows that this system can be used for protein separations. This was tested on purification of apolipoprotein A‐1 from human plasma and Escherichia coli extract. Apolipoprotein A‐1 could be recovered in the HM‐EOPO‐rich phase and the majority of contaminating proteins in the water phase. By adding a new water/buffer phase at higher pH and with 100 mM NaClO4, and raising the temperature for separation, the apolipoprotein A‐1 could be back‐extracted from the HM‐EOPO phase into the new water phase. This novel system has a strong potential for use in biotechnical extractions as it uses only one polymer and can be operated at moderate temperatures and salt concentrations and furthermore, the copolymer can be recovered. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 66: 247–257, 1999.

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Driving forces for phase separation and partitioning in aqueous two-phase systems

Cited by 199 publications

References 30 publications

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

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

Evaluation of Driving Forces for Protein Partition in PEG-Salt Aqueous Two- Phase Systems and Optimization by Design of Experiments

Thermoseparating water/polymer system: A novel one-polymer aqueous two-phase system for protein purification

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