Biphasic systems formed by mixing of two polymers or a polymer and a salt in water can be used for separation of cells, membranes, viruses, proteins, nucleic acids, and other biomolecules. The partitioning between the two phases is dependent on the surface properties and conformation of the materials, and also on the composition of the two-phase system. The mechanism of partitioning is, however, complex and not easily predicted. Aqueous two-phase systems (ATPS) have proven to be a useful tool for analysis of biomolecular and cellular surfaces and their interactions, fractionation of cell populations, product recovery in biotechnology, and so forth. Potential for environmental remediation has also been suggested. Because ATPS are easily scalable and are also able to hold high biomass load in comparison with other separation techniques, the application that has attracted most interest so far has been the large-scale recovery of proteins from crude feedstocks. As chemicals constitute the major cost factor for large-scale systems, use of easily recyclable phase components and the phase systems generated by a single-phase chemical in water are being studied.

Aqueous two-phase systems. A general overview.

Liquid–liquid phase transitions in complex mixtures of proteins and other molecules produce crowded compartments supporting in vitro transcription and translation. We developed a method based on picoliter water-in-oil droplets to induce coacervation in Escherichia coli cell lysate and follow gene expression under crowded and noncrowded conditions. Coacervation creates an artificial cell-like environment in which the rate of mRNA production is increased significantly. Fits to the measured transcription rates show a two orders of magnitude larger binding constant between DNA and T7 RNA polymerase, and five to six times larger rate constant for transcription in crowded environments, strikingly similar to in vivo rates. The effect of crowding on interactions and kinetics of the fundamental machinery of gene expression has a direct impact on our understanding of biochemical networks in vivo. Moreover, our results show the intrinsic potential of cellular components to facilitate macromolecular organization into membrane-free compartments by phase separation.

https://www.pnas.org/content/pnas/110/29/11692.full.pdf

Enhanced transcription rates in membrane-free protocells formed by coacervation of cell lysate

Effect of additives on the micellization of PEO/PPO/PEO block copolymer F127 in aqueous solution

Two-phase systems can be exploited in separation science for the extraction/purification of desired biomolecules. This article reviews recent experimental work on the use of aqueous two-phase polymer systems, two-phase aqueous micellar systems and reversed micellar systems for the extraction/purification of biomolecules. The experimental partitioning behavior of different biomolecules is reviewed and new results with nisin and lipopolysaccharides are presented. An extensive description of each system is presented, based on the biomolecules behavior and the tools employed to improve their extraction and purification. Copyright © 2007 Society of Chemical Industry

https://onlinelibrary.wiley.com/doi/pdf/10.1002/jctb.1794

Liquid–liquid extraction of biomolecules: an overview and update of the main techniques

The salting-out effect and phase separation in aqueous solutions of electrolytes and poly(ethylene glycol)

Diagramme de phase des systemes obtenus avec differents sels (formate, succinate, tartrate, citrate, phosphate, carbonate, sulfate et silicate de sodium, etc.)

E. D. Goddard

Papers

Aqueous biphase formation in polyethylene oxide-inorganic salt systems