Aqueous polymer systems

FIG. 22-85 Phase diagram for a PEG/Dextran, hiphasic, aqueous-polymer system used in liquid-liquid extraction operations for protein separations. Alheiisson, Partition of Cell Particles and Macromolecules, 3d ed., Copyright 1986. Reprintedhy petTTUssion of John Wiley Sons, Inc.)... 

N. L. Abbott, D. Blankschtein, and T. A. Hatton, On protein partitioning in two-phase aqueous polymer systems, Bioseparation 1990, 1, 191-225. 

Classical LLPC using aqueous-aqueous polymer systems based on Albertsson s [9] PEG-dextran system has provided a versatile tool for the separation of proteins and nucleic acids, thus increasing the arsenal of biopolymer purification methods currently dominated by gel filtration, ion-exchange chromatography, and affinity chromatography RPC. The technique operates... 

CRE Crespo Colin, A., Cancho, S.M., Rubio, R.G., and Compostizo, A., Equation of state of aqueous polymer systems poly(propylene glycol) + water, Phys. Chem. Chem. Phys., 1, 319, 1999. 

Shibusawa, Y. Ito, Y. Protein separation with aqueous-aqueous polymer systems by two types of counter-current chromatographs. J. Chromatogr. 1991, 559, 695. 

Shibusawa, Y. Ito, Y. Protein separation with aqueous-aqueous polymer systems by two types of counter-current chromatographs. J. Chromatogr. 1991, 550, 695. Shibusawa, Y. Ito, Y. Countercurrent chromatography of proteins with polyethylene glycol-dextran polymer phase systems using type-XLLL cross-axis coil planet centrifuge. J. Liq. Chromatogr. 1992,15, 2787. 

Experimental Observations on Protein Partitioning in Two-Phase Aqueous Polymer Systems... 

Experimental observations such as those presented in Figures 1 and 2 motivated the philosophy behind our theoretical formulation (21). In particular, the correlation observed between the overall sizes of the proteins and their partitioning behavior suggested that a coarse-grained view of these systems, rather than an atom-by-atom account, may be sufficient to describe the nature of the interactions responsible for the observed partitioning behaviors of these proteins. This realization prompted our decision to pursue (21,24) a scaling account (20,32-34) of protein partitioning in two-phase aqueous polymer systems. 

Because the partitioning behavior of proteins in two-phase aqueous polymer systems reflects the relative interactions between the proteins and the two coexisting polymer solution phases, and because the independent control of the polymer concentration in only one of the two coexisting phases is not possible, we have explored an alternative experimental technique, namely, the measurement of the partitioning of proteins between an entangled PEO solution phase and an aqueous (polymer-free) phase using a diffusion cell (24). 

In view of the potentially important effect of the Donnan equilibrium of charged species in similar systems, for example, two-phase aqueous polymer systems (29,30), it is important to note that several observations indicate that this effect is not a dominant one in the diffusion cell experiments (24). Specifically, (i) relatively small differences in the partitioning of cytochrome-c were observed to accompany the substitution of different salt types, and (ii) the PEO concentration in the PEO-rich compartment is an order of magnitude smaller than that encountered in typical two-phase aqueous polymer systems. As a result, the effective electrical potential difference across the membrane was estimated to be 0.2mV or less (24). 

We have reviewed our recent theoretical and experimental studies of the physical mechanisms responsible for protein partitioning in two-phase aqueous polymer systems (21-25). It is gratifying to see that from a common physicd basis, our theoretical... 

Polyvinylpyrrolidone (PVP) (monomer-unit structure [I]) is a water-soluble synthetic polymer v ich is stable physically and ch ically in aqueous solution (1-3), and which is commercially available in a diversity of molecular weight grades (4). From these features alone, PVP has potential for use in oil-recovery and related applications similarly, its monomer unit has potential as a component of copolymers tailored for these applications (5). In any such applications, it is important not only that the polymer remains in solution under all conditions of teirperature, pressure and salinity that may be encountered, but that its solutions also retain the desired rheological behavior. Ensuring that this happens, especially with novel copolymers, requires that we have a good understandirq of the molecular interactions which occur in these aqueous polymer systems. 

The present paper reviews the effects of small-molecule solutes (i.e., cosolutes) on the aqueous solubility and conformation of PVP, both to demonstrate some of their practical consequences in the applications of this particular polymer, and also to illustrate some general features of aqueous polymer systems from the molecular interaction viewpoint. 

Incorporation of Salts into Thermotropic Aqueous Polymer Systems. The... 

It is well known that salts can strongly influence the material prqiolies of aqueous polymer systems. Ilieir addition often leads to a physical cross-linking of tile polymo chains, three-dimoisional netwcaics are built up. 

BAS Baskir, J.N., Hatton, T.A., and Suter, U.W., Thermodynamics of the separation of biomaterials in two-phase aqueous polymer systems effect of the phase-forming Xyvasrs, Macromolecules, 20, 1300, 1987. 

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