Proteins equilibrium partitioning

Biesheuvel, P. M., Stroeve, R, and P. A. Bameveld. 2004. Effect of protein adsorption and ionic strength on the equilibrium partition coefficient of ionizable macromolecules in charged nanopores. Journal of Physical Chemistry B 108 17660-17665. 

This section is misplaced in some respects. Several efforts have been put forth to separate proteins from aqueous solutions into nonionic microemulsion phases. After several years of investigation, I am convinced that the observed separations rely on an equilibrium partitioning and not on a combined extraction-stripping phenomenon. Thus, such studies should really be incorporated into the discussion in Sec. II.B.2. 

In subsequent work,Vasudevan et al. [23] conclusively showed that the hemoglobin was fully dissociated under the conditions presented in Ref. 18 and that only the heme (i.e., iron within porphyrin) was extracted into the microemulsion. Vasudevan and Wiencek [24] went on to prove that under very limiting circumstances, protein will partition into nonionic microemulsion liquid membranes. The underlying extraction mechanism is a weak electrostatic interaction between the trace impurities in the surfactant and the protein. Since the separation is based on an interaction between the surfactant (or some other interfacially active compound) and the solute, no stripping reaction is required, and the system is really an equilibrium microemulsion extraction system as described in Sec. II.B.2. 

Equilibrium dialysis s Semipermeable membrane partitions protein but not carbohydrate ligand... 

A relatively common feature of many problems involving molecular weight determination of biopolymers is that of association-dissociation equilibrium. Subunit structure of enzyme proteins is well recognized (1), and methods of dissociation of subunits to obtain monomer molecular weight are widely utilized (2). A previous paper described the application of an equilibrium gel partition method to the analysis of macromolecular association in a monomer-dimer case (3). The experimental parameters in a system utilizing the Sephadex series of gel filtra-... 

For LLE the liquid sample is mixed with a larger volume of a non-polar organic solvent to induce a partition equilibrium of the analyte between the aqueous and organic layer. Typically, the latter one contains the major fraction of analytes and is further processed for LC-MS analysis. In contrast to protein precipitation, LLE thus requires a subsequent drying step by evaporation or with a gentle stream of nitrogen... 

From a statistical thermodynamic standpoint, the description of the folding/unfolding equilibrium in proteins requires the specification of the system partition function, Q defined as the sum of the statistical weights of all the possible states of the molecule (see Freire and Biltonen, 1978a) ... 

The mitotic spindle is part of a larger intracellular skeleton (cytoskele-ton) that is essential for the internal movements occurring in the cytoplasm of all eukaryotic cells. The mitotic spindle consists of chromatin, and a system of microtubules composed of the protein tubulin. The mitotic spindle is essential for the equal partitioning of DNA into the two daughter cells formed when a eukaryotic cell divides. Several plant-derived substances used as anticancer drugs disrupt this process by affecting the equilibrium between the polymerized and depolymerized forms of the microtubules, thereby causing cytotoxicity. 

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