Protein-solvent interactions, gel

Aqueous solutions of proteins and polysaccharides may exhibit phase separation at finite concentrations. Two types of behavior may be recognized, namely coacer-vation and incompatibility. Complex coacervation involves spontaneous separation into solvent-rich and solvent-depleted phases. The latter contains the protein-poly-saccharide complex that is caused by nonspecific attractive protein-polysaccharide interaction, e.g. opposite charge interaction. Incompatibility is caused by spontaneous separation into two solvent-rich phases, one composed of predominantly protein and the other predominantly polysaccharide. Depending on the interactions, a gel formed from a mixture of two biopolymers may contain a coupled network, an interpene-... 

Like other GFC matrices, including TSK-GEL SW and TSK-GEL PW packings, and dextran and agarose gels, Toyopearl HW resins exhibit some ionic and hydrophobic interaction with samples. The hydrophobic properties of Toyopearl HW resins, however, can be utilized more effectively for improved protein purifications because, unlike numerous other GFC packing materials, Toyopearl HW resins can be used with high levels of organic solvent (38). 

The colloidal particles can be crystalline or constitnte an amorphons agglomeration of individual molecnles. The definition also includes nonaggregated large macromolecules such as proteins. An arbitrary distinction is made between hydrophobic colloids (sols) and hydrophilic colloids (gels), which depends on the degree and type of interaction with the aqneons solvent. 

Protein separation by hydrophobic interaction chromatography is dependent upon interactions between the protein itself, the gel matrix and the surrounding aqueous solvent. Increasing the ionic strength of a solution by the addition of a neutral salt (e.g. ammonium sulfate or sodium chloride) increases the hydrophobicity of protein molecules. This may be explained (somewhat simplistically) on the basis that the hydration of salt ions in solution results in an ordered shell of water molecules forming around each ion. This attracts water molecules away from protein molecules, which in turn helps to unmask hydrophobic domains on the surface of the protein. 

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