Separation in Solution

Abstract

The methods described in Chapters 3 and 4 involve phase changes. The proteins pass from liquid phase (i.e., dissolved) to solid (precipitated or adsorbed) and back again. Not all proteins withstand the stresses occurring in these methods; gentler methods in which the proteins remain in solution at all times are available. One of these, gel filtration, is one of the principal techniques used in purifying enzymes and other proteins, and it will be considered in detail. Other methods, grouped together as electrophoretic techniques, are less widely used, for reasons which will be outlined in sections 5.2 and 5.3. A third, little-used method of separation in solution involves phase partitioning where proteins may move from one liquid phase into another (section 5.4). As a general technique, separation in solution is an important procedure both in research and industrial enzyme and protein purification.