Macromolecules such as proteins, polysaccharides, and nucleic acids often differ only in their physicochemical properties within the individual groups, and their isolation on the basis of these differences, e.g., by ion exchange chromatography, gel filtration, or electrophoresis, is therefore difficult and time consuming. Consequently, their activity decreases considerably during the isolation procedure owing to denaturation, cleavage, enzymatic hydrolysis, and so forth. One of the most characteristic properties of these biologically active macromolecules is their ability to bind other molecules reversibly. For example, active and regulatory sites of enzymes form complexes with substrates, inhibitors, cofactors, or effectors; antibodies bind antigens against which they were prepared, etc. The formation of these biospecific, dissociable complexes of biological macromolecules serves as a basis for bioaffinity chromatography.