Bioselective Separations

Highly specific interactions between complex molecules are at the heart of the activity and regulation of biological systems. This specificity results from the complementary 3-dimensional structures and surface properties of interacting species. The binding of enzymes with substrates, cofactors, inhibitors and allosteric effectors are all governed by structural complementarity, as are the interactions of antibodies and antigens, hormones and receptors, etc. Such specificity can also be used to achieve highly selective bioseparations. The most common form of this is affinity chromatography in which one species (the affinity ligand) is immobilized on a chromatography matrix in order to selectively bind a target molecule. Figure 5 shows a schematic representation of an affinity separation. The feedstock containing the target compound is applied to a column containing the affinity adsorbent. The target protein binds to the ligand while other solutes are washed through. The conditions are then changed such that the interaction between the ligand and the bound protein is disrupted and the desorbed protein is recovered in the eluent. The column can be returned to the conditions required for binding in a final regeneration step.

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