1. The basic concept of the affinity phase

Affinity chromatography utilizes the specific interaction between one kind of solute molecule and another kind of molecule that is immobilized on a stationary phase. The immobilized molecules can recognize and interact with the specific molecule from a group of molecules with similar structure or properties.

The most popular theory about the mechanism of affinity chromatography is Lock-and-key theory. In this theory, the protein has some specific active site, which can interact with ligand specifically. Such a relationship is like that between the lock and the key.

Of course, beside the lock-and-key property, there must be other complex interactions between the molecules of interest and the ligand, such as electrostatic bond, hydrogen bond, hydrophobic interaction, coordinate-covalent bond and weak covalent bond. According to such complex interactions, the affinity interaction has excellent selectivity and we can utilize such properties to separate some components which have very closed structure or properties.

There are many factors, which can influence the affinity interaction: ion strength, pH value, temperature, chelating agent and inhibitor such as carbamide and guanidine hydrochloride etc. So we can change the operate conditions to  control the separate process.

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