Every protein is different, so each requires a different method. They differ in size, and the amino acid residues on the surface, both of which have important effects on a protein's interaction with chromatography resins.

Protein purification is vital for the characterization of the function, structure and interactions of the protein of interest. The purification process may separate the protein and non-protein parts of the mixture, and finally separate the desired protein from all other proteins.

The reason why a protein can be purified from thousands of protein mixtures is that different proteins have quite different physicochemical and biological properties. The difference in properties between the target protein and other proteins can be used to design a set of reasonable fractionation steps.

Proteins extracted from cells often contain impurities. To remove these impurities while maintaining the protein's biological activities, it is necessary to work out corresponding strategies according to different proteins, using different methods.