1. Affinity chromatography: A chromatographic technique in which molecules are separated by special and reversible affinity binding with their ligands.

Principle: Affinity molecules with special structures were made into solid adsorbents and placed in chromatographic columns. When the protein mixture to be separated passes through the chromatographic column, protein with affinity for adsorbent will be adsorbed and retained in the chromatographic column. Protein without affinity will flow out directly because it is not adsorbed, so it will be separated from protein. Then, the bound protein was eluted by selecting suitable eluent and changing the binding conditions.

2. Gel filtration: a chromatographic method in which a gel with a certain pore size is used as chromatographic medium (such as dextran gel, agarose gel and polyacrylamide gel). ), and the separated substances diffuse into the gel pores at different speeds according to the different molecular sizes and shapes, thus passing through the chromatographic column at different speeds.

Principle: Gel filtration chromatography, also known as exclusion chromatography or molecular sieve method, mainly separates and purifies according to the size and shape of protein, that is, the quality of protein. The packing in the chromatographic column is some inert porous reticular substances, mostly cross-linked polysaccharides (such as dextran or agarose). The substances in protein mixture are separated according to different molecular sizes. It is also called molecular exclusion chromatography. It is a chromatographic technique that uses porous gel beads as matrix to separate protein or other molecular mixtures according to the molecular size. Generally, macromolecules flow out first, and small molecules flow out later.

3. Polyacrylamide gel electrophoresis: used to separate protein and oligosaccharide nucleotides.

Principle of action polyacrylamide gel electrophoresis is a network structure with molecular sieve effect. It has two forms: (1) non-denaturing polyacrylamide gel. In the process of electrophoresis, protein can remain intact and gradually separate according to the molecular weight of protein, the shape of protein and the amount of attached charge.

4. Salting-out: The phenomenon that increasing the concentration of neutral salt will reduce the solubility of protein, gas and uncharged molecules. This is a common method for the separation and purification of protein. The most commonly used neutral salts are ammonium sulfate, sodium sulfate and sodium chloride.