Recombinant Protein Purification

Recombinant protein purification is generally divided into three categories: Purification of Tagged Recombinant Proteins, Purification of Untagged Recombinant Proteins, and Purification from Inclusion Bodies through Denaturation and Refolding.

Tagged recombinant protein purification: The histidine tag (His-tag) is one of the most commonly used affinity tags for protein purification. Its purification principle is based on the imidazole groups on the histidine residues chelating with metal ions in the chromatography medium. Target proteins are then eluted through competitive binding by increasing the imidazole concentration in the buffer. One major advantage of the His-tag is its small molecular weight, which minimally affects the biological function and characteristics of the target protein. Therefore, His-tagged proteins can be directly used as antigens for immunizing animals without compromising the specificity of the resulting antibodies. We also provide purification services for a variety of other affinity tags, such as GST-tag, SUMO-tag, and MBP-tag.

Figure 1. Interaction between 6×His Tag and Adjacent Residues on Ni-NTA Resin

Untagged Recombinant Protein Purification: For recombinant proteins without purification tags, we analyze the protein properties in detail based on the client's samples and requirements. We design an integrated Purification Plan using size-exclusion chromatography, ion exchange chromatography, and hydrophobic interaction chromatography. Typically, we apply antibody affinity purification to isolate the target protein through the specific interaction between a ligand and its target. Alternatively, gel filtration may be used for separation and purification.

Inclusion Body Denaturation and Refolding Purification: For proteins expressed in the form of inclusion bodies, we perform denaturation and refolding procedures. Depending on the protein’s characteristics, denaturation can be achieved using urea, guanidine hydrochloride, detergents, or extreme pH conditions to obtain the protein in a monomeric denatured state.