Metal-Free Polymer-Based Affinity Medium for Selective Purification of His6-Tagged Proteins

Area of Science:

• Biochemistry
• Materials Science
• Biotechnology

Background:

• Affinity chromatography is crucial for protein purification.
• Immobilized metal ion chromatography (IMAC) is widely used for His6-tagged proteins but can have limitations.
• Development of metal-free alternatives is desirable for specific applications.

Purpose of the Study:

• To develop a metal-free synthetic hydrogel copolymer with high affinity and selectivity for His6-tagged peptides and proteins.
• To investigate the structural and chemical factors influencing His6-tag binding.
• To evaluate the performance of the synthetic copolymer as an affinity medium for protein purification.

Main Methods:

• Screening of copolymer libraries with varying charged and hydrophobic functional groups.
• Monomer selection guided by antibody-antigen complex crystal structures.
• Characterization of His6-tag binding affinity and selectivity.
• pH-dependent binding and elution studies.
• Preparation and testing of a copolymer-coated chromatographic medium for protein purification.

Main Results:

• Synthetic copolymers incorporating phenylalanine-derived monomers showed strong affinity for His6-tagged peptides and proteins.
• Aromatic and negatively charged functional groups were key for His6 affinity.
• Binding affinity was unaffected by enzyme cleavage sequences.
• His6-copolymer interactions were pH-sensitive, enabling mild protein release at pH 8.6.
• A copolymer-coated chromatographic medium successfully purified a His6-tagged protein from an E. coli expression system.

Conclusions:

• Metal-free synthetic hydrogel copolymers can effectively bind His6-tagged molecules.
• The developed copolymer offers a viable, metal-free alternative to IMAC for His6-protein purification.
• pH-sensitive binding provides a mild elution strategy for purified proteins.