Histidine has a strong association with immobilized metal ion matrices. This is because the imidazole ring has electron donor groups that form coordination bonds with the transition metal that is immobilized. Hexahistidine tag (His-tag) consists of four to six histidines that are fused genetically. It is mainly used to purify proteins by immobilized metal-ion affinity chromatography (IMAC). His-tags are added at the amino or carboxy termini of proteins.
Storage: -20C