The Hexa His tag peptide is a short peptide composed of six consecutive histidine residues and also serves as a purification tag for fusion proteins. The Hexa His tag peptide can chelate with metal ions such as nickel and cobalt. Recombinant proteins can be efficiently purified by immobilized metal ion affinity chromatography[1]. The Hexa His tag peptide is commonly used to prepare protein mimics for nanocrystals[2].
References:
[1] Schmidt TG, Koepke J, Frank R, et al. Molecular interaction between the Strep-tag affinity peptide and its cognate target, streptavidin. J Mol Biol. 1996 Feb 9;255(5):753-66.
[2] Zhou W, Baneyx F. Biofabrication of ZnS:Mn luminescent nanocrystals using histidine, hexahistidine, and His-tagged proteins: a comparison study. Biochem Eng J. 2014 Aug 15;89:28-32.