Use of phage display methods to identify heptapeptide sequences for use as affinity purification 'tags' with novel chelating ligands in immobilized metal ion affinity chromatography

This study describes the screening of a peptide phage display library for amino acid sequences that bind with different affinities to a novel class of chelating ligands complexed with Ni2+ ions. These chelating ligands are based on the 1,4,7-triazacyclononane (TACN) structure and have been chosen to allow enhanced efficiency in protein capture and decreased propensity for metal ion leakage in the immobilized metal ion affinity chromatographic (IMAC) purification of recombinant proteins. Utilising high stringency screening conditions, various peptide sequences containing multiple histidine, tryptophan, and/or tyrosine residues were identified amongst the different phage peptide sequences isolated. The structures, and particularly the conserved locations of these key amino acid residues within the selected heptapeptides, form a basis to design specific peptide tags for use with these novel TACN ligands as a new mode of IMAC purification of recombinant proteins.