Figure 1. Schematic diagram of monomeric and heptameric targeting ligands.

(A) The cDNA of heptameric ligand consists of coding regions for a target binding domain, a flexible hinge linker, and a heptamerization domain. A 6×His-tag was introduced on the C-terminus of each molecule. The structure of the monomeric targeting ligand is similar to the heptameric ligand with the exception of the absence of the heptamerization domain. (B) Schematic representation of the monomeric and heptameric ligands;; Affibody (Z domain) structure was obtained from PDB database (PDB ID:2B89).