Determination of the Dissociation Constant for Polyvalent Receptors using ELISA: a Case of M13 Phages Displaying Troponin T-specific Peptides

Phage-derived affinity peptides have become widespread thanks to their easy selection via phage display. Interactions between a target protein and its specific peptide are similar to those between antibodies and antigens. The strength of these non-covalent complexes may be described by the dissociation constant (Kd). In this paper, protein-specific peptides are exposed on the pIII protein present in the M13 bacteriophage virion with up to 5 copies. Therefore, one phage particle can bind from one to five ligands. Here, we discuss the dependences between phage-displayed peptides and their ligands in solution using a model system based on troponin T (TnT) binding phages. Moreover, a method of calculating Kd values from ELISA experiments was developed and presented. Determined Kd values are in the picomolar range