FAQ: When performing an experiment using Ph.D.™ Phage Display, the ELISA indicates that background binding to the plate is as high as binding to the target.

If panning against a polystyrene plate coated with the target (Surface-Phase Panning or Direct Target Coating), it is possible to inadvertently select peptides that specifically bind the polystyrene surface (see Adey, N. B. et al. (1995) Gene 156, 27-31). These peptides will yield identical ELISA signals in the presence and absence of target since the ELISA plate is also made of polystyrene. Such "plastic binders" are typically rich in aromatic residues (Phe, Tyr, Trp, His), which often alternate (the sequence FHWTWYW is a plastic binder discovered and characterized at NEB). Selection of plastic binders often occurs in the absence of a strong target preference for peptide sequences present in the library: other libraries may yield the desired target specific sequences. Selection of polystyrene-specific peptides can be avoided by using the Solution Phase Panning method when possible, for a given target. The phage is reacted with the target in solution, and the phage-target complexes are then captured onto beads that specifically bind the target.