It is a selection technique in which a library of variants of a peptide or protein is expressed on the outside of a phage virion, while the genetic material encoding each variant resides on the inside. This creates a physical linkage between each variant protein sequence and the DNA encoding it, which allows rapid partitioning based on binding affinity to a given target molecule (antibodies, enzymes, cell-surface receptors, etc.) by an in vitro selection process called panning.
(1) Sidhu, S.S. et al. (2003) Chembiochem. 4, 14-25. PMID: 125112072
(2) Azzazy, H.M. and Highsmith, W.E. (2002) Clin. Biochem. 35, 425-445. PMID: 12413604
(3) Rodi, D.J. et al. (200) Curr. Opin. Chem. Biol. 6, 92-96. PMID: 11827830