Peptides can be displayed on the surface of filamentous bacteriophages by fusion to phage coat proteins. It was recently shown that vast (108) collections of phages, each exposing a variant of the original peptide, can be constructed and utilized as a general source of peptide ligands. By panning these libraries on a target molecule linked to a solid support it is possible to select, out of the hundreds of millions of clones, those few phages that display a peptide that binds the target molecule. Searching these libraries is a powerful tool to be applied in many areas of fundamental and applied biology.
