A substrate comprises a surface, and a plurality of moieties, on at least a portion of the surface. The moieties are moieties of formula:
Surf-L—Q—T,
where —T comprises a reactant ligand, and Surf- designates where the moiety attaches to the surface. The substrate can be made into a protein chip by the reaction of a reactant ligand and a fusion polypeptide, where the fusion polypeptide includes a capture polypeptide moiety which corresponds to the reactant ligand.
The present invention provides a method, comprising (a) providing a reactant ligand attached to a substrate; (b) contacting the substrate with a fusion polypeptide, said fusion polypeptide comprising a capture polypeptide fused to a display polypeptide under conditions such that said reactant ligand covalently binds to said capture polypeptide; and (c) analyzing said display polypeptide.