Abstract: The present invention provides novel methods for producing nucleic acid fragment libraries that express highly diverse peptides or protein domains and, in particular, methods for producing nucleic acid fragment libraries wherein the nucleic acid fragments of the libraries are derived from two or more diverse characterized genomes.

Abstract: The present invention provides a method for identifying a modulator or mediator of a biological activity, which activity includes antigenicity and or immunogenicity, said method comprising the step of: (i) producing a gene fragment expression library derived from defined nucleotide sequence fragments; and (ii) assaying the expression library for at least an amino acid sequence derived from step (i) for a biological activity wherein that activity is different from any activity the amino acid sequence may have in its native environment.

Abstract: The present invention relates provides an improved reverse n-hybrid screening method for identifying antagonists or inhibitors of biological interactions, wherein multiple reporter genes are employed to distinguish antagonists or inhibitors of one interaction from those antagonists or inhibitors of other interactions, particularly where each of said interactions involves one or more common interacting partners. A further aspect of the invention provides novel expression vectors for performing the inventive method, particularly in high throughput screens.