Constrained phage-displayed peptide librarie

At the time of writing this chapter, three commercial random peptide display libraries are available. Two phage Ph.D. libraries (New England Biolabs) are constituted of random 7-mers and random 12-mers fused to pill protein of the filamentous phage Ml3. The FliTrx (Invitrogen) is an E. coli display library with constrained random dodeca-peptides inserted into flagellin-thioredoxin fusion protein [10]. 

In analogy with constrained peptide libraries, several reports have described the use of small proteins, protein domains, or antibodies as scaffolds for the display of random polypeptide sequences to obtain novel binding proteins or antibodies. Koide et al. (81) used the tenth FN3 sequence, a 94-amino-acid fibronectin domain (82, 83) known to be involved in molecular recognition, as a scaffold to build a phagemid 3+3 library L7 (Fig. 10.16) where less than a copy of modified FN3 was present on each phage capsid. The 10 -member library was screened using plates coated with ubiquitin, a small protein for which native FN3 does not have any affinity. The library was made by randomizing five amino acids in positions 26-30 (BC) and five amino acids in... 

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