α-Helically constrained phage display library

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Abstract
The library described here is a collection of phages with six degenerate codons in gene VIII, specifying amino acids 12, 13, 15–17 and 19 of the major coat protein. The randomized positions are surface exposed in the wild-type protein and thus might be expected to tolerate a great diversity of side chains without compromising phage viability. In agreement with this supposition, the new library showed great diversity of amino acids at the randomized positions and diversity did not diminish noticeably during repeated subculture. Despite their diversity, however, the randomized positions should be strongly constrained conformationally because they lie in an extended α-helical portion of the protein, stabilized by numerous inter- and intra-subunit contacts—a presupposition corroborated by circular dichroism spectroscopy of many library members. To reflect this conformational homogeneity and the fact that random amino acids subtend a major fraction of the surface `landscape’ of the particle, we call the new construct an alpha landscape library. It can be used as a source of α-helical ligands and substitute antibodies.