Solid-Phase Capture of Phage for Combinatorial Chemical Diversification of Peptide Libraries

The chemical and structural diversity of peptide phage or mRNA-display libraries can be expanded by chemical modification, such as with cyclization reagents or by incorporation of unnatural amino acids, but the number of different non-natural building blocks introduced has been modest so far. To expand the chemical diversity in peptide display libraries, we developed a strategy for efficient parallel chemical diversification of phage display libraries based on capturing phage on a solid support via a polyhistidine tag and chemical modification. We applied chemically diverse building blocks in a 96-well format that allowed high-throughput experimentation, including parallel phage panning. Selections against the oncology target MCL-1 identified binders containing unnatural building blocks that were important for binding, such as thienylpyridine. This demonstrated the effectiveness of the approach and emphasized the advantages of an increased chemical diversity. This strategy may be particularly attractive for generating short peptide-based ligands, where the number of combinations based on proteinaceous amino acids is limited, for generating membrane-permeable peptides required for oral application or intracellular targeting.