Selection of Peptide-Bismuth Bicycles Using Phage Display.

Abstract

Cysteine conjugation is widely used to constrain phage displayed peptides for the selection of cyclic peptides against specific targets. In this study, the nontoxic Bi3+ ion was used as a cysteine conjugation reagent to cross-link peptide libraries without compromising phage infectivity. We constructed a randomized 3-cysteine peptide library and cyclized it with Bi3+, followed by a selection against the maltose-binding protein as a model target. Next-generation sequencing of selection samples revealed the enrichment of peptides containing clear consensus sequences. Chemically synthesized linear and Bi3+ cyclized peptides were used for affinity validation. The cyclized peptide showed a hundred-fold better affinity (0.31 ± 0.04 μM) than the linear form (39 ± 6 μM). Overall, our study proved the feasibility of developing Bi3+ constrained bicyclic peptides against a specific target using phage display, which would potentially accelerate the development of new peptide-bismuth bicycles for therapeutic or diagnostic applications.