Figure 4. First-phase diversification of peptides, and quantification of their inhibitory activities against Plk1 PBD.

(A) First-phase N-terminal-truncated peptides generated using solid-phase peptide synthesis (SPPS). i) R-COOH, HBTU, HOBt, DIPEA, DMF, 2 h; ii) TFA/TIS/H₂O (90:5:5), 2.5 h; (B) ELISA-based Plk1 PBD-binding assay result using first-phase N-terminal-truncated peptide derivatives. Representative graphs from three independent experiments are shown (O.D., optical density).