Biological Identification of Peptides that Specifically Bind to Poly(phenylene vinylene) Surfaces: Recognition of the Branched or Linear Structure of the Conjugated Polymer

Peptides that bind to poly(phenylene vinylene) (PPV) were identified by the phage display method. Aromatic amino acids were enriched in these peptide sequences, suggesting that a π−π interaction is the key interaction between the peptides and PPV. The surface plasmon resonance (SPR) experiments using chemically synthesized peptides demonstrated that the Hyp01 peptide, with the sequence His-Thr-Asp-Trp-Arg-Leu-Gly-Thr-Trp-His-His-Ser, showed an affinity constant (7.7 × 10<sup>5</sup> M<sup>−1</sup>) for the target, hyperbranched PPV (hypPPV) film. This value is 15-fold greater than its affinity for linear PPV (linPPV). In contrast, the peptide screened for linPPV (Lin01) showed the reverse specificity for linPPV. These results suggested that the Hyp01 and Lin01 peptides selectively recognized the linear or branched structure of PPVs. The Ala-scanning experiment, circular dichroism (CD) spectrometry, and molecular modeling of the Hyp01 peptide indicated that adequate location of two Trp residues by forming the polyproline type II (P<sub>II</sub>) helical conformation allowed the peptide to specifically interact with hypPPV.