Cyclic peptides as scaffold for oriented functional groups on surface

Surface modification with Disperse Red-1 (DR-1), which is a chromophore for optical second harmonic generation (SHG), was carried out by using cyclic peptides as a scaffold for DR-1. Cyclic dipeptide and cyclic octapeptide having DR-1 at the side chain were synthesized. The surfaces of quartz or glass substrates were covered with the cyclic peptides by transfer of the monolayer spread on water subphase (Langmuir–Blodgett film) or by cast of thin film. The planar cyclic skeleton lay down on the surface with face-to-face orientation. The orientation of the DR-1 unit in the side chain of the cyclic peptides was evaluated by polarization modulation Fourier transform infrared reflection–absorption spectroscopy and SHG measurement. The results indicate that the DR-1 unit was fixed on the surface with anisotropic orientation due to the scaffold ability of the cyclic peptides.