Oligo(p-phenylenevinylene)−Peptide Conjugates: Synthesis and Self-Assembly in Solution and at the Solid−Liquid Interface

Two oligo(p-phenylenevinylene)−peptide hybrid amphiphiles have been synthesized using solid- and liquid-phase strategies. The amphiliphiles are composed of a π-conjugated oligo(p-phenylenevinylene) trimer (OPV) which is coupled at either a glycinyl-alanyl-glycinyl-alanyl-glycine (GAGAG) silk-inspired β-sheet or a glycinyl-alanyl-asparagyl-prolyl-asparagy-alanyl-alanyl-glycine (GANPNAAG) β-turn forming oligopeptide sequence. The solid-phase strategy enables one to use longer peptides if strong acidic conditions are avoided, whereas the solution-phase coupling gives better yields. The study of the two-dimensional (2D) self-assembly of OPV−GAGAG by scanning tunneling microscopy (STM) at the submolecular level demonstrated the formation of bilayers in which the molecules are lying antiparallel in a β-sheet conformation. In the case of OPV−GANPNAAG self-assembled monolayers could not be observed. Absorption, fluorescence, and circular dichroism studies showed that OPV−GAGAG and OPV−GANPNAAG are aggregated in a variety of organic solvents. In water cryogenic temperature transmission electron microscopy (cryo-TEM), atomic force microscopy (AFM), light scattering, and optical studies reveal that self-assembled nanofibers are formed in which the helical organization of the OPV segments is dictated by the peptide sequence.