Cysteine-containing polyisocyanides as versatile nanoplatforms for chromophoric and bioscaffolding

The straightforward syntheses of polyisocyanides containing the alanine-cysteine motif in their side chains have been achieved. Detailed characterization of the polymers revealed a well-defined and highly stable helical conformation of the polyimine backbone responsible for the formation of rodlike structures of over one hundred nanometers. The 4 1 helix is further stabilized by β-sheet-like interactions between the peptide arms. As a result, the cysteine sulfur atoms are regularly aligned along the polymer axis, which provides a unique platform for the scaffolding of various entities by using versatile click-chemistry post-modification approaches. For instance, pyrene derivatives were introduced through thio-specific reactions involving either maleimide, iodoacetamide, or thioester groups, leading to arrays of stacked chromophores with excimerlike emission. A water-soluble cysteinerich polyisocyanide was successfully biotinylated and coupled to streptavidin