Modified PNAs

Peptide nucleic acids are a new class of DNA analogues in which charged sugar-phosphate backbone of DNA is replaced by a neutral and achiral polyamide backbone. The monomeric unit consists of N-(2-aminoethyl) glycine units to which nucleobases are attached through a conformationally rigid, tertiary acetamide linker group. The design and facile synthesis of sterically constrained new analogs of PNA having gem-dimethyl substitutions on glycine is presented. They show a higher binding to DNA relative to that with isosequential RNA. This may be a structural consequence of sterically rigid gem-dimethyl group, imposing a pre-organized conformation favorable for complex formation with cDNA. In this regard, gem-dimethyl functionality need to be explored more by introducing in aminoethyl segment or aminoethyl and glycine, both segments. Also, significant stabilization of DNA:PNA hybrids occurs upon complexation with gold nanoparticles. It is shown here that the non-thiolic polyanionic DNA can act as a template for organizing lysine capped cationic gold nanoparticles into linear superstructures. These types of assemblies may have potential for creating nanowires and lithographic circuits.