Light Emitting Self-Assembled Peptide Nucleic Acids Exhibit Both Stacking and Watson-Crick Base-Pairing

Or Berger, Molecular Microbiology & Biotechnology, Tel Aviv University, Tel Aviv, Israel
Lihi Adler-Abramovich, Molecular Microbiology & Biotechnology, Tel Aviv University, Tel Aviv, Israel
Michal Levy-Sakin, Molecular Microbiology & Biotechnology, Tel Aviv University, Tel Aviv, Israel
Assaf Grunwald, Molecular Microbiology & Biotechnology, Tel Aviv University, Tel Aviv, Israel
Yael Liebes-Peer, Molecular Microbiology & Biotechnology, Tel Aviv University, Tel Aviv, Israel
Mor Bachar, Molecular Microbiology & Biotechnology, Tel Aviv University, Tel Aviv, Israel
Ludmila Buzhansky, Molecular Microbiology & Biotechnology, Tel Aviv University, Tel Aviv, Israel
Estelle Mossou, Partnership for Structural Biology, Institut Laue Langevin, Grenoble, France
Trevor Forsyth, Partnership for Structural Biology, Institut Laue Langevin, Grenoble, France
Tal Schwartz, Molecular Microbiology & Biotechnology, Tel Aviv University, Tel Aviv, Israel
Yuval Ebenstein, Molecular Microbiology & Biotechnology, Tel Aviv University, Tel Aviv, Israel
Felix Frolow, Molecular Microbiology & Biotechnology, Tel Aviv University, Tel Aviv, Israel
Linda Shimon, Department of Chemical Research Support, Weizmann Institute of Science, Rehovot, Israel
Fernando Patolsky, Molecular Microbiology & Biotechnology, Tel Aviv University, Tel Aviv, Israel
Ehud Gazit, Molecular Microbiology & Biotechnology, Tel Aviv University, Tel Aviv, Israel

The two main branches of bionanotechnology involve the self-assembly of either peptides or DNA. Peptide scaffolds offer chemical versatility, architectural flexibility, and structural complexity, but they lack the precise base-pairing and molecular recognition available with nucleic acid assemblies. Here, inspired by the ability of aromatic dipeptides to form ordered nanostructures with unique physical properties, we explore the assembly of peptide nucleic acids (PNAs), which are short DNA mimics that have an amide-backbone. All 16 combinations of the very short di-PNA building blocks were synthesised and assayed for their ability to self-associate. Only three guanine-containing di-PNAs - CG, GC and GG - could form ordered assemblies, as observed by electron microscopy, and these di-PNAs efficiently assembled into discrete architectures within a few minutes. The x-ray crystal structure of the GC di-PNA showed the occurrence of both stacking interactions and Watson-Crick base-pairing. The assemblies were also found to exhibit optical properties including voltage-dependent electroluminescence and wide-range excitation-dependent fluorescence in the visible region.