Mechanically rigid supramolecular assemblies formed from an Fmoc-guanine conjugated peptide nucleic acid

Abstract

The variety and complexity of DNA-based structures make them attractive candidates for nanotechnology, yet insufficient stability and mechanical rigidity, compared to polyamidebased molecules, limit their application. Here, we combine the advantages of polyamide materials and the structural patterns inspired by nucleic-acids to generate a mechanically rigid fluorenylmethyloxycarbonyl (Fmoc)-guanine peptide nucleic acid (PNA) conjugate with diverse morphology and photoluminescent properties. The assembly possesses a unique atomic structure, with each guanine head of one molecule hydrogen bonded to the Fmoc carbonyl tail of another molecule, generating a non-planar cyclic quartet arrangement. This structure exhibits an average stiffness of 69.6 ± 6.8 N m −1 and Young's modulus of 17.8 ± 2.5 GPa, higher than any previously reported nucleic acid derived structure. This data suggests that the unique cation-free "basket" formed by the Fmoc-G-PNA conjugate can serve as an attractive component for the design of new materials based on PNA self-assembly for nanotechnology applications.

Self‐Assembled Quadruplex‐Inspired Peptide Nucleic Acid Tetramer for Artificial Photosynthesis

“…The Fmoc-G-PNA tetramer shows an atomic level packing similar to the four stranded topology of G-quadruplex, with the exception of the head to tail hydrogen bonding between Fmoc and guanine, thus resembling other synthetic G-quartets that possess some of the characteristic features of native G-quadruplex. [19] This synthetic G-quartet based PNA-tetramer comprises several advantages over reported templates used for the construction of fully integrated artificial photosynthesis templates, including a high mechanical rigidity (Young's modulus =~17 GPa) as reported earlier, [19] larger surface area, extreme thermal and chemical stability. Also, highly organized aromatic groups result in extensive π-π interactions and photoelectron transfer, indicating a broad-spectrum light sensitivity.…”

“…To address these issues, here, we employed our recently reported rigid G‐quartet inspired fluorenylmethoxycarbonyl (Fmoc)‐conjugated peptide nucleic acid (PNA)‐tetramer formed by the self‐assembly of Fmoc‐G‐PNA conjugate to construct a fully integrated artificial photosynthetic system. The Fmoc‐G‐PNA tetramer shows an atomic level packing similar to the four stranded topology of G‐quadruplex, with the exception of the head to tail hydrogen bonding between Fmoc and guanine, thus resembling other synthetic G‐quartets that possess some of the characteristic features of native G‐quadruplex .…”

“…The PNA molecule and the self-assembled quadruplex inspired Fmoc-G-PNA tetramer used in this study (Figure 1a,b) was synthesized and characterized as we have recently reported. [19] Briefly, PNA crystals were grown in a methanolwater mixture and single crystal X-ray diffraction analysis revealed the crystals to comprise an atomic level packing similar to synthetic G-quartets. Here, the guanine base of one PNA molecule alternatively forms an H-bond with the aliphatic tail and Fmoc group of neighbouring molecules.…”

“…Here, the guanine base of one PNA molecule alternatively forms an H-bond with the aliphatic tail and Fmoc group of neighbouring molecules. [19] This results in a cyclic tetramer, designated PNA-tetramer, which further undergoes vertical stacking, similar to the stacking of G-quartet into G-quadruplex. [20] To construct a fully integrated solid and recyclable artificial photosynthesis system, the template should be mechanically rigid, stable over a wide range of temperatures and solvents, as well as show a broad-spectrum light sensitivity.…”

“…Molecular structure and stability of the PNA-tetramer crystals. a) Chemical structure and b) Self-assembly of the quadruplex-inspired Fmoc-G-PNA tetramer [19]. c) TGA curve of the PNA-tetramer crystals.…”