Self‐Assembling of Fmoc‐GC Peptide Nucleic Acid Dimers into Highly Fluorescent Aggregates

Abstract

Self-assembling of molecules by non-covalent interactions is one of the most attracting topics in supramolecular chemistry. The use of short peptides or modified nucleotides as building blocks of the aggregates is particularly intriguing, as these are very easy to synthesize; moreover subtle changes in the chemical structure of such building blocks may drastically affect the properties of the aggregates. The ability of Peptide Nucleic Acids to aggregate is yet very little explored, despite its practical applications. In this work we investigated the self-assembling properties of a PNA dimer, conjugated at the N-terminus to a fluorenylmethoxycarbonyl group. This PNA dimer forms nano-aggregates at low concentration in CHCl 3 /CH 3 OH mixtures. The aggregates keep very interesting fluorescent properties (high quantum yield in the visible region with lifetime in the nanoseconds scale), which make them a promising material for applications in optoelectronic.

Fluorescence and Morphology of Self‐Assembled Nucleobases and Their Diphenylalanine Hybrid Aggregates

“…This phenomenon has already been observed for aggregates formed by PNAs andi sa ttributed to the interactions of aggregates with solvents. [9,10] The ca ggregates instead show a4 0nmS tokes shift andn oR EES, which suggest ad ifferent polarity of the aggregates. The shift of the absorption band toward higher wavelengths, the sharpeningo ft he bands observed for the aggregatesr elative to those of monomeric species,a nd the fluorescenceo ft he samples suggest the formation of J-type aggregatesi na ll cases.…”

“…Aggregates of a and t show Stokes shifts of about 80 nm and an increase in the emission wavelength at increasing excitation wavelength (red edge excitation shift (REES); Figure S1 in the Supporting Information). This phenomenon has already been observed for aggregates formed by PNAs and is attributed to the interactions of aggregates with solvents . The c aggregates instead show a 40 nm Stokes shift and no REES, which suggest a different polarity of the aggregates.…”

“…Moreover, fluorenylmethyloxycarbonyl (Fmoc)-protectedg cs elf-assembles at av ery low concentration in organic solvents, to give fluorescent supramolecular structuresc haracterizedb yavery high quantum yield in the visible range with al ifetime in the nanosecondr ange. [10] This evidence makes these compounds promising for the development of novel optoelectronicm aterials. Fmoc-/benzhydryloxycarbonyl (Bhoc)-protected PNA g monomers form uniform spherical assembliest hat arrange in a 2D periodic fashion, similar to that of gr esidues on the skin of chameleons, and respond with ac olor change to an increase in salt concentration.…”

“…For example, guanine (g)–cytosine (c) dimers produce voltage‐dependent electroluminescence and excitation‐dependent fluorescence in the visible range. Moreover, fluorenylmethyloxycarbonyl (Fmoc)‐protected gc self‐assembles at a very low concentration in organic solvents, to give fluorescent supramolecular structures characterized by a very high quantum yield in the visible range with a lifetime in the nanosecond range . This evidence makes these compounds promising for the development of novel optoelectronic materials.…”

Coassembly of Complementary Peptide Nucleic Acid into Crystalline Structures by Microfluidics

“…These structures, which exhibit interesting broad fluorescence, could be highly useful for the design of novel materials with unique structural and physical properties. Furthermore, it was demonstrated that modifying these molecules with the aromatic protective group fluorenylmethoxycarbonyl (Fmoc) generates aggregates displaying high quantum yield in the visible region with lifetimes on the nanosecond scale . Moreover, protected guanine‐based PNA monomers were shown to assemble into spheres, which further organize into a periodic layer arrangement to produce photonic crystals …”