Coassembly of Complementary Peptide Nucleic Acid into Crystalline Structures by Microfluidics

Abstract

The self‐assembly of simple units into well‐ordered supramolecular polymeric structures may give rise to a broad range of desirable attributes. In the field of bionanotechnology, there are two main classes commonly used as building blocks for self‐assembly—amino acids and nucleobases. While protein, peptide, and amino acid building blocks propose broad chemical versatility, the specific Watson–Crick base pairings of nucleic acids allow rational design and precise control over the assembly process. Specifically, artificially synthesized peptide nucleic acids (PNA), short DNA mimics that have an amide backbone, can present a unique set of properties while preserving the specific base pairing of the nucleic acids. The use of complementary building blocks allows the study of supramolecular polymer coassemblies. Here, the coassembly of two paired di‐PNA building blocks provides a new layer of control, as both building blocks are required for the spontaneous assembly to occur. Utilizing a microfluidic system, the growth of the well‐ordered structure can be regulated and monitored. The crystal structure of the formed assemblies display Watson–Crick base pairing with similar distances as those found in typical DNA double helices. Moreover, the crystals exhibit intriguing optical properties that may be implemented in various materials science and nanotechnological applications.

On-off transition and ultrafast decay of amino acid luminescence driven by modulation of supramolecular packing

“…It was shown that single amino acids in their aggregated form can also produce a fluorescent signal, which is not evident in the monomeric state (Babar and Sarkar, 2017;Banerjee et al, 2020;Niyangoda et al, 2017;Shaham-Niv et al, 2018). Numerous observations suggest that the optical phenomenon of aggregation-induced intrinsic fluorescence is broader than originally speculated, as it also applies to many other metabolites and nucleic acids (Arnon et al, 2019;Berger et al, 2015;Chen et al, 2018;Lakowicz et al, 2001;Stephens et al, 2020;Zou et al, 2002). Circumstantial evidence and argumentation suggested that supramolecular packing is important.…”

“…The phenomenon of aggregation-dependent luminescence of proteins is a rapidly evolving field ( Ardona et al., 2017 ; Arnon et al., 2019 ; Babar and Sarkar, 2017 ; Banerjee et al., 2020 ; Berger et al., 2015 ; Bhattacharya et al., 2017 ; Chan et al., 2013 ; Kong et al., 2019 ; Niyangoda et al., 2017 ; Pansieri et al., 2019 ; Pinotsi et al, 2013 , 2016 ; Prasad et al., 2017 ; Shaham-Niv et al., 2018 ). Protein aggregates were shown to absorb light at wavelengths above 300 nm and to exhibit a structure-specific fluorescence in the visible range, even in the absence of aromatic amino acids ( Del Mercato et al., 2007 ).…”

On-off transition and ultrafast decay of amino acid luminescence driven by modulation of supramolecular packing

“…Such a behaviour of the fluorescence emission band is known as the red-edge excitation shift effect and is characteristic for the self-assembly induced fluorescence of amino acids, peptides and proteins. 16,17,27 The presence of elongated fibrillar structures was detectable by fluorescence lifetime imaging, without the use of any external dyes, only by using the autofluorescence signal of the sample (Figure 4c). The autofluorescence decay curve obtained for the phenylalanine fibrils, revealed the presence of 0.35 and 2.53 ns decay times after fitting to a biexponential model (Figure 4d).…”

“…[10][11][12][13] Numerous observations suggest that the optical phenomenon of aggregation induced intrinsic fluorescence is broader than originally speculated, as it also applies to many other metabolites and nucleic acids. [14][15][16][17][18][19] Circumstantial evidence and argumentation suggested that supramolecular packing is important. It was suggested that the hydrogen bonds and, in specific cases, the aromatic stacking, can underlie these optical properties.…”

“…The phenomenon of aggregation-dependent luminescence of proteins is a rapidly evolving field. 1,2,17,[22][23][24][3][4][5][10][11][12][13]16 Protein aggregates were shown to absorb light at wavelengths above 300 nm and to exhibit a structure-specific fluorescence in the visible range, even in the absence of aromatic amino acids. 6 A plausible explanation for this phenomenon is the formation of structure-specific supramolecular fluorophores that are permissive to proton transfer across hydrogen bonds.…”