High-Resolution Cryo-Electron Microscopy Reveals the Unique Striated Hollow Structure of Photocatalytic Macrocyclic Polydiacetylene Nanotubes

Abstract

High-resolution structures are crucial for understanding the functional properties of nanomaterials. We applied single-particle cryo-electron microscopy (cryo-EM), a method traditionally used for structure determination of biological macromolecules, to obtain high-resolution structures of synthetic non-biological filaments formed by photopolymerization of macrocyclic diacetylene (MDA) amphiphilic monomers. Tomographic analysis showed that the MDA monomers self-assemble into hollow nanotubes upon dispersion in water. Single-particle analysis revealed tubes consisting of six pairs of covalently bonded filaments held together by hydrophobic interactions, where each filament is composed of macrocyclic rings stacked in parallel “chair” conformations. The hollow MDA nanotube structures we found may account for the efficient scavenging of amphiphilic pollutants in water and subsequent photodegradation of the guest species.

Structural Elucidation of a Polypeptoid Chain in a Crystalline Lattice Reveals Key Morphology-Directing Role of the N-Terminus

“…Peptoid nanosheets have been imaged using cryo-TEM, ,,, however, the 3D molecular conformation of an individual synthetic polymer chain in a crystalline polymer lattice has not yet been directly observed due to increased heterogeneity of their assemblies. Single-particle analysis (SPA) is an emerging powerful imaging technique to analyze the molecular details at atomic and near-atomic resolution of assembled nanostructures from natural biopolymer complexes (e.g., peptide assemblies, ribosomes, membrane proteins, , viruses) or synthetic organic and inorganic materials. , It not only enables the 2D and 3D classification of inhomogeneity in the nanostructures , but also allows for reference-free ab initio 3D reconstructions using sophisticated algorithms. , Here, we apply cryo-TEM 3D reconstruction to directly visualize the spatial conformation of the peptoid chain in crystalline peptoid fibrils.…”

Light-Induced Self-Assembled Polydiacetylene/Carbon Dot Functional “Honeycomb”

“…The pronounced photocatalytic activity of the bis-ADA/MCDA-EDEA/C-dot film likely arise from the high surface area of the macropore structure and hydrophobicity allowing efficient adsorption of the dye molecules, and the presence of conjugated polydiacetylene network. 19,66,67 Figure 6B reveals that around 50% of the R6G degradation efficiency is retained after three cycles. This result indicates photocatalytic recyclability of the bis-ADA/MCDA-EDEA/C-dot system, although film degradation prevents considerable multiple usage.…”

“…Polydiacetylenes (PDAs) are a class of unique chromatic conjugated polymers formed by the topochemical ultraviolet (UV) light induced polymerization of diacetylene (DA). − Diacetylene units can be particularly incorporated within varied linear or cyclic molecular scaffolds, giving rise to stable self-assembled nano- and microstructures. − Due to their unique optical and electronic properties, such nanostructures have been used in numerous applications including sensing, , drug delivery, , energy storage materials, , and others. Fabrication of composite micro/nano PDA structures with nanoparticles like ZnO 2 , TiO 2 , or Au/Ag NP’s , have been also reported, contributing to interesting applications in sensing ,− and photonic devices …”

Nanoarchitectonics of Exfoliated Flexible Nanosheet Based on Laterally Stacked Macrocycles

“…In our previous works, the similar MCDA molecules preserved the chair‐like conformation in the organized states (Figure S2, Supporting Information). [ 45,48,49 ]…”

“…In our previous works, the similar MCDA molecules preserved the chair-like conformation in the organized states (Figure S2, Supporting Information). [45,48,49] The monomeric MCDA and p-MCDA showed the peaks corresponding to C≡C bond of the DA moiety ≈2250 cm −1 on the Raman spectra (band F of spectra (i) and (ii) in Figure 2b). After the polymerization of p-MCDA, the peaks ≈1450 and 2100 cm −1 corresponding to the ene-yne structure were observed for PMCDA (bands D and E of spectrum (iii) in Figure 2b).…”