Constructing polymeric toroids with a uniform, tunable size is challenging. Reported herein is the formation of uniform toroids from poly(γ‐benzyl‐l‐glutamate)‐graft‐poly(ethylene glycol) ...(PBLG‐g‐PEG) graft copolymers by a two‐step self‐assembly process. In the first step, uniform rodlike micelles are prepared by dialyzing the polymer dissolved in tetrahydrofuran (THF)/N,N′‐dimethylformamide (DMF) against water. With the addition of THF in the second step, the rodlike micelles curve and then close end‐to‐end to form uniform toroids, which resemble a cyclization reaction.
Rodlike micelles, self‐assembled from polypeptide graft copolymers with rigid backbones, can exclusively close end‐to‐end to form toroids under solvent and temperature stimuli. This transformation resembles a cyclization reaction.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
In recent years, toroidal nanostructures have become an appealing topic in nanoscience owing to their unique structure and promising applications. Among them, polymeric toroidal self‐assemblies have ...attracted considerable attention because of their manipulability and diversity. Despite the substantial advances in the area of polymeric nanotoroids, the universal formation principles and functions of these toroids have not been sufficiently summarized. This article aims to review recent advances in the formation and function of polymeric nanotoroids. The significant role of theoretical simulations in revealing the formation mechanism and inherent structure of toroidal assemblies is emphasized. Additionally, a perspective on the challenges of this research field is addressed.
Polymeric toroidal assemblies have attracted considerable attention because of their unique geometry and properties. In this review, the formation routes and functions of polymeric toroids are summarized. The significant role of theoretical simulations in revealing the formation mechanism and inherent structure of toroidal assemblies is emphasized.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
At the molecular level, intermolecular polymerization can compete with its intramolecular cyclization, which is known as a ring–chain competition reaction. However, this competitive phenomenon has ...rarely been observed in higher-level systems. Herein, we report a supramolecular ring–chain competition reaction between the intermicellar polymerization and intramicellar cyclization of rodlike micelles assembled from rod–coil graft copolymers. Nanowires and toroidal micelles are the chain-like and ring-like products of the two supramolecular reactions, respectively. When the reaction conditions (solvent composition or temperature) are varied, the competition of the two supramolecular reactions is induced, and their dynamic competition relation and equilibrium constants can be regulated by the reaction conditions. The combination of experiments and theoretical simulations reveals that the interplay of the core/shell interfacial energy, the bending energy of rodlike micelles, and the end-capping energy determines such ring–chain competition. This study presents an advance in supramolecular self-assembly and provides a progressive way to construct complex hierarchical nanostructures.
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IJS, KILJ, NUK, PNG, UL, UM
The self-assembly behavior of poly(γ-benzyl-l-glutamate)-graft-poly(ethylene glycol) rod−coil graft copolymers in aqueous solution was investigated. With tetrahydrofuran (THF) as initial solvent, ...vesicles were observed for the graft copolymers with lower degree of grafting. When the degree of grafting increases, the aggregate morphology transforms from vesicles to spindle-like micelles then to spherical micelles. When N , N′-dimethylformamide (DMF) is introduced into the initial solvent, the vesicles transform to spindles. Increasing DMF volume fraction leads to a spindle to connected-spindle transition. On the basis of the experimental results, the mechanism of the morphological transition of the rod−coil graft copolymer is suggested.
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IJS, KILJ, NUK, PNG, UL, UM
A novel linear-dendron-like polyampholyte, poly(l-lysine)-b-D2-poly(l-glutamic acid) PLL-b-D2-(PLGA)4, where D2 is the second generation of poly(amido amine), was prepared by hydrolyzing ...poly(ε-benzyloxycarbonyl-l-lysine)-b-D2-poly(γ-benzyl-l-glutamate) copolymer which was synthesized via a combination of ring-opening polymerization and click chemistry. The pH-responsive self-assembly behaviors of PLL-b-D2-(PLGA)4 were investigated in detail. It is found that PLL-b-D2-(PLGA)4 can self-assemble into PLGA-core aggregates at acidic pH and PLL-core aggregates at alkaline pH, which was accompanied with the coil-to-helix conformational transition of PLGA and PLL segments, respectively. The self-assembled aggregates with various morphologies, such as large compound micelles, worm-like micelles, large compound vesicles, simple vesicles, and rigid tubular structures have been obtained in “schizophrenic” aggregation process with simply increasing the solution pH. The hierarchical assembled fractal structures of PLL-b-D2-(PLGA)4 were observed during the solvent evaporation at high pH value.
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IJS, KILJ, NUK, PNG, UL, UM
Self-assembly of mixture systems containing poly(acrylic acid)-g-poly(γ-benzyl-l-glutamate) graft copolymers (PAA-g-PBLG) and PBLG homopolymers in aqueous solution was investigated by both ...experiments and computer simulations. It was found that the aggregate morphologies, such as rods, curved rods, and toroids, could be tuned by the homopolymer content. The toroidal micelles with uniform size were formed when the homopolymer content in the hybrid aggregates is higher. The effect of added water content on the toroid formation process was studied. Rods and curved rods were observed sequentially before formation of toroids. We also performed dissipative particle dynamics (DPD) simulations to verify the structure transition and explore the formation mechanism of the toroidal aggregates. The DPD results are in good agreement with the experimental findings and provide additional information such as chain distribution in aggregates, which is difficult to be gained through experiments. On the basis of the experimental and simulation results, the formation mechanism of the toroidal micelles was suggested.
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IJS, KILJ, NUK, PNG, UL, UM
Self-assembly behavior of rod–coil–rod poly(γ-benzyl-l-glutamate)-b-poly(ethylene glycol)-b-poly(γ-benzyl-l-glutamate) (PBLG-b-PEG-b-PBLG) triblock copolymers with various PBLG block lengths in ...aqueous solution was investigated. The PBLG-b-PEG-b-PBLG triblock copolymers are able to self-assemble into vesicles when PBLG block length is relatively short. Meanwhile, the initial polymer concentration was found to have influence on the self-assembly. Giant vesicles can be observed when the initial concentration is high. Dissipative particle dynamics (DPD) simulations about the vesicles revealed that the rigid rod blocks could be aligned parallelly with each other to form the monolayer vesicles wall. When the PBLG block length in the PBLG-b-PEG-b-PBLG triblock copolymers increases, the aggregate morphologies were observed to transform from vesicles to spherical micelles. Based on the experimental and simulation results, we proposed a possible mechanism of the morphological transitions of the rod–coil–rod triblock copolymer aggregates.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Hybrid polymeric micelles self-assembled from a mixture containing poly(γ-benzyl-l-glutamate)-block-poly(ethylene glycol) (PBLG-b-PEG) block copolymer and gold nanoparticles (AuNPs) were prepared. ...The effect of AuNPs on the self-assembly behavior of PBLG-b-PEG was studied both experimentally by transmission electron microscopy, scanning electron microscopy, and laser light scattering and computationally using dissipative particle dynamics (DPD) simulations. It was found that, the pure PBLG-b-PEG block copolymer self-assembles into long cylindrical micelles. By introducing AuNPs to the stock block copolymer solution, the formed aggregate morphology transforms to spherical micelles. The DPD simulation results well reproduced the morphological transformations observed in the experiments. And the simulation revealed that the main reason for the aggregate morphology transformation is the breakage of ordered packing of PBLG rods in micelle core by the added nanoparticles. Moreover, from the DPD simulations, the distribution information on nanoparticles was obtained. The nanoparticles were found to prefer to locate near the core/shell interface as well as in the core center of the micelles. The combination of experimental and simulation methods lead to a comprehensive understanding of such a complex self-assembly system.
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IJS, KILJ, NUK, PNG, UL, UM
We found that poly(γ-benzyl-L-glutamate)-block-poly(ethylene glycol) (PBLG-b-PEG) rod-coil block copolymers and polystyrene (PS) homopolymers can cooperatively self-assemble into nano-spheres with ...striped patterns on their surfaces (strip-pattern-spheres) in aqueous solution. With assistance of dissipative particle dynamics simulation, it is discovered that the PS homopolymers form a spherical template core and the PBLG-b-PEG block copolymers assemble into striped patterns on the spherical surface. The hydrophobic PBLG rods are packed orderly in the strips, while the hydrophilic PEG blocks stabilize the strip-pattern-spheres in solution. Defects such as dislocations and disclinations can be observed in the striped patterns. Self-assembling temperature and sphere radius are found to affect defect densities in the striped patterns. A possible mechanism is proposed to illustrate how PBLG-b-PEG and PS cooperatively self-assemble into hierarchical spheres with striped patterns on surfaces.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Eukaryotic cilia and flagella have highly conserved 9 + 2 structures. They are functionally diverged to play cell-type-specific roles even in a multicellular organism. Although their structural ...components are therefore believed to be common, few studies have investigated the molecular diversity of the protein components of the cilia and flagella in a single organism. Here we carried out a proteomic analysis and compared protein components between branchial cilia and sperm flagella in a marine invertebrate chordate, Ciona intestinalis. Distinct feature of protein recruitment in branchial cilia and sperm flagella has been clarified; (1) Isoforms of α- and β-tubulins as well as those of actins are distinctly used in branchial cilia or sperm flagella. (2) Structural components, such as dynein docking complex, tektins and an outer dense fiber protein, are used differently by the cilia and flagella. (3) Sperm flagella are specialized for the cAMP- and Ca2+-dependent regulation of outer arm dynein and for energy metabolism by glycolytic enzymes. Our present study clearly demonstrates that flagellar or ciliary proteins are properly recruited according to their function and stability, despite their apparent structural resemblance and conservation.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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