Helical Polymers Research Articles

Toward Synthetic Intrinsically Disordered Polypeptides (IDPs): Controlled Incorporation of Glycine in the Ring-Opening Polymerization of N-Carboxyanhydrides.

Intrinsically disordered proteins (IDPs) do not have a well-defined folded structure but instead behave as extended polymer chains in solution. Many IDPs are rich in glycine residues, which create steric barriers to secondary structuring and protein folding. Inspired by this feature, we have studied how the introduction of glycine residues influences the secondary structure of a model polypeptide, poly(l-glutamic acid), a helical polymer. For this purpose, we carried out ring-opening copolymerization with γ-benzyl-l-glutamate and glycine N-carboxyanhydride (NCA) monomers. We aimed to control the glycine distribution within PBLG by adjusting the reactivity ratios of the two NCAs using different reaction conditions (temperature, solvent). The relationship between those conditions, the monomer distributions, and the secondary structure enabled the design of intrinsically disordered polypeptides when a highly gradient microstructure was achieved in DMSO.

Cryo-EM structures of membrane-bound dynamin in a post-hydrolysis state primed for membrane fission.

Dynamin assembles as a helical polymer at the neck of budding endocytic vesicles, constricting the underlyingmembrane as it progresses through the GTPase cycle to sever vesicles from the plasmamembrane.Although atomic models of the dynamin helical polymer bound to guanosine triphosphate (GTP) analogs define earlier stages of membrane constriction, there are no atomic models of theassembled state post-GTP hydrolysis. Here, we used cryo-EM methods to determine atomic structures of the dynamin helical polymer assembled on lipid tubules, akin to necks of budding endocytic vesicles, in a guanosine diphosphate (GDP)-bound, super-constricted state. In this state, dynamin is assembledas a 2-start helix with an inner lumen of 3.4nm, primed for spontaneous fission. Additionally, by cryo-electron tomography, we trapped dynamin helical assemblies within HeLa cells using theGTPase-defective dynamin K44A mutant and observed diverse dynamin helices, demonstrating that dynamin can accommodate a range of assembled complexes in cells that likely precede membrane fission.

High Internal Phase Emulsion for Constructing Chiral Helical Polymer-Based Circularly Polarized Luminescent Porous Materials.

Polymerized high internal phase emulsions (polyHIPEs) with circularly polarized luminescence (CPL), as an interesting class of porous materials, are of great significance for the development of CPL porous materials but have not been reported so far. Herein, we report the construction of polyHIPE-based CPL porous materials, taking advantage of an adsorption strategy. The pristine polyHIPEs constructed by chiral helical polymers, which acted as a chiral microenvironment, were fabricated by coordination polymerization of chiral acetylene monomers (R/S-SA) using HIPEs as templates. Achiral fluorescent small molecules were dispersed in the pores of the 3D porous organic chiral polymer matrix provided by polyHIPEs through the adsorption strategy, and CPL-active porous materials with blue, cyan, and green emissions were constructed using a fluorescence-selective absorption mechanism that does not rely on chirality transfer at the molecular level. The maximum luminescence dissymmetry factor (glum) value was -2.6 × 10-2. This work establishes a new and simple way for developing CPL porous materials.

Dynamic Entwined Topology in Helical Covalent Polymers Dictated by Competing Supramolecular Interactions

AbstractNaturally occurring polymeric structures often consist of 1D polymer chains intricately folded and entwined through non‐covalent bonds, adopting precise topologies crucial for their functionality. The exploration of crystalline 1D polymers through dynamic covalent chemistry (DCvC) and supramolecular interactions represents a novel approach for developing crystalline polymers. This study shows that sub‐angstrom differences in the counter‐ion size can lead to various helical covalent polymer (HCP) topologies, including a novel metal‐coordination HCP (m‐HCP) motif. Single‐crystal X‐ray diffraction (SCXRD) analysis of HCP−Na revealed that double helical pairs are formed by sodium ions coordinating to spiroborate linkages to form rectangular pores. The double helices are interpenetrated by the unreacted diols coordinating sodium ions. The reticulation of the m‐HCP structure was demonstrated by the successful synthesis of HCP−K. Finally, ion‐exchange studies were conducted to show the interconversion between HCP structures. This research illustrates how seemingly simple modifications, such as changes in counter‐ion size, can significantly influence the polymer topology and determine which supramolecular interactions dominate the crystal lattice.

Dynamic Entwined Topology in Helical Covalent Polymers Dictated by Competing Supramolecular Interactions.

Naturally occurring polymeric structures often consist of 1D polymer chains intricately folded and entwined through non-covalent bonds, adopting precise topologies crucial for their functionality. The exploration of crystalline 1D polymers through dynamic covalent chemistry (DCvC) and supramolecular interactions represents a novel approach for developing crystalline polymers. This study shows that sub-angstrom differences in the counter-ion size can lead to various helical covalent polymer (HCP) topologies, including a novel metal-coordination HCP (m-HCP) motif. Single-crystal X-ray diffraction (SCXRD) analysis of HCP-Na revealed that double helical pairs are formed by sodium ions coordinating to spiroborate linkages to form rectangular pores. The double helices are interpenetrated by the unreacted diols coordinating sodium ions. The reticulation of the m-HCP structure was demonstrated by the successful synthesis of HCP-K. Finally, ion-exchange studies were conducted to show the interconversion between HCP structures. This research illustrates how seemingly simple modifications, such as changes in counter-ion size, can significantly influence the polymer topology and determine which supramolecular interactions dominate the crystal lattice.

Sustainable Bioinspired Helical Fibrous Electronics with Interfacial Bonding, Wide Range Elasticity and High Conductivity

AbstractBecause of the weak interfacial bonding between the substrates and active materials, most stretchable electronics often face the problem of performance destabilization and functional failure, especially under large strains. Herein, a super‐elastic, high conductive and core‐shell nanofibrous helix based on polyurethane (PU), silk fibroin (SF) and liquid metal (LM) is fabricated. Compared with traditional membrane, that the LM@PU/SF fibrous helix shows a wider range of workable strain (1500%) and reversible elasticity (600%) accompany with high conductivity is found. SF is acted as “glue” to strengthen the interfacial bonding between the PU and LM. The good elasticity of the helical structure and PU polymer as well as the fluidity of LM improve the stretchability, reversible elasticity and conductivity of the fibrous helix conductor. Furthermore, an alarming and monitoring apparatus using LM@PU/SF helix as the conductive unit based on multiscale fracture is engineered. This composite nanofibrous helix with ultra‐high conductivity and elasticity, making it a promising candidate for stretchable electronic devices.

Mechanically and Thermally Robust Gel Electrolytes Built from A Charged Double Helical Polymer.

Polymer electrolytes have received tremendous interest in the development of solid-state batteries, but often fall short in one or more key properties required for practical applications. Herein, a rigid gel polymer electrolyte prepared by immobilizing a liquid mixture of a lithium salt and poly(ethylene glycol) dimethyl ether with only 8 wt% poly(2,2'-disulfonyl-4,4'-benzidine terephthalamide) (PBDT) is reported. The high charge density and rigid double helical structure of PBDT lead to formation of a nanofibrillar structure that endows this electrolyte with stronger mechanical properties, wider temperature window, and higher battery rate capability compared to all other poly(ethylene oxide) (PEO)-based electrolytes. The ion transport mechanism in this rigid polymer electrolyte is systematically studied using multiple complementary techniques. Li/LiFePO4 cells show excellent capacity retention over long-term cycling, with thermal cycling reversibility between ambient temperature and elevated temperatures, demonstrating compelling potential for solid-state batteries targeting fast charging at high temperatures and slower discharging at ambient temperature.

Synthesis and Direct Observation of Chiral Supramolecular Polymer of Porphyrin Having Cholesteryl Groups.

We report the synthesis and microscopic investigations of two chiral helical porphyrin supramolecular polymers with different coordinating metals that are expected to be capable of serving as synthetic macromolecular motors driven by thermal fluctuations. Furthermore, based on their microscopic images, we propose a stepwise process for the formation of higher-order structures. These porphyrins formed completely different association states, and this was reflected in the marked differences in the shapes of the supramolecular polymers. The Cu-TChOAlaCPP supramolecular polymers formed H-aggregate rods in diisopropyl ether, then grew into superhelices and then into ribbons. On the other hand, Zn-TChOAlaCPP supramolecular polymers formed aggregates based on van der Waals interactions in diethyl ether, then grew into fibers and then grew into multiple-helices and ribbons. In addition, we imaged the interaction between long and short chains of the Cu-TChOAlaCPP supramolecular polymer by fast-scanning atomic force microscopy, and we indicated the availability as a macromolecular motor driven by thermal fluctuations.

Spatially Resolved Anisotropic Natural Abundance Deuterium 2D-NMR Spectroscopy Using Bimesophasic Lyotropic Chiral Systems.

In this paper, we describe, for the first time, the combined and original use of spatially resolved anisotropic natural abundance deuterium (ANAD) 2D-NMR experiments and bimesophasic lyotropic chiral systems to extract two independent sets of anisotropic parameters such as 2H-RQCs from a single NMR sample. As a pioneering example, we focus on a mixture of immiscible polypeptides (PBLG) and polyacetylene helical polymers (L-MSP) dissolved in weakly polar organic solvents (chloroform). Nondeuterated (D)-(+)-camphor is used as a model chiral solute. By providing two series of 2H-RQCs, this new analytical approach paves the way for applications in 3D structure elucidation with increased reliability and also opens up original investigations in terms of spectral enantiomeric discriminations and mixing of helical polymers.

Structural basis for regulated assembly of the mitochondrial fission GTPase Drp1

Mitochondrial fission is a critical cellular event to maintain organelle function. This multistep process is initiated by the enhanced recruitment and oligomerization of dynamin-related protein 1 (Drp1) at the surface of mitochondria. As such, Drp1 is essential for inducing mitochondrial division in mammalian cells, and homologous proteins are found in all eukaryotes. As a member of the dynamin superfamily of proteins (DSPs), controlled Drp1 self-assembly into large helical polymers stimulates its GTPase activity to promote membrane constriction. Still, little is known about the mechanisms that regulate correct spatial and temporal assembly of the fission machinery. Here we present a cryo-EM structure of a full-length Drp1 dimer in an auto-inhibited state. This dimer reveals two key conformational rearrangements that must be unlocked through intramolecular rearrangements to achieve the assembly-competent state observed in previous structures. This structural insight provides understanding into the mechanism for regulated self-assembly of the mitochondrial fission machinery.

Inside Cover: Massive Molecular Motion in Crystal Leads to an Unexpected Helical Covalent Polymer in a Solid‐state Polymerization (Angew. Chem. Int. Ed. 9/2024)

Inside Cover: Massive Molecular Motion in Crystal Leads to an Unexpected Helical Covalent Polymer in a Solid‐state Polymerization (Angew. Chem. Int. Ed. 9/2024)

Innentitelbild: Massive Molecular Motion in Crystal Leads to an Unexpected Helical Covalent Polymer in a Solid‐state Polymerization (Angew. Chem. 9/2024)

Innentitelbild: Massive Molecular Motion in Crystal Leads to an Unexpected Helical Covalent Polymer in a Solid‐state Polymerization (Angew. Chem. 9/2024)

Helical Superstructures from the Hierarchical Self-Assembly of Coil-Coil Block Copolymer Guided by Side Chain Amyloid-β(17-19) LVF Peptide.

The rational design of precisely controlled hierarchical chiral nanostructures from synthetic polymers garnered inspiration from sophisticated biological materials. Since chiral peptide motifs induce helix formation in macromolecules, herein we report the synthesis of a novel type of hybrid polymer consisting of a β-sheet forming a LVF [L = leucine, V = valine, and F = phenylalanine] tripeptide pendant polymethacrylate block and a poly[poly(ethylene glycol) methyl ether methacrylate] (PPEGMA) block. The designed block copolymer self-organized into helical superstructures with a left-handed twisting sense, as visualized by field emission scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. This intriguing hierarchical self-assembly is driven by the minimalistic peptide motif that itself has a high propensity to adopt an antiparallel β-sheet conformation. We also report the generation of a diverse array of nanostructures, including spherical micelles, spindle micelles, rod-like micelles, vesicles, helical supramolecular fibers, and helical toroids via self-assembly of the designed block copolymer in tetrahydrofuran/water mixed solvents. To realize the observable helical superstructure, a twisted two-dimensional core-shell tape is proposed as a structure model in which the peptide segments form an antiparallel β-sheet with a polymer shell. The findings contribute to the advancement of a helical polymer or the superhelical self-assembly of polymers, paving the way for diverse applications in materials science and related fields.

2,2'-Tethered Binaphthyl-Embedded One-Handed Helical Ladder Polymers: Impact of the Tether Length on Helical Geometry and Chiroptical Property.

Synthetic breakthroughs diversify the molecules and polymers available to chemists. We now report the first successful synthesis of a series of optically-pure 2,2'-tethered binaphthyl-embedded helical ladder polymers based on quantitative and chemoselective ladderization by the modified alkyne benzannulations using the 4-alkoxy-2,6-dimethylphenylethynyl group as the alkyne source, inaccessible by the conventional approach lacking the 2,6-dimethyl substituents. Due to the defect-free helix formation, the circular dichroism signal increased by more than 6 times the previously reported value. The resulting helical secondary structure can be fine-tuned by controlling the binaphthyl dihedral angle in the repeating unit with variations in the 2,2'-alkylenedioxy tethering groups by one carbon atom at a time. The optimization of the helical ladder structures led to a strong circularly polarized luminescence with a high fluorescence quantum yield (28 %) and luminescence dissymmetry factor (2.6×10-3 ).

2,2′‐Tethered Binaphthyl‐Embedded One‐Handed Helical Ladder Polymers: Impact of the Tether Length on Helical Geometry and Chiroptical Property

AbstractSynthetic breakthroughs diversify the molecules and polymers available to chemists. We now report the first successful synthesis of a series of optically‐pure 2,2′‐tethered binaphthyl‐embedded helical ladder polymers based on quantitative and chemoselective ladderization by the modified alkyne benzannulations using the 4‐alkoxy‐2,6‐dimethylphenylethynyl group as the alkyne source, inaccessible by the conventional approach lacking the 2,6‐dimethyl substituents. Due to the defect‐free helix formation, the circular dichroism signal increased by more than 6 times the previously reported value. The resulting helical secondary structure can be fine‐tuned by controlling the binaphthyl dihedral angle in the repeating unit with variations in the 2,2′‐alkylenedioxy tethering groups by one carbon atom at a time. The optimization of the helical ladder structures led to a strong circularly polarized luminescence with a high fluorescence quantum yield (28 %) and luminescence dissymmetry factor (2.6×10−3).

Size dependence of optical activities in helical polymers.

Chiroptical properties of helical polymers do not always align with the sum of the local contributions of their unit cells. This study investigates the discrepancy in optical rotatory strength between local and global structures using a right-handed helical polyacetylene model. The chirality is examined through density functional theory (DFT) calculations. The analysis reveals that, at higher degrees of polymerization, the contribution of chirality from the helical strand generally surpasses the partial chirality from the local structure. The ratio of local contribution to total contribution is deduced within the framework of crystal orbital theory, and a numerical method using Wannier functions is presented for evaluation.

Massive Molecular Motion in Crystal Leads to an Unexpected Helical Covalent Polymer in a Solid-state Polymerization.

We designed a proline-derived monomer with azide and alkene functional groups to enable topochemical ene-azide cycloaddition (TEAC) polymerization. In its crystal, the monomer forms supramolecular helices along the 'a' axis through various non-covalent interactions. Along the 'c' axis, the molecules arrange themselves head-to-tail in a wave-like pattern, positioning the azide and alkene groups of adjacent molecules in close proximity and anti-parallel orientation, complying with Schmidt's criteria for topochemical reaction. This prearranged configuration was expected to facilitate smooth topochemical polymerization, resulting in a 1,4-triazoline-linked polymer. Upon heating, the monomer underwent TEAC polymerization in a remarkable single-crystal-to-single-crystal fashion, but, to our surprise, it yielded an unexpected covalent helical polymer linked by 1,5-disubstituted triazoline units. Remarkably, the crystal avoids the ready-to-react arrangement for polymerization, but connects monomer molecules within the supramolecular helix through the cycloaddition of azide and alkene groups, even though they are not in close proximity nor in the expected orientation. This unexpected path, involving a substantial 134° rotation of the alkene group, yields hitherto unknown 1,5-disubstituted triazoline product regiospecifically. This study serves as a cautionary reminder that relying solely on topochemical postulates for predicting reactivity can sometimes be misleading.

Massive Molecular Motion in Crystal Leads to an Unexpected Helical Covalent Polymer in a Solid‐state Polymerization

AbstractWe designed a proline‐derived monomer with azide and alkene functional groups to enable topochemical ene‐azide cycloaddition (TEAC) polymerization. In its crystal, the monomer forms supramolecular helices along the ‘a’ axis through various non‐covalent interactions. Along the ‘c’ axis, the molecules arrange themselves head‐to‐tail in a wave‐like pattern, positioning the azide and alkene groups of adjacent molecules in close proximity and anti‐parallel orientation, complying with Schmidt's criteria for topochemical reaction. This prearranged configuration was expected to facilitate smooth topochemical polymerization, resulting in a 1,4‐triazoline‐linked polymer. Upon heating, the monomer underwent TEAC polymerization in a remarkable single‐crystal‐to‐single‐crystal fashion, but, to our surprise, it yielded an unexpected covalent helical polymer linked by 1,5‐disubstituted triazoline units. Remarkably, the crystal avoids the ready‐to‐react arrangement for polymerization, but connects monomer molecules within the supramolecular helix through the cycloaddition of azide and alkene groups, even though they are not in close proximity nor in the expected orientation. This unexpected path, involving a substantial 134° rotation of the alkene group, yields hitherto unknown 1,5‐disubstituted triazoline product regiospecifically. This study serves as a cautionary reminder that relying solely on topochemical postulates for predicting reactivity can sometimes be misleading.

Metallo‐Supramolecular Helical Fibres from Chiral Phenylacetylene Monomers: Cation Induced Self‐Assembly

AbstractChiral metallo‐supramolecular fibres can be easily obtained by mixing a chloroform solution of a phenylacetylene monomer (PA) that bears a chiral sulfoxide group as pendant, with different equivalents of a methanolic solution of AgClO4. Thus, while the PA is found molecularly dissolved in chloroform, the addition of Ag+ ions induce its aggregation through the formation of an axially chiral metallo‐supramolecular aggregate with high thermal stable properties. In this case, the ability of the metal ion to coordinate the PA triple bond, combined with the argentophilicity of the metal ion and the planarity of the phenylacetylene drives to the formation of a helical coordination polymer, whose P or M axial chirality is determined by the chirality of the sulfoxide used as substituent of the PA. Depending on the PA/Ag+ (mol/mol) ratio, it is possible to tune the morphology of the metallo‐supramolecular aggregate from chiral fibers to chiral gel.

Metallo-Supramolecular Helical Fibres from Chiral Phenylacetylene Monomers: Cation Induced Self-Assembly.

Chiral metallo-supramolecular fibres can be easily obtained by mixing a chloroform solution of a phenylacetylene monomer (PA) that bears a chiral sulfoxide group as pendant, with different equivalents of a methanolic solution of AgClO4 . Thus, while the PA is found molecularly dissolved in chloroform, the addition of Ag+ ions induce its aggregation through the formation of an axially chiral metallo-supramolecular aggregate with high thermal stable properties. In this case, the ability of the metal ion to coordinate the PA triple bond, combined with the argentophilicity of the metal ion and the planarity of the phenylacetylene drives to the formation of a helical coordination polymer, whose P or M axial chirality is determined by the chirality of the sulfoxide used as substituent of the PA. Depending on the PA/Ag+ (mol/mol) ratio, it is possible to tune the morphology of the metallo-supramolecular aggregate from chiral fibers to chiral gel.