Chiral Components Research Articles

Chiral Hydrogel Nerve Conduit Boosts Peripheral Nerve Regeneration via Regulation of Schwann Cell Reprogramming.

The Schwann cell (SC) is essential in peripheral nerve regeneration by reprogramming into a stem-like "repair Schwann cell" (rSC) phenotype; however, maintaining the rSC stemness remains an unmet challenge. Chirality is a fundamental factor controlling cell fate, and its potential role in regulation of SC reprogramming has long been ignored and remains poorly understood. Herein, inspired by natural chiral components in the SC microenvironment, chiral hydrogel nerve conduits are prepared by supramolecular assembly of l/d-phenylalanine derivatives (l/d-Phe) in polymeric chitosan-gelatin conduits. Right-handed l-Phe fibers within hydrogel conduits maintain the stemness of rSC through enhanced stereoselective interaction between collagen IV and l-Phe fibers triggered by collagen IV-Integrin α1β1, MAPK, and YAP/TAZ signaling pathways and finally activate the key regulator of SC reprogramming, the c-Jun pathway. In the rat model of a sciatic nerve defect, the l-Phe hydrogel nerve conduit significantly enhances nerve regeneration, exhibiting markedly improved histological, electrophysiological, and functional outcomes. The findings reveal the chirality-dependent regulation of SC reprogramming in a pioneering way, offering potential strategies for nerve regeneration therapies.

Stereoisomeric separation and chiral recognition mechanism study of star cyclodextrin polymer as the chiral stationary phase

BackgroundAs the derivatives of cyclodextrin (CD), cyclodextrin polymers (CDPs) effectively increase the concentration of CD units and construct supramolecular structures with unique stereoselectivity by the structure design. CDPs have shown significant potential in chiral separation, however, the process of stereoselective interactions on chiral stationary phases (CSPs) and the specific contribution of intermolecular forces are still a challenge issue. A comprehensive understanding of the chiral recognition mechanism of CDPs will help to optimize chiral separation conditions and design new CSPs. ResultsThe star CDP with a supermolecular structure was synthesized by grafting β-CD onto the external 6-position hydroxyl groups using β-CD as the parent nucleus. The enhanced host-guest recognition ability of CD supramolecular polymer structure provided better inclusion interaction and increased chiral recognition of the isomers. The Star-CD CSP with star CDP as a chiral ligand performed satisfactory stereoisomer separation ability with the separation factor (α) up to 2.0 for various quinoline alkaloid isomers and 1.89 for catechins. To elucidate its chiral separation mechanism, molecular docking was used to construct the three-dimensional visual models of the binding sites and the contribution of non-covalent interactions between Star-CD CSP and quinoline alkaloid isomers. In addition, the formation sites of non-covalent interactions on the CD monomers of the polymer side chains were confirmed from the actual geometric structure by analyzing the NMR chemical shift changes before and after the formation of complexes between Star-CD polymers and isomers. Combined with the mutual evidence of molecular simulation and chiral NMR, the specific recognition mechanism of selector-selectand complexes was comprehensively expounded. SignificanceThe multi-mode CSP based on cyclodextrin supramolecular structure provides new ideas for the stereoisomeric separation of complex chiral components with multiple chiral centers in natural products. Not limited to the macroscopic performance of the chromatographic separation, molecular docking explored the theoretical model of chiral recognition from the molecular level. The chiral NMR analysis confirmed the credibility of the model from the geometry structure, and then the recognition mechanism of multi-mode CSP was fully elaborated combining the above three aspects.

Stereospecific supramolecular polymerization of nanoclusters into ultra-long helical chains and enantiomer separation

During the construction of supramolecular polymers of smaller nanoparticles/nanoclusters bearing hierarchy and homochirality, the mechanism understanding via intuitive visualization and precise cross-scale chirality modulation is still challenging. For this goal, a cooperative self-assembly strategy is here proposed by using ionic complexes with uniform chemical composition comprising polyanionic nanocluster cores and surrounded chiral cationic organic components as monomers for supramolecular polymerization. The single helical polymer chains bearing a core-shell structure at utmost length over 20 μm are demonstrated showing comparable flexibility resembling covalent polymers. A nucleation-elongation growth mechanism that is not dealt with in nanoparticle systems is confirmed to be accompanied by strict chiral self-sorting. A permeable membrane prepared by simple suction of such supramolecular polymers displays high enantioselectivity (e.e. 98% after four runs) for separating histidine derivatives, which discloses a benefiting helical chain structure-induced functionalization for macroscopic supramolecular materials in highly efficient racemate separation.

The Functional Significance of Cardiac Looping: Comparative Embryology, Anatomy, and Physiology of the Looped Design of Vertebrate Hearts.

The flow path of vertebrate hearts has a looped configuration characterized by curved (sigmoid) and twisted (chiral) components. The looped heart design is phylogenetically conserved among vertebrates and is thought to represent a significant determinant of cardiac pumping function. It evolves during the embryonic period of development by a process called "cardiac looping". During the past decades, remarkable progress has been made in the uncovering of genetic, molecular, and biophysical factors contributing to cardiac looping. Our present knowledge of the functional consequences of cardiac looping lags behind this impressive progress. This article provides an overview and discussion of the currently available information on looped heart design and its implications for the pumping function. It is emphasized that: (1) looping seems to improve the pumping efficiency of the valveless embryonic heart. (2) bilaterally asymmetric (chiral) looping plays a central role in determining the alignment and separation of the pulmonary and systemic flow paths in the multi-chambered heart of tetrapods. (3) chiral looping is not needed for efficient pumping of the two-chambered hearts of fish. (4) it is the sigmoid curving of the flow path that may improve the pumping efficiency of lower as well as higher vertebrate hearts.

Chirality Interplay between the Interior and Exterior of Metal–Organic Cages

AbstractA series of metal–organic cages featuring two stereogenic elements, in terms of the twisting of amide moieties within the ligand backbones and the rotation of diazaanthracene segments along the ligand ridges, were exploited. These two chiral components are correlative and serve as relays for transmitting chirality information between the internal and external cages. The chirality information induced by a chiral guest inside the cage cavity can pass through the cage framework and influence the orientation of the diazaanthracene segments on the periphery of the cage. In turn, the chirality of a stereogenic center within the diazaanthracene segments can transfer back into the cavity, enabling discrimination of enantiomeric guests.

Gas chromatographic techniques and spectroscopic approaches for a deep characterization of Piper gaudichaudianum Kunth essential oil from Brazil

Piper gaudichaudianum Kunth essential oil (EO) is a natural source of bioactive components, having multiple therapeutic applications. Its chemical composition is highly variable, and strictly depends on abiotic factors, resulting in various biological activities. The present study details the utilization of multiple gas chromatographic techniques alongside nuclear magnetic resonance (NMR) spectroscopy to characterize the essential oil of Piper gaudichaudianum Kunth from Brazil. Seventy-six components were identified using GC–MS analysis, while enantio‑selective multidimensional gas chromatography elucidated the enantiomeric distribution of eight chiral components, for the first time in the literature. Following GC–MS analysis, an unidentified component, constituting approximately 27 % of the total oil, prompted an isolation step through preparative gas chromatography. Through the combined use of nuclear magnetic resonance, GC-Fourier transform infrared spectroscopy (FTIR), and mass spectrometry (MS), the unknown molecule was structurally identified as 4-[(3E)‑dec-3-en-1-yl]phenol. Remarkably, it was identified as a known molecule, gibbilimbol B, and not previously listed in any MS database. Subsequently, the spectrum was included in a commercial library, specifically the FFNSC 4.0 MS database, for the first time.

Supersymmetric States in Anti-de Sitter D=3 Supergravity with Chiral Torsion.

In this Letter, we construct a supersymmetric model, obtained by deforming N=2 anti-de Sitter D=3 supergravity through a chiral vector component of the torsion. Moreover, we study the existence of supersymmetric states of such theory by inspecting the presence of Killing spinors on a specific bosonic solution.

Fluorescence-Selective Absorption and Circularly Polarized Fluorescence Energy Transfer Assist the Generation of Multicolor Circularly Polarized Luminescence in Chiral Helical Polyacetylene-Based Janus Nanofibers.

Chiroptical nanomaterials with circularly polarized luminescence (CPL) performance have aroused increasing attention. Herein, multicolor CPL-active Janus nanofibers are prepared through a simple parallel electrospinning method using chiral helical polyacetylenes as the chiral source and achiral fluorophores as the fluorescent source. Interestingly, despite a direct spatial isolation between the chiral component and the fluorescent component, blue and green CPL emissions can still be obtained due to the fluorescence-selective absorption behavior of chiral helical polyacetylenes, with a satisfactory dissymmetric factor (glum) of 2 × 10-2 and 2.5 × 10-3, respectively. Moreover, by taking advantage of the circular polarization fluorescence energy transfer process, red CPL emission is further achieved using the obtained blue and green CPL as energy donors and the achiral red fluorophore as an energy acceptor. The present work offers a facile approach to prepare multilevel-structured chiroptical materials with promising application potentials in a flexible photoelectric device.

Effect of the mixing of s-wave and chiral p-wave pairings on electrical shot noise properties of normal metal/superconductor tunnel junctions

Abstract We study theoretically the electrical shot noise properties of tunnel junctions between a normal metal and a superconductor with the mixture of singlet $s$-wave and chiral triplet $p$-wave pairing due to broken inversion symmetry. We investigate how the shot noise properties vary as the relative amplitude between the two parity components in the pairing potential is changed. It is demonstrated that some characteristics of the electrical shot noise properties of such tunnel junctions may depend sensitively on the relative amplitude between the two parity components in the pairing potential, and some significant changes may occur in the electrical shot noise properties when the relative amplitude between the two parity components is varied from the singlet $s$-wave pairing dominated regime to the chiral triplet $p$-wave pairing dominated regime. In the chiral triplet $p$-wave pairing dominated regime, the ratio of noise power to electric current is close to $2e$ both in the in-gap and in the out-gap region. In the singlet $s$-wave pairing dominated regime, the value of this ratio is close to $4e$ in the inner gap region but may reduce to about $2e$ in the outer gap region as the relative amplitude of the chiral triplet pairing component is increased. The variations of the differential shot noise with the bias voltage also exhibit some significantly different features in different regimes. Such different features can serve as useful diagnostic tools for the determination of the relative magnitude of the two parity components in the pairing potential.

Intramolecular halogen bonding: Enantiomer induced by 'rhombic-shape' intramolecular halogen bonding

Programmable supramolecular materials assembled from chiral components are receiving increasing attention. Herein, we report a self-assembled racemic based on a halogenated Schiff base complex, [Cu3L2Cl2(H2O)] (L = N, N'-bis (3-Bromosalicylidene) ethylene-1,3-diaminopropane). Structural analysis reveals that the disappearance of molecular symmetry is closely related to the unique intramolecular 'rhombic-shape' halogen bonding of the compound. To the best of our knowledge, this is the first example of 'rhombic-shape' halogen bonding within a single molecule. To gain deeper mechanistic insight into the formation of this peculiar structure, we performed a series of structural analyses and theoretical calculations on the reported compound. The results suggest that the 'rhombic-shape' halogen bonding structure formed among the four Br atoms is asymmetric. This asymmetry structural feature further affects the molecular symmetry and serves as the primary factor inducing the special chirality in the molecule.

Stereoselective Amine-omics Using Heavy Atom Isotope Labeled l-and d-Marfey's Reagents.

Biological amines and amino acids play essential roles in many biochemical processes. The chemical complexity of biological samples is challenging, and the selective identification and quantification of amines and amino acid stereoisomers would be very useful for amine-focused "amino-omics" studies. Many amines and amino acids are chiral, and their stereoisomers cannot be resolved on achiral media without chiral derivatization. In prior studies, we demonstrated the use of Marfey's reagent─a chiral derivatization reagent for amines and phenolic OH groups─for the LC-MS/MS resolution and quantification of amines and amino acid stereoisomers. In this study, a heavy atom isotope labeled Marfey's reagent approach for the stereoselective detection and quantification of amines and amino acids was developed. Heavy (13C2) l-Marfey's (Hl-Mar) and heavy (2H3) d-Marfey's (Hd-Mar) were synthesized from 13C2-l-Ala and 2H3-d-Ala, respectively. Both light and heavy Marfey's reagents were used to derivatize standard amine mixtures, which were analyzed by LC-QToF-HRMS. Aligned peak lists were comparatively analyzed by light vs heavy Mar mass differences to identify mono-, di-, and tri-Marfey's adducts and then by the retention time difference between l- and d-Mar derivatives to identify stereoisomers. This approach was then applied to identify achiral and chiral amine and amino acid components in a methicillin-resistant Staphylococcus aureus (MRSA) extract. This approach shows high analytical selectivity and reproducibility.

Enantioselective Construction of Chiral THIQUINOL and Its Derivatives via Chiral Phosphoric Acid Catalysis.

The first catalytic enantioselective construction of chiral THIQUINOL and its derivatives has been accomplished through a chiral phosphoric-acid-catalyzed direct aza-Friedel-Crafts reaction of 3,4-dihydroisoquinolines with 2-naphthols/anthracen-2-ols/phenanthren-9-ol. This method offers a powerful and straightforward synthetic route toward chiral THIQUINOL derivatives with good to excellent yields and enantioselectivities. These structural motifs are crucial chiral components for further transformations into established or potential chiral ligands and catalysis.

Reversible Photochromism for Dynamically Tuning Full‐Color Circularly Polarized Luminescence Toward Multi‐Level Anti‐Counterfeiting Application

AbstractPhotochromic circularly polarized luminescence (CPL) demonstrates broad application prospects in the field of advanced functional materials. However, the current photochromic CPL focuses predominantly on single‐band CPL adjustment, and how to achieve dynamically tunable CPL in multi‐band is still highly challenging. This work reports the success in utilizing reversible photochromism for realizing full‐color CPL emission. Photochromic flexible films are created consisting of triple components: spiropyran (SP) working as photochromic matter, polyurethane (PU) as matrix, and chiral helical polyacetylene as chiral component. Further introducing blue fluorophore 9‐anthracene carboxylic acid (ACA) in the film, blue CPL and red CPL are emitted respectively through selective absorption/transmission and circularly polarized fluorescence energy transfer (CPF‐ET). Doping the photochromic film with diverse fluorophores provides full‐color CPL emission. Adding Zn2+ further intensifies fluorescence and CPL via forming merocyanine (MC)‐Zn2+ complex. Taking advantage of the diverse fluorescence and CPL emission, anti‐counterfeiting, and secondary encryption application of the resulting photochromic CPL materials are demonstrated.

Chiral photon emission from a chiral–achiral perovskite heterostructure

Chiral semiconductors have been recently suggested as the basic building blocks for the design of chiral optoelectronic and electronic devices for chiral emission and spintronics. Herein, we report that through the formation of a chiral/achiral heterostructure, one can develop a chiral system that integrates the merits of both chiral and achiral components for developing a demanded chiral emitter. In the R-(+)-(or S-(−)-)1-(1-naphthyl)-ethylammonium lead bromide/CsPbBr3 heterostructure, we show that the photoluminescence of CsPbBr3 carries a degree of circular polarization of around 1% at room temperature. It is explained that such chiral emission is enabled through the chiral self-trapped exitonic absorption of R-(+)- (or S-(−)-)1-(1-naphthyl)-ethylammonium lead bromide. This work may provide an alternative way to generate bright circularly polarized light from achiral materials, which has potential applications in spintronics, biosensing, and signal encryption.

The Influence of the Molecular Structure of Compounds on Their Properties and the Occurrence of Chiral Smectic Phases.

We have designed new chiral smectic mesogens with the -CH2O group near the chiral center. We synthesized two unique rod-like compounds. We determined the mesomorphic properties of these mesogens and confirmed the phase identification using dielectric spectroscopy. Depending on the length of the oligomethylene spacer (i.e., the number of methylene groups) in the achiral part of the molecules, the studied materials show different phase sequences. Moreover, the temperature ranges of the observed smectic phases are different. It can be seen that as the length of the alkyl chain increases, the liquid crystalline material shows more mesophases. Additionally, its clearing (isotropization) temperature increases. The studied compounds are compared with the structurally similar smectogens previously synthesized. The helical pitch measurements were performed using the selective reflection method. These materials can be useful and effective as chiral components and dopants in smectic mixtures targeted for optoelectronics and photonics.

Discriminatory fluorescence and FRET in the chiral-perovskite/RhB system.

Förster resonance energy transfer (FRET) holds a significant position in various natural and artificial systems, especially within donor-acceptor systems encompassing chiral components. Despite extensive investigations, a clear understanding of the effects of chirality and FRET on discriminatory fluorescence remains elusive. Here, chiral perovskite nanowires (CPNWs) and achiral rhodamine B (RhB) are employed to examine the FRET and discriminatory fluorescence behavior in a donor-acceptor system involving a chiral nanostructure. A notable FRET from the CPNWs to RhB is observed, along with circular dichroism (CD) and circularly polarized luminescence (CPL) activities in RhB. Although the FRET interaction remains consistent over time, a notable inversion in the polarity preference of the CD and CPL of RhB is observed. This reveals that the discriminatory fluorescence of the acceptor arises from the electromagnetic influence of the chiral donor. These findings elucidate that "chirality", as a property related to spatial orientation, cannot accompany the transfer of energy (which is a scalar) from chiral nanostructures to achiral molecules, which helps advance the understanding of the discriminatory fluorescence in the donor-acceptor system with a chiral nanostructure.

Structure Investigation of Mesogenic Homo- and Copolymers Based on Chiral and Achiral Acrylates

The X-ray diffraction method was used to study the structure of mesogenic homo- and copolymers based on chiral and achiral acrylates (disubstituted biphenyl and phenylbenzoate) under the orienting influence of magnetic and (in some cases) electric fields. The analysis of diffraction patterns was carried out in terms of the Hosemann model of a paracrystal using structural modeling and diffraction calculations on models. It was established that chiral and achiral homopolymers form smectic bilayer polar structures, but the structure of the achiral homopolymer possesses weak polarization due to small value of total dipole moment of C=O groups in the side chains. The copolymers (as the chiral homopolymer) form smectic bilayer polar helicoidal structures. The distribution of chiral and achiral components in the layers of the common bilayer depends on their ratios in the copolymer. In turn, this distribution affects both the step of helicoidal structure and the nature of structural-phase transformations in the copolymers. A comparative evaluation of the orientational effects of magnetic and electric fields on the structure of the chiral homopolymer and the copolymers has been carried out. The analysis of the temperature dependences of diffraction and structural parameters of the investigated polymers allowed us to explain some features of their behaviour within seemingly similar (by the type of X-ray patterns) smectic phases.

Odd Cosserat elasticity in active materials.

Stress-strain constitutive relations in solids with an internal angular degree of freedom can be modeled using Cosserat (also called micropolar) elasticity. In this paper, we explore Cosserat materials that include chiral active components and hence odd elasticity. We calculate static elastic properties and show that the static response to rotational stresses leads to strains that depend on both Cosserat and odd elasticity. We compute the dispersion relations in odd Cosserat materials in the overdamped regime and find the presence of exceptional points. These exceptional points create a sharp boundary between a Cosserat-dominated regime of complete wave attenuation and an odd-elasticity-dominated regime of propagating waves. We conclude by showing the effect of Cosserat and odd-elasticity terms on the polarization of Rayleigh surface waves.

Wightman Fields for Two-Dimensional Conformal Field Theories with Pointed Representation Category

Two-dimensional full conformal field theories have been studied in various mathematical frameworks, from algebraic, operator-algebraic to categorical. In this work, we focus our attention on theories with chiral components having pointed braided tensor representation subcategories, namely having automorphisms whose equivalence classes necessarily form an abelian group. For such theories, we exhibit the explicit Hilbert space structure and construct primary fields as Wightman fields for the two-dimensional full theory. Given a finite collection of chiral components with automorphism categories with trivial total braiding, we also construct a local extension of their tensor product as a chiral component. We clarify the relations with the Longo–Rehren construction, and illustrate these results with concrete examples including the U(1)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ extrm{U}}(1)$$\\end{document}-current.

Boryl radical catalysis enables asymmetric radical cycloisomerization reactions.

The development of functionally distinct catalysts for enantioselective synthesis is a prominent yet challenging goal of synthetic chemistry. In this work, we report a family of chiral N-heterocyclic carbene (NHC)-ligated boryl radicals as catalysts that enable catalytic asymmetric radical cycloisomerization reactions. The radical catalysts can be generated from easily prepared NHC-borane complexes, and the broad availability of the chiral NHC component provides substantial benefits for stereochemical control. Mechanistic studies support a catalytic cycle comprising a sequence of boryl radical addition, hydrogen atom transfer, cyclization, and elimination of the boryl radical catalyst, wherein the chiral NHC subunit determines the enantioselectivity of the radical cyclization. This catalysis allows asymmetric construction of valuable chiral heterocyclic products from simple starting materials.