Search Results (214)

Structural symmetry preservation and breaking play important roles in optical manipulation at subwavelength scales. By precisely engineering the symmetry of the nanostructures, metasurfaces can effectively realize various optical functions such as polarization control, wavefront shaping, and on-chip optical integration, with promising applications in information photonics, bio-detection, and flexible devices. In this article, we review the recent advances in chiral and achiral metasurfaces based on symmetry manipulation. We first introduce the fundamental principles of chiral and achiral metasurfaces, including methods for characterizing chirality and mechanisms for phase modulation. Then, we review the research on chiral metasurfaces based on material type and structural dimensions and related applications in high-sensitivity chiral sensing, reconfigurable chiral modulation, and polarization-selective imaging. We then describe the developments in the application of achiral metasurfaces, particularly in polarization-multiplexed holography, phase-gradient imaging, and polarization-insensitive metalenses. Finally, we provide an outlook on the future development of chiral and achiral metasurfaces. Full article

Helical ladder polymers attract attention because of their well-defined, one-handed helical ladder structures and unique properties, which differ from precursor polymers that have random-coil conformations. However, the synthesis of helical ladder polymers is difficult and inhibits their functions and applications. In this study, we reported the synthesis of amphiphilic optically active 2,2′-tethered binaphthyl-embedded helical ladder polymers carrying hydrophilic oligo (ethylene glycol) (OEG) as side chains through quantitative and chemoselective acid-promoted intramolecular cyclization of random-coil precursor polymers. The obtained helical ladder polymers exhibited dramatic circular dichroism (CD) and circularly polarized luminescence (CPL) enhancement. Moreover, we further established a circularly polarized fluorescence-energy transfer (CPF-ET) strategy in which the helical ladder polymers work as a donor, emitting circularly polarized fluorescence to excite an achiral fluorophore (coumarin-6) as the acceptor, producing green CPL with luminescence dissymmetry factor (2.5 × 10⁻⁴). Full article

Intense circularly polarized luminescence is crucial for high-performance electroluminescent, optoelectronic, and photonic devices. This study investigates the magneto-chiral characteristics of two achiral soluble diamagnetic perovskite-type PbQDs. Magnetic fields of 158 and 198 mT are applied using an electromagnet in a toluene solution at 25 °C. Both PbQDs show a magnetic circularly polarized luminescence magnitude of approximately 10⁻³ within the (480 to 580) nm wavelength range. The strength of the magnetic circularly polarized luminescence increases with the intensity of the applied magnetic field. Furthermore, the study demonstrates rapid and reversible switching of the rotation direction of the magnetic circularly polarized luminescence when the magnetic poles are rapidly changed. These results suggest that the direction (right- and left-rotating light) and circular polarization of circularly polarized luminescence (CPL) from circularly polarized perovskites can be alternately and freely controlled by applying an external magnetic field with an appropriate direction and strength. Full article

Broccoli, a highly valued Brassica vegetable, is renowned for its rich content of bioactive substances, including glucosinolates, phenolic compounds, vitamins, and essential minerals. Glucosinolates (GSLs), secondary plant metabolites, are particularly abundant in broccoli. The global consumption of broccoli has increased due to its high nutritional value. This review examines the essential bioactive compounds in broccoli and their biological properties. Numerous in vitro and in vivo studies have demonstrated that broccoli exhibits various biological activities, including antioxidant, anticancer, antimicrobial, anti-inflammatory, anti-obesity and antidiabetic effects. This review analyzes several aspects of the chemical and biological activity of GSLs and their hydrolysis products, isothiocyanates such as sulforaphane, as well as phenolic compounds. Particular emphasis is placed on sulforaphane’s chemical structure, the reactivity of its isothiocyanate fraction (-NCS), and given the different behavior of SFN enantiomers, a wide and detailed review of the chemical synthesis methods described, by microbial oxidation, or using a chiral ruthenium catalyst and more widely using chiral auxiliaries for synthesizing sulforaphane enantiomers. In addition, the methods of chiral resolution of racemates by HPLC are reviewed, explaining the different chiral fillers used for this resolution and a third section on resolution using the formation of diastereomeric complexes and subsequent separation on achiral columns. Additionally, this review highlights the presence of antimicrobial peptides in broccoli, which have shown potential applications in food preservation and as natural alternatives to synthetic antibiotics. The antimicrobial peptides (AMPs) derived from broccoli target bacterial membranes, enzymes, oxidative stress pathways and inflammatory mediators, contributing to their effectiveness against a wide range of pathogens and with potential therapeutic applications. Full article

Ferroelectric liquid crystals (FLCs) are key materials for high-speed electro-optical applications, yet achieving optimal properties over a broad temperature range down below room temperature remains a challenge. This study presents a novel series of systematically designed FLC mixtures, incorporating components with three degrees of chirality—achiral systems, with one center of chirality and with two centers of chirality—to optimize the mesomorphic stability, electro-optical response, and physicochemical properties. The strategic doping by chiral components up to a 0.2 weight fraction extends the temperature range of the ferroelectric phase while lowering the melting temperature. Notably, mixtures containing two chiral centers exhibit shorter helical pitches, while increasing chirality enhances the tilt angle of the director and spontaneous polarization. However, in a mixture containing all three types of chirality (CchM), spontaneous polarization decreases due to opposing vector contributions. Switching time analysis reveals that a system with achiral components and those with two centers of chirality (A-BchM) exhibits the fastest response, while CchM demonstrates only intermediary behavior, caused by its high rotational viscosity. Among all formulations, those containing compounds with two centers of chirality display the most favorable balance of functional properties for deformed helix ferroelectric liquid crystal (DHFLC) applications. One such mixture achieves the lowest melting temperature reported for DHFLC-compatible FLCs, enabling operation at sub-zero temperatures. These findings pave the way for next-generation electro-optical devices with enhanced performance and appropriate environmental stability. Full article

In this paper, we conduct a detailed in silico study of the role of topological features in the electronic transport properties of all-carbon films. To create all-carbon film supercells, we used AA- and AB-stacked bilayer graphene, as well as (5,5), (6,0), (16,0), (12,6), and (8,4) single-walled carbon nanotubes (SWCNTs). For the first time, the simultaneous influence of several topological features on the quantum transport of electrons in graphene–nanotube films are considered. Topological features are understood as the topological type of nanotubes (chiral or achiral), the stacking order in bilayer graphene (AA or AB), and the mutual orientation of bilayer graphene and nanotubes. A characteristic feature of the studied all-carbon films is the presence of electrical conductivity anisotropy. Moreover, depending on the topological features of all-carbon films, the values of electrical resistance can differ by tens of times in different directions of electron transport. The patterns of formation of the profile of the electron transmission function of the studied structural configurations of all-carbon film are established. It is found that the mutual orientation of bilayer graphene and nanotubes plays an important role in the electronic transport properties of all-carbon films. The obtained results make a significant contribution to the understanding of the mechanisms controlling the electrical conductivity properties of all-carbon films at the atomic level. Full article

Several CNN pincer Pd(II) complexes including chiral complexes 1a–e with 2-phenyl-6-(oxazolinyl)pyridines and achiral ones 2a–c with N-substituted-2-aminomethyl-6-phenylpyridines were prepared. In addition, the preparation of the achiral PCN pincer Pd(II) complexes 3a–e with aryl-based phosphinite–imine ligands and chiral 4a–c with aryl-based phosphinite–imidazoline ligands was also performed. Among them, the PCN Pd(II) pincers 3a–e were new complexes and were readily synthesized from commercially available materials in only two steps. The new complexes were characterized through elemental analyses, namely ¹H NMR, ¹³C{¹H} NMR, and ³¹P{¹H} NMR spectroscopies. Furthermore, the molecular structure of complex 3a was determined via X-ray single-crystal diffraction analysis. In the presence of EtAlCl₂, Et₂AlCl, or methylaluminoxane (MAO), the CNN pincer Pd(II) complexes and PCN pincer Pd(II) complexes exhibited excellent activities and monomer conversion rates in norbornene addition polymerization. Surprisingly, the CNN pincer Pd(II) complexes exhibited a higher conversion rate (99.5%) with Et₂AlCl as the cocatalyst, while the PCN pincer Pd(II) complexes showed a higher conversion rate (98.8%) with MAO. Full article

In order to expand the group of chiral thiourea structures, several optically active thioureas derived from the (S)-1-(2-pyridyl)ethylamine enantiomer were prepared via its reaction with achiral or optically active isothiocyanates. To show their synthetic potential as chiral auxiliaries the isolated thioureas were tested as an optically active organocatalyst in the asymmetric version of the selected aldol condensation and addition of diethylzinc to benzaldehyde. The observation of asymmetric induction in these model reactions encourages further research on the use of this group of thioureas in asymmetric versions of multicomponent reactions and cycloadditions. The mechanistic aspects of the reactions under study are also briefly discussed. Full article

Rising global food demand necessitates improved crop yields. Biostimulants offer a potential solution to meet these demands. Among them, antioxidants have shown potential to improve yield, nutritional quality, and resilience to climate change. However, large-scale production of many antioxidants is challenging. Here, we investigate Coenzyme M (CoM), a small, achiral antioxidant from archaea, as a potential biostimulant, investigating its effects on growth and physiology. CoM significantly increased shoot mass and root length of the model plant, Arabidopsis thaliana, in a concentration-dependent manner. Sulfur-containing CoM supplementation restored growth under sulfur-limited conditions in Arabidopsis, whereas similar recovery was not observed for other macronutrient deficiencies, consistent with it being metabolized. In tobacco, CoM increased photosynthetic light capture capacity, consistent with observed growth improvements. Interestingly, this effect was independent of carbon capture rates. Furthermore, CoM promoted early-stage shoot growth in various crops species, including tobacco, basil, cannabis, and soybean. Our results suggest CoM is a promising, scalable biostimulant with potential to modify photosynthesis and enhance crop productivity. Full article

Backgrounds/Objectives: Following previous findings on high-salt (HS)-intake-related increase of oxidative stress, this study explored whether carnosine (CAR; β-alanyl-L-histidine), a reactive oxygen species (ROS) scavenger, enhanced antioxidative defence and vascular function following HS, potentially via the NRF2 or HIF-1α signalling pathway. Methods: Sprague Dawley rats (64, 8–10 weeks old, both sexes) were divided into four groups (n = 6/group): CTRL (0.4% NaCl), HS (4% NaCl for 7 days), CTRL + CAR (0.4% NaCl and 150 mg/kg/day oral CAR supplementation), and HS + CAR (4% NaCl and CAR). Acetylcholine-induced relaxation (AChIR) and hypoxia-induced relaxation (HIR) were evaluated in norepinephrine-precontracted (NE, 10⁻⁷ M) aortic rings. HIR was also tested with NRF2 (ML-385, 5 × 10⁻⁶ M) and HIF-1α (LW6, 10⁻⁴ M) inhibitors. Gene expression of superoxide dismutases 1, 2, and 3 (SOD1, 2 and 3), glutathione peroxidases (GPx1 and 4), catalase (CAT), NRF2, and NAD(P)H dehydrogenase (quinone 1) (NQO1) in aortic tissue was measured by RT-qPCR. Ferric reducing antioxidant power (FRAP) and advanced oxidation protein products (AOPPs) assays were performed on serum samples. All experimental procedures conformed to the European Guidelines (directive 86/609) and were approved by the local and national Ethical Committees (#2158-61-46-23-36, EP355/2022). Results: HS impaired AChIR and HIR, both preserved by CAR. NRF2 and HIF-1α inhibitors suppressed HIR in the HS and HS + CAR groups. CAR significantly increased SOD1 and 2, NRF2, and NQO1 expression and SOD activity compared to the CTRL and HS groups. GPx1 and GPx4 were upregulated in HS + CAR compared to HS. CAR prevented an increase in AOPPs, which were elevated in HS, while FRAP was highest in HS + CAR. Conclusions: Carnosine enhances antioxidative defence by upregulating antioxidant enzymes and activities and preserves vascular relaxation, likely via NRF2 signalling. Full article

Recently, two new polymorphs have been added to the nematic class: the polar-twisted nematic (N_PT) in 2016 and the ferroelectric nematic (N_F) in 2020. Comprised of achiral molecules, both exhibit local polar ordering and adopt modulated structures, right- and left-handed helical organizations—form chirality—albeit on vastly different dimensional scales; modulations have a ~10 nanometer pitch in the N_PT and ~500 nm in the N_F. Here, we focus on the structure and symmetries of the N_PT phase and the ensuing physical properties. Based on an array of order parameters that fully describe the molecular ordering and the nano-modulations thereof, we present a consistent formulation of the dielectric, optical, surface anchoring, and elasticity properties of the N_PT materials. We show that these properties are distinctly different from those associated with an elastically modulated, locally uniaxial, nematic. Full article

The current review provides a focused analysis of the application of capillary electrophoresis (CE) techniques to determine the chiral purity of pharmaceuticals, with a specific emphasis on cyclodextrin- (CD) based chiral selectors (CSs), highlighting advancements, methodologies, and trends in this area as reported in studies published from 2010 to 2024. The review emphasizes CE’s evolution as a critical tool in this field, discussing its advantages, such as high efficiency, flexibility, relatively low costs, and minimal environmental impact, which make it well-suited for modern pharmaceutical applications. Additionally, it underscores the importance of CE in meeting stringent regulatory requirements for chiral drug substances. A significant shift in method optimization has occurred in the last ten years, shifting from the traditional One-Factor-at-a-Time (OFAT) strategy to the Design-of-Experiments (DoE) approach; this shift has enabled more systematic and robust method development. Furthermore, a common trend in recent years is the application of Quality-by-Design (QbD) principles in method development and optimization, ensuring higher reliability and efficiency. Additionally, there is an increasing focus on developing CE methods capable of detecting both achiral and chiral impurities simultaneously, which enhances the comprehensiveness of the analysis. This review seeks to guide future research and development in optimizing CE methodologies for pharmaceutical applications. Full article

An asymmetric synthesis is a favorable approach for obtaining enantiomerically pure substances, but racemic resolution remains an efficient strategy. This study aims to elucidate the chiral resolution of aromatic amino acids and their elution order using glycopeptides as chiral selectors through molecular docking analysis. Chiral separation experiments were conducted using Vancomycin as a chiral additive in the mobile phase (CMPA) at various concentrations, coupled with an achiral amino column as the stationary phase. The Autodock Vina 1.1.2 software was employed to perform molecular docking simulations between each enantiomer (ligand) and Vancomycin (receptor) to evaluate binding affinities, demonstrate enantiomeric resolution feasibility, and elucidate chiral recognition mechanisms. Utilizing Vancomycin as CMPA at a concentration of 1.5 mM enabled the separation of tryptophan enantiomers with a resolution of 3.98 and tyrosine enantiomers with a resolution of 2.97. However, a poor chiral resolution was observed for phenylalanine and phenylglycine. Molecular docking analysis was employed to elucidate the lack of separation and elution order for tryptophan and tyrosine enantiomers. By calculating the binding energy, docking results were found to be in good agreement with experimental findings, providing insights into the underlying mechanisms governing chiral recognition in this system and the interaction sites. This comprehensive approach clarifies the complex relationship between chiral discrimination and molecular architecture, offering valuable information for creating and improving chiral separation protocols. Full article

Three pairs of enantiomers and one achiral molecule that are new ethylated derivatives of sulfur and nitrogen-containing compounds named mantidisamides E–H (1–4), along with twenty known ones (5–24), were derived from the ethanol extract of Tenodera sinensis Saussure. The structures of these new compounds and their absolute configurations were assigned on the basis of spectroscopic analyses and computational methods. The assessment of activities in NRK-52e cells induced by TGF-β1 demonstrated that the previously undescribed compounds 1 and 2 exhibited a significant capacity to inhibit the expression of proteins (fibronectin, collagen I, and α-SMA). Moreover, the biological activity of these compounds was found to increase with rising concentrations. Notably, compounds 1–4 should be artifacts; however, undescribed compounds 1 and 2, which possessed obvious biological activity, might be attractive for chemists and biologists due to the potential for more detailed exploration of their properties. It is worth mentioning that compounds 1 and 2 remain novel structures even in the absence of the ethoxy group. Full article

Loss of the inner blood–retinal barrier (BRB) integrity is a main feature of ocular diseases such as diabetic macular edema. However, there is a lack of clarity on how inner BRB function is modulated within the diabetic retina. The current study examined whether eucalyptol inhibited inner BRB destruction and aberrant retinal angiogenesis in 33 mM glucose-exposed human retinal microvascular endothelial (RVE) cells and db/db mice. This study further examined the molecular mechanisms underlying endothelial dysfunction including retinal endoplasmic reticulum (ER) stress and angiopoietin (Ang)/Tie axis in conjunction with vascular endothelial growth factor (VEGF). Eucalyptol is a naturally occurring monoterpenoid and an achiral aromatic component of many plants including eucalyptus leaves. Nontoxic eucalyptol reduced the production of amyloid-β (Aβ) protein in glucose-loaded RVE cells and in diabetic mice. This natural compound blocked apoptosis of Aβ-exposed RVE cells in diabetic mouse eyes by targeting ER stress via the inhibition of PERK-eIF2α-ATF4-CHOP signaling. Eucalyptol promoted activation of the Ang-1/Tie-2 pathway and dual inhibition of Ang-2/VEGF in Aβ-exposed RVE cells and in diabetic eyes. Supply of eucalyptol reversed the induction of junction proteins in glucose/Aβ-exposed RVE cells within the retina and reduced permeability. In addition, oral administration of eucalyptol reduced vascular leaks in diabetic retinal vessels. Taken together, these findings clearly show that eucalyptol inhibits glucose-induced Aβ-mediated ER stress and manipulates Ang signaling in diabetic retinal vessels, which ultimately blocks abnormal angiogenesis and loss of inner BRB integrity. Therefore, eucalyptol provides new treatment strategies for diabetes-associated RVE defects through modulating diverse therapeutic targets including ER stress, Ang-1/Tie-2 signaling, and Ang-2/VEGF. Full article