Structural Characterization Research Articles

Terminal {Ni(II)-SH} complex promoted anaerobic catalytic sulfur atom transfer reaction: implication to the sulfide oxidase function of Cu/Zn-superoxide dismutase.

In mitochondria, the detoxification of molar excess H2S as polysulfide proceeded via an oxidation process promoted by Cu/Zn containing superoxide dismutase (SOD1) enzyme, which has been very recently reported as the alternative enzyme for cytosolic H2S oxidation. Herein, we present Ni(II) complexes bearing the terminal SH group as a synthetic functional analogue for the sulfide oxidase function of SOD1. Synthesis, crystal structure and complete spectroscopic characterization of two sets of complexes, [NiLOMe/tBu(PPh3)] (2OMe/tBu) and tetraethyl salt of [NiLOMe/tBu(SH)]-1 (3OMe/tBu), were described (LOMe = (E)-2-methoxy-6-(((2-sulfidophenyl)imino)methyl)phenolate and LtBu = (E)-2,4-di-tert-butyl-6-(((2-sulfidophenyl)imino)methyl)phenolate). Under anaerobic conditions, 3OMe/tBu responded to a catalytic sulfur atom transfer (SAT) reaction with PPh3 to produce SPPh3. The SAT reaction was analyzed using detailed studies of 1H and 31P NMR spectra. Finally, the SAT reactivity pattern was compared with the same in the native enzyme of SOD1.

Supramolecular Binding of Phosphonate Dianions by Nanojars and Nanojar Clamshells.

Despite the widespread use of phosphonates (RPO32-) in various agricultural, industrial, and household applications and the ensuing eutrophication of polluted water bodies, the capture of phosphonate ions by molecular receptors has been scarcely studied. Herein, we describe a novel approach to phosphonate binding using chemically and thermally robust supramolecular coordination assemblies of the formula [RPO3⊂{cis-CuII(μ-OH)(μ-pz)}n]2- (Cun; n = 27-31; pz = pyrazolate ion, C3H3N2-; R = aliphatic or aromatic group). The neutral receptors, termed nanojars, strongly bind phosphonate anions by a multitude of hydrogen bonds within their highly hydrophilic cavities. These nanojars can be synthesized either directly from their constituents or by depolymerization of [trans-CuII(μ-OH)(μ-pz)]∞ induced by phosphonate anions. Electrospray-ionization mass spectrometry, UV-vis and variable-temperature, paramagnetic 1H and 31P NMR spectroscopy, single-crystal X-ray diffraction, along with chemical stability studies toward NH3 and Ba2+ ions, and thermal stability studies in solution are employed to explore the binding of various phosphonate ions by nanojars. Crystallographic studies of 12 different nanojars offer unprecedented structural characterization of host-guest complexes with doubly charged RPO32- ions and reveal a new motif in nanojar chemistry, nanojar clamshells, which consist of phosphonate anion-bridged pairs of nanojars and double the phosphonate-binding capacity of nanojars.

Preparation of Zn-Co Bimetallic Catalysts and Their Catalytic Properties for Thermal Decomposition of Ammonium Perchlorate.

This research delves into the preparation of heteronuclear bimetallic catalysts and explores their catalytic properties in the thermal decomposition of ammonium perchlorate (AP). The study's central focus is on enhancing the thermal decomposition characteristics of AP and, consequently, the combustion performance of composite solid propellants. The synthesized materials underwent structural characterization by XRD, XPS, SEM, and FTIR. Catalytic properties were examined using DTA tests. Notably, catalysts derived from calcination at 500 °C exhibited heightened catalytic activity. They advanced the pyrolysis temperature by 135.4 °C and reduced the activation energy by 82.38 kJ/mol compared with pure AP. To further elucidate the decomposition mechanism of AP, the investigation also employed a combined approach involving DSC-TG-FTIR-MS analysis.

Structural, Optical, and Dielectric Characterization of NiO Nanoparticles and Their Integration into PVA/SA Blends for Enhanced Nanocomposite Properties

Structural, Optical, and Dielectric Characterization of NiO Nanoparticles and Their Integration into PVA/SA Blends for Enhanced Nanocomposite Properties

Design, synthesis and activity evaluation of usnic acid monoesterification derivatives.

A new series of usnic acid (UA) monoesterified derivatives 2-15 were designed and synthesised using UA (1) as starting material. The structural characterisation of all compounds was elucidated using 1H-NMR and 13C-NMR spectral data. In vitro studies demonstrated thatmost UA derivatives exhibited higher inhibitory activity against Candida albicans and Staphylococcus aureus. Among them, compound 7 displayed the highest inhibitory activity against C. albicans with a minimum inhibitory concentration (MIC) of 32 μg/mL. Compounds 5, 8, 9, 11and 13 demonstrated superior inhibition of S. aureus (MIC, 16 μg/mL) and biofilm formation in a concentration-dependent manner. With the exception of 11, compounds 5, 8, 9 and 13 were all more effective than UA in inhibiting S. aureus biofilms. This research highlights the potential of UA monoesterified derivatives for the development of dual antimicrobial and antibiofilm agents.

Efficient net transfer-dehydrogenation of glycerol: NNN pincer-Mn and manganese chloride as a catalyst unlocks the effortless production of lactic acid and isopropanol.

Herein, a series of pincer-Mn complexes based on bis(imino)pyridine ligands of the type R2NNN (R = tBu, iPr, Cy and Ph) were synthesized and characterized using various spectroscopic techniques. SCXRD studies revealed a trigonal bipyramidal geometry around the metal center in all the complexes. EPR spectroscopy confirmed the presence of high-spin Mn(II) centers with the consistent observation of sextets in EPR spectra. Additionally, solution magnetic moment measurement exhibited values ranging from 5.8 to 6.2 BM for all the complexes, which are in accordance with the theoretical value of 5.92 BM. HRMS analysis complemented structural characterization, showing fragments corresponding to various solvent adducts and derivatives of the complexes. Subsequently, the synthesized complexes were investigated for their catalytic activity in the transfer dehydrogenation of glycerol to lactic acid in the presence of acetone. Among the considered complexes, the catalyst Ph2NNNMnCl2 was found to be highly efficient. Remarkably, a yield of 92% LA was observed with >99% selectivity at 0.5 mol% loading of Ph2NNNMnCl2 in the presence of 1 equivalent of NaOH at 140 °C in 24 h, surpassing the yield obtained from its precursor MnCl2·4H2O, where a yield of 72% LA was observed with 96% selectivity under similar reaction conditions. This catalytic system was further investigated with a range of acceptors, and good to moderate yields were observed in most cases. Moreover, several control experiments, including reaction with PPh3, CS2 and Hg, highlighted the major involvement of molecular species in the reaction medium. Deuterium labelling studies indicated the involvement of C-H bond activation in the catalytic cycle but not in the rate-determining step (RDS), with a secondary kinetic isotope effect (KIE) of 1.25.

ERAP Inhibitors in Autoimmunity and Immuno-Oncology: Medicinal Chemistry Insights.

Endoplasmic reticulum aminopeptidases ERAP1 and 2 are intracellular aminopeptidases that trim antigenic precursors and generate antigens presented by major histocompatibility complex class I (MHC-I) molecules. They thus modulate the antigenic repertoire and drive the adaptive immune response. ERAPs are considered as emerging targets for precision immuno-oncology or for the treatment of autoimmune diseases, in particular MHC-I-opathies. This perspective covers the structural and biological characterization of ERAP, their relevance to these diseases and the ongoing research on small-molecule inhibitors. We describe the chemical and pharmacological space explored by medicinal chemists to exploit the potential of these targets given their localization, biological functions, and family depth. Specific emphasis is put on the binding mode, potency, selectivity, and physchem properties of inhibitors featuring diverse scaffolds. The discussion provides valuable insights for the future development of ERAP inhibitors and analysis of persisting challenges for the translation for clinical applications.

Scaffold-free development of multicellular tumor spheroids with spatial characterization of structure and metabolic radial profiles

Abstract Purpose In vitro assays are essential for studying cellular biology, but traditional monolayer cultures fail to replicate the complex three-dimensional (3D) interactions of cells in living organisms. 3D culture systems offer a more accurate reflection of the cellular microenvironment. However, 3D cultures require robust and unique methods of characterization. Methods The goal of this study was to create a 3D spheroid model using cancer cells and macrophages, and to demonstrate a custom image analysis program to assess structural and metabolic changes across spheroid microregions. Results Structural characterization shows that cells at the necrotic core show high normalized fluorescence intensities of CD206 (M2 macrophages), cellular apoptosis (cleaved caspase-3, CC3), and hypoxia (HIF-1α and HIF-2α) compared to the proliferative edge, which shows high normalized fluorescence intensities of CD80 (M1 macrophages) and cellular proliferation (Ki67). Metabolic characterization was performed using multiphoton microscopy and fluorescence lifetime imaging (FLIM). Results show that the mean NADH lifetime at the necrotic core (1.011 ± 0.086 ns) was lower than that at the proliferative edge (1.105 ± 0.077 ns). The opposite trend is shown in the A1/A2 ratio (necrotic core: 4.864 ± 0.753; proliferative edge: 4.250 ± 0.432). Conclusion Overall, the results of this study show that 3D multicellular spheroid models can provide a reliable solution for studying tumor biology, allowing for the evaluation of discrete changes across all spheroid microregions.

The Structural Characterization of a Polysaccharide from the Dried Root of Salvia miltiorrhiza and Its Use as a Vaccine Adjuvant to Induce Humoral and Cellular Immune Responses

In order to supplement the research gap concerning Salvia miltiorrhiza polysaccharide extracted from Danshen in NMR analysis, and to clarify its immune enhancement effect as an adjuvant, we isolated and purified SMPD–2, which is composed of nine monosaccharides such as Ara, Gal, and Glc from Danshen. Its weight average molecular weight was 37.30 ± 0.096 KDa. The main chain was mainly composed of →4)-α-D-Galp-(1→, →3,6)-β-D-Glcp-(1→ and a small amount of α-L-Araf-(1→. After the subcutaneous injection of SMPD–2 as an adjuvant to OVA in mice, we found that it enhanced the immune response by activating DCs from lymph nodes, increasing OVA-specific antibody secretion, stimulating spleen lymphocyte activation, and showing good biosafety. In conclusion, SMPD–2 could be a promising candidate for an adjuvant.

Zwitterionic Thiolate-Protected Ag22(0/I) and Ag20(I) Clusters: Assembly, Structural Characterization, and Antibacterial Activity.

Zwitterionic thiolate ligands have the potential to introduce novel assembly modes and functions for noble metal clusters. However, their utilization in the synthesis of silver clusters remains understudied, particularly for the clusters containing reductive Ag(0) species. In this article, we report the first synthesis of a mixed-valence silver(0/I) cluster protected by zwitterionic Tab as thiolate ligands (Tab = 4-(trimethylammonio)benzenethiolate), denoted as [Ag22(Tab)24](PF6)20·16CH3OH·6Et2O (Ag22·16CH3OH·6Et2O), alongside an Ag(I) cluster [Ag20(Tab)12(PhCOO)10(MeCN)2(H2O)](PF6)10·11MeCN (Ag20·11MeCN). Ag22 has a distinct hierarchical supratetrahedral structure with a central {Ag6} kernel surrounded by four [Ag4(Tab)6]4+ units. High-resolution electrospray ionization mass spectra demonstrate that Ag22 has two free electrons, indicating a superatomic core. Ag20 has a drum-like [Ag12(Tab)6(PhCOO)6(H2O)]6+ inner core capped by two tetrahedral-like [Ag4(Tab)3(PhCOO)2(MeCN)]2+ units. Ag20 can be transformed into Ag22 after its reaction with NaBH4 in solution. Antibacterial measurements reveal that Ag22 has a significantly lower minimum inhibitory concentration than that of the Ag20 cluster. This work not only extends the stabilization of silver(0/I) clusters to neutral thiol ligands but also offers new materials for the development of novel antibacterial materials.

A highly effective PANI@(Ce-Er) dual doped ZnO (PCEZ) nanocomposite as UV-light driven photocatalyst for degradation of MB dye: Synthesis and characterization

Abstract Utilizing ecologically friendly methods to address wastewater concerns is paramount. In this study, we developed novel PANI@(Ce-Er) dual-doped ZnO (PCEZ) nanocomposites using a wet impregnation approach assisted by ultrasound. These composites were thoroughly characterized using XRD, FESEM, EDX, UV-DRS, PL, and Impedance Analyzer techniques to assess their structural, optical, and electrical properties. Structural characterization was conducted to analyze the crystalline behavior and chemical composition of the synthesized samples. UV-DRS and PL spectroscopy were utilized to analyze their optical properties. Compared to PANI alone, the PCEZ heterojunction demonstrated enhanced photocatalytic stability and efficiency. Notably, in neutral media, the PCEZ heterojunction exhibited a significant photodegradation efficiency against methylene blue (MB), achieving approximately to 94.14% degradation. Morphology analysis of the synthesized samples and elemental composition was effectively performed using SEM images and EDX data. The UV-DRS investigation aimed to confirm the active contacts of dopant metals with polyaniline backbone chains and assess the energy band gap, which defines the absorption behavior of the photocatalyst. Kinetic studies of methylene blue degradation were characterized using the Pseudo First-Order relation, with the best adjusted R2 value of 0.9947 observed for 50% w/w (PANI@(Ce-Er)-ZnO). The produced PANI@(Ce-Er) co-doped ZnO nanocomposites show promise as effective photocatalysts for the elimination of methylene blue in aqueous environments.

Structural and molecular characterization of astrocyte and vasculature connectivity in the mouse hippocampus and cortex.

The relation of astrocytic endfeet to the vasculature plays a key functional role in the neuro-glia-vasculature unit. We characterize the spatial organization of astrocytes and the structural aspects that facilitate their involvement in molecular exchanges. Using double transgenic mice, we performed co-immunostaining, confocal microscopy, and three-dimensional digital segmentation to investigate the biophysical and molecular organization of astrocytes and their intricate endfoot network at the micrometer level in the isocortex and hippocampus. The results showed that hippocampal astrocytes had smaller territories, reduced endfoot dimensions, and fewer contacts with blood vessels compared with those in the isocortex. Additionally, we found that both connexins 43 and 30 have a higher density in the endfoot and the former is overexpressed relative to the latter. However, due to the limitations of the method, further studies are needed to determine the exact localization on the endfoot. The quantitative information obtained in this study will be useful for modeling the interactions of astrocytes with the vasculature.

How to enable highly efficient and large‐area fabrication on specific textures for monolithic perovskite/silicon tandem solar cells?

AbstractPerovskite/silicon tandem solar cells (PVSK/Si TSCs) have emerged as a promising photovoltaic technology toward achieving a high power conversion efficiency (PCE) along with cost‐effective manufacturing. The PCE of PVSK/Si TSCs has skyrocketed to a certified 33.9%, surpassing the theoretical limit of any single‐junction solar cell. This achievement is partially attributed to advancements in surface textures for Si bottom cells. In this regard, we present an overview of the recent developments concerning surface textures of Si in monolithic PVSK/Si TSCs, including planar, pyramid texture, and nanotexture. Following, the prevailing perovskite deposition methods on these textures are thoroughly discussed, and the corresponding challenges are evaluated. Additionally, we provide a summary of the advanced morphological, structural, optical, and electrical characterization techniques being utilized for theses textures. Finally, the prospects for further development of PVSK/Si TSCs are outlined, including designing novel textures with industrial compatibility, developing perovskite deposition methods with scalability, and exploring more pertinent characterization techniques for textured PVSK/Si TSCs.

Regiocontrol of the Bulk Polymerization of Lysine Ethyl Ester by the Selection of Suitable Immobilized Enzyme Catalysts.

The development of a green and facile method for the controlled synthesis of functional polypeptides is desired for sustainable material applications. In this study, the regioselective synthesis of poly(l-lysine) (polyLys) via enzyme-catalyzed aminolysis was achieved by bulk polymerization of l-lysine ethyl ester (Lys-OEt) using immobilized Candida antarctica lipase Novozym 435 (IM-lipase) or trypsin (IM-trypsin). Structural characterization of the obtained polyLys revealed that IM-lipase resulted solely in ε-linked amide bond formation, whereas IM-trypsin predominantly provided α-linked polyLys. Optimization of the conditions for the bulk polymerization using immobilized enzymes resulted in high monomer conversion and a high degree of polymerization, with excellent regioselectivity. Molecular docking simulations revealed different binding conformations of Lys-OEt to the catalytic pockets of lipase and trypsin, which putatively resulted in different amino moieties being used for amide bond formation. The immobilized enzymes were recovered and recycled for bulk polymerization, and the initial activity was maintained in the case of IM-trypsin. The obtained α- and ε-linked polyLys products exhibited different degradability against proteolysis, demonstrating the possibility of versatile applications as sustainable materials. This enzymatic regioregular control enabled the synthesis of well-defined polypeptide-based materials with a diverging structural variety.

Crystal Structure of Bis(1-butyl-1-methypyrrolidinium) Perthiodicarbonate Complex

Bis(1-butyl-1-methypyrrolidinium) perthiodicarbonate was obtained by the reaction of carbon disulfide with 1-butyl-1-methypyrrolidinium acetate ([BmPyrro][Ac]) in the liquid phase. Structural characterization of this original complex was achieved by single-crystal X-ray diffraction (SCXRD) analysis. The asymmetric unit of the title compound, C2S6·2C9H20N, consisted of two crystallographically 1-methyl-1-butyl pyrrolidinium cations and one perthiodicarbonate anion. The complex C2S6·2C9H20N crystallized in the monoclinic space group, C 2/c, and possessed the following cell parameters: a = 16.0970(10) Å, b = 14.7140(9) Å, c = 12.3280(8) Å, α = 90°, β = 112.3730(12)°, γ = 90°, V = 2700.11 Å3, and Z = 8, Z’ = 0.5.

19F Fast Magic-Angle Spinning NMR Spectroscopy on Microcrystalline Complexes of Fluorinated Ligands and the Carbohydrate Recognition Domain of Galectin-3.

Structural characterization of protein-ligand binding interfaces at atomic resolution is essential for improving the design of specific and potent inhibitors. Herein, we explored fast 19F- and 1H-detected magic angle spinning NMR spectroscopy to investigate the interaction between two fluorinated ligand diastereomers with the microcrystalline galectin-3 carbohydrate recognition domain. The detailed environment around the fluorine atoms was mapped by 2D 13C-19F and 1H-19F dipolar correlation experiments and permitted characterization of the binding interface. Our results demonstrate that 19F MAS NMR is a powerful tool for detailed characterization of protein-ligand interfaces and protein interactions at the atomic level.

Ionic Lignin Polymers for Controlled CO2 Capture, Release, and Conversion into High-Value Chemicals.

In this study, an innovative and cost-effective ionic polymer for CO2 capture and utilization for the first time, using abundant and nonfood-based biomass lignin is reported. The modified ionic polymer synthesizes through the reaction of glycidyltrimethylammonium chloride with lignin under alkaline conditions to yield quaternary ammonium ionic functionality. Subsequently, the hydroxide-based pure ionic lignin polymer is employed for CO2 capture from both direct air and concentrated CO2 sources at room temperature and atmospheric pressure. Structural characterization of the polymers is accomplished through 1H, 13C, and 2D-heteronuclear single quantum coherence (HSQC)NMR, and FT-IR spectroscopy. The CO2 capture process is established through the formation of bicarbonate ions alongside the presence of CO2. The captured CO2 is precisely quantified by using inverse-gated proton decoupled 13C NMR with an internal standard (trioxane). Remarkably, the captured-CO2 amounts of ionic lignin polymer are 1.06mmol g-1 (47mg g-1) from concentrated-CO2 source and 0.60mmol g-1 (26mg g-1) from direct-air. The captured-CO2 in ionic lignin polymer is released in controlled manner and utilized in the synthesis of cyclic carbonate, showcasing the productive application of the captured carbon. Moreover, the fully controlled recovering of ionic lignin polymer achieves via repeated CO2 release ↔ CO2 capture.

Exploring the Health Benefits of Boletus aereus Polysaccharides: Extraction, Structural Characterization, and Antiproliferative Properties against Non-Hodgkin's Lymphomas (NHLs).

Boletus aereus Fr. ex Bull. stands out as a delectable edible mushroom with high nutritional and medicinal values, featuring polysaccharides as its primary nutrient composition. In our continuous exploration of its beneficial substances, a novel polysaccharide (BAPN-1) with a molecular weight of 2279 kDa was prepared. It was identified as a glucan with a backbone composed of the residues →4)-α-Glcp-(1→ and →4,6)-α-Glcp-(1→ connected in a proportion of 5:1 and a β-Glcp-(1→ side residue attached at C6 of the →4,6)-α-Glcp-(1→ residue. Biologically, BAPN-1 exhibited broad-spectrum antiproliferative activities against various NHL cells, including HuT-78, OCI-LY1, OCI-LY18, Jurkat, RL, and Karpas-299, with IC50 values of 0.73, 1.21, 3.18, 1.52, 3.34, and 4.25 mg/mL, respectively. Additionally, BAPN-1 significantly induced cell cycle arrest in the G2/M phase and caused apoptosis of NHL cells. Mechanistically, bulk RNA sequencing and Western blot analysis revealed that BAPN-1 could upregulate cyclin B1 and enhance cleaved caspase-9 expression through the inhibition of FGFR3 and RAF-MEK-ERK signaling pathways. This work supports the improved utilization of B. aereus in high-value health products.

Microwave-assisted synthesis of ZnS@CuInxSy for photocatalytic degradation of coloured and non-coloured pollutants

Copper indium sulfide (CuInS2) exhibits strong visible light absorption and thus has the potential for good photocatalytic activity; however, rapid charge recombination limits its practical usage. An intriguing strategy to overcome this issue is to couple CuInS2 with another semiconductor to form a heterojunction, which can improve the charge carrier separation and, hence, enhance the photocatalytic activity. In this study, photocatalysts comprising CuInS2 with a secondary CuS phase (termed CuInxSy) and CuInxSy loaded with ZnS (termed ZnS@CuInxSy) were synthesized via a microwave-assisted method. Structural and morphological characterization revealed that the ZnS@CuInxSy photocatalyst comprised tetragonal CuInS2 containing a secondary phase of hexagonal CuS, coupled with hexagonal ZnS. The effective band gap energy of CuInxSy was widened from 2.23 to 2.71 as the ZnS loading increased from 0 to 30%. The coupling of CuInxSy with ZnS leads to long-lived charge carriers and efficient visible-light harvesting properties, which in turn lead to a remarkably high activity for the photocatalytic degradation of brilliant green (95.6% in 5 h) and conversion of 4-nitrophenol to 4-nitrophenolate ions (95.4% in 5 h). The active species involved in these photocatalytic processes were evaluated using suitable trapping agents. Based on the obtained results, photocatalytic mechanisms are proposed that emphasize the importance of h+, O2•–, and OH− in photocatalytic processes using ZnS@CuInxSy.

Controlling Triboelectric Charge of MOFs by Leveraging Ligands Chemistry.

Metal-organic frameworks (MOFs) have emerged as promising materials for triboelectric nanogenerators (TENGs), but the effects of ligand choice on triboelectric charge remain underexplored. Hence, this paper demonstrates the effect of single, binary, and ternary ligands on TENG performance of cobalt/cerium-based (Co─Ce) bimetallic MOFs utilizing 2-methylimidazole (2Melm), terephthalic acid (BDC), and benzene tricarboxylic acid (BTC) as ligands. The detailed structural characterization revealed that varying ligand chemistries led to distinct MOF features affecting TENG performance. Single ligand bimetallic MOFs (designated as CoCe-2MeIm, CoCe-BDC, CoCe-BTC) has lower performance than binary ligand (designated as CoCe-2MeIm-BDC, CoCe-2MeIm-BTC, CoCe-BDC-BTC) and ternary ligand MOFs (designated as CoCe-2MeIm-BDC-BTC). Among all, the binary ligand MOF, CoCe-2MeIm-BTC, shows the best results (598V, 26.7µA) due to the combined effect of imidazole ring and (─COO─) groups. This is attributed to lone pairs on nitrogen atoms and a delocalized π-electron system in imidazole system in this material. CoCe-BTC has the lowest results (31V, 3.2µA) due to the bulkier nature of the electron-withdrawing (─COO─) groups and their impact on the π-electron system of the benzene ring. This study showcases the potential of ligand chemistry manipulation to control triboelectric charge and thereby enhance MOF-based TENG performance.