Search Results (194)

Using density functional theory (M06-2X-D3/def2-TZVP), we investigated the 1,2-addition reactions of NH₃ with a series of heavy imine analogues, G13=P-Rea (where G13 denotes a Group 13 element; Rea = reactant), featuring a mixed G13–P–Ga backbone. Theoretical analyses revealed that the bonding nature of the G13=P moiety in G13=P-Rea molecules varies with the identity of the Group 13 center. For G13=B, Al, Ga, and In, the bonding is best described as a donor–acceptor (singlet–singlet) interaction, whereas for G13=Tl, it is characterized by an electron-sharing (triplet–triplet) interaction. According to our theoretical studies, all G13=P-Rea species—except the Tl=P analogue—undergo 1,2-addition with NH₃ under favorable energetic conditions. Energy decomposition analysis combined with natural orbitals for chemical valence (EDA–NOCV), along with frontier molecular orbital (FMO) theory, reveals that the primary bonding interaction in these reactions originates from electron donation by the lone pair on the nitrogen atom of NH₃ into the vacant p-π* orbital on the G13 center. In contrast, a secondary, weaker interaction involves electron donation from the phosphorus lone pair of the G13=P-Rea species into the empty σ* orbital of the N–H bond in NH₃. The calculated activation barriers are primarily governed by the deformation energy of ammonia. Specifically, as the atomic weight of the G13 element increases, the atomic radius and G13–P bond length also increase, requiring a greater distortion of the H₂N–H bond to reach the transition state. This leads to a higher geometrical deformation energy of NH₃, thereby increasing the activation barrier for the 1,2-addition reaction involving these Lewis base-stabilized, heavy imine-like G13=P-Rea molecules and ammonia. Full article

Glycans on the surface of all immune cells are the product of diverse post-translational modifications (glycosylation) that affect almost all proteins and possess enormous structural heterogeneity. Their bioinformational content is decoded by glycan-binding proteins (lectins, GBPs), such as C-type lectins, including selectins, galectins, and Siglecs. Glycans located on the surface of immune cells are involved in many immunological processes through interactions with GBPs. Lectins recognize changes in the glycan epitopes; distinguish among host (self), microbial (non-self), and tumor (modified self) antigens; and consequently regulate immune responses. Understanding GBP–glycan interactions accelerates the development of glycan-targeted therapeutics in severe diseases, including inflammatory and autoimmune diseases and cancer. This review will discuss N- and O-glycosylations and glycosyltransferases involved in the biosynthesis of carbohydrate epitopes and address how interactions between glycan epitopes and GBPs are crucial in immune responses. The pivotal role of the glycan antigen tetrasaccharide sialyl Lewis x in mediating immune and tumor cell trafficking into the extravascular site will be discussed. Next, the role of glycans in modulating bacterial, fungal, viral, and parasitic infections and cancer will be surveyed. Finally, the role of glycosylation in antibodies and carbohydrate vaccines will be analyzed. Full article

Black, needle-like single crystals of [Pd@Bi₁₀][AlCl₄]₄ were synthesized in a one-pot reaction between PdCl₂, Bi, and BiCl₃ at 180 °C in the Lewis acidic ionic liquid (LAIL) medium [BMIm]Cl∙4.2AlCl₄ (BMIm = 1-n-butyl-3-methylimidazolium). Single-crystal X-ray diffraction revealed that the compound crystallizes in the triclinic space group P$\overline{1}$ with the unit cell parameters a = 11.0233(5) Å, b = 26.1892(14) Å, c = 26.2687(14) Å, α = 90.842(2)°, β = 92.1940(10)°, γ = 91.164(2)°, closely matching its platinum-containing analog. The structure features pentagonal antiprismatic [Pd@Bi₁₀]⁴⁺ cluster cations charge-balanced by tetrahedral [AlCl₄]⁻ anions. Bonding and charge analysis reveal unoptimized Pd–Bi and strong Bi–Bi covalent interactions consistent with electronegativity trends and the previously reported host–guest model. Electronic structure calculations performed with the TB-LMTO-ASA program show that [Pd@Bi₁₀][AlCl₄]₄ exhibits semiconducting behavior, suggesting a bandgap opening of 0.71 eV. Full article

This study investigated the therapeutic potential of the nuclear retinoid X receptor (RXR) in mitigating the progression of alpha-synucleinopathies (αSNPs), particularly in Parkinson’s disease (PD). PD-like pathology in mice was successfully induced through the co-delivery of AAV expressing human α-synuclein (αS) and αS preformed fibrils (PFFs) into the substantia nigra pars compacta (SNpc). Significant increases in Lewy body (LB)-like inclusions, loss of tyrosine hydroxylase-positive (TH+) neurons, and reductions in dopamine (DA) levels in the striatum were observed. Additionally, diminished levels of PPARα and NURR1—proteins essential for neuronal survival—along with elevated expression of IBA1 and GFAP, markers of microglial activation and astrocytic gliosis, respectively, are associated with the pathogenesis of Parkinson’s disease. AAV-mediated overexpression of human RXRα demonstrated preservation of TH+ neurons, prevention of DA decline, and attenuation of αS accumulation. Furthermore, RXR-treated PD brains showed a reduced number of GFAP+ and Iba1+ cells, decreased GFAP+ and IBA1+ immunoreactivity, and fewer and less widespread LB-like aggregates. RXR overexpression also enhanced the production of PPARα and NURR1. These findings suggest that RXRα upregulation promotes neuroprotection by mitigating αSNPs and chronic neuroinflammation, a major contributor to PD progression. This research underscores the therapeutic potential of targeting nuclear receptors, such as RXR, in neurodegenerative diseases like PD. Full article

A sustainable and efficient approach for converting carbohydrates into 5-hydroxymethylfurfural (HMF) via heterogeneous catalysis is crucial for effectively utilizing biomass. In this study, we synthesized a series of CrX-polyphenol-formaldehyde resin (PTF) catalysts, which are composites of Cr-doped phenolic-resin-based hydrothermal carbon, using a chelation-assisted multicomponent co-assembly strategy. The performance of the synthesized catalysts was assessed through various analytical techniques, including scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, pyrolysis–Fourier transform infrared spectroscopy, and Brunauer–Emmett–Teller analysis. Cr incorporation into the catalysts enhanced the total and Lewis acidities. Notably, the optimized catalyst, designated as Cr0.6-PTF, achieved an effective glucose conversion into HMF, yielding a maximum of 69.5% at 180 °C for 180 min in a saturated NaCl solution (NaClaq)/dimethyl sulfoxide (2: 18) solvent system. Furthermore, Cr0.6-PTF maintained excellent catalytic activity and a stable chemical structure after nine cyclic reactions, resulting in a 63.8% HMF yield from glucose. This study revealed an innovative approach for utilizing metal-doped phenolic resin hydrothermal carbon to transform glucose into platform chemicals. Full article

This study addresses the dual challenges of water pollution and waste management by exploring the valorization of chicken bone biomass in native (NBio) and calcined (CBio) forms as biosorbents for dye removal. Basic fuchsine (BF) and methylene blue (MB) were selected as model pollutants, and adsorption was assessed under varying operational conditions. Characterization using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD) showed that calcination improved crystallinity, eliminated organic impurities, and increased surface area (247 m²/g for NBio vs. 370 m²/g for CBio). Adsorption tests revealed higher performance for CBio, with maximum adsorption capacities of 100 mg/g (BF) and 142.85 mg/g (MB) based on the Langmuir isotherm, while NBio with maximum adsorption capacities of 111 mg/g (BF) and 111.11 mg/g (MB) followed the Freundlich model. Adsorption kinetics indicated pseudo-second-order behavior, suggesting chemisorption. The possible interactions between dyes and the biosorbent are hydrogen bonding, electrostatic interactions, and Lewis acid–base interactions. Thermodynamic analysis highlighted exothermic behavior for NBio and endothermic, entropy-driven adsorption for CBio, with both processes being spontaneous. A decision tree with Least Squares Boosting (DT_LSBOOST) provided accurate predictions (R² = 0.9999, RMSE < 0.003) by integrating key parameters. These findings promote chicken bone biomass as a cost-effective, sustainable biosorbent, offering promising potential in wastewater treatment and environmental remediation. Full article

This study examined the hierarchical structuring of *BEA zeolite using two distinct approaches: double aluminum removal with solid ammonium hexafluorosilicate (2x-AHFS) and a solution of 0.2 M sodium hydroxide followed by 0.5 M hydrochloric acid (T-NaOH). Additionally, niobium pentoxide (Nb₂O₅) was impregnated at different loadings (5, 10, 15, and 20 wt.%) onto the hierarchized materials. Both treatments increased the SiO₂/Al₂O₃ ratio and produced crystals with domains of about the same size. The hierarchization methods generated secondary mesopores and reduced the micropores in the treated HB zeolite. The solid-state NMR analysis by ²⁷Al and ²⁹Si indicated that the 2x-AHFS treatment increased the hydrophobic character of the zeolite, while the treatment with NaOH/HCl resulted in a less hydrophobic material. A balanced quantity of Brønsted and Lewis sites was observed for all treated zeolites. Thus, these combined physicochemical characteristics of the new catalysts may explain their superior performance in the dehydration reactions. In the case of ethanol dehydration at 230 °C, the 20 wt.% Nb₂O₅ supported on the T-NaOH catalyst produced an 84% conversion and 86% selectivity for ethylene (EE), with 14% diethyl ether (DEE) as the only products. Conversely, in the 1-propanol dehydration reaction, the 20 wt.% Nb₂O₅ supported on 2x-AHFS achieved 99% conversion, producing 99% propene. Full article

The objective of this study was to evaluate the catalytic performance of commercial Nb₂O₅, supplied by CBMM, in the production of biodiesel by transesterification and esterification, using different feedstocks (soybean, corn, sunflower, and waste oils) and both methyl and ethyl routes. For this, the catalyst was characterized in terms of its crystal structure by X-ray diffraction (XRD), specific surface area using the Brunauer–Emmett–Teller (BET) technique, thermal stability by thermogravimetric analysis (TGA), morphology by scanning electron microscopy (SEM), acidity by ammonia desorption at programmed temperature (TPD-NH₃), and catalytic activity by gas chromatography. The results from the structural analyses indicated that Nb₂O₅ has a single monoclinic phase and a morphology consisting of irregular agglomerates. The specific surface area was 1.3 m²/g, and its density was 4.639 g/cm³. The thermogravimetric analysis showed that the material has thermal stability, maintaining its structural integrity up to temperatures as high as 1000 °C. The total acidity reached 301 μmol NH₃/g, indicating the presence of Brønsted and Lewis acidic sites. In catalytic tests, Nb₂O₅ showed higher efficiency in the methyl route, achieving an initial conversion of 96.43% in esters with soybean oil, outperforming other feedstocks. However, catalyst reuse over five cycles revealed a progressive decrease in catalytic activity, possibly due to blocking active sites by adsorbed products, as confirmed by FTIR and XRD analyses conducted on the catalyst. Despite decreased activity after the cycles, the catalyst maintained its crystal structure, indicating structural stability. These results demonstrate the potential of Nb₂O₅ as a heterogeneous catalyst for biodiesel production, particularly with the methyl route and high-quality oils. This study highlights the relevance of Nb₂O₅ in biodiesel synthesis, contributing to sustainable practices and technological advancement in the renewable energy sector. Full article

A simple one-pot reaction of LiAlH₄, AlCl₃, and a secondary amine HNR₂ [R = Et, ⁱPr, ⁱBu, cyclo-C₆H₁₁, (CH₂)₄, and (CH₂)₅] in hydrocarbon solvents results in the formation of exogenous Lewis-base-free amidoalanes [H₂Al(NR₂)]_n (n = 2 or 3) as crystalline solids (35–85% yield). In the solid state (seven X-ray structures), all the amidoalanes exist as dimers, with the exception of the pyrrolidine-derived alane which exists as a trimer. As solids, these amidoalanes exhibit significant kinetic stability towards oxygen/moisture allowing the brief (ca. 5 min.) handling of [H₂Al(NⁱPr₂)]₂ in air. Full article

III-nitrides are crucial materials for solar flow batteries due to their versatile properties. In contrast to the well-studied MOVPE reaction mechanism for AlN and GaN, few works report gas-phase mechanistic studies on the growth of InN. To better understand the reaction thermodynamics, this work revisited the gas-phase reactions involved in metal–organic vapor-phase epitaxy (abbreviated as MOVPE) growth of InN. Utilizing the M06-2X function in conjunction with Pople’s triple-ζ split-valence basis set with polarization functions, this work recharacterized all stationary points reported in previous literature and compared the differences between the structures and reaction energies. For the reaction pathways which do not include a transition state, rigorous constrained geometry optimizations were utilized to scan the PES connecting the reactants and products in adduct formation and XMIn (M, D, T) pyrolysis, confirming that there are no TSs in these pathways, which is in agreement with the previous findings. A comprehensive bonding analysis indicates that in TMIn:NH₃, the In-N demonstrates strong coordinate bond characteristics, whereas in DMIn:NH₃ and MMIn:NH₃, the interactions between the Lewis acid and base fragments lean toward electrostatic attraction. Additionally, the NBO computations show that the H radical can facilitate the migration of electrons that are originally distributed between the In-C bonds in XMIn. Based on this finding, novel reaction pathways were also investigated. When the H radical approaches MMInNH₂, MMIn:NH₃ rather than MMInHNH₂ will generate and this is followed by the elimination of CH₄ via two parallel paths. Considering the abundance of H₂ in the environment, this work also examines the reactions between H₂ and XMIn. The Mulliken charge distributions indicated that intermolecular electron transfer mainly occurs between the In atom and N atom whiling forming (DMInNH₂)₂, whereas it predominately occurs between the In atom and the N atom intramolecularly when generating (DMInNH₂)₃. Full article

A computational study of X-H···Y binary hydrogen-bonded complexes was undertaken to examine the red- and blue-shifting behavior of three model X-H proton donors interacting with a series of Lewis bases: Y = NH₃, NCLi, NCH, NCF, C₂H₂, BF, CO, N₂ and Ne. Two of these proton donors, FArH and F₃CH, have blue-shifting tendencies, while the third, FH, has red-shifting tendencies. A perturbation theory model for frequency shifts that was derived many years ago was employed to partition the predicted frequency shift into the sum of two components, one dependent on the second derivative of the interaction energy with respect to X-H displacement and the other dependent on the X-H bond length change in the binary complex. The predicted shifts were found to be in good agreement with standard ab initio computations, but they were obtained at much lower computational cost. The change in the infrared intensity of the X-H stretching frequency, expressed as a ratio of complex to monomer intensities, was also investigated, along with its relation to the X-H permanent dipole moment derivative and total induced dipole moment derivative with respect to X-H displacement, and used to rationalize the observed infrared intensity changes in the red- and blue-shifted X-H···Y complexes. Full article

A UO₂²⁺ complex bearing N, N, N′, N′-tetraisopropyldiglycolamide (TiPDGA) and two DMF molecules was prepared to explore the catalytic activities of the Lewis-acidic U centre. The cationic complex, [UO₂(TiPDGA)(DMF)₂]²⁺, was obtained as a ClO₄⁻ salt under optimised reaction conditions with an appropriate mixing ratio between UO₂²⁺ and TiPDGA to maintain 1:1 stoichiometry, a non-coordinating ClO₄⁻ counteranion to reserve the coordination sites for substrate activation, and the presence of extra HClO₄ to suppress undesired hydrolysis of UO₂²⁺ competing with the expected complex formation. This UO₂²⁺ complex was characterised by IR, elemental analysis, X-ray crystallography, and ¹H NMR to confirm that the desired [3+1+1] equatorial coordination is actually formed in the solid state and is still maintained even after dissolution in CD₂Cl₂. [UO₂(TiPDGA)(DMF)₂]²⁺ was further subjected to nucleophilic acyl substitution reactions of acid anhydrides to assess its activity and capability as a Lewis-acid catalyst there. Although the observed reaction rates were not very rapid, some characteristic aspects to gain reaction- and substrate-selectivity appeared thanks to the equatorial coordination sphere sterically regulated by the tridentate auxiliary TiPDGA ligand and labile monodentate DMF molecules to activate an acid anhydride after ligand substitution. Full article

A series of homoleptic rare earth (RE) complexes bearing phosphino-aryloxide ligands (1-RE, 2-La) has been prepared. The complexes have been characterised using multinuclear NMR and IR spectroscopy, X-ray crystallography and elemental analysis. Structural characterisation highlighted the different RE–P interactions as a result of differing Lewis acidity and ionic size across the series, hinting at the possibility of FLP-type activity. The potential reactivity of these complexes has been tested by reacting them with small molecules (H₂, CO, CO₂). A series of side-products (3-RE) has also been observed, isolated and characterised, featuring the incorporation of a phosphonium-aryloxide ligand. Full article

Galectins are β-galactoside-binding animal lectins involved in various biological functions, such as host defense. Galectin-2 and -3 are members of the galectin family that are expressed in the stomach, including the gastric mucosa and surface mucous cells. Galectin-3 exhibits aggregation and bactericidal activity against Helicobacter pylori in a β-galactoside-dependent manner. We previously reported that galectin-2 has the same activity under neutral pH conditions. In this study, the H. pylori aggregation activity of galectin-2 was examined under weakly acidic conditions, in which H. pylori survived. Galectin-2 agglutinated H. pylori even at pH 6.0, but not at pH 5.0, correlating with its structural stability, as determined using circular dichroism. Additionally, galectin-2 binding to the lipopolysaccharide (LPS) of H. pylori cultured under weakly acidic conditions was investigated using affinity chromatography and Western blotting. Galectin-2 could bind to H. pylori LPS containing H type I, a Lewis antigen, in a β-galactoside-dependent manner. In contrast, galectin-3 was structurally more stable than galectin-2 under acidic conditions and bound to H. pylori LPS containing H type I and Lewis X. In conclusion, galectin-2 and -3 might function cooperatively in the defense against H. pylori in the stomach under different pH conditions. Full article

4-Nitroquinoline-N-oxide (NQO) and 4-nitropyridine-N-oxide (NPO) are important precursors for the synthesis of substituted heterocycles while NQO is a popular model mutagen and carcinogen broadly used in cancer research; intermolecular interactions are critical for their reactions or functioning in vivo. Herein, the effects of the coordination of N-oxide’s oxygen atom to Lewis acids on multicenter donor–acceptor bonding were explored via a combination of experimental and computational studies of the complexes of NQO and NPO with a typical π-electron donor, pyrene. Coordination with ZnCl₂ increased the positive electrostatic potentials on the surfaces of these π-acceptors and lowered the energy of their LUMO. Analogous effects were observed upon the protonation of the N-oxides’ oxygen or bonding with boron trifluoride. The interaction of ZnCl₂, NPO, or NQO and pyrene resulted in the formation of dark co-crystals comprising π-stacked Zn-coordinated N-oxides and pyrene similar to that found with protonated or (reported earlier) BF₃-bonded N-oxides. Computational studies indicated that the coordination of N-oxides to zinc(II), BF₃, or protonation led to the strengthening of the multicenter bonding of the nitro-heterocycle with pyrene, and this effect was related both to the increased electrostatic attraction and molecular–orbital interactions in their complexes. Full article