Search Results (99)

Adsorption of multicomponent mixtures on solid substrates is essential to numerous technological processes and provides key insights into surface phenomena. Despite advancements in theoretical modeling, many approaches still assume that each adsorbate occupies a single site, thereby neglecting important effects arising from molecules that span multiple adsorption sites. In this work, we broaden the theoretical description of such systems by considering the adsorption of j distinct polyatomic species on triangular lattices. Our approach is based on (i) exact thermodynamic results for polyatomic gases on one-dimensional lattices, extended here to account for substrates with higher coordination numbers, and (ii) the “0D cavity” functional theory originally developed by Lafuente and Cuesta, which reduces to the well-known Guggenheim–DiMarzio model in the limit of rigid rods. As a case study, we explore the behavior of a three-component system consisting of dimers, linear trimers, and triangular trimers adsorbing onto a triangular lattice. This model captures the interplay between structural simplicity, multisite occupancy, configurational diversity, and competition for space, key factors in many practical scenarios involving size-asymmetric molecules. We characterize the system using total and partial isotherms, energy of adsorption, and configurational entropy of the adsorbed phase. To ensure the reliability of our theoretical predictions, we perform Monte Carlo simulations, which show excellent agreement with the analytical approaches. Our findings demonstrate that even complex adsorption systems can be efficiently described using this generalized framework, offering new insights into multicomponent surface adsorption. Full article

In our previous work, we fabricated Ni single-atoms within Beta zeolite (Ni₁@Beta-NO₃⁻) using NiNO₃·6H₂O as a metal precursor without any chelating agents, which exhibited exceptional performance in the selective hydrogenation of furfural. Owing to the confinement effect, the as-encapsulated nickel species appears in the form of Ni⁰ and Ni^δ+, which implies its feasibility in metal catalysis and coordination catalysis. In the study reported herein, we further explored the hydrogen production and olefin oligomerization performance of Ni₁@Beta-NO₃⁻. It was found that Ni₁@Beta-NO₃⁻ demonstrated a high H₂ generation turnover frequency (TOF) and low activation energy (E_a) in a sodium borohydride (NaBH₄) hydrolysis reaction, with values of 331 min⁻¹ and 30.1 kJ/mol, respectively. In ethylene dimerization, it exhibited a high butylene selectivity of 99.4% and a TOF as high as 5804 h⁻¹. In propylene oligomerization, Ni₁@Beta-NO₃⁻ demonstrated high selectivity (75.21%) of long-chain olefins (≥C₆⁺), overcoming the problem of cracking reactions that occur during oligomerization using H-Beta. Additionally, as a comparison, the influence of the metal precursor (NiCl₂) on the performance of the encapsulated Ni catalyst was also examined. This research expands the application scenarios of non-noble metal single-atom catalysts and provides significant assistance and potential for the production of H₂ from hydrogen storage materials and the production of valuable chemicals. Full article

A significant portion of adolescents suffer from mental illnesses and persistent pain due to repeated stress. The components of the nervous system that link stress and pain in early life remain unclear. Prior studies in adult mice implicated the innate immune system, specifically Toll-like receptors (TLRs), as critical for inducing long-term anxiety and pain-like behaviors in social defeat stress (SDS) models. In this work, we investigated the pain and anxiety behavioral phenotypes of wild-type and TLR4-deficient juvenile mice subjected to repeated SDS and evaluated the engagement of TLR4 by measuring dimerization in the spinal cord, dorsal root ganglia, and prefrontal cortex. Male juvenile (4-week-old) mice (C57BL/6J or Tlr4^-/-) underwent six social defeat sessions with adult aggressor (CD1) mice. In WT mice, SDS promotes chronic mechanical allodynia and thermal hyperalgesia assessed via von Frey testing and the Hargreaves test, respectively. In parallel, the stressed WT mice exhibited transient anxiety-like behavior and long-lasting locomotor activity reduction in the open-field test. Tlr4^-/--stressed animals were resistant to the induction of pain-like behavior but had a remnant of anxious behavior, spending less time in the center of the arena. In WT SDS, there were concordant robust increases in TLR4 dimerization in dorsal root ganglia macrophages and spinal cord microglia, indicating TLR4 activation. These results suggest that the chronic pain phenotype and locomotor impairment induced by SDS in juvenile mice depends on TLR4 engagement evidenced by dimerization in immune cells of the dorsal root ganglia and spinal cord. Full article

Background: Chronic wounds, such as diabetic ulcers, often fail to progress through healing due to persistent inflammation, infections, and extracellular matrix (ECM) imbalances. Cathepsin D, an aspartate protease active in acidic environments, plays a pivotal role in wound healing by mediating inflammatory responses, ECM remodeling, and macrophage phenotype transitions. Its dysregulation, however, can impair healing, highlighting the need for targeted modulation of its activity. The aim of this study was to investigate the molecular interaction between Fe²⁺ and cathepsin D’s catalytic core and ionic zipper under physiological and acidic conditions to identify strategies to enhance tissue repair and accelerate the healing of chronic wounds. Methods: The molecular structure of active cathepsin D was obtained from the Protein Data Bank (PDB) and analyzed using UCSF Chimera. Molecular interactions between cathepsin D and ferrous ions (Fe²⁺) were studied, focusing on key residues (D33 and D231) and ionic zipper residues (E5, E180, and D187). Results: Our results showed that the active form of cathepsin D, a 96 kDa dimer, consisted of heterodimers with distinct amino acid chains, where residues D33 and D231 formed the active site, and E5, E180, and D187 constituted the ionic zipper. A functional pocket containing the conserved residues D33 and D231, essential for proteolytic activity, was identified. At physiological pH (~7.5), D33 exhibited the most potent interactions with Fe²⁺, with interaction energies of −7 × 10¹⁷ J at oxygen atoms of the carboxylate group (OD1) and α-carbon (CA) atoms, whereas D231 showed slightly lower energies of −6 × 10¹⁷ J at γ-carbon atom (CG) and CA atoms. At acidic pH (~4), E5 was the primary interacting residue, with the shortest distance to Fe²⁺ (2.69 Å), and showed stable interactions across several atoms, emphasizing its role in metal binding. Conclusions: pH conditions strongly influence the interaction of cathepsin D with Fe². At physiological pH, residues D33 and D231 demonstrate robust and energetically efficient binding with Fe²⁺. At the same time, under acidic conditions, E5 emerges as the primary residue involved, potentially affecting the ionic zipper of cathepsin D. These insights provide a molecular foundation for targeting specific residues to modulate cathepsin D activity, presenting promising opportunities for therapeutic strategies aimed at improving chronic wound healing. Full article

Background/objectives: Ultraviolet-B (UVB) represents a major extrinsic factor in skin cancer development, causing cellular changes that are not yet fully understood. Aquaporins (AQPs) are a family of transmembrane proteins that favor water transport and are involved in several pathways. Nicotinamide (NAM), a vitamin B3 derivate, is a safe molecule able to reduce UVB-induced damages. This study aims to verify whether AQP expression is affected by UVB exposure at different dosages and times and to evaluate NAM’s effects against UVB-induced damages. Methods: A375 cells were exposed to 40, 100, and 200 mJ/cm² UVB doses and analyzed 0, 1, 18, and 24 h post-irradiation. Results: We found that the 40 mJ/cm² UVB dose, 24 h post-irradiation, caused the most detrimental effects an overall overexpression and dimerization of AQPs. However, in the presence of NAM 25 μM, the cell cycle was restored, leading to improved cell viability and proliferation, reduced ROS levels, and reduced DNA damage. Moreover, we found decreased AQPs expression and dimerization. Conclusions: Overall, NAM effectively mitigates UVB-induced cellular damage, including AQPs overexpression, and may serve as a protective agent against UVB-related skin damage. Full article

Background/Objective: Ultraviolet (UV) B radiation leads to DNA damage by generating cyclobutane pyrimidine dimers (CPDs). UVB-induced CPDs can also result in immune suppression, which is a major risk factor for non-melanoma skin cancer (NMSC). UVB-induced CPDs are repaired by nucleotide repair mechanisms (NER) mediated by xeroderma pigmentosum complementation group A (XPA). The purpose of this study was to investigate the use of TH as a chemopreventive agent against the development of skin cancer. Method: SKH-1 hairless mice were exposed were fed with TH (0.1% v/v) for two weeks and exposed to a single dose of UVB (180 mJ/cm²). Dorsal skin was harvested 24 h post-UVB exposure for evaluation of DNA damage and repair. Lymph nodes were also harvested to prepare single cell suspension for flow cytometric evaluation. For carcinogenesis experiments, SKH-1 hairless mice were given TH (0.1% v/v) ad libitum and exposed to UVB (180 mJ/cm²) thrice a week for 30 weeks. Results: Feeding SKH-1 hairless mice with TH (0.1% v/v) for two weeks prior to a single dose of UVB (180 mJ/cm²) led to a significant increase in XPA in skin and DNA repair cytokines IL-12 and IL-23 in draining lymph nodes. Furthermore, when subjected to the photocarcinogenesis protocol; mice fed with TH developed significantly fewer tumors in comparison to mice fed on drinking water. Conclusions: Our data demonstrate that TH has a protective effect against UVB-induced DNA damage, immune suppression, and skin cancer. Future studies will further investigate the potential of TH as a preventive treatment for NMSC. Full article

One undescribed fatty glyceride (1), two unreported N-acetyldopamine dimers (2 and 3), and four known structurally diverse N-acetyldopamine dimers were isolated from adult Vespa velutina auraria Smith. Their structures were elucidated based on a comprehensive analysis of spectroscopic data, HRESIMS, and NMR calculations with ML_J_DP4, and the absolute configurations of 2 and 3 were determined via ECD calculations. Regarding their bioactivities, compounds 5 and 6 can inhibit the production of NO. Moreover, compounds 3, 5 and 7 showed stronger antioxidant activity than the positive control (VC) at 14 μg/mL. A network pharmacology study was used to explore the potential bioactive mechanisms. In addition, a docking study of anti-inflammatory and antioxidative compounds was also performed. Full article

Ethyl maltol was investigated using matrix isolation infrared spectroscopy and DFT calculations. In an argon matrix (14.5 K), the compound was found to exist in a single conformer (form I), characterized by an intramolecular hydrogen bond with an estimated energy of ~17 kJ mol⁻¹. The IR spectrum of this conformer was assigned, and the molecule’s potential energy landscape was explored to understand the relative stability and isomerization dynamics of the conformers. Upon annealing the matrix to 41.5 K, ethyl maltol was found to predominantly aggregate into a centrosymmetric dimer (2× conformer I) bearing two intermolecular hydrogen bonds with an estimated energy of ca. 28 kJ mol⁻¹ (per bond). The UV-induced (λ > 235 nm) photochemistry of the matrix-isolated ethyl maltol was also investigated. After 1 min of irradiation, band markers of two rearrangement photoproducts formed through the photoinduced detachment-attachment (PIDA) mechanism, in which the ethyl maltol radical acts as an intermediate, were observed: 1-ethyl-3-hydroxy-6-oxibicyclo [3.1.0] hex-3-en-2-one and 2-ethyl-2H-pyran-3,4-dione. The first undergoes subsequent reactions, rearranging to 4-hydroxy-4-propanoylcyclobut-2-en-1-one and photofragmenting to cyclopropenone and 2-hydroxybut-1-en-1-one. Other final products were also observed, specifically acetylene and CO (the expected fragmentation products of cyclopropenone), and CO₂. Overall, the study demonstrated ethyl maltol’s high reactivity under UV irradiation, with significant photochemical conversion occurring within minutes. The rapid photochemical conversion, with complete consumption of the compound in 20 min, should be taken into account in designing practical applications of ethyl maltol. Full article

The reactivity of nitrogen oxide, NO, as a ligand in complexes with [Fe2-S2] and [Co2-S2] non-planar rhombic cores is examined by density functional theory (DFT). The cobalt-containing nitrosyl complexes are less stable than the iron complexes because the Co-S bonds in the [Co2-S2] core are weakened upon NO coordination. Various positions of NO were examined, including its binding to sulfur centers. The release of NO molecules can be monitored photochemically. The ability of NO to form a (NO)₂ dimer provides a favorable route of electrochemical reduction, as protonation significantly stabilizes the dimeric species over the monomers. The quasilinear dimer ONNO, with trans-orientation of oxygen atoms, gains higher stability under protonation and reduction via proton–electron transfer. The first two reduction steps lead to an N₂O intermediate, whose reduction is more energy demanding: in the two latter reaction steps the highest energy barrier for Co₂S₂(CO)₆ is 109 kJ mol⁻¹, and for Fe₂S₂(CO)₆, it is 133 kJ mol⁻¹. Again, the presence of favorable light absorption bands allows for a photochemical route to overcome these energy barriers. All elementary steps are exothermic, and the final products are molecular nitrogen and water. Full article

The presented work aimed to explore the potential of oleanolic acid dimers (OADs): their cytostatic and antioxidant activities, molecular docking, pharmacokinetics, and ADMETox profile. The cytostatic properties of oleanolic acid (1) and its 14 synthesised dimers (2a–2n) were evaluated against 10 tumour types and expressed as IC₅₀ values. Molecular docking was performed with the CB-Dock2 server. Antioxidant properties were evaluated with the CUPRAC method. ADMETox properties were evaluated with the ADMETlab Manual (2.0) database. The results indicate that the obtained OADs can be effective cytostatic agents, for which the IC₅₀ not exceeded 10.00 for many tested cancer cell lines. All OADs were much more active against all cell lines than the mother compound (1). All dimers can inhibit the interaction between the 1MP8 protein and cellular proteins with the best results for compounds 2f and 2g with unsaturated bonds within the linker. An additional advantage of the tested OADs was a high level of antioxidant activity, with Trolox equivalent for OADs 2c, 2d, 2g–2j, 2l, and 2m of approximately 0.04 mg/mL, and beneficial pharmacokinetics and ADMETox properties. The differences in the DPPH and CUPRAC assay results obtained for OADs may indicate that these compounds may be effective antioxidants against different radicals. Full article

The benzene dimer (BD) is an archetypal model of π∙∙∙π and C–H∙∙∙π noncovalent interactions as they occur in its cofacial and perpendicular arrangements, respectively. The enthalpic stabilization of the related BD structures has been debated for a long time and is revisited here. The revisit is based on results of computations that apply the coupled-cluster theory with singles, doubles and perturbative triples [CCSD(T)] together with large basis sets and extrapolate results to the complete basis set (CBS) limit in order to accurately characterize the three most important stationary points of the intermolecular interaction energy (ΔE) surface of the BD, which correspond to the tilted T-shaped (TT), fully symmetric T-shaped (FT) and slipped-parallel (SP) structures. In the optimal geometries obtained by searching extensive sets of the CCSD(T)/CBS ΔE data of the TT, FT and SP arrangements, the resulting ΔE values were −11.84, −11.34 and −11.21 kJ/mol, respectively. The intrinsic strength of the intermolecular bonding in these configurations was evaluated by analyzing the distance dependence of the CCSD(T)/CBS ΔE data over wide ranges of intermonomer separations. In this way, regions of the relative distances that favor BD structures with either π∙∙∙π or C–H∙∙∙π interactions were found and discussed in a broader context. Full article

Non-alcoholic fatty liver disease (NAFLD) has emerged as the leading cause of chronic liver disease worldwide. Caspase 8 and FADD-like apoptosis regulator (CFLAR) has been identified as a potent factor in mitigating non-alcoholic steatohepatitis (NASH) by inhibiting the N-terminal dimerization of apoptosis signal-regulating kinase 1 (ASK1). While arginine methyltransferase 1 (PRMT1) was previously reported to be associated with increased hepatic glucose production, its involvement in hepatic lipid metabolism remains largely unexplored. The interaction between PRMT1 and CFLAR and the methylation of CFLAR were verified by Co-IP and immunoblotting assays. Recombinant adenoviruses were generated for overexpression or knockdown of PRMT1 in hepatocytes. The role of PRMT1 in NAFLD was investigated in normal and high-fat diet-induced obese mice. In this study, we found a significant upregulation of PRMT1 and downregulation of CFLAR after 48h of fasting, while the latter significantly rebounded after 12h of refeeding. The expression of PRMT1 increased in the livers of mice fed a methionine choline-deficient (MCD) diet and in hepatocytes challenged with oleic acid (OA)/palmitic acid (PA). Overexpression of PRMT1 not only inhibited the expression of genes involved in fatty acid oxidation (FAO) and promoted the expression of genes involved in fatty acid synthesis (FAS), resulting in increased triglyceride accumulation in primary hepatocytes, but also enhanced the gluconeogenesis of primary hepatocytes. Conversely, knockdown of hepatic PRMT1 significantly alleviated MCD diet-induced hepatic lipid metabolism abnormalities and liver injury in vivo, possibly through the upregulation of CFLAR protein levels. Knockdown of PRMT1 suppressed the expression of genes related to FAS and enhanced the expression of genes involved in FAO, causing decreased triglyceride accumulation in OA/PA-treated primary hepatocytes in vitro. Although short-term overexpression of PRMT1 had no significant effect on hepatic triglyceride levels under physiological conditions, it resulted in increased serum triglyceride and fasting blood glucose levels in normal C57BL/6J mice. More importantly, PRMT1 was observed to interact with and methylate CFLAR, ultimately leading to its ubiquitination-mediated protein degradation. This process subsequently triggered the activation of c-Jun N-terminal kinase 1 (JNK1) and lipid deposition in primary hepatocytes. Together, these results suggested that PRMT1-mediated methylation of CFLAR plays a critical role in hepatic lipid metabolism. Targeting PRMT1 for drug design may represent a promising strategy for the treatment of NAFLD. Full article

222 nm far-ultraviolet (F-UV) light has a bactericidal effect similar to deep-ultraviolet (D-UV) light of about a 260 nm wavelength. The cytotoxic effect of 222 nm F-UV has not been fully investigated. DLD-1 cells were cultured in a monolayer and irradiated with 222 nm F-UV or 254 nm D-UV. The cytotoxicity of the two different wavelengths of UV light was compared. Changes in cell morphology after F-UV irradiation were observed by time-lapse imaging. Differences in the staining images of DNA-binding agents Syto9 and propidium iodide (PI) and the amount of cyclobutane pyrimidine dimer (CPD) were examined after UV irradiation. F-UV was cytotoxic to the monolayer culture of DLD-1 cells in a radiant energy-dependent manner. When radiant energy was set to 30 mJ/cm², F-UV and D-UV showed comparable cytotoxicity. DLD-1 cells began to expand immediately after 222 nm F-UV light irradiation, and many cells incorporated PI; in contrast, PI uptake was at a low level after D-UV irradiation. The amount of CPD, an indicator of DNA damage, was higher in cells irradiated with D-UV than in cells irradiated with F-UV. This study proved that D-UV induced apoptosis from DNA damage, whereas F-UV affected membrane integrity in monolayer cells. Full article

A new dimeric C-glycoside polyketide chrysomycin F (1), along with four new monomeric compounds, chrysomycins G (2), H (3), I (4), J (5), as well as three known analogues, chrysomycins A (6), B (7), and C (8), were isolated and characterised from a strain of Streptomyces sp. obtained from a sediment sample collected from the South China Sea. Their structures were determined by detailed spectroscopic analysis. Chrysomycin F contains two diastereomers, whose structures were further elucidated by a biomimetic [2 + 2] photodimerisation of chrysomycin A. Chrysomycins B and C showed potent anti-tuberculosis activity against both wild-type Mycobacterium tuberculosis and a number of clinically isolated MDR M. tuberculosis strains. Full article

New iron and cobalt bis(dithiolene) complexes [M(3cbdt)₂] (3cbdt = 3-cyanobenzene-1,2-dithiolate) were prepared as tetraphenylphosphonium (Ph₄P⁺) salts for Fe in the monoanionic state and for Co in both the dianionic and monoanionic states: (Ph₄P)₂[Fe(III)(3cbdt)₂]₂ (1); (Ph₄P)₂[Co(III)(3cbdt)₂]₂ (2); (Ph₄P)₂[Co(II)(3cbdt)₂] (3). These compounds were characterized by single-crystal X-ray diffraction, cyclic voltammetry, EPR, and static magnetic susceptibility. Their properties are discussed in comparison with the corresponding complexes based on the isomer ligand 4-cyanobenzene-1,2-dithiolate (4cbdt) and 4,5-cyanobenzene-1,2-dithiolate (dcbdt), previously described by us. The Fe(III) and the Co(III) compounds (1 and 2) are isostructural, crystallizing in the triclinic $P\overline{1}$ space group, with cis [M(III)(3cbdt)₂] complexes dimerized in a trans fashion, and the transition metal (M = Fe, Co) has a distorted 4+1 square pyramidal coordination geometry. The Co(II) compound (3) crystallizes in the triclinic $P\overline{1}$ space group, with the unit cell containing one cis and three trans inequivalent [Co(II)(3cbdt)₂] complexes with the transition metal (Co) and having a square planar coordination geometry. The Fe(III) complex (1) is EPR-silent, and the static magnetic susceptibility shows a temperature dependence typical of dimers of antiferromagnetically coupled S = 3/2 spins with −J/k_B = 233.6 K and g = 1.8. Static magnetic susceptibility measurements of compound (3) show that this Co(II) complex is paramagnetic, corresponding to an S = ½ state with g = 2, in agreement with EPR spectra showing in solid state a hyperfine structure typical of the I(⁵⁹Co) = 7/2. Static susceptibility measurements of Co(III) complex (2) showed an increase in the paramagnetic susceptibility upon warming above 100 K, which is consistent with strong AFM coupling between dimerized S = 1 units with a constant −J/k_B ~1286 K. Full article