Stable Complex Research Articles

Adaptation strategies of soil microorganisms in resource changes and stoichiometric imbalances induced by secondary succession on the loess plateau

Sequestering farmland for secondary succession is an effective method of restoring ecosystem services to degraded farmland, but long-term secondary succession often alters ecosystem environments, resources, and substrate stoichiometry. Currently, it is not known how resource changes and stoichiometric imbalances due to secondary succession affect soil microbial community structure and function, hindering our understanding of the natural resilience for degraded ecosystems. Here, we assessed nutrient limitation elements, community structure, metabolic functions, co-occurrence network complexity, and community stability of soil microorganisms during secondary succession of abandoned farmlands on the Loess Plateau. Results showed that secondary succession significantly altered plant characteristics and soil properties, as well as causing stoichiometry imbalances in nutrient resources. Along the secondary succession chronosequence, microbial nutrient metabolism shifted from phosphorus (P) limitation to carbon (C) and nitrogen (N) co-limitation. Microbial diversity, eutrophic flora, plant growth-promoting bacteria, and metabolism functional groups increased significantly during the 20 years after the abandonment of the farmlands, but decreased significantly with long-term succession. However, oligotrophic flora and P-solubilizing bacteria became dominant after 30 years of secondary succession on abandoned farmlands. The topological features of microbial co-occurring networks, including nodes, degree, closeness, betweenness, and eigenvector complexity, natural connectivity, and community stability first increased and then decreased with secondary succession. Correlation and random forest analyses indicated that secondary succession-induced stoichiometry imbalances in C:N and N:P, as well as changes in soil organic C and lignin phenols, were the key factors influencing microbial community structure and function. Overall, these results enhance our understanding of the adaptation strategies of soil microbial communities in ecologically managed regions to changes in ecosystem resources and stoichiometric imbalances.

Five novel Pb/Zn/Co metal-organic frameworks using 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene and carboxylate ligands: Synthesis, characterization, DFT calculation and catalytic PMS degradation of RhB

Five new metal-organic frameworks (MOFs), namely {Pb(atpt)(3-bpd)0.5}n (1); {Co(cbz)2(3-bpd)(H2O)2·2H2O}n (2); {Co(imdc)(3-bpd)(H2O)·H2O}n (3); {Co(tdca)(3-bpd)(H2O)2·DMF}n (4); {Zn(tdca)(3-bpd)(H2O)2·DMF}n (5), were assembled with metal ions Pb²⁺, Zn²⁺, and Co²⁺ using 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene (3-bpd) as the main ligand, combined with 2-aminoterephthalic acid (H2atpt), 4-cyanobenzoic acid (Hcbz), 4,5-imidazoledicarboxylic acid (H2imdc), and thiophene-2,5-dicarboxylic acid (H2tdca) as auxiliary ligands via hydro/solvothermal methods. Their molecular structures were analyzed by single-crystal X-ray diffraction and characterized by FT-IR and PXRD. Complex 1 has a three-dimensional structure with a hepta-coordinated, semi-directed {PbNO6} metal center. The central metal ions in complexes 2–5 exhibit a six-coordinated {MN2O4} (M = Co or Zn) octahedral geometry. In complex 2, the carboxylate ligand does not function as a bridging ligand, resulting in a 1D chain structure, while complexes 3- 5 extend into 2D layered structures. Thermogravimetric analysis indicates good thermal stability for complexes 1–5. Then, the prepared complexes were used as catalysts to degrade Rhodamine B (RhB) during the monopersulfate (PMS) activation. Complexes 3 and 4 demonstrated significant efficiency, achieving degradation rates of 93.61 % and 98.56 % within 10 min. Radical scavenging experiments and EPR analysis identified that the activation of PMS for dye degradation by the two catalysts occurs through both radical and non-radical pathways, with SO4•− and •OH radicals being the dominant species. Density functional theory (DFT) calculations explained the superior catalytic performance of complex 4 compared to complex 3.

Interfacial structure modification and enhanced emulsification stability of microalgae protein through interaction with anionic polysaccharides

Microalgae protein (MP) have emerged as a focal point of research within food processing due to its nutritional value and foaming properties. However, its isoelectric point around pH 4 leads to it susceptible to collision, binding, and precipitation. Additionally, MP has poor emulsification properties and only shows stability under strongly alkaline conditions. This study investigated the effects of food-grade anionic polysaccharides (guar gum (GG), gum arabic (GA), low acyl gellan gum (LG), and pectin (PT)) on the molecular structure and emulsification properties of MP. Results indicated that these anionic polysaccharides enhanced the UV absorption of MP near 620 nm, especially at 14 % content, while fluorescence intensity decreased due to amino acid residues masking without structural changes. The addition of polysaccharides resulted in bimodal or multimodal particle size distributions, with LG and PT showing larger particle sizes. At pH 4, negatively charged polysaccharides formed stable complexes with near-neutral MP, improving solution stability via electrostatic repulsion and diminishing turbidity. The droplet distribution analysis indicated that higher anionic polysaccharide ratios (1:4, 1:2, and 1:1) correlated with smaller droplet sizes and increased emulsion stability. Zeta-potential measurements revealed negative charges for emulsions, with LG-MP and PT-MP complexes displaying higher absolute values (15.0 to 20.7 mV) compared to GG-MP and GA-MP complexes, indicating superior stability. Storage stability analysis showed that LG-MP and PT-MP complexes stabilized emulsions had minimal delamination over two weeks. Rheological assessments showed that increasing GG and GA contents from 14 % to 50 % had negligible effects on apparent viscosity, while LG-MP (1:1) complexes stabilized emulsion displayed higher viscosity compared to PT-MP emulsions. Frequency sweep results showed that GG-MP, GA-MP, and LG-MP emulsions had greater elastic moduli (G') than viscous moduli (G"), indicating elastic behavior, whereas PT-MP emulsions transitioned from liquid-like to solid-like behavior as frequency increased. This study illustrates the advantages of high LG and PT content in preventing particle aggregation and enhancing emulsion stability, providing a theoretical and practical foundation for MP applications in food processing.

Biophysical insight into the interaction mechanism of 4-bromo-N-(thiazol-2- yl)benzenesulfonamide and human serum albumin using multi-spectroscopic and computational studies

4-Bromo-N-(thiazol-2-yl)benzenesulfonamide (1) is enriched with bioactive components and is highlighted for its pharmacological properties. However, its pharmacokinetic characteristics are yet to be reported. The interaction of compound 1 with carrier proteins in the bloodstream is an important factor that affects its potential therapeutic efficacy. This study aimed to elucidate the pharmacokinetic mechanisms of compound 1 in relation to human serum albumin (HSA) using multi-spectroscopic and computational techniques. Its predicted drug-like properties revealed no mutagenicity, although potential hepatotoxicity and interactions with certain cytochrome P450 enzymes were observed. Spectroscopic analyses extensively provided the interaction between HSA and 1 through a static fluorescence quenching mechanism with spontaneous hydrophobic interactions and hydrogen bonding. The binding constant of the HSA‒1 complex was relatively moderate to strong at a level of 106 M−1. Various spectroscopic techniques including ultraviolet-visible, Fourier-transform infrared, and circular dichroism spectroscopies indicated that its binding induced alteration in the α-helix content of HSA. Competitive binding and molecular docking studies designated the preferential binding of 1 to sub-structural domain IIA binding site I of HSA. Molecular dynamic simulations further illustrated the formation of a stable complex between 1 and HSA, accompanied by conformational changes in the protein. Importantly, esterase capacity of the HSA‒1 complex increased compared to the free HSA. Therefore, elucidation of the HSA‒1 binding mechanism provides valuable insights into the pharmacokinetics, suggesting potential benefits for the further development of 1 as a therapeutic agent.

Electrochemical activation of periodate with graphite electrodes for degradation of high concentrations of thiocyanogen (SCN−) in mineral processing tail liquid

Cyanide has been widely used in gold extraction due to its cost-effectiveness, high selectivity and recovery. Regrettably, its wide application also leads to the presence of a large amount of thiocyanogen (SCN−) in the tail liquid of mineral processing plants, which affects the quality of the effluent water, and thus poses a threat to the ecological environment and human health. This paper investigates the degradation of high concentration of SCN− in water using electrochemical oxidation/periodate (E-GP/PI) system. A degradation rate of 90.25 % of SCN− was achieved by optimising various operating parameters. The effects of organic matter and typical heavy metal ion concentrations on the degradation of SCN− were investigated, and it was found that Cu2+ was able to promote the degradation of SCN− through the formation of stable complexes with SCN−, which enhanced the degradation rate to 96.48 %. However, the presence of Octadecyltrimethylammonium bromide (OTAB) and butylxanthin hindered the degradation process, where 500 mg/L of OTAB reduced the degradation rate of SCN− to 80.88 %, while 100 mg/L of butylxanthin reduced the degradation rate to 78.66 %. On this basis, experiments were carried out using real wastewater samples and SCN− degradation efficiencies of about 90 % were obtained. Afterwards, through electron paramagnetic resonance analysis, free radical burst, ion chromatograph and other research techniques, IO3 and O2– were obtained as the main drivers of SCN− degradation and SCN− degradation pathways were elucidated. Finally, the E-GP/PI system was shown to be effective in reducing the ecotoxicity of SCN− by increasing the 24-h LC50 from 12.5 % to 48.5 % in a toxicity test with daphnia. This study provides a new idea for the green and efficient treatment of SCN− rich beneficiation tail liquid.

Preparation of cellulose nanofiber/polyvinyl alcohol-based composite films for metal ion detection by starch/disodium calcium ethylenediaminetetraacetate synergistic complexation effect

Heavy metal pollution causes irreversible damage to plants, animals, and humans. Therefore, it is meaningful to develop facile, fast, and efficient strategies for heavy metal ion (HMI) detection. Here, a portable composite film (CPSE) was designed for HMI detection with high sensitivity and wide detection range. The CPSE was prepared by using cellulose nanofibers (CNF)/polyvinyl alcohol (PVA) as the matrix and utilizing modified starch (HPS) to assist disodium calcium ethylenediaminetetraacetate (EDTA-Ca) to form stable complexes with HMI. The R, G and B values (the three primary colors of light) were captured using an image acquisition system to produce an HMI standard color card successfully. Specifically, the composite film can effectively distinguish Cu2+, Pb2+ and Fe3+. The response time of the composite film to HMI was 2–4 s, and the detection ranges of Cu2+ and Fe3+ were 5–700 ppm and 10–1000 ppm, respectively. Additionally, the synergistic effect of HPS and EDTA-Ca led to the increase in tensile strength (1.59–1.71 times), tear strength (3.29–3.57 times), and glass transition temperature (~ 6 °C) compared to CNF/PVA/HPS and CNF/PVA/EDTA-Ca films. This study confirms the value of CPSE films as materials for HMI detection and suggests innovative ideas for designing similar biomass detection materials in the future.

Discovery of a New Isatin Scaffold for BCR‐ABL Tyrosine Kinase Inhibitors Using a Comprehensive Computational Approach

AbstractInserting Isatin (1H indole 2,3‐dione) stands out as an exceptionally captivating element in the realm of drug design and development. Hence, there has been a notable focus in numerous anticancer studies on investigating the potential of various derivatives of Isatin (1H indole 2,3‐dione), including imines, hydrazones, thiosemicarbazones, and other compounds. Therefore, to develop new compounds with anticipated high activity, a novel series of 40 Isatin derivatives have undergone 3D‐QSAR studies as potent anticancer agents against the leukemia cell line (K562). This approach has been pursued due to the significant importance placed on exploring the potential of these derivatives. Through the analysis of graphical contour maps, the generated models yielded favorable statistical outcomes and provided valuable insights into the structural elements that exert a significant influence on the activity. Furthermore, both CoMFA and CoMSIA models have shown suitable reliabilities (q2 = 0.689, 0.772, respectively) and predictive abilities (r2pred = 0.780, 0.892, respectively). As a result, the design of five new compounds (T1–T5) based on the Isatin moiety, which exhibited remarkable inhibitory activity, has successfully been accomplished. Accordingly, molecular docking and molecular dynamics (MD) simulations of 100 ns have been utilized to examine the interaction mechanism and conformational changes of the newly designed compounds at the binding site of BCR‐ABL tyrosine kinase. MD simulation revealed that both compounds T1 and T2 formed stable complexes with BCR‐ABL. Additionally, the assessment of the in‐silico pharmacokinetic parameters indicates favorable ADMET properties. These findings hold promise for the future development of potent BCR‐ABL tyrosine kinase inhibitors.

In-silico Studies, Synthesis, and Antacid Activities of Magnesium (II) Complexes.

Nowadays, acidity is a severe problem worldwide caused by excessive gastric acid secretion by the stomach and proximal intestine. Antacids are drugs capable of buffering stomach acid. Therefore, in our research work, we have reported the in-silico studies, synthesis, characterization, and evaluation of antacid activities of magnesium (II) complexes via the acid-base neutralization process. In this research, some magnesium complexes were synthesized and their antacid behavior was compared with marketed products. Also, in-silico studies were performed on H+/K+ ATPase (Proton pump). All synthesized compounds were characterized by various spectroscopic techniques like UV-Vis, FT-IR, XRD, and DSC techniques. Spectroscopic analysis results showed that the semicarbazone ligand shows keto-enol isomerism and forms a coordinated stable complex with magnesium ions in the crystalline phase. The FT-IR results confirmed the presence of Mg-O stretching, N-H bending, and C=N stretching vibrations in Mg (II) complexes. The antacid activities of Mg (II) complexes were excellent as compared to the semicarbazone ligand and comparable with that of marketed antacid drugs like ENO, and Pantop-D. Insilco studies also confirmed that semicarbazone ligand and its Mg (II) complexes were both found to be fitted into the active sites of molecular targets, and Mg (II) complexes showed better binding affinities towards macromolecular as compared to semicarbazone ligand.

Novel 5-Fluorouracil analogues versus perfluorophenyl ureas as potent anti-breast cancer agents: Design, robust synthesis, in vitro, molecular docking, pharmacokinetics ADMET analysis and dynamic simulations

To investigate the therapeutic potential of 5-Fluorouracil-based analogues, a straightforward synthetic technique was employed to synthesize a novel series of 5-arylurea uracil derivatives (AUFU01-03) and aryl-urea derivatives bearing perfluorophenyl (AUPF01-03). Reliable tools such as infrared (IR), Nuclear Magnetic Resonance (NMR) spectra, and elemental analyses were utilized to confirm the chemical structures and purity of these compounds. In comparison to healthy noncancerous control skin fibroblast cells (BJ-1), we examined the antiproliferative efficacy of compounds (AUFU01-03) and (AUPF01-03) against specific human malignant cell lines of the breast (MCF-7), and colon (HCT-116). Based on the MTT experiment results, compounds AUFU03 and AUPF01-03 possessed highly cytotoxic effects. Among these, cytotoxicity was demonstrated by compounds AUPF01-03 with IC50 values (AUPF01, IC50 = 167 ± 0.57 µM, AUPF02, IC50 = 23.4 ± 0.68 µM and AUPF03, IC50 = 28.8 ± 1.13 µM, respectively, on MCF-7), relative to 5-Fluorouracil as reference drug (IC50 = 160.7 ± 0.22 µM). Compound AUPF01 showed safety on BJ-1 cells up to a concentration of 100 µM (% cytotoxicity = 3.9 ± 0.42 %), so AUPF01 was selected for further studies. At the gene, the expression levels of BCL-2 gene were decreased significantly in MCF-7 + 5-FU and reached the lowest level in MCF-7 + AUPF01. In contrast, the expression levels of pro-apoptotic genes (p53 and BAX) were increased in MCF-7 + 5-FU, and reached a significantly higher level in MCF-7 + AUPF01. Apoptosis/necrosis assays demonstrated that AUPF01 induced S and G2/M phase cell cycle arrest in MCF-7 cells. Moreover, the efficacy of these compounds against anti-cancer protein receptors was assessed using molecular docking. The results indicated that compound AUPF01 exhibited high binding energies, effectively interacting with the active sites of crucial proteins such as EGFR, CDK2, ERalfa, BAX1, BCL2, and P53. These interactions involved a diverse range of chemical bonding types, suggesting the potential of these substances to inhibit enzyme activities. Moreover, computational ADMET analyses of these compounds demonstrated compliance with Lipinski’s criteria, indicating favorable physicochemical properties. Additionally, molecular dynamics (MD) simulations revealed stable complexes of AUPF01 with EGFR, CDK2, ERalfa, BAX1, BCL2, and P53, as evidenced by (RMSD) values, RMSF values, and (SASA) values for the respective complexes.

STK19 drives transcription-coupled repair by stimulating repair complex stability, RNA Pol II ubiquitylation, and TFIIH recruitment

STK19 drives transcription-coupled repair by stimulating repair complex stability, RNA Pol II ubiquitylation, and TFIIH recruitment

Determination of Binding Constants and Gas Phase Stabilities of Artificial Carbohydrate Receptor Complexes Using Electrospray Mass Spectrometry

Determination of Binding Constants and Gas Phase Stabilities of Artificial Carbohydrate Receptor Complexes Using Electrospray Mass Spectrometry

Probing Noncovalent Interaction Strengths of Host-Guest Complexes Using Negative Ion Photoelectron Spectroscopy.

Noncovalent interactions (NCIs) are crucial for the formation and stability of host-guest complexes, which have wide-ranging implications across various fields, including biology, chemistry, materials science, pharmaceuticals, and environmental science. However, since NCIs are relatively weak and sensitive to bulk perturbation, direct and accurate measurement of their absolute strength has always been a significant challenge. This concept article aims to demonstrate the gas-phase electrospray ionization (ESI)-negative ion photoelectron spectroscopy (NIPES) as a direct and precise technique to measure the absolute interaction strength, probe nature of NCIs, and reveal the electronic structural information for host-guest complexes. Our recent studies in investigating various host-guest complexes that involve various types of NCIs such as anion-π, (di)hydrogen bonding, charge-separated ionic interactions, are overviewed. Finally, a summary and outlook are provided for this field.

KCNB1-Leptin receptor complexes couple electric and endocrine function in the melanocortin neurons of the hypothalamus.

The neurons of the melanocortin system regulate feeding and energy homeostasis through a combination of electrical and endocrine mechanisms. However, the molecular basis for this functional heterogeneity is poorly understood. Here, a voltage-gated potassium (Kv+) channel named KCNB1 (alias Kv2.1) forms stable complexes with the leptin receptor (LepR) in a subset of hypothalamic neurons including proopiomelanocortin (POMC) expressing neurons of the Arcuate nucleus (ARHPOMC). Mice lacking functional KCNB1 channels (NULL mice) have less adipose tissue and circulating leptin than WT animals and are insensitive to anorexic stimuli induced by leptin administration. NULL mice produce aberrant amounts of POMC at any developmental stage. Canonical LepR-STAT3 signaling-which underlies POMC production-is impaired, whereas non-canonical insulin receptor substrate PI3K/Akt/FOXO1 and ERK signaling are constitutively upregulated in NULL hypothalami. The levels of proto-oncogene c-Fos-that provides an indirect measure of neuronal activity-are higher in arcuate NULL neurons compared to WT and most importantly do not increase in the former upon leptin stimulation. Hence, a Kv channel provides a molecular link between neuronal excitability and endocrine function in hypothalamic neurons.

Diffusion and Spectroscopy of H2 in Myoglobin

The diffusional dynamics and vibrational spectroscopy of molecular hydrogen (H2) in myoglobin (Mb) is characterized. Hydrogen has been implicated in a number of physiologically relevant processes, including cellular aging or inflammation. Here, the internal diffusion through the protein matrix was characterized, and the vibrational spectroscopy was investigated using conventional empirical energy functions and improved models able to describe higher-order electrostatic moments of the ligand. Depending on the energy function used, H2 can occupy the same internal defects as already found for Xe or CO (Xe1 to Xe4 and B-state). Furthermore, four additional sites were found, some of which had been discovered in earlier simulation studies. Simulations using a model based on a Morse oscillator and distributed charges to correctly describe the molecular quadrupole moment of H2 indicate that the vibrational spectroscopy of the ligand depends on the docking site it occupies. This is consistent with the findings for CO in Mb from experiments and simulations. For H2, the maxima of the absorption spectra cover ∼20 cm−1 which are indicative of a pronounced Stark effect of the surrounding protein matrix on the vibrational spectroscopy of the ligand. Electronic structure calculations show that H2 forms a stable complex with the heme iron (stabilized by ∼−12 kcal/mol), but splitting of H2 is unlikely due to a high activation energy (∼50 kcal/mol).

Efficient leaching of valuable metals from spent lithium-ion batteries using green deep eutectic solvents: Process optimization, mechanistic analysis, and environmental impact assessment

The accumulation of over 11 million tons of spent lithium-ion batteries (LIBs) by 2030 highlights a critical environmental challenge posed by their large-scale retirement. The efficient recycling valuable metals from spent LIBs can both reduces environmental impact and mitigates the pressing issue of metal resource scarcity. In this context, deep eutectic solvents (DESs) have become a promising option as an eco-friendly solvent, exhibiting great potential for recycling spent LIBs. Therefore, this work proposed an innovative green DES system consisting of choline chloride (ChCl), DL-malic acid (MAL), and glycerol for the efficient leaching of valuable metals from spent LIBs. Comprehensive experiments were conducted to determine the optimum leaching conditions (130 °C, 60 g/L, MChCl:MAL:Glycerol of 1:1:3, 3 h), achieving high leaching efficiencies of 94.6% for Ni, 96.8% for Co, 93.8% for Mn, and 96.4% for Li. Through characterization techniques, kinetics studies, and density functional theory (DFT) calculations, the leaching process was predominantly governed by surface chemical reaction (1-(1-x)1/3 = kt) within the shrinking core model, exhibited activation energies of 49.89 kJ/mol, 47.66 kJ/mol, 50.51 kJ/mol, and 22.24 kJ/mol for Ni, Co, Mn, and Li, respectively. The propensity for DES to leach metal ions followed the order: Li > Co > Ni > Mn, determined by binding energy and energy gaps. Cl− and −COOH within the DES were capable of forming stable complexes with reduced transition metal ions, revealing an efficient coordination leaching mechanism. Additionally, a life cycle assessment (LCA) was conducted on the environmental impacts of the DES leaching process, confirming it as an effective and environmentally friendly method for recycling spent LIBs. This work avoided the employment of corrosive acids and alleviated the generally harsh conditions associated with DESs leaching, providing a viable solution for recovering spent LIBs.

Binding of a Drug (Colchicine) to L-Asparaginase Enzyme Using Multispectroscopic, Thermodynamics, and Simulation Studies: Possible Implication in Acute Lymphoblastic Leukemia Treatment.

The research aims to elucidate how drug interactions affect the activity of L-asparaginase (L-ASNase), an essential enzyme in cancer treatment, especially for acute lymphoblastic leukemia (ALL). Understanding these interactions is crucial for optimizing treatment effectiveness and reducing adverse effects. This study explores the intricate molecular interactions and structural dynamics of L-ASNase upon binding with colchicine. Fluorescence quenching experiments were conducted at various temperatures (298, 303, and 310 K), revealing notable interactions between L-ASNase and colchicine. These interactions were characterized by a reduction in fluorescence intensity and a blue shift in emission maxima. Additional analyses, including the determination of Stern-Volmer quenching constants (KSV), bimolecular quenching rate constants (kq), and thermodynamic parameters, indicated a static quenching mechanism with moderate binding affinities (Ka: 1.40-2.71 × 104 M-1) across different temperatures. Thermodynamic study suggested positive enthalpy and entropy changes (ΔH° = -10.26 kcal mol-1; ΔS° = -14.19 cal mol-1 K-1), suggesting a spontaneous reaction with negative ΔG° values (-5.86 to -6.03 kcal mol-1). FRET measurements supported optimal distances (r and Ro) for FRET occurrence, reinforcing the static quenching mechanism. Molecular docking further supported these findings, revealing a 1:1 stoichiometric binding ratio for L-ASNase:colchicine and elucidating specific binding orientations and interactions critical for complex stability. Subsequent molecular dynamics simulations spanning 100 ns underscored the stability of the L-ASNase-colchicine complex, with minimal deviations observed in key structural parameters such as RMSD, RMSF, Rg, and SASA. Additionally, spectroscopic analyses, including circular dichroism (CD), synchronous fluorescence, and 3D fluorescence provided insights into the conformational changes and alterations in the microenvironment of aromatic amino acid residues in L-ASNase upon colchicine binding. Moreover, L-ASNase activity was slightly reduced by 25% in the presence of colchicine. This comprehensive investigation sheds light on the molecular intricacies of the L-ASNase-colchicine complex, advancing our understanding of drug-target interactions and offering potential avenues for therapeutic applications.

Bench-Stable Meisenheimer Complexes: Synthesis, Characterization, and Divergent Reactivity for Dearomatization.

The chemistry of the Meisenheimer complexes is of fundamental interest in organic chemistry. While the nitro group has been extensively employed to facilitate the formation and stabilization of Meisenheimer complexes, the analogous application of more user-friendly ester groups has remained an unexplored frontier. Herein, we report ester-stabilized Meisenheimer complexes, which have remarkable air-, moisture-, and thermo-stability. Moreover, the isolable and well-defined Meisenheimer intermediates exhibit divergent reactivity for dearomatization reactions, including modular 1,4-additions, dearomative (2 + 3) cycloadditions, and even higher-order (4 + n) cycloadditions. These methodologies enabled rapid access to complicated cyclohexane derivatives with multiple all-carbon quaternary centers and interesting structure topologies.

Bridge-Dependent Donor-Metal-Acceptor-Metal-Donor (D-M-A-M-D) Systems: From Charge Transfer to Electron Transfer in Dioxolene-Ge-Diimine Complexes.

Synthesis and structural characterization of a family of germanium-dioxolene complexes with ditopic N-donor ligands (L1-L5) (L1=1,2-bis(pyridin-2-ylmethylene)hydrazine L2=1,6-bis-(pyridin-2-yl)-2,5-diaza-1,5-hexadiene, L3=N,N-bis(pyridin-2-ylmethylene)-1,4-benzenediamine, L4=N,N-bis(pyridin-2-ylmethylene)-(biphenyl)-4,4-diamine, L5=2,2'-azopyridine) is reported. The reaction of germanium bis-catecholate with bridging ligands L1 - L4, differing by the nature of the linker between pyridine sites gives rise to dinuclear digermanium complexes (36Cat2Ge)2L1-4 (36Cat=dianion of 3,6-di-tert-butylcatechol) 1-4 of DMAMD type (donor-metal-acceptor-metal-donor) with a charge transfer in the UV-Vis region. In opposite, the interaction of the 36Cat2Ge with 2,2'-azopyridine (L5) results in the two-electron transfer from the donor 36Cat2- ligands to the azopyridine bridge forming stable open-shell complex 5 [(36SQ)(36CatGe)]2(L5)2- (36SQ=radical-anionic semiquinonate ligand). Molecular structures of compounds 3 and 5 were determined by single crystal X-ray diffraction analysis. Electronic structures of complexes 1-5 were studied by means of DFT calculations.

Evaluation of β‐ and γ‐Cyclodextrins as Promising Bisoprolol Drug Carriers: Docking, Molecular Dynamics and MM‐PBSA1 Free‐Energy Calculations*

AbstractIn this research work, the binding mechanism of Bisoprolol (BIS) drug into the beta‐cyclodextrin (β‐CD) and gamma‐cyclodextrin (γ‐CD) nanopores were investigated using docking, molecular dynamics (MD) simulations, and MM‐PBSA free energy calculations. Also, we assessed the energetic aspects within the BIS‐CDs complex under different thermal conditions in four stages from 298 to 334 K, which includes mammalian body temperature in order to approximate physiological conditions. The computational results reveal that the encapsulation of the BIS into the cavities of CDs is reinforced by hydrogen bonds (HBs) and van der Waals (vdW) interactions in the aqueous phase. The stability of the inclusion complexes of β and γ‐CD with BIS was confirmed by evaluating system stability, flexibility, dynamic and thermodynamic properties at all temperature steps. Next, we analyzed the degree of complexation between BIS and CDs at four different temperatures. The findings revealed that the degree of complexation is decreased as the temperature is increased. The translational movement of the drug to the outside of the CDs cavity increased in the temperature range of 310 to 334 K in γ‐CD more than β‐CD. The β‐CD complex exhibits greater stability compared to the γ‐CD complex in the aqueous medium. The MM‐PBSA free energy approach also confirms more binding affinity of BIS drug into the β‐CD cavity. keywords: Bisoprolol, β‐cyclodextrin, γ‐cyclodextrin, Molecular dynamics, MM‐PBSA free energy.

Supramolecular Modeling of Molecularly Imprinted Chitosan-Thiamin Using Density Functional Theory

The evaluation of chitosan and thiamin interactions has been conducted using density functional theory (DFT) to model a slow-release system of the active ingredient thiamin from the chitosan matrix. The geometry optimization method for modeling was selected using the DFT/B3LYP method with various basis sets. Molecularly imprinted chitosan (MIC) complex models with thiamin were created in two different configurations. All models were optimized using selected computational methods. The optimized complex models were used to calculate interaction energies and analyze the non-covalent interactions between the MIC cavity and thiamin. The MIC-thiamin complex models formed relatively stable supramolecular complexes with a relatively low interaction energy of -171 kJ/mol and formed four hydrogen bonds with bond lengths around 1.83-2.12 Å.