C-H Bond Research Articles

ANN-QSAR, Molecular Docking, ADMET Predictions, and Molecular Dynamics Studies of Isothiazole Derivatives to Design New and Selective Inhibitors of HCV Polymerase NS5B

Background/Objectives: RNA polymerase (NS5B), serves as a crucial target for pharmaceutical interventions aimed at combating the hepatitis C virus (HCV), which poses significant health challenges worldwide. The present research endeavors to explore and implement a variety of advanced molecular modeling techniques that aim to create and identify innovative and highly effective inhibitors that specifically target the RNA polymerase enzyme. Methods: In this study, a QSAR investigation was carried out on a set of thirty-eight isothiazole derivatives targeting NS5B inhibition and thus hepatitis C virus (HCV) treatment. The research methodology made use of various statistical techniques including multiple linear regression (MLR) and artificial neural networks (ANNs) to develop satisfactory models in terms of internal and external validation parameters, indicating their reliability in predicting the activity of new inhibitors. Accordingly, a series of potent NS5B inhibitors is designed, and their inhibitory potential is confirmed through molecular docking simulations. Results: These simulations showed that the interactions between these inhibitors and the active site 221 binding pocket of the NS5B protein are hydrophobic and hydrogen bond interactions, as well as carbon–hydrogen bonds and electrostatic interactions. Additionally, these newly formulated compounds displayed favorable ADMET characteristics, with molecular dynamics investigations revealing a stable energetic state and dynamic equilibrium. Conclusions: Our work highlights the importance of NS5B inhibition for the treatment of HCV.

Crystal Structures of Sulfobetaine-8 Solvates: Bend Hydrophobic Chains and Doubly Charge-Assisted Hydrogen Bonds N+CH⋯−O3S

Three novel solvatomorphs (C13H29NO3S•CH3OH, 1; C13H29NO3S•0.113(H2O), 2; C13H29NO3S•0.038(H2O), 3) of zwitterionic sulfobetaine-8 were obtained and their structures were determined using single-crystal X-Ray diffraction. In all cases dimethyl–amino substituted hydrophobic chains -(CH2)3-N+Me2-(CH2)7-Me exhibit kinks at nitrogen atoms resulted from strong intra- and intermolecular CH⋯O hydrogen bonds between negatively charged sulfonic anion -O3S- and positively charged tetraalkylammonium fragments. Periodic (solid state) DFT calculations for structure 1 showed that the energy of the intermolecular hydrogen bonds CH…O is very high, at about 17 kJ/mol. In hydrates 2 and 3, water molecules play the structure-forming role since they interconnect hydrophobic layers by HOH…-O3S hydrogen bonds. The location of only partially occupied water molecules in the interlayer space leads to low stability of both crystals 2 and 3 in open air.

Molecular Modelling of Resveratrol Derivatives with SIRT1 for the Stimulation of Deacetylase Activity.

Resveratrol is a polyphenol that is found in plants and has been proposed to have a potential therapeutic effect through the activation of SIRT1, which is a crucial member of the mammalian NAD+ -dependent deacetylases. However, how its activity is enhanced toward specific substrates by resveratrol derivatives has not been studied. This study aimed to evaluate the types of interaction of resveratrol and its derivatives with SIRT1 as the target protein, as well as to find out the best ligand with the strangest interaction with SIRT1. In this study, we employed the extensive molecular docking analysis using AutoDock Vina to comparatively evaluate the interactions of resveratrol derivatives (22 molecules from the ZINC database) as ligands with SIRT1 (PDB ID: 5BTR) as a receptor. The ChemDraw and Chem3D tools were used to prepare 3D structures of all ligands and energetically minimize them by the MM2 force field. The molecular docking and visualizations showed that conformational change in resveratrol derivatives significantly influenced the parameter for docking results. Several types of interactions, including conventional hydrogen bonds, carbon-hydrogen bonds, Pi-donor hydrogen bonds, and Pi-Alkyl, were found via docking analysis of resveratrol derivatives and SIRT1 receptors. The possible activation effect of resveratrol 4'-(6-galloylglucoside) with ZINC ID: ZINC230079516 with higher binding energy score (-46.8608 kJ/mol) to the catalytic domain (CD) of SIRT1 was achieved at the maximum value for SIRT1, as compared to resveratrol and its other derivatives. Finally, resveratrol 4'-(6-galloylglucoside), as a derivative for resveratrol, has stably interacted with the CD of SIRT1 and might be a potential effective activator for SIRT1.

Pressure Effect on Surface Roughness of Gradient Chromium-doped Diamond-like Carbon Coatings under High Temperature

Abstract In this paper, the pressure effect of surface roughness of four gradient chromium-doped diamond-like carbon (GCD-DLC) coating is systemically studied in argon annealing and high pressure annealing under high temperature. After HIPping annealing, the surface roughness of the hydrogen-free group (GCr and GCrSi) decreased slightly. However, for the two hydrogen-containing GCD-DLC coatings (DCr and DCrSi), especially the DCr coating, the roughness increased significantly. The changes in surface roughness of the hydrogen-free group and the hydrogen-containing group after high-pressure annealing are opposite. The surface roughness of the DCr coating increased significantly after 500°C HIP annealing, which is attributed to the pores on the coating surface. Only the surface morphology of the DCr coating exhibited significant changes. Numerous voids appeared on the surface of the DCr5H coating after 500°C HIP annealing. There were significant differences in the size and shape of these voids compared to those after 500°C argon annealing. The voids on the coating after argon annealing were larger than those after HIP annealing. The formation of pores is associated with the breaking of carbon-hydrogen bonds and the subsequent release of hydrogen. This is because high pressure slows down the transformation from sp3 carbon bonds to sp2 carbon bonds. Simultaneously, high pressure also slows down the release of hydrogen within the coatings.

Antibacterial activity of polyethylene film by hyperthermal hydrogen induced cross-linking with chitosan quaternary ammonium salt

In this study, hyperthermal hydrogen-induced cross-linking (HHIC) technology was applied to construct a dense cross-linking layer of antibacterial chitosan quaternary ammonium salt (HTCC) to PE surface through the selective cleavage of CH bonds and subsequent cross-linking of the resulting carbon radicals. Before HHIC treatment, UV-Ozone was used to activate PE surface to facilitate HTCC adsorption. FT-IR and XPS analyses proved the successful cross-linking between PE and HTCC. From AFM analysis, the prepared PE cross-linked HTCC film (PE-c-HTCC) showed the rougher surface with average roughness (Ra) of 9.16 nm. The water vapor permeability (WVP) and oxygen permeability (OP) values of the film were decreased by about 83 % and 97 %, respectively. Additionally, the film exhibited strong antibacterial properties against E. coli and S. aureus. In terms of these properties, the shelf life of fresh beef could be extended for 2 days after packing with the PE-c-HTCC film.

Activating copper by creating low-coordinated copper sites for antibiotic detoxification through Electrocatalytic hydrodechlorination reaction

Electrocatalytic hydrodehalogenation (ECHD) offers a sustainable venue for detoxifying halogenated antibiotics by converting CX (XBr, Cl and F) bonds to CH bonds. Metallic copper (Cu) is a promising catalyst with higher chemical stability compared to general cobalt-based catalysts but suffers from lower activity toward dilute antibiotic pollutants. Herein, we activated the Cu by creating numbers of low-coordinated Cu sites on skeleton surface of a Cu foam electrode (r-CF) through a stepwise calcination and electrochemical reduction (C-ER) process. The r-CF electrode demonstrated extraordinary activity in FLO removal with a mass activity of 3.3 gFLO h−1 m−2. More importantly, it achieved 100 % conversion of CCl bonds at a relatively mild potential of −0.30 V, outperforming pristine Cu foam electrode (64.6 %) and most reported catalysts. Mechanistic studies revealed that the low-coordinated Cu sites exhibited an upshift d band center towards Fermi level, which facilitated pollutant adsorption and electron transfer on these sites. Furthermore, the C-ER processing increased the roughness of the skeleton, enlarging the laminar region in the vicinity of active sites and enhancing the turbulent state around the electrode during ECHD. These dual enhancement contributed to the mass transfer of FLO from bulk solution to electrode and their stabilization at active sites. The r-CF was further applied to detoxify a FLO-contaminated lake water sample. It was able to reduce the antibacterial activity of the water by 81.7 %. This work offered a new approach to activate the Cu for ECHD, and demonstrated the promise of Cu-mediated ECHD for antibiotics contamination remediation.

Rhodium(III)-Catalyzed Regioselective C4 Alkylation of Indoles with Nitroalkenes.

The Rh(III)-catalyzed indole C4-H bond addition to nitroalkenes is disclosed under mild and redox-neutral reaction conditions, offering straightforward access to various 4-(2-nitroalkyl)indoles (34 examples) with excellent chemo- and regioselectivity. Furthermore, late-stage diversifications and mechanistic studies were also performed.

The radical scavenging activity of 1-methyl-1,4-dihydronicotinamide: theoretical insights into the mechanism, kinetics and solvent effects.

1,4-Dihydronicotinamide derivatives, including 1-methyl-1,4-dihydronicotinamide (MNAH), are derivatives of the active center of nicotinamide coenzyme (NADH) and are therefore potent radical scavengers. MNAH serves as a useful model of NADH that allows for modeling studies to address the activity of this important biomolecule. In this work, MNAH activity was evaluated against typical free radicals using quantum chemical calculations in physiological environments, with a secondary aim of comparing activity against two physiologically relevant radicals of markedly different stability, HO˙, and HOO˙, to establish which of these is a better model for assessing antioxidant capacity in physiological environments. The HO˙ + MNAH reaction exhibited diffusion-limited overall rate constants in all media, including the gas phase. The HOO˙ antiradical activity of MNAH was also good, with overall rate constants of 2.00 × 104 and 2.44 × 106 M-1 s-1, in lipid and aqueous media, respectively. The calculated rate constant in water (k overall(MNAH + HOO˙) = 3.84 × 105 M-1 s-1, pH = 5.6) is in good agreement with the experimental data (k exp(NADH + HOO˙) = (1.8 ± 0.2)×105 M-1 s-1). In terms of mechanism, the H-abstraction of the C4-H bond characterized the HOO˙ radical scavenging activity of MNAH, whereas HO˙ could react with MNAH at several sites and following either of SET (in polar media), RAF, and FHT reactions, which could be ascribed to the high reactivity of HO˙. For this reason the results suggest that activity against HOO˙ is a better basis for comparison of anti-radical potential. In the broader context, the HOO˙ scavanging activity of MNAH is better than that of reference antioxidants such as trans-resveratrol and ascorbic acid in the nonpolar environment, and Trolox in the aqueous physiological environment. Therefore, in the physiological environment, MNAH functions as a highly effective radical scavenger.

Identification of heterozygous mutations of ABCC8 gene responsible for maturity-onset diabetes of the young with exome sequencing

Abstract Background Although the MODY12 subtype, caused by ABCC8 mutations, is rare, it is highly sensitive to sulfonylureas. The identification of ABCC8 mutations in patients clinically diagnosed with MODY has the ability to contribute to the precise management of diabetes. Methods Genetic analysis of two families with MODY were conducted using whole-exome sequencing (WES) and Sanger sequencing. The spatial structures of the mutant proteins were constructed using MODELLER and PyMOL software to provide further evidence of pathogenicity. Results The heterozygous missense mutations V357I and R1393H in ABCC8 were found in probands of two unrelated MODY pedigrees, which co-segregated with the hyperglycemic phenotypes in these two pedigrees. Detection of the V357I mutation enabled the proband of family A to successfully transfer from insulin to sulfonylurea (SU). After 3 months of follow-up for the SU trial, the HbA1c level of proband A improved from 12.4% at the initial diagnosis to 7.20%. Proband B was treated with insulin because of pregnancy and poor islet function. In silico analysis indicated that the R1393H mutation resulted in a longer hydrogen bond distance to L1389 and cleavage of carbon-hydrogen bonds to V1395, A1390, and L1389. Conclusions We have described two pathogenic missense mutations in ABCC8 in Chinese families with MODY. Our findings support the heterogeneity in the clinical features of MODY12 caused by ABCC8 mutations.

Flipping the Metalation of 4-Dimethylaminopyridine: Steric Repulsion versus London Dispersion Attraction.

Non-covalent interactions, including the coordination of an organolithium reagent by a directing group and the steric hindrance from substituents, play a crucial role in determining the selectivity of metalation reactions. Here, we demonstrate the effective utilization of steric interactions for flipping the lithiation of 4-dimethylaminopyridine (DMAP). Introduction of a Me3Si substituent to the position 1 of DMAP or simple complexation with t-BuLi allows selective C3-lithiation, due to the steric hindrance of a C2-H bond by the bulky moiety at the pyridine nitrogen. This simple approach creates a convenient way to achieve the selective C3-functionalization of DMAP. In contrast, the utilization of an even bulkier i-Pr3Si substituent leads to exclusive C2-functionalization due to the dispersion interactions with organometallic bases. For the first time, it is demonstrated that the i-Pr3Si moiety can serve as a directing group, providing a new type of directed ortho-metalation effect.

Copigmentation effect on red cabbage anthocyanins, investigation of their cellular viability and interaction mechanism

Anthocyanins (ANS) are an appealing substitute to synthetic colorants; but their practical applicability is limited due to low color stability. Copigmentation can improve both complex’s color stability as well as intensity. In this study, we examined the interaction of red cabbage ANS with copigments i.e., two organic acid, two phenolic acid, a flavonoid and three amino acid through experimental and theoretical approach. Among various copigments, phenolic and organic acids induced a strong bathochromic shift of 6.5–7.1 nm and 5.1–11.6 nm. Thermal analysis, anthocyanin content and chromaticity, were used to assess the color intensity and stability of ANS, at 4 ℃, 25 ± 2 ℃, sunlight, oxygen, and heat. Results revealed that oxalic acid copigmented complex followed by chlorogenic and rosmarinic acid exhibits significant thermal stability with greater retention rate at 120 ℃ and 150 ℃. In case of anthocyanin content and colorimetric parameters, chlorogenic acid followed by oxalic and rosmarinic acid exhibits significantly improved stability. Rosmarinic acid copigmented sample showed good cell viability at high concentration (200 µg/mL). Steered molecular dynamics and thermodynamic analysis reveals chlorogenic and rosmarinic acid as promising copigments involving conventional H-bonds, π-π interactions, and carbon hydrogen bonds.

Extra-framework cations promoted zeolite-encaged cobalt catalysts towards efficient ethylbenzene dehydrogenation

The transformation of ethylbenzene to styrene through direct dehydrogenation is essential process in chemical industry, indispensable for the synthesis of polymers and plastics. Herein, faujasite zeolite encaged cobalt catalyst with potassium ion as the extraframework cations, namely K-Co@Y, is reported to be a robust catalyst for ethylbenzene direct dehydrogenation, showing ethylbenzene conversion of ∼45 % and styrene selectivity of ∼95 % simultaneously under employed conditions. The superior performance of K-Co@Y in comparison with Na-Co@Y is attributed to the effective modulation of zeolite-encaged Co2+ species by extraframework K+ ions, which increases the electron density of cobalt sites and facilitates CH bond activation. Although coke deposits cause gradual deactivation, the structural integrity of K-Co@Y can be well preserved during the dehydrogenation reaction and the performance can be full restored via a simple calcination regeneration step, making K-Co@Y an eligible catalyst for long-term running in the continuous regeneration mode. This study highlights the vital role of extraframework cations in zeolite-encaged single-site catalysts for target chemical transformations and opens up a new way to modulate the performance of zeolite catalysts.

Enhanced electrocatalytic C[sbnd]H amination of toluene via tailored interfacial microenvironment

Electrocatalytic CH amination of hydrocarbons is a promising avenue for the synthesis of high-value CN compounds. However, efficient activation of CH bonds remains a significant challenge in electrocatalytic CN coupling. Herein, we present a novel strategy to enhance the electrocatalytic conversion of toluene to N-benzylacetamide through a Ritter–type reaction by engineering a hydrophobic electrode–electrolyte interface using polytetrafluoroethylene (PTFE)-coated carbon paper (CP). The hydrophobic CP-based electrode exhibited a superior N-benzylacetamide productivity of 1860.9 mmol m−2h−1 and a substantially higher Faradaic efficiency (FE) of 70.1 % compared to pure CP (41.5 %). Experimental results and density functional theory (DFT) calculations reveal that the PTFE coating promotes toluene adsorption and efficiently lowers the energy barrier for toluene dehydrogenation. Additionally, the hydrophobic interface effectively hinders water adsorption on the electrode, suppressing the competitive water oxidation reaction. This study underscores the crucial role of interfacial engineering in optimizing electrocatalytic CN coupling reactions for the sustainable synthesis of high-value amide compounds.

Influence of the second coordination sphere on O2 activation by a nonheme iron(II) thiolate complex

The synthesis and characterization of a new ligand, 1-(bis(pyridin-2-ylmethyl) amino)-2-methylpropane-2-thiolate (BPAMe2S−) and its nonheme iron complex, FeII(BPAMe2S)Br (1), is reported. Reaction of 1 with O2 at −20 °C generates a high-spin iron(III)-hydroxide complex, [FeIII(OH)(BPAMe2S)(Br)] (2), that was characterized by UV–vis, 57Fe Mössbauer, and electron paramagnetic resonance (EPR) spectroscopies, and electrospray ionization mass spectrometry (ESI-MS). Density functional theory (DFT) calculations were employed to support the spectroscopic assignments. In a previous report (J. Am. Chem. Soc.2024, 146, 7915–7921), the related iron(II) complex, FeII(BNPAMe2S)Br (BNPAMe2S− = bis((6-(neopentylamino)pyridinyl) methyl)amino)-2-methylpropane-2-thiolate) was reported and shown to react with O2 at low temperature to give a rare (η2-superoxo)‑iron(III) intermediate, which then converts to an S‑oxygenated sulfinate as seen for the nonheme iron thiol dioxygenases. This complex includes two hydrogen bonding neopentylamino groups in the second coordination sphere. Complex 1 does not include these H-bonding groups, and its reactivity with O2 does not yield a stabilized Fe/O2 intermediate or S‑oxygenated products, although the data suggest an inner-sphere mechanism and formation of an iron‑oxygen species that is capable of abstracting hydrogen atoms from solvent or weak CH bond substrates. This study indicates that the H-bond donors are critical for stabilizing the FeIII(O2-•) intermediate with the BNPAMe2S− ligand, which in turn leads to S‑oxygenation, as opposed to H-atom abstraction, following O2 activation by the nonheme iron center.

1,3-Dipolar Cycloaddition of Nitrile Oxides and Nitrilimines to (-)-β-Caryophyllene: Stereoselective Synthesis of Polycyclic Derivatives and Their Biological Testing.

The cycloaddition of nitrile oxides and nitrilimines to one or both of the C=C double bonds of caryophyllene is described. The possibility of introducing five-membered fused and spiro-linked heterocycles into the structure of sesquiterpenes by the 1,3-dipolar cycloaddition reactions of nitrile oxides and nitrilimines to caryophyllene was demonstrated. As a result of these reactions, pharmacophore fragments of isoxazoline and pyrazoline are introduced into the structure of caryophyllene, which leads to an increase in the conformational rigidity of the molecule. A complete stereochemical assignment of 1,3-dipolar cycloaddition adducts to caryophyllene was carried out. The study of antiviral and cytotoxic activity for some heterocyclic derivatives synthesized in this work revealed relatively high biological activity of previously little-studied cycloaddition adducts at the exocyclic C=CH2 bond of caryophyllene. The effect of substituents in the synthesized heterocycles on biological activity was demonstrated. Compounds with a good inhibitory effect on the H1N1 influenza virus were revealed. The activity of the compound was demonstrated up to 6 h post infection, and this could be due to slight inhibiting activity against viral neuraminidase, necessary at the stage of progeny virion budding.

ATR-FTIR characterisation of daily-use plastics mycodegradation

Synthetic polymers, such as plastics, have permeated all aspects of modern life, and nowadays plastic pollution is a major environmental problem. Mycodegradation of these polymers could represent part of the solution to this problem since it calls on a broad toolbox of enzymes and applies non-enzymatic mechanisms to degrade and deteriorate recalcitrant materials. However, not enough is known about this ability for most of the representatives of the fungal kingdom. Another bottleneck is the harmonisation of technologies to analyse plastic degradation. This work involved the design of a biodegradation experiment, where the potential of four fungi representative of Dikarya and Penicillia (Funalia floccosa, Trametes versicolor, Pycnoporus cinnabarinus and Penicillium oxalicum) were tested on their ability to deteriorate the six most used plastics based on gravimetry and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). The following correlation between changes in the band signals and the loss of mass after treatment was determined using polyethylene terephthalate, polypropylene, polyethylene, poly vinyl chloride, high density polyethylene, low density polyethylene and nylon. After treatment, the decrease in absorbance of the characteristic bands of the plastics was taken as an indication of the degradation of the corresponding bonds/functionalities. The four fungi used could transform CH, CH2, CH3, CO, CO, CN, NH and CCl bonds. The best result was obtained using the fungus F. floccosa with 90-day treatments for high density polyethylene (∼ 62.0 %), low density polyethylene (∼ 23.6 %) and nylon (∼ 35.6 %). Therefore, mycodegradation could open up new doors in the fight against plastic pollution.

Integrative computational approach for hyperuricemia treatment: 3D QSAR, molecular docking and dynamics of flavonoid analogues as xanthine oxidase inhibitors

Hyperuricemia is characterized by an excessive accumulation of uric acid in the joints, and this condition remains a therapeutic challenge with limited options and significant side effects associated with conventional pharmacological treatments. This research aims to identify new molecular structures capable of inhibiting uric acid production by targeting key enzymes in purine metabolism. In this study, a comprehensive in silico analysis was conducted to explore the relationship between the chemical structure of flavonoid analogs and their inhibitory capacity on xanthine oxidase (XO). The results revealed that the analogs meet the structural requirements for xanthine oxidase inhibition. A 3D-QSAR model was generated, accurately predicting the biological activity of flavonoids targeting XO and identifying a potential lead compound with a q2 of 0.77 and R2 of 0.98. The CoMFA analysis disclosed how substituents affect XO affinity, with bulky groups enhancing it at positions R2 and R7. These strategies were applied and a new molecule was generated with better binding energy with the XO receptor. Electron-donating or accepting groups, such as phenyl and carbonyl, interact with amino acid residues (T1010 and R880) in XO's active site. Molecular docking analysis highlights different common interaction types in flavonoid-XO binding, emphasizing the importance of hydrogen and CH bonds. Previous studies underscore the significance of these specific residues in flavonoid-XO binding. Molecular dynamics showed that 3(R,S)-3′-Hydroxy-8-methoxyvestitol predominantly interacts through hydrophobic interactions, inducing a conformational change in the binding pocket and stabilizing the complex along with stable hydrogen bonds.

Theoretical screening of single-atom catalysts (SACs) on Mo2TiC2O2 MXene for methane activation

Producing value-added chemicals and fuels from methane (CH4) under mild conditions efficiently utilizes this cheap and abundant feedstock, promoting economic growth, energy security, and environmental sustainability. However, the first CH bond activation is a significant challenge and requires high energy. Efficient catalysts have been sought for utilizing CH4 at low temperatures including emerging single-atom catalysts (SACs). In this work, we screened fourteen transition metals (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Pt) doped at a single oxygen vacancy in Mo2TiC2O2 (TMSA-Mo2TiC2O2 SACs) for methane activation using density functional theory (DFT) calculations. Our results reveal that methane adsorption is thermodynamically stable on all simulated TMSA-Mo2TiC2O2 SACs, with the adsorption energies (Eads) ranging from −0.92 to −0.40 eV. For the CH activation process, Ru-SAC exhibits the lowest activation barrier (Ea) of 0.22 eV. In summary, Ru-, Rh-, Co-, V-, Cr-, Ti-, and Pt-SACs demonstrate promising catalytic properties for methane activation, with Ea values below 1.0 eV and an exothermic nature. Our findings pave the way for the design and development of novel single-atom catalysts in MXene materials, applicable not only for methane activation but also for other alkane dehydrogenation processes.

Binding characteristics of the major kratom alkaloid, mitragynine, towards serum albumin: Spectroscopic, calorimetric, microscopic, and computational investigations

Mitragynine (MTG) is a prominent indole alkaloid that is present abundantly in Mitragyna speciosa, commonly referred to as kratom. MTG has garnered significant attention due to its selective agonistic characteristics towards opioid receptors and related analgesic effects. In the circulatory system, the in vivo efficacy of MTG is dictated by its interaction with plasma proteins, primarily human serum albumin (HSA). In the present study, we utilized a broad methodology that included spectroscopic, calorimetric, microscopic, and in silico approaches to characterize the interaction between MTG and HSA. Alterations in the UV absorption spectrum of HSA by the presence of MTG demonstrated a ground-state complexation between the protein and the ligand. The Ka values obtained for the MTG–HSA interaction were in the range 103–104 M−1 based on analysis of fluorescence and ITC data, respectively, indicating an intermediate binding affinity. The binding reaction was thermodynamically favorable as revealed by ΔH, ΔS, and ΔG values of −16.42 kJ mol−1, 39.97 J mol−1 K−1, and −28.34 kJ mol−1, respectively. Furthermore, CD spectroscopy results suggested MTG binding induced minimal effects on the structural integrity of HSA, supported by computational methods. Changes in the dimensions of HSA particles due to aggregation, as observed using atomic force microscopy in the presence of MTG. Competitive drug displacement results seemingly suggested site III of HSA located at subdomain IB as the preferred binding site of MTG, but were in inconclusive. However, docking results showed the clear preference of MTG to bind to site III, facilitated by hydrophobic (alkyl and pi-alkyl) and van der Waals forces, together with carbon hydrogen bonds. Additionally, the MTG–HSA complexation was demonstrated to be stable based on molecular dynamics analysis. The outcomes of this study shed light on the therapeutic potential of MTG and can help in the design of more effective derivatives of the compound.

Aerobic oxidation of lignin model compounds catalyzed by the iron or copper/ABNO at room temperature with ambient air as the oxidant

Herein, we report a simple, efficient, and mild Fe(NO3)3·9H2O or Cu(NO3)2·3H2O/ABNO- catalytic system (ABNO=9-azabicyclo[3.3.1]nonane-N-oxyl), which was capable of oxidizing β-O-4 alcohol lignin model compounds to ketones at room temperature using ambient air as the oxidant. This versatile catalytic system exhibits excellent substrate scope and the corresponding products were obtained in good to excellent yields. The kinetic isotope effect shows that the CH bond breaking is the rate-determining step of the reaction. The experiment of gram scale proves that the catalytic system has good practicability.