Ammonium adsorption on Brønsted acidic centers on low-index vanadium pentoxide surfaces

In silico investigation of potential phytoconstituents against ligand- and voltage-gated ion channels as antiepileptic agents

The most promising anticonvulsant phytocompounds were explored in this work using docking, molecular dynamic (MD) simulation, and Molecular Mechanics-Poisson-Boltzmann Surface Area (MM-PBSA) approaches. A total of 70 phytochemicals were screened against α-amino-3-hydroxyl-5-methyl-4-isoxazole propionic acid (AMPA), N-methyl-d-aspartate (NMDA), voltage-gated sodium ion channels (VGSC), and carbonic anhydrase enzyme II (CA II) receptors, and the docking results were compared to the reference drug phenytoin. Amentoflavone displayed the highest affinity for AMPA and VGSC receptors, with docking scores of - 10.4 and - 10.1 kcal/mol, respectively. Oliganthin H-NMDA and epigallocatechin-3-gallate-CA II complexes showed docking scores of - 10.9 and - 6.9 kcal/mol, respectively. All four complexes depicted a high dock score compared to the phenytoin complex at the binding site of the corresponding proteins. The MD simulation investigated the stabilities and favorable conformation of apoproteins and ligand/reference-bound complexes. The results revealed that proteins AMPA, VGSC, and CA II were more efficiently stabilized by lead phytochemicals than phenytoin binding. Additionally, principal component analysis and MM-PBSA results suggested that these lead phytocompounds have good compactness and strong binding free energy. Further, physicochemical and pharmacokinetic studies revealed that these final lead phytochemicals would be suitable for oral intake, have sufficient intestinal permeability, and have the ability to cross the blood-brain barrier (BBB). Comprehensively, this study predicted amentoflavone as the best lead phytochemical out of the 70 anticonvulsant phytocompounds that can be used to treat epilepsy.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-024-03948-1.

Thermodynamic and Kinetic Studies on Adsorption of Vanadium with Glutamic Acid

Many hydrometallurgy methods, including chemical precipitation, ion exchange, solvent extraction, and adsorption, have been used to recover vanadium from vanadium solution, but the final step of these methods involved precipitation with ammonium salts, high concentrations of which are harmful to the environment. The key point is to find a new compound to replace ammonium salts without reducing the vanadium precipitation efficiency. The adsorption process of vanadium with glutamic acid is investigated. The effects of experimental factors, including dosage of glutamic acid, reaction temperature, concentration of H2SO4, and reaction time, on the adsorption process are investigated. The results show that nearly 91.66% vanadium is adsorbed under the following reaction conditions: reaction temperature of 90 °C, H2SO4 concentration of 20 g/L, glutamic acid dosage at n(glu)/n(V) = 3.0:1, and reaction time of 60 min. The response surface methodology is applied to optimize the reaction conditions. The analysis results indicate that the reaction temperature has the greatest effect on the adsorption efficiency of vanadium and the influence of experimental factors follows the order: reaction temperature > dosage of glutamic acid to vanadium > reaction time > concentration of H2SO4. The pseudo-second-order model is selected to describe well the adsorption kinetic behavior, and the thermodynamic analysis results indicate that the adsorption process of vanadium is unspontaneous and exothermic. The results will be useful for further applications of glutamic acid, and they provide a bright future for vanadium recovery.

Poisoning Effects of Phosphorus, Potassium and Lead on V2O5-WO3/TiO2 Catalysts for Selective Catalytic Reduction with NH3

The poisoning effect of single elements on commercial V2O5-WO3/TiO2 catalysts has been studied in the past decades. In this study, the combined effects of two multi-element systems (phosphorus-potassium and phosphorus-lead) on V2O5-WO3/TiO2 catalysts were studied by diverse characterizations. The results show that potassium and lead can result in the deactivation of catalysts to different degrees by reacting with active acid sites and reducing the amount of V5+. However, phosphorus displays slight negative influence on the NOx conversion of the catalyst due to the comprehensive effect of reducing V5+ amount and generating new acid sites. The samples poisoned by phosphorus–potassium and phosphorus–lead have higher NOx conversion than that by potassium or lead, because doped potassium or lead atoms may react with new acid sites generated by phosphate, which liberates more V–OH on the surface of catalysts and reduces the poisoning effects of potassium or lead on vanadium species and active oxygen species.

Perovskite-based catalysts for the control of nitrogen oxide emissions from diesel engines

Nitrogen oxides removal over a wide range of perovskite-based catalysts together with their property-activity relationships.

QM/MM reveals the sequence of substrate binding during OPRT action

Computational investigation of orotate phosphoribosyltransferase (OPRT) action, an enzymatic reaction between phosphoribosyl pyrophosphate (PRPP) and orotic acid (OA) to yield orotidine 5'-monophosphate (OMP), was carried out. Insights into the pathways of the substrate attack step of the reaction were developed under the quantum mechanics/molecular mechanics framework with S. cerevisiae strain as the representative enzyme bearer. Four pathways were proposed for PRPP and OA binding differing in the sequence of PRPP, OA and Mg²⁺ ion complexation with OPRT. The formation of Mg²⁺-OPRT complex was accompanied by a small energy change while the largest stabilization was observed for the formation of Mg²⁺-PRPP complex supporting the experimental observation of Mg²⁺-PRPP complex as the true substrate for the reaction. Formation of PRPP-OPRT complex was found to be energetically not probable rendering the pathway requiring Mg²⁺-OA complex not probable. Further, PRPP migration towards the active site was found to be energetically not favoured rendering the pathway involving Mg²⁺-OA complexation improbable. Migration of OA and Mg²⁺-PRPP complex towards the active site was found to be energetically probable with a large stabilization of the system when Mg²⁺-PRPP complex bound to the OA-OPRT complex. This conclusively proved the sequential binding of OA and Mg²⁺-PRPP complexes during OPRT action.

Effect of surface hydroxyls on dimethyl ether synthesis over the γ-Al₂O₃ in liquid paraffin: a computational study

In a recent paper (Zuo et al., Appl Catal A 408:130-136, 2011), the mechanism of dimethyl ether (DME) synthesis from methanol dehydration over γ-Al2O3 (110) was studied using density functional theory (DFT). Using the same method, the effect of surface hydroxyls on γ-Al2O3 in liquid paraffin during DME synthesis from methanol dehydration is investigated. It is found that DME is mainly formed from two adsorbed CH3O groups via methanol dehydrogenation on both dehydrated and hydrated γ-Al2O3 in liquid paraffin. No close correlation between catalytic activity and acid intensity was found. Before and after water adsorption at typical catalytic conditions (e.g., 553 K), the reaction rate is not obviously changed on γ-Al2O3(100) surface in liquid paraffin, but the reaction rate decreases by about 11 times on the (110) in liquid paraffin. Considering the area of the (110) and (100) surfaces under actual conditions, the catalytic activity decreased mainly because the Al3 sites on the (110) surface gradually become inactive. Catalytic activity decreased mainly due to surface hydrophilicity. The calculated results were consistent with the experiment.