Hydrogen Bridges Research Articles

Structural conservation in the glutathione binding in Sphingomonas sp. glutaredoxin Grx3 and variations for cold adaptation

Glutaredoxin 3 (Grx3), a redox protein with a thioredoxin-fold structure, maintains structural integrity and glutathione (GSH) binding capabilities across varying habitat temperatures. The cis-Pro loop, essential for GSH binding, relies on the Arg-Asp salt bridge (α2-α3) and Gln-His hydrogen bond (β3-β4) for its conformation. In some psychrophilic Grx3 variants, Arg in α2 is replaced with Tyr, and His in β4 is replaced with Phe. This study examines the roles of these bonds in Grx3's structure, function, and cold adaptation, using SpGrx3 from the Arctic bacterium Sphingomonas sp. Despite its cold habitat, SpGrx3 maintains the Arg51-Asp69 salt bridge and Gln56-His63 hydrogen bond. The R51Y substitution disrupts the α2-α3 salt bridge, while the H63F and H63Y substitutions hinder the salt bridge through cation-π interactions with Arg51, involving Phe63/Tyr63, thereby enhancing flexibility. Conversely, mutations that disrupt the hydrogen bond (Q56A, H63A, and H63F) reduce thermal stability. In the psychrophilic Grx3 configuration A48T/R51Y/H63F, a Thr48-Gln56 hydrogen bond stabilizes the cis-Pro loop, enhancing flexibility by disrupting both bonds. Furthermore, all mutants exhibit reduced α-helical content and catalytic efficiency. In summary, the highly conserved Arg51-Asp69 salt bridge and Gln56-His63 hydrogen bond are crucial for stabilizing the cis-Pro loop and catalytic activity in SpGrx3. His63 is favored as it avoids cation-π interactions with Arg51, unlike Phe63/Tyr63. Psychrophilic Grx3 variants have adapted to cold environments by reducing GSH binding and increasing structural flexibility. These findings deepen our understanding of the structural conservation in Grx3 for GSH binding and the critical alterations required for cold adaptation.

Rates and Mechanism of Vivianite Dissolution under Anoxic Conditions.

The iron phosphate mineral vivianite Fe(II)3(PO4)2·8H2O has emerged as a potential renewable P source. Although the importance of vivianite as a potential P sink in the global P cycle had previously been recognized, a mechanistic understanding of vivianite dissolution at the molecular level, critical to its potential application, is still elusive. The potential of vivianite as a P sink or source in natural or engineered systems is directly dependent on its dissolution kinetics under environmentally relevant conditions. To understand the thermodynamic and kinetic controls on bioavailability, the oxidation and dissolution processes of vivianite must be disentangled. In this study, we conducted controlled batch and flow-through experiments to quantitatively determine the dissolution rates and mechanisms of vivianite under anoxic conditions as a function of pH and temperature. Our results demonstrate that vivianite solubility and dissolution rates strongly decreased with increasing solution pH. Dissolution was nonstoichiometric at alkaline pH (>7). The rapid initial dissolution rate of vivianite is related to the solution saturation state, indicating a thermodynamic rather than a kinetic control. A defect-driven dissolution mechanism is proposed. Dissolution kinetics over pH 5-9 could be described with a rate law with a single rate constant and a reaction order of 0.61 with respect to {H+}: The activation energy of vivianite dissolution proved low (Ea = 20.3 kJ mol-1), suggesting hydrogen bridge dissociation as the rate-determining step.

Three-Center M-H-B Bonds Are Strong Field Interactions. Synthesis and Characterization of M(CH2NMe2BH3)3 Complexes of Titanium, Chromium, and Cobalt.

We describe new compounds of stoichiometry M(CH2NMe2BH3)3 (M = Ti, Cr, and Co), each of which contains three chelating boranatodimethylaminomethyl (BDAM) ligands. In all three compounds, the BDAM anion, which is isoelectronic and isostructural with the neopentyl group, is bound to the metal center at one end by a metal-carbon σ bond and at the other by one three-center M-H-B interaction. The crystal structures show that the d1 titanium(III) compound is trigonal prismatic (or eight-coordinate, if two longer-ranged M···H interactions with the BH3 groups are included), whereas the d3 chromium(III) compound and the d6 cobalt(III) compounds are both fac-octahedral. The Cr and Co compounds exhibit two rapid dynamic processes in solution: exchange between the Δ and Λ enantiomers and exchange of the terminal and bridging hydrogen atoms on boron. For the Co complex, the barrier for Δ/Λ exchange (ΔG⧧298 = 10.1 kcal mol-1) is significantly smaller than those seen in other octahedral cobalt(III) compounds; DFT calculations suggest that Bailar twist and dissociative pathways for Δ/Λ exchange are both possible mechanisms. The UV-vis absorption spectra of the cobalt(III) and chromium(III) species show that the ligand field splittings Δo caused by the M-H-B interactions are unexpectedly large, thus placing them high on the spectrochemical series (near ammonia and alkyl groups); their nephelauxetic effect is also large. The DFT calculations suggest that these properties of M-H-B interactions are in part a consequence of their three-center nature, which delocalizes electron density away from the metal center and reduces electron-electron repulsions.

Novel polymorphisms in the prion protein gene (PRNP) and stability of the resultant prion protein in different horse breeds

Prion diseases are fatal neurodegenerative disorders in which the main pathogenic event is the conversion of the cellular prion protein (PrPC) into an abnormal and misfolded isoform known as PrPSc. Most prion diseases and their susceptibility and pathogenesis are mainly modulated by the PRNP gene that codes for PrP. Mutations and polymorphisms in the PRNP gene can alter PrPC amino acid sequence, leading to a change in transmission efficiency depending on the place where it occurs. Horses are animals that are considered to be highly resistant to prions. Several studies have attempted to identify polymorphisms in the PRNP gene that explain the reason for this high resistance. In this study, we have analysed 207 horses from 20 different breeds, discovering 3 novel PRNP polymorphisms. By using computer programmes such as PolyPhen-2, PROVEAN, PANTHER, Meta-SNP and PredictSNP, we have predicted the possible impact that these new polymorphisms would have on the horse prion protein. In addition, we measured the propensity for amyloid aggregation using AMYCO and analysed the lack of hydrogen bridges that these changes would entail together with their electrostatic potentials using Swiss-PdbViewer software, showing that an increased amyloid propensity could be due to changes at the level of electrostatic potentials.

Multiphasic Coacervates Assembled by Hydrogen Bonding and Hydrophobic Interactions.

Coacervation has emerged as a prevalent mechanism to compartmentalize biomolecules in living cells. Synthetic coacervates help in understanding the assembly process and mimic the functions of biological coacervates as simplified artificial systems. Though the molecular mechanism and mesoscopic properties of coacervates formed from charged coacervates have been well investigated, the details of the assembly and stabilization of nonionic coacervates remain largely unknown. Here, we describe a library of coacervate-forming polyesteramides and show that the water-tertiary amide bridging hydrogen bonds and hydrophobic interactions stabilize these nonionic, single-component coacervates. Analogous to intracellular biological coacervates, these coacervates exhibit "liquid-like" features with low viscosity and low interfacial energy, and form coacervates with as few as five repeating units. By controlling the temperature and engineering the molar ratio between hydrophobic interaction sites and bridging hydrogen bonding sites, we demonstrate the tuneability of the viscosity and interfacial tension of polyesteramide-based coacervates. Taking advantage of the differences in the mesoscopic properties of these nonionic coacervates, we engineered multiphasic coacervates with core-shell architectures similar to those of intracellular biological coacervates, such as nucleoli and stress granule-p-body complexes. The multiphasic structures produced from these synthetic nonionic polyesteramide coacervates may serve as a valuable tool for investigating physicochemical principles deployed by living cells to spatiotemporally control cargo partitioning, biochemical reaction rates, and interorganellar signal transport.

“Bridging hydrogen bonds” from guanidine and amidoxime groups on natural bamboo strips as a superantibacterial and knitted adsorbent to efficiently adsorb uranium from simulated seawater

Uranium adsorption from seawater can provide a sustainable development path for the future raw material supply of nuclear energy. However, in the process of uranium extraction from seawater, biofouling adheres to the surface of the adsorbent, wasting the adsorption sites and seriously affecting the adsorption capability of the adsorbent. Herein, inspired by the superanti-biofouling property of guanidine groups, a superantibacterial and knitted adsorbent with guanidine and amidoxime groups cografted on natural bamboo strips (G-AOBS) is synthesized to adsorb uranium from simulated seawater. The intrinsic structure of bamboo is not destroyed by the whole grafting process, and G-AOBS still maintains the porous and cellulose crystalline structure. The grafting of guanidine groups improves the hydrophilicity and significantly enhances the anti-biofouling performance, thereby increasing the adsorption capacity for uranium (qe = 201.4 ± 13.23 mg g−1 at pH = 4 with C0 = 100 mg L−1 and qe = 1.04 ± 0.12 mg g−1 in simulated seawater with C0 = 500 μg L−1). According to the results of DFT, the guanidine and amidoxime groups can not only replace one carbonate in uranyl tricarbonate alone to form a more stable coordination structure but also have a synergistic effect between the two, that is, using three “bridging hydrogen bonds” to form the most stable chelation mode with uranyl dicarbonate.

Understanding the Behavior of Sodium Polyacrylate in Suspensions of Silica and Monovalent Salts.

This study investigated the interaction of monovalent cations with different sizes on quartz surfaces and the rheological impact that this causes in concentrated suspensions when subjected to the action of a rheological modifier, in this case, sodium polyacrylate (NaPA). Yield stress was determined using a rheometer with a vane-in-cup configuration to establish the relationship between shear stress and strain. Experiments were carried out in LiCl, NaCl, KCl, and CsCl solutions. The results show that the yield stress increases following the order Li < Na < K < Cs in the absence of PAA. However, the addition of NaPA significantly reduced the yield stress in all cases. This reduction was more noticeable in the LiCl and NaCl solutions than in the KCl and CsCl solutions, suggesting a more pronounced effect of PA in maker salts. We conducted molecular dynamics simulations to understand how PA interacts with dissolved salts on the quartz surface. Our results showed that Li had the highest adsorption, followed by Na, K, and Cs. As the salt concentration increased, so did the adsorption. We validated these simulation results with rheological experiments, which helped us understand the observed differences. The molecular interactions indicate that, in the lithium system, cationic bridges and the synergy between hydrogen bridges and hydrophobic bridges predominate mainly. This tendency decreases as the type of cation is changed due to the decrease in the electrical density of the cation in the following order: Li < Na < K < Cs. This reduces bridging with the quartz surface and, therefore, directly impacts the system's rheological properties.

Synergistic effect of a fluorinated azobenzene for transforming spherical micelles into thread-like micelles with a disk-like cross-section

The free energy in solutions of amphiphilic molecules leads to the formation of supramolecular structures, often making spherical aggregates, worm-like micelles, vesicles, and lamellae. In this work, we add a fluorinated azobenzene, 4-(4-trifluoromethoxy phenyl azo) phenol (Azo-3F) to a solution mainly made of spherical and rodlike micelles of CetylTrimethylAmmonium Bromide (CTAB) and sodium salicylate (NaSal). These structures transform to disk-like micelles, which concatenate through hydrogen bridges to form long thread-like structures highly similar to worm-like micelle structures. This conclusion was reached after observing that NMR results suggest the formation of aggregates in solution with Azo-3F molecules inside them. Viscosity increases by three orders of magnitude at low shear rates when Azo-3F is added, and it shear-thins as the shear rate increases. The viscoelastic spectra show that the fluid changes from viscous to viscoelastic. Cole-Cole plots follow semicircles, typical of Maxwellian behavior below ∼ 35 °C. Cryo-TEM micrographs of the solution with Azo-3F show giant thread-like structures, and cross-sectional analysis of SAXS and WAXS profiles predict oblate ellipsoidal structures. In addition, MD simulations show that the disk-like micelles interact mainly through hydrogen bonds and electrostatics, forming micellar strings. These strings behave similarly to worm-like micelles, explaining why the solution behaves as a Maxwellian fluid at relatively low temperatures. Consequently, when some specific molecules are introduced in supramolecular structures, such as a spherical micelle, they can be transformed into disk-like micelles that assemble into thread-like micelles.

Simple Route to [PSH][B9H14] and a Contemporary Study of Its Solid-State Dynamic Behavior.

The 1,8-bis(dimethylamino)naphthalenium ([PSH]+) decaborane salt, [PSH][B10H13], has been found to react in ethanol to form [PSH][B9H14] (1), affording a simple route to the synthesis of the arachno-nonaborate anion. This new polyhedral salt is characterized by NMR spectroscopy and X-ray diffraction. The measurement of diffusion coefficients by NMR methods demonstrates that the [PSH]+ cation and the [B9H14]- anion form ion pairs in a non-coordinating solvent such as CH2Cl2, whereas in CD3CN the formation of ion pairs was not observed. Insights into the long-known low-energy dynamic behavior, which involves the bridging and endo-terminal hydrogen atoms, are elucidated using DFT calculations. Salts [PSH][B9H14] (1) and [PSH][B9H14]·0.5CHCl3 (solvated, 1·0.5CHCl3) have also been studied by X-ray diffraction analysis. A solid-state NMR study has demonstrated that K[B9H14] and [PSH][B9H14] (1) undergo significantly different motion regimes, being a low-energy, weakly temperature-dependent process for 1, which may be ascribed to some type of low-amplitude reorientation of the whole boron cages. This process may be the mechanism for the low- to-room-temperature order-disorder hidden transition found by X-ray analysis.

Fabrication, characterization and potential application of biodegradable polydopamine-modified scaffolds based on natural macromolecules

Sodium alginate (SA)-based implantable scaffolds with slow-release drugs have become increasingly important in the fields of biomedical and tissue engineering. However, high-molecular-weight SA is difficult to remove from the body due to the lack of SA-degrading enzymes. The very slow degradation properties of SA-based scaffolds limit their applications. Herein, we designed a series of biodegradable oxidized SA (OSA)-based scaffolds through amide bonds, imine bonds and hydrogen bridges between OSA and silk fibroin (SF). SF/OSA-0.4 with a blend ratio of 4/1 was chosen for further polydopamine (PDA) surface modification studies through the optimization of those parameters such as different OSA oxidation degrees, and blend ratios. PDA modified SF/OSA-0.4 (Dopa/SF/OSA-0.4) showed the excellent stability, better stretchable properties, a uniform interconnective porous structure, high thermal stability, a low hemolysis ratio and cytotoxicity. In vitro degradation experiments showed that the degradation rate of SF/OSA was significantly higher than that of SF/SA, but the degradation slowed again after PDA modification. Interestingly, the degradation of Dopa/SF/OSA-0.4 in vivo was significantly faster than that in vitro. Dopa/SF/OSA-0.4 was also more conducive to new tissue growth and collagen bundle formation. Moreover, Dopa/SF/OSA-0.4 improved the absorbability of RhB (model drug) and reduced the sudden release of RhB during the sustained release.

Graphene nanostructures functionalization: Hydrogen bonds and oxide coverage effect

Density functional theory is the most used tool to predict the fundamental properties of crystalline and molecular systems. Here we present a study on the passivated oxidized graphene structures with hydrogen atoms at the edges (GO). A stability analysis was performed using the ground-state energies and first-principles thermodynamics. Initially, two stability pseudo-mappings were made on the GO structures, the first varying the position of an epoxide functional group and the second varying the position of a hydroxyl functional group. It was found that the adsorption of a hydroxyl group could occur at any position on the GO structure. The epoxy group has greater stability towards the nanostructure edges. Oxygen adsorption strengthens in Stone-Wales and C vacancy defects. Vacancies dominate the adsorption process. The O/C ratios were increased to 5%, 9%, 13%, and 16% with 27, 20, 19, and 4 oxidation configurations, respectively. All constructed GO structures are thermodynamically stable. For each selected coverage, the calculated bandgap follows the experimental trend. In addition, hydrogen bonds were observed at all coverages. At 13% and 16% O/C ratios, H2O formation happens without energy barriers, leaving epoxy and carbonyl groups as by-products. Our calculations suggest that hydroxyl groups can spontaneously promote the generation of water molecules together with epoxy and/or carbonyl groups. Hydrogen bridge interactions between the ligands in the hydroxyl group induce such an effect. The mechanism described here helps to understand the reactivity observed in experimental studies of GO nanostructures obtained from the bamboo Guadua Angustifolia ‘Kunth’.

Enhanced SO2 adsorption performance on nitrogen-doped biochar: Insights from generalized two-dimensional correlation infrared spectroscopy

Nitrogen-doped biochar is considered as a renewable, cost-effective, and promising SO2 adsorbent. However, it is difficult to improve the physicochemical properties of biochar synergistically and clarify the adsorption mechanism. Therefore, in this study, a one-step high-temperature CO2-NH3 modification method was proposed for biochar to improve its SO2 adsorption, and the in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (in situ DRIFTS) was used to reveal the interface reaction mechanism between SO2 and nitrogen-doped biochar. The results showed that when the modification temperature exceeded 700 °C, CO2 and NH3 exhibited significant thermal activation and nitrogen doping on biochar simultaneously. Under a modification temperature of 800 °C (BCAN-800), the microporous surface area and nitrogen content of modified biochar reached the highest value of 563.83 m2/g and 6.63 wt%. The SO2 adsorption capacities of BCAN-800 were up to 201.89 mg/g and 145.68 mg/g at 30 °C and 120 °C, respectively. The results of in situ DRIFTS showed that dimeric and bridge hydrogen bonds were the main SO2 adsorption sites on nitrogen-doped biochar at 30 °C. With the increase of adsorption temperature, nitrogen-containing groups as the main adsorption site could combine with SO2 to form sulfamide (60 °C), which eventually existed in a more stable form of SO42−/R-O-SO2-OR′ (120 °C).

Synthesis and crystal structures of three Schiff bases derived from 3-formyl-acetyl-acetone and benzyl-, tert-butyl- and (S)-methyl-benzyl-amine.

Treatment of 3-formyl-acetyl-acetone with the amines benzyl-amine, tert-butyl-amine and (S)-methyl-benzyl-amine led to the formation of the corresponding Schiff bases 3-[(benzyl-amino)-methyl-idene]pentane-2,4-dione, C13H15NO2 (1), 3-[(tert-butyl-amino)-methyl-idene]pentan-2,4-dione, C10H17NO2 (2) and 3-{[(S)-benz-yl(meth-yl)amino]-methyl-idene}pentane-2,4-dione, C14H17NO2 (3). The mol-ecules of all three compounds exist as enamine tautomers that contain a nearly planar amino-methyl-ene-pentane-2,4-dione core with a strong intra-molecular N-H⋯O hydrogen bridge. The R group attached to the enamine N atom has no significant influence on the bond lengths and angles of the amino-methyl-ene-pentane-2,4-dione core. The supra-molecular structures in 1-3 are mainly based on weak C-H⋯O hydrogen bonds.

HydraMap v.2: Prediction of Hydration Sites and Desolvation Energy with Refined Statistical Potentials.

The complex network of water molecules within the binding pocket of a target protein undergoes alterations upon ligand binding, presenting a significant challenge for conventional molecular modeling methods to accurately characterize and compute the associated energy changes. We have previously developed an empirical method, HydraMap (J. Chem. Inf. Model. 2020, 60, 4359-4375), which employs statistical potentials to predict hydration sites and compute desolvation energy, achieving a reasonable balance between accuracy and speed. In this work, we present its improved version, namely, HydraMap v.2. We updated the statistical potentials for protein-water interactions through an analysis of 17 042 crystal protein structures. We also introduced a new feature to evaluate ligand-water interactions by incorporating statistical potentials derived from the solvated structures of 9878 small organic molecules produced by molecular dynamics simulations. By combining these potentials, HydraMap v.2 can predict and compare the hydration sites in a binding pocket before and after ligand binding, identifying key water molecules involved in the binding process, such as those forming bridging hydrogen bonds and unstable ones that can be replaced. We demonstrated the application of HydraMap v.2 in explaining the structure-activity relationship of a panel of MCL-1 inhibitors. The desolvation energies calculated by summing the energy change of each hydration site before and after ligand binding showed good correlation with known ligand binding affinities on six target proteins. In conclusion, HydraMap v.2 offers a cost-effective solution for estimating the desolvation energy during protein-ligand binding and also is practical in guiding lead optimization in structure-based drug discovery.

Cooperation of Peripheral Hydrogen Atoms for the Stabilization of Aachno-pentaborane (11) with Small Molecules: Hydrogen Bonds and Dihydrogen Bonds

Post-Hartree-Fock calculations performed at the MP2/aug-cc-pVDZ level of theory has been used to analyze the formation of intermolecular complexes between B5H11 and W = CO, NCH, NH3, H2O or HOCH3. The interactions on the structure of the arachno-pentaborane(11) are manifested by the terminal and bridge hydrogen atoms, whereby are formed the hydrogen bonds (H∙∙∙Y with Y = O, C or N) as well as dihydrogen bonds (H∙∙∙H). In this context, the B5H11 shows a host-guest capability for trapping molecules, of course depending on the strength of each aforementioned interactions. The topological descriptors of the Quantum Theory of Atoms in Molecules (QTAIM) were decisive for unveiling each one of the following structures B5H11∙∙∙CO, B5H11∙∙∙NCH, B5H11∙∙∙NH3, B5H11∙∙∙H2O and B5H11∙∙∙HOCH3, and ideally, all hydrogen bonding formed by them.

Molecular Structures and Intermolecular Hydrogen Bonding of Silylated 2-Aminopyrimidines

A series of silylated 2-aminopyrimidines Me(4−n)Si(NHpyr)n (Me = methyl, NHpyr = pyrimid-2-ylamino, n = 1, 2, 3, 4), i.e., compounds 1, 2, 3, and 4, respectively, was prepared from a series of the respective chlorosilanes Me(4−n)SiCln and 2-aminopyrimidine. Triethylamine was used as a sacrificial base. Compounds 1, 2, 3, and 4 are solid at room temperature. They were analyzed using 1H, 13C, 29Si NMR, and Raman spectroscopy, and their molecular structures were confirmed by single-crystal X-ray diffraction analyses. All structures exhibit intramolecular van der Waals contacts between the silicon atom and one nitrogen atom of the pyrimidine moiety. Thus, their Si coordination spheres can be interpreted as [4+n] coordinated capped tetrahedra. Intermolecular hydrogen bonds (N–H···N bridges between the Si-bound amino groups and the non-Si-capping pyrimidine N atoms) are a constant contributor to the solid-state structures of these compounds. Furthermore, compounds 2 and 4 exhibit N–H···N bridges which involve 50% of their Si-capping N atoms as hydrogen bridge acceptors. Consequently, 50% of the non-Si-capping pyrimidine N atoms are stabilized by C–H···N contacts. As a result of a particularly dense network of intermolecular hydrogen bridges, the melting point of Si(NHpyr)4 (compound 4) is higher than 300 °C.

Encapsulation of atomized erythrocytes in liposomes as source of heme iron for oral supplementation strategies

AbstractThis work aimed to develop and characterize liposomes of atomized bovine erythrocytes (ABE‐liposomes) for potential use as a heme iron supplement or to fortify food with heme iron. Soy lecithin (SL) and Tween 80 (T80) were chosen to prepare empty liposomes (8 types), and ABE‐liposomes (16 types) by a rotary‐evaporated film method. Variables of interest for our study were: ABE concentration, proportion of SL:T80 and ultrasonic bath time. ABE‐liposomes were characterized according to appearance, color, morphology, Fourier transform infrared spectroscopy (FTIR), size, zeta potential, total iron content, encapsulation efficiency (EE) and in vitro iron release under gastrointestinal conditions. ABE‐liposomes presented a brown color and spherical shape. Hydrogen bridges were the main interactions in ABE‐liposomes. Their size ranged from 379 to 964 nm, the zeta potential from −56 to −74 mV, the iron concentration range was 0.8–9.0 mg/100 mL, and EE ranged from 29% to 48%. Ultrasonic bath time was the most important variable on the reduction of ABE‐liposomes' size and EE. Under in vitro gastrointestinal conditions, iron release from ABE‐liposomes occurred mainly at the intestinal level. In conclusion, ABE‐liposomes were effectively developed, which could become a complement for supplementation or food fortification strategies with nonheme for the prevention of iron deficiency anemia.Practical ApplicationsIn this study atomized bovine erythrocytes (ABE)‐liposomes were developed, due to the: (1) lack of supplements or products to fortify foods based on heme iron, (2) higher bioavailability of heme iron than nonheme iron, especially when working with ABE, and (3) ABE is a low value‐added product that is generated in slaughter plants and in turn is an excellent source of underutilized heme iron. In this study it was possible to develop ABE‐liposomes, where ABE was encapsulated inside liposomes, obtaining a product that could be used as a complement in iron supplementation strategies or food fortification to prevent or treat iron deficiency or iron deficiency anemia, especially in developing countries that have low consumption of heme iron.

Synthesis, characterization and identification of inhibitory activity on the main protease of COVID-19 by molecular docking strategy of (4-oxo-piperidinium ethylene acetal) trioxonitrate

In this investigation a single crystal of (4-oxo-piperidinium ethylene acetal) trioxonitrate (4-OPEAN) was synthesized by modifying the mechanism of gradual evaporation at ambient temperature. The operational groupings are found in the complex material in the elaborate substance, according to the infrared spectrum. Single crystal X-ray diffraction suggests, (4-OPEAN) with the chemical formula (C7H12NO2)NO3 belongs to the orthorhombic space group Pnma and is centrosymmetric in three dimensions with the aforementioned network configurations, a = 11.7185(8) Å, b = 7.2729(6) Å, c = 11.0163(8) Å, Z = 4, V = 938.89(12) Å3, R = 0.0725 and wR = 0.1762. Many NH…O and CH…O hydrogen bridges, both bifurcated and non-bifurcated, link the 4-oxo-piperidinium ethylene acetal cations to the trigonal (NO3−) anions. Molecular geometry and optimal parameters of (4-OPEAN) have been determined via DFT computations at the theory-level B3LYP/6-311 ++ G(d, p), these have been contrasted with the X-ray data already available. Hirshfeld surface analysis has made it possible for the visualization and quantification of relationships between molecules in the crystal composition. Quantum theory atoms in molecules, electron location function, decreased density gradient, and localized orbital locator research have all been used to explore non-covalent interactions in crystal structure. In order to pinpoint both the nucleophilic and electrophilic locations that support hydrogen bond formation, the molecule electrostatic potential was determined. The greatest and lowest energies of occupied and unfilled molecular orbitals, together with additional derived atomic characteristics, show the material to be extremely stable and hard. According to a molecular docking study, 4-OPEAN may exhibit inhibiting effects on the 6Y84 and 7EJY virus proteins from corona (COVID-19).

Catalytic Oxidation of VOC over Cobalt-Loaded Hierarchical MFI Zeolite

The zeolites ZSM-5 with different Si/Al ratios were modified with a buffer solution of HF and NH4F. This acidic treatment led to the obtaining of a material with secondary mesoporosity. The deposition of cobalt from an aqueous solution of cobalt acetate on the surface of treated samples generates the formation of different cobalt oxide species: bulk-like Co3O4 phases strongly interacting with the support, Co2+ in ion exchange positions (γ and β sites) and silicate-like phases. The mechanism of cobalt silicate phase formation is proposed here and includes a replacement of silanol groups and the bridging hydrogens by Co and the inclusion of the Co atoms in tetrahedral framework positions. The catalysts, obtained through use of the treated ZSM-5, exhibit higher activity in the reactions of propane, and n-hexane completes oxidation compared with the catalyst samples containing un-treated zeolite. Both the finer dispersion of metal oxide particles on the hierarchical sample and the presence of secondary mesoporosity improve the effectiveness of the active phase utilization via access to larger number of active sites.

Experimental and Simulation Studies on Hematite Interaction with Na-Metasilicate Pentahydrate.

Iron ore is a fundamental pillar in construction globally, however, its process is highly polluting and deposits are becoming less concentrated, making reusing or reprocessing its sources a sustainable solution to the current industry. A rheological analysis was performed to understand the effect of sodium metasilicate on the flow curves of concentrated pulps. The study was carried out in an Anton Paar MCR 102 rheometer, showing that, in a wide range of dosages, the reagent can reduce the yield stress of the slurries, which would result in lower energy costs for transporting the pulps by pumping. To understand the behavior observed experimentally, computational simulation has been used by means of quantum calculations to represent the metasilicate molecule and the molecular dynamics to study the adsorption of metasilicate on the hematite surface. It has been possible to obtain that the adsorption is stable on the surface of hematite, where increasing the concentration of metasilicate increases its adsorption on the surface. The adsorption could be modeled by the Slips model where there is a delay in adsorption at low concentrations and then a saturated value is reached. It was found that metasilicate requires the presence of sodium ions to be adsorbed on the surface by means of a cation bridge-type interaction. It is also possible to identify that it is absorbed by means of hydrogen bridges, but to a lesser extent than the cation bridge. Finally, it is observed that the presence of metasilicate adsorbed on the surface modifies the net surface charge, increasing it and, thus, generating the effect of dispersion of hematite particles which experimentally is observed as a decrease in rheology.