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We report small-sample evidence from a randomized experiment among a set of urban Ecuadorian households who owned both electric induction and gas stoves. We randomly assigned households to cook only with one stove during a prescribed two-day monitoring period, and then cook only with the other stove in a subsequent two-day period. The order of stove use was randomized, and air pollution was measured during each period. We found that mean 48-hour personal NO2exposure was 9.9 ppb higher (95% CI, 4.5-15.3) — a 50% increase over the 48-hour induction mean — when households were randomized to gas as compared to induction. Mean kitchen area NO2concentrations were 1 ppb higher (95% CI, 0.4-2.1) (a 6% increase) and mean personal PM2.5exposure was 11μgm−3higher (95% CI, -0.1-22.8) (a 44% increase) during study periods when randomized to gas. We use time-resolved cooking and pollution data to illustrate that these differences are driven by LPG cooking, which was associated with a 5.0 ppb increase in 5-minute average NO2kitchen area concentrations (95% CI, 3.4-6.7) and a 20.8μgm−3increase in 5-minute average personal PM2.5exposure (95% CI 8.9-32.6). In contrast, cooking with induction was not associated with changes to short-term NO2kitchen area concentrations, though it was associated with short-term increased personal PM2.5exposure (10.8, 95% CI, 5.7-15.9).

In this study, Crocin, Digitoxigenin, Beta-Eudesmol, and Favipiravir were docked in the active site of SARS-CoV-2 main protease (PDB code: 6LU7). The docking study was followed by Molecular Dynamics simulation. The result indicates that Crocin and Digitoxigenin are the structures with the best affinity in the studied enzyme's binding site. Still, Molecular Dynamics simulation showed that Digitoxigenin is the molecule that fits better in the active site of the main protease. Therefore, this molecule could have a more potent antiviral treatment of COVID-19 than the other three studied compounds. © 2021 by the authors.

We determined the optical profiles of a molecular system coupled with a thermal bath in presence of intramolecular coupling. Solvent effects were explicitly considered as a random variable by model...

The selenoenzyme glutathione peroxidase (GPx) like activity of stable organoselenium compounds has been evaluated through the initial rate (ν0) of the reduction reaction of H2O2, Cum-OOH, and t-BuO...

Breast cancer is the main cancer type with more than 2.2 million cases in 2020, and is the principal cause of death in women; with 685000 deaths in 2020 worldwide. The estrogen receptor is involved at least in 70% of breast cancer diagnoses, and the agonist and antagonist properties of the drug in this receptor play a pivotal role in the control of this illness. This work evaluated the agonist and antagonist mechanisms of 30 cannabinoids by employing molecular docking and dynamic simulations. Compounds with docking scores -8 kcal/mol were analyzed by molecular dynamic simulation at 300 ns, and relevant insights are given about the protein's structural changes, centered on the helicity in alpha-helices H3, H8, H11, and H12. Cannabicitran was the cannabinoid that presented the best relative binding-free energy (-34.96 kcal/mol), and based on rational modification, we found a new natural-based compound with relative binding-free energy (-44.83 kcal/mol) better than the controls hydroxytamoxifen and acolbifen. Structure modifications that could increase biological activity are suggested.

In the present work, the fast amide bond cleavage of [3-((1R,5S,7s)-3-azabicyclo[3.3.1]nonane-7-carbonyl)-3-azabicyclo[3.3.1]nonane-7-carboxylic acid (bi-ATDO)], through an intramolecular nucleophilic attack of an amine group is evaluated. First, six possible peptide bond cleavage mechanisms, two of them including a water molecule, are described at the ωB97XD/6-311 + G(d,p)//MP2/6-311 + G(d,p) level of theory. The reaction consisting of an intramolecular nitrogen nucleophilic attack followed by a proton transfer and the amide bond cleavage is determined as the most favorable mechanism. The activation free energy computed for the latter is 20.5 kcal mol-1 , which agrees with the reported experimental result of 24.8 kcal mol-1 . Inclusion of a water molecule to assist the first step of the reaction results in an activation free energy increase of about 17 kcal mol-1 . All the steps in the most favorable mechanism are studied more in detail employing intrinsic reaction coordinate as well as the reaction force and reaction electronic flux analysis.

A new phosphole derivative, 2,5-di(2-quinolyl)-1-phenylphosphole (1), was synthesized by using the Fagan–Nugent method. Phosphole 1 was obtained as an air-stable solid in high yield (73%). Addition...

Biodiesel from four different renewable resources was produced. An optimization of the reference methodology by gas chromatography was conducted based on the construction of calibration curves for each biodiesel during fatty acid methyl esters (FAME) quantification. Therefore, in the proposed optimized methodology, pure commercial standards are not necessary. Consequently, a reduction in the research expenses is achieved, making this methodology a cost-effective alternative for FAME quantification. The calibration curves obtained for each biodiesel presented slope values between 0.5–0.7 and regression coefficients (R2) > 0.98 in all cases. These results were compared to those obtained by the conventional methodology. With respect to the validation of the optimized methodology, a comparison of the results obtained by this proposed methodology and the reference one is presented. Finally, a robust and promising technique to quantify FAME present in biodiesel was successfully developed in this study.

Correlations among Shimura’s parameter (dCo) from spectrochemical series for 34 ligands and electronic descriptors from density functional theory calculations are reported. Simple and multiple linear regression models were constructed. The best results were obtained with the descriptors estimated with MN15 functional, obtaining a multiple linear regression model based on a quantitative structure–property relationship (QSPR) approach, with four attributes and the statistical parameters: R2 = 0.8543, Q2LOO = 0.8050, and Q2LMO = 0.7977. The four molecular descriptors are ligand field splitting (Δ), dipole moment (χC), enthalpy of the metal complex (HC) and the ligand HOMO energy (EHO_L). This model obtained for the Ni(0) complexes represents a novel approach to the spectroscopic series description based on computational tools also revising the models proposed from Werner’s description until modern recompilations carried out across the spectroscopic series developments. The applicability of the model was evaluated on cooper complexes and good prediction of the dCo values for some ligands was also obtained.

The nature of the Na⋯B bond, in the recently synthesized NaBH 3- adduct, is analyzed on the light of the Na- propensity to polarize along the bond axis as a consequence of the electric field produced by the BH3 fragment. The observed induced polarization has two consequences: (i) the energetic stabilization of the Na- , and (ii) the split of its valence electrons into two opposite lobes along the bond axis. Additionally, an analysis of the electron localization is presented using the information content of the correlated conditional pair density that reveals a significant delocalization between one lobe of the polarized Na- anion and the BH3 fragment at the equilibrium distance. Our findings reported here complement previous works on this system.

The topological profiles of the nonlinear optical properties of a two-level molecular system involving simplified versions of intramolecular coupling immersed in a thermal reservoir have been studied in four-wave mixing (FWM) spectroscopy. Solvent effects have been explicitly considered by modeling the nonradiative interaction with the solute as a random variable. To formulate a solution, it is necessary to introduce stochastic considerations. We assume that system–solvent interactions induce random shifts in the Bohr frequency of the adiabatic states, and their manifestation corresponds to the broadening of the upper level. The Born–Oppenheimer (BO) electronic energy curves for this molecular model consist of two intertwined harmonic oscillator potentials shifted in both their position and their minimum equilibrium energy. The critical quantities for this analysis are the transition and permanent dipole moments, which depend strongly on intramolecular coupling. Our results show how absorption and refractive index are affected by vibronic coupling and solvent stochasticity.

The occurrence, persistence, and accumulation of antibiotics and non-steroidal anti-inflammatory drugs (NSAIDs) represent a new environmental problem due to their harmful effects on human and aquatic life. A suitable absorbent for a particular type of pollutant does not necessarily absorb other types of compounds, so knowing the compatibility between a particular pollutant and a potential absorbent before experimentation seems to be fundamental. In this work, the molecular interactions between some pharmaceuticals (amoxicillin, ibuprofen, and tetracycline derivatives) with two potential absorbers, chitosan and graphene oxide models (pyrene, GO-1, and coronene, GO-2), were studied using the ωB97X-D/6-311G(2d,p) level of theory. The energetic interaction order found was amoxicillin/chitosan &gt, amoxicillin/GO-1 &gt, amoxicillin/GO-2 &gt, ibuprofen/chitosan &gt, ibuprofen/GO-2 &gt, ibuprofen/GO-1, the negative sign for the interaction energy in all complex formations confirms good compatibility, while the size of Eint between 24–34 kcal/mol indicates physisorption processes. moreover, the free energies of complex formation were negative, confirming the spontaneity of the processes. The larger interaction of amoxicillin GOs, compared to ibuprofen GOs, is consistent with previously reported experimental results, demonstrating the exceptional predictability of these methods. The second-order perturbation theory analysis shows that the amoxicillin complexes are mainly driven by hydrogen bonds, while van der Waals interactions with chitosan and hydrophobic interactions with graphene oxides are modelled for the ibuprofen complexes. Energy decomposition analysis (EDA) shows that electrostatic energy is a major contributor to the stabilization energy in all cases. The results obtained in this work promote the use of graphene oxides and chitosan as potential adsorbents for the removal of these emerging pollutants from water.

A copper(I) complex [CuCl{k1(P)-1a}{k2(P,N)-1a}] (1a = 2,5-bis(2-pyridyl)-1-phenylphosphole) with pseudo tetrahedral geometry was synthesized. In solution, 1a displays a hemilabile behaviour leading to a dynamic equilibrium between four and three-coordinate specie. Its catalytic potential was tested in synthesis of propargylamines and 1,2,3-triazoles via three-component reactions. Experimental results discussed on base to DFT calculations.

Coronavirus desease 2019 (COVID-19) is responsible for more than 1.80 M deaths worldwide. A Quantitative Structure-Activity Relationships (QSAR) model is developed based on experimental pIC50 values reported for a structurally diverse dataset. A robust model with only five descriptors is found, with values of R2 = 0.897, Q2LOO = 0.854, and Q2ext = 0.876 and complying with all the parameters established in the validation Tropsha’s test. The analysis of the applicability domain (AD) reveals coverage of about 90% for the external test set. Docking and molecular dynamic analysis are performed on the three most relevant biological targets for SARS-CoV-2: main protease, papain-like protease, and RNA-dependent RNA polymerase. A screening of the DrugBank database is executed, predicting the pIC50 value of 6664 drugs, which are IN the AD of the model (coverage = 79%). Fifty-seven possible potent anti-COVID-19 candidates with pIC50 values &gt, 6.6 are identified, and based on a pharmacophore modelling analysis, four compounds of this set can be suggested as potent candidates to be potential inhibitors of SARS-CoV-2. Finally, the biological activity of the compounds was related to the frontier molecular orbitals shapes.

Magnetic catalysts containing Fe and Ca synthesized in the presence of pectin have demonstrated to be highly efficient in the transesterification reaction for biodiesel production. Catalysts were prepared by the co-precipitation method under a N2 atmosphere with Na2CO3 from a mixture of FeSO4, FeCl3, Ca(NO3)2, and pectin followed by calcination at 550 ˚C/6h. The influence of the Fe:Ca molar ratio in the catalytic activity on the transesterification reaction with methanol was evaluated in the presence or absence of pectin. The most efficient catalyst was prepared in the presence of pectin with a Fe:Ca molar ratio of 4.5:2 (FCP2), and the best experimental conditions were at 3 % wt catalyst, 14:1 of methanol: soybean oil molar ration and 7.5 h of reaction time, which resulted in a methyl ester yield of 96.3%. It was shown that the presence of the biopolymer in the synthesis enhances the catalytic activity of the material from 20% to 99% of biodiesel production. All materials were fully characterized by TEM, FTIR, TGA, BET, XRD and DC magnetometry. It was found that catalysts present high surface areas with a nanometer size (∼20 nm), giving rise to a superparamagnetic state with a magnetic saturation high enough for separation by means of a magnet. In contrast, catalysts prepared in the absence of pectin demonstrated poor performance in the transesterification reaction of biodiesel in the optimized experimental conditions. The magnetic properties and the biopolymer role are discussed.

Twenty-four cannabinoids active against MRSA SA1199B and XU212 were optimized at WB97XD/6-31G(d,p), and several molecular descriptors were obtained. Using a multiple linear regression method, several mathematical models with statistical significance were obtained. The robustness of the models was validated, employing the leave-one-out cross-validation and Y-scrambling methods. The entire data set was docked against penicillin-binding protein, iso-tyrosyl tRNA synthetase, and DNA gyrase. The most active cannabinoids had high affinity to penicillin-binding protein (PBP), whereas the least active compounds had low affinities for all of the targets. Among the cannabinoid compounds, Cannabinoid 2 was highlighted due to its suitable combination of both antimicrobial activity and higher scoring values against the selected target, therefore, its docking performance was compared to that of oxacillin, a commercial PBP inhibitor. The 2D figures reveal that both compounds hit the protein in the active site with a similar type of molecular interaction, where the hydroxyl groups in the aromatic ring of cannabinoids play a pivotal role in the biological activity. These results provide some evidence that the anti-Staphylococcus aureus activity of these cannabinoids may be related to the inhibition of the PBP protein, besides, the robustness of the models along with the docking and Quantitative Structure&ndash, Activity Relationship (QSAR) results allow the proposal of three new compounds, the predicted activity combined with the scoring values against PBP should encourage future synthesis and experimental testing.

Zinc oxide (ZnO) quantum dots were synthesized in the presence of a columnar liquid crystalline perylene derivative. The liquid crystal molecules did not influence the nanoparticles' growth, and surprisingly they were efficient in stabilizing the colloidal dispersion over several months. For the first time, the quantity of ZnO units present in the ~4 nm sized ZnO nanoparticles was determined from the supramolecular interaction between the nanoparticles and the liquid crystal molecules as well as by analyzing the stoichiometry of the mixture. The quantity of ZnO units was also confirmed by theoretical studies performed by means of DFT calculations. The mixture was efficiently applied for methylene blue photodegradation.

Drug-induced liver injury (DILI) is a key safety issue in the drug discovery pipeline and a regulatory concern. Thus, many in silico tools have been proposed to improve the hepatotoxicity predictio...

In the present work, a number of R&ndash, X⋯NH3 (X = Cl, Br, and I) halogen bonded systems were theoretical studied by means of DFT calculations performed at the &omega, B97XD/6-31+G(d,p) level of theory in order to get insights on the effect of the electron-donating or electron-withdrawing character of the different R substituent groups (R = halogen, methyl, partially fluorinated methyl, perfluoro-methyl, ethyl, vinyl, and acetyl) on the stability of the halogen bond. The results indicate that the relative stability of the halogen bond follows the Cl &lt, Br &lt, I trend considering the same R substituent whereas the more electron-withdrawing character of the R substituent the more stable the halogen bond. Refinement of the latter results, performed at the MP2/6-31+G(d,p) level showed that the DFT and the MP2 binding energies correlate remarkably well, suggesting that the Grimme&rsquo, s type dispersion-corrected functional produces reasonable structural and energetic features of halogen bond systems. DFT results were also observed to agree with more refined calculations performed at the CCSD(T) level. In a further stage, a more thorough analysis of the R&ndash, Br⋯NH3 complexes was performed by means of a novel electron localization/delocalization tool, defined in terms of an Information Theory, IT, based quantity obtained from the conditional pair density. For the latter, our in-house developed C++/CUDA program, called KLD (acronym of Kullback&ndash, Leibler divergence), was employed. KLD results mapped onto the one-electron density plotted at a 0.04 a.u. isovalue, showed that (i) as expected, the localized electron depletion of the Br sigma-hole is largely affected by the electron-withdrawing character of the R substituent group and (ii) the R&ndash, X bond is significantly polarized due to the presence of the NH3 molecule in the complexes. The afore-mentioned constitutes a clear indication of the dominant character of electrostatics on the stabilization of halogen bonds in agreement with a number of studies reported in the main literature. Finally, the cooperative effects on the [Br&mdash, CN]n system (n = 1&ndash, 8) was evaluated at the MP2/6-31+G(d,p) level, where it was observed that an increase of about ~14.2% on the complex stability is obtained when going from n = 2 to n = 8. The latter results were corroborated by the analysis of the changes on the Fermi-hole localization pattern on the halogen bond zones, which suggests an also important contribution of the electron correlation in the stabilization of these systems.

The thermal decomposition of ethyl acetate was experimentally studied in a newly designed fast pyrolysis set-up. The results were compared to theoretical calculations and literature values in order to proof the experimental concept. The reaction was carried out in a free fall tubular reactor with a residence time of 0.15 s. The identification and quantification of products stream composition was performed online using a GC-TCD/FID. First, an overview of the reaction rate at feed volumes of 0.25, 0.50 and 0.75 mL was obtained at reaction temperature between 400 to 600 degrees C in intervals of 50 degrees C. As a result mass transfer limitation for feeds larger than 0.5 mL were identified. For the second approach, a constant feed volume of 0.25 mL and temperatures between 420 to 550 degrees C were investigated. Using the experimental results, a global kinetic model is proposed for the thermal decomposition of ethyl acetate into ethylene and acetic acid through a first order unimolecular reaction. Also, theoretical calculations were performed at wB97XD/6-311++G(d,p) level. A concerted mechanism through a six-membered transition state was identified in the reaction path. The theoretical and experimental activation energy values lie within the literature values between 193 and 213 kJ/mol. 2020 The Authors. Published by Elsevier B.V. on behalf of Institution of Chemical Engineers. This is an open access article under the CC BY-NC -ND license (http://creativecommons.orgilicenseseby-nc-nd/450/).

The reaction force formalism represents a convenient approach to analyze the course of a reaction step. From this analysis, the reaction path can be separated in a number of regions that are associated to either structural changes or electronic reorganization. This empirical observation is rationalized in this work on the basis of a simple two-state valence bond correlation diagram. We demonstrate that the ratio between the integrated reaction force and the region of interest ($$w_{\text{ii}}/w_{\text{i}}$$ for the forward reaction and $$w_{\text{iii}}/w_{\text{iv}}$$ for the backward reaction) increases with the ratio between the quantum mechanical resonance energy and the energy required to reach the crossing point at the transition state, we call to this ratio the strength of the resonance. This observation means that the size of the transition region (region ii and iii), that includes the transition state, depends on the strength of the resonance, and the structural zones (region i and iv), that are regions associated with the pure valence bond state curves (no resonance). We propose a simple analytical relationship for $$w_{\text{ii}}/w_{\text{i}}$$ and $$w_{\text{iii}}/w_{\text{iv}}$$ based on three parameters: (i) the quantum mechanical resonance energy, (ii) the energy of the reaction and (iii) the overlap between the VB structures at the transition state. The previous conclusions were supported by a reaction force analysis of a $${\text{S}}_{N}2$$ reactions, $${\text{X}}^{-} + {\text{CH}}_{3}{-}{\text{Y}} \rightarrow {{\text{X}}{-}{\text{CH}}}_{3} + {\text{Y}}^{-} ({\text{X}} = {\text{F}}, {\text{Cl}}, {\text{Br}})$$. The valence bond parameters for these reactions are estimated from empirical considerations. A very good agreement is found between the computed reaction force ratios and the predicted one.

In the present work, a molecular modelling has been performed on a total of 17 cinnamic acids, derived with different amino acids. These have recently been evaluated as potential α-glucosidase inhibitors. Consequently, we proposed a quantitative 3D structure–activity relationships in order to obtain predictive models of the biological activity. Two types of descriptors were used for the modelling: quantum chemical and multi-linear algebraic maps. The first one was obtained by using Density Functional Theory (DFT) at the M06/6-311++G(d,p) level, while for the second, attribute sets were obtained by using 3D molecular topology, atom weighed by physicochemical properties including the polar surface area, hardness, softness, van der Waals volume and charges. A genetic algorithm scheme was employed to determine the best subset of attributes for the application of the multiple linear regression. The most robust model (M4R_TD) was obtained with four multi-linear algebraic map descriptors (R2 = 0.946, Q2 = 0.901, F = 85.70), which indicate a good correlation between experimental and calculated results. Seven new simple structural modifications in the molecular core were suggested specifically for the three most active compounds (1, 2 and 5). The modifications to compound 1 appear to lead to an increase in the predicted activity from a pIC50 value of 9.872 to 10.656 in compound 1.3. The modifications to compound 2 do not affect an increase in the biological activity, and finally the modifications to compound 5 seem to increase the activity with a predicted pIC50= log[10/(10−6×IC50)]IC50 value of 10.094 for compound 5.1.

A computational study on the mechanisms of reaction for the pyrolysis of asparagine is presented. A density functional theory (DFT) study at the &omega, B97XD/6-311G(d,p) level was performed to analyze the differences in two reaction mechanisms: (i) the formation of five-membered cyclic products: maleimide and succinimide, and (ii) the more classical, six-membered cyclic products (diketopiperazine species) which are common in the pyrolysis of many other amino acids. The effect of temperature was included in the calculations at 300 &deg, C or 625 &deg, C, as required. Moreover, a detailed study based on the degree of rate control and thermodynamic control of the proposed mechanism for the formation of maleimide and succinimide is also presented. Results show that, for asparagine, the five-membered ring formation is the preferred process instead of the six-membered cycle (32 kJ/mol of Gibbs free energy difference between them at the first cyclization step), therefore, the polymerization is favored. On the other hand, the rupture of the polymer represents the highest energetic barrier (&Delta, G&Dagger, = 281 kJ/mol) and the most influential process in the overall rate of the reaction. These results are in good agreement with the experimental evidence.

Dapsone (DDS) is an antibacterial drug with well-known antioxidant properties. However, the antioxidant behavior of its derivatives has not been well explored. In the present work, the antioxidant activity of 10 dapsone derivatives 4-substituted was determined by an evaluation in two in vitro models (DPPH radical scavenging assay and ferric reducing antioxidant power). These imine derivatives 1–10 were obtained through condensation between DDS and the corresponding aromatic aldehydes 4-substuited. Three derivatives presented better results than DDS in the determination of DPPH (2, 9, and 10). Likewise, we have three compounds with better reducing activity than dapsone (4, 9, and 10). In order to be more insight, the redox process, a conceptual DFT analysis was carried out. Molecular descriptors such as electronic distribution, the total charge accepting/donating capacity (I/A), and the partial charge accepting/donating capacity (ω+/ω−) were calculated to analyze the relative donor-acceptor capacity through employing a donor acceptor map (DAM). The DFT calculation allowed us to establish a relationship between GAPHOMO-LUMO and DAM with the observed antioxidant effects. According to the results, we concluded that compounds 2 and 3 have the lowest Ra values, representing a good antioxidant behavior observed experimentally in DPPH radical capturing. On the other hand, derivatives 4, 9, and 10 display the best reducing capacity activity with the highest ω− and Rd values. Consequently, we propose these compounds as the best antireductants in our DDS imine derivative series.

In the present study, the most favourable reaction mechanism in the flash vacuum pyrolysis of 2-[(2E)-2-benzylidenehydrazinyl]pyridine and analogous was theoretically studied using B3LYP-D3/6-311G(d,p) level. The influence of different substituents on the phenyl ring in the para position is evaluated at 500 K. A deep analysis of the mechanisms reveals the influence of the substituents in the activation energy, where the reactivity order OCH3 > CH3 > H > Cl > NO2 is found, following Hammet parameters (σp). To reach the transition state, geometric changes contribute more than 70% of the energy in agreement with the reaction force analysis. A recent independent gradient model (IGM) is also applied to establish an influence between the substituent and the strength of the bonds involved in the mechanism, through an intrinsic bond strength index (IBSI). Furthermore, the influence of the substituent was also evaluated in terms of interatomic distances and evolution percentages, finding high correlations with Hammet σp values.