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A new synthesized Schiff base, N-((anthracen-9-yl) methylene-2-methyl benzenamine) (AMMB), was prepared from o-toluidine and 9-anthracenecarboxaldehyde. The structure of the compound was confirmed by single crystal X-ray diffraction and characterized through various analytical tools such as high resolution mass, 1H and 13C NMR, infrared, UV-vis and elemental composition analysis. The molecular geometries of AMMB were optimized by means of DFT/B3LYP/6311-G++ (d,p) basis set. The optimized geometric parameters of the compound were concordant with the single crystal structure. The optimized structure was utilized in comparison of experimental FT-IR with calculated frequency calculation. TD-DFT analysis was performed to compute the electronic absorption of the compound. SCF-GIAO was employed to compute 1H and 13C NMR, which was consistent with the experimental results. Additionally, NLO, NBO, MEP and global reactivity parameters were also computed using the same level of theory. Hirshfield surface analysis, fingerprint plot and energy frameworks were presented to explore the intermolecular interactions within the crystal. Molecular docking study was carried out to predict the probable binding site of AMMB into lipid bilayers such as DMPC, DPPC, POPC, DLPE, DOPC and POPE. The molecular docking analysis of AMMB showed complex formation with binding affinity energy ranging from −9.3 to −3.4 kcal/mol. [ABSTRACT FROM AUTHOR]

The corrosion inhibition activity of indole derivatives has been systematically examined by calculating quantum chemical parameters including energy of the highest occupied molecular orbital, energy of the lowest unoccupied molecular orbital, energy difference, molecular hardness, molecular softness, and the number of electrons exchanged between the metal and the corrosion inhibitor at the B3LYP/6-311++G (d,p) level of theory. The results demonstrate that derivatives containing the electron-donating groups exhibit superior efficiency in inhibiting iron corrosion compared to indole. Additionally, an investigation into the corrosion inhibition ability of derivatives containing the NH2 group reveals that 6-NH2-indole emerges as the most effective inhibitor, boasting an efficiency value of 97.11%. These calculated outcomes align with previously studied experimental results, underscoring the remarkable corrosion resistance of derivatives containing electron-donating groups.

This study aimed to address the issue of the low solubility in the model drug probenecid (PRO) and its impact on bioavailability. Two salts of probenecid (PRO), 4-aminopyridine (4AMP), and 4-dimethylaminopyridine (4DAP) were synthesized and characterized by PXRD, DSC, TGA, FTIR, and SEM. The crystal structures of the two salts were determined by SCXRD, demonstrating that the two salts exhibited different hydrogen bond networks, stacking modes, and molecular conformations of PRO. The solubility of PRO and its salts in a phosphate-buffered solution (pH = 6.8) at 37 °C was determined, the results showed that the solubility of PRO salts increased to 142.83 and 7.75 times of the raw drug, respectively. Accelerated stability experiments (40 °C, 75% RH) showed that the salts had good phase stability over 8 weeks. Subsequently, Hirshfeld surface (HS), atom in molecules (AIM), and independent gradient model (IGM) were employed for the assessment of intermolecular interactions. The analyses of salt-forming sites and principles were conducted using molecular electrostatic potential surfaces (MEPs) and pKa rules. The lattice energy (EL) and hydration-free energy (EHF) of PRO and its salts were calculated, and the relationships between these parameters and melting points and the solubility changes were analyzed. [ABSTRACT FROM AUTHOR]

The current work targets to discover the potential of two pyrimidine derivatives, ethyl 4-[4-(dimethylamino)phenyl]-6-methyl-2-sulfanylidene-1,2,3,4-tetrahydropyrimidine-5-carboxylate (ESP) and 4-[4-(dimethylamino)phenyl]-6-methyl-N-phenyl-2-sulfanylidene-1,2,3,4-tetrahydropyrimidine-5-carboxamide (DSP), for the protection of C1018 steel from acidic corrosion. Electrochemical tests like electrochemical impedance spectroscopy, linear polarization resistance, potentio-dynamic polarization, and electron frequency modulation were employed for assessing the anticorrosive capability of the synthesized ESP and DSP. Both ESP and DSP inhibitors exhibited great inhibition activity, and the inhibition effectiveness attained 88.6 % for ESP and 94.9 % for DSP at saturation concentration.EIS data for ESP and DSP exposes that inhibition efficacy enhances with an increase in the doses of the two inhibitors by creating a protective film. The finest explanation for the adsorption of the examined molecules on the Fe surface was provided by the Langmuir model. The surface morphology was also evaluated by using SEM and EDX techniques. Computational studies like DFT and MC simulation methods were employed to determine the connection between anticorrosion performance and the inhibitor structure, which agrees with the experimental outcomes.

This study undertakes a detailed theoretical investigation into the iso‐pentanol radical isomerization and decomposition kinetics and the mechanism development of the iso‐pentanol oxidation. The CCSD(T)/CBS//M08‐HX/6‐311+G(2df,2p) method was adopted to calculate the reaction potential energy surface. The reaction rate coefficients were calculated by variational transition state theory (VTST) with multistructural torsional (MS‐T) partition function and small curvature tunneling (SCT) correction. Moreover, the pressure‐dependent rate coefficients were determined using the system‐specific quantum Rice‐Ramsperger‐Kassel theory (SS‐QRRK). The variational and tunneling effects were discussed, and the dominant reaction channels were identified. It reveals that the isomerization reactions play a significant role at low temperatures, while the decomposition reactions dominate the high‐temperature regime. Notably, the quantitative rate expressions for iso‐pentanol radical decomposition reactions were also obtained. Furthermore, a new kinetic model incorporating the calculated rate coefficients was constructed, exhibiting satisfactory prediction performance on ignition delay times and improved predictive accuracy of species mole fractions. This work provides accurate rate data of isomerization and decomposition kinetics and contributes to a more comprehensive understanding of the iso‐pentanol oxidation mechanism. [ABSTRACT FROM AUTHOR]

In this work, a novel organic–inorganic hybrid-based Fe3O4 nanoparticles was developed to remove metal ion and organic contaminants from aqueous solutions with the most serious environmental problems. In order to remove pollutants including Mercury(II) chloride (HgCl2), Alpha lipoid acid (ALA), Methyl orange (MO), Fe3O4@SiO2@APTS functionalized oxidized chitosan (Fe3O4@SiO2@APTS-OCS) was synthesized, and these composites were characterized by FT-IR, XRD, FE-SEM, VSM and BET techniques. In addition, a simple and fast multi-stage heating method was provided to produce mercury chloride under a closed laboratory system. The purification of mercury (II) chloride showed > 99.99%. Then, Hg2+, ALA and MO removal can be carried out by Fe3O4@SiO2@APTS-OCS with the optimum equilibrium conditions. The adsorbent catalyst dosage Fe3O4@SiO2@APTS-OCS was obtained 0.35 g/L. The initial concentration parameter for Hg2+, ALA and MO removal was calculated 30 mg/L. In addition, optimum initial pH value for Hg2+, ALA and MO removal was obtained 11, 1 and 1, respectively. After six consecutive cycles, Hg2+, ALA and MO adsorption by nano-composite were decreased from 89.0 to 78.0%, 85.0 to 76.0%, and 92 to 79, respectively. The quantum and molecular dynamic calculations were studied to obtain optimization of structures and removal of Hg2+, ALA and MO by Fe3O4@SiO2@APTS-OCS in Materials Studio 2017 software. Based on the negative adsorption energy (ΔEads) of Hg2+, ALA and MO on nanoparticles, the simulation system was the stability and placed spontaneously in parallel above Fe3O4@SiO2@APTS-OCS by forming hydrogen bonds and van der Waals. [ABSTRACT FROM AUTHOR]

Abstract Magnetite-functionalized biochar (MBC) is a promising engineered material for remediation of antibiotic-contaminated fields. However, sorption mechanisms of ionizable organic compounds such as sulfonamide antibiotics (SAs) on MBC are still unclear. This study employed four representative SAs including sulfamethazine (SMT), sulfamerazine (SMR), sulfadiazine (SDZ), and sulfamethoxazole (SMX), to compare the difference in sorption on MBC. Results showed that the sorption capacities and affinities of the four SAs varied with their substituents, hydrophobic properties, and dissociation constants (pK a). Synergistic effect during co-pyrolysis with Fe3+ enhanced the sorption performance of MBC towards SAs compared to original BC. Spectral methods confirmed structural changes of MBC such as the variance in oxygen-containing groups and defective/graphitized phases. Results of modeling pH-dependent sorption revealed that H-bonding or π-bond assisted H-bonding determined the sorption affinities and capacities of SAs. In particular, the SAs with lower pK a were thermodynamically favorable to form H-bonding with MBC via proton exchange with water molecules. Quantum calculation results quantified the contributions of H-bonding strengths and found that the energies of H-bonding were correlated with affinities of SAs. Moreover, contributions of oxygen-containing groups instead of minerals dominated the H-bonding energies. Mechanistic insights from this study can be valuable in exploring engineered BC composites for practical application in field remediation. Graphical Abstract

BackgroundLignin peroxidases catalyze a variety of reactions, resulting in cleavage of both β-O-4' ether bonds and C-C bonds in lignin, both of which are essential for depolymerizing lignin into fragments amendable to biological or chemical upgrading to valuable products. Studies of the specificity of lignin peroxidases to catalyze these various reactions and the role reaction conditions such as pH play have been limited by the lack of assays that allow quantification of specific bond-breaking events. The subsequent theoretical understanding of the underlying mechanisms by which pH modulates the activity of lignin peroxidases remains nascent. Here, we report on combined experimental and theoretical studies of the effect of pH on the enzyme-catalyzed cleavage of β-O-4' ether bonds and of C-C bonds by a lignin peroxidase isozyme H8 from Phanerochaete chrysosporium and an acid stabilized variant of the same enzyme.ResultsUsing a nanostructure initiator mass spectrometry assay that provides quantification of bond breaking in a phenolic model lignin dimer we found that catalysis of degradation of the dimer to products by an acid-stabilized variant of lignin peroxidase isozyme H8 increased from 38.4% at pH 5 to 92.5% at pH 2.6. At pH 2.6, the observed product distribution resulted from 65.5% β-O-4' ether bond cleavage, 27.0% Cα-C1 carbon bond cleavage, and 3.6% Cα-oxidation as by-product. Using ab initio molecular dynamic simulations and climbing-image Nudge Elastic Band based transition state searches, we suggest the effect of lower pH is via protonation of aliphatic hydroxyl groups under which extremely acidic conditions resulted in lower energetic barriers for bond-cleavages, particularly β-O-4' bonds.ConclusionThese coupled experimental results and theoretical explanations suggest pH is a key driving force for selective and efficient lignin peroxidase isozyme H8 catalyzed depolymerization of the phenolic lignin dimer and further suggest that engineering of lignin peroxidase isozyme H8 and other enzymes involved in lignin depolymerization should include targeting stability at low pH.

This study aimed to address the issue of the low solubility in the model drug probenecid (PRO) and its impact on bioavailability. Two salts of probenecid (PRO), 4-aminopyridine (4AMP), and 4-dimethylaminopyridine (4DAP) were synthesized and characterized by PXRD, DSC, TGA, FTIR, and SEM. The crystal structures of the two salts were determined by SCXRD, demonstrating that the two salts exhibited different hydrogen bond networks, stacking modes, and molecular conformations of PRO. The solubility of PRO and its salts in a phosphate-buffered solution (pH = 6.8) at 37 °C was determined, the results showed that the solubility of PRO salts increased to 142.83 and 7.75 times of the raw drug, respectively. Accelerated stability experiments (40 °C, 75% RH) showed that the salts had good phase stability over 8 weeks. Subsequently, Hirshfeld surface (HS), atom in molecules (AIM), and independent gradient model (IGM) were employed for the assessment of intermolecular interactions. The analyses of salt-forming sites and principles were conducted using molecular electrostatic potential surfaces (MEPs) and pKa rules. The lattice energy (EL) and hydration-free energy (EHF) of PRO and its salts were calculated, and the relationships between these parameters and melting points and the solubility changes were analyzed.

Magnetite-functionalized biochar (MBC) is a promising engineered material for remediation of antibiotic-contaminated fields. However, sorption mechanisms of ionizable organic compounds such as sulfonamide antibiotics (SAs) on MBC are still unclear. This study employed four representative SAs including sulfamethazine (SMT), sulfamerazine (SMR), sulfadiazine (SDZ), and sulfamethoxazole (SMX), to compare the difference in sorption on MBC. Results showed that the sorption capacities and affinities of the four SAs varied with their substituents, hydrophobic properties, and dissociation constants (pKa). Synergistic effect during co-pyrolysis with Fe3+ enhanced the sorption performance of MBC towards SAs compared to original BC. Spectral methods confirmed structural changes of MBC such as the variance in oxygen-containing groups and defective/graphitized phases. Results of modeling pH-dependent sorption revealed that H-bonding or π-bond assisted H-bonding determined the sorption affinities and capacities of SAs. In particular, the SAs with lower pKa were thermodynamically favorable to form H-bonding with MBC via proton exchange with water molecules. Quantum calculation results quantified the contributions of H-bonding strengths and found that the energies of H-bonding were correlated with affinities of SAs. Moreover, contributions of oxygen-containing groups instead of minerals dominated the H-bonding energies. Mechanistic insights from this study can be valuable in exploring engineered BC composites for practical application in field remediation. Highlights: Sorption capacity and affinity of four SAs varied with substituents, Kow, and pKa Copyrolyzed carbon matrix and Fe3+ synergistically enhanced SA sorption performance H-bonding or π-bond assisted H-bonding determined SA sorption affinity and capacity Contributions of O-containing groups instead of minerals dominated H-bonding energy [ABSTRACT FROM AUTHOR]

Context: Benzene and other aromatic groups, as planar groups with π electrons cloud, tend to form stacking interactions which have an important role in various chemical and biological processes. In order to have a better insight in the nature of these interactions, we have performed a fractal analysis on patterns of electron density and electrostatic potential for two benzenes in stacking interaction. The calculated fractal dimension follows the trend of the calculated interaction energy for the interplanar distances of 4.0 to 6.0 Å, which partially coincides with the strongest attractive stacking interactions. The fractal dimension vs. energy dependences were fitted with the logistic curve, and the fitting coefficient was 0.96 up to 1.00. Methods: For the benzene stacking interaction energy, with a range of conformations and distances between two benzenes, DFT calculations at the B3LYP+D3/aug-cc-pVDZ level were performed with the TURBOMOLE software. The fractal analysis for electron density and electrostatic potential has been done by python scripting. [ABSTRACT FROM AUTHOR]

Objective: to formulate the bases for quantum law as the law of the future, based on the study of quantum phenomena and features of quantum technologies determining the risks and challenges associated with the emergence of these technologies, as well as the analysis of legal regulation of quantum technologies in the Russian Federation and abroad.Methods: to carry out this research, the authors applied a complex of general scientific methods of systemic analysis and specific methods of engineering and legal sciences. The use of comparative-legal method allowed revealing the main directions of developing legal regulation of quantum technologies in the Russian and foreign law orders based on the analysis of their international and national regulation. The method of legal modeling allowed forming a concept of quantum law, revealing the main vectors of its development and the complex of its ethical-legal principles.Results: the features and properties of quantum technologies were revealed which can change the development of law with the advent of these technologies; the main risks and challenges were identified which are associated with the development of quantum technologies; the features of quantum technologies regulation in some foreign countries were specified; the trends of developing the quantum technologies regulation in the Russian Federation were identified; the conceptual bases of quantum law were formulated, as well as the vectors of its development.Scientific novelty: for the first time in the legal science, a complex analysis of the current national (both Russian and foreign) regulation of quantum technologies was carried out, based on which an attempt was made to substantiate the need to form quantum law and to outline the main vectors of its development.Practical significance: the research results lay the foundation for forming the concept of quantum law; in this regard, the authors’ conclusions and proposals for improving the current regulation of quantum technologies can be used in law-making and law enforcement in this sphere, and may lay the bases for further research in the sphere of quantum technologies.

One of the main ways that metallic materials lose their useful qualities is through dissolution; hence corrosion management is crucial for protecting the metal. In this paper, new thienylpicolinamidine derivatives, namely; 5-[5-(3,4,5-trimethoxyphenyl)thiophen-2-yl]picolinamidine hydrochloride salt (MA-1517), 5-[5-(4-methoxyphenyl)thiophen-2-yl]picolinamidine hydrochloride salt (MA-1543), and 5-[5-(3-chloro-4-methoxyphenyl)thiophen-2-yl]picolinamidine hydrochloride salt (MA-1516), were utilized as corrosion inhibitors for C-steel in 1.0 mol L−1 HCl. Their corrosion inhibiting impact can be demonstrated by experimental methods as chemical approaches (mass reduction) and electrochemical techniques (electrochemical impedance examination, EIS, and Tafel polarization). These methods gave inhibition efficiencies (IE%) of 97.41 %, 93.84 % and 91 % for MA-1517, MA-1543 and MA-1516, respectively at 323 K and concentration 17 × 10−6 mol. L−1. The rise in IE% with rising inhibitor concentration and temperature illustrate that the adsorption of these studied compounds is chemisorption, declared via the Langmuir isotherm. Thermodynamic and kinetic parameters are computed and discussed. Polarization research exhibits that these thienylpicolinamidines act as mixed type inhibitors. The outer part morphology of C-steel surfaces and the adsorption of these compounds on C-steel outer part can be checked by atomic force microscopy (AFM), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX). The mechanism of inhibition can be backed by quantum chemical examination and Monte Carlo model. A theoretical estimate proves that the use of cationic derivatives of pyridine is good impediments versus corroding of C-steel in HCl medium. [ABSTRACT FROM AUTHOR]

Aim: To evaluate using bioinformatics tools the interactions between plant protease inhibitors (PIs) and SARS-CoV-2 Mpro. Materials & methods: This was an in silico study based on molecular docking, molecular dynamics simulations and quantum biochemistry calculations. Results: The plant PIs pineapple cystatin and sesame cystatin interacted allosterically with Mpro, leading to significant structural alterations. These conformational changes lead to a reduction of the area and volume of the Mpro proteolytic site, likely affecting the protease activity and, consequently, reducing viral replication. Conclusion: This work highlights the therapeutic potential of plant PIs as candidates for future in vivo investigations into new therapeutics for COVID-19. [ABSTRACT FROM AUTHOR]

The quantum transport properties of ZnO devices with five different bulk configurations are investigated with numerical methods. The calculation results reveal that the transport property at a higher energy range can be tuned by changing the length of central scattering. By substituting some Zn atoms with Cu atoms, it is found that the doped Cu atoms have an obvious effect on the quantum properties at the entire energy range investigated, and could result in different transmission. The properties of ZnO devices are also influenced by the doping positions of Cu atoms. The tuning mechanism relies on the shifting of carrier distributions in the scattering center of the device. [ABSTRACT FROM AUTHOR]

• The inhibition performance of two Gemini cationic surfactants (GCs-O and GCs) for carbon steel in formation water solution was studied. • The inhibitors have 91.04 % and 89.11 % inhibition efficiencies after 6 h for GCs-O and GCs respectively. • The inhibitors form a stable protective film on carbon steel surface at different temperatures. • Carbon steel surface analysis results confirmed the efficacy of the prepared inhibitors. • Quantum calculations assured the experimental results. Carbon steel (CS) metal is considered the basic of numerous industries; however, it is highly susceptible to being corroded in various offensive environments. CS corrosion is an inevitable but manageable process. Utilizing inhibitors to reduce the media's aggressiveness toward metallic components is an efficient technique for corrosion control. Two Gemini cationic surfactants (GCs & GCs-O) that differ in their spacer were synthesized and verified using FT-IR and 1HNMR spectroscopy. The critical micelle concentration (CMC) was obtained by surface tension and conductivity measurements. The inhibition performance of the studied GCs and GCs-O in formation water (FW) was evaluated using electrochemical measurements (potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS). After adding the synthesized inhibitors, the electrochemical experiments demonstrated that CS corrosion resistance increased. The inhibition efficiency increased till reach 92.73 % and 90.11 % in the presence of GCs-O and GCs inhibitors respectively using the PP technique. The obtained PP data showed that the synthesized GCs-O and GCs acted as mixed-type inhibitors with high mitigation potency which reflected the accumulation of inhibitors molecules on the surface of CS via their adsorption nature. The adsorption mechanism of the investigated GCs and GCs-O followed Langmuir adsorption isotherm. Also, the achieved SEM (scanning electron microscopy), EDX (energy-dispersive X-ray), and AFM (Atomic Force Microscope) analysis confirmed the mitigation effect of GCs and GCs-O inhibitors through their adsorption process over the CS surface. Theoretical quantum calculations, like DFT (density functional theory) and MCs (Monte Carlo simulations), indicated the high potential reactivity of the studied GCs and GCs-O towards corrosive species that confirmed their inhibition performance and supported the experimental results. [ABSTRACT FROM AUTHOR]

[Display omitted] • R∙+HO 2 ↔ ROOH→R-CHO+H 2 O and R∙+HO 2 → vdw complex → R+3O 2 were added to the mechanism. • The reactive sites of DMF and 2MF were studied. • Improved ignition delay prediction accuracy with updated reaction rate constants. A valuable alternative to traditional fuels, bio-oxygenated fuels provide benefits. Oxygenated fuels 2,5-dimethylfuran (DMF) and 2-methylfuran (2MF) perform well. This study used quantum chemical calculations and combustion simulations to evaluate the combustion characteristics of low and medium temperature combustion mechanisms. Conclusions: In the combustion reaction of DMF and 2MF, the H-abstraction reaction occurs mainly at the methyl site. The reaction between macromolecular radicals and HO 2 at low and middle temperatures plays a critical role in fuel auto-ignition. Thus, R∙+HO 2 ↔ ROOH→R-CHO+H 2 O and R∙+HO 2 → vdw complex → R+3O 2 were added to the mechanism. Modified mechanism improves temperature prediction accuracy. The HOMO-LUMO gap is narrowed by the methyl group, which is closely related to the reaction sites and the molecular structure. After H-abstraction, the methyl site is the most likely to react, followed by the C3 and C5 sites. [ABSTRACT FROM AUTHOR]

An efficient method for prediction in the capture of SO2 from flue gas by imidazolium ionic liquids was reported, where the concentration of SO2 is 2000 ppm. On the basis of quantitative calculations through a combination of Langmuir simulation, theoretical calculation and quantum chemical method, SO2 absorption and desorption performance from flue gas by twelve kinds of imidazolium ionic liquids with different anions were designed and predicted. Then, among them, five kinds of imidazolium ionic liquids were chosen and prepared to investigate their behavior of SO2 absorption capacity, desorption residue, and available absorption capacity. The results indicated that the experimental values were in good agreement with the predicted values. Thus, an ideal ionic liquid [Emim][Tetz] was obtained through the predictive method for the capture of SO2 of 2000 ppm, which showed high available absorption capacity of 0.24 g SO2 per g ionic liquid and excellent reversibility.

Hydrolyzable chlorine is a well-known residue issued from the synthesis of epoxy resin, which may impart specific dielectric properties. In this work, the changes in distributed energy levels and charge trap depths of the molecule containing such defects are investigated using quantum chemical calculations. These changes are analyzed from the microscopic perspectives of electron energy structure and electron cloud offset. The charge transport and charge injection behavior in epoxy materials before and after the hydrolysis are predicted using the analysis results. The volume resistivities and space charges of epoxy materials with three different hydrolyzable chlorine contents are tested at different hygrothermal aging times, which are consistent with the previous predictions. These results are used to explain the ac breakdown strength of these epoxy materials at different hygrothermal aging times. It is indicated that the structural changes (electronegativity and atomic position changes) of the molecule containing hydrolyzable chlorine before and after hydrolysis change the spatial distribution of electron cloud density between and on valence bonds, and in turn, change the energy levels of different molecular segments. This results in a large increase in the overall electron trap depth and a small decrease in the overall hole trap depth of the molecule after hydrolysis. [ABSTRACT FROM AUTHOR]

The Aeluropus lagopoides (ALG) was used as an eco-friendly green inhibitor to prevent carbon steel (C.S) corrosion in one molar HCl. Based on the GC-MS results, 36 compounds are identified in the studied extract. The corrosion inhibition efficiency (%IE) of ALG for C.S in one molar HCl has been calculated by utilized chemical technique [weight loss (WL)] and electrochemical tests [potentiodynamic polarization (PP) method and AC impedance spectroscopy (EIS)]. The extract acted as a mixed-type metal corrosion inhibitor according to the potentiodynamic polarization results. The adsorption of ALG on C.S followed the Langmuir adsorption isotherm. The inhibition efficiency increased by lowering the temperature. EIS revealed that the ALG extract formed a thin protective film on the C.S surface. The adsorption of ALG on C.S surface was confirmed via scanning electron microscope (SEM), Energy Dispersion Spectroscopy X-ray spectra (EDX), and Atomic force Microscopy (AFM). Moreover, the biological effect of the ALG was measured and indicate ALG has a kindly impact in preventing multiplying bacteria. Monte Carlo simulations are also executed to simulate the adsorption of ALG extract on iron surface. The theoretical results were in a good agreement with experimental measurements. [ABSTRACT FROM AUTHOR]

Abstract Background Lignin peroxidases catalyze a variety of reactions, resulting in cleavage of both β-O-4′ ether bonds and C–C bonds in lignin, both of which are essential for depolymerizing lignin into fragments amendable to biological or chemical upgrading to valuable products. Studies of the specificity of lignin peroxidases to catalyze these various reactions and the role reaction conditions such as pH play have been limited by the lack of assays that allow quantification of specific bond-breaking events. The subsequent theoretical understanding of the underlying mechanisms by which pH modulates the activity of lignin peroxidases remains nascent. Here, we report on combined experimental and theoretical studies of the effect of pH on the enzyme-catalyzed cleavage of β-O-4′ ether bonds and of C–C bonds by a lignin peroxidase isozyme H8 from Phanerochaete chrysosporium and an acid stabilized variant of the same enzyme. Results Using a nanostructure initiator mass spectrometry assay that provides quantification of bond breaking in a phenolic model lignin dimer we found that catalysis of degradation of the dimer to products by an acid-stabilized variant of lignin peroxidase isozyme H8 increased from 38.4% at pH 5 to 92.5% at pH 2.6. At pH 2.6, the observed product distribution resulted from 65.5% β-O-4′ ether bond cleavage, 27.0% Cα-C1 carbon bond cleavage, and 3.6% Cα-oxidation as by-product. Using ab initio molecular dynamic simulations and climbing-image Nudge Elastic Band based transition state searches, we suggest the effect of lower pH is via protonation of aliphatic hydroxyl groups under which extremely acidic conditions resulted in lower energetic barriers for bond-cleavages, particularly β-O-4′ bonds. Conclusion These coupled experimental results and theoretical explanations suggest pH is a key driving force for selective and efficient lignin peroxidase isozyme H8 catalyzed depolymerization of the phenolic lignin dimer and further suggest that engineering of lignin peroxidase isozyme H8 and other enzymes involved in lignin depolymerization should include targeting stability at low pH.

The anticorrosion potency of Sabic mild steel (MS) in 0.5 M H2SO4 solution was enhanced by three synthetic non-ionic surfactants (NI Surf.) containing pyridine and pyrimidine derivatives. These compounds are safe, environmentally friendly, and harmless to human health. Chemical and electrochemical measurements were used to compute the corrosion parameters. The anticorrosion efficacy increases with increasing the concentration of NI Surf. and with lowering temperature, surface and interfacial tension, and critical micelle concentration. The effectiveness of anticorrosion is interpreted due to the spontaneous horizontal adsorption on the surface of MS by the existence of some active centers that facilitate the adsorption. The adsorption process obeys Temkin isotherm. Potentiodynamic polarization elucidated that the synthetic NI Surf. acted as mixed-type inhibitors. Some surface properties were determined and confirm the anticorrosive effect of these molecules. Quantum chemical parameters as reactivity descriptors were carried out. It should be noted that the results obtained from computational calculations of the specifications are in full agreement with the experimental observations. There is good compatibility between the anticorrosion efficiency obtained from various techniques and surface properties and quantum chemical calculation.

The corrosion behavior of Al in 1 M HCl solution with and without thiophene derivatives is studied utilizing altered chemical and electrochemical methods. Thiophene derivatives have been prepared and characterized by infrared (IR), proton nuclear magnetic resonance (1H NMR) and mass spectral studies. The corrosion data were obtained using weight reduction and electrochemical techniques. The outcome data revealed that the efficiency rises with improving the dose of thiophene derivatives in aggressive solution, while it lowered with the rise of temperature. The adsorption of the studied thiophene derivatives on the surface of Al follows Langmuir isotherm. The thermodynamic parameters such as adsorption constant Kads and free energy of adsorption () are calculated and discussed. Polarization curves indicated that the thiophene derivatives are mixed-kind inhibitors. The quantum calculation such as EHOMO, ELUMO and ΔE were obtained and related to the experimental data. The biological effect of these derivatives also discussed. [ABSTRACT FROM AUTHOR]

The quantum transport properties of ZnO devices with five different bulk configurations are investigated with numerical methods. The calculation results reveal that the transport property at a higher energy range can be tuned by changing the length of central scattering. By substituting some Zn atoms with Cu atoms, it is found that the doped Cu atoms have an obvious effect on the quantum properties at the entire energy range investigated, and could result in different transmission. The properties of ZnO devices are also influenced by the doping positions of Cu atoms. The tuning mechanism relies on the shifting of carrier distributions in the scattering center of the device.

The anticorrosion potency of Sabic mild steel (MS) in 0.5 M H2SO4 solution was enhanced by three synthetic non-ionic surfactants (NI Surf.) containing pyridine and pyrimidine derivatives. These compounds are safe, environmentally friendly, and harmless to human health. Chemical and electrochemical measurements were used to compute the corrosion parameters. The anticorrosion efficacy increases with increasing the concentration of NI Surf. and with lowering temperature, surface and interfacial tension, and critical micelle concentration. The effectiveness of anticorrosion is interpreted due to the spontaneous horizontal adsorption on the surface of MS by the existence of some active centers that facilitate the adsorption. The adsorption process obeys Temkin isotherm. Potentiodynamic polarization elucidated that the synthetic NI Surf. acted as mixed-type inhibitors. Some surface properties were determined and confirm the anticorrosive effect of these molecules. Quantum chemical parameters as reactivity descriptors were carried out. It should be noted that the results obtained from computational calculations of the specifications are in full agreement with the experimental observations. There is good compatibility between the anticorrosion efficiency obtained from various techniques and surface properties and quantum chemical calculation. [ABSTRACT FROM AUTHOR]

• Synthetic additives unite leveling and superfilling inhibitors for feature filling. • Intermolecular synergism between inhibitors weakens the adsorption of imidazole. • Intramolecular synergism between inhibitors enhances the adsorption of imidazole. • Increase in polyether chain length weakens the intramolecular synergism. Additives are crucial in the electroplating metallization for damascene features, among which hybrid additives with both superfilling and leveling capabilities have attracted much attention, yet their inhibition mechanism remains to be further explored. In this work, hybrid additives named IDZ-PEs, which comprise imidazole and polyethers with varying degrees of polymerization, were designed and prepared to reveal the inter- and intramolecular synergism between superfilling and leveling inhibitors. In addition, mixtures of imidazole and polyether were applied for comparison. Electrochemical tests and quantum calculations demonstrated that IDZ-PEs exhibited both superfilling and leveling capabilities. The intermolecular synergism between independent imidazole and polyether weakens the inhibition of polyether by changing its active adsorption sites. In contrast, the intramolecular synergism between imidazole and polyether enhances the inhibition from both components, and the enhancement reduces with the increasing polyether polymerization. Furthermore, the void-free filling of damascene features was achieved with IDZ-PEs, demonstrating that IDZ-PEs were effective suppressors for damascene copper electrodeposition. The explanation of the synergism between superfilling and leveling inhibitors provides further insights into the mechanism of hybrid additives. [Display omitted] [ABSTRACT FROM AUTHOR]

Many energetic materials synthesized to date have limited applications because of low thermal and/or mechanical stability. This limitation can be overcome by introducing structural modifications such as a bridging group. In this study, a series of 1,3,4‐oxadiazole‐bridged furazans was prepared. Their structures were confirmed by 1H and 13C NMR, infrared, elemental, and X‐ray crystallographic analyses. The thermal stability, friction sensitivity, impact sensitivity, detonation velocity, and detonation pressure were evaluated. The hydroxylammonium salt 8 has an excellent detonation performance (D=9101 m s−1, P=37.9 GPa) and insensitive properties (IS=17.4 J, FS=330 N), which show its great potential as a high‐performance insensitive explosive. Using quantum computation and crystal structure analysis, the effect of the introduction of the 1,3,4‐oxadiazole moiety on molecular reactivity and the difference between the sensitivities and thermal stabilities of mono‐ and bis‐1,3,4‐oxadiazole bridges are considered. The synthetic method for introducing 1,3,4‐oxadiazole and the systematic study of 1,3,4‐oxadiazole‐bridged compounds provide a theoretical basis for future energetics design. [ABSTRACT FROM AUTHOR]

Clarithromycin has significant antibacterial effect against Gram positive bacteria, and has been widely used as an important clinical antibiotic at present. As a derivative of microbial secondary metabolites, however, clarithromycin products have a large number of impurities, and some trace impurities also need further structural analysis. In this study, the mass spectrometric fragmentation reactions of clarithromycin K and its impurities of KL and KO were systematically studied by electrospray ionization tandem mass spectrometry ( ESI-MS/ MS) and quantum calculation. Quantum calculation showed that the amino N atom of deoxyaminoglycosides ( the No. 5 side chain unit) is the most preferred protonation site in the structure of clarithromycin. Upon collisional activation, the protonated molecules undergo a serie of proton migration and fragmentation reactions on side chain groups as the followings: 1) The ionizing proton transfers to the 0 5a atom in the No. 5 side chain group and triggers the loss of macrolides to form an oxoniumion of the dehydrided deoxyaminoglycoside (KSa-P, m/ z 158.1). 2) The ionizing proton transfers to the 05b atom in the No. 5 side chain group, which triggers the ring-opeaning reaction of the deoxyaminoglycosides group to give a characteristic fragment ion of N-(3-hydroxybutylidene)-N-methylmethanaminium (KSc-P, m/ z 11 6. 1 ). 3) Migration of the ionizing proton to the 06 atom results in the loss of methanol. 4) Migration of t he ionizing proton to the 03a atom results in the formation of K3a, which undergoes migration of the pyranose unit due to the nucleophilic attack of the 05d atom of the No. 5 side chain unit, and the subsequent loss of macrolides to form anoxoniumion at m/ z 316. 2 (K3a-1P). 5) K3a can also undergo nucleophilic reaction due to the nucleophilic attack of the 03c atom of the para hydroxyl, and subsequent fragmentation to produce the characteristic ion K3a-2P by losing C8 H12O3, and further cleavage to give the characteristic ion K3a-2P-P via the loss of methanol. The impurities of KL and KO have high similarity to clarithromycin in structure, which only differ in the No. 9 side chain unit. As expected, they have very similar tandem mass spectra, in which there are several characteristic neutral losses of CH4O, C8 H12 O3 and (C8 H12 O3 + CH4O) in the high mass region, and abundant characteristic fragment ions at m/z 316, m/z 158 and m/z 11 6 in the low mass region. This work summarizes the MS fragmentation law of clarithromycin and its analogue, provides a reference for the structure derivation of the other impurities of clarithromycin and it metabolites. [ABSTRACT FROM AUTHOR]

Clarithromycin has significant antibacterial effect against Gram positive bacteria. and has been widely used as an important clinical antibiotic at present. As a derivative of microbial secondary metabolites, however. clarithromycin products have a large number of impurities, and some trace impurities also need further structural analysis. In this study. the mass spectrometric fragmentation reactions of clarithromycin K and its impurities of KL and KO were systematically studied by electrospray ionization tandem mass spectrometry (ESI-MS/MS) and quantum calculation. Quantum calculation showed that the amino N atom of deoxyaminoglycosides (the No. 5 side chain unit is the most preferred protonation site in the structure of clarithromycin. Upon collisional activation, the protonated molecules undergo a serie of proton migration and fragmenta tion reactions on side chain groups as the followings: 1) The lonizing proton transfers to the O5a atom in the No, 5 side chain group and triggers the loss of macrolides to form an oxonium ion of the dehydrided deoxyaminoglycoside (K5a-P, m/z 158. 1). 2) The ioni- zing proton transfers to the 05b atom in the No. 5 side chain group, which triggers the ning opesting reaction of the deoxyaminoglycosides group to give a characteristic frog mention of N-(3-hydroxybutylidene)-N-methylmethanaminium (K5e-P, m/= 116. 1). 3) Migration of the ionizing proton to the 06 atom results in the loss of methanol: Migration of the ionizing proton to the 03a atom results in the formation of K3a, which undergoes migration of the pyranose unit due to the nucleophilic attack of the 05 atom of the No. 5 side chain unit, and the subsequent loss of macrolides to form an oxo nium ion stm/z 316.2 (K3a-1P), 5) K3a can also undergo nucleophilic reaction due to the nucleophilic attack of the O3c atom of the pura hydroxyl, and subsequent fragmen tation to produce the characteristic ion K3-2P by losing C, H,O,. and further cleavage to give the characteristic ion K3a-2P-P via the loss of methanol. The impurities of KL and KO have high similarity to clarithromycin in structure. which only differ in the No. 9 side chain unit. As expected. they have very similar tandem mass spectra, in which there are several characteristic neutral losses of CH4O,C8H12O3, and (C8H12O3+ CH4O) in the high mass region. and abundant characteristic fragment ions at m/z 316. m/z 158 and m/z 116 in the low mass region. This work summarizes the MS fragmentation law of clarithromycin and its analogue. provides a reference for the structure derivation of the other impurities of clarithromycin and it metabolites. [ABSTRACT FROM AUTHOR]

Amino acid modified polyaspartic acids were evaluated as calcium‐scale inhibitors. Feasibility of scale inhibition experiments was analyzed by molecular dynamics simulation and Gaussian optimization, and the scale inhibition mechanism was theoretically analyzed. Scale inhibition performance was studied by scanning electron microscopy, X‐ray diffraction, X‐ray photoelectron spectroscopy, static scale inhibition experiments, and electrochemical performance testing, which provided an experimental basis for the molecular dynamics simulation. The experimental results showed that Arg‐SA‐PASP has better scale inhibition and corrosion inhibition performance than His‐SA‐PASP. The scale inhibition effect increased with increasing concentration. Electrochemical tests indicated that Arg‐SA‐PASP is an excellent scale and corrosion inhibitor. [ABSTRACT FROM AUTHOR]

In this paper, space charge behavior over a large range of electric field and temperature, of two kinds of epoxy resins are investigated using an improved pulsed electro-acoustic method. Significant influence of high electric field and high temperature on the space charge accumulation in epoxy are found. Hetero charge accumulation starts to build up at 80 °C under 120 kV/mm for amine-type hardener cured epoxy (EP-AM), while at 140 °C under 60 kV/mm for anhydride-type hardener cured epoxy (EP-AH). The accumulated charge increases with the increasing of electric field and temperature. The maximum enhancement of local electric field of is 135 and 123 % at 140 °C for EP-AM and EP-AH, respectively. Quantum chemical calculation is performed to clarify the mechanism of space charge characteristics in the two types of epoxy. It is indicated that ionization of remnant unreacted hardener and electrode injection may be the main sources of space charge. The interaction between molecular chains of EP-AH is stronger than that of EP-AM, which makes it have better space charge characteristics even under high temperature. [ABSTRACT FROM AUTHOR]

Despite the common use of salens and hydroxyquinolines as therapeutic and bioactive agents, their metal complexes are still under development. Here, we report the synthesis of novel mixed-ligand metal complexes (MSQ) comprising salen (S), derived from (2,2′-{1,2-ethanediylbis[nitrilo(E) methylylidene]}diphenol, and 8-hydroxyquinoline (Q) with Co(II), Ni(II), Cd(II), Al(III), and La(III). The structures and properties of these MSQ metal complexes were investigated using molar conductivity, melting point, FTIR, 1H NMR, 13C NMR, UV–VIS, mass spectra, and thermal analysis. Quantum calculation, analytical, and experimental measurements seem to suggest the proposed structure of the compounds and its uncommon monobasic tridentate binding mode of salen via phenolic oxygen, azomethine group, and the NH group. The general molecular formula of MSQ metal complexes is [M(S)(Q)(H2O)] for M (II) = Co, Ni, and Cd or [M(S)(Q)(Cl)] and [M(S)(Q)(H2O)]Cl for M(III) = La and Al, respectively. Importantly, all prepared metal complexes were evaluated for their antimicrobial and anticancer activities. The metal complexes exhibited high cytotoxic potency against human breast cancer (MDA-MB231) and liver cancer (Hep-G2) cell lines. Among all MSQ metal complexes, CoSQ and LaSQ produced IC50 values (1.49 and 1.95 µM, respectively) that were comparable to that of cisplatin (1.55 µM) against Hep-G2 cells, whereas CdSQ and LaSQ had best potency against MDA-MB231 with IC50 values of 1.95 and 1.43 µM, respectively. Furthermore, the metal complexes exhibited significant antimicrobial activities against a wide spectrum of both Gram-positive and -negative bacterial and fungal strains. The antibacterial and antifungal efficacies for the MSQ metal complexes, the free S and Q ligands, and the standard drugs gentamycin and ketoconazole decreased in the order AlSQ > LaSQ > CdSQ > gentamycin > NiSQ > CoSQ > Q > S for antibacterial activity, and for antifungal activity followed the trend of LaSQ > AlSQ > CdSQ > ketoconazole > NiSQ > CoSQ > Q > S. Molecular docking studies were performed to investigate the binding of the synthesized compounds with breast cancer oxidoreductase (PDB ID: 3HB5). According to the data obtained, the most probable coordination geometry is octahedral for all the metal complexes. The molecular and electronic structures of the metal complexes were optimized theoretically, and their quantum chemical parameters were calculated. PXRD results for the Cd(II) and La(III) metal complexes indicated that they were crystalline in nature.

The identities and properties of ‘Novichok’ (Russian for ‘newcomer’ or ‘novice’) agents allegedly used in the recent terrorist attack in the UK have not been well documented. Although several people previously involved in the synthesis of these materials claimed Novichok agents to be five to eight times more potent than VX, a deadly nerve agent, no open data on these species are currently available. To bridge this gap, we herein performed a theoretical study on several Novichok agent candidates and conducted natural population charge analysis to evaluate the possible mechanisms of their toxicity, suggesting that these agents might promote the ageing and deformation of acetylcholinesterase. Moreover, the reaction of Novichok agents with acetylcholinesterase serine was calculated to be most thermodynamically favoured for Novichok candidate A234. Thus, this work is believed to provide a basis for finding Novichok antidotes and should inspire further detoxification studies to prepare for possible terrorist attacks in the future.

Deep trap sites have been proved able to suppress charge injection into nanocomposites even under high electric field. In order to reveal the mechanism of deep trap sites in epoxy/graphene nanocomposite, the trap distribution was obtained through surface potential decay (SPD) method. The energy levels and 3D potential distributions of epoxy and single-layer graphene under vertical or various parallel electric fields were calculated by using the density functional theory (DFT). The experimental and calculation results indicate that doping with graphene sheets introduces deep trap sites in epoxy/graphene composite. Under parallel electric field, the apparent dipoles of single-layer graphene build positive and negative potential wells in pairs, which capture carriers as the trap sites in epoxy/graphene composite. While a vertical electric field seems to have no effect on the trap sites. For better performance in suppressing charge injection, the doped graphene sheets should be exposed partially to a parallel electric field. [ABSTRACT FROM AUTHOR]

Abstract Nine phosphonates surfactant were synthesized by two steps. The first step was condensation between acetaldehyde and butyl amine, dodecylamine or hexadecylamine individually to give three corresponding Schiff bases, and then the Schiff base products were added to dibutyl phosphite individually. The second step was reaction of the phosphonate products with polyethylene glycol 400, 600 and 1000 to get on the nine water soluble phosphonate corrosion inhibitors. The products were characterized by FTIR, 1HNMR and 13CNMR spectroscopic techniques. The surface active properties of this phosphonate were calculated and they were evaluated as corrosion inhibitors in formation water formulations using open circuit potential and potentiodynamic polarization. The quantum calculations of the structures were calculated and the data obtained were nearly closed with the experimental data. HMPA1 shows the best results as corrosion inhibitors (efficiency 94%) at lowest concentration 15 ppm. The corrosion inhibition mechanism was discussed on the basis of surface tension measurements and the electronic data. Graphical abstract Unlabelled Image Highlights • Nine novel phosphonates were synthesized and characterized by spectroscopic methods. • Electrochemical techniques were used to evaluate as corrosion inhibitors. • Quantum was applied to the synthesized phosphonate to predict their efficiencies. • The percentage inhibition efficiency (IE%) of the surfactants increases by decrease the alkyl chain and the ethylene units. [ABSTRACT FROM AUTHOR]

Graphical abstract A nickel(II) complex with a new Schiff base derived from 2,4-dihydroxyacetophenone has been synthesized and spectroscopically characterized. Density Functional Theory (DFT) approach was successfully used for investigation of its structural and spectral characteristics. Antibacterial assay was done and DFT calculations were used to explain its antibacterial activity. Abstract The molecular geometry, vibrational frequencies and gauge including atomic orbital (GIAO) 1H NMR chemical shift values of the title molecule, N,N ′-bis-(4-hydroxy-α-methylsalicylidene)ethylenediamine nickel(II) complex, (C 18 H 18 N 2 NiO 4) in the ground state have been calculated using density functional theory (DFT) method with general (GEN) and 6-311++G(d,p) basis set, respectively. The theoretical results were compared with the experimental data. Calculated results show that DFT can well reproduce the structure of the title compound. The theoretical vibrational frequency and 1H NMR chemical shift values show good agreement with experimental data. In addition, by using time dependent (TD)-DFT method, a good agreement between the predicted electronic absorption and experimental values are observed. [ABSTRACT FROM AUTHOR]

• Corn gluten meal hydrolysate (molecular weight less than 1 kDa) exhibited high antioxidant activity. • A novel antioxidant peptide was identified as Arg-Tyr-Leu-Leu (RYLL) from the hydrolysate. • Tyrosine was the main active site in RYLL based on quantum calculation. • Peptide structure and hydrogen bond network improved antioxidant activity of RYLL. The antioxidant activity of corn peptides is related to their molecular weight and structure. Corn gluten meal (CGM) was hydrolyzed using a combination of Alcalase, Flavorzyme and Protamex, and the hydrolysates were subjected to antioxidant activity analysis after further fractionation. Corn peptides with molecular weights less than 1 kDa (CPP1) exhibited excellent antioxidant activity. A novel peptide, Arg-Tyr-Leu-Leu (RYLL), was identified from CPP1. RYLL displayed preferable scavenging capacities for ABTS radicals and DPPH radicals, with IC 50 values of 0.122 mg/ml and 0.180 mg/ml, respectively. Based on quantum calculations, RYLL had multiple antioxidant active sites, and tyrosine was the main active site due to the highest energy of the highest occupied molecular orbit (HOMO). Moreover, the simple peptide structure and hydrogen bond network of RYLL contributed to the exposure of the active site. This study elucidated the antioxidant mechanism of corn peptides, which could provide an understanding for CGM hydrolysates as natural antioxidants. [ABSTRACT FROM AUTHOR]

Soluble guanylate cyclase (sGC) is a key enzyme implicated in various physiological processes such as vasodilation, thrombosis and platelet aggregation. The enzyme's Heme-Nitric oxide/Oxygen (H-NOX) binding domain is the only sensor of nitric oxide (NO) in humans, which on binding with NO activates sGC to produce the second messenger cGMP. H-NOX is thus a hot target for drug design programs. BAY60-2770 and BAY58-2667 are two widely studied activators of sGC. Here we present comparative molecular dynamics studies to understand the molecular details characterizing the binding of BAY60-2770 and BAY58-2667 with the human H-NOX (hH-NOX) and bacterial H-NOX (bH-NOX) domains. HartreeFock method was used for parametrization of both the activators. A 50 ns molecular dynamics (MD) simulation was run to identify the functionally critical regions of the H-NOX domains. The CPPTRAJ module was used for analysis. BAY60-2770 on binding with bH-NOX, triggered rotational movement in signaling helix F and significant dynamicity in loops α and β, but in hH-NOX domain the compound showed relatively lesser aforementioned structural fluctuations. Conversely, hH-NOX ligated BAY58-2667 experienced highest transitions in its helix F due to electrostatic interactions with D84, T85 and R88 residues which are not conserved in bH-NOX. These conformational transformations might be essential to communicate with downstream PAS, CC and cyclase domains of sGC. Comparative MD studies revealed that BAY bound bHNOX dynamics varied from that of hH-NOX, plausibly due to some key residues such as R40, F74 and Y112 which are not conserved in bacteria. These findings will help to the design of novel drug leads to cure diseases associated to human sGC. [ABSTRACT FROM AUTHOR]

A global glide disorder has been discovered during an X‐ray investigation of the crystal structure of (Z)‐2‐[(E)‐(4‐methoxybenzylidene)hydrazinylidene]‐1,2‐diphenylethanone (MHDE, C22H18N2O2) at room temperature. In another crystal, however, such disorder disappears (still at room temperature). Even though the disorder may be partly due to the poor quality of the harvested crystal, the structure can shed light on the nature of disorder. With the help of quantum chemical calculations, it is found that the global disorder seems to be connected with the need for stabilization of the somewhat rigid but mobile and unstable molecular structure. The most relevant feature driving the packing of the disordered structure concerns the slight perturbations (such as glide) of two or more disorder components (fractional occupancies) distributed throughout the crystal. [ABSTRACT FROM AUTHOR]

This work aims to investigate the inhibitory activity of capsaicin, which is one of capsaicinoid compounds, on these enzymes using a molecular docking and quantum calculation. Acarbose, a commercial diabetes drug, was also investigated for comparison. The docking results revealed that acarbose yields better inhibition efficiency with binding free energy (ΔGbinding) of about -8.2 to -11.9 kcal/mol, and inhibition constant (Ki) of about 0.0002 to 0.4 µM, where as capsaicin provided the ΔGbinding of -5.8 to -6.1 kcal/mol and Ki of 23.7 to 45.9 µM. The total binding energy (ΔEbinding) between each inhibitor and amino acids in active site of enzyme obtained from quantum calculation with MP2/6-31G(d,p) level is in agreement with the ΔGbinding, i.e. the ΔEbinding of acarbose was larger negative than that of capsaicin. The amino acids interacting with inhibitor as hydrogen bond mainly contribute to the total binding energy. Nevertheless, it could be concluded that capsaicinoids have high potential to be developed as an alternative drug for diabetes disease. [ABSTRACT FROM AUTHOR]

Summary: In the modeling of hydrocarbon thermal cracking processes, complicated reaction networks of multicomponent reactants make kinetic parameter predictions very challenging. To solve this problem, the additivity method and Evans‐Polanyi equation were proposed for the prediction of kinetic factors. As the calculation of kinetic parameters using quantum chemical theory was used for higher accuracy, new additivity methods at the quantum theory level were developed for the prediction of thermodynamic kinetic parameters. At the same time, a reaction class transition state theory RC‐TST, analogous to the Evans‐Polanyi equation, was proposed by considering quantum factors for kinetic constant evaluation. Quantum calculation methods promoted mechanistic studies of electronic effects to accurately reveal the kinetic constant rules with different structural factors. Under these circumstances, kinetic parameter predictions by different quantum chemical computation methods were firstly introduced and reviewed. Meanwhile, development of the new additivity method and RC‐TST theory at the quantum chemistry level were summarized, and the new outlook on electronic effects with an appropriate quantum chemical computational method into the new additivity method was conducted to develop more perspicuous and accuracy in a simplified method for the calculation of complicated thermal cracking reaction. [ABSTRACT FROM AUTHOR]

The charge density analysis of meloxicam sodium monohydrate [sodium 4-hydroxy-2-methyl-N-(5-methyl-1,3-thiazol-2-yl)-1,1-dioxo- 1$l^{6},2-benzothiazine-3-carboxamide monohydrate] was performed with high-resolution X-ray diffraction data measured at low temperature (90 K). The experimental results were compared with those derived from the corresponding periodic theoretical calculations at the B3LYP/6-31G** level of theory. The multipolar charge-density analysis highlights the regions of meloxicam which are the most electronegative. These regions correspond to those forming short electrostatic interactions with the Na+ cation. The molecular conformation in the crystal is maintained by a strong intramolecular N-H···O=C hydrogen bond. The Na+ cation interacts with as much as five neighboring oxygen atoms. The strong hydrogen bonds N/O-H···O/N, the Na···O short contacts and hydrophobic aromatic stacking between the two aromatic cycles constitute the most represented and enriched contact types and act as the driving force in the crystal packing formation. The crystal packing presents several meloxicam anion dimers but also one Na+···Na+ repulsive interactions which are largely compensated by the electrostatic favorable attractions between anions and cations. [ABSTRACT FROM AUTHOR]