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The heat of mixing of some petrological relevant substitutions (i.e., Mg-Al, Si-Al, Mg-Ti, Mg-Ca, and Mg-Fe) was investigated systematically in silicates, titanates, tungstates, carbonates, oxides, hydroxides, and sulphates by density functional theory calculations (e.g., melilite, chlorite, biotite, brucite, cordierite, amphibole, talc, pseudobrookite, pyroxene, olivine, wadsleyite, ilmenite, MgWO4, ringwoodite (spinel), perovskite, pyrope-grossular, magnesite-calcite, MgO-CaO, anhydrous and different hydrated MgSO4). A specific substitution is characterised by different microscopic interaction energies in different minerals, e.g., the octahedral Mg-Al exchange on a single crystallographic site in pyroxene has a microscopic interaction energy that is more than twice compared to that in biotite. A comparative investigation of the heat of mixing using microscopic interaction energies on a single crystallographic site has the advantage that they are not influenced by cation ordering. They could be successfully correlated with the stiffnesses of the minerals, which in turn were scaled to the oxygen packing fraction, a parameter that is easily available for poorly investigated minerals. With this information, the interaction energies of a certain substitution can be transferred from minerals where they are well-known to mineral groups where they are less- or unknown. Using the cross-site terms and the microscopic interaction energies, the macroscopic interaction energies of the coupled substitution, e.g., Mg + Si = Al + Al, of biotite and pyroxene were calculated, which are, however, affected by cation ordering and different degrees of local charge balance, for which appropriate models are necessary. [ABSTRACT FROM AUTHOR]

We have investigated the basic mechanism of carbon nanotube (CNT) interactions with various room-temperature ionic liquids (RTILs) using molecular dynamics (MD) simulations. To understand the effects of the cation molecular geometry on the properties of the interface structure in the RTIL systems, we have studied a set of three RTILs with the same [BF4]- (tetrafluoroborate) anion but with different cations, namely, [EMIM]+ (1-ethyl-3-methylimidazolium), [BMIM]+ (1-butyl-3-methylimidazolium), [HMIM]+ (1-hexyl-3-methylimidazolium), and [OMIM]+ (1-octyl-3-methylimidazolium) ions. The simulation results showed that the imidazolium cations exhibit two distinct orientations (perpendicular and parallel to the CNTs surface) at the interface irrespective of the alkyl chain length of the cations. The average number of hydrogen bonds per cations inside the CNT was found to be higher for [OMIM][BF4] (1.01), which suggests that [OMIM]+ imidazolium rings to be concentrated at the center of the CNT, which favors hydrogen bond. The reported results show the diffusion coefficients of ions in confinement are much lower in comparison to the bulk region. The interaction energy between [OMIM][BF4] (-8.75 kcal.mol−1.ion−1) and CNT was found to be higher as compared to other ILs. The cations paralleling the CNT surface are thermodynamically significantly more stable because of the substantial interfacial π-π stacking interactions, as shown by a comparison with the calculated interaction energies between cations and the CNTs. Our simulation results provide a molecular-level understanding of the stabilization and dispersion of CNT bundles in ILs. [ABSTRACT FROM AUTHOR]

A computational study on the host–guest complexes of neutral bis(4-nitrophenyl)squaramide (SQ) and halide anions is reported. In the gas-phase, the calculated interaction and stabilization energies indicates a diminishing intrinsic affinity of SQ for anions from fluoride to iodide. The nature of interactions is investigated using Natural Bond Orbital (NBO), Quantum Theory of Atoms in Molecules (QTAIM) along with Energy Decomposition Analysis-Natural Orbitals for Chemical Valence (EDA-NOCV). While electrostatic interactions account for roughly 60% of the total, EDA-NOCV analysis demonstrated increasing contributions of orbital interactions from SQ ⋯ I - to SQ ⋯ F - complexes. In solution, thermodynamic cycle analyses and Gibbs free energy calculations reveal a propensity towards the formation of SQ ⋯ F - , taking into account the influence of solvation energies on the overall stability. The consistent trend observed in selectivity both in the gas phase and in solution suggests that changes in solvation energy do not significantly impact the stability of complexes. The findings were additionally supported by a significant correlation observed between the computed and experimental formation constants. [ABSTRACT FROM AUTHOR]

When nano-fillers are used to enhance the thermal conductivity of organic phase change materials (PCMs), the naturally formed interface is considered to hinder thermal transport of the composite PCMs. However, the effect of the interface on the thermal properties of surrounding PCM has not been fully studied. In this paper, three composite PCMs (Ery@SiC, Ery@SiO2 and Ery@Si3N4) were prepared by melt-blending method. The local thermal conductivity and reduced Young's modulus (E⋆) of the erythritol at the interface and far away from the interface in the composite PCMs were simultaneously measured by scanning thermal microscopy (SThM). The results revealed significant enhancement in local thermal conductivity of erythritol at the interface and its obvious positive correlation with E⋆. For different composite PCMs, molecular dynamics (MD) simulations suggested that the increase in intrinsic thermal conductivity and E⋆ of erythritol is attributed to the increase in interaction energy between erythritol and nanoparticles, as more erythritol phonon vibrations transform from localized mode to delocalized mode and erythritol has a higher density at the interface. These findings will provide new ideas for the design of PCM for energy storage. [ABSTRACT FROM AUTHOR]

Environmental friendly biocomposites are urgently needed to mitigate the pollution caused by huge consumption of petroleum-based polymers. Renewable carrageenan and polylactic acid (PLA) natural polymers have the potential to replace petroleum-origin polymers. Nevertheless, the carrageenan and PLA themselves inherit poor tensile strength, hydrophobicity and stability. The aim of this study is to underpin the mechanism of synthesis of carrageenan-PLA biocomposite using van't Hoff plot, 1HNMR and density functional theorem simulation. Strong hydrogen bonding was found at 1.88 Å between O atom (carrageenan) and H atom (PLA) and was validated in 1HNMR shifting at 5.3 ppm corresponding to –OH group from PLA. The interaction established in the biocomposite mixed at 50 °C leads to a stronger tensile strength of 75.37 MPa, higher hydrophobicity and thermal stability with highest activation energy of 45.39 kJ/mol. The biocomposite produced from renewable carrageenan-PLA material would be a future replacement for nondegradable plastic as a food packaging material. [ABSTRACT FROM AUTHOR]

Let Ω ⊂ R 2 and let L ⊂ Ω be a one-dimensional set with finite length L = | L | . We are interested in minimizers of an energy functional that measures the size of a set projected onto itself in all directions: we are thus asking for sets that see themselves as little as possible (suitably interpreted). Obvious minimizers of the functional are subsets of a straight line but this is only possible for L ≤ diam (Ω) . The problem has an equivalent formulation: the expected number of intersections between a random line and L depends only on the length of L (Crofton's formula). We are interested in sets L that minimize the variance of the expected number of intersections. We solve the problem for convex Ω and slightly less than half of all values of L: there, a minimizing set is the union of copies of the boundary and a line segment. [ABSTRACT FROM AUTHOR]

Three cocrystals of acridine with 2,7-dihydroxynaphthalene (Ia and Ib) in two different polymorphs and 1,5-dihydroxynaphthalene (II) have been synthesized and characterized by single crystal X-ray diffraction method. Two polymorphs of acridine, 2,7-dihydroxynaphthalene cocrystal crystallizes in same space group with different unit-cell parameters. In (Ia) the O–H group form a syn-anti conformation whereas in (Ib) the O–H group form an anti-anti conformation leads to the polymorphic structure of acridine, 2,7-dihydroxynaphthalene. This study reveals that the influence of π⋯π and C–H⋯π interactions in the formation of one-, two-, and three-dimensional supramolecular frameworks when the classical hydrogen bonds such as O–H⋯N and C–H⋯O are limited to discrete motifs. The acridine molecules form continuous π⋯π stacking in the crystal structure of (Ia) and discrete π⋯π stacking in the crystal structure of (Ib) and (II). The conformational flexibility of the substituted hydroxy group has an influence in the supramolecular frameworks of the three-dimensional crystal structure. The intermolecular interaction energy calculation between the molecular pairs has been carried out to study the strength of the interaction and its dependence on the geometrical parameters. [ABSTRACT FROM AUTHOR]

Here, we introduce the use of ANI-ML potentials as a rescoring function in the host–guest interaction in molecular docking. Our results show that the “docking power” of ANI potentials can compete with the current scoring functions at the same level of computational cost. Benchmarking studies on CASF-2016 dataset showed that ANI is ranked in the top 5 scoring functions among the other 34 tested. In particular, the ANI predicted interaction energies when used in conjunction with GOLD-PLP scoring function can boost the top ranked solution to be the closest to the x-ray structure. Rapid and accurate calculation of interaction energies between ligand and protein also enables screening of millions of drug candidates/docking poses. Using a unique protocol in which docking by GOLD-PLP, rescoring by ANI-ML potentials and extensive MD simulations along with end state free energy methods are combined, we have screened FDA approved drugs against the SARS-CoV-2 main protease (Mpro). The top six drug molecules suggested by the consensus of these free energy methods have already been in clinical trials or proposed as potential drug molecules in previous theoretical and experimental studies, approving the validity and the power of accuracy in our screening method. [ABSTRACT FROM AUTHOR]

Here, we introduce the use of ANI-ML potentials as a rescoring function in the host–guest interaction in molecular docking. Our results show that the “docking power” of ANI potentials can compete with the current scoring functions at the same level of computational cost. Benchmarking studies on CASF-2016 dataset showed that ANI is ranked in the top 5 scoring functions among the other 34 tested. In particular, the ANI predicted interaction energies when used in conjunction with GOLD-PLP scoring function can boost the top ranked solution to be the closest to the x-ray structure. Rapid and accurate calculation of interaction energies between ligand and protein also enables screening of millions of drug candidates/docking poses. Using a unique protocol in which docking by GOLD-PLP, rescoring by ANI-ML potentials and extensive MD simulations along with end state free energy methods are combined, we have screened FDA approved drugs against the SARS-CoV-2 main protease (Mpro). The top six drug molecules suggested by the consensus of these free energy methods have already been in clinical trials or proposed as potential drug molecules in previous theoretical and experimental studies, approving the validity and the power of accuracy in our screening method. [ABSTRACT FROM AUTHOR]

A molecular model of the interaction between alkaline NaCl solution (Sol) and carbon-supported silver/graphene oxide (Ag/GO/C) composite electrode during oxygen reduction reaction was designed and constructed, and the Molecular dynamics (MD) simulation of the model was carried out. Based on the calculation and analysis of interaction energy (ΔE), diffusion coefficient (D) and radial distribution function (RDF), depending on the type and number of oxygen-containing functional groups of GO, the interaction law between alkaline solution and Ag/GO/C composite electrode was found out, and the interaction mechanism was revealed. The results showed that the interaction force between Sol and Ag/GO/C composite electrodes with 4 different GO structures (GO1, GO2, GO3 and GO4) is mutual attraction at 353 K. The interaction energy between the Sol and the Ag/GO2/C electrode is the highest in numerical terms, and the diffusion capacity of Na+ and Cl– in the Sol is the weakest in the electrode system, indicating that the interaction between the Sol and the Ag/GO2/C electrode prevents the diffusion of solution molecules or ions on the surface of the electrode. The results of RDF showed that O2, Na+ and Cl– in solution within 3.5 Å have no obvious bonding effect with the electrode, while Sol has obvious bonding effect. When the interaction distance is 5–8 Å, O2, Na+, Cl–, Sol in the system and Ag atoms in different composite electrodes all have obvious non-bond interaction, indicating that Sol and the electrode are prone to bond interaction in the short-range region and non-bond interaction in the remote region, while O2, Na+, Cl–, and the electrode are only prone to non-bond interaction in the remote region. In other words, Ag/GO/C composite electrode has bonding and non-bonding effects in the formation of ORR system in alkaline NaCl solution, and it is mainly provided by non-bonding effects. When the number of –O–, –OH, –COOH in GO is 5 : 5 : 2 (GO2), that is, Ag/GO2/C composite electrode is most prone to ORR. This further proved that adding GO to the composite electrode can improve the catalytic performance of the electrode. These results are helpful to provide theoretical support for the research and development of electrodes in electrolytic chlor-alkali industry. [ABSTRACT FROM AUTHOR]

Alkylated fluorene-based conjugated porous polymers (CPPs) were developed for electrochemical detection of nitroaromatics (NAs). Poly[(1, 3, 5-tris(9,9-dihexyl-9H-fluorene-2,7-diyl) benzene)] [PPHF] and poly[(1,3,5-tris(5-(9,9-dihexyl-9H-fluorene) thiophene-2-yl)benzene)] [PPTHF], two CPPs with modified morphologies, showed improved porosity and charge transfer to NAs. PPTHF, featuring a thiophene moiety, exhibited superior sensing capabilities for 1,2-dinitrobenzene (1,2-DNB). Computational analysis confirmed strong bindings. This work introduces a novel approach for real-time safety monitoring and effective electrochemical sensing of NAs. [ABSTRACT FROM AUTHOR]

In comparison with conventional macro-systems, two-dimensional sheet-like materials such as aluminum carbide (C3Al) are considered as promising drug delivery systems (DDSs) because of their bioavailability and high adsorption. The surface of two-dimensional materials, which is capable of binding to the molecules of drugs with moderate binding energies, can further improve this adsorption and bioavailability. Hence, the possibility of using C3Al for the delivery of fluorouracil (5FU) is investigated for the first time within this research study. According to the adsorption energy analysis, there is a binding between the molecules of 5FU and C3Al with a moderate interaction energy, which is one of the requirements for a promising DDS. The adsorption energy of 5FU drug on the C3Al monolayer in different complexes is in the range of − 15.67 to − 26.79 kcal/mol, and there is a rise in the dipole moment (DM) of the surface after 5FU is adsorbed. This rise in the DM following the formation of the complex is conducive to improving solubility that is considered a prerequisite in biological systems for drug delivery. There is a reduction in the energy of the highest-occupied molecular orbital (HOMO) of the diene overlaps with the lowest-unoccupied molecular orbital (LUMO) gap of C3Al from 3.45 eV to 2.80 eV following the adsorption of 5FU. According to the results, C3Al seems to be a promising candidate for the delivery of 5FU. The current works provides useful insights into the experimental formulation of DDSs for 5FU based on C3Al. [ABSTRACT FROM AUTHOR]

The new compound 4-hydroxy-1-[(4-nitrophenyl)sulfonyl]pyrrolidine-2-carboxyllic acid was obtained by the reaction of 4-hydroxyproline with 4-nitrobenzenesulfonyl chloride. The compound was characterized using single crystal X-ray diffraction studies. Spectroscopic methods including NMR, FTIR, ES-MS, and UV were employed for further structural analysis of the synthesized compound. The title compound was found to have crystallized in an orthorhombic crystal system with space group P212121. The S1-N1 bond length of 1.628 (2) Å was a strong indication of the formation of the title compound. The absence of characteristic downfield 1H NMR peak of pyrrolidine ring and the presence of S–N stretching vibration at 857.82 cm−1 on the FTIR are strong indications for the formation of the sulfonamide. The experimental study was complemented with computations at the B3LYP/6-311G + + (d,p) level of theory to gain more understanding of interactions in the compound at the molecular level. Noncovalent interaction, Hirsfeld surface analysis and interaction energy calculations were employed in the analysis of the supramolecular architecture of the compound. Predicted ADMET parameters, awarded suitable bioavailability credentials, while the molecular docking study indicated that the compound enchants promising inhibition prospects against dihydropteroate synthase, DNA topoisomerase, and SARS-CoV-2 spike. Herein we present the solid state structure, noncovalent interaction and spectroscopic analysis of a prospective bioactive compound 4-hydroxy-1-[(4-nitrophenyl)sulphonyl]pyrrolidine-2-carboxyllic acid. [ABSTRACT FROM AUTHOR]

In nanobiotechnology, organic molecule-containing two-dimensional nano-structured materials are considered crucial for developing horizontal bio-inorganic nano-devices for pharmaceutical applications. We present a complete review of the application of silicon carbide monolayer (SiCML) for smart drug delivery of hydroxyurea (HU) through density functional theory computations. Also, interacting host-guest complexes with different approaching orientations, the charge transport, and the interaction strength were scrutinized. It was found that the application of HU together with SiCML was significantly effective for bio-functionalization with −35.86 kcal/mol interaction energy. The charge transfer from HU to the SiCML was confirmed by Hirshfeld method. The findings of the current study provide useful insights into research on the application of functionalized nano-biomaterials for drug delivery, nano-medicine, and other related fields. [ABSTRACT FROM AUTHOR]

New hydrazone derivate, (1Z,2E)-2-(2-(1-(1,3-dimethyl-2,4,6-trioxotetrahydropyrimidin-5(2H)-ylidene)ethyl)hydrazineylidene)-2-(p-tolyl)acetaldehyde oxime (H2L) was synthesized by 5-acetyl-1,3-dimethyl-barbituric acid and p-methyl isonitrosophenylhydrazine. Its molecular and crystal structures were determined by single crystal X-ray analysis. It belongs to triclinic system P-1 space group with a = 7.1722 (3) Å, b = 10.5362 (4) Å, c = 11.7675 (5) Å, α = 98.844 (4)°, β = 98.882 (4)°, γ = 104.330 (4)°, Z = 2 and V = 833.95 (6) Å3. In the molecular structure, the intramolecular N–H···O and N–H···N hydrogen bonds enclose S(6) ring motifs. In the crystal structure, the intermolecular C–H···O and O–H···O hydrogen bonds link the molecules into centrosymmetric dimers, enclosing R22(10) and R44(10) ring motifs, in which they may be effective in stabilization of the structure. The Hirshfeld surface analysis of crystal structure indicates that the most important contributions for crystal packing are from H...H (48.5%), H...O/O...H (23.7%) and H...C/C...H (9.7%) interactions. Hydrogen bonding and van der Waals interactions are the dominant interactions in crystal packing. Computational chemistry indicates that in the crystal, O–H···O and C–H···O hydrogen bond energies are 95.9 and 87.5 kJ mol−1. The evaluation of the electrostatic, dispersion and total energy frameworks indicates that stabilization is dominated via the nearly equal strengths of the electrostatic and dispersion energy contributions. [ABSTRACT FROM AUTHOR]

In our present work, we applied Machine Learning approaches to predict potential energy profiles for rare gas dimers as well as for the H 2 molecule. We designed an Artificial Neural Network (ANN) model with one and two layers, with two to eight neurons in each layer, to predict potential energy values. We compared the ANN predicted energy values with the ab initio data and we found an excellent agreement between the actual and predicted values. The root mean squared deviation (RMSD) values for the test data are found to be 0.10, 0.22, 0.03 and 0.47 cm - 1 for He 2 , Ne 2 , Kr 2 and Ar 2 , respectively. Further, we observed that the ANN method is able to fit the potential energy profile for weak van der Waals dimers as well as covalently bound molecules. Application of machine learning approaches to predict the interaction energies for rare gas dimers is tested in this study. Our results show that Artifical Neural Network modeling is able to predict the energies for these van der Waals interactions. [ABSTRACT FROM AUTHOR]

Fish swim bladders used to be considered as byproducts or waste in fishery; however, they are potential materials for biological medicine with abundant collagen. In this work, an efficient noncytotoxic decellularization process using sodium dodecyl sulfate (SDS) ternary system assisted with supercritical carbon dioxide (scCO2) as the green extraction fluid and ethanol (ET) as the cosolvent has been developed to harvest acellular fish swim bladders (AFSBs). The experimental results show that the tissue treated by SDS assisted with scCO2 and ethanol at 37 °C and 25 MPa can be decellularized thoroughly and maintains intact fibers and uniform pore distribution, which resulting in a tensile strength of 5.61 MPa and satisfactory biocompatibility. Meanwhile, the residual SDS content in scCO2/SDS/ET ternary system is 0.0122% which is significantly lower than it in scCO2/SDS system due to the enhanced mass transfer rate of SDS in tissues by scCO2 with ethanol. The synergy between SDS and ethanol can enhance the diffusion coefficient and the solubility of SDS in scCO2, which reduced the contact time between SDS and tissues. Meaningfully, the results obtained in this work can not only provide a novel strategy to produce acellular matrix with superior properties, but also offer a further understanding of the decellularization through scCO2 extraction processing with the synergy of suitable detergent/cosolvent. [ABSTRACT FROM AUTHOR]

Methods: The intermolecular interactions between the heavy-atom analogues of acetylene T2H2 (T = Si, Ge, Sn, Pb) and HCN have been investigated by theoretical calculations at the CCSD(T)/aug-cc-pVTZ//MP2/aug-cc-pVDZ level. Results: The global energy minimum of T2H2 is the butterfly structure A, and another energy minimum is the planar structure B. Both structures A and B exhibit the dual behavior when binding with HCN. The various hydrogen bond (HB), dihydrogen bond (DB) and tetrel bond (TB) complexes can be found according to the MEP maps of T2H2. One TB and three HB complexes formed between structure A and HCN can be located for Si2H2 and Ge2H2. One TB, two HB and one DB complexes formed between structure A and HCN can be located for Sn2H2 and Pb2H2. Four TB and one HB complexes formed between structure B and HCN can be located for all the T2H2. The geometries and binding strengths of the complexes are compared and analyzed. Conclusions: The interactions in these complexes are generally weak, and the interaction energies of these complexes range from −0.53 to −8.23 kcal/mol. The interaction energies of the TB complexes are larger than those of the corresponding HB and DB complexes for structure A···HCN systems. The relative binding strength of the four TB complexes exhibits different order for different structure B···HCN systems, which is consistent with the MEP maps of the isolated monomers. [ABSTRACT FROM AUTHOR]

The dipole–dipole interaction model is further developed to predict the stacking interaction between the protonated arginine residue and other representative neutral organic molecules, where the charge-permanent dipole and charge-induced dipole interaction is introduced into the electrostatic term of the intermolecular interaction energy. The root-mean-square error of our obtained potential energy curves and those at the level of SCS-MI-CCSD/CBS is as low as 0.40 kcal/mol. Overall, our model could accurately depict the noncovalent interaction between the protonated Arginine residue and neutral molecules, and it will serve as a powerful tool for our further exploration in biomolecular simulation. [ABSTRACT FROM AUTHOR]

We report on the results of mathematical simulation of molecular-dynamics processes in 2D and 3D crystalline structures using the Lennard–Jones potential in the MatLab software package. In the theoretical part, differential equations for simulation, their initial and boundary conditions, as well as the difference approximation are described. As the method of simulation, we have chosen the principle of molecular-dynamics simulation using one of pair potentials. In the part devoted to applications, we have simulated the chaotic motion (displacement) of atoms in 2D and 3D crystal lattices. The distribution over the calculation cell and the emergence of atoms beyond its limits are demonstrated. The relation between the binding energies in real metals and in the calculation model is determined. The interaction potential is calculated and turned out to be positive. The amplitude, phase, and frequency characteristics that have passed through the stability test have been obtained. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations are used to investigate the aggregation of the cross-contacted and non-cross-contacted graphene sheets in n-hexane, 2,3-dimethylbutane, and cyclohexane solvents. The results show that the main driving force of the graphene aggregation is the interaction between the graphene sheets, and the interaction between solvent molecules also contributes to the aggregation slightly. The initial graphene configurations and the solvent molecule structures both have effects on the graphene aggregation speed. Specifically, the cross-contacted graphene sheets aggregate faster than the non-cross-contacted configuration, since the interaction between the graphene sheets is larger and the direction of this interaction is conducive to pushing away the solvent molecules adsorbed on the graphene surface. The graphene aggregation speed is larger in n-hexane mainly since the mobility of the solvent molecules is higher than the other two solvents, while the interaction between graphenes/solvents has little influence for the systems used in this work. This work provides useful insights into the graphene aggregation in the solvents with different initial graphene configurations and solvent molecule structures. [ABSTRACT FROM AUTHOR]

Graphyne (GYN) has received immense attention in gas adsorption applications due to its large surface area. The adsorption of toxic ammonia and nitrogen halides gaseous molecules on graphyne has been theoretically studied at ωB97XD/6–31 + G(d, p) level of DFT. The counterpoise corrected interaction energies of NH3, NF3, NCl3, and NBr3 molecules with GYN are − 4.73, − 2.27, − 5.22, and − 7.19 kcal mol−1, respectively. Symmetry-adapted perturbation theory (SAPT0) and noncovalent interaction index (NCI) reveal that the noncovalent interaction between analytes and GYN is dominated by dispersion forces. The significant change in electronic behavior, i.e., energies of HOMO and LUMO orbitals and NBO charge transfer correspond to the pronounced sensitivity of GYN towards considered analytes, especially NBr3. Finally, TD-DFT calculation reveals a decrease in electronic transition energies and shifting of adsorption to a longer wavelength. The recovery time for NX3@GYN is observed in nanoseconds, which is many orders of magnitude smaller than the reported systems. The recovery time is further decreased with increasing temperature, indicating that the GYN benefits from a short recovery time as a chemical sensor. [ABSTRACT FROM AUTHOR]

In this work, pure and supersalt-doped graphene is evaluated by the density functional theory (DFT) to explore its optical and electronic properties. The doping of supersalt Al(BH4)3 on graphene reduces the highest occupied molecular orbital and lower unoccupied molecular orbital (HOMO–LUMO) bandgap of graphene@Al(BH4)3 and graphene@2Al(BH4)3 to 3.57 and 3.55 eV from 3.61 eV. The improvement in the optoelectronic properties of the supersalt Al(BH4)3-doped graphene is determined by the upshift of UV absorption peak and dipole moment. Polarizability (α) values of graphene@Al(BH4)3, and graphene@2Al(BH4)3 increase to 14% and 26% in the comparison of pure graphene. The first hyperpolarizability (βo) is increased from 0.44 (graphene) to 1295.4 au in graphene@2Al(BH4)3. Our findings suggest that Al(BH4)3-doped graphene could be an effective method for making graphene an efficient nonlinear optical material. [ABSTRACT FROM AUTHOR]

Based on the anodizing process of aluminum alloy with sulfuric acid (H2SO4) solution as electrolyte and reduced graphene oxide (rGO) as electrode material, the molecular structure model of the interaction between them was designed and constructed, and molecular dynamics (MD) simulation was performed. When the number of sulfuric acid and water molecules remained unchanged, by changing the structure ratio of oxygen-containing groups including the hydroxy (–OH), epoxy (–O–) and carboxyl (–COOH) groups of rGO, the influence of rGO structure on the interaction between them was discussed, and the nature of the interaction was revealed, which provides theoretical support for the research and development of cathode materials in aluminum anodic oxidation process. The calculation results showed that the interaction energies are all positive in the 7 rGO structures with different ratios of oxygen-containing groups, indicating that the interactions between particles are mutually repulsive. With the increase of the number of –OH, the interaction energy between rGO and H2SO4 basically decreases, and the diffusion coefficient of H2SO4 on the surface of rGO is generally similar to the change rule of the interaction energy. When the ratio of –OH, –O–, ‒COOH of rGO structure is 2 : 8 : 2, both the interaction energy and diffusion coefficient reach the maximum. From the analysis of the radial distribution functions, it can be seen that the O atoms of /H+ particles and the rGO surface tend to form bonding and non-bonding in the short and long range regions, respectively. The H and O atoms of water as well as the water molecules can not easily form chemical bonding with rGO sheet, while can form non-bonding, however, the non-bonding is not strong. And the formation of model system is mainly provided by the non-bond interaction. The order of bonding strength and the change of interaction energy with different rGO structures are basically the same. [ABSTRACT FROM AUTHOR]

Four acridinium/acridine derivatives have been prepared by mechanochemical synthesis and their crystal structure, supramolecular framework, interaction energy calculation, thermal analysis, and photophysical properties are studied and presented in this manuscript. In the crystal structure, the one- and two-dimensional supramolecular framework is constructed via various strong and weak intermolecular interactions such as N‒H…Cl, O‒H…N, O‒H…Cl, C‒H…Cl, C‒H…O, C‒H…π, and π…π, respectively. The contribution of intermolecular interaction in the three-dimensional molecular packing is studied by the Hirshfeld surface analysis. The calculated total energy value of intermolecular interaction/contacts observed between the molecular pairs in the acridine compound is stronger than the energy value of intermolecular interaction/contacts of acridinium derivatives. The energy value of π…π contacts exhibited between the molecular pairs is significantly stronger than other weak interactions. The thermogravimetric analysis reveals that the acridinium derivatives degrade in three steps whereas the acridine compound undergoes a single-step degradation. Studies show that the acridinium derivatives exhibit a better photoluminescence quantum yield when compared to the acridine compound, and the acridine compound experiences a photoluminescence quenching due to charge transfer interactions. [ABSTRACT FROM AUTHOR]

We proposed a quantum chemical calculation to investigate the nature of the adsorption of 5-Fluorouracil (5FU) on the zinc oxide (ZnO) nanocage. For this purpose, different geometries of this drug were considered to be adsorbed over the nanocage. The interaction energy is found to be quite favorable when 5FU is adsorbed with its -C = O-component onto the ZnO nanocage, compared to the other sides of the drug. The binding sites for all cases were found to belong to the nanocage in the zinc site. The charge evaluations focusing on the study of the NBO suggested that the charge transfer could be from the 5FU to the ZnO surface. The formation of physical adsorption in the interacting atoms can be further characterized in the interface regions by the density of state diagrams. Based on molecular orbitals, the HOMO is mostly situated on the adsorbed molecules of 5FU, while the electron densities in the LUMOs in the most stable configurations were mainly located on the surface of the nanocage. In another word, the charge transfer has occurred from 5FU to ZnO nanocage. The sensor mechanism is dependent upon the difference between the electronic levels. It also corresponds to the changes in the electrical conductivity. The sensor response was predicted to be approximately 1185 for 5FU detected with the ZnO nanocage, which was in complete agreement with the experimental results. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) calculations were used to investigate the adsorption of the NO molecule onto metallic Ni4M clusters (M = Ni, Mo, Sc, and Y). The goal of this study is to see if these clusters can activate NO molecules. The DFT computations are carried out using the B3PW91 functional and the LANL2DZ basis set for metal atoms, and the 6–311 + G* basis set for N and O atoms. According to molecular dynamic simulations, all of the Ni4M nanoclusters are stable at T = 300 K. Unlike Ni4Mo, the incorporation of Sc and Y impurities into Ni5 cluster is a thermodynamically favorable process. The results show that NO adsorption via its nitrogen is more energetically preferable to that via its oxygen atom. Furthermore, the adsorption of NO molecule on the Ni4Mo cluster is stronger than that on other clusters. In all of the complexes examined, NO binding causes a substantial redshift in the N‒O harmonic stretching frequency. Natural bond orbital analysis indicates that NO binding is followed by a significant charge transfer from the cluster to the NO molecule, which accounts for N‒O bond lengthening and redshifting. The nature of the interaction between the NO molecule and the Ni4M clusters is investigated, and it is concluded that the interaction is more than just charge transfer, with significant contributions from inductive and electrostatic interactions. [ABSTRACT FROM AUTHOR]

The properties of polyvinyl chloride (PVC) compositions plasticized with dibutyl and di-(2-ethylhexyl)esters of phthalic and 4-nitrophthalic acids were investigated. The result of physical and mechanical tests and dynamic mechanical analysis of samples of polymer compositions demonstrated that an introduction of a nitro group and an increase in the polarity of the plasticizer leads to a decrease in its volatility from polymer films, an increase in the strength and elasticity of the samples. Quantum-chemical calculations of systems simulating polymer-plasticizer solvation interactions revealed the possibility of enhancing intermolecular interactions with the participation of nitrophthalates. It is noted that the method of PVC film formation (from solutions or from melts) affects their properties. [ABSTRACT FROM AUTHOR]

In this research, the effect of ZnMoO4 nanoparticles (ZM NPs: A) and multi-wall carbon nanotubes (MWCNT: B) on the tensile strength of the epoxy/polyurethane (EP) matrix was investigated using the response surface methodology (RSM). This model was examined through an experimental procedure, and the results illustrated that the RSM was an appropriate tool for optimizing ε, σy, and σu. In addition, due to the importance of the interaction energy (Eint.) for understanding chemical reactions, the Eint. of the SWCNT-COOH, ZM NPs and SWCNT-COOH/ZM particles with the EP/PU polymers was assessed using the molecular dynamic (MD) simulation. The results revealed that the Eint., values for the EP/PU/ZM, EP/PU/SWCNT-COOH, EP/PU/ZM/SWCNT-COOH nanocomposites were −31.08, −18.18, and −50.33 eV, respectively. Therefore, the Eint. values between EP/PU and ZM/SWCNT-COOH was obviously higher than that of the EP/PU/CNT and EP/PU/ZM specimens. [ABSTRACT FROM AUTHOR]

The object of the present study are BODIPY molecules obtained previously by Piskorz et al. (Dyes Pigm. 178:108322, 2020) for their antimicrobial activity. Structural analysis of the BODIPY dimers is presented in context of the aggregation influence on the photophysical properties. The thorough investigation of the nature of intermolecular interaction in the representative BODIPY dimers is provided together with the decomposition of the interaction energy into the components of well-defined origin according to SAPT procedure. For the model BODIPY systems the careful examination of the interaction nature for the dimer structure based on experimental crystal study as well as fully optimized is given. The tendencies observed in the model dimers are further on investigated for two pairs of BODIPY systems designed for biomedical application. The analyzed molecules are shown to maximize the mutual interaction by the optimization of the stacking dispersion contacts between the aromatic rings of the molecules, therefore producing stable dimers. The estimation of SAPT0 interaction energy components confirms the dominating dispersion character arising from mutual BODIPY core contacts. The influence of the dimerization process on the photophysical properties of the systems studied theoretically depends to the high extend on the dimerization mode and is significant for parallel and antiparallel dispersion-governed dimers. [ABSTRACT FROM AUTHOR]

The compatibility between asphalt and nanosilica (nano-SiO2) is critical to determine the performance of nano-SiO2–modified asphalt. However, a comprehensive understanding of the compatibility behavior and mechanism of asphalt components and nano-SiO2 in the modified asphalt is still limited. In this study, the compatibility was revealed through molecular dynamics (MD) simulation. Virgin asphalt, nano-SiO2–modified asphalt, and oxidation aged asphalt models produced with the COMPASS force field; meanwhile, the proposed models were validated by comparisons with reference data. The compatibility of asphalt and nano-SiO2 was analyzed by solubility and the Flory–Huggins parameters and interaction energy. Results show that the solubility parameters decreased with the increase of system temperature while increased with the asphalt's oxidation level increase. Meanwhile, the compatibility of the asphaltene, resin, and aromatic components in asphalt is better than the compatibility with saturates, which may be due to saturates being volatile; however, the compatibility of the nano-SiO2 and saturates is much better than those with asphaltene, resin, and aromatic components. The incorporation of nano-SiO2 alleviates the volatilization of saturates. The present results provide insights into the understanding of the compatibility behavior and mechanism of nano-SiO2 and asphalt components. [ABSTRACT FROM AUTHOR]

With its unique two-dimensional structure and many outstanding features, reduced graphene oxide (rGO) can be used as an ideal electrode material. However, the mechanism of its interaction with the electrolyte solution is still unclear. The molecular model of the interaction between nitrobenzene (PhNO2) and rGO loaded iron (Fe/rGO) in ionic liquid 1-butyl-3-methylimidazole hexafluorophosphate ([BMiM][PF6]) was designed and constructed by using Materials Studio (MS) software, and the molecular dynamics (MD) simulation was performed. This paper discusses the influence of rGO with different oxygen–containing functional groups (–OH, –O–, –COOH) on the interaction, reveals the nature of the interaction, and provides a theoretical basis for the reaction process of reduction of nitrobenzene catalyzed by rGO. The results show that in [BMiM][PF6], the interaction energy between PhNO2–Fe/rGO is negative, indicating that the interaction is mainly characterized by mutual attraction. Among the 7 rGO systems, rGO2 showed the strongest interaction attraction and rGO5 the weakest. The diffusion coefficient of nitrobenzene in rGO5 system is the largest, rGO2 is the smallest. From the analysis of the radial distribution function (RDF), it can be seen that within 3.5 Å, nitrobenzene molecules are prone to bond with Fe atoms on rGO5, while nonbonding outside 3.5 Å is relatively weak. This indicates that Fe/rGO catalyzed PhNO2 system has bonding and nonbonding, and mainly bonding. Around 3.5 Å, the order of RDF peak values is consistent with the diffusion coefficient and opposite of the interaction energy. This indicates that the weaker the interaction between PhNO2 and Fe atoms on rGO, the smaller the binding of nitrobenzene molecules and the easier the diffusion. [ABSTRACT FROM AUTHOR]

In this paper we consider some physical phenomena in the vicinity of a conducting plate in a non-minimal Lorentz-violating scenario in 3 + 1 dimensions. We consider a model where the dynamics of the abelian gauge field is given by the standard Maxwell Lagrangian added by a Lorentz symmetry breaking term with the presence of higher order derivatives in the gauge field. The Lorentz symmetry breaking is due to the presence of a single background vector dλ and we perform the calculations perturbatively up to first order in dλ. We obtain the propagator for the gauge field in the presence of a mirror and the interaction force between the mirror and a point-like electric charge, as well as the interaction force between the mirror and an electric dipole. We show that, on the contrary to what happens in a minimal Lorentz-violating scenario with one single background field (L.H.C. Borges, F.A. Barone, Eur. Phys. J. C 693, 77, 2017), the image method is not valid in the model that we consider in this paper. As a consequence, the symmetry of spatial reflection on the mirror is broken. We also investigate the emergence of a torque in a system composed by a mirror and a point-like electric charge, placed at a fixed distance apart each other. The results obtained in this work have no counterpart in the Maxwell electrodynamics and were not verified in any Lorentz-violating scenario previously. [ABSTRACT FROM AUTHOR]

The interaction energy of the ozone molecule with atoms of noble gases (Ar and He) is analyzed. The coupled cluster methods CCSD(T) and CCSD(T)-F12 with orbital basis sets including electrons from diffuse orbitals (aug-cc-pVXZ for X = D, T, Q, 5, ... CBS) have been used. The geometrical configurations corresponding to the structures with global minima are established. The full three-dimensional grids of the interaction potentials with more than 4800(5300) points have been fitted for the O3–Ar(He) complexes with root-mean-square values of 0.421(0.567) cm–1. The interaction energy was additionally calculated for the O3–He complex with one internal coordinate r1 of ozone stretched to Δr1 = 0.2 and 0.4a0. [ABSTRACT FROM AUTHOR]

The structure, energetics and vibrational spectra of xylofuranose–(H2O)n where n = 2 to 10 cluster have been investigated by using Moller–Plesset second-order perturbation theory (MP) with aug-cc-pvdz as a basis set. Complete basis set limit for the xylofuranose–water clusters were calculate at MP2 level of theory. The incoming water molecule prefers the water–water interaction over the xylose–water interaction. The structural analysis shows that the average water–water distances are observed to be of similar. The calculated O–H stretching frequency is seen to blue shift in all except di-, penta- and hepta-hydrated clusters. In these clusters, the O–H frequency red shifts from isolated xylofuranose molecule. Because the OH group in these clusters is taking part either in intermolecular hydrogen bonding with water molecule or in intramolecular H-bonding with other OH groups present in xylose ring. [ABSTRACT FROM AUTHOR]

Three phenyl dimer compounds, namely 3,3′-Diformyldiphenoxyethane (C16H14O4) (1), 1-(4-[2-(4-Acetyl-phenoxy)-ethoxy]-phenyl)-ethanone (C17H16N2O3) (2), 1-{4-[2-(4-Acetyl-phenoxymethyl)-benzyloxy]-phenyl}-ethanone (C24H22O4) (3), were obtained and fully characterized, including their crystal structure determinations. The structural properties of two compounds 4, 4′-(ethylenedioxy)dibenzaldehyde) (C16H14O4) (Tewari et al. Acta Cryst. E63:o1930, 2007) [1] (4) and 4-(2-Phenoxy-ethoxy)-benzaldehyde (C15H14O3) (Valgera et al. CCDC 710835, 2016) [2] (5) are discussed with the role of the substituent in crystal packing. In vivo, anti-inflammatory activities of all compounds were studied on Wistar strain albino rats. All the compounds exhibited anti-inflammatory activity except 5. Compounds 1, 2, 4 have shown moderate-to-intermediate effects on inhibitory properties. Compound (3) with restricted rotation in the compound-like SC-558 drug was shown to possess good inhibitory properties at 180 min. In silico analysis was performed and compared with experimental in vivo results. [ABSTRACT FROM AUTHOR]

We report thermodynamic, geometric, and electronic parameters for the interaction between neutral ligands and the [Hg(H2O)]2+ dication, using the B3LYP/6–311 + G(d,p) approach. Gibbs free energies for the interaction were employed to rank the affinity order of the several neutral ligands. To identify the parameters that characterize the affinity between the two fragments, the metal-ligand interaction was analyzed according to the EDA, NBO, and QTAIM decomposition schemes. The phosphine oxide showed the highest affinity for the Hg(H2O)2+ dication, mainly due to the P=O bond polarization. Ligands containing the sulfur atom, characterized by a high covalent component for the metal-ligand interaction, are the following in the interaction order. According to the Gibbs free energy for substitution of one water molecule in the [Hg(H2O)2]2+ complex, the sequence for the affinity order is: phosphine oxide > thioketone > thioesther > lactam > amide > amine > carboxylic acid > thiophene > ketone > esther > thiol > thiocyanate > ammonia > disulfide > aldehyde > ether > haloydrin > alcohol > enol > azide. [ABSTRACT FROM AUTHOR]

In this investigation, a systematic understanding of the nature of molecular interactions between aprotic heterocyclic anions (AHAs) and typically phosphonium-based cation named as [Pnnnm]+ (n = 6, and m = 14), has been carried out using density functional theory (DFT) method and Gaussian 09 program at B3LYP/6-311G** basis sets. Multiple stable conformers were determined between the heterocyclic N atoms of the AHA anions that geometrically positioned around the [P66614]+ (C-H(α) bond) so as to formation of maximum non-covalent interactions. According to the Mulliken charge distributions on atoms in gas phase, the computational results show that the [P66614]+[3-Triaz]− ion pair possess of −394.6 kJ mol−1 as highest negative interaction energy, with six hydrogen bonds between N and H atoms of [3-Triaz]− and [P66614]+, respectively. According to the solvent effect results, the charge distributions and interaction energy is more affected by solvent than geometrical conformations. Also, for addition of CO2 molecules to multiple [P66614]+[AHA]−, our investigations indicated that, chemical interacts of one CO2 to the isolated AHA anions clearly resulted in the formation of a covalently bound carbamate with the high strength of binding, while the addition of two or more CO2 molecules leads to non-covalent bond due to the steric effect. Our results reveals the [Inda]− position rather than cation is so that five fairly strong interactions create between ion pairs in "[P66614]+[Inda]- –CO2" conformer and leads to the formation most stable conformer with highest negative interaction energy. Moreover, to the best of our knowledge, this is the first theoretical report to deeply explore the molecular interactions in the [P66614]+[AHA]− ion pairs, as well as interaction strength with the CO2 molecules. [ABSTRACT FROM AUTHOR]

State-of-the-art benchmark lattice energies of 1D hydrogen fluoride model crystal are presented. Many-body expanded coupled-cluster CCSD(T) extrapolated to the complete basis set, and thermodynamic limit results in - 7.5 ± 0.1 kcal/mol per molecule. One-determinant fixed-node diffusion Monte Carlo ( - 7.5 ± 0.1 kcal/mol) explicitly confirms its ability to produce competitive results in periodic setting. [ABSTRACT FROM AUTHOR]

The substituent effects of C–H/π non-covalent interactions between the C–H bond of alkane/alkene/alkyne/alkane halide and π orbitals of aromatic compounds were studied using the theoretical calculation methods at the CCSD(T)/aug-cc-pvdz level. The natural bond orbital (NBO) analysis implies the charge transfer from the π-system to the C–H bond in the C–H/π interaction. Therefore, either electron-donating group on the π-system or the electron-withdrawing group on the C–H system could enhance the C–H/π interaction. Meanwhile, the substituent effect of the π-system is weaker than that of the C–H systems. There is a good linear correlation between the stabilization energy (energy difference between the C–H/π complex and the separated reactants) and the reaction enthalpy (for the formation of the C–H/π complex) of the alkane/alkene/alkyne-aromatic systems. For the C–H/π interactions between two aromatic systems, good linear correlations were observed between the σp (C–H/π bond pair substituent constant) and the stabilization energy or the r(CH...η), i.e., the distance from H atom to the center of benzene ring. [ABSTRACT FROM AUTHOR]

Using DFT treatment based on the B3LYP hybrid functional, the nearly spherical structure of [Ti7O28H26]2−, the rod-like structures of [Ti2O10H10]2−, and [Ti7O30H10]2− chains in singlet ground spin states and the structures of their neutral complexes with Cu2+ ions coordinated at various terminal or bridging oxygen sites in doublet ground spin states are optimized in order to assess the toxicity of rutile nanoparticles of various shapes. For this purpose Cu-ligand interaction energy parameters and Cu charges in the above systems under study are evaluated. Spherical structures are more reactive than the rod-like chains of the (nearly) same size. The reverse relation holds for the degree of their toxicity as indicated by the extent of the electron density transfer to a Cu2+ probe. The experimentally observed higher cytotoxicity of the rod-like nanoparticles in comparison with the spherical ones might be explained by the higher electron density transfer to the interacting cells. [ABSTRACT FROM AUTHOR]

Self-assembling cyclic peptide nanotubes are widely investigated in many scientific fields due to many of their properties; controllable sizes, stable, and simple formation. In this research, the cyclic peptide nanotubes are modelled as the carriers to interact with a drug molecule. On employing the Lennard-Jones function and the continuous approximation, the energy value of the system can be evaluated. The main outcome of this research is a mathematical expression describing the relation of energy, radii of drug and peptide and the spacing between peptide units. We find that the drug is most stable when it is in the spacing between subunits of the peptide nanotubes. We also consider the energy behaviour of an offset drug inside three different sizes of the cyclic peptide nanotubes. We predict that the drug can be encapsulated inside the peptide nanotube when the difference of their radii is around 3 Å. [ABSTRACT FROM AUTHOR]

In title compound, 2-amino-5-chloropyridinium p-toluenesulfonate C7H7SO3−C5H5N2Cl+ (I), the anions and cations form an 22 (8) heteromeric dimer through N-H...O hydrogen bonds. 2-Amino-5-chloropyridinium cations and p-toluenesulfonate anions are interlinked through N-H...O and C-H...O hydrogen bonds to develop a two-dimensional supramolecular grid in the crystal structure parallel to the (0 0 1) plane. The formation of π...π and π...Cl interactions bridges the two-dimensional supramolecular network developing a three-dimensional packing of the crystal structure. The Hirshfeld surface analysis of the title molecule is carried out to understand various aspects of the intermolecular interaction. Interaction energies are calculated at the dispersion-corrected CE-B3LYP/6–31G(d,p) level of quantum theory for N-H...O, C-H...O, π...π interactions and the effect of interaction energies in the formation of a supramolecular network is studied. [ABSTRACT FROM AUTHOR]

The energetic and electronic structure of various water dimer isomers has been explored through DFT methodology. Six different possible water dimers come in two broad categories, planar and non-planar. In each of the categories, three distinct topologies (i) linear, (ii) ring and (iii) bifurcated, have been obtained. The linear dimer has the highest interaction energy, followed by the ring dimer and then comes the bifurcated dimer. For each of these type, a planar dimer having all six atoms organized in a single plane come very close to, but has a slightly higher energy than the corresponding non-planar counterpart. Bader's atoms in molecules (AIM) theory, reduced density gradient (RDG) method and non-covalent interaction (NCI) analysis reveal that the electron density distribution among the interacting water molecules correlates exactly in the sequence of interaction energies of different isomers of water dimer. [ABSTRACT FROM AUTHOR]

The existing methods for dewatering sewage sludge containing finely dispersed clay minerals can be applied with an initial moisture content of <75%. In the case of higher moisture content, it is necessary to treat preliminary such dispersions to provide their destabilization, sedimentation, and consolidation, that is, to obtain more concentrated precipitate, followed by the separation of the excess liquid phase. A decrease in the stability of clay disperse systems can be achieved by decreasing the electrostatic repulsion between particles with a decrease in their surface charge due to a change in the pH of the dispersed medium or adsorption of potential-determining cations, as well as due to the compression of the double electric layer with an increase in the total concentration of electrolyte. We studied the effect of the chemical composition of an aqueous dispersed medium on the ζ potential, the interaction and aggregation of dispersed particles in a model system based on kaolinite, sedimentation of aggregates, and consolidation of the sediment. The dependence of the obtained values of the ζ potential on the inhomogeneity of the surface charge of the particles and the polarization of the formed chain aggregates in an electric field is analyzed. The conditions for maximum sediment consolidation are determined, which ensure a further decrease in moisture content using methods combining pressure and electroosmosis. [ABSTRACT FROM AUTHOR]

Biotin is well known to be bound with exceptional strength by the avidin class of proteins. This ability comes from a match between the biotin-binding pocket of the protein and the structural elements of biotin, including its ureido and thiolane rings. Here we investigate the solvation shell of biotin in water as revealed by classical force field molecular dynamics with GAFF force field. Snapshots from the classical molecular dynamics were then used to generate microsolvated structures. Details of hydrogen bonding patterns present in these microsolvated structures were studied by symmetry-adapted perturbation theory (SAPT). Interaction energy values for small models of biotin hydrated by 5 or 6 water molecules show that the cooperativity constitutes 15–22% of the total interaction energy and corresponds roughly to formation of one additional hydrogen bond to biotin. The SAPT analysis shows the differences underlying hydrogen bonds of similar strength (with oxygen or sulfur atoms as the hydrogen bond acceptors, and with nitrogen atom playing a dual role of the donor and acceptor). [ABSTRACT FROM AUTHOR]

This work was undertaken to understand the mode of interaction of makaluvamines, a class of marine pyrroloiminoquinone alkaloids isolated from sponges of the genus Zyzzya, used in the treatment of several human cancer cell lines. This analysis was done by the quantum chemistry method. First, we used electrostatic potential (ESP) to reveal the different sites that accept and donate hydrogen bonds (HB) of charged forms (protonated and methylated) of makaluvamines (at level B3LYP/6-311++G(d,p)). In a second step, we studied the interactions by hydrogen bond between these molecules and water molecule on the one hand (at level B3LYP/6-311++G(d,p)) and on the other hand glutamic acid a protein residue of topoisomerase II (at level B3LYP/6-31+G(d,p)). Finally, we calculated the corrected BSSE interaction energies and estimated the relative stability of the formed complexes. [ABSTRACT FROM AUTHOR]

Understanding the interaction of CH4 with kaolinite is significant for researchers in the fields of coalbed CH4 and shale gas. The diffusion behaviors of CH4 in kaolinite with water contents ranging from 0 to 5 wt% have been analyzed by molecular dynamics simulations. The results of the simulations indicate that CH4 molecules can jump between adjacent holes in the kaolinite matrix. CH4 diffusion coefficient was very low (3.28 × 10−9 m2/s) and increased linearly with the increasing of water content. As the water content decreased, the value of radial distribution function first peak between CH4 and oxygen was larger, meaning that with lower water content, the interaction energy between CH4 and oxygen in kaolinite is stronger. The interaction between CH4 and water is linearly positively correlated with water content, in contrast, the interaction energy between kaolinite and water as well as between kaolinite and CH4 decreased linearly with increasing water content. On the other hand, the diffusion of CH4 molecules adsorbed on the surfaces also can be accelerated by the fast diffusion of water molecules in the middle micropore of the kaolinite. [ABSTRACT FROM AUTHOR]

In this study, the properties of unstable and stable flocs were investigated under the steady operation of a membrane bioreactor (MBR). The extracellular polymeric substances (EPS) composition, surface charge, and hydrophobicity of unstable and stable flocs were examined and compared. Interfacial interactions of the membrane with unstable flocs, unstable flocs themselves, and unstable and stable flocs were assessed using the extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) models. Cake layer resistance was found to contribute more than 80% of total resistance under steady operating conditions. Compared with stable flocs, unstable flocs possessed a higher level of EPS, more diverse protein, more negative charge, weaker hydrophobicity, and higher fouling potential. Thermodynamic analyses showed that unstable flocs had a higher adhesive strength (− 63.4 mJ/m2) with the membrane, lower self-cohesive strength (− 18.3 mJ/m2), and higher cohesive strength (− 54.3 mJ/m2) with stable flocs. Therefore, some unstable flocs remained on the membrane surface to form the cake layer due to their poor cohesion strength. [ABSTRACT FROM AUTHOR]

It is obvious and well known that the hydrogen bond plays a crucial role in numerous physical, chemical and biochemical processes. However, the significance of other interactions is also analysed in numerous studies. They are often compared with the hydrogen bond. The halogen bond is an example of such interaction that reveals characteristics occurring also for the hydrogen bond. The other interactions which are often classified as the σ-hole bonds or π-hole bonds possess characteristics typical for the hydrogen bond. The interactions of tetrahedral pnicogen and tetrel centres with Lewis bases are analysed here. The former ones may be labelled as the charge-assisted pnicogen bonds and classified as the σ-hole bonds. The latter ones labelled as the tetrel bonds are also classified as interactions between the σ-hole and the electron-rich region. Both these interactions are compared with the hydrogen bond. In the case of the hydrogen bond, the A–H...B, A–H...π and A–H...σ types of interactions are discussed in different studies where A–H is the proton-donating bond while B, π and σ label the kind of the proton acceptor: the mono-atomic Lewis base centre B, the π-electrons and the σ-electrons, respectively. The pnicogen centre, Z, in the charge-assisted pnicogen bonds may also interact with these electron-rich regions thus the Z...B, Z...π and Z...σ pnicogen bonds are known. [ABSTRACT FROM AUTHOR]