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Human activities have been limited by coronavirus disease 2019 (COVID-19), and the normal conditions of our lifestyles have changed, particularly in terms of electricity usage. The aim of this study was to investigate the impact of COVID-19 on the power sector in the Lao PDR in 2020, as well as the challenge of using solar energy to supply power to the network using an optimal approach. The returns on investment of network extension and the purchase of solar energy were also evaluated. Furthermore, load conditions caused by the country’s lockdown policy were analyzed. We analyzed the optimal sizing and location of solar energy using a particle swarm optimization method based on the main objective functions, with the system’s power loss decreasing and its reliability improved. The results demonstrated that the suddenly reduced load from industry and commercial business did not have a large impact on its operations; however, revenue was reduced. The optimal method for connecting solar energy to a network can reduce power loss and improve system reliability. In addition, we discovered that the location and capacity of solar generation can reduce the investment costs of extensions for new lines, with the surplus power being exported.

In this study, the glass transition temperature (Tg) of polyethylene terephthalate (PET) and polyethylene vanillate (PEV) are obtained by molecular dynamics (MD) simulations using united atoms OPLS-UA model. The obtained Tg are found to be about 375K and 378K for PET and PEV polymers, respectively, which are a bit higher than those of previous experiments and computer simulation works. This imply the need of parameters optimized and validation to be fit for the specific PET and PEV systems before applied in further works of their blended systems.

This paper presents the CSP-2L continuous sampling plan, which is designed for product inspectionon two independent production lines at the same time. The purpose of the CSP-2L is to improve the CSP-1-2Lin order to reduce the number of defective products that have passed without being inspected during thetemporary inspection stop, so the quality of the products is better. Therefore, if the manufacturer who uses theCSP-2L plan to inspect the production lines then resulting in higher quality of the products than the CSP-1-2L.This presentation includes the product inspection procedures and the formulas for performance measures suchas average total fraction inspected (ATFI), average total outgoing quality (ATOQ), and average total outgoingquality limit (ATOQL) which are carried out using a Markov chain. The formulas for performance measures ofthe CSP-2L have been tested to be accurate. When defined, the probability of a unit produced by the processbeing nonconforming of line 1 and line 2 are equal (p1 = p2 = p = 0.005, 0.015 and 0.035), the clearance numberof line 1 and line 2 are equal (i1 = i2 = 10, 20, 30, 40 and 50), the sampling fraction of line 1 and line 2 are equal(f1 = f2 =12and13) and the number of units to be found when inspection of line 1 and line 2 are in the phaseof sampling inspection at the same time (m = i1 and 2i1). Moreover, the ATOQ values from the CSP-2L and theCSP-1-2L plans were compared. The results showed that, the formulas for performance measures are accurateand in the case of p, the levels are low and moderate, the ATOQ of the CSP-2L are less than those of theCSP-1-2L in all cases. But in the case of p is at a high level, the ATOQ of the CSP-2L is less than those of theCSP-1-2L for some cases of i.

A high selectivity of NO x over N2 (simulating air) is found in silico when studying the adsorption of the ternary mixture N2O4/NO2/N2 on the metal-organic framework MIL-127(Fe) by molecular simulations under consideration of the recombination reaction N2O4 ↔ 2NO2. The number of N atoms in nitrogen oxides NO x and that in N2 is used to define a selectivity of the combined adsorption and chemical recombination that can reach values of about 1000.

The separation of nitrogen dioxide (NO2) from the gas mixture with nitrogen (N2) by selective adsorption and diffusion in three Zeolitic Imidazolate Frameworks (ZIFs) is examined by Gibbs Ensemble Monte Carlo (GEMC) and Molecular Dynamics (MD) computer simulations at 373 K, which is a temperature that can be found in the exhaust gases of combustion engines and furnaces. This temperature ensures that the chemical equilibrium reaction between NO2 and N2O4 can be neglected since at this temperature almost only NO2 exists. At 373 K, the membrane selectivity of NO2 over N2 is predicted to be about 4.2 (ZIF-90), 5.2 (ZIF-8), and 10.6 (ZIF-78). In addition, it is shown that N2O4 can be neither adsorbed nor diffuses inside these ZIF materials, which makes these ZIFs a promising materials for separation by membranes. Due to molecular sieving, only N2 and NO2 can pass the ZIF membranes.

Polyethylene terephthalate (PET) is one of the most common polymers used in industries. However, its accumulation in the environment is a health risk to humans and animals. Polyethylene vanillate (PEV) is a bio-based material with topological, mechanical, and thermal properties similar to PET, allowing it to be used as a PET replacement or blending material. This study aimed to investigate some structural and dynamical properties as well as the estimated glass transition temperature (Tg) of PET/PEV blended polymers by molecular dynamics (MD) simulations with an all-atom force field model. Four blended systems of PET/PEV with different composition ratios (4/1, 3/2, 2/3, and 1/4) were investigated and compared to the parent polymers, PET and PEV. The results show that the polymers with all blended ratios have Tg values around 344–347 K, which are not significantly different from each other and are close to the Tg of PET at 345 K. Among all the ratios, the 3/2 blended polymer showed the highest number of contacting atoms and possible hydrogen bonds between the two chain types. Moreover, the radial distribution results suggested the proper interactions in this system, which indicates that this is the most suitable ratio model for further experimental studies of the PET/PEV polymer blend.

Polyethylene vanillic (PEV), a bio-based material, has mechanical and thermal properties similar to polyethylene terephthalate (PET), the most common polymer used in industries. The present study aimed to investigate and compare their structural dynamics and physical data using a computational approach. The simple model of a single-chain polymer containing 100 repeating units was performed by all-atom molecular dynamics (MD) simulations with refined OPLS–AA force field parameters. As a result, the flexibility of the PEV structure was greater than that of PET. PET and PEV polymers had the predicted glass transition temperature Tg values of approximately 345 K and 353 K, respectively. PEV showed a slightly higher Tg than PET, consistent with current experimental evidence.

The binding capability of pyrrolidinyl peptide nucleic acids (PNAs) to DNA have been studied experimentally, also the high affinity and sequence specificity were reported. However, to date a detailed understanding of these properties is unclear due to a lack of crystallographic data. In this work, molecular dynamics (MD) simulations of pyrrolidinyl PNA with different stereochemistry, (2′R,4′R)- and (2′R,4′S)-prolyl-(1S,2S)-2-aminocyclopentanecarboxylic acid (namely acpcPNA and epi-acpcPNA, respectively), binding to DNA were performed. MD simulations of three different forms (A-, B- and P-forms) were conducted to investigate the probable duplex conformation, which revealed that the MD structures were close to B-type duplex. It was found that acpcPNA and epi-acpcPNA backbones play a minor role in the hydrogen bond geometry of base pair, however, these greatly influence the interactions between PNA and DNA strands, leading to the differences in duplex stability. The calculated binding free energy revealed the higher thermodynamic stability of acpcPNA-DNA compared to epi-acpcPNA-DNA system, which is in good agreement with published experimental data. This work offers new insights into the conformational and energetic properties of pyrrolidinyl PNA-DNA duplexes at a molecular level.

There is experimental evidence from adsorption and permeation studies that methane can enter the Zeolitic Imidazolate Framework (ZIF)-90 framework despite the fact that the critical diameter of methane (3.8 A) is larger than the window size of ZIF-90 (3.5 A) assuming a rigid framework. Therefore, adsorption and diffusion of methane in the ZIF-90 were investigated by Molecular Dynamics (MD) and Gibbs Ensemble Monte Carlo. Various interaction force fields have been tested and a suitable one has been proposed. Results of structural and dynamical properties of methane in ZIF-90 are presented. Like for methane in ZIF-8, no gate opening was found in this paper for methane in ZIF-90 up to a pressure of 260 bar. Therefore, the adsorption and diffusion of methane in ZIF-90 can be explained by a flexible framework.

The effect of the partial charge distributions on the adsorption of CO2 molecules in ZIF-8 framework has been obtained using GEMC simulations. The charge models are derived from the ab initio electrostatic potential surfaces of framework fragments. The signs of the atomic charges obtained with the MK model are more consistent with respect to the basis set than those obtained from the other models. The charges on the H1 and H2 atoms are found to have a notable effect on the amount of absorbed CO2, in agreement with a previous mention that these hydrogen sites are the favored absorption sites.

In the field of nanoporous materials, guest-induced structural changes in metal–organic frameworks (MOFs) attracted great attention over the last years. One example concerns a gate-opening effect in MOF ZIF-8 which was found to occur upon sorption of N2. To mirror these structural changes in molecular simulations, suitable force fields for the proper description of framework flexibility are required. We demonstrate that our previously published force field is able to reproduce these structural changes in classical MD simulations. In particular, with our parameter set the diameter of the windows connecting adjacent cavities is found to match the X-ray values almost perfectly. We focus on investigating the impact of the structural changes on the mobility of N2 molecules in ZIF-8 framework and compare the results with those of another parameter set, which was published recently by Zhang and coworkers. The size of the windows increases notably, when the critical “gate-opening” loading is surpassed. Most surprisingly, this pronounced increase does not result in a speed-up of the N2 self-diffusivity. It appears, that a complex interplay of host-host and host-guest interactions increases the mutual hindrance of the N2 molecules and counter balance the acceleration of the mobility due to the larger window size.

Recent adsorption, diffusion and permeation studies give experimental evidence that ethane can easily adsorb and diffuse in the ZIF-8 framework. This finding is surprising since the pore window of ZIF-8 – derived from XRD data – is virtually too small for ethane migration. Therefore, the diffusion mechanism of ethane in ZIF-8 and the influence of the diffusing guest molecules on the flexible lattice are investigated in detail in this paper with focus on the diffusion limiting step, the passage of the ZIF-8 window between adjacent cavities. Contrary to zeolite research, well established interaction parameter sets are still not available for MOF simulations. Hence, a large part of this paper is devoted the comparison of several parameter sets for the molecular interactions. Also, the conservation not only of the unit box size in NPT simulations but also the conservation of the geometrical structure of the lattice (most important the “windows” between adjacent pores) has been examined. Employing a suitable parameter set, two interesting effects can be observed: (i) The window size of ZIF-8 is smaller at higher ethane loadings, while simultaneously (ii) at higher loadings the guest molecules within the cavity exert forces that press a given probe molecule toward the window. These two effects nearly compensate each other leading to a weak dependence of the self-diffusivity upon the concentration of guest molecules. However, no gate-opening mechanism by a torsional motion of the linker molecule methylimidazolate could be found in our MD simulations because of a too large activation energy for this motion.

Using quantum chemical (QC) calculations at the B3LYP/6-31G(d) level of theory, we investigate for three selected layer–pillar paddle–wheel metal–organic framework materials of composition M 2 II L 2 1 L 2 ( M II = Zn,Cu; L 1 = 2 , 3 , 5 , 6 -tetrafluorobenzene-1,4-dicarboxylate, 2,3,5,6-tetramethylbenzene-1,4-dicarboxylate; L2 = 1,4-diazabicylco[2.2.2]octane) the preferential orientations and the rotational energy barriers of both layer (L1) and pillar (L2) linkers. The calculations suggest unhindered rotational motion for pillar linker in all compounds studied (ΔEbarrier ⩽ 0.14 kcal mol−1). For layer linkers, the energy barriers for the rotation of benzene rings are found to vary significantly, indicating an hindered rotation in the case of the fluorine substituent (ΔEbarrier ≈ 14 kcal mol−1), and a static situation in the case of the methyl substituent (ΔEbarrier ≈ 75 kcal mol−1). The rotational dynamics are found not to depend on the type of metal ion. AIM analysis indicates that the rotational energy barriers are influenced by C–H⋯F hydrogen-bonding interactions between the dabco and fluorine-substituted linkers.

Initiated by separation factors of up to 15 between CH 4 and H 2 found in experiments of gas mixture permeation through a newly developed ZIF-8 membrane the diffusion of CH 4 and H 2 in ZIF-8 has been investigated by IR microscopy and molecular dynamics simulations. Several well known interaction parameter sets for simulations have been tested. It turned out that the H 2 /CH 4 -ZIF-8 system is very sensitive with respect to the choice of these parameters. The large differences in the diffusion behavior of CH 4 and H 2 are investigated by microscopic simulation tools and compared with experiments. A parameter set has been found that gives reasonable agreement with experimental IR and membrane permeation results.

The extremely slow diffusion of the molecule n -pentane caused by the hopping from cage-to-cage in zeolite ZK5 has been investigated by transition state theory (TST). Such slow diffusion cannot be accessed by usual molecular dynamics simulation techniques. The calculation of the partition function ratio needed for TST was enabled by a recently developed method, the so-called high-temperature configuration-space exploration (HTCE). Dynamical corrections for recrossing events have also been taken into account. The obtained intra-zeolite self-diffusion constant between 247 and 317 K of 10 −16 –10 −15 m 2 s −1 falls in the range of 10 −18 –10 −15 m 2 s −1 observed experimentally. The calculated energetic barrier between two neighboring cages of 29 kJ mol −1 is in good agreement with that of 28 ± 5 kJ mol −1 obtained from NMR measurement.

The permeation of methane molecules through the silicalite-1 surfaces with and without silanol groups has been studied by nonequilibrium molecular dynamics computer simulations. A newly fitted intermolecular potential between the methane molecules and the silanol is used. A control volume provides a nearly stationary gas phase close to the membrane. The nonequilibrium process of filling the (initially empty) membrane with methane molecules until saturation is considered, and the surface permeability has been evaluated. It turns out to be strongly influenced by the presence of silanol groups. Additionally it was found that for a large part of the loading process the particle stream into the zeolite membrane was nearly independent upon the deviation from equilibrium. This means that far from equilibrium the decay of this deviation does not follow an exponential law.

Configurational-Bias Monte Carlo simulations of the adsorption isotherm of ethane in Zn(tbip) (H 2 tbip = 5-tert-butyl isophthalic acid), a representative of metal-organic frameworks, show an inflection at a loading, q i = 6 molecules per unit cell. This inflection causes the inverse thermodynamic factor, 1/ Γ i , to display a minimum at q i = 6, along with a maximum at q i ≈ 10. Molecular Dynamics (MD) simulations of the self-diffusivity D i,self , taking account of the framework flexibility of Zn(tbip) show that the D i,self − q i dependence follows that of 1/ Γ i − q i , with a minimum at q i = 6. Remarkably, MD simulations assuming a rigid framework yield significantly lower values of the self-diffusivities, and show a monotonic decrease of D i,self with q i .

Optimal binding sites and its corresponding binding energies between MOF-5 clusters and small guest molecules, CH4 and CO2, were investigated using the ONIOM method with different levels of quantum chemical calculations. The clusters were validated using three different sizes of the MOF-5 clusters, SINGLE, DOUBLE and TRIPLE consisting of (Zn4O)2(COOCH3)10(COO)2C6H4, (Zn4O)3(COOCH3)14(COO)4(C6H4)2 and (Zn4O)4(COOCH3)18(COO)6(C6H4)3 units, respectively. Guest molecules were assigned to lie in the configurations parallel ( ∥ ) and perpendicular ( ⊥ ) to linker (LINK) and corner (CORN) domains of the clusters. The ONIOM(MP2/6-31G∗∗:HF/6-31G∗∗) with the corrections due to the basis set superposition errors was found to be the optimal choice for the investigation of these systems. Strong effects of cluster size were found for the CO2/MOF-5 complexes, i.e., the SINGLE cluster is sufficient to represent interactions with CH4, but the interaction with CO2 requires the TRIPLE model. The optimal binding sites of guest molecules as well as their orientations in the cavity of the MOF-5 are CORN ⊥ for both CH4 and CO2 with the corresponding binding energies of −3.64 and −9.27 kJ/mol, respectively.

The crystal structure of a novel octanuclear copper(II) complex containing the bidentate 1,10-phenanthroline ligand (abbreviated as phen) with cooperative carbonato and hydroxido bridging ligands, [Cu8(phen)12(μ3-OH)2(μ-OH)2(μ3-CO3)2](CF3SO3)8(DMF)2(H2O)0.5 (1) (when DMF = N,N-dimethylformamide) is described. Compound 1 consists of two symmetry-related di-μ-hydroxido-bis(1,10-phenanthroline)copper(II) groups which held together by long Cu–O(H) bonds, creating a Cu2(OH)2 core of a tetranuclear hydroxido-bridged copper(II) unit, further coordinated with trans-axially at Cu(3) and Cu(3)A by [μ3-carbonato-tetrakis(phen)dicopper(II)] moieties. The di-μ-hydroxidocopper(II) species play an important role for the apparent ferromagnetic interaction with the Cu–OH–Cu angles (θ) of 95.8(2)° and 93.5(1)°. The spectroscopic properties (IR, reflectance and EPR spectra) and the magnetic susceptibility data of this compound are investigated and compared with other related polynuclear copper(II) compounds.

The crystal structures of polynuclear copper(II) complexes containing the bidentate bpy ligand (bpy = 2,2′-bipyridine) with varied coordination modes of the carbonato bridging ligand, a hexanuclear compound [Cu6(bpy)10(μ-OH)2(μ-CO3)2](CF4SO3)6(DMF)2(H2O)4 (1) and a polymeric compound {[Cu3(bpy)3(μ-OH)2(μ-CO3)2](H2O)6.5}n (2) are described. Compound 1 consists of the di-μ-hydroxido-bis(2,2′-bipyridine)copper(II) groups coordinated with trans-axially at each copper atom by [μ-carbonato-bis(bpy)copper(II)] moieties, forming a hexanuclear copper(II) compound. Each copper(II) ion has a distorted square–pyramidal environment in which three Cu(II) atoms are linked through oxygen atoms of the bridged ligand by the μ3-η2:η1-CO3 coordinated mode. Compound 2 consists of two independent di-μ-hydroxido-bis(2,2′-bipyridine)copper(II) dinuclear units which are connected to the central moiety by two different coordination modes of the carbonate bridging ligands, μ-η1:η1 (anti–anti) and μ-η2:η1-CO3 configurations. Each Cu(II) ion has a distorted square–pyramidal geometry. The repeating units give rise to a one-dimensional chain along b-axis. The lattice structures are stabilized by stacking interaction between pyridine groups of bpy chelated ligands of different units. The spectroscopic properties (IR, Reflectance and EPR spectra) and the magnetic susceptibility data of both compounds are investigated.

The orientation distribution and confined rotational motion of n-pentane in the oblate ¿ cages of zeolite KFI is computed by use of MD simulation. Pentane is preferably oriented with its end-to-end vector in the x and y direction perpendicular to the C4 symmetry axis of the cage. For comparison with a previous NMR study (Zorine et al.; J. Phys. Chem. B 2004, 108, 5600), the orientational autocorrelation function (OACF) of the C1C2C3 bi-sector is obtained from the simulations between 125 and 450 K, and decomposed into three exponential components. The slowest component follows the Arrhenius law with an activation energy of 13 kJ mol-1 and corresponds well to the effective rotation correlation times obtained from NMR relaxation above 200 K. MD trajectory analysis suggests that this component reflects gauche-trans conformation changes within the cage. According to our present findings, rotation of trans-trans pentane about the cage symmetry axis, which was previously proposed as the source for NMR relaxation, is actually too fast. Based on the OACF analysis, the non-Arrhenius behavior observed in the mentioned NMR study is now explained by a simultaneous increase of the correlation time and relative amplitude of the slowest OACF component versus inverse temperature.

The binding energies and the corresponding structures of a methane molecule on the silanol covered (010) surface of silicalite-1 have been investigated using ab initio methods. Different levels of calculations, HF/6-31G(d), MP2/6-31G(d) and ONIOM (MP2/6-31G(d):HF/6-31G(d)) including the correction of an error due to an unbalance of the basis set, known as basis set super position error (BSSE), as well as the size of the cluster representing the silicalite-1 surface, were systematically examined to validate the model used. The ONIOM method with the BSSE correction was found to be a compromise between accuracy and computer time required. The optimal binding site on the silicalite-1 surface was observed at the configuration where the methane molecule points one H atom toward the O atom of the silanol group. The corresponding binding energy is -1.71 kJ/mol. This value is significantly higher than that of -5.65 kJ/mol when the methane molecule approaches the center of the straight channel. At this configuration, the C atom of methane was observed to locate exactly at the center of the channel. This leads to the conclusion that the methane molecule will relatively seldom be adsorbed on the silanol covered (010) surface of silicalite-1. Instead, the adsorption process will take place directly at the center of the straight channel.

The solvation structure of glucosamine in aqueous solution was investigated using Monte Carlo simulation at 298 K. The MCY rigid water model and ab initio glucosamine–water fitted potential were applied. The first hydration shell appears at 4.6 A from the center of glucosamine with a coordination number of seven water molecules where one water lies in the ligand’s plane while two and four of them are about 2–4 A above and below the plane, respectively. Furthermore, the mobility distribution and orientation of the water molecules around the ligand have been intensively investigated and reported.

The hydration of Fe 2+ and Fe 3+ ions in aqueous solution was studied by molecular dynamics simulation using ab initio pairwise interactions potential plus three-body correction terms. The simulations were performed at 298.16 K using the CF2 flexible water model. Radial distribution functions and their integration for Fe n + –O show that six water molecules reside in the first hydration shell for both Fe 2+ and Fe 3+ ions, with R FeO being 2.15 and 2.05 A, respectively. The second hydration shell contains about 13 and 15 water molecules for Fe 2+ and Fe 3+ ions, respectively, forming hydrogen bonds to the water molecules in the first shell. Water exchange between the second shell and bulk occurs frequently. Librational and vibrational spectra of second shell water molecules are almost identical to those in the bulk, whereas for first shell ligands remarkable differences are observed.

The hydration shell structure of Fe(II) and Fe(III) ions in their high spin state has been studied by combined ab initio quantum mechanical/molecular mechanical (QM/MM) molecular dynamics simulations, in which the ion and its first hydration sphere were treated at the Hartree−Fock ab initio quantum mechanical level, whereas ab initio generated pair plus three-body potentials were employed for the remaining system. The coordination number in the first hydration shell is 6 for both Fe(II) and Fe(III) ions. The second hydration shell contains 12.4 and 13.4 water molecules for Fe(II) and Fe(III) ions, respectively, in good agreement with the experimental values. The residence time of a water molecule in the second hydration shells of Fe(II) and Fe(III) is 24 and 48 ps, respectively. The complex configuration and ligand orientations observed in this study prove that many-body effects play an important role in the hydration of both Fe(II) and Fe(III) ions. The hydration energies computed from the simulation are...

Dynamical properties, librational and vibrational motions of water molecules in the first and second hydration shells of the Fe(II) and Fe(III) ion were evaluated by means of velocity autocorrelation functions obtained by combined quantum mechanical/molecular mechanical molecular dynamics (QM/MM-MD) simulations. The frequencies of rotation around three principal axes and the frequencies of intramolecular vibration of the water molecules in the first hydration shells obtained from the simulations are blue-shifted for both ions compared to those observed experimentally for liquid water. The intramolecular geometry of water molecules in the quantum mechanically treated region (ion plus first hydration shell) shows shorter O–H bonds and wider H–O–H angles than the bulk solvent.

In this paper, digital image analysis is applied for non-destructive identification of pure breeding Rice seed. The appearance of rice such as its shape and color is expected to be the important features in agricultural breeding and quality testing. It is a difficult task for farmer to identify rice seeds because of the similar surface color of the seeds. This paper presents an automatic classification method based on segment images and RGB color features. Hardware of image capturing is designed using scanner. The ratio between segment images and varieties of different shades RGB histogram are then calculated. The rule of classification “Khao Dawk Mali 105” between pure breeding Rice seed and impure breeding Rice seed are created. The correct classification rates for two steps are: good rice seeds 98% and pure breeding rice seeds 82%. This information could be used as a signal to farmer decided to switch to a new generation seeds.

Nonbonding parameters of AMBER force field have been refined based onab initiobinding energies of CO2–[C7H5N2]−complexes. The energy and geometry scaling factors are obtained to be 1.2 and 0.9 forεandσparameters, respectively. Molecular dynamics simulations of CO2molecules in rigid framework ZIF-11, have then been performed using original AMBER parameters (SIM I) and refined parameters (SIM II), respectively. The site-site radial distribution functions and the molecular distribution plots simulations indicate that all hydrogen atoms are favored binding site of CO2molecules. One slight but notable difference is that CO2molecules are mostly located around and closer to hydrogen atom of imidazolate ring in SIM II than those found in SIM I. The Zn-Zn and Zn-N RDFs in free flexible framework simulation (SIM III) show validity of adapting AMBER bonding parameters. Due to the limitations of computing resources and times in this study, the results of flexible framework simulation using refined nonbonding AMBER parameters (SIM IV) are not much different from those obtained in SIM II.

Andrographis paniculata has been employed as a folklore remedy. Andrographolide (Andro), 14-deoxy-11,12-didehydroandrographolide (DHA), andrographiside (AS), and neoandrographolide (Neo), are major diterpenoids isolated from this plant. In the present study, influence of the four diterpenoids on CYP1A1 mRNA expression was investigated in primary cultured mouse hepatocytes. Additionally, binding of these compounds to aryl hydrocarbon receptor (AhR) was examined using molecular docking analysis to clarify mechanism of CYP1A1 induction. Andro and DHA induced CYP1A1 expression by itself, and co-treatment with a CYP1A1 inducer (BNF, beta-naphthoflavone) showed a synergistic increase of CYP1A1 expression. Andro demonstrated higher enhancing activity than DHA at every similar concentration. On the other hand, Neo suppressed BNF-induced CYP1A1 expression, but AS did not modify the induction. Results from molecular docking analysis of BNF and four diterpenoids on ligand binding domain of AhR were consistent with levels of CYP1A1 mRNA expressions. Furthermore, difference of binding sites of BNF in the presence of diterpenoids might affect the synergism or inhibition of CYP1A1 expression. These results suggest that use of A. paniculata as a health supplement should be concerned in term of herb-drugs interactions or risk of carcinogenesis, according to its ability to influence CYP1A1 expression.

Aiming at understanding the molecular properties of the encapsulation of the anticancer drug gemcitabine in the single-walled carbon nanotube (SWCNT), molecular dynamics (MD) simulations were applied to the two scenarios; that of gemcitabine filling inside the SWCNT, and that of the drug in the free state. Inside the SWCNT, the cytosine ring of gemcitabine was found to form a π-π stacking conformation with the SWCNT surface, and this movement is not along the centerline of the tube from one end to the other of the tube where the distance from the center of gravity of the molecule to the surface is 4.7 A. A tilted angle of 19° was detected between the cytosine ring of gemcitabine and the inner surface of SWCNT. In comparison to its conformation in the free form, no significant difference was observed on the torsion angle between the five- (ribose) and the six- (cytosine) membered rings. However, gemcitabine inside the SWCNT was found to have a lower number of solvating water molecules but with a stronger net solvation than the drug in the free state. This is due to the collaborative interactions between gemcitabine and the surface of the SWCNT. In addition, the steered molecular dynamics simulation (SMD) approach was employed to investigate the binding free energy for gemcitabine moving from one end to another end throughout the SWCNT. In excellent agreement with that yielded from the classical MD, the SMD energy profile confirms that the drug molecule prefers to locate inside the SWCNT.

2, 2, Thai Journal of Genetics

Quantum mechanical calculations have been carried out to investigate the structural properties and the interaction between water molecules and silanol groups on the surface of silicalite-1. The (010) surface, which is perpendicular to the straight channel, has been selected and represented by three fragments taken from different parts of the surface. Calculations have been performed using different levels of accuracy: HF/6-31G(d,p), B3LYP/6-31G(d,p), HF/6-31++G(d,p), and B3LYP/6-31++G(d,p). The basis set superposition error has been taken into account. The geometry of the silanol groups and that of the water molecules have been fully optimized. The results show that the most stable conformation takes place when a water molecule forms two hydrogen bonds with two silanols, with only one silanol lying on the opening of the pore of the straight channel. The corresponding binding energy is -48.82 kJ/mol. These areas are supposed to be the first binding sites which have to be covered when the water molecule approaches the surface. When the water loading increases, the next favorable silanols are those of the opening of the pore in which the four possible complex conformations yield a binding energy between -25.62 and -37.41 kJ/mol. It was also found that the calculated O-H bond length of the silanol in the free form was slightly shorter than that in the complex. In terms of the stretching frequency, the complexation leads to a red shift of the O-H stretching of the silanol group.

Quantum mechanical calculations at different levels, HF/6-31G(d,p), B3LYP/6-31G(d,p), HF/6-31++G(d,p), and B3LYP/6-31++G(d,p), have been applied to investigate the interaction between guest molecules, water and methane, and the external surface of silicalite-1. The (010) surface which is perpendicular to the straight channel was selected and the silanol groups on the surface were generated by adding hydrogen atoms to the broken O-Si bonds. The complex geometries were fully optimized. The optimal B3LYP/6-31++G(d,p) binding energies on the external (010) surface of −13.84 kcal/mol and −0.26 kcal/mol were yielded for water and methane molecule, respectively. With the same method, the binding energy in the channel was −4.76 kcal/mol for water and −3.87 kcal/mol for methane binding. This leads to the estimated energy barrier to enter the straight channel via binding with the silanol group on the (010) surface of silicate-1 of 9.08 kcal/mol for water while this process is barrier free for methane molecules.

Department of Chemistry, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand Department of Mathematics, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand Department of Physics, Faculty of Science and Technology, Thammasat University, Rangsit, Pathumthani 12121, Thailand Gorlaeus Laboratories, Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands