Crystal structure, intermolecular interactions, charge-density distribution and ADME properties of the acridinium 4-nitrobenzoate and 2-amino-3-methylpyridinium 4-nitrobenzoate salts: a combined experimental and theoretical study

Acridines are a class of bioactive agents which exhibit high biological stability and the ability to intercalate with DNA; they have a wide range of applications. Pyridine derivatives have a wide range of biological activities. To enhance the properties of acridine and 2-amino-3-methylpyridine as the active pharmaceutical ingredient (API), 4-nitrobenzoic acid was chosen as a coformer. In the present study, a mixture of acridine and 4-nitrobenzoic acid forms the salt acridinium 4-nitrobenzoate, C13H10N+·C7H4NO4- (I), whereas a mixture of 2-amino-3-methylpyridine and 4-nitrobenzoic acid forms the salt 2-amino-3-methylpyridinium 4-nitrobenzoate, C6H9N2+·C7H4NO4- (II). In both salts, protonation takes place at the ring N atom. The crystal structure of both salts is predominantly governed by hydrogen-bond interactions. In salt I, C-H...O and N-H...O interactions form an infinite chain in the crystal, whereas in salt II, intermolecular N-H...O interactions form an eight-membered R22(8) ring motif. A theoretical charge-density analysis reveals the charge-density distribution of the inter- and intramolecular interactions of both salts. An in-silico ADME analysis predicts the druglikeness properties of both salts and the results confirm that both salts are potential drug candidates with good bioavailability scores and there is no violation of the Lipinski rules, which supports the druglikeness properties of both salts. However, although both salts exhibit drug-like properties, salt I has higher gastrointestinal absorption than salt II and hence it may be considered a potential drug candidate.

Theoretical study to gain fundamental insight into reaction mechanism of N-S acyl transfer of N-sulfanylethylanilide-based protein labeling reagent on protein surface

Elucidation of protein function is one of the central issues in the field of life sciences. To study the function of proteins not in isolation, but in a cell or its lysate, thus, it is necessary to selectively label the target protein in a mixture. Affinity labeling is one of several widely used methods for selective labeling; however, this method has the disadvantage that the labeling reagent is always activated, albeit weakly. Therefore, fine-tuning of the reactivity and/or reaction conditions is generally required for successful target-selective labeling. We previously developed a new affinity labeling reagent with N-sulfanylethylanilide (SEAlide) as a key reactive unit. It was designed based on the following hypotheses. SEAlide is less reactive and does not label in the absence of a target protein. Upon target binding, amino acid side-chain functional groups on the target surface convert SEAlide into a thioester form via N-S acyl transfer, allowing the target to be labeled. However, no evidence has been obtained so far to directly prove the hypothesis. In this study, we examine whether amino acid side-chain functional groups can activate SEAlide from the viewpoint of theoretical chemistry. The theoretical studies show that the activation free energy and enthalpy of the acyl transfer of SEAlide are reduced in the presence of methylammonium, which is a model for the protonated side chain of Lys, and acetate, which is a model for the deprotonated side chain of Asp/Glu. It suggests that Lys and Asp/Glu side chains could potentially stabilize the activation transition states to accelerate the thioester formation. Furthermore, the significant decrease in the activation enthalpy indicates that the contribution of entropy to the transition state is large. This result supports the original hypothesis that the SEAlide-based labeling reagent is efficiently activated by binding to the target protein.

Elucidating the Excited State Behavior of Pyridyl Pyridinium Systems via Computational and Transient Absorption Studies of Tetrahedral Multichromophoric Arrays and their Model Compounds

The tetrahedral shape-persistent molecule 14+ , containing four identical pyridyl pyridinium units connected via a sp3 hybridized carbon atom, has been investigated in detail by means of steady-state and time resolved spectroscopy. Remarkable photophysical properties are observed, particularly in comparison with protonated and methylated analogues (1H4 8+ , 1Me4 8+ ), which exhibit substantially shorter excited state lifetimes and lower emission quantum yields. Theoretical studies have rationalized the behavior of the tetrameric molecules relative to the monomers, with DFT and TD-DFT calculations corroborating steady-state (absorption and emission) and transient absorption spectra. The behavior of the monomeric compounds (each consisting in one of the four identical subunits of the tetramers, i. e., 2+ , 2H2+ and 2Me2+ ) considerably differs from that of the tetramers, indicating a strong electronic interaction between the subunits in the tetrameric species, likely promoted by the homoconjugation through the connecting sp3  C atom. 2+ is characterized by a peculiar S1 -S2 excited state inversion, whereas the short-lived emitting S1 state of 2H2+ and 2Me2+ exhibits a partial charge-transfer character, as substantiated by spectro-electrochemical studies. Among the six investigated systems, only 14+ is a sizeable luminophore (Φem =0.15), which is related to the peculiar features of its singlet state.

Theoretical Understanding on the Facilitated Photoisomerization of a Carbonyl Supported Borane System

Boron compound BOMes2 containing an internal B-O bond undergoes highly efficient photoisomerization, followed by sequential structural transformations, resulting in a rare eight-membered B, O-heterocycle (S. Wang, et al. Org. Lett. 2019, 21, 5285-5289). In this work, the detailed reaction mechanisms of such a unique carbonyl-supported tetracoordinate boron system in the first excited singlet (S1 ) state and the ground (S0 ) state were investigated by using the complete active space self-consistent field and its second-order perturbation (MS-CASPT2//CASSCF) method combined with time-dependent density functional theory (TD-DFT). Moreover, an imine-substituted tetracoordinated organic boron system (BNMes2 ) was selected for comparative study to explore the intrinsic reasons for the difference in reactivity between the two types of compounds. Steric factor was found to influence the photoisomerization activity of BNMes2 and BOMes2 . These results rationalize the experimental observations and can provide helpful insights into understanding the excited-state dynamics of heteroatom-doped tetracoordinate organoboron compounds, which facilitates the rational design of boron-based materials with superior photoresponsive performances.

On the Importance of Halogen and Chalcogen Bonds in the Solid State of Nucleic Acids: A Combined Crystallographic and Theoretical Perspective

In this work, intra- and intermolecular halogen and chalcogen bonds (HlgBs and ChBs, respectively) present in the solid state of nucleic acids (NAs) have been studied at the RI-MP2/def2-TZVP level of theory. To achieve this, a Protein Data Bank (PDB) survey was carried out, revealing a series of structures in which Br/I or S/Se/Te atoms belonging to nucleobases or pentose rings were involved in noncovalent interactions (NCIs) with electron-rich species. The energetics and directionality of these NCIs were rationalized through a computational study, which included the use of Molecular Electrostatic Potential (MEP) surfaces, the Quantum Theory of Atoms in Molecules (QTAIM), and Non Covalent Interaction plot (NCIplot) and Natural Bonding Orbital (NBO) techniques.

Three Iodoargentate-Based Hybrids Decorated by Metal Complexes: Structures, Optical/Photoelectric Properties and Theoretical Studies

So far, the development of new iodoargentate-based hybrids, especially those compounds with metal complex cations, and the understanding of their structure-activity relationships have been of vital importance but full of challenges. Herein, using the in-situ-generated metal complex cations as structural directing agents, three new iodoargentate-based hybrids, namely, [Co(phen)3]Ag2PbI6 (phen = 1,10-phenanthroline; 1), [Ni(5,5-dmpy)3]Ag7I9·CH3CN (5,5-dmpy = 5,5-dimethyl-2,2-bipyridine; 2) and [Co(5,5-dmpy)3]Ag5I8 (3), have been solvothermally prepared and then structurally characterized. Compound 1 represents one new heterometallic Ag-Pb-I compound characteristic of the chain-like [Ag2PbI6]n2n- anions. Compound 2 features the straight one-dimensional (1D) [Ag7I9]n2n- anionic moieties, while compound 3 contains infrequent two types of curved [Ag5I8]n3n- anions. Optical properties reveal that the title compounds exhibit interesting semiconductor behaviors with the band gaps of 1.59-2.78 eV, which endow them with good photoelectric switching performances under the alternate light irradiations. We also present their Hirshfeld surface analyses, and the theoretical studies (band structures, density of states (DOS) and partial density of states (PDOS)).

Raman Spectroscopic Study of Five Typical Plasticizers Based on DFT and HF Theoretical Calculation

Phthalic acid esters (PAEs) are the most commonly used plasticizers, and long-term or high levels of exposure to PAEs have a huge potential risk to human health. In this study, the theories of Hartree-Fock (HF) and density functional theory (DFT) with different hybrid methods and basis sets were used to calculate the theoretical Raman spectra of five PAEs, and the comparison of calculated spectra between different theories, hybrid methods, and basis sets was conducted to determine the suitable theory with hybrid method and basis set for PAEs. Also, the Raman vibrations were assigned to the Raman peaks of PAEs according to the theoretical and experimental Raman spectra. The results indicate that DFT is more suitable for the theoretical study of PAEs than HF. In DFT, the hybrid method of B3LYP is more applicable to the theoretical study of PAEs than B3PW91, and the basis set of 6-311G(d, p) obtains the most consistent theoretical Raman spectra with the experimental spectra for PAEs. This study finds the optimal combination of the theoretical method and basis set for PAEs, and it will contribute to the establishment of the Raman fingerprint and the development of rapid detection for PAEs in the future.

Theoretical and Anti-Klebsiella pneumoniae Evaluations of Substituted 2,7-dimethylimidazo[1,2-a]pyridine-3-carboxamide and Imidazopyridine Hydrazide Derivatives

A series of multistep synthesis protocols was adopted to synthesize substituted imidazopyridines (IMPs) (SM-IMP-01 to SM-IMP-13, and DA-01-05). All substituted IMPs were then characterized using standard spectroscopic techniques such as ¹H-NMR, ¹³C-NMR, elemental analyses, and mass spectrometry. Our both in vitro qualitative and quantitative results for antibacterial analysis, against Klebsiella pneumoniae ATCC 4352 and Bacillus subtilis ATCC 6051 suggested that all compounds essentially exhibited activity against selected strains of bacteria. Our DFT analyses suggested that the compounds of the SM-IMP-01-SM-IMP-13 series have HOMO/LUMO gaps within 4.43-4.69 eV, whereas the compounds of the DA-01-DA-05 series have smaller values of the HOMO/LUMO gaps, 3.24-4.17 eV. The lowest value of the global hardness and the highest value of the global softness, 2.215 and 0.226 eV, respectively, characterize the compound SM-IMP-02; thus, it is the most reactive compound in the imidazopyridine carboxamide series (except hydrazide series). This compound also depicted lesser MIC values against Klebsiella pneumoniae ATCC 4352 and Bacillus subtilis ATCC 6051 as 4.8 µg/mL, each. In terms of another series, hydrazide DA-05 depicted strong antimicrobial actions (MIC: 4.8 µg/mL against both bacterial strains) and also had the lowest energy gap (3.24 eV), higher softness (0.309 eV), and lesser hardness (1.62 eV). Overall, when we compare qualitative and quantitative antimicrobial results, it is been very clear that compounds with dibromo substitutions on imidazopyridine (IMP) rings would act as better antimicrobial agents than those with -H at the eighth position on the IMP ring. Furthermore, substituents of higher electronegativities would tend to enhance the biological activities of dibromo-IMP compounds. DFT properties were also well comparable to this trend and overall, we can say that the electronic behavior of compounds under investigation has key roles in their bioactivities.

Inorganic Drugs as a Tool for Protein Structure Solving and Studies on Conformational Changes

Inorganic drugs are capable of tight interactions with proteins through coordination towards aminoacidic residues, and this feature is recognized as a key aspect for their pharmacological action. However, the "protein metalation process" is exploitable for solving the phase problem and structural resolution. In fact, the use of inorganic drugs bearing specific metal centers and ligands capable to drive the binding towards the desired portions of the protein target could represent a very intriguing and fruitful strategy. In this context, a theoretical approach may further contribute to solve protein structures and their refinement. Here, we delineate the main features of a reliable experimental-theoretical integrated approach, based on the use of metallodrugs, for protein structure solving.

Inverse Electron-Demanding Diels-Alder Reactions in the Chemical Synthesis of Prenylated Indole Alkaloids Containing a Bicycle[2.2.2]diazaoctane Moiety: A Theoretical Study

The Diels-Alder reaction is believed to be a key step in the biosynthesis of prenylated indole alkaloids containing a bicycle[2.2.2]diazaoctane moiety. Many chemical syntheses of bicyclic structures by Diels-Alder reactions have been reported, but the reaction mechanism remains underexplored. We have carried out DFT calculations on both acid- and base-promoted Diels-Alder reactions in these syntheses and reveal that the reactions occur through an inverse-electron demand mechanism. We hope that the new mechanism is helpful for the mechanistic understanding of the biosynthesis of this class of important natural products.

Sustainability Study of Concrete Blocks with Wood Chips Used in Structural Walls in Seismic Areas

The concept of sustainability has become a priority in the construction field, in a context where there is an increasing discussion about reducing carbon dioxide emissions, as the construction industry is one of the most polluting industries with a focus on the production of building materials. At present, the classic solution used for structural masonry walls worldwide is the ceramic block. Given that the production of ceramic blocks represents an environmentally polluting process, the alternative solution of using concrete blocks with wood chips is proposed. The proposed solution is more environmentally friendly, both in terms of production technology and materials used, as it is made of wood chips, wood being a sustainable material. These types of blocks are currently used in non-seismic areas due to their poor structural performance. This paper deals with a study on the use of recyclable materials, such as wood chips, from waste materials and aims to propose viable solutions for the use of this type of blocks for structural walls in seismic areas. Two solutions, including concrete blocks with wood chips, have been proposed and numerical analyses have been carried out. Numerical analyses were also carried out for the classical solutions, so that, finally, a comparison could be made between them from a structural point of view. Following the numerical analysis of four types of walls, the two proposed solutions of concrete blocks with wood chips had the best results in terms of force-displacement relationship. Moreover, the quantitative results are presented in a force-displacement graph for the four wall types. This stage represents the first phase of the research, while phase II will continue with experimental tests of the proposed solutions.

Thermal Analysis and Prediction Methods for Temperature Distribution of Slab Track Using Meteorological Data

The structural temperature distribution, especially temperature difference caused by solar radiation, has a great impact on the deformation and curvature of the concrete slab tracks of high-speed railways. Previous studies mainly focused on the temperature prediction of slab tracks, while how the temperature distribution is affected by environmental conditions has been rarely investigated. Based on the integral transformation method, this work presents an analytical method to determine and decompose the temperature distribution of the concrete slab track. A field temperature test of a half-scaled specimen of concrete slab track was conducted to validate the developed methodology. In the proposed method, we decompose the temperature distribution of the slab track into an initial temperature component and a boundary temperature component. Then, the boundary temperature components caused by solar radiation and atmospheric temperature are investigated, respectively. The results show that the solar radiation plays a significant role in the nonlinear temperature distribution, while the atmospheric temperature has little effect. By contrast, the temperature change in the slab surface resulting from the atmospheric temperature accounts on average for only 5% in the hot weather condition. The proposed method establishes a relation between the structural temperature and meteorological parameters (i.e., the solar radiation and atmospheric temperature). Consequently, the temperature distribution of the concrete slab track is predicted via the meteorological parameters.

Phenoxy- and Phenylamino-Heterocyclic Quinones: Synthesis and Preliminary Anti-Pancreatic Cancer Activity

The successful application of fragment-based drug discovery strategy for the efficient synthesis of phenoxy- or phenylamino-2-phenyl-benzofuran, -benzoxazole and -benzothiazole quinones is described. Interestingly, in the final step of the synthesis of the target compounds, unusual results were observed on the regiochemistry of the reaction of bromoquinones with phenol and aniline. A theoretical study was carried out for better understanding the factors that control the regiochemistry of these reactions. The substituted heterocyclic quinones were evaluated in vitro to determine their cytotoxicity by the MTT method in three pancreatic cancer cell lines (MIA-PaCa-2, BxPC-3, and AsPC-1). Phenoxy benzothiazole quinone 26a showed potent cytotoxic activity against BxPC-3 cell lines, while phenylamino benzoxazole quinone 20 was the most potent on MIA-PaCa-2 cells. Finally, electrochemical properties of these quinones were determined to correlate with a potential mechanism of action. All these results, indicate that the phenoxy quinone fragment led to compounds with increased activity against pancreatic cancer cells.

Insights into the Activation Mode of α-Carbonyl Sulfoxonium Ylides in Rhodium-Catalyzed C-H Activation: A Theoretical Study

A computational study has been performed to investigate the mechanism of Rh^III‐catalyzed C−H bond activation using sulfoxonium ylides as a carbene precursor. The stepwise and concerted activation modes for sulfoxonium ylides were investigated. Detailed theoretical results showed that the favored stepwise pathway involves C−H bond activation, carbonization, carbene insertion, and protonation. The free energy profiles for dialkylation of 2‐phenylpyridine were also calculated to account for the low yield of this reaction. Furthermore, the substituent effect was elucidated by comparing the energy barriers for the protonation of meta‐ and para‐substituted sulfoxonium ylides calculated by density functional theory.

Magnetic Properties in Mn-Doped δ-MoN: A Systematic Density Functional Theory Study

Due to the potential applications of transition metal nitrides in modern electronic and spintronic devices, we have systematically studied the magnetic properties of δ-MoN induced by the Mn dopant, with the goal of identifying the origin of magnetism and figuring out the magnetic coupling mechanism between the Mn dopants. Based on the density functional theory, one Mn atom doped at different Mo sites (2a and 6c in the International Tables) in the unit cell of δ-MoN was firstly studied. It was found that the Mn dopant located at the 2a or 6c site leads to significant spin splitting of the density of states, suggesting that the Mn doping induces magnetism in δ-MoN. The calculations were then extended to a 2 × 1 × 2 supercell, which contains two impurity Mn atoms. Detailed analysis reveals that the different couplings of the Mn–Mn pair cannot be simply attributed to the different Mn–Mn distances but are closely related to the electronic processes that take place in the segment (–N– or –N–Mo–N–) that connects two Mn dopants. The mechanisms responsible for the FM/AFM coupling of the Mn–Mn pairs are the superexchange and the p–d exchange mediated by the N atoms, and the d–d coupling between the host Mo atom and the Mn dopant.

Synthesis and Characterization of Zn-Organic Frameworks Containing Chitosan as a Low-Cost Inhibitor for Sulfuric-Acid-Induced Steel Corrosion: Practical and Computational Exploration

In this work, a Zn-benzenetricarboxylic acid (Zn@H3BTC) organic framework coated with a dispersed layer of chitosan (CH/Zn@H3BTC) was synthesized using a solvothermal approach. The synthesized CH/Zn@H3BTC was characterized by Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscope (FESEM), thermal gravimetric analysis (TGA), and Brunauer, Emmett, and Teller (BET) surface area. The microscopic observation and the analysis of the BET surface area of CH/Zn@H3BTC nanocomposites indicated that chitosan plays an important role in controlling the surface morphology and surface properties of the Zn@H3BTC. The obtained findings showed that the surface area and particle size diameter were in the range of 80 m2 g-1 and 800 nm, respectively. The corrosion protection characteristics of the CH/Zn@H3BTC composite in comparison to pristine chitosan on duplex steel in 2.0 M H2SO4 medium determined by electrochemical (E vs. time, PDP, and EIS) approaches exhibited that the entire charge transfer resistance of the chitosan- and CH/Zn@H3BTC-composite-protected films on the duplex steel substrate was comparatively large, at 252.4 and 364.8 Ω cm2 with protection capacities of 94.1% and 97.8%, respectively, in comparison to the unprotected metal surface (Rp = 20.6 Ω cm2), indicating the films efficiently protected the metal from corrosion. After dipping the uninhabited and protected systems, the surface topographies of the duplex steel were inspected by FESEM. We found the adsorption of the CH/Zn@H3BTC composite on the metal interface obeys the model of the Langmuir isotherm. The CH/Zn@H3BTC composite revealed outstanding adsorption on the metal interface as established by MD simulations and DFT calculations. Consequently, we found that the designed CH/Zn@H3BTC composite shows potential as an applicant inhibitor for steel protection.

Flexural Behavior of T-Shaped UHPC Beams with Varying Longitudinal Reinforcement Ratios

In order to investigate the transverse flexural behavior of the UHPC waffle deck, a total of six T-shaped UHPC beams, with varying longitudinal reinforcement ratios, were tested and analyzed. The experiments, including material tests of UHPC and beam tests, were conducted. The material tests of UHPC revealed that strain-hardening behavior in tension was exhibited, and the ratio of uniaxial compressive strength-to-cubic compressive strength was 0.85. The beam tests showed that all the T-shaped UHPC beams, even without longitudinal rebar, exhibited ductile behavior that was similar to that of properly reinforced concrete beams. As the longitudinal reinforcement ratio increased, more flexural cracks developed and a larger load-carrying capacity was provided. Furthermore, the sectional analysis for the ultimate flexural capacity of T-shaped UHPC beams was conducted. Simplified material models, under tension and compression, for UHPC were developed. Based on the reverse calculation from the experimental result, the relation between reduction factor to the ultimate tensile strength of UHPC, and longitudinal reinforcement ratios was formulated. As a result, the predictive equations for the ultimate flexural capacity of T-shaped UHPC beams were proposed, and agreed well with the experimental results in this study and existing studies, which indicates good validity of the proposed equations.

Detection of Early Warning Signs in Autism Spectrum Disorders: A Systematic Review

Due to the exponential increase of autism spectrum disorders’ prevalence in Western countries, it is necessary to improve early detection and intervention to enhance developmental milestones. This systematic review identified the most effective screening instrument, which can be used at an early age and which identifies the maximum number of autism cases. We identified several instruments with adequate predictive properties—the Autism Parent Screen for Infants (APSI), Battelle Development Inventory, second edition (BDI-2); Brief Infant-Toddler Social and Emotional Assessment (BITSEA); First Year Inventory (FYI); Infant-Toddler Checklist/Communication and Symbolic Behavior Scales Developmental Profile (ITC/CSBS-DP); Program of Research and Studies on AUTISM (PREAUT-Grid); Checklist for Early Signs of Developmental Disorders (CESDD); Social Attention and Communication Study (SACS); and the Screening Tool for Autism in Toddlers and Young Children (STAT)—that can be applied from 12 months of age in Western countries. The ITC/CSBS-DP has been proposed for universal screening from 12 months of age onwards, complemented by the Modified Checklist for Autism in Toddlers, Revised/Revised with Follow-Up (M-CHAT-R/F), which can be used from 15 months of age onwards. This strategy could improve early detection in at-risk children within the current health system, thus allowing for early intervention.

Charge Transfer Complex of Neostigmine with 2,3-Dichloro-5,6-Dicyano-1,4-Benzoquinone: Synthesis, Spectroscopic Characterization, Antimicrobial Activity, and Theoretical Study

Background

Electron donor-acceptor interactions are important molecular reactions for the activity of pharmacological compounds. The aim of the study is to develop a charge transfer (CT) complex: synthesis, characterization, antimicrobial activity, and theoretical study.

Method and Results

A solid CT complex of neostigmine (NSG) with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) was synthesized and characterized by infrared spectra, NMR, and UV-visible spectroscopy. The results confirm the formation of a CT complex. The stability of the CT complex between NSG and DDQ in acetonitrile was determined in solution via spectrophotometric measurement, ie, by calculating the formation constant, molar extinction coefficient, and different spectroscopic parameters. The stoichiometry of the formed NSG-DDQ complex was determined using Job's method. The absorption band of the NSG-DDQ complex can be used for the quantification of NSG.

Conclusion

The DFT geometry optimization of NSG, DDQ, and the CT complex and the UV comparative study of both theoretical and experimental structures are presented. The experimental results confirm the charge transfer structure. The bacterial study shows that the NSG-DDQ complex has good antibacterial activity against both Gram-positive and Gram-negative bacteria as well as antifungal activity against Candida albicans.

Theoretical and Experimental Studies on the Signal Propagation in Soil for Wireless Underground Sensor Networks

Wireless Underground Sensor Networks (WUSNs), an important part of Internet of things (IoT), have many promising applications in various scenarios. Signal transmission in natural soil undergoes path loss due to absorption, radiation, reflection and scattering. The variability and dynamic of soil conditions and complexity of signal attenuation behavior make the accurate estimation of signal path loss challenging. Two existing propagation models for predicting path loss are reviewed and compared. Friis model does not consider the reflection loss and is only applicable in the far field region. The Fresnel model, only applicable in the near field region, has not considered the radiating loss and wavelength change loss. A new two stage model is proposed based on the field characteristics of antenna and considers four sources of path loss. The two stage model has a different coefficient m in the near field and far field regions. The far field distance of small size antenna is determined by three criteria: 2 D²/λ, 5 D, 1.6 λ in the proposed model. The proposed two stage model has a better agreement with the field experiment data compared to Friis and Fresnel models. The coefficient m is dependent on the soil types for the proposed model in near field region. It is observed from experiment data that the m value is in the range of 0~0.20 for sandy soils and 0.433~0.837 for clayey silt.

Design and Synthesis of Gold-Gadolinium-Core-Shell Nanoparticles as Contrast Agent: a Smart Way to Future Nanomaterials for Nanomedicine Applications

INTRODUCTION

The development of biopolymers for the synthesis of Gd(III) nanoparticles, as therapeutics, could play a key role in nanomedicine. Biocompatible polymers are not only used for complex monovalent biomolecules, but also for the realization of multivalent active targeting materials as diagnostic and/or therapeutic hybrid nanoparticles. In this article, it was reported for the first time, a novel synthesis of Gd(III)-biopolymer-Au(III) complex, acting as a key ingredient of core-shell gold nanoparticles (Gd(@AuNPs).

MATERIAL AND METHODS

The physical and chemical evaluation was carried out by spectroscopic analytical techniques (Raman spectroscopy, UV-visible and TEM). The theoretical characterization by DFT (density functional theory) analysis was carried out under specific conditions to investigate the interaction between the Au and the Gd precursors, during the first nucleation step. Magnetic features with relaxivity measurements at 7T were also performed as well as cytotoxicity studies on hepatocyte cell lines for biocompatibility studies. The in vivo detailed dynamic biodistribution studies in mice to characterize the potential applications for biology as MRI contrast agents were then achieved.

RESULTS

Physical-chemical evaluation confirms the successful design and reaction supposed. Viabilities of TIB-75 (hepatocytes) cells were evaluated using Alamar blue cytotoxic tests with increasing concentrations of nanoparticles. In vivo biodistribution studies were then accomplished to assess the kinetic behavior of the nanoparticles in mice and characterize their stealthiness property after intravenous injection.

CONCLUSION

We demonstrated that Gd@AuNPs have some advantages to display hepatocytes in the liver. Particularly, these nanoconjugates give a good cellular uptake of several quantities of Gd@NPs into cells, while preserving a T1 contrast inside cells that provide a robust in vivo detection using T1-weighted MR images. These results will strengthen the role of gadolinium as complex to gold in order to tune Gd(@AuNPs) as an innovative diagnostic agent in the field of nanomedicine.

Role of Alkaline-Earth Metal-Catalyst: A Theoretical Study of Pyridines Hydroboration

Density functional theory (DFT) calculations have been performed to investigate the mechanism of alkaline-earth-metal-catalyzed hydroboration of pyridines with borane. In this reaction, the active catalytic species is considered to be an alkaline earth metal hydride complex when the corresponding alkaline earth metal is used as the catalyst. The theoretical results reveal that initiation of the catalytic cycle is hydride transfer to generate a magnesium hydride complex when β-diimine alkylmagnesium is used as a pre-catalyst. The magnesium hydride complex can undergo coordination of the pyridine reactant followed by hydride transfer to form a dearomatized magnesium pyridine intermediate. Coordination of borane and hydride transfer from borohydride to magnesium then give the hydroboration product and regenerate the active magnesium hydride catalyst. The rate-determining step of the catalytic cycle is hydride transfer to pyridine with a free energy barrier of 29.7 kcal/mol. Other alkaline earth metal complexes, including calcium and strontium complexes, were also considered. The DFT calculations show that the corresponding activation free energies for the rate-determining step of this reaction with calcium and strontium catalysts are much lower than with the magnesium catalyst. Therefore, calcium and strontium complexes can be used as the catalyst for the reaction, which could allow mild reaction conditions.

Crystal structure and theoretical study of (2E)-1-[4-hy-droxy-3-(morpholin-4-ylmeth-yl)phen-yl]-3-(thio-phen-2-yl)prop-2-en-1-one

In the title compound, C18H19NO3S, the morpholine ring adopts a chair conformation. The thio-phene ring forms dihedral angles of 26.04 (9) and 74.07 (10)° with the benzene ring and the mean plane of the morpholine ring, respectively. The mol-ecular conformation is stabilized by an O-H⋯N hydrogen bond. In the crystal, mol-ecules are connected through C-H⋯O hydrogen bonds, forming wave-like layers parallel to the ab plane, which are further linked into a three-dimensional network by C-H⋯π inter-actions involving the benzene rings and the methyl-ene H atoms of the morpholine rings.

Insight into resistance mechanism of anaplastic lymphoma kinase to alectinib and JH-VIII-157-02 caused by G1202R solvent front mutation

BACKGROUND

Mutated anaplastic lymphoma kinase (ALK) drives the development of advanced non-small cell lung cancer (NSCLC). Most reported small-molecule inhibitors targeting the ALK domain do not display good inhibition of the G1202R solvent front mutation. The solvent front mutation was assumed to hinder drug binding. However, a different fact could be uncovered by the simulations reported in this study through a structural analog of alectinib (JH-VIII-157-02), which demonstrated potent effects against the G1202R mutation.

METHODS

Molecular docking, conventional molecular dynamics (MD) simulations, free energy calculations, and umbrella sampling (US) simulations were carried out to make clear the principles of the binding preferences of alectinib and JH-VIII-157-02 toward ALKWT and the ALK G1202R (ALKG1202R) mutation.

RESULTS

JH-VIII-157-02 has similar binding affinities to both ALKWT and ALKG1202R whereas it has has a much lower binding affinity for alectinib to ALKG1202R. Analysis of individual energy terms indicate the major variation involves the van der Waals and entropy terms. Structural analysis reveals that the conformational change of the ATP-binding glycine-rich loop was primarily responsible for the alectinib resistance, not JH-VIII-157-02. In addition, US simulations prove JH-VIII-157-02 has similar dissociative processes from both ALKWT and ALKG1202R, while alectinib is more easily dissociated from ALKG1202R than from ALKWT, thus indicating lesser residence time.

CONCLUSION

Both the binding affinity and the drug residence time should be emphasized in rational drug design to overcome the G1202R solvent front mutation in ALK resistance.

Insight into resistance mechanisms of AZD4547 and E3810 to FGFR1 gatekeeper mutation via theoretical study

Inhibitors targeting the amplification of the fibroblast growth factor receptor 1 (FGFR1) have found success in the treatment of FGFR1-positive squamous cell lung and breast cancers. A secondary mutation of gatekeeper residue (V561M) in the binding site has been linked to the acquired resistance. Recently, two well-known small molecule inhibitors of FGFR1, AZD4547 and E3810, reported that the V561M mutation confers significant resistance to E3810, while retaining affinity for AZD4547. FGFR1 is widely investigated as potential therapeutic target, while there are few computational studies made to understand the resistance mechanisms about FGFR1 V561M gatekeeper mutation. In this study, molecular docking, classical molecular dynamics simulations, molecular mechanics/generalized born surface area (MM/GBSA) free energy calculations, and umbrella sampling (US) simulations were carried out to make clear the principle of the binding preference of AZD4547 and E3810 toward FGFR1 V561M gatekeeper mutation. The results provided by MM/GBSA reveal that AZD4547 has similar binding affinity to both FGFR1^WT and FGFR1^V561M, whereas E3810 has much higher binding affinity to FGFR1^WT than to FGFR1^V561M. Comparison of individual energy terms indicates that the major variation of E3810 between FGFR1^WT and FGFR1^V561M are van der Waals interactions. In addition, US simulations prove that the potential of mean force (PMF) profile of AZD4547 toward FGFR1^WT and FGFR1^V561M has similar PMF depth. However, the PMF profile of E3810 toward FGFR1^WT and FGFR1^V561M has much higher PMF depth, suggesting that E3810 is more easily dissociated from FGFR1^V561M than from FGFR1^WT. The results not only show the drug-resistance determinants of FGFR1 gatekeeper mutation but also provide valuable implications and provide vital clues for the development of new inhibitors to combat drug resistance.

Air-water partition coefficients for a suite of polycyclic aromatic and other C10 through C20 unsaturated hydrocarbons

The air-water partition coefficients (Kaw) for 86 large polycyclic aromatic hydrocarbons and their unsaturated relatives were estimated using high-level G4(MP2) gas and aqueous phase calculations with the SMD, IEFPCM-UFF, and CPCM solvation models. An extensive method validation effort was undertaken which involved confirming that, via comparisons to experimental enthalpies of formation, gas-phase energies at the G4(MP2) level for the compounds of interest were at or near thermochemical accuracy. Investigations of the three solvation models using a range of neutral and ionic compounds suggested that while no clear preferential solvation model could be chosen in advance for accurate Kaw estimates of the target compounds, the employment of increasingly higher levels of theory would result in lower Kaw errors. Subsequent calculations on the polycyclic aromatic and unsaturated hydrocarbons at the G4(MP2) level revealed excellent agreement for the IEFPCM-UFF and CPCM models against limited available experimental data. The IEFPCM-UFF-G4(MP2) and CPCM-G4(MP2) solvation energy calculation approaches are anticipated to give Kaw estimates within typical experimental ranges, each having general Kaw errors of less than 0.5 log10 units. When applied to other large organic compounds, the method should allow development of a broad and reliable Kaw database for multimedia environmental modeling efforts on various contaminants.

A Pilot Test of Self-Affirmations to Promote Smoking Cessation in a National Smoking Cessation Text Messaging Program

Background

Although effective smoking cessation treatments, including mHealth interventions, have been empirically validated and are widely available, smoking relapse is likely. Self-affirmation, a process through which individuals focus on their strengths and behaviors, has been shown to reduce negative effects of self-threats and to promote engagement in healthier behavior.

Objective

To assess the feasibility of incorporating self-affirmations into an existing text messaging-based smoking cessation program (Smokefree TXT) and to determine whether self-affirmation led to greater engagement and higher cessation rates than the standard intervention.

Methods

Data were collected from smokers (n=1261) who subscribed to a free smoking cessation program and met eligibility criteria. The intervention lasted 42 days. The original design was a 2 (Baseline affirmation: 5-item questionnaire present vs absent) × 2 (Integrated affirmation: texts present vs absent) factorial design. Only 17 eligible users completed all baseline affirmation questions and these conditions did not influence any outcomes, so we collapsed across baseline affirmation conditions in analysis. In the integrated affirmation conditions, affirmations replaced approximately 20% of texts delivering motivational content.

Results

In all, 687 users remained enrolled throughout the 42-day intervention and 81 reported smoking status at day 42. Among initiators (n=1261), self-affirmation did not significantly improve (1) intervention completion, (2) days enrolled, (3) 1-week smoking status, or (4) 6-week smoking status (all Ps>.10); and among the 687 completers, there were no significant effects of affirmation on cessation (Ps>.25). However, among the 81 responders, those who received affirmations were more likely to report cessation at 6 weeks (97.5%; 39 of 40) than those not given affirmations (78.1%; 32 of 41; χ²(1)=7.08, P=.008).

Conclusion

This proof-of-concept study provides preliminary evidence that self-affirmation can be integrated into existing text-based cessation programs, as the affirmations did not lead to any adverse effects (ie, less engagement or lower rates of cessation). Among those who reported smoking status at the end of the intervention period (6.4% of eligible respondents), affirmations facilitated cessation. This study provides a “proof-of-concept” that brief, low-touch interventions may be integrated into a text messaging program with potential benefits, minimal disruption to the program or users, and little cost. Many questions remain regarding how self-affirmation and similar approaches can promote engagement in population interventions.

Properties, theoretical study and crystal structure of 3-benzothiazole-9-ethyl carbazole

The title compound of 3-benzothiazole-9-ethyl carbazole was synthesized by the reaction of 3-aldehyde-9-ethyl carbazole and 2-aminothiophenol. The compound was characterized by (1) H nuclear magnetic resonance (NMR) and mass spectrometry (MS). Its crystal structure was obtained and determined by single crystal X-ray diffraction. The results showed that the crystal belongs to the orthorhombic crystal system and the cell parameters of space group P2(1)2(1)2(1) were a = 5.6626 (12) Å, b = 12.606 (3) Å, c = 22.639 (5) Å, α = 90°, β = 90°, γ = 90°, V = 1616.0 (6) Å(3) , Z = 4, Dc = 1.350 mg/m(3) . The UV-vis and fluorescence spectra were also studied preliminarily. The fluorescence spectra of the title compound with bovine serum albumin (BSA) showed that BSA could be marked with the compound and the stability constant between them was 0.82 × 10(7)  M(-1) . Meanwhile, the crystal and molecule were theoretically surveyed by density functional tight-binding (DFTB). The results showed that there was an orbital overlap for lowest unoccupied molecular orbital (LUMO) between the neighbouring molecules for the crystal, which is different from the molecule structure. It was also showed that the crystal structure is a non-conductor. Copyright © 2016 John Wiley & Sons, Ltd.

A QM/MM study of the reaction mechanism of (R)-hydroxynitrile lyases from Arabidopsis thaliana (AtHNL)

Hydroxynitrile lyases (HNLs) catalyze the conversion of chiral cyanohydrins to hydrocyanic acid (HCN) and aldehyde or ketone. Hydroxynitrile lyase from Arabidopsis thaliana (AtHNL) is the first R-selective HNL enzyme containing an α/β-hydrolases fold. In this article, the catalytic mechanism of AtHNL was theoretically studied by using QM/MM approach based on the recently obtained crystal structure in 2012. Two computational models were constructed, and two possible reaction pathways were considered. In Path A, the calculation results indicate that the proton transfer from the hydroxyl group of cyanohydrin occurs firstly, and then the cleavage of C1-C2 bond and the rotation of the generated cyanide ion (CN(-)) follow, afterwards, CN(-) abstracts a proton from His236 via Ser81. The C1-C2 bond cleavage and the protonation of CN(-) correspond to comparable free energy barriers (12.1 vs. 12.2 kcal mol(-1)), suggesting that both of the two processes contribute a lot to rate-limiting. In Path B, the deprotonation of the hydroxyl group of cyanohydrin and the cleavage of C1-C2 bond take place in a concerted manner, which corresponds to the highest free energy barrier of 13.2 kcal mol(-1). The free energy barriers of Path A and B are very similar and basically agree well with the experimental value of HbHNL, a similar enzyme of AtHNL. Therefore, both of the two pathways are possible. In the reaction, the catalytic triad (His236, Ser81, and Asp208) acts as the general acid/base, and the generated CN(-) is stabilized by the hydroxyl group of Ser81 and the main-chain NH-groups of Ala13 and Phe82.

Prediction of the air-water partition coefficient for perfluoro-2-methyl-3-pentanone using high-level Gaussian-4 composite theoretical methods

The air-water partition coefficient (Kaw) of perfluoro-2-methyl-3-pentanone (PFMP) was estimated using the G4MP2/G4 levels of theory and the SMD solvation model. A suite of 31 fluorinated compounds was employed to calibrate the theoretical method. Excellent agreement between experimental and directly calculated Kaw values was obtained for the calibration compounds. The PCM solvation model was found to yield unsatisfactory Kaw estimates for fluorinated compounds at both levels of theory. The HENRYWIN Kaw estimation program also exhibited poor Kaw prediction performance on the training set. Based on the resulting regression equation for the calibration compounds, the G4MP2-SMD method constrained the estimated Kaw of PFMP to the range 5-8 × 10(-6) M atm(-1). The magnitude of this Kaw range indicates almost all PFMP released into the atmosphere or near the land-atmosphere interface will reside in the gas phase, with only minor quantities dissolved in the aqueous phase as the parent compound and/or its hydrate/hydrate conjugate base. Following discharge into aqueous systems not at equilibrium with the atmosphere, significant quantities of PFMP will be present as the dissolved parent compound and/or its hydrate/hydrate conjugate base.

99Tc NMR as a promising technique for structural investigation of biomolecules: theoretical studies on the solvent and thermal effects of phenylbenzothiazole complex

The phenylbenzothiazole compounds show antitumor properties and are highly selective. In this paper, the (99)Tc chemical shifts based on the ((99m)Tc)(CO)3 (NNO) complex conjugated to the antitumor agent 2-(4'-aminophenyl)benzothiazole are reported. Thermal and solvent effects were studied computationally by quantum-chemical methods, using the density functional theory (DFT) (DFT level BPW91/aug-cc-pVTZ for the Tc and BPW91/IGLO-II for the other atoms) to compute the NMR parameters for the complex. We have calculated the (99)Tc NMR chemical shifts of the complex in gas phase and solution using different solvation models (polarizable continuum model and explicit solvation). To evaluate the thermal effect, molecular dynamics simulations were carried, using the atom-centered density matrix propagation method at the DFT level (BP86/LanL2dz). The results highlight that the (99)Tc NMR spectroscopy can be a promising technique for structural investigation of biomolecules, at the molecular level, in different environments.