Dynamics Simulations Of Molecules Research Articles

Molecular modeling and DFT studies of diazenylphenyl derivatives as a potential HBV and HCV antiviral agents

The need for novel antiviral drug particularly for hepatitis B (HBV) and C (HCV) virus cannot be over emphasized hence, this work focuses on the stability and intermolecular interaction of three diazenylphenyl compounds; 5-((E)-(4-((E)-(3-hydroxy-nitrosonaphthalen-1-yl)diazinyl)phenyl)diazinyl)-3,8a-dihydroquinolin-8-ol, (Z)-4-(E-(4-(E)-(2,4-dihydroxyphenyl)phenyl)diazinyl-2-(hydroxyamino)-4a,8a-dihyroapthalen-1(2H)-one, and 4-((E)-(4-((E)-(2-hydroxy-3-nitrosophenyl)diazenyl)phenyl)diazenyl)-4a,8a-dihydronaphthalen-1(4H)-one depicted as A, B and C respectively. We have performed a comprehensive quantum computational study to ascertain the drug likeness of the titled molecules. Interestingly, Compound C was found to be the most stable compound compared to A and B. In the Density of state (DOS) studies, hydrogen was observed to have the highest peak in the antibonding region whereas carbon has the highest values at the bonding molecular orbitals. Compound C have the highest second order perturbation energies. The molecular dynamics simulation of the individual molecules indicate that compound B + 4MWF complex has the highest binding energy than other complexes and the RMSD values indicate that the targeted K7F, 6CWT, 4MWF and 5YAX proteins are more conformationally stable when bound with compound B. Antiviral property of the titled molecules was investigated by docking with the selected viral proteins. The studied compounds were observed to have the highest binding affinity compared to Telbivudine and Sofosbuvir which were used as standard drugs.

15-Crown-5 ether as efficient electrolyte additive for performance enhancement of aqueous Zn-ion batteries

Aqueous rechargeable Zn-ion batteries (ZIBs) have been regarded as a complement to LIBs due to their merits in terms of high safety, low cost, environmentally benignity, and long cycle life. However, the Zn metal anode suffers from corrosion and parasitic reactions in the aqueous electrolyte, which lead to growth of byproduct flakes and hydrogen gas evolution in the Zn platting/stripping process. Here, an organic additive, 15-crown-5 ether (15-CE-5), is added into the aqueous ZnSO4 electrolyte to improve the Zn anode performance by altering the Zn2+ solvation sheath. Other CE molecules such as 12-CE-4 and 18-CE-6 are also tested, while their efficacies are inferior compared to that of 15-CE-5. The optimal concentration of 15-CE-5 in the ZnSO4 electrolyte is found to be 2 wt%, which enables the best performance of Zn anode in either Zn||Zn symmetric cells or MnO2||Zn full cells. Using this modified electrolyte, the Zn||Zn symmetric cell exhibits a cycle life of 770 h when tested at 2 mA cm−2 and a set capacity of 2 mAh cm−2, and the MnO2||Zn full cell shows enhanced and stable capacity over 1000 cycles. The experimental results are elucidated by theoretical studies including molecule dynamics simulations and density functional theory calculations.

Discovery of the Cryptic Sites of SARS-CoV-2 Papain-like Protease and Analysis of Its Druggability.

In late 2019, a new coronavirus (CoV) caused the outbreak of a deadly respiratory disease, resulting in the COVID-19 pandemic. In view of the ongoing pandemic, there is an immediate need to find drugs to treat patients. SARS-CoV-2 papain-like cysteine protease (PLpro) not only plays an important role in the pathogenesis of the virus but is also a target protein for the development of inhibitor drugs. Therefore, to develop targeted inhibitors, it is necessary to analyse and verify PLpro sites and explore whether there are other cryptic binding pockets with better activity. In this study, first, we detected the site of the whole PLpro protein by sitemap of Schrödinger (version 2018), the cavity of LigBuilder V3, and DeepSite, and roughly judged the possible activated binding site area. Then, we used the mixed solvent dynamics simulation (MixMD) of probe molecules to induce conformational changes in the protein to find the possible cryptic active sites. Finally, the TRAPP method was used to predict the druggability of cryptic pockets and analyse the changes in the physicochemical properties of residues around these sites. This work will help promote the research of SARS-CoV-2 PLpro inhibitors.

Sulindac acetohydrazide derivative attenuates against cisplatin induced organ damage by modulation of antioxidant and inflammatory signaling pathways

This study aimed to explore the mechanisms of action of a sulindac acetohydrazide derivative, N'-(4-dimethylaminobenzylidene)-2-1-(4-(methylsulfinyl) benzylidene)-5-fluoro-2-methyl-1H-inden-3-yl) acetohydrazide, against anticancer drug cisplatin induced organ damage. Using a rodent model, various markers of organ function and signaling pathways were examined and validated by molecular docking studies. The study involves five groups of animals: control, DMSO, CDDP, CDDP + DMFM, and DMFM. Biochemical enzyme activity, histopathology, tissue antioxidant, and oxidative stress markers were examined. RT-PCR and western blot analyses were conducted for the expression of inducible cyclooxygenase enzyme (COX-2), nuclear factor kappa beta (NF-κB), p65, IL-1, TNF-α, and inducible nitric oxide synthase (iNOS). Flow cytometry analysis of CD4 + TNF-α, CD4 + COX-2, and CD4 + STAT-3 cells in whole blood was performed. Structural and dynamic behavior of DMFM upon binding with receptor molecule molecular docking and dynamic simulations were performed using bioinformatics tools and software. Treatment with DMFM reversed cisplatin-induced malondialdehyde (MDA) and nitric oxide (NO) induction, whereas the activity of glutathione peroxidase (GPx), and superoxide dismutase (SOD) in the kidney, heart, liver, and brain tissues were increased. DMFM administration normalized plasma levels of biochemical enzymes. We observed a marked decline in CD4 + STAT3, TNF-α, and COX2 cell populations in whole blood after treatment with DMFM. DMFM downregulated the expression factors related to inflammation at the mRNA and protein levels, i.e., IL-1, TNF-α, iNOS, NF-κB, STAT-3, and COX-2. Dynamic simulations and in silico docking data supports the experimental findings. Our experimental and in silico results illustrated that DMFM may affect protective action against cisplatin-induced brain, heart, liver, and kidney damage via reduction of inflammation and ROS.

Identifying Vibrations that Control Non-adiabatic Relaxation of Polaritons in Strongly Coupled Molecule-Cavity Systems.

The strong light–matter coupling regime, in which excitations of materials hybridize with excitations of confined light modes into polaritons, holds great promise in various areas of science and technology. A key aspect for all applications of polaritonic chemistry is the relaxation into the lower polaritonic states. Polariton relaxation is speculated to involve two separate processes: vibrationally assisted scattering (VAS) and radiative pumping (RP), but the driving forces underlying these two mechanisms are not fully understood. To provide mechanistic insights, we performed multiscale molecular dynamics simulations of tetracene molecules strongly coupled to the confined light modes of an optical cavity. The results suggest that both mechanisms are driven by the same molecular vibrations that induce relaxation through nonadiabatic coupling between dark states and polaritonic states. Identifying these vibrational modes provides a rationale for enhanced relaxation into the lower polariton when the cavity detuning is resonant with specific vibrational transitions.

Target-based virtual screening, computational multiscoring docking and molecular dynamics simulation of small molecules as promising drug candidate affecting kinesin-like protein KIFC1.

The kinesin family member C1 (KIFC1) is an essential protein that facilitates the bipolar division of neoplastic cells. Inhibiting KIFC1 by small molecules is a lucrative strategy to impede bipolar mitosis leading to the apoptosis of cancerous cells. The research aims to envisage small-molecule inhibitors targeting KIFC1. The Mcule database, a comprehensive online digital platform containing more than five million chemical compounds, was used for structure-based virtual screening (SBVS). Druglikeness filtration sifted 2,293,282 chemical hits that further narrowed down to 49 molecules after toxicity profiling. Finally, 39 compounds that comply with the BOILED-Egg permeation predictive model of the ADME rules were carried forward for multiscoring docking using the AutoDock Vina inbuilt to Mcule drug discovery platform, DockThorand SwissDock tools. The mean of ΔG terms produced by docking tools was computed to find consensus top ligand hits. AZ82 exhibited stronger binding (Consensus ΔG: -7.99 kcal mol-1 ) with KIFC1 among reference inhibitors, for example, CW069 (-7.57 kcal mol-1 ) andSR31527 (-7.01 kcal mol-1 ). Ten ligand hits namely, Mcule-4895338547 (Consensus ΔG: -8.69 kcal mol-1 ), Mcule-7035674888 (-8.42 kcal mol-1 ), Mcule-5531166845 (-8.53 kcal mol-1 ), Mcule-3248415882 (-8.55 kcal mol-1 ), Mcule-291881733 (-8.41 kcal mol-1 ), Mcule-5918624394 (-8.44), Mcule-3470115427 (-8.47), Mcule-3686193135 (-8.18 kcal mol-1 ), Mcule-3955355291 (8.09 kcal mol-1 )and Mcule-9534899193 (-8.01 kcal mol-1 ) depicted strong binding interactions with KIFC1 in comparison to potential reference inhibitor AZ82. The top four ligands and AZ82 were considered for molecular dynamics simulation of 50 ns duration. Toxicity profiling, physicochemical properties, lipophilicity, solubility, pharmacokinetics, druglikeness, medicinal chemistry attributes, average potential energy, RMSD, RMSF, SASA, ΔGsolvand Rg analyses forecast the ligand mcule-4895338547 as a promising inhibitor of KIFC1.

Investigating the structure-activity relationship of marine polycyclic batzelladine alkaloids as promising inhibitors for SARS-CoV-2 main protease (Mpro)

Over a span of two years ago, since the emergence of the first case of the novel coronavirus (SARS-CoV-2) in China, the pandemic has crossed borders causing serious health emergencies, immense economic crisis and impacting the daily life worldwide. Despite the discovery of numerous forms of precautionary vaccines along with other recently approved orally available drugs, yet effective antiviral therapeutics are necessarily needed to hunt this virus and its variants. Historically, naturally occurring chemicals have always been considered the primary source of beneficial medications. Considering the SARS-CoV-2 main protease (Mpro) as the duplicate key element of the viral cycle and its main target, in this paper, an extensive virtual screening for a focused chemical library of 15 batzelladine marine alkaloids, was virtually examined against SARS-CoV-2 main protease (Mpro) using an integrated set of modern computational tools including molecular docking (MDock), molecule dynamic (MD) simulations and structure-activity relationships (SARs) as well. The molecular docking predictions had disclosed four promising compounds including batzelladines H–I (8–9) and batzelladines F-G (6–7), respectively according to their prominent ligand-protein energy scores and relevant binding affinities with the (Mpro) pocket residues. The best two chemical hits, batzelladines H–I (8–9) were further investigated thermodynamically though studying their MD simulations at 100 ns, where they showed excellent stability within the accommodated (Mpro) pocket. Moreover, SARs studies imply the crucial roles of the fused tricyclic guanidinic moieties, its degree of unsaturation, position of the N–OH functionality and the length of the side chain as a spacer linking between two active sites, which disclosed fundamental structural and pharmacophoric features for efficient protein-ligand interaction. Such interesting findings are greatly highlighting further in vitro/vivo examinations regarding those marine natural products (MNPs) and their synthetic equivalents as promising antivirals.

Investigations into the electronic properties of lorlatinib, an anti‐cancerous drug using DFT, wavefunction analysis and MD simulations

AbstractLung cancer is a kind of cancer with high morbidity and mortality rate, making it one of the most dangerous tumors to humanity's health and existence. Wavefunction dependent reactivity analysis, atom in molecule (AIM) and molecular dynamics (MD) simulations of lorlatinib (LTB) are reported in the present work. Electrophilicity index predicts the biological activity. The bond ellipticity describes the anisotropy of the curvature of electron density and its maximum value is at C15‐H32. Chemical environments, N8 = C26‐N7, C18 = C30 ≡ N9, and C15 = C14‐C13 are found to be highest delocalization regions. The complexes were stable throughout the simulation and amino acids involved in bringing the overall structural deviation are explored.

Gel polymer dominated ion charging mechanisms within graphene nanochannels

Revealing microscopic real-time ion transport behavior is critically-important for understanding the charging mechanisms of polymer electrolytes. Herein polymer dominated ion charging mechanism of LiCl/polyvinyl alcohol (PVA) gel polymer electrolytes within graphene nanochannels is observed by combined electrochemical quartz crystal microbalance (EQCM) and molecule dynamics (MD) simulations. This is substantially different with the conventional aqueous electrolytes, demonstrating the dominated role of PVA polymer (including polymer-ion and polymer-electrode interactions) in mediating the charging mechanisms. Specifically, in-situ EQCM measurement reveals that –OH polar groups of PVA exhibit more significant hindrance to cations than anions, yielding the charging mechanisms from Li+ adsorption/desorption (at 0 wt % PVA) to Li+/Cl− ion exchange dominated transport (at 40 wt % PVA). Furthermore, ionic flux is quantitatively characterized based on the non-equilibrium thermodynamics, and the charging resistance is revealed via combining constant potential method and equivalent electric circuits. More importantly, increasing PVA concentration remarkably affects the thermodynamic properties (e.g., dielectric property, angle distribution and number density), while almost identical capacitance is recognized because of higher dielectric constant of PVA molecules. By solving Poisson equation, this is further interpreted and invalidated by quantifying the contributions of ions, solvents and PVA molecules to the electric potentials.

Radiative thermalization in semiclassical simulations of light-matter interaction

Prediction of the equilibrium populations in quantum dynamics simulations of molecules exposed to black-body radiation has proved challenging for semiclassical treatments, with the usual Ehrenfest and Maxwell-Bloch methods exhibiting serious failures. In this context, we explore the behavior of a recently introduced semiclassical model of light-matter interaction derived from a dissipative Lagrangian [C. M. Bustamante, E. D. Gadea, A. Horsfield, T. N. Todorov, M. C. Gonz\'alez Lebrero, and D. A. Scherlis, Phys. Rev. Lett. 126, 087401 (2021)]. It is shown that this model reproduces the Boltzmann populations for two-level systems, predicting the black-body spectra in approximate agreement with Planck's distribution. In multilevel systems, small deviations from the expected occupations are seen beyond the first excited level. By averaging over fast oscillations, a rate equation is derived from the dissipative equation of motion that makes it possible to rationalize these deviations. Importantly, it enables us to conclude that this model will produce the correct equilibrium populations provided the occupations of the lowest levels remain close to unity, a condition satisfied at low temperature or small excitations.

Interaction Analysis of Odorant-Binding Protein 12 from Sirex noctilio and Volatiles from Host Plants and Symbiotic Fungi Based on Molecule Dynamics Simulation

As a quarantine pest of conifer, Sirex noctilio has caused widespread harm around the world. It is expected that the molecular mechanism of protein–ligand binding can be elucidated to carry out the pest control. Through studies of SnocOBP12–ligand hydrophobic binding and dynamics and responsible amino acid residues identification, we got some promising results. SnocOBP12 had a general and excellent affinity for host plant volatiles, and may be a key protein for S. noctilio to find host plants. Among the many odor molecules that are bound to SnocOBP12, (−)-α-cedrene and (E)-β-farnesene from host plants and (−)-globuol from the symbiotic fungi of Sirex noctilio stood out and formed highly stable complexes with SnocOBP12. By the molecular mechanics Poisson–Boltzmann surface area (MM-PBSA) method, the calculated free binding energy of the three complexes was −30.572 ± 0.101 kcal/mol, −28.349 ± 0.119 kcal/mol and −25.244 ± 0.152 kcal/mol, respectively. It was found that the van der Waals energy contributed to the stability of the complexes. Some key amino acid residues were also found: LEU74 and TYR109 were very important for SnocOBP12 to stably bind (−)-α-cedrene, while for (E)-β-farnesene, ILE6, MET10, and LEU74 were very important for the stable binding system. We discovered three potential ligands and analyzed the interaction pattern of the protein with them, this paper provides a favorable molecular basis for optimizing the attractant formulation. Investigation of the binding characteristics in the olfactory system at the molecular level is helpful to understand the behavior of S. noctilio and develop new methods for more effective and environmentally friendly pest control.

A top-down strategy for amorphization of hydroxyl compounds for electrocatalytic oxygen evolution

Amorphous materials have attracted increasing attention in diverse fields due to their unique properties, yet their controllable fabrications still remain great challenges. Here, we demonstrate a top-down strategy for the fabrications of amorphous oxides through the amorphization of hydroxides. The versatility of this strategy has been validated by the amorphizations of unitary, binary and ternary hydroxides. Detailed characterizations indicate that the amorphization process is realized by the variation of coordination environment during thermal treatment, where the M–OH octahedral structure in hydroxides evolves to M–O tetrahedral structure in amorphous oxides with the disappearance of the M–M coordination. The optimal amorphous oxide (FeCoSn(OH)6-300) exhibits superior oxygen evolution reaction (OER) activity in alkaline media, where the turnover frequency (TOF) value is 39.4 times higher than that of FeCoSn(OH)6. Moreover, the enhanced OER performance and the amorphization process are investigated with density functional theory (DFT) and molecule dynamics (MD) simulations. The reported top-down fabrication strategy for fabricating amorphous oxides, may further promote fundamental research into and practical applications of amorphous materials for catalysis.

Structural basis of leukotriene B4 receptor 1 activation

Leukotriene B4 receptor 1 (BLT1) plays crucial roles in the acute inflammatory responses and is a valuable target for anti-inflammation treatment, however, the mechanism by which leukotriene B4 (LTB4) activates receptor remains unclear. Here, we report the cryo-electron microscopy (cryo-EM) structure of the LTB4 -bound human BLT1 in complex with a Gi protein in an active conformation at resolution of 2.91 Å. In combination of molecule dynamics (MD) simulation, docking and site-directed mutagenesis, our structure reveals that a hydrogen-bond network of water molecules and key polar residues is the key molecular determinant for LTB4 binding. We also find that the displacement of residues M1013.36 and I2717.39 to the center of receptor, which unlock the ion lock of the lower part of pocket, is the key mechanism of receptor activation. In addition, we reveal a binding site of phosphatidylinositol (PI) and discover that the widely open ligand binding pocket may contribute the lack of specificity and efficacy for current BLT1-targeting drug design. Taken together, our structural analysis provides a scaffold for understanding BLT1 activation and a rational basis for designing anti-leukotriene drugs.

Reactive scattering of water group ions on ice surfaces with relevance to Saturn's icy moons

Collisions of hyperthermal water group ions with ices are known to occur in astrophysical environments, for example, solar wind-comet interactions and moon-magnetosphere interactions (at Saturn and Jupiter), yet their effect on surface and gaseous composition is little understood. Here, we report molecular dynamics simulations of hyperthermal water-group molecules impacting water-ice surfaces using the ReaxFF reactive force fields to describe bond breaking and forming processes dynamically during the reactive collision events. Simulation conditions are chosen for relevance to Saturn's moons Dione and Rhea. At impact velocities of 10–35 kms−1 (8 to 102 eV for O), we find that water group projectiles undergo Eley-Rideal reactions with the ice surface to form O2, HO2, and H2O2. At a 45o angle of incidence the OO bonded products tend to embed within a few molecular layers of the surface. Smaller angles of incidence lead to formation of some molecular oxygen that promptly rebounds from the surface with ~3 eV kinetic energy. Impact velocity, angle of incidence, and hydrogenation of the impactor strongly influence O2 formation, with the yield peaking at 19% for atomic oxygen impactors at 20 kms−1. Notably, this reaction is relatively temperature independent and proceeds in hydrogen rich pristine ice, where radiolysis is hindered. This mechanism for O2 production from low energy impacts may contribute to O2 exospheres at Saturn and Jupiter's icy moons, where hyperthermal ion fluxes are large.

MOF-VR: A Virtual Reality Program for Performing and Visualizing Immersive Molecular Dynamics Simulations of Guest Molecules in Metal-Organic Frameworks.

Molecular dynamics simulations are useful to study diffusion of guest molecules in metal-organic frameworks. The interpretation of the generated three-dimensional trajectories is often difficult, because most visualization tools only allow two-dimensional projections. To facilitate interpretation, we present MOF-VR: a virtual reality program for performing interactive molecular dynamics simulations in metal-organic frameworks and visualizing atomic or molecular trajectories. MOF-VR consists of three subroutines: a construction routine to create hypothetical metal-organic frameworks by hand, a molecular dynamics suite, and a trajectory visualizer. To the best of our knowledge, MOF-VR is the first virtual reality program that allows hypothetical metal-organic frameworks to be constructed and tested in molecular dynamics simulations of guest molecules. We further show that MOF-VR is capable of performing state-of-the-art molecular dynamics simulations of guest molecules in rigid metal-organic frameworks in virtual reality and provides reliable simulation results.

Molecule Dynamics Simulation of the Effect of Oxidative Aging on Properties of Nitrile Rubber.

The effects of oxidative aging on the static and dynamic properties of nitrile rubber at the molecular scale were investigated by molecular dynamics simulation. The aged nitrile rubber models were constructed by introducing hydroxyl groups and carbonyl groups into rubber molecular chains to mimic oxidative aging. The static and dynamic properties of the unaged and aged nitrile rubber under different conditions were evaluated by mean square displacement, self-diffusion coefficients, hydrogen bond, fractional free volume, radial distribution function, cohesive energy density and solubility parameter. The results show that the elevated temperature intensified significantly the mobility of rubber molecular chains and fractional free volume, while the compressive strain displayed the opposite effect resulting in packing and rearrangement of rubber chains. The introduction of hydroxyl groups and carbonyl groups enhanced the polarity, intermolecular interactions, the volume and rigidity of molecular chains, implying weaker mobility of molecular chains as compared to unaged models. The compressive strain and oxidative aging both decreased the fractional free volume, which inhibited gaseous and liquid diffusion into the rubber materials, and slowed down the oxidative aging rate. This study provides insights to better understand the effect of molecular changes due to oxidative aging on the structural and dynamic properties of rubber materials at the molecular level.

Montelukast is a dual-purpose inhibitor of SARS-CoV-2 infection and virus-induced IL-6 expression identified by structure-based drug repurposing

Drug-repurposing has been instrumental to identify drugs preventing SARS-CoV-2 replication or attenuating the disease course of COVID-19. Here, we identify through structure-based drug-repurposing a dual-purpose inhibitor of SARS-CoV-2 infection and of IL-6 production by immune cells. We created a computational structure model of the receptor binding domain (RBD) of the SARS-CoV-2 spike 1 protein, and used this model for insilico screening against a library of 6171 molecularly defined binding-sites from drug molecules. Molecular dynamics simulation of candidate molecules with high RBD binding-scores in docking analysis predicted montelukast, an antagonist of the cysteinyl-leukotriene-receptor, to disturb the RBD structure, and infection experiments demonstrated inhibition of SARS-CoV-2 infection, although montelukast binding was outside the ACE2-binding site. Molecular dynamics simulation of SARS-CoV-2 variant RBDs correctly predicted interference of montelukast with infection by the beta but not the more infectious alpha variant. With distinct binding sites for RBD and the leukotriene receptor, montelukast also prevented SARS-CoV-2-induced IL-6 release from immune cells. The inhibition of SARS-CoV-2 infection through a molecule binding distal to the ACE-binding site of the RBD points towards an allosteric mechanism that is not conserved in the more infectious alpha and delta SARS-CoV-2 variants.

A chemical dynamics study of the reaction of the methylidyne radical (CH, X2Π) with dimethylacetylene (CH3CCCH3, X1A1g).

The gas-phase reaction of the methylidyne (CH; X2Π) radical with dimethylacetylene (CH3CCCH3; X1A1g) was studied at a collision energy of 20.6 kJ mol-1 under single collision conditions with experimental results merged with ab initio calculations of the potential energy surface (PES) and ab initio molecule dynamics (AIMD) simulations. The crossed molecular beam experiment reveals that the reaction proceeds barrierless via indirect scattering dynamics through long-lived C5H7 reaction intermediate(s) ultimately dissociating to C5H6 isomers along with atomic hydrogen with atomic hydrogen predominantly released from the methyl groups as verified by replacing the methylidyne with the D1-methylidyne reactant. AIMD simulations reveal that the reaction dynamics are statistical leading predominantly to p28 (1-methyl-3-methylenecyclopropene, 13%) and p8 (1-penten-3-yne, 81%) plus atomic hydrogen with a significant amount of available energy being channeled into the internal excitation of the polyatomic reaction products. The dynamics are controlled by addition to the carbon-carbon triple bond with the reaction intermediates eventually eliminating a hydrogen atom from the methyl groups of the dimethylacetylene reactant forming 1-methyl-3-methylenecyclopropene (p28). The dominating pathways reveal an unexpected insertion of methylidyne into one of the six carbon-hydrogen single bonds of the methyl groups of dimethylacetylene leading to the acyclic intermediate, which then decomposes to 1-penten-3-yne (p8). Therefore, the methyl groups of dimethylacetylene effectively 'screen' the carbon-carbon triple bond from being attacked by addition thus directing the dynamics to an insertion process as seen exclusively in the reaction of methylidyne with ethane (C2H6) forming propylene (CH3C2H3). Therefore, driven by the screening of the triple bond, one propynyl moiety (CH3CC) acts in four out of five trajectories as a spectator thus driving an unexpected, but dominating chemistry in analogy to the methylidyne - ethane system.

Long-lasting antifogging mechanism for large-aperture optical surface in low-pressure air plasma in-situ treated

In this article, the long-lasting antifogging capability of large-aperture optical components was obtained by the in-situ plasma treatment. Water contact angle and surface free energy were used to study the overall antifogging evolution of optical components in the air. The optical performance, including laser-induced damage threshold and surface morphology, were discussed after plasma cleaning. Elements contents and functional groups information were analyzed by X-ray photoelectron spectroscopy detection as a reference to simulation results. In molecule dynamics simulations, the substrates of fused quartz were modified by linking various functional groups (-H, –OH, –CHO, –COOH, –NH2) to simulate the surface of optical components after plasma treatment at a microscopic level. Experimental results showed that the surface of the optical components (fused quartz, sol-gel antireflection film, multilayer dielectric film) treated by plasma had a good antifogging effect, which can be maintained for 300 min. The surface wettability of optical components was improved significantly after plasma treatment, which was supported mainly by the polar components in the surface free energy. Besides, The optical performance of the components was enhanced while the surface structure was barely damaged. According to simulation results, it was found that –CHO, –COOH, and –NH2 played a dominant role in improving the hydrophilicity of optical components, compared with -H, –OH. The hydrophilic surfaces after plasma modification were obtained because more hydrogen bonds were generated between the surface functional groups and the water molecules. The above research provides a new method and a theoretical basis for improving the long-lasting antifogging for large-aperture optical components.

Metal–Organic Frameworks‐Based Fabry−Pérot Cavity Encapsulated TiO2 Nanoparticles for Selective Chemical Sensing

AbstractThis paper reports a Fabry−Pérot (F–P) cavity constructed by metal–organic frameworks (MOFs) encapsulated with TiO2 nanoparticles that can achieve selective sensing of chemicals. The MOFs‐based F–P cavity is fabricated by sequentially spray‐coating TiO2 in HKUST‐1 thin films through a layer‐by‐layer deposition strategy. The bandwidth of the cavity is tuned over a broad range by adjusting the thickness and refractive index of the HKUST‐1⊃TiO2 thin films with controllable TiO2 size and concentration. Selective sensing of chemical vapors is demonstrated on the HKUST‐1⊃TiO2 cavities which are attributed to enhanced interaction between hydroxyl groups on the surface of TiO2 and the specific oxygen‐containing analytes. In addition, molecule dynamics simulation and infrared absorption spectrum characterization are conducted to elucidate the mechanism of enhanced sensing properties. Homogeneous encapsulation of functional guest pieces with smaller sizes in MOF films contributes to specific physical–chemical properties that benefit their device applications in optical communication and chemical sensing.