Synthesis of Dihydrobenzofuro[3,2-b]chromenes as a potential 3CLpro inhibitors of SARS-CoV-2: A molecular docking and dynamics simulation study

The recent emergence of pandemic of coronavirus (COVID‐19) caused by SARS‐CoV‐2 has raised significant global health concerns. More importantly, there is no specific therapeutics currently available to combat against this deadly infection. The enzyme 3‐chymotrypsin‐like cysteine protease (3CLpro) is known to be essential for viral life cycle as it controls the coronavirus replication. 3CLpro could be a potential drug target as established before in the case of severe acute respiratory syndrome coronavirus (SARS‐CoV) and Middle East respiratory syndrome coronavirus (MERS‐CoV). In the current study, we wanted to explore the potential of fused flavonoids as 3CLpro inhibitors. Fused flavonoids (5a,10a‐dihydro‐11H‐benzofuro[3,2‐b]chromene) are unexplored for their potential bioactivities due to their low natural occurrences. Their synthetic congeners are also rare due to unavailability of general synthetic methodology. Here we designed a simple strategy to synthesize 5a,10a‐dihydro‐11H‐benzofuro[3,2‐b]chromene skeleton and it's four novel derivatives. Our structural bioinformatics study clearly shows excellent potential of the synthesized compounds in comparison to experimentally validated inhibitor N3. Moreover, in‐silico ADMET study displays excellent druggability and extremely low level of toxicity of the synthesized molecules. Further, for better understanding, the molecular dynamic approach was implemented to study the change in dynamicity after the compounds bind to the protein. A detailed investigation through clustering analysis and distance calculation gave us sound comprehensive data about their molecular interaction. In summary, we anticipate that the currently synthesized molecules could not only be a potential set of inhibitors against 3CLpro but also the insights acquired from the current study would be instrumental in further developing novel natural flavonoid based anti‐COVID therapeutic spectrums.

Metal-Molecule-Metal Junctions on Self-Assembled Monolayers Made with Selective Electroless Deposition

Electronic transport through molecular-scale devices has been studied extensively for its extraordinary dimension superiority. Assembling such devices into large-scale functional circuits is crucial since the molecular tunnel junctions must be reliable, stable and reproducible during technological applications. In ideal circumstances, the device architecture should be designed such that the metal-molecule-metal (MMM) junctions can be analyzed by the more sensitive four point probe system. In this paper, we expound a delicate method to manufacture molecular junctions, which show excellent stability and reproducibility with high yields (>91 per cent). We form self-assembled monolayers (SAMs) on conductive Au thin film by microcontact printing and then generate robust covalently bound metal thin film electrodes on top of the SAMs by selective electroless deposition. Following MMM junction formation, a photoresist is coated and wells are opened on each feature by lithography. Then, Au thin film, as a permanent top electrode, is deposited into the photolithographically defined well. Conductivity analyzations were carried out on the 50 μm square junctions by the four point probe measurement, and the results showed reproducible tunneling I-V characteristics. This method reveals an approach not only offering a unique vehicle to investigate the electrical properties of molecule ensembles in MMMs, but also making a significant step toward MMM applications at the device level.

A polymerizable supramolecular approach for the fabrication of patterned magnetic nanoparticles

A straightforward method for the preparation of patterned magnetite nanoparticles (MNPs) was developed. The polymerizable supramolecular approach afforded finely patterned MNPs on a solid substrate after a sequential UV-irradiation-wet etching-calcination process with an MNP-embedded diacetylene film.

Tuning deposition of magnetic metallic nanoparticles from periodic pattern to thin film entrainment by dip coating method

In this work, we report on the self-assembly of bimetallic CoFe carbide magnetic nanoparticles (MNPs) stabilized by a mixture of long chain surfactants. A dedicated setup, coupling dip coating and sputtering chamber, enables control of the self-assembly of MNPs from regular stripe to continuous thin films under inert atmosphere. The effects of experimental parameters, MNP concentration, withdrawal speed, amount, and nature of surfactants, as well as the surface state of the substrates are discussed. Magnetic measurements revealed that the assembled particles were not oxidized, confirming the high potentiality of our approach for the controlled deposition of highly sensitive MNPs.

Dip-coating deposition on chemically patterned surfaces: a mechanistic analysis and comparison with topographically patterned surfaces

Chemically patterned surfaces containing hydrophilic features on a hydrophobic background have been used by a number of groups to deposit arrays of particles/crystals/substances by dip-coating deposition. In this technique, a substrate is simply withdrawn from a solution (or dispersion) of the desired substance, the solution dewets from the hydrophobic region and wets the hydrophilic features, and the particles/crystals/substances deposit on the hydrophilic features after solvent evaporation. An apparently similar approach, recently described by several groups, involves dip-coating deposition of substances from solutions onto hydrophobic topographic features (arrays of posts on superhydrophobic surfaces) that are separated by air. We report results of dip-coating deposition using chemically patterned surfaces and compare them directly with results from post-containing superhydrophobic surfaces. This comparison involves the analysis of events at receding three-phase contact lines; these events differ significantly in the two approaches with the key difference being tensile (normal to the surface) versus sessile (parallel to the surface) capillary bridge failure. Tensile failure occurs with the post-containing superhydrophobic surfaces and sessile failure with chemically patterned surfaces. The solvent evaporation stages of the processes, that occur subsequent to the capillary bridge failure events, also vary significantly in the two approaches and depend on the receding contact angles of the hydrophobic post tops and the hydrophilic chemically patterned features. These differences, as the adjectives suggest, are pronounced. Controlling the evaporation rate (adjusting the vaporization/condensation equilibrium) by raising the partial pressure of the solvent is identified as a useful variable for chemically patterned surfaces.

Airbrushed nickel nanoparticles for large-area growth of vertically aligned carbon nanofibers on metal (Al, Cu, Ti) surfaces

Vertically aligned carbon nanofibers (VACNFs) were grown by plasma-enhanced chemical vapor deposition (PECVD) using Ni nanoparticle (NP) catalysts that were deposited by airbrushing onto Si, Al, Cu, and Ti substrates. Airbrushing is a simple method for depositing catalyst NPs over large areas that is compatible with roll-to-roll processing. The distribution and morphology of VACNFs are affected by the airbrushing parameters and the composition of the metal foil. Highly concentrated Ni NPs in heptane give more uniform distributions than pentane and hexanes, resulting in more uniform coverage of VACNFs. For VACNF growth on metal foils, Si micropowder was added as a precursor for Si-enriched coatings formed in situ on the VACNFs that impart mechanical rigidity. Interactions between the catalyst NPs and the metal substrates impart control over the VACNF morphology. Growth of carbon nanostructures on Cu is particularly noteworthy because the miscibility of Ni with Cu poses challenges for VACNF growth, and carbon nanostructures anchored to Cu substrates are desired as anode materials for Li-ion batteries and for thermal interface materials.