Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was found to be a severe threat to global public health in late 2019. Nevertheless, no approved medicines have been found to inhibit the virus effectively. Anti-malarial and antiviral medicines have been reported to target the SARS-CoV-2 virus. This paper chose eight natural eucalyptus compounds to study their binding interactions with the SARS-CoV-2 main protease (Mpro) to assess their potential for becoming herbal drugs for the new SARS-CoV-2 infection virus. In-silico methods such as molecular docking, molecular dynamics (MD) simulations, and Molecular Mechanics Poisson Boltzmann Surface Area (MM/PBSA) analysis were used to examine interactions at the atomistic level. The results of molecular docking indicate that Mpro has good binding energy for all compounds studied. Three docked compounds, α-gurjunene, aromadendrene, and allo-aromadendrene, with highest binding energies of −7.34 kcal/mol (−30.75 kJ/mol), −7.23 kcal/mol (−30.25 kJ/mol), and −7.17 kcal/mol (−29.99 kJ/mol) respectively, were simulated with GROningen MAchine for Chemical Simulations (GROMACS) to measure the molecular interactions between Mpro and inhibitors in detail. Our MD simulation results show that α-gurjunene has the strongest binding energy of −20.37 kcal/mol (−85.21 kJ/mol), followed by aromadendrene with −18.99 kcal/mol (−79.45 kJ/mol), and finally allo-aromadendrene with −17.91 kcal/mol (−74.95 kJ/mol). The findings indicate that eucalyptus may be used to inhibit the Mpro enzyme as a drug candidate. This is the first computational analysis that gives an insight into the potential role of structural flexibility during interactions with eucalyptus compounds. It also sheds light on the structural design of new herbal medicinal products against Mpro.

Two-dimensional (2D) materials and their heterostructures are useful in electronic applications, especially with the drive towards more and more miniaturization. Using first-principles calculations, we study the structural and electronic properties of some transition metal dichalcogenides and diselenides (MoS₂, MoSe₂, WS₂, WSe₂). Our studies were based on density functional theory (DFT) as implemented in the Quantum ESPRESSO package. 2D layered materials present a huge challenge for DFT as a result of interlayer van der Waals (vdW) interaction which is absent from the typical DFT exchange-correlation functional. In order to account for the van der Waals interactions between layers, we applied the semi-empirical DFT-D2 method of Grimme and the revised Vydrov-Van Voorhis non-local correlation functional (rVV10). We show that the two approaches give similar structural properties. We also found that the size of the electronic band gap of these structures changes with respect to the number of layers stacked.

We investigate the dynamics of the spatial entanglement between two initially independent walkers that perform discrete-time quantum walk with respect to symmetric and anti-symmetric initial coin states. By considering the symmetry associated with the setting and post-selecting the states of the two coins accordingly, we show that, for the anti-symmetric initial coin state, the entanglement corresponding to all the anti-symmetric results are always constant, while that corresponding to the symmetric result is underdamped-like with period of oscillation ($T$) being inversely proportional to the coin operator parameter ($\theta$). The results are the opposite way around for the case of symmetric initial coin states. We also discover that the underdamped-like behaviour of the spatial entanglement show up in the cases of both initial coin states when the post-selected results have no symmetry. Our findings reveal some interesting aspects of symmetry and entanglement dynamics in quantum walk, which may be useful for applications in quantum communication and other quantum technology.