COVID-19, since emerged in Wuhan, China, has been a major concern due to its high infection rate, leaving more than one million infected people around the world. Huge number of studies tried to reveal the structure of the SARS-CoV-2 compared to the SARS-CoV-1, in order to suppress this high infection rate. Some of these studies showed that the mutations in the SARS-CoV-1 Spike protein might be responsible for its higher affinity to the ACE2 human cell receptor. In this work, we used molecular dynamics simulations and Monte Carlo sampling to compare the binding affinities of the spike proteins of SARS-CoV and SARS-CoV-2 to the ACE2. We found that the SARS-CoV-2 binds to ACE2 stronger than SARS-CoV by 7 kcal/mol, due to enhanced electrostatic interactions. The major contributions to the electrostatic binding energies are resulting from the salt-bridges formed between R426 and ACE2-E329 in case of SARS-CoV and K417 and ACE2-D30 for SARS-CoV2. In addition, there is no significant contribution from a single mutant to the binding energies. However, these mutations induce sophisticated structural changes that enhance the binding energies. Our results also indicate that the SARS-CoV-2 is unlikely a lab engineered virus.

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Lignin's availability in large amounts from industrial black liquor as waste from the paper industry is still a problem. On the other hand, its utilization potentials as a green low-cost adsorbent for the effective removal of toxic organic dye from industrial wastewater has become a topic of great interest but remains quite challenging. In this sense, this work aimed to evaluate the feasibility of removing the reactive green dye (RGD) onto the functionalized lignin-based adsorbent (FLA) by the acidic method. The kinetic study suggested the adsorption process confirmed to a pseudo-second-order-kinetic and intra-particle diffusion models. Also, the isotherm results showed that the FLA exhibited multi-layer adsorption. Meanwhile, the results of FTIR and SEM showed that the RG-19 adsorption mechanisms were electrostatic interaction, hydrogen bonding, π-π stacking, and physical adsorption. Thermodynamic parameters were also evaluated and their values indicated that adsorption of RG-19 onto FLA is an exothermic process and spontaneous in nature. As a renewable, low-cost, and natural biomass material, FLA has the potential to be used as a promising sustainable and economic application of biomass and will inspire more scholars to investigate solutions to the problem of contaminated water resources.

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