Interaction of the new inhibitor paxlovid (PF-07321332) and ivermectin with the monomer of the main protease SARS-CoV-2: A volumetric study based on molecular dynamics, elastic networks, classical thermodynamics and SPT

The COVID-19 pandemic has accelerated the study of drugs, most notably ivermectin and more recently Paxlovid (PF-07321332) which is in phase III clinical trials with experimental data showing covalent binding to the viral protease M^pro. Theoretical developments of catalytic site-directed docking support thermodynamically feasible non-covalent binding to M^pro. Here we show that Paxlovid binds non-covalently at regions other than the catalytic sites with energies stronger than reported and at the same binding site as the ivermectin B1a homologue, all through theoretical methodologies, including blind docking. We volumetrically characterize the non-covalent interaction of the ivermectin homologues (avermectins B1a and B1b) and Paxlovid with the mM^pro monomer, through molecular dynamics and scaled particle theory (SPT). Using the fluctuation-dissipation theorem (FDT), we estimated the electric dipole moment fluctuations at the surface of each of complex involved in this study, with similar trends to that observed in the interaction volume. Using fluctuations of the intrinsic volume and the number of flexible fragments of proteins using anisotropic and Gaussian elastic networks (ANM+GNM) suggests the complexes with ivermectin are more dynamic and flexible than the unbound monomer. In contrast, the binding of Paxlovid to mM^pro shows that the mM^pro-PF complex is the least structurally dynamic of all the species measured in this investigation. The results support a differential molecular mechanism of the ivermectin and PF homologues in the mM^pro monomer. Finally, the results showed that Paxlovid despite beingbound in different sites through covalent or non-covalent forms behaves similarly in terms of its structural flexibility and volumetric behaviour.

Computational Analysis of the Silver Nanoparticle-Human Serum Albumin Complex

Drug delivery in excess concentrations and at not-specified sites inside the human body adversely affects the body and gives rise to other diseases. Several methods have been developed to deliver the drugs in required amounts and at specific targets. Nanoparticle-mediated drug delivery is one such approach and has gained success at primary levels. The effect of nanoparticles on the human body needs important apprehension, and it has been unraveled by assessing the protein-nanoparticle interactions. Here, we have measured the impact of silver nanoparticles (AgNPs) on the human serum albumin (HSA) structure and function with the help of all-atom molecular dynamics simulations (MDS). HSA is a transport protein, and any change in the structure may obstruct its function. The post MD analyses showed that the NP interacts with HSA and the conjugated system got stabilized with time evolution of trajectories. The present investigation confirms that the AgNP interacts with HSA without affecting its tertiary and secondary structures and in turn the protein function as well. AgNP application is recommended in transporting conjugated drug molecules as it has no adverse effect on serum proteins. Since HSA is present in the circulatory system, it may open various applications of AgNPs in the biomedical field.