The Molecular Basis of the Effect of Temperature on the Structure and Function of SARS-CoV-2 Spike Protein.

The remarkable rise of the current COVID-19 pandemic to every part of the globe has raised key concerns for the current public healthcare system. The spike (S) protein of SARS-CoV-2 shows an important part in the cell membrane fusion and receptor recognition. It is a key target for vaccine production. Several researchers studied the nature of this protein under various environmental conditions. In this work, we applied molecular modeling and extensive molecular dynamics simulation approaches at 0°C (273.15 K), 20°C (293.15 K), 40°C (313.15 K), and 60°C (333.15 K) to study the detailed conformational alterations in the SARS-CoV-2 S protein. Our aim is to understand the influence of temperatures on the structure, function, and dynamics of the S protein of SARS-CoV-2. The structural deviations, and atomic and residual fluctuations were least at low (0°C) and high (60°C) temperature. Even the internal residues of the SARS-CoV-2 S protein are not accessible to solvent at high temperature. Furthermore, there was no unfolding of SARS-CoV-2 spike S reported at higher temperature. The most stable conformations of the SARS-CoV-2 S protein were reported at 20°C, but the free energy minimum region of the SARS-CoV-2 S protein was sharper at 40°C than other temperatures. Our findings revealed that higher temperatures have little or no influence on the stability and folding of the SARS-CoV-2 S protein.

Systems analysis shows that thermodynamic physiological and pharmacological fundamentals drive COVID-19 and response to treatment.

Why a systems analysis view of this pandemic? The current pandemic has inflicted almost unimaginable grief, sorrow, loss, and terror at a global scale. One of the great ironies with the COVID-19 pandemic, particularly early on, is counter intuitive. The speed at which specialized basic and clinical sciences described the details of the damage to humans in COVID-19 disease has been impressive. Equally, the development of vaccines in an amazingly short time interval has been extraordinary. However, what has been less well understood has been the fundamental elements that underpin the progression of COVID-19 in an individual and in populations. We have used systems analysis approaches with human physiology and pharmacology to explore the fundamental underpinnings of COVID-19 disease. Pharmacology powerfully captures the thermodynamic characteristics of molecular binding with an exogenous entity such as a virus and its consequences on the living processes well described by human physiology. Thus, we have documented the passage of SARS-CoV-2 from infection of a single cell to species jump, to tropism, variant emergence and widespread population infection. During the course of this review, the recurrent observation was the efficiency and simplicity of one critical function of this virus. The lethality of SARS-CoV-2 is due primarily to its ability to possess and use a variable surface for binding to a specific human target with high affinity. This binding liberates Gibbs free energy (GFE) such that it satisfies the criteria for thermodynamic spontaneity. Its binding is the prelude to human host cellular entry and replication by the appropriation of host cell constituent molecules that have been produced with a prior energy investment by the host cell. It is also a binding that permits viral tropism to lead to high levels of distribution across populations with newly formed virions. This thermodynamic spontaneity is repeated endlessly as infection of a single host cell spreads to bystander cells, to tissues, to humans in close proximity and then to global populations. The principal antagonism of this process comes from SARS-CoV-2 itself, with its relentless changing of its viral surface configuration, associated with the inevitable emergence of variants better configured to resist immune sequestration and importantly with a greater affinity for the host target and higher infectivity. The great value of this physiological and pharmacological perspective is that it reveals the fundamental thermodynamic underpinnings of SARS-CoV-2 infection.

Identification of homologous human miRNAs as antivirals towards COVID-19 genome.

The COVID-19 fatality rate is ~57% worldwide. The investigation of possible antiviral therapy using host microRNA (miRNA) to inhibit viral replication and transmission is the need of the hour. Computational techniques were used to predict the hairpin precursor miRNA (pre-miRNAs) of COVID-19 genome with high homology towards human (host) miRNA. Top 21 host miRNAs with >80% homology towards 18 viral pre miRNAs were identified. The Gibbs free energy (ΔG) between host miRNAs and viral pre-miRNAs hybridization resulted in the best 5 host miRNAs having the highest base-pair complementarity. miR-4476 had the strongest binding with viral pre-miRNA (ΔG = -21.8 kcal/mol) due to maximum base pairing in the seed sequence. Pre-miR-651 secondary structure was most stable due to the (1) least minimum free energy (ΔG = -24.4 kcal/mol), energy frequency, and noncanonical base pairing and (2) maximum number of stem base pairing and small loop size. Host miRNAs-viral mRNAs interaction can effectively inhibit viral transmission and replication. Furthermore, miRNAs gene network and gene-ontology studies indicate top 5 host miRNAs interaction with host genes involved in transmembrane-receptor signaling, cell migration, RNA splicing, nervous system formation, and tumor necrosis factor-mediated signaling in respiratory diseases. This study identifies host miRNA/virus pre-miRNAs strong interaction, structural stability, and their gene-network analysis provides strong evidence of host miRNAs as antiviral COVID-19 agents.

Molecular dynamics simulation perception study of the binding affinity performance for main protease of SARS-CoV-2.

Like common cold and flu, SARC-CoV-2 virus spreads by droplets of sneezes or coughs which virus affects people of various age groups. Today, this virus is almost distributed all over the world. Since binding process plays a crucial role between host and receptor, therefore, we studied the molecules intended toward inhibition process through molecular docking and molecular dynamics simulation process. From the molecular docking study, it is noteworthy that remdesivir shows better binding affinity toward the main protease of SARS-CoV2 compared to other studied drugs. Within studied phytochemicals, carnosic acid shows better binding poses toward main protease of SARS-CoV2 among studied phytochemicals. The amino acid residues GLN110 and PHE294 were almost found in all the studied interactions of drugs and phytochemicals with main protease of SARS-CoV-2. Furthermore, the results show a larger contribution of the Van der Waals energies as compared to others like electrostatic energies suggesting that ligands at the binding pocket are predominantly stabilized by hydrophobic interactions. The conformational change during ligand binding was predicted from Gibbs free energy landscape analysis through molecular dynamics simulation. We observed that, there were two main free energy basins for both docked carnosic acid complex and for docked remdesivir complex, only one main free energy basin was found in the global free energy minimum region.Communicated by Ramaswamy H. Sarma.

Analysis of the potential impact of genomic variants in global SARS-CoV-2 genomes on molecular diagnostic assays.

An epidemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causing coronavirus diseases (C0VID-19) initially reported in Wuhan, China has rapidly emerged into a global pandemic affecting millions of people worldwide. Molecular detection of SARS-CoV-2 using reverse transcription polymerase chain reaction (RT-PCR) forms the mainstay in screening, diagnosis and epidemiology of the disease. Since the virus evolves by accumulating base substitutions, mutations in the viral genome could possibly affect the accuracy of RT-PCR-based detection assays. The recent availability of genomes of SARS-CoV-2 isolates motivated us to assess the presence and potential impact of variations in target sites of the oligonucleotide primers and probes used in molecular diagnosis. We catalogued a total of 132 primer or probe sequences from literature and data available in the public domain. Our analysis revealed that a total of 5862 unique genetic variants mapped to at least one of the 132 primer or probe binding sites in the genome. A total of 29 unique variants were present in ≥ 1% of genomes from at least one of the continents (Asia, Africa, Australia, Europe, North America, and South America) that mapped to 36 unique primers or probes binding sites. Similarly, a total of 27 primer or probe binding sites had cumulative variants frequency of ≥ 1% in the global SARS-CoV-2 genomes. These included primers or probes sites which are used worldwide for molecular diagnosis as well as approved by national and international agencies. We also found 286 SARS-CoV-2 genomic regions with low variability at a continuous stretch of ≥ 20bps that could be potentially used for primer designing. This highlights the need for sequencing genomes of emerging pathogens to enable evidence-based policies for development and approval of diagnostics.

Synthesis of exfoliated multilayer graphene and its putative interactions with SARS-CoV-2 virus investigated through computational studies.

Our work investigates the interaction of synthesized graphene with the SARS-CoV-2 virus using molecular docking and molecular dynamics (MD) simulation method. The layer dependent inhibitory effect of graphene nanosheets on spike receptor-binding domain of 6LZG, complexed with host receptor i.e. angiotensin-converting enzyme 2 (ACE2) of SARS-CoV-2 was investigated through computational study. Graphene sample was synthesized using mechanical exfoliation with shear stress and its mechanism of inhibition towards the SARS-CoV-2 virus was explored by molecular docking and molecular dynamics (MD) simulation method. The thermodynamics study for the free binding energy of graphene towards the SARS-CoV-2 virus was analyzed. The binding energy of graphene towards the virus increased with an increasing number of layers. It shows the highest affinity of -17.5 Kcal/mol in molecular docking while ΔGbinding is in the order of -28.01 ± 0.04 5 Kcal/mol for the seven-layers structure. The increase in carbon layers is associated with an increasing number of edge sp3 -type carbon, providing greater curvature, further increase the surface reactivity responsible for high binding efficiency. The MD simulation data reveals the high inhibition efficiency of the synthesized graphene towards SARS-CoV-2 virus which would help to design future in-vitro studies. The graphene system could find potential applications in personal protective equipment and diagnostic kits.Communicated by Ramaswamy H. Sarma.