Quantum-Chemical Quasi-Docking for Molecular Dynamics Calculations

The quantum quasi-docking procedure is used to compare the docking accuracies of two quantum-chemical semiempirical methods, namely, PM6-D3H4X and PM7. Quantum quasi-docking is an approximation to quantum docking. In quantum docking, it is necessary to search directly for the global minimum of the energy of the protein-ligand complex calculated by the quantum-chemical method. In quantum quasi-docking, firstly, we look for a wide spectrum of low-energy minima, calculated using the MMFF94 force field, and secondly, we recalculate the energies of all these minima using the quantum-chemical method, and among these recalculated energies we determine the lowest energy and the corresponding ligand position. Both PM6-D3H4X and PM7 are novel methods that describe well-dispersion interactions, hydrogen and halogen bonds. The PM6-D3H4X and PM7 methods are used with the COSMO implicit solvent model as it is implemented in the MOPAC program. The comparison is made for 25 high quality protein-ligand complexes. Firstly, the docking positioning accuracies have been compared, and we demonstrated that PM7+COSMO provides better positioning accuracy than PM6-D3H4X. Secondly, we found that PM7+COSMO demonstrates a much higher correlation between the calculated and measured protein–ligand binding enthalpies than PM6-D3H4X. For future quantum docking PM7+COSMO is preferable, but the COSMO model must be improved.

Future Clinical Application of β-galactosidase Stabilized by Magnesium oxide Nanoparticles

The present study demonstrates the application of freshly prepared neem leaf extract as a reducing agent for synthesizing magnesium oxide nanoparticles (MgO-NPs). In silico interaction of Aspergillus oryzae β-galactosidase with MgO-NPs was observed by using molecular docking program Dock v.6.5 while the visual analyses and illustration of protein–ligand complex were investigated by utilizing chimera v.1.6.2 and PyMOL v.1.3 softwares. The prepared nanomatrix provided 83% immobilization yield, and broadened the biocatalytic activity of immobilized β-galactosidase at higher pH and temperature ranges. Immobilized β-galactosidase exhibited greater activity even at 5.0% galactose concentration as compared to the soluble enzyme under similar experimental conditions. Hence, the use of green nanotechnology makes the process inexpensive, and therefore, immobilization of these enzymes on such nanoparticles can help to recover the enzyme, which ultimately decreases the cost of process.

Computational Investigations on Interactions Between DNA and Flavonols

Today, the main task of researchers is to study and develop drugs that are less toxic and have lesser side effects. The principal motive of this research is to study and analyze the interaction between naturally active compounds flavonoids with biomolecule DNA. Since the interaction between DNA and ligand is essential in drug designing, this study will provide a good base for further research and development of less toxic and more efficient drugs for various diseases. The selected compounds for this study are Kaempferide, Kaempferol, Morin, and Rutin. They all fall into the category ‘flavonols’ of flavonoids. Computational methods are implemented for theoretical drug designing. These are molecular optimization, molecular docking, and molecular dynamics. Computational results are compared with experimental data from previous studies. Molecular docking gives the most preferred orientation of ligands within DNA, and Molecular Dynamics provides the details about the DNA-ligand complex with respect to time. Free energy calculations were also performed by implementing MMPBSA and MMGBSA calculations.

Detection to trace aluminum ion of pharmaceutical wastewater using synthesis of Schiff-based chemosensor

Background: The aim of this research was to develop a fluorogenic sensor for Al3+ions, which have been identified as a possible food and drinking water pollutant by the WHO and considered to be harmful to human health. Methods: The sensing mechanism was based on excited-state intramolecular proton transfer, with the intramolecular rotation restriction occurring after binding with the analyte. The probe attaches Al3+selectively and emits strong emission in 4:1 H2 O/MeOH (v/v) solution while irradiated at 400 nm in the presence of a wide number of cations, acting as a "turn-on" fluorescence chemosensor. The range of detection for Al3+is 3.3 nM (3 method), which is more than 200 times more responsive than the WHO suggested limit of 7.4 mM (3σ method). Mass spectra, job plot, and Benesi-Hildebrand plot were used to determine the formation of the 1:1 metal-to-ligand complex. Results: Aluminum (Al) ion content in effluent obtained from the pharmaceutical sector is 0.381 mM, which is a trace amount. A separate in vitro experiment indicates that the probe can precisely perceive Al3+ions in a cell line. The sensor-based method is developed to detect 3.3 nM of Al3+ions, which is significantly less than the WHO max. Conclusion: The probe to detect Al3+ions in live cells. HL becomes a flexible sensor for recognizing intracellular Al3+in human liver cancer cell line Hep G2 and human lung fibroblast cell lines by fluorescence cell imaging procedures, and the probe’s non-toxicity has been proven by MTT tests up to 100M.

PDBrt: A free database of complexes with measured drug-target residence time

Background: Difficulties in translating the in vitro potency determined by cellular assays into in vivo efficacy in living organisms complicates the design and development of drugs. However, the residence time of a drug in its molecular target is becoming a key parameter in the design and optimization of new drugs, as recent studies show that residence time can reliably predict drug efficacy in vivo. Experimental approaches to binding kinetics and target ligand complex solutions are currently available, but known bioinformatics databases do not usually report information about the ligand residence time in its molecular target. Methods: To extend existing databases we developed the Protein Data Bank (PDB) residence time database (PDBrt) which reports drug residence time. The database is implemented as an open access web-based tool. The front end uses Bootstrap with Hypertext Markup Language (HTML), jQuery for the interface and 3Dmol.js to visualize the complexes. The server-side code uses Python web application framework, Django Rest Framework and backend database PostgreSQL. Results: The PDBrt database is a free, non-commercial repository for 3D protein-ligand complex data, including the measured ligand residence time inside the binding pocket of the specific biological macromolecules as deposited in The Protein Data Bank. The PDBrt database contains information about both the protein and the ligand separately, as well as the protein-ligand complex, binding kinetics, and time of the ligand residence inside the protein binding site. Availability: https://pdbrt.polsl.pl

A comprehensive in silico investigation into the nsSNPs of Drd2 gene predicts significant functional consequences in dopamine signaling and pharmacotherapy

DRD2 is a neuronal cell surface protein involved in brain development and function. Variations in the Drd2 gene have clinical significance since DRD2 is a pharmacotherapeutic target for treating psychiatric disorders like ADHD and schizophrenia. Despite numerous studies on the disease association of single nucleotide polymorphisms (SNPs) in the intronic regions, investigation into the coding regions is surprisingly limited. In this study, we aimed at identifying potential functionally and pharmaco-therapeutically deleterious non-synonymous SNPs of Drd2. A wide array of bioinformatics tools was used to evaluate the impact of nsSNPs on protein structure and functionality. Out of 260 nsSNPs retrieved from the dbSNP database, initially 9 were predicted as deleterious by 15 tools. Upon further assessment of their domain association, conservation profile, homology models and inter-atomic interaction, the mutant F389V was considered as the most impactful. In-depth analysis of F389V through Molecular Docking and Dynamics Simulation revealed a decline in affinity for its native agonist dopamine and an increase in affinity for the antipsychotic drug risperidone. Remarkable alterations in binding interactions and stability of the protein–ligand complex in simulated physiological conditions were also noted. These findings will improve our understanding of the consequence of nsSNPs in disease-susceptibility and therapeutic efficacy.

Virtual Screening of Phytochemicals Targeting the Main Protease and Spike Protein of SARS-CoV-2: An In silico Approach

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is an emerging virus responsible for the ongoing Coronavirus Disease 19 (COVID-19) pandemic. Despite the advent of COVID-19 vaccines, pandemic fatigue is still escalating as new SARS-CoV-2 variants emerge and vaccine shortages hit globally. Hence, drug repurposing remains an alternative strategy to combat SARS-CoV-2. For centuries, plants have served as natural reservoirs of pharmacologically active compounds with minimal cytotoxicity and promising antimicrobial and antiviral activities. In this light, the present study was undertaken to virtually screen 33 phytochemicals across various cultivars against the main protease (Mpro) and Spike (S) protein of SARS-CoV-2 using ADME analysis. 31 phytochemicals obeying Lipinski’s rules were subjected to molecular docking using AutoDock Vina. Docking scores were determined by selecting the best conformation of the protein-ligand complex that exhibited the highest affinity. The study identified withanone, licoflavone A, and silibinin to interact with the S protein at the hACE2-binding site with high binding energies. Similarly, myricitrin, withanone, naringenin, licoflavone A, and silibinin exhibited high binding affinities with the substrate-binding pocket of Mpro between the domains I and II. Interestingly, licoflavone A, silibinin, and withanone interacted with both Mpro and S proteins in silico. Further, drug-likeness studies indicated withanone to be the most readily bioavailable phytochemicals among the three shortlisted ligands. Therefore, phytochemicals can be regarded as potential leads for developing inhibitors against this mysterious virus. In vitro investigations are further warranted to prove their antiviral efficacy.

Directed evolution of and structural insights into antibody-mediated disruption of a stable receptor-ligand complex

Antibody drugs exert therapeutic effects via a range of mechanisms, including competitive inhibition, allosteric modulation, and immune effector mechanisms. Facilitated dissociation is an additional mechanism where antibody-mediated “disruption” of stable high-affinity macromolecular complexes can potentially enhance therapeutic efficacy. However, this mechanism is not well understood or utilized therapeutically. Here, we investigate and engineer the weak disruptive activity of an existing therapeutic antibody, omalizumab, which targets IgE antibodies to block the allergic response. We develop a yeast display approach to select for and engineer antibody disruptive efficiency and generate potent omalizumab variants that dissociate receptor-bound IgE. We determine a low resolution cryo-EM structure of a transient disruption intermediate containing the IgE-Fc, its partially dissociated receptor and an antibody inhibitor. Our results provide a conceptual framework for engineering disruptive inhibitors for other targets, insights into the failure in clinical trials of the previous high affinity omalizumab HAE variant and anti-IgE antibodies that safely and rapidly disarm allergic effector cells.

Molecular Dynamics Simulation of Bioactive Compounds Against Six Protein Target of Sars-Cov-2 As Covid-19 Antivirus Candidates

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is the virus that causes Coronavirus 2019 (COVID-19). To date, there has been no proven effective drug for the treatment or prevention of COVID-19. A study on developing inhibitors for this virus was performed using molecular dynamics simulation. 3CL-Pro, PL-Pro, Helicase, N, E, and M protein were used as protein targets. This study aimed to determine the stability of the selected protein-ligand complex through molecular dynamics simulation by Amber20 to propose bioactive compounds from natural products that have potential as a drug for COVID-19. Based on our previous study, the best value of free binding energy and protein-ligand interactions of the candidate compounds are obtained for each target protein through molecular docking. Corilagin (-14.42 kcal/mol), Scutellarein 7-rutinoside (-13.2 kcal/mol), Genistein 7-O-glucuronide (-10.52 kcal/mol), Biflavonoid-flavone base + 3O (-11.88 and -9.61 kcal/mol), and Enoxolone (-6.96 kcal/mol) has the best free energy value at each protein target. In molecular dynamics simulation, the 3CL-Pro-Corilagin complex was the most stable compared to other complexes, so that it was the most recommended compound. Further research is needed to test the selected ligand activity, which has the lowest free energy value of the six target proteins.

New Approaches to Assess Mechanisms of Action of Selective Vitamin D Analogues

Recent studies of transcription have revealed an advanced set of overarching principles that govern vitamin D action on a genome-wide scale. These tenets of vitamin D transcription have emerged as a result of the application of now well-established techniques of chromatin immunoprecipitation coupled to next-generation DNA sequencing that have now been linked directly to CRISPR-Cas9 genomic editing in culture cells and in mouse tissues in vivo. Accordingly, these techniques have established that the vitamin D hormone modulates sets of cell-type specific genes via an initial action that involves rapid binding of the VDR–ligand complex to multiple enhancer elements at open chromatin sites that drive the expression of individual genes. Importantly, a sequential set of downstream events follows this initial binding that results in rapid histone acetylation at these sites, the recruitment of additional histone modifiers across the gene locus, and in many cases, the appearance of H3K36me3 and RNA polymerase II across gene bodies. The measured recruitment of these factors and/or activities and their presence at specific regions in the gene locus correlate with the emerging presence of cognate transcripts, thereby highlighting sequential molecular events that occur during activation of most genes both in vitro and in vivo. These features provide a novel approach to the study of vitamin D analogs and their actions in vivo and suggest that they can be used for synthetic compound evaluation and to select for novel tissue- and gene-specific features. This may be particularly useful for ligand activation of nuclear receptors given the targeting of these factors directly to genetic sites in the nucleus.