An Experimental and Theoretical Investigation of the Efficacy of Pantoprazole as a Corrosion Inhibitor for Mild Steel in an Acidic Medium

The corrosion behavior of mild steel in a 1 M aqueous sulfuric acid medium in the presence and absence of the drug Pantoprazole was investigated using potentiodynamic polarization and quantum chemical calculations as well as Monte Carlo and molecular dynamic simulations. The potentiodynamic experiments indicated that this molecule, as a result of its adsorption on a mild steel surface, functioned as a mixed inhibitor. The goal of the study was to use theoretical calculations to acquire a better understanding of how inhibition works. The adsorption behavior of the examined compounds on the Fe (1 1 0) surface was calculated using a Monte Carlo simulation. Furthermore, the molecules were studied using density functional theory (DFT), especially the PBE functional, to determine the relationship between the molecular structure and the corrosion inhibition behavior of the chemical under research. The adsorption energies of Pantoprazole (in its three different protonation states) iron were calculated more precisely using molecular mechanics with periodic boundary conditions (PBC). The predicted theoretical parameters were found to be in agreement with the experimental data, which was a considerable help in understanding the corrosion inhibition mechanism displayed by this chemical.

Repurposing FDA-approved Drugs Targeting SARS-CoV2 3CLpro: a study by applying Virtual Screening, Molecular Dynamics, MM-PBSA Calculations and Covalent Docking

Background: Since the end of 2019, the etiologic agent SAR-CoV-2 responsible for one of the most significant epidemics in history has caused severe global economic, social, and health damages. The drug repurposing approach and application of Structure-based Drug Discovery (SBDD) using in silico techniques are increasingly frequent, leading to the identification of several molecules that may represent promising potential. Method: In this context, here we use in silico methods of virtual screening (VS), pharmacophore modeling (PM), and fragment-based drug design (FBDD), in addition to molecular dynamics (MD), molecular mechanics/Poisson-Boltzmann surface area (MM -PBSA) calculations, and covalent docking (CD) for the identification of potential treatments against SARS-CoV-2. We initially validated the docking protocol followed by VS in 1,613 FDA-approved drugs obtained from the ZINC database. Thus, we identified 15 top hits, of which three of them were selected for further simulations. In parallel, for the compounds with a fit score value ≤ of 30, we performed the FBDD protocol, where we designed 12 compounds Result: By applying a PM protocol in the ZINC database, we identified three promising drug candidates. Then, the 9 top hits were evaluated in simulations of MD, MM-PBSA, and CD. Subsequently, MD showed that all identified hits showed stability at the active site without significant changes in the protein's structural integrity, as evidenced by the RMSD, RMSF, Rg, SASA graphics. They also showed interactions with the catalytic dyad (His41 and Cys145) and other essential residues for activity (Glu166 and Gln189) and high affinity for MM-PBSA, with possible covalent inhibition mechanism. Conclution: Finally, our protocol helped identify potential compounds wherein ZINC896717 (Zafirlukast), ZINC1546066 (Erlotinib), and ZINC1554274 (Rilpivirine) were more promising and could be explored in vitro, in vivo, and clinical trials to prove their potential as antiviral agents.

Structural development of amyloid precursors in insulin B chain and the inhibition effect by fibrinogen

Amyloid fibrils are abnormal protein aggregates that relate to a large number of amyloidoses and neurodegenerative diseases. The oligomeric precursors, or prefibrillar intermediates, which emerge prior to the amyloid fibril formation, have been known to play a crucial role for the formation. Therefore, it is essential to elucidate the mechanisms of the structural development of the prefibrillar intermediates and ways to prevent its fibril formation. An insulin-derived peptide, insulin B chain, has been known for its stable accumulation of the prefibrillar intermediates. In this study, structural development of B chain prefibrillar intermediates was monitored by transmission electron microscopy and small-angle X-ray scattering combined with size exclusion chromatography and solid-state NMR spectroscopy to elucidate the stability and secondary structure. We further tracked its inhibition process by fibrinogen (Fg), which has been known to effectively prevent the amyloid fibril formation of B chain. We demonstrated that prefibrillar intermediates are wavy structures with low β-sheet content, growing in a multistep manner toward the nucleation for the amyloid fibril formation. In the presence of Fg, the formation of the prefibrillar intermediates slowed down by forming specific complexes. These observations suggest that the prefibrillar intermediates serve as reaction fields for the nucleation and its propagation for the amyloid fibril formation, whereas the inhibition of prefibrillar intermediate elongation by Fg is the significant factor to suppress the fibril formation. We propose that the obtained molecular picture could be a general inhibition mechanism of the amyloid fibril formation by the inhibitors.

Antifungal Mechanism of Vip3Aa, a Vegetative Insecticidal Protein, against Pathogenic Fungal Strains

Discovering new antifungal agents is difficult, since, unlike bacteria, mammalian and fungal cells are both eukaryotes. An efficient strategy is to consider new antimicrobial proteins that have variety of action mechanisms. In this study, a cDNA encoding Bacillus thuringiensis Vip3Aa protein, a vegetative insecticidal protein, was obtained at the vegetative growth stage; its antifungal activity and mechanism were evaluated using a bacterially expressed recombinant Vip3Aa protein. The Vip3Aa protein demonstrated various concentration- and time-dependent antifungal activities, with inhibitory concentrations against yeast and filamentous fungi ranging from 62.5 to 125 µg/mL and 250 to 500 µg/mL, respectively. The uptake of propidium iodide and cellular distributions of rhodamine-labeled Vip3Aa into fungal cells indicate that its growth inhibition mechanism involves its penetration within cells and subsequent intracellular damage. Furthermore, we discovered that the death of Candida albicans cells was caused by the induction of apoptosis via the generation of mitochondrial reactive oxygen species and binding to nucleic acids. The presence of significantly enlarged Vip3Aa-treated fungal cells indicates that this protein causes intracellular damage. Our findings suggest that Vip3Aa protein has potential applications in the development of natural antimicrobial agents.

Virtual prediction of purple rice ferulic acid as anti-inflammatory of TNF-α signaling

Purple rice is one of the main sources of ferulic acid (FA). Some studies reported anti-inflammatory properties of FA, but the interaction of FA with TNF-α signaling has not been elucidated. TNF-α is a target for anti-inflammatory drug research due to its major role in the inflammatory process. This study aims to investigate the interaction of FA with TNF-α and TNF-α receptor (TNFR) through in silico study and evaluate the drug-like properties and biological activity of FA. The interactions among FA (CID 445858), TNF-α (2AZ5), and TNFR (1NCF) were docked by Hex 8.0.0 Cuda, then visualized by Discovery Studio 2020 and LigPlot V.1.4.5. Apigenin-7-glucuronide (AG, CID 5319484) was used as the positive control. The drug-like properties were predicted by Lipinski’s rule of five and the biological activity was analyzed by PASS online. FA showed good properties as a drug-like molecule and biological activity as an anti-inflammatory. FA also showed good interaction with TNF-α and TNFR. FA bound to TNF-α at Asn92(B), Val91(B), Leu93(B), Phe124(B), Phe124(D), and Leu93(D) residues with docking energy of -214.6 kJ/mol, and bound to TNFR at Pro16(A), Glu56(B), Cys55(B), Glu54(B) residues with docking energy of -191.1 kJ/mol. FA could inhibit TNF-α – TNFR interaction by binding to TNFR at Glu54 residue, the same inhibition mechanism to AG which bind to TNFR at Glu54 and Val90. The current study shows that FA has the potential as an anti-inflammatory of TNF-α signaling and can be developed as an oral anti-inflammatory drug candidate.

Evaluation of TG202 inhibitor for tubing steels in 15% hydrochloric acid by electrochemical noise technology

Acid fracturing is an effective technology for increasing oil and gas production. However, acid will cause serious corrosion to the tubing. In this paper, the inhibition performance of TG202 inhibitor for acidizing of high temperature and high pressure gas wells on N80 carbon steel and 13Cr martensitic stainless steel tubing in 15% hydrochloric acid was studied by electrochemical noise technology. The results showed that with the increase of TG202 inhibitor content, the noise resistance increased and the corrosion rate of tubing steel decreased. Under the same condition, the order of corrosion rate of tubing steels: 13Cr > HP-13Cr > N80 > P110. The pitting corrosion of HP-13Cr and 13Cr is significant. The research showed that TG202 inhibitor had a protective effect on tubing during acidizing. The inhibition mechanism of TG202 inhibitor was discussed.

Structure-property Relationship of Flavonoids as Potential Green Inhibitors for Oilfield Scales: A Mini-review

Scale deposits are a significant flow assurance issue in oil and gas operation with huge financial consequences. Not only does scaling drastically impair well performance, but it also has the potential to permanently destroy formation and equipment. Scale inhibitors are commonly used to prevent the accumulation of scales. A good scale inhibitor should be stable at the minimum effective inhibitor concentration under imposed operating conditions without interfering with or being affected by other chemical additives. However, most conventional scale inhibitors that possess these attributes, do not meet environmental restrictions which make them unfavorable for continuous application, prompting the industry to focus more on developing eco-friendly substitutes. This paper reviews the various types of scale inhibitors and general scale inhibition mechanism, summarizes scale concepts and ultimately, assesses the potential of flavonoids from natural plants as potential green scale inhibitors.