A DFT study of vibrational spectra of 5-chlorouracil with molecular structure, HOMO-LUMO, MEPs/ESPs and thermodynamic properties

Identification and molecular mechanism of novel antioxidant peptide from fish sauce: A combined quantum chemistry and molecular simulation

Fish sauce, derived from fermented fish, exhibits a notable antioxidant effect after a six-month fermentation process, and we propose that potential antioxidant peptides were present in the fish sauce. We isolated, purified, and identified potential bioactive antioxidant peptides by using fish sauce fermented for 6 months. Additionally, molecular simulation was employed to investigate the antioxidant action mechanism of these bioactive peptides. The molecular docking results revealed that FS4-1 (MHQLSKK), FS4-2 (VLDNSPER), FS4-3 (MNPPAASIK), FS6-1(VLKQAAAGR), and FS6-2 (SPDVSPRR), could dock with the Keap1 receptor. The primary force (Van der Waals' force and hydrogen bonds) and key sites (GLY509 and ALA510) of Keap1 binding to peptides were determined. The active center was located in the side chain of amino acid Met at positions C7H78 and C7H79. We here identified antioxidant peptides in fish sauce and revealed the antioxidant mechanism through molecular simulations.

The synthesis of cinnamyl acetate and deacetyl-7-aminocephalosporanic acid by a GDSL-type esterase and its substrate specificity analysis

GDSL-type esterases are promising biocatalysts for the food and pharmaceutical industries. Here, a GDSL-type esterase from Aspergillus niger CCTCC No. M2012538 (INANE1) was expressed and purified in Pichia pastoris GS115, and its catalytic performances were evaluated, including the synthesis of cinnamyl acetate and deacetyl-7-aminocephalosporanic acid (D-7-ACA). In addition, molecular docking and molecular dynamics simulations analyzed INANE1's substrate specificity. The substrate specificity profile indicated the recombinant esterase (rINANE1) was an acetylesterase with high specificity for p-nitrophenyl acetate (p-NPA). The rINANE1 exhibited maximum activity at pH 8.0 and 35 °C, where Km and Vmax were calculated as 0.13±0.03 mM and 22.56 ± 0.32 μmoL/min/mg, respectively. The yield of cinnamyl acetate of about 85 % was achieved in 24 h. The conversion rate of 7-aminocephalosporanic acid (7-ACA) could reach 92.71 ± 1.78 % at 25 °C and 2.5 h. Moreover, the INANE1 structure model, molecular docking, and molecular dynamics simulation demonstrated that the pocket of the catalytic triad Ser34, Asn267, and His270 could only accommodate p-NPA. INANE1 may be the first fungi esterase with cinnamyl acetate synthetic activity and 7-ACA hydrolysis activity. Therefore, INANE1 would be a promising enzyme with industrial values.

Investigation of dual inhibition of antibacterial and antiarthritic drug candidates using combined approach including molecular dynamics, docking and quantum chemical methods

Emerging antibiotic resistance in bacteria threatens immune efficacy and increases susceptibility to bone degradation and arthritic disorders. In our current study, we utilized a three-layer in-silico screening approach, employing quantum chemical methods, molecular docking, and molecular dynamic methods to explore the novel drug candidates similar in structure to floroquinolone (ciprofloxacin). We investigated the interaction of novel similar compounds of ciprofloxacin with both a bacterial protein S. aureus TyrRS (1JIJ) and a protein associated with gout arthritis Neutrophil collagenase (3DPE). UTIs and gout are interconnected through the elevation of uric acid levels. We aimed to identify compounds with dual functionality: antibacterial activity against UTIs and antirheumatic properties. Our screening based on several methods, sorted out six promising ligands. Four of these (L1, L2, L3, and L6) demonstrated favorable hydrogen bonding with both proteins and were selected for further analysis. These ligands showed binding affinities of -8.3 to -9.1 kcal/mol with both proteins, indicating strong interaction potential. Notably, L6 exhibited highest binding energies of -9.10 and -9.01 kcal/mol with S. aureus TyrRS and Neutrophil collagenase respectively. Additionally, the pkCSM online database conducted ADMET analysis on all lead ligand suggested that L6 might exhibit the highest intestinal absorption and justified total clearance rate. Moreover, L6 showed a best predicted inhibition constant with both proteins. The average RMSF values for all complex systems, namely L1, L2, L3 and L6 are 0.43 Å, 0.57 Å, 0.55 Å, and 0.51 Å, respectively where the ligand residues show maximum stability. The smaller energy gap of 3.85 eV between the HOMO and LUMO of the optimized molecule L1 and L6 suggests that these are biologically active compound. All the selected four drugs show considerable stabilization energy ranging from 44.78 to 103.87 kcal/mol, which means all four compounds are chemically and physically stable. Overall, this research opens exciting avenues for the development of new therapeutic agents with dual functionalities for antibacterial and antiarthritic drug designing.

Shedding light into the biological activity of aminopterin, via molecular structural, docking, and molecular dynamics analyses

In this study, the structural and anticancer properties of aminopterin, as well as its antiviral characteristics, were elucidated. The preferred conformations of the title molecule were investigated with semiempirical AM1 method, and the obtained the lowest energy conformer was then optimized by using density functional (DFT/B3LYP) method with 6-311++G(d,p) as basis set. The vibrational frequencies of the optimized structure were calculated by the same level of theory and were compared with the experimental values. The vibrational assignments were performed based on the computed potential energy distribution (PED) of the vibrational modes. The molecular electrostatic potential (MEP) and frontier molecular orbitals (HOMO, LUMO) analyses were carried out for the optimized structure and the chemical reactivity has been scrutinized. To enlighten the biological activity of aminopterin as anticancer and anti-COVID-19 agents, aminopterin was docked into DNA, αIIBβ3 and α5β1integrins, human dihydrofolate reductase, main protease (Mpro) of SARS-CoV-2 and SARS-CoV-2/ACE2 complex receptor. The binding mechanisms of aminopterin with the receptors were clarified. The molecular docking results revealed the strong interaction of the aminopterin with DNA (-8.2 kcal/mol), αIIBβ3 and α5β1 integrins (-9.0 and -10.8 kcal/mol, respectively), human dihydrofolate reductase (-9.7 kcal/mol), Mpro of SARS-CoV-2 (-6.7 kcal/mol), and SARS-CoV-2/ACE2 complex receptor (-8.1 kcal/mol). Moreover, after molecular docking calculations, top-scoring ligand-receptor complexes of the aminopterin with SARS-CoV-2 enzymes (6M03 and 6M0J) were subjected to 50 ns all-atom MD simulations to investigate the ligand-receptor interactions in more detail, and to determine the binding free energies accurately. The predicted results indicate that the aminopterin may significantly inhibit SARS-CoV-2 infection. Thus, in this study, as both anticancer and anti-COVID-19 agents, the versatility of the biological activity of aminopterin was shown.Communicated by Ramaswamy H. Sarma.

Computational discovery of dual potential inhibitors of SARS-CoV-2 spike/ACE2 and Mpro: 3D-pharmacophore, docking-based virtual screening, quantum mechanics and molecular dynamics

To find drugs against COVID-19, caused by the SARS-CoV-2, promising targets include the fusion of the viral spike with the human angiotensin-converting enzyme 2 (ACE2) as well as the main protease (Mpro). These proteins are responsible for viral entry and replication, respectively. We combined several state-of-the-art computational methods, including, protein-ligand interaction fingerprint, 3D-pharmacophores, molecular-docking, MM-GBSA, DFT, and MD simulations to explore two databases: ChEMBL and NANPDB to identify molecules that could both block spike/ACE2 fusion and inhibit Mpro. A total of 1,690,649 compounds from the two databases were screened using the pharmacophore model obtained from PLIF analysis. Five recent complexes of Mpro co-crystallized with different ligands were used to generate the pharmacophore model, allowing 4,829 compounds that passed this prefilter. These were then submitted to molecular docking against Mpro. The 5% top-ranked docking hits from docking result having scores < -8.32 kcal mol-1 were selected and then docked against spike/ACE2. Only four compounds: ChEMBL244958, ChEMBL266531, ChEMBL3680003, and 1-methoxy-3-indolymethyl glucosinolate (4) displayed binding energies < - 8.21 kcal mol-1 (for the native ligand) were considered as putative dual-target inhibitors. Furthermore, predictive ADMET, MM-GBSA and DFT/6-311G(d,p) were performed on these compounds and compared with those of well-known antivirals. DFT calculations showed that ChEMBL244958 and compound 4 had significant predicted reactivity values. Molecular dynamics simulations of the docked complexes were run for 100 ns and used to validate the stability docked poses and to confirm that these hits are putative dual binders of the spike/ACE2 and the Mpro.

Investigation on synthesized sulfonamide Schiff base with DFT approaches and in silico pharmacokinetic studies: Topological, NBO, and NLO analyses

The sulfonamide Schiff base (C16H14N4O3S) was successfully synthesized and experimentally ascertained. The main purpose of this research is to investigate the geometry of the aforesaid molecule using both experimental and density functional theory (DFT) techniques and determine its drug likeness characteristics, docking ability as an insulysin inhibitor, and its NLO property. For the computational investigations the DFT approaches were utilized at the B3LYP level with the 6-311G+(d,p) basic set. The experimental results of the compound (such as FT-IR, UV-Vis, and 1H NMR) were compared with simulated data. The both results were well and consistent with previously related published data. The obtained spectral results confirm the formation of the Schiff base compound. Both π-π* and n-π* interactions were found in experimental and computational UV-Vis spectra, as well as in the natural bond orbital (NBO) study. The molecular, electronic, covalent, and non-covalent interactions were analyzed using DFT studies. Both experimental and simulation results revealed that the compound is successfully formed and relatively stable. The compound with a lower band gap showed high chemical reactivity. The medicinal characteristics of the compound were evaluated using in silico medicinal methods. The investigated compound was also followed Pfizer, Golden Triangle, GSK as well as Lipinski's rules. Therefore, the compound has more favorable absorption, distribution, metabolism, excretion, and toxicity (ADMET) profile and it can be used as non-toxic oral drug candidate. The compound was exhibited good insulysin inhibitory activity and it has almost eighteen times higher non-linear optical properties than urea and three times higher than potassium dihydrogen phosphate (KDP).

Synthesis, quantum chemical calculations, in silico and in vitro bioactivity of a sulfonamide-Schiff base derivative

The sulfonamide Schiff base compound (E)-4-((4-(dimethylamino)benzylidene)amino)-N-(5-methylisoxazol-3-yl)benzenesulfonamide was successfully prepared and fully characterized. The foremost objective of this study was to explore the molecular geometry of the aforementioned compound and determine its drug likeness characteristics, docking ability as an insulysin inhibitor, anticancer and antioxidant activities. The molecular structure of this compound was optimized using the B3LYP/6-311G+(d,p) level of theory. The compound was completely characterized utilizing both experimental and DFT approaches. Molecular electrostatic potential, frontier molecular orbitals, Fukui function, drug likeness, and in silico molecular docking analyses of this compound were performed. Wave functional properties such as localized orbital locator, electron localization function and non-covalent interactions were also simulated. The compound was screened for anticancer and antioxidant activities using in vitro technique. The observed FT-IR, UV-Vis, and 1H NMR results compared with simulated data and both results were fairly consistent. The experimental and computational spectral findings confirm the formation of the Schiff base compound. Both π-π* and n-π* transitions were observed in both experimental and computational UV-Vis spectra. The examined compound followed to Pfizer, Golden Triangle, GSK, and Lipinski's rules. Consequently, it possesses a more favorable absorption, distribution, metabolism, excretion, and toxicity (ADMET) profile, making it a suitable candidate for non-toxic oral drug use. Moreover, the compound exhibited promising insulysin inhibition activity in an in silico molecular docking. The compound showed in vitro anticancer activity against A549 cancer cells with an IC50 value of 40.89 μg/mL and moderate antioxidant activity.

Discerning toxic nerve gas agents via a distinguishable 'turn-on' fluorescence response: multi-stimuli responsive quinoline derivatives in action

We have successfully synthesized quinoline derivatives that exhibit easy scalability and responsiveness to multiple stimuli. These derivatives are capable of forming self-assembled nanoscopic aggregates in an aqueous medium. Consequently, when placed in an aqueous environment, we observe dual fluorescence originating from both twisted intramolecular charge transfer and aggregation-induced emission. The introduction of nerve gas agents, such as diethyl chlorophosphate (DClP) or diethylcyanophosphate (DCNP), to the probe molecules facilitates the charge-transfer process, resulting in a red-shift in absorption maxima. Notably, when operating in fluorescence mode, both of these analytes produce distinct output signals, making them easily distinguishable. DCNP generates a blue fluorescence, while the addition of DClP yields cyan fluorescence. Our mechanistic investigation reveals that the initial step involves phosphorylation of the quinoline nitrogen end. However, in the case of DCNP, the released cyanide ion subsequently attacks the carbonyl carbon centre, forming a cyanohydrin derivative. The response to these target analytes appears to be influenced by the nucleophilicity of the quinoline nitrogen end and the electrophilic nature of the carbonyl unit.

Investigation of cathinone analogs targeting human dopamine transporter using molecular modeling

In a step towards understanding the structure-property relationship among Synthetic Cathinones (SCs), a combined methodology based on Density Functional Theory (DFT), Administration, Distribution, Metabolism, Excretion, and Toxicity (ADMET) predictions, docking and molecular dynamics simulations have been applied to correlate physicochemical descriptors of various SCs to their biological activity. The results from DFT and molecular docking studies correlate well with each other explaining the biological activity trends of the studied SCs. Quantum mechanical descriptors viz. polarizability, electron affinity, ionization potential, chemical hardness, electronegativity, molecular electrostatic potential, and ion interaction studies unravel the distinguishingly reactive nature of Group D (pyrrolidine substituted) and Group E (methylenedioxy and pyrrolidine substituted) compounds. According to ADMET analysis, Group D and Group E molecules have a higher probability of permeating through the blood-brain barrier. Molecular docking results indicate that Phe76, Ala77, Asp79, Val152, Tyr156, Phe320, and Phe326 constitute the binding pocket residues of hDAT in which the most active ligands MDPV, MDPBP, and MDPPP are bound. Finally, to validate the derived quantum chemical descriptors and docking results, Molecular Dynamics (MD) simulations are performed with homology-modelled hDAT (human dopamine transporter). The MD simulation results revealed that the majority of SCs remain stable within the hDAT protein's active sites via non-bonded interactions after 100 ns long simulations. The findings from DFT, ADMET analysis, molecular docking, and molecular dynamics simulation studies complement each other suggesting that pyrrolidine-substituted SCs (Group D and E), specifically, MPBP and PVN are proven potent SCs along with MDPV, validating various experimental observations.Communicated by Ramaswamy H. Sarma.

A DFT study on substituents, solvent, and temperature effect and mechanism of Diels-Alder reaction of hexafluoro-2-butyne with furan

CONTEXT

Furan and its derivatives constitute a vital class of heterocyclic chemistry used widely in organic synthesis via Diels-Alder reactions. As fluorine incorporation has been of great interest due to the limited possible pathways, the present study on [4 + 2] cycloaddition Diels-Alder reaction, between hexafluoro-2-butyne and 2-substituted (NH2, OCH3, OTMS, NHBoc) furans, uses the reaction as a likely route. The computational study revealed that that the reaction is feasible in all conditions and is most favorable for NH2 substituent in furan. The study of the effect of temperature has depicted that low temperature favors the formation of adducts, while the rise in temperature prefers ring opening to form 4-substituted-2,3-di(trifluoromethyl)phenol derivatives. The feasibility of a reaction has been determined by Gibbs energy change. The transition state study has been performed to find the activation energy, C-C single bond formation and global electron density transfer (GEDT) involved in the adduct formation. MEP plots have been used to understand the region of electrophilicity and nucleophilicity character. Furthermore, the mechanism for the formation of phenol products has been discussed. The decomposition of the NHBoc group at higher temperatures has been proved via a proposed mechanism and compared with experimental results.

METHODS

The reaction was theoretically investigated using B3LYP hybrid functional with 6-311 + G(d,p) basis sets, in gas phase and under different solvent conditions like water, acetonitrile, and THF. The transition state structures of the adduct were optimized at the lower basis set B3LYP/6-31 + G(d,p) as well as at the higher basis set B3LYP/6-311 + G(d,p) level. The changes in Gibbs energy (∆G) for the formation of products at different temperatures and in various solvents have been calculated at B3LYP/6-311 + G(d,p) level.

In Silico and In Vitro Analyses to Repurpose Quercetin as a Human Pancreatic α-Amylase Inhibitor

Human pancreatic α-amylase (HPA), situated at the apex of the starch digestion hierarchy, is an attractive therapeutic approach to precisely regulate blood glucose levels, thereby efficiently managing diabetes. Polyphenols offer a natural and multifaceted approach to moderate postprandial sugar spikes, with their slight modulation in carbohydrate digestion and potential secondary benefits, such as antioxidant and anti-inflammatory effects. Taking into consideration the unfavorable side effects of currently available commercial medications, we aimed to study a library of polyphenols attributed to their remarkable antidiabetic properties and screened the most potent HPA inhibitor via a comprehensive in silico study encompassing molecular docking, molecular mechanics with generalized Born and surface area solvation (MM/GBSA) calculation, molecular dynamics (MD) simulation, density functional theory (DFT) study, and pharmacokinetic properties followed by an in vitro assay. Significant hydrogen bonding with the catalytic triad residues of HPA, prominent MM/GBSA binding energy of -27.03 kcal/mol, and the stable nature of the protein-ligand complex with regard to 100 ns MD simulation screened quercetin as the best HPA inhibitor. Additionally, quercetin showed strong reactivity in the substrate-binding pocket of HPA and exhibited favorable pharmacokinetic properties with a considerable inhibitory concentration (IC50) of 57.37 ± 0.9 μg/mL against α-amylase. This study holds prospects for HPA inhibition and suggests quercetin as an approach to therapy for diabetes; however, it is imperative to conduct further research.

Application of DFT Calculations in Designing Polymer-Based Drug Delivery Systems: An Overview

Drug delivery systems transfer medications to target locations throughout the body. These systems are often made up of biodegradable and bioabsorbable polymers acting as delivery components. The introduction of density functional theory (DFT) has tremendously aided the application of computational material science in the design and development of drug delivery materials. The use of DFT and other computational approaches avoids time-consuming empirical processes. Therefore, this review explored how the DFT computation may be utilized to explain some of the features of polymer-based drug delivery systems. First, we went through the key aspects of DFT and provided some context. Then we looked at the essential characteristics of a polymer-based drug delivery system that DFT simulations could predict. We observed that the Gaussian software had been extensively employed by researchers, particularly with the B3LYP functional and 6-31G(d, p) basic sets for polymer-based drug delivery systems. However, to give researchers a choice of basis set for modelling complicated organic systems, such as polymer-drug complexes, we then offered possible resources and presented the future trend.