Deposition of aggregates of hyperphosphorylated tau protein is a hallmark of tauopathies like Alzheimer and many other neurodegenerative diseases. A sensitive and selective method of in vivo ...detection of tau-aggregate presence and distribution could provide the means of an early diagnosis of tau-associated diseases. Furthermore, the use of selective molecular probes that enable histochemical differentiation of protein aggregates post-mortem would be advantageous for the insight into the properties of tau protein aggregates. We chose to design new molecular probes based on the structure of 2-(1-(6-((2-18Ffluoroethyl)(methyl)amino)-2-naphthyl)ethylidene)malononitrile to investigate their likelihood of fitting into VQIVYK tau protein binding channel model. In a modular approach, using cross-coupling reactions, we synthesized a series of candidates, radiolabeled them with fluorine-18 radioisotope, and determined their physicochemical and in vitro binding properties. Herein we report the synthesis of a series of molecular probes capable of detection of tau protein deposits in vitro.
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•Consensus docking is applied to evaluate binding of polyphenols to 3CLpro.•Ellagic acid is among strongest 3CLpro inhibitors of 19 polyphenols tested.•Ellagic acid binds into active ...site by hydrogen bonding and hydrophobic forces.•3CLpro-polyphenols interactions are confirmed by surface plasmon resonance.
The abundance of polyphenols in edible plants makes them an important component of human nutrition. Considering the ongoing COVID-19 pandemic, a number of studies have investigated polyphenols as bioactive constituents. We applied in-silico molecular docking as well as molecular dynamics supported by in-vitro assays to determine the inhibitory potential of various plant polyphenols against an important SARS-CoV-2 therapeutic target, the protease 3CLpro. Of the polyphenols in initial in-vitro screening, quercetin, ellagic acid, curcumin, epigallocatechin gallate and resveratrol showed IC50 values of 11.8 µM to 23.4 µM. In-silico molecular dynamics simulations indicated stable interactions with the 3CLpro active site over 100 ns production runs. Moreover, surface plasmon resonance spectroscopy was used to measure the binding of polyphenols to 3CLpro in real time. Therefore, we provide evidence for inhibition of SARS-CoV-2 3CLpro by natural plant polyphenols, and suggest further research into the development of these novel 3CLpro inhibitors or biochemical probes.
Poly(thiophen-3-ylacetic acid) (PTAA) is a representative of conjugated polyelectrolytes which are used in many optoelectronics devices. The performance of these devices is affected by the polymer ...conformation, which, among others, depends on the nature of the counterion. In this study, the binding of tetrabutylammonium counterions (TBA+) on PTAA was determined using a combination of nuclear Overhauser effect spectroscopy (NOESY) and molecular dynamics (MD) simulation. It was found that TBA+ ions specifically bind on the hydrophobic main chain of PTAA, while, according to MD simulations, alkali counterions predominantly bind in the vicinity of negatively charged carboxylic groups located on side chains. The MD trajectories were used to compute the relaxation matrices and the NOESY spectra. With the help of these latter calculations, the changes of intensities in experimental NOESY spectra upon binding of TBA+ ions to PTAA were interpreted.
Complexes of polycations and DNA, also known as polyplexes, have been extensively studied in the past decade, as potential gene delivery systems. Their stability depends strongly on the ...characteristics of the polycations, as well as the nature of the added salt. We present here a study of the DNA ionene complexation in which we used fluorescence, UV, and CD spectroscopy, combined with molecular dynamics computer simuations, to systematically examine the influence of the polycation charge density, as well as the influence of the nature of the counterion, on the stability of these systems. Ionenes as polycations, depending on their structural characteristics, have previously been found to possess low cytotoxicity, and are therefore particularly interesting as potential gene delivery agents. The results show that the DNA solutions in the presence of the polycation are more stable in the case of very large or very small ionene charge density, suggesting different mechanism of complexation. The computer simulations show that the ionenes with high charge density bind to the minor groove of the DNA molecules, while the ionenes with lower charge density bind to the major groove of the DNA. The nature of the counterions play only a minor role: precipitation of the DNA molecules occurs at slightly lower ionene concentration when fluoride counterion are present, compared to the bromide counterions.
► Epigallocatechin-3-gallate has the highest binding affinity to BSA among catechines. ► Structurally simpler hydroxycinnamic acids have a very low binding affinity to BSA. ► The binding site for ...polyphenols on BSA is near Trp213.
Polyphenols are responsible for the major organoleptic characteristics of plant-derived foods and beverages. Here, we investigated the binding of several polyphenols to bovine serum albumin (BSA) at pH 7.5 and 25°C: catechins (−)-epigallocatechin-3-gallate, (−)-epigallocatechin, (−)-epicatechin-3-gallate, flavones (kaempferol, kaempferol-3-glucoside, quercetin, naringenin) and hydroxycinnamic acids (rosmarinic acid, caffeic acid, p-coumaric acid). Fluorescence emission spectrometry and molecular docking were applied to compare experimentally determined binding parameters with molecular modelling. Among these polyphenols, (−)-epicatechin-3-gallate showed the highest Stern–Volmer modified quenching constant, followed by (−)-epigallocatechin-3-gallate. Similarly, (−)-epicatechin-3-gallate had the highest effect on the Circular Dichroic spectrum of BSA, while the changes induced by other polyphenols were negligible. Molecular docking predicted high binding energies for (−)-epicatechin-3-gallate and (−)-epigallocatechin-3-gallate for the binding site on BSA near Trp213. Our data reveal that the polyphenol structures significantly affect the binding process: the binding affinity generally decreases with glycosylation and reduced numbers of hydroxyl groups on the second aromatic ring.
COVID-19 represents a new potentially life-threatening illness caused by severe acute respiratory syndrome coronavirus 2 or SARS-CoV-2 pathogen. In 2021, new variants of the virus with multiple key ...mutations have emerged, such as B.1.1.7, B.1.351, P.1 and B.1.617, and are threatening to render available vaccines or potential drugs ineffective. In this regard, we highlight 3CLpro, the main viral protease, as a valuable therapeutic target that possesses no mutations in the described pandemically relevant variants. 3CLpro could therefore provide trans-variant effectiveness that is supported by structural studies and possesses readily available biological evaluation experiments. With this in mind, we performed a high throughput virtual screening experiment using CmDock and the “In-Stock” chemical library to prepare prioritisation lists of compounds for further studies. We coupled the virtual screening experiment to a machine learning-supported classification and activity regression study to bring maximal enrichment and available structural data on known 3CLpro inhibitors to the prepared focused libraries. All virtual screening hits are classified according to 3CLpro inhibitor, viral cysteine protease or remaining chemical space based on the calculated set of 208 chemical descriptors. Last but not least, we analysed if the current set of 3CLpro inhibitors could be used in activity prediction and observed that the field of 3CLpro inhibitors is drastically under-represented compared to the chemical space of viral cysteine protease inhibitors. We postulate that this methodology of 3CLpro inhibitor library preparation and compound prioritisation far surpass the selection of compounds from available commercial “corona focused libraries”.
During fungal infections, plant cells secrete chitinases, which digest chitin in the fungal cell walls. The recognition of released chitin oligomers via lysin motif (LysM)-containing immune host ...receptors results in the activation of defense signaling pathways. We report here that Verticillium nonalfalfae, a hemibiotrophic xylem-invading fungus, prevents these digestion and recognition processes by secreting a carbohydrate-binding motif 18 (CBM18)-chitin-binding protein, VnaChtBP, which is transcriptionally activated specifically during the parasitic life stages. VnaChtBP is encoded by the Vna8.213 gene, which is highly conserved within the species, suggesting high evolutionary stability and importance for the fungal lifestyle. In a pathogenicity assay, however, Vna8.213 knockout mutants exhibited wilting symptoms similar to the wild-type fungus, suggesting that Vna8.213 activity is functionally redundant during fungal infection of hop. In a binding assay, recombinant VnaChtBP bound chitin and chitin oligomers in vitro with submicromolar affinity and protected fungal hyphae from degradation by plant chitinases. Moreover, the chitin-triggered production of reactive oxygen species from hop suspension cells was abolished in the presence of VnaChtBP, indicating that VnaChtBP also acts as a suppressor of chitin-triggered immunity. Using a yeast-two-hybrid assay, circular dichroism, homology modeling, and molecular docking, we demonstrated that VnaChtBP forms dimers in the absence of ligands and that this interaction is stabilized by the binding of chitin hexamers with a similar preference in the two binding sites. Our data suggest that, in addition to chitin-binding LysM (CBM50) and Avr4 (CBM14) fungal effectors, structurally unrelated CBM18 effectors have convergently evolved to prevent hydrolysis of the fungal cell wall against plant chitinases and to interfere with chitin-triggered host immunity.
•QSAR models were developed to evaluate the anticorrosion activity of a series of 24 thiadiazole derivatives.•A wide variety of classical as well as binary fingerprint descriptors have been ...used.•Fingerprint descriptors are used to describe corrosion inhibition.•Novel candidate for corrosion inhibition on mild steel in 1M HCl was suggested.
In this study, different QSAR approaches based on the multiple linear regression (MLR), the kernel-based Partial Least-Square (kPLS) and Pharma-RQSAR models have been applied to investigate the relationship between chemical structure descriptors of thiadiazole derivatives and their anticorrosion activity. The screened classical descriptors were firstly used to establish the linear regression model. In addition, six binary fingerprints were successfully applied using the kernel-based Partial Least-Square (kPLS), with priority given to the atom-pair fingerprint model. The Pharma-RQSAR model was also used to analyze the role of the various substitutions in the common substructure. The atom-pair descriptors and Pharma-RQSAR models have the advantage of visualizing the contribution maps, suggesting the general substitution requirements of the thiadiazole derivatives as potential corrosion inhibitors.
Gold is a scarce element in the Earth's crust but indispensable in modern electronic devices. New, sustainable methods of gold recycling are essential to meet the growing eco‐social demand of gold. ...Here, we describe a simple, inexpensive, and environmentally benign dissolution of gold under mild conditions. Gold dissolves quantitatively in ethanol using 2‐mercaptobenzimidazole as a ligand in the presence of a catalytic amount of iodine. Mechanistically, the dissolution of gold begins when I2 oxidizes Au0 and forms a AuII2− species, which undergoes subsequent ligand‐exchange reactions and forms a stable bis‐ligand AuI complex. H2O2 oxidizes free iodide and regenerated I2 returns back to the catalytic cycle. Addition of a reductant to the reaction mixture precipitates gold quantitatively and partially regenerates the ligand. We anticipate our work will open a new pathway to more sustainable metal recycling with the utilization of just catalytic amounts of reagents and green solvents.
Gold can be dissolved in a sustainable manner with common household chemicals: iodine solution in ethanol, resembling diluted iodine tincture, green oxidant hydrogen peroxide and 2‐mercaptobenzimidazole, a compound used in medicinal applications. Catalytic reactions and green solvents are the basis for sustainable development and recycling of precious metals like gold.
Many intrinsically disordered proteins (IDP) that fold upon binding retain conformational heterogeneity in IDP‐target complexes. The thermodynamics of such fuzzy interactions is poorly understood. ...Herein we introduce a thermodynamic framework, based on analysis of ITC and CD spectroscopy data, that provides experimental descriptions of IDP association in terms of folding and binding contributions which can be predicted using sequence folding propensities and molecular modeling. We show how IDP can modulate the entropy and enthalpy by adapting their bound‐state structural ensemble to achieve optimal binding. This is explained in terms of a free‐energy landscape that provides the relationship between free‐energy, sequence folding propensity, and disorder. The observed “fuzzy” behavior is possible because of IDP flexibility and also because backbone and side‐chain interactions are, to some extent, energetically decoupled allowing IDP to minimize energetically unfavorable folding.
Fuzz box: A thermodynamic framework rationalizes the energetics of intrinsically disordered protein (IDP)–target interactions in terms of folding and binding contributions and clarifies the relationship between IDP sequence folding propensity, helix fraction, and the free energy of IDP–target association. The IDPs respond to sequence perturbations by adjusting fuzziness of the bound‐state ensemble in a manner similar to the Le Châtelier's principle.
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