Main Inhibition Mechanism Research Articles

Mechanism of Action of Streptococcus downii, a New Bacterial Species with Probiotic Potential.

Streptococcus downii is a recently reported bacterial species of oral origin, with inhibitory capacity against Streptococcus mutans, Actinomyces naeslundii, Veillonella parvula and Aggregatibacter actinomycetemcomitans, which confers upon it the potential of being an oral probiotic. The aim of the present study was to identify the potential mechanisms by which S. downii exerts its inhibitory effect on S. mutans. To this end, the study assessed the consumption of glucose and proteins available in the culture medium, the modification of the pH, the production of short-chain fatty acids, the changes in the protein panel of the inhibition halo, the production of hydrogen peroxide and the effect of proteinase K. There were no differences in the glucose values or in the protein content of the medium, but there was a reduction in pH (with no effect on the growth of S. mutans). Significant increases were detected in the levels of lactic and formic acid (with no effect on the growth of S. mutans), as well as changes in the peptide panel (with no effect on the growth of S. mutans). The inhibitory effect was maintained in the presence of peroxidase but disappeared after adding proteinase K. Based on these results, it is suggested that the main mechanism of inhibition of S. downii against S. mutans is the production of bacteriocins.

Analysis of corrosion inhibition of Kleinhovia hospita plant extract aided by quantification of hydrogen evolution using a GLCM/SVM method

During a corrosion inhibition test, a combination of common electrochemical corrosion test methods with an in-situ quantification of H2 evolution could provide a comprehensive analysis of the effectiveness of an organic inhibitor. This work analyzes the corrosion inhibition efficiency of Kleinhovia hospita plant extract on carbon steel specimens polarized in 1 M HCl, based on acquired H2 bubbles images, by using gray level co-occurrence matrix (GLCM) and support vector machine (SVM) classification. A conformity was established between the classified-algorithm models and the corrosion test results obtained by potentiodynamic polarization test and electrochemical impedance spectroscopy. Hydrogen rate and corrosion rate show the same lowest trends at the addition of 3000 mg/L of KH extract. The inhibitor addition led to 99% of maximum inhibition efficiency. Based on the polarization data, KH extract is a mixed type inhibitor. Supported by Langmuir calculation for adsorption isotherm, a physisorption is stated as the main inhibition mechanism. The feature extraction using GLCM was able to distinguish changes in H2 bubbles characteristics where the addition of inhibitor affected the corrosion rate. The GLCM/SVM method applied as a linear kernel function and showed 88% accuracy with d = 5 for image data testing. Remarkable changes in H2 gas bubbles characteristic were observed in the specimen immersed in the solution with 3000 mg/L inhibitor addition, signified by 99% inhibition efficiency.

Reductive dehalogenation pathways and inhibition mechanisms of 2,5-dichloronitrobenzene in UV/sulfite advanced reduction process

2,5 − dichloronitrobenzene (2,5 − DCNB) and its chlorine − containing intermediates as adsorbable organic halogens (AOX), which may cause persist environment and health damages, are widely present in fine chemical wastewater. However, AOX in high − salt wastewater are hardly removed by biological process and advanced oxidation process (AOPs). Advanced reduction processes (ARPs), especially UV/sulfite process, have attracted increasing attention in past few years due to their powerful reduction potential to refractory contaminants. In this study, the kinetics, main inhibition mechanisms, and degradation pathways of 2,5 − DCNB in UV/sulfite process were studied. The apparent reaction rate (kobs) increasing from 0.0059 min−1 to 0.0628 min−1 with sulfite dosage increasing from 2.6 mM to 104.2 mM and from 0.0027 min−1 to 0.0659 min−1 with pH value increasing from 3 to 12. Relative quantitation method based on EPR was developed to prove the dominant role of hydrated electron (eaq−) in UV/sulfite ARPs. A new sulfite activating pathway in dark was discovered at lower pH, which partly inhibits the ARPs. The nonlinear increase of kobs with increasing sulfite dosage was attributed to UV scattering which is caused by density fluctuation. The inhibition of Cl− triggered by ●OH from H2O direct photolysis by UV at 185 nm from lower pressure mercury lamp. This inhibition is linearly depending on Cl− concentration. The multiple competitive inhibition of NO3− was discussed and the three pathways are “inner filter” effect, eaq− competition and oxidizing species generation. In addition, the reduction pathways of 2,5 − DCNB during UV/sulfite ARPs were predicted by intermediates identification and density functional theory (DFT) calculation. Cyclohexanol with lower toxicity was identified as final product of UV/sulfite process. This study revealed the capacity of UV/sulfite ARPs for direct dehalogenation on benzene ring and the application potential in industrial wastewater dehalogenation.

PMo12 as a redox mediator for bio-reduction of Cr(VI): Promotor or inhibitor?

Slow reduction rate and low reduction ability were the main limitations of bio-reduction of Cr(VI). As an efficient redox mediator, how phosphomolybdic acid (PMo12) affected bio-reduction of Cr(VI) was worthy of exploration. In this study, short-term and long-term effects of PMo12 on Cr(VI) reduction were investigated to reveal the relevant mechanism. After evaluating the short-term effect of PMo12 concentration from 0.05 to 1.00 mM on Cr(VI) bio-reduction, 0.50 mM was found to be optimum by improving Cr(VI) reduction rate by 16.3 % and microbial electron transport system activity (ETSA) by 43.0 % with Cr(VI) reduction efficiency of 100 % in short-term (22 h) batch experiments. By contrast, in long-term (28 days) continuous flow experiments, 0.50 mM PMo12 exhibited serious inhibition on Cr(VI) bio-reduction. The cumulative toxicity of Mo, strong oxidative stress (reactive oxygen species increased by 16.5 %), the inhibition of extracellular polymeric substances production and the reduction of microbial activity were proved to be the main inhibition mechanism. In terms of microbial electron transport system, the main electron carriers including flavin mononucleotide (FMN), nitrate reductase (NAR), nitrite reductase (NIR) were seriously inhibited. BugBase analysis confirmed that the relative abundance of biofilm forming bacteria decreased after PMo12 addition, and the relative abundance of oxidative stress tolerance bacteria continued to increase.

The stabilization mechanism of high-efficiency magnesium phosphate cement for arsenic remediation in lollingite polluted environments

Industrial non-ferrous metal smelting and processing activities are a major contributor to the migration of arsenic-containing minerals throughout the environment, such as lollingite, which poses a severe threat to human health due to its rapid oxidation and subsequent release of arsenic (As). Herein, two phosphate mineral systems (potassium phosphate and calcium phosphate) were used to explore the potential for As solidification and establish the As immobilization mechanisms. Experimental results show that the compressive strength of the calcium phosphate system was higher than that of the potassium phosphate system due to the higher bond energy of the Ca–O–Mg–O–P–O system (31109 kJ /mol), as compared to the K–O–Mg–O–P–O system (16189.2 kJ /mol). Furthermore, the coordination capability of arsenic oxyanions with Ca or Fe ions was stronger than that of phosphorus oxyanions with Ca or Fe ions. The main mechanism of inhibition of As migration by magnesium phosphate cement (MPC) binders, was the formation of FeAsO4.H2O, Ca3(AsO4)2.H2O, MgHAsO4.H2O, CaMgAsO4(OH) and KMgAsO4.6H2O coprecipitates, with physical encapsulation by MgKPO4·6H2O (K-struvite), Ca2Mg(PO4)2·2H2O (Ca-struvite) and Mg2PO4(OH) phosphate-gel. Using Fe2O3-modified MPC binders with a Fe/As molar ratio of 3, the As immobilization efficiency reached 98.73%. The results of toxicity characteristic leaching procedure (TCLP) analysis confirmed that the maximum leached As concentrations from MPC binders cured for 7 days and 28 days were 0.31 mg/L and 0.06 mg/L, respectively, both of which were below the maximum permitted value for safe disposal (5 mg/L). These results verify the potential of MPC binders to be utilized as low-environmental impact and high-efficiency cementitious matrices for As pollution control and environmental remediation.

Outer Membrane Vesicles From The Gut Microbiome Contribute to Tumor Immunity by Eliciting Cross-Reactive T Cells.

A growing body of evidence supports the notion that the gut microbiome plays an important role in cancer immunity. However, the underpinning mechanisms remain to be fully elucidated. One attractive hypothesis envisages that among the T cells elicited by the plethora of microbiome proteins a few exist that incidentally recognize neo-epitopes arising from cancer mutations (“molecular mimicry (MM)” hypothesis). To support MM, the human probiotic Escherichia coli Nissle was engineered with the SIINFEKL epitope (OVA-E.coli Nissle) and orally administered to C57BL/6 mice. The treatment with OVA-E.coli Nissle, but not with wild type E. coli Nissle, induced OVA-specific CD8+ T cells and inhibited the growth of tumors in mice challenged with B16F10 melanoma cells expressing OVA. The microbiome shotgun sequencing and the sequencing of TCRs from T cells recovered from both lamina propria and tumors provide evidence that the main mechanism of tumor inhibition is mediated by the elicitation at the intestinal site of cross-reacting T cells, which subsequently reach the tumor environment. Importantly, the administration of Outer Membrane Vesicles (OMVs) from engineered E. coli Nissle, as well as from E. coli BL21(DE3)ΔompA, carrying cancer-specific T cell epitopes also elicited epitope-specific T cells in the intestine and inhibited tumor growth. Overall, our data strengthen the important role of MM in tumor immunity and assign a novel function of OMVs in host-pathogen interaction. Moreover, our results pave the way to the exploitation of probiotics and OMVs engineered with tumor specific-antigens as personalized mucosal cancer vaccines.

Effects of endogenous and exogenous dissolved organic matter on sorption behaviors of bisphenol A onto soils

The transport of organic contaminants in groundwater might be greatly affected by coexistence of dissolved organic matter (DOM) from different sources. In this study, the effects of endogenous and exogenous DOMs (referred to as DOMen and DOMex, respectively) on sorption behavior of bisphenol A (BPA) onto two reference soils were investigated by batch experiments and microscopic characterization. The results showed that BPA sorption onto soils was dominated by soil organic matter content and affected by DOM properties. The effect of DOMen on BPA sorption was also related to the inorganic components of the two soils. The decrease of organic matter content reduced the sorption capacity of fluvo-aquic soil. However, because the content of available inorganic components in black soil was high, after removing DOMen, more inorganic sites were exposed to increase the sorption capacity. In addition, DOMen could form complexes with BPA in solution, thus the removal of DOMen promoted BPA sorption onto black soil. Under the experimental conditions, contribution of DOMex to the total sorption of BPA onto both soils was not more than 30%. Results of dialysis experiments and soil sorption experiments indicated that effects of coexisting DOMex on BPA sorption was related to the affinity of DOMex to soils and complexation of BPA and DOMex. Since the affinity of DOMex to fluvo-aquic soil was relatively low, the complex of BPA and DOMex in solution was the main inhibition mechanism for BPA sorption. For black soil, higher complexation proportion of BPA with DOMex adsorbed onto soil which promoted BPA sorption onto soil. The findings are of significance for understanding the co-migration of DOM with BPA through soils.

Phytochemicals as steel corrosion inhibitor: an insight into mechanism

Abstract Corrosion is a spontaneous process that adversely affects strength and quality of economically vital materials including steel. Plant extracts are emerging as renewable, low cost and eco-friendly alternate to existing toxic chemical corrosion inhibitors. Physisorption, Chemisorption and retrodonation are the main mechanism of corrosion inhibition by plant extracts. Different functional groups of phytochemicals namely carbohydrate, lipids, terpenoids, phenolic acids, alkaloids and other nitrogen containing metabolites participate in physisorption, chemisorption and retrodonation with steel surface in presence of HCl and H2SO4 to act as corrosion inhibitors. Exact mechanism of inhibition depends upon presence of such phytochemical in the plant extracts.

Механизмы ингибирования AMPA рецепторов диминазеном

Diminazene is an anti-infective medication from the diarylamidine group. In this work we have shown for the first time that it inhibits AMPA type ionotropic glutamate receptors. Experiments were conducted on isolated Wistar rat neurons. Calcium-permeable AMPA receptors were studied on giant striatum cholinergic interneurons, while calcium-impermeable AMPA receptors – on hippocampal CA1 pyramidal neurons. Cells were isolated from slices by vibrodissociation. Currents were recorded by whole-cell patch-clamp method. Diminazene inhibited kainate-induced currents in both types of neurons in a concentration-dependent manner. IC50 values for calcium-permeable and calcium-impermeable AMPA receptors were 60±11 and 160±30 µM, respectively. It is interesting that the degree of inhibition by fixed diminazene concentration was increased with the increase of agonist concentration. The voltage-dependence curve for the inhibition of calcium-permeable AMPA receptors by fixed diminazene concentration was biphasic: minimal inhibition was observed at positive holding potentials, maximal – at -40 - -60 mV, while further hyperpolarization resulted in the smooth decrease of block. All these features strongly suggest that channel block with the ability to permeate into the cytoplasm is the main molecular mechanism of AMPA receptor inhibition by diminazene.

Transcriptome Analysis of Pseudomonas aeruginosa Biofilm Following the Exposure to Malaysian Stingless Bee Honey.

IntroductionMalaysian stingless bee honey (Trigona) has been aroused as a potential antimicrobial compound with antibiofilm activity. The capability of the gram-negative bacillus P. aeruginosa to sustain a fatal infection is encoded in the bacterium genome.MethodsIn the current study, a transcriptome investigation was performed to explore the mechanism underlying the biofilm dispersal of P. aeruginosa after the exposure to Trigona honey.ResultsMicroarray analysis of the Pseudomonas biofilm treated by 20% Trigona honey has revealed a down-regulation of 3478 genes among the 6085 screened genes. Specifically, around 13.5% of the down-regulated genes were biofilm-associated genes. The mapping of the biofilm-associated pathways has shown an ultimate decrease in the expression levels of the D-GMP signaling pathway and diguanylate cyclases (DGCs) genes responsible for c-di-GMP formation.ConclusionWe predominantly report the lowering of c-di-GMP through the down-regulation of DGC genes as the main mechanism of biofilm inhibition by Trigona honey.

Effects of phenolic compounds from blueberry leaves on the thermal decomposition of trimethylamine oxide in squid extract

Abstract The effects of chlorogenic acid and quercetin-3-D-galactoside on the decomposition of trimethylamine oxide (TMAO) in squid extract and the main mechanism of inhibition of thermal decomposition were studied. The results indicated that chlorogenic acid and quercetin-3-D-galactoside could inhibit decomposition of TMAO in squid extract. The amount of TMAO was increased by 11.79 and 15.76% in squid extract treated with chlorogenic acid and quercetin-3-D-galactoside from 0 and 2.5 g/L, respectively. The contents of trimethylamine (TMA), dimethylamine (DMA), and formaldehyde (FA) were significantly decreased with increasing contents of chlorogenic acid and quercetin-3-D-galactoside. There were many free radicals in squid extract at high temperatures; however, the free radical signals were weakened after the addition of chlorogenic acid and quercetin-3-D-galactoside therein. This implied that chlorogenic acid and quercetin-3-D-galactoside could inhibit the thermal decomposition of TMAO in squid extract, which was associated with the scavenging of their free radicals. This result provides a theoretical basis for the development and utilization of blueberry leaf extract as an efficient FA inhibitor for aquatic products.

Maltoheptaoside hydrolysis with chromatographic detection and starch hydrolysis with reducing sugar analysis: Comparison of assays allows assessment of the roles of direct α-amylase inhibition and starch complexation

The aim was to determine inhibition of human α-amylase activity by (poly)phenols using maltoheptaoside as substrate with direct chromatographic product quantification, compared to hydrolysis of amylose and amylopectin estimated using 3,5-dinitrosalicylic acid. Acarbose exhibited similar IC50 values (50% inhibition) with maltoheptaoside, amylopectin or amylose as substrates (2.37 ± 0.11, 3.71 ± 0.12 and 2.08 ± 0.01 µM respectively). Epigallocatechin gallate, quercetagetin and punicalagin were weaker inhibitors of hydrolysis of maltoheptaoside (<50% inhibition) than amylose (IC50: epigallocatechin gallate = 20.41 ± 0.25 µM, quercetagetin = 30.15 ± 2.05 µM) or amylopectin. Interference using 3,5-dinitrosalicylic acid was in the order punicalagin > epigallocatechin gallate > quercetagetin, with minimal interference using maltoheptaoside as substrate. The main inhibition mechanism of epigallocatechin gallate and punicalagin was through complexation with starch, especially amylose, whereas only quercetagetin additionally binds to the α-amylase active site. Interference is minimised using maltoheptaoside as substrate with product detection by chromatography, potentially allowing assessment of direct enzyme inhibition by almost any compound.

Both Boceprevir and GC376 efficaciously inhibit SARS-CoV-2 by targeting its main protease

COVID-19 was declared a pandemic on March 11 by WHO, due to its great threat to global public health. The coronavirus main protease (Mpro, also called 3CLpro) is essential for processing and maturation of the viral polyprotein, therefore recognized as an attractive drug target. Here we show that a clinically approved anti-HCV drug, Boceprevir, and a pre-clinical inhibitor against feline infectious peritonitis (corona) virus (FIPV), GC376, both efficaciously inhibit SARS-CoV-2 in Vero cells by targeting Mpro. Moreover, combined application of GC376 with Remdesivir, a nucleotide analogue that inhibits viral RNA dependent RNA polymerase (RdRp), results in sterilizing additive effect. Further structural analysis reveals binding of both inhibitors to the catalytically active side of SARS-CoV-2 protease Mpro as main mechanism of inhibition. Our findings may provide critical information for the optimization and design of more potent inhibitors against the emerging SARS-CoV-2 virus.

Drastically inhibited nZVI-Fenton oxidation of organic pollutants by cysteine: Multiple roles in the nZVI/O2/hv system

The influence of l-cysteine, a common aliphatic amino acid, on the zero-valent iron (nZVI)/O2 photo-Fenten degradation of rhodamine B (RhB) was investigated in this study. The oxidation rate of RhB in the nZVI/O2/hv system was 91.2% after 40 min under the illumination and oxygen conditions and pH of 3, but when cysteine was introduced into the system, the oxidization process was inhibited. The removal of RhB was only about 50% after 40 min at a cysteine concentration ≥50 μM. It was shown experimentally that, under dark conditions, only 40.5% and 19.8% RhB was removed by the nZVI/O2 and nZVI/O2/cysteine systems, respectively. Electron paramagnetic resonance (EPR) and iron dissolving experiments revealed that the addition of cysteine clearly reduced the production of hydroxyl radicals (OH) and Fe2+ and Fe3+. In addition, Fourier transform infrared spectroscopy (FTIR) demonstrated that cysteine could form hydrogen bonds on the iron surface. These results indicated that the main inhibition mechanism of cysteine was the alleviation of the oxidation of nZVI to Fe2+ and Fe3+ through wrapping the nZVI particles. Moreover, cystine (the oxidized form of CYS) could partly react with OH to regenerate cysteine, which resulted in competition with RhB for OH. Another possible reason for the inhibitory effect of cysteine was the prevention of light utilization. These findings indicate a non-negligible inhibitory trait for heterogeneous Fenton process in wastewater treatment when amino acids are present.

MnTE-2-PyP Suppresses Prostate Cancer Cell Growth via H2O2 Production.

Prostate cancer patients are often treated with radiotherapy. MnTE-2-PyP, a superoxide dismutase (SOD) mimic, is a known radioprotector of normal tissues. Our recent work demonstrated that MnTE-2-PyP also inhibits prostate cancer progression with radiotherapy; however, the mechanisms remain unclear. In this study, we identified that MnTE-2-PyP-induced intracellular H2O2 levels are critical in inhibiting the growth of PC3 and LNCaP cells, but the increased H2O2 levels affected the two cancer cells differently. In PC3 cells, many proteins were thiol oxidized with MnTE-2-PyP treatment, including Ser/Thr protein phosphatase 1 beta catalytic subunit (PP1CB). This resulted in reduced PP1CB activity; however, overall cell cycle progression was not altered, so this is not the main mechanism of PC3 cell growth inhibition. High H2O2 levels by MnTE-2-PyP treatment induced nuclear fragmentation, which could be synergistically enhanced with radiotherapy. In LNCaP cells, thiol oxidation by MnTE-2-PyP treatment was not observed previously and, similarly to PC3 cells, there was no effect of MnTE-2-PyP treatment on cell cycle progression. However, in LNCaP cells, MnTE-2-PyP caused an increase in low RNA population and sub-G1 population of cells, which indicates that MnTE-2-PyP treatment may cause cellular quiescence or direct cancer cell death. The protein oxidative modifications and mitotic catastrophes caused by MnTE-2-PyP may be the major contributors to cell growth inhibition in PC3 cells, while in LNCaP cells, tumor cell quiescence or cell death appears to be major factors in MnTE-2-PyP-induced growth inhibition.

Experimental evaluation of thiamine as a new clay swelling inhibitor

This study aims at evaluating the performance of thiamine as a new eco-friendly shale inhibitor in water-based drilling fluids (WBDFs). The evaluation experiments include sedimentation, bentonite inhibition, filtration, zeta potential, thermal gravimetric analysis, scanning electron microscopy, X-ray diffraction, shale cuttings recovery, linear swelling and Fourier transform infrared spectroscopy (FTIR). The performance of thiamine was compared to potassium chloride. In contrast to deionized water, the aqueous solution of thiamine exhibited greater power to inhibit montmorillonite (Mt) dispersion, much more Mt loading capacity (280 g/L) and fluid loss, lower Mt mass loss, larger aggregated Mt particles, lower interlayer space of the Mt particles, less shale cuttings disintegration and lower linear swelling. Adsorption of thiamine on Mt led to a significant shift in the value of zeta potential (from −17.1 to +8.54 mV). Thiamine demonstrated superior inhibitive performance than potassium chloride. FTIR analysis confirmed that thiamine is adsorbed on Mt particles. The compatibility test revealed the compatibility of thiamine with conventional WBDF additives. It was concluded that the main probable inhibition mechanisms of thiamine are the cation exchange and Mt surface coating. In view of its prominent inhibition capacity and great environmental acceptability, thiamine is a promising inhibitor for drilling in water-sensitive formations.

Effects of four bamboo derived flavonoids on advanced glycation end products formation in vitro

• BLFs inhibit the production of both endogenous and exogenous AGEs. • BLFs can inhibit the oxidation of proteins. • FOs can reduce the content of AGEs precursors (dicarbonyl compounds). • BLFs can retard the combination between dicarbonyl compounds and proteins. Advanced glycation end products (AGEs) are formed irreversibly during endogenous protein glycation and Maillard reaction, and closely related to many diseases such as diabetes. In this study, inhibitory activities of four flavonoids obtained from bamboo leaf, including orientin, isoorientin, vitexin and isovitexin, were investigated on the formation of AGEs. Fluorescence spectrophotometry was used to determine the contents of fluorescence AGEs and protein oxidation products in the system. The residual amount of dicarbonyl compounds were determined by a high-performance liquid chromatography. The results showed that the four bamboo-leaf-flavonoids (BLFs) significantly depress the formation of fluorescence AGEs and protein oxidation products. We demonstrated that the main inhibition mechanisms of BLFs include inhibiting proteins oxidation, decreasing AGEs precursors concentration and blocking the combination between dicarbonyl compounds and proteins. In conclusion, extraction of bamboo leaf may be a promising dietary supplement to reduce AGEs in human body.

Communication: Novel Drug Combination Doxycycline-Melatonin- Digoxin(D-M-D) for Possible Covid-19 Treatment

Covid-19, stands for a Coronavirus disease appeared in Wuhan province of China in December 2019, for first time. So far, it has spread rapidly throughout the world with mortality of 1-2% in general population. The main fatal mechanism is acute respiratory distress syndrome due to the development of severe pneumonia with or without sepsis, especially in patients aged over 50 with serious comorbidities. The deadly outcome of Covid-19 regarding the aforementioned infected group, has intensified scientific research worldwide in order to create novel vaccination and drug treatment. Based on current Guidelines of National Health Commission of the People’s Republic of China drugs such as IFNa, Lopinavir/ritonavir, Ribavirin, Chloroquine phosphate and Arbidol have been proposed for the treatment of Covid-19 infection. Yet, research is still ongoing on a variety of other potential drugs. Doxycycline(D), is an antimalarial antibiotic which exhibits both anti-inflammatory and antiviral action. In particular, doxycycline inhibits Dengue virus replication in vitro. Melatonin(M), among other mechanisms demonstrates immune-regulatory, antioxidant and antiviral activity, as well. Melatonin administration shows protective action in cases of Acute Respiratory Distress Syndrome(ARDS) and septic shock. Digoxin(D), is a cardiac glycoside which has been scientifically proven to possess antiviral properties. The main inhibition mechanism is the blocking of Na-K-ATPase in a variety of viral infections, including Coronavirus family’s ones. Hypothesis, that the three previous agents(D-M-D) deserve to be scientifically tested in combination as potential drug treatment against Covid-19, seems to be a well-established proposal. Keywords: Covid-19, Melatonin, Digoxin, Doxycycline, antiviral treatment. Read more →

Influence of ZnO nanoparticles on anammox granules: The inhibition kinetics and mechanism analysis by batch assays

The spread application of nanoparticles (NPs) would cause instability on anaerobic ammonium oxidation (anammox) process. The present study focused on the short-term evaluation of ZnO nanoparticles (NPs) on anammox process by batch tests. Results indicated that a significant inhibition occurred under ZnO NPs stress of 5–100 mg gVSS−1. The half inhibitory concentration (IC50) of ZnO NPs was found to be 11.6 mg gVSS−1. The release of zinc ions from ZnO NPs dissolution was confirmed to be the main mechanism of inhibition on anammox activity. Haldane kinetic model simulation results confirmed that ZnO NPs imposed a non-competitive inhibition on nitrite conversion by decreasing maximum nitrogen removal rate (qmax), while they showed a competitive inhibition on ammonium conversion kinetics with affinity constant (Ks) increasing by 6 times. From the competitive inhibition results, it is suggested that the inhibition caused by ZnO NPs could be alleviated and recovered under higher ammonium concentrations.

X-Ray Crystallography, Fluorescence, and Molecular Simulations Studies on Regulators of SERCA

X-ray crystallography was used to solve the structure of the sarco/endoplasmic reticulum Ca-ATPase (SERCA) in complex with a novel small-molecule inhibitor (CXL017) that targets multidrug-resistant leukemia. The structure, solved at 3.0Å resolution, reveals CXL017 bound at a new site that is distinct from those of other known inhibitors of SERCA. This new site is near the ATP binding site, and suggests blockage of the phosphorylation site as the main mechanism of inhibition. This inhibitor binding site explains the synergistic relationship previously uncovered between CXL017 and other SERCA inhibitors. Identifying a novel inhibitor binding site provides insights for structure-guided improvements of this new class of potential anti-cancer agents. Molecular modeling and simulation, in combination with fluorescence spectroscopy, was used to generate new structural and mechanistic models that better describe the conformational landscape and regulation of SERCA by phospholamban (PLB) and sarcolipin (SLN). Fluorescence spectroscopy, including fluorescence resonance energy transfer (FRET) between fluorescent-fusion-protein constructs of SERCA, provided structural dynamics information about the cytosolic headpiece of SERCA and also on its interaction with regulatory peptides. Simulations were performed to sample conformations of fusion protein constructs, CFP-SERCA, YFP-PLB and YFP-SLN. The simulations were based on crystal structures of SERCA/PLB and SERCA/SLN complexes. FRET parameters, such as the inter-probe distance, RDA, and the orientation factor κ2 were calculated from simulations and used to generate predictions of fluorescence lifetimes and FRET efficiency distributions that were compared with experimental data. Based on these results, we propose a model of a super-inhibitory complex of SERCA, in which SERCA first binds SLN and then binds PLB. Spectroscopic studies were performed at the Biophysical Technology Center and computational work at the Minnesota Supercomputing Institute. This work was funded by NIH grants to DDT (GM27906 and AR07612).