Low Inhibitor Concentrations Research Articles

Rhodesain inhibitors on the edge of reversibility-irreversibility

A comparative study of Michael acceptor and keto-Michael acceptor inhibitors of the cysteine protease rhodesain has been performed. Five new inhibitors have been prepared bearing the peptide structure of the known cysteine protease inhibitor K11777 and differing on the warhead. For the preparation of the Michael acceptor warhead, a Horner-Wadsworth-Emmons reaction was used. In the synthetic routes of the keto-Michael acceptor warheads, keto-enoate and keto-vinyl sulfone, a metathesis reaction and a radical sulfonylation were the key steps, respectively. Interestingly, keto-Michael acceptors inhibited rhodesain through a dual mode of action, showing reversibility at low inhibitor concentrations and irreversibility at high inhibitor concentrations.

Strain effects on corrosion inhibition in stress corrosion of tubing steel

In this investigation, we explored the corrosion inhibition mechanism of an imidazoline quaternary ammonium salt (IQA) on J55 steel in simulated annulus environment through a series of experiments, including electrochemical testing, stress corrosion immersion experiments, and hydrogen permeation testing. Our findings reveal that IQA functions as a mixed-type inhibitor, exerting its inhibitory action through chemical adsorption. Notably, it exhibits a stronger inhibitory effect on the anodic dissolution reaction compared to the cathodic hydrogen evolution reaction. Despite the minor influence of tensile plastic strain on the average inhibition efficiency, it notably exacerbates pitting and initiates stress corrosion cracking. This underscores the limitation of average inhibition efficiency in accurately assessing IQA's efficacy against stress corrosion. Additionally, hydrogen permeation experiments and electrochemical testing demonstrate that plastic strain diminishes IQA's inhibitory effect on the cathodic hydrogen evolution reaction, facilitating hydrogen diffusion into the steel substrate and thereby exacerbating stress corrosion in J55 steel. Consequently, at low IQA inhibitor concentrations (as in this study, 12.5 mg L−1), despite high average inhibition efficiency, it proves ineffective in mitigating stress corrosion.

Unveiling the inhibition of high-pressure CO2 flow accelerated corrosion at gradual contraction and gradual expansion tubings

The different inhibition behavior of imidazoline quaternary ammonium salt for high-pressure CO2 flow accelerated corrosion of carbon steel gradual contraction and gradual expansion tubings was unveiled combing high pressure dynamic in situ electrochemical methods and microstructure characteristics analysis. It is manifested that there is no noticeable inhibition effect in high CO2 partial pressure environments at extremely low inhibitor concentration. At low inhibitor concentration, the polarization resistance and inhibition efficiency increase firstly and then decrease along the flowing direction of gradual contraction tubing. However, the polarization resistance generally drops along the gradual expansion tubing. As the inhibitor concentration of the corrosion inhibitor is further increased, the polarization resistance and inhibition efficiency are reduced in a whole along the gradual contraction tubing. Nevertheless, the polarization resistance is raised, followed by a fall along the flowing direction of gradual expansion tubing. The inhibition effect at the top and the bottom of gradual contraction tubing exhibits symmetry while it is asymmetrical at the top and the bottom of inclination section in gradual expansion tubing. The distinct inhibition effect at different inhibitor concentration is relevant to flow characteristics of fluid at gradual contraction tubing and gradual expansion tubing. The findings could provide valuable guidance for the protection of flow accelerated corrosion at gradual contraction tubing and gradual expansion tubing under high CO2 partial pressure conditions.

Corrosion resistance of aluminum against acid activation in 1.0 M HCl by symmetrical ball − type zinc phthalocyanine

The inhibition effect of symmetrical Ball − type Zinc Phthalocyanine on Aluminum in 1mol/L hydrochloric acid was analyzed by electrochemical techniques. A novel ball-type zinc phthalocyanine (Zn-Pc) inhibitor has been synthesized and verified utilizing FTIR, nuclear magnetic resonance (1H NMR and 13C NMR), MALDI-TOF MS, and absorption spectroscopy (UV-Vis). In addition, laser-induced breakdown and photoluminescence spectroscopy were employed for additional study. Weight loss technique was employed to investigate the corrosion inhibition effectiveness of the synthesized Zn-Pc on Aluminum in 1mol/L hydrochloric acid at the range of variation temperatures (293–333 K). The inhibition efficiency of Zn-Pc increased with higher concentrations of Zn-Pc and decreased as the temperature increased. Furthermore, Zn-Pc demonstrated outstanding outcomes, achieving 72.9% at a very low inhibitor concentration (0.4 mmol/L) at 298 K. The experimental data for Zn-Pc Aluminum in 1mol/L hydrochloric acid obeys the Langmuir adsorption isotherm. Moreover, the corrosion system’s thermodynamic parameters and activation energy were determined. Quantum chemical calculations applying the (DFT) Density Functional Theory method was conducted and applied in this study. These calculations played a pivotal role in elucidating molecular structures and reactivity patterns. Through DFT, numerous reactivity indicators were computed, providing valuable insights into the chemical behavior of the studied compounds. These indicators, such as frontier molecular orbitals, electron density, and molecular electrostatic potential, were subsequently correlated with experimental data.

IN VITRO STUDY OF THE DOSE-DEPENDENT EFFECT OF JANUS KINASE INHIBITORS

Background. One of the most promising means of targeting the mechanisms of autoimmune processes and hyperimmune reactions associated with cytokine imbalance are Janus kinase inhibitors. However, these chemicals in the used doses have a number of undesirable side effects. The effect of small and ultra-low doses in relation to this group of substances has not been studied. Purpose. To study the effect of low and ultra-low concentrations of Janus kinase inhibitors on the synthesis of cytokines by human mononuclear cells in vitro. Materials and methods. The concentrations of tumor necrosis factor alpha (TNFα), granulocyte-macrophage colony-stimulating factor (GM-CSF), interferon alpha (IFNα), interleukin 2 (IL-2), interleukin 4 (IL-4), interleukin 6 (IL-6), interleukin 8 (IL-8) and interleukin 10 (IL-10) after stimulation with phytohemagglutinin were determined in the culture of mononuclear cells of healthy donors. Also the effect on the production of these cytokines of ruxolitinib and baricitinib in various doses, including ultra-low ones, was determined. Results. It was found that baricitinib, as well as ruxolitinib, at normal concentrations significantly decreased, and at ultra-low concentrations they significantly increased the level of synthesis of all cytokines studied in this experiment. Conclusion. The stimulating, but not suppressive effect of ultra-low concentrations of Janus kinase inhibitors has been demonstrated using the example of ruxolitinib and baricitinib. In relation to inhibitors of Janus kinase functions, this phenomenon has been discovered for the first time, which opens up ways to search for new means of regulating immunity, in particular, the production of cytokines.

Abstract 661: An oral Cbl-b inhibitor with sustained T cell activation demonstrated robust anti-tumor efficacy along with enhanced infiltration and activation of functional T cells

Abstract The E3 ubiquitin ligase Casitas B-lineage lymphoma b (Cbl-b) is a member of the highly conserved family of Cbl (casitas b-lineage lymphoma) proteins, which associates with multi-immune response regulations including Teff and NK activation, Treg differentiation. Cbl-b KO mice showed enhanced immune responses and resistance to tumor transplantation. Previously, we reported a novel Cbl-b inhibitor, ZM-8026, which robustly activated T cells and efficiently inhibited tumor growth as monotherapy or in combination with anti-PD-1. Here, we further demonstrated that Cbl-b inhibition restores the Teff cells' function in immune suppression conditions, such as in the presence of PGE2, A2AR agonist, and TGF-β. CD8+T proliferation and cytokines induction were maintained in the presence of MDSC. Furthermore, CD8+T function was reversed from an exhausting status induced by a continuous anti-CD3/CD28 activation for a long period. To investigate whether continuous target occupancy was necessary for sustained TCR activation, the dynamic impacts of Cbl-b inhibition on CD8+T cell activation were explored using a washout assay. The results showed that the high-level activated T cells lasted for 48 h after more than 4hs preincubation with 1 µM Cbl-b inhibitor followed by a washout, however, short and weak activation states were found with less than 4hs preincubation or low inhibitor concentration treatment (< 0.1 uM). This finding revealed sufficient inhibitor concentration and treatment time ensure high T-cell activation. Further, in vivo efficacy studies demonstrated less anti-tumor growth efficacy for intermittent dosing (Q2D, Q3D) compared with QD dosing. In vitro and in vivo pharmacokinetics studies exhibited favorable ADME profiles and bioavailability of our Cbl-b inhibitor for oral administration in mice, rats, and dogs. At least in two syngeneic models, our Cbl-b inhibitor exhibited efficient anti-tumor growth with more than 70% TGI (tumor growth inhibition). In a CT26 syngeneic model, complete tumor growth inhibition in 6 of 8 mice was found in the Cbl-b inhibitor combined with an anti-PD1 antibody. The complete regression mice were re-challenged with the same tumor cells, and no measurable tumors were found for up to 30 days, suggesting the treatment-induced immune memory. Tumor samples in mice were collected, RNAseq showed that activated functions of tumor-infiltrated T, NK, DC, and macrophage were dramatically increased in the Cbl-b inhibitor treatment group, and the T and NK activation signature genes such as Gzmb, Ifng were significantly upregulated by RT-PCR. In conclusion, our Cbl-b inhibitor exhibited a favorable PK profile in multi-preclinical animals. The sustained T cell activation in vitro was identified and robust anti-tumor growth in vivo was demonstrated with optimized dosing frequency. Citation Format: Feng Zhou, Guimei Yang, Yajing Liu, Liting Xue, Weijie Chen, Zhengtao Li, Xiaowu Liu, Jian Li, Renhong Tang. An oral Cbl-b inhibitor with sustained T cell activation demonstrated robust anti-tumor efficacy along with enhanced infiltration and activation of functional T cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 661.

Biosynthesis of poly(β-L-malic acid) from rubberwood enzymatic hydrolysates in co-fermentation by Aureobasidium pullulans

Co-fermentation of multiple substrates has emerged as the most effective method to improve the yield of bioproducts. Herein, sustainable rubberwood enzymatic hydrolysates (RWH) were co-fermented by Aureobasidium pullulans to produce poly(β-L-malic acid) (PMA), and RWH + glucose/xylose was also investigated as co-substrates. Owing to low inhibitor concentration and abundant natural nitrogen source content of RWH, a high PMA yield of 0.45 g/g and a productivity of 0.32 g/L/h were obtained by RWH substrate fermentation. After optimization, PMA yields following the fermentation of RWH + glucose and RWH + xylose reached 59.92 g/L and 53.71 g/L, respectively, which were 52 % and 36 % higher than that after the fermentation of RWH. RWH + glucose more significantly affected the correlation between PMA yield and substrate concentration than RWH + xylose. The results demonstrated that the co-fermentation of RWH co-substrate is a promising method for the synthesis of bioproducts.

Native ApxIIA secreted by Actinobacillus pleuropneumoniae induces apoptosis in porcine alveolar macrophages dependent on concentration and acylation

Actinobacillus pleuropneumoniae is an important swine respiratory pathogen causing substantial economic losses to the global pig industry. The Apx toxins of A. pleuropneumoniae belong to the RTX toxin family and are major virulence factors. In addition to hemolysis and/or cytotoxicity via pore-forming activity, RTX toxins, such as ApxIA of A. pleuropneumoniae, have been reported to cause other effects on target cells, e.g., apoptosis. A. pleuropneumoniae ApxIIA is expressed by most serotypes and has moderate hemolytic and cytotoxic activities. In this study, porcine alveolar macrophages (3D4/21) were stimulated with different concentrations of purified native ApxIIA from the serotype 7 strain AP76 which only secretes ApxIIA. By observation of nuclear condensation via fluorescent staining and detection of apoptosis and necrosis by flow cytometry, it was found that high and low concentrations of native ApxIIA mainly caused necrosis or apoptosis of 3D4/21 cells, respectively. ApxIIA purified from an AP76 mutant with a deleted acetyltransferase gene (apxIIC) did not induce necrosis nor apoptosis. Western blot analysis using specific antibodies showed that a cleaved caspase 3 and activated capase 9 was detected after treatment of cells with a low concentration of native ApxIIA, while general or specific inhibitors of caspase 3, 8, 9 blocked these effects. ApxIIA-induced apoptosis of macrophages may be a mechanism of A. pleuropneumoniae to escape host immune clearance.

Microwave-assisted cassava pulp hydrolysis as food waste biorefinery for biodegradable polyhydroxybutyrate production.

Cassava pulp is one of the most abundant agricultural residues that can cause serious disposal problems. This study aimed to apply a biorefinery approach by examining the feasibility of microwave-assisted cassava pulp hydrolysis to attain sustainable management and efficient use of natural resources. Four factors, namely, the liquid-to-solid ratio (20mL/g, 10mL/g, 7.5mL/g, and 5mL/g), types of acids (H2SO4 and H3PO4), watt power (600W, 700W, and 800W) and time (3, 5 and 8min), were carefully investigated. The highest fermentable sugar content of 88.1g/L ± 0.7g/L (0.88g fermentable sugars/g dry cassava pulp) was achieved when 20mL/g cassava pulp was hydrolyzed with 2.5% (v/v) H2SO4 under microwave irradiation at 800W for 8min. Glucose was a major product (82.0g/L ± 5.2g/L). The inhibitor concentration was 5.17g/L ± 0.01g/L, and the levulinic acid concentration was 5.15g/L ± 0.01g/L. The results indicated that the liquid-to-solid ratio, diluted acid concentration, irradiation watt power and time were important factors in producing fermentable sugars from acid hydrolysis under microwave irradiation. The crude hydrolysate was used for PHB production by Cupriavidus necator strain A-04. The hydrolysate to nutrients ratio of 30:70 (v/v) yielded a cell dry weight of 7.5g/L ± 0.1g/L containing PHB content of 66.8% ± 0.3% (w/w), resulting in a yield (g-PHB/g- ) of 0.35g/g. This study demonstrated that the microwave-assisted cassava pulp hydrolysate developed in this study provided a high amount of glucose (88.1% conversion) and resulted in a low concentration of inhibitors without xylose; this was successfully achieved without pregelatinization, alkaline pretreatment or detoxification.

Electrochemical, surface analysis, and theoretical investigation of 3-hydroxy-5-(phenylamino)-4-(p-tolyldiazenyl)thiophen-2-yl)(phenyl)methanone as a corrosion inhibitor for carbon steel in a molar hydrochloric acid solution

In this work, a comprehensive study for using (3-hydroxy-5-(phenylamino)-4-(p-tolyldiazenyl)thiophen-2-yl)(phenyl)methanone as a corrosion inhibitor for carbon steel in a 1.0 M HCl was performed. For this purpose, different types of electrochemical and surface analysis techniques as well as a computational simulations have been applied. The obtained experimental results showed that the investigated compound is a promising corrosion inhibitor for carbon steel in acidic environments. Adding a low inhibitor concentration of about 5 × 10−5 M at room temperature resulted in an inhibition efficiency of up to 93.25 %. The inhibition efficiency increases with increasing inhibitor concentration while decreasing with increasing temperature. This trend has been demonstrated and discussed precisely by potentiodynamic polarization (PDP) measurements. SEM and AFM were used to examine the surface morphology of the electrode before and after inhibition. The inhibitor adsorbs on the surface of the steel, acting as a barrier at the steel/HCl acid interface and thus blocking the steel electrode's surface. DFT calculations and MC simulations were used to demonstrate the adsorption process. The findings also revealed that it is a mixed-type inhibitor that follows Henry's adsorption isotherm. The experimental and theoretical studies agree remarkably well. The inhibition mechanism has also been discussed.

On the influence of hydrocarbons solvents on the inhibition efficiency of some organic corrosion inhibitors: Theoretical and validation studies

Injecting inhibitors into industrial equipment and piping systems is an effective way to control corrosion. Before application of corrosion inhibitors on an industrial scale, small scale laboratory testing is necessary to define the performance of inhibitors in specific corrosive media. To achieve low inhibitor concentrations for the laboratory, the inhibitor often needs to be pre-diluted before addition to the corrosive media by solvents. However, corrosion inhibitors may be affected by the solvents used. In this study, some cases that make the researchers get fake results in inhibitor science have been discussed by investigating ten organic compounds in different states (vacuum and solvents). Three hydrocarbon solvents, acetone, benzene, and diethyl ether, were selected. Inhibition performance can be improved by pre-design and theoretical simulations. The Density Functional Theory (DFT) was used in this study. Some physical values were used to find a link between the calculated quantum chemical parameters and the effectiveness of inhibition. The theoretical outcomes were confirmed via experimental tests. The corrosion of aluminum in 1 M HCl in the absence and presence of three hydrocarbon solvents was evaluated. Electrochemical measurements were used to estimate the corrosion parameters. It was found that each solvent affected the corrosion rates. Inhibition efficiencies ranged from 31.43 to 81.42 %. The maximum effect was related to acetone. Furthermore, SEM and AFM techniques were used to determine the effects of solvents. Theoretical and experimental results proved that the solvents used with inhibitors produced fake values of inhibitor efficiency.

Construction of a DNA Nanoassembly Based on Spatially Ordered Recognition Elements for Inhibiting β-Amyloid Aggregation.

A β-amyloid (Aβ) aggregation process is a spontaneous process where the original random coil or helical structure changes into a regularly arranged β-sheet structure. The development of inhibitors with the features of low cost, high efficiency, and biosafety by targeting Aβ self-aggregation is significant for Alzheimer's disease treatment. However, the issues of low inhibition efficiency under low concentrations of inhibitors and biological toxicity are currently to be addressed. To resolve the above problems, a DNA nanoassembly (HCR-Apt) based on spatially ordered recognition elements was constructed by targeted disruption of Aβ ordered arrangement. It was discovered that HCR-Apt could inhibit effectively the fibrillation of Aβ40 monomers and oligomers at substoichiometric ratios. This may be due to orderly arrangement of aptamers in rigid nanoskeletons for enhancing the recognition interaction between aptamers and Aβ40. The strong interaction between HCR-Apt and Aβ40 limited the flexible conformational conversion of Aβ40 molecules, thereby inhibiting their self-assembly. Computational simulations and experimental analysis revealed the interactions of Apt42 with Aβ40, which explained different inhibition effects on the fibrillation of Aβ40 monomers and oligomers. Furthermore, the analysis of tyrosine intrinsic fluorescence spectra and surface plasmon resonance imaging showed that the interaction of HCR-Apt and Aβ40 was stronger than that of Apt42 and Aβ40. These findings contributed to establishing a promising method of boosting the recognition interaction by orderly arrangement of recognition elements. Taken together, this work is expected to provide a simple and efficient strategy for inhibiting Aβ aggregation, expanding aptamer's application potential in neurodegenerative diseases.

Superior Long-Term Corrosion Inhibition of N80 Steel by New Eco-friendly Hydrazone-Based Compounds in a Simulated Oil Well Acidizing Environment: Establishing the Mechanism at the Molecular Level

The acid treatment process of production wells is one of the most acid-induced corrosive processes. Corrosion inhibitors are an effective tool to inhibit the acids employed in acidizing treatments. Herein, new eco-friendly hydrazone-based compounds, namely, 2-(4-isobutylphenyl)-N-((1E,2E)-3-phenylallylidene) propanehydrazide (IPP) and N'-cyclohexylidene-2-[4-(2-methylpropyl)phenyl] propanehydrazide (CIP), were prepared through the functionalization of ibuprofen (IBF) and applied for corrosion mitigation of N80 steel in 15 wt % HCl (referred to hereafter as blank). The anticorrosion performance of selected compounds was investigated by employing weight loss (WL), potentiodynamic polarization curves (PPCs), and electrochemical impedance spectroscopy (EIS), complemented by scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses. In addition, density functional theory-based tight-binding (DFTB) modeling was conducted to get molecular-level insights into inhibitor-metal bonding. Experimental results revealed excellent long-term corrosion inhibition efficiency at very low concentrations of inhibitors and a mixed-type inhibition process. Numerically, N80 steel polarization resistance increased from 5.51 Ω cm2 in blank to 608.4 and 396 Ω cm2 in blank inhibited with 5 × 10-3 mol/L of IPP and CIP, respectively, equivalent to 99% and 98% inhibition efficiency based on EIS experiments. Besides, SEM and AFM images showed that, after addition to 15 wt % HCl, inhibitors could effectively prevent the acid attack on the N80 steel surface. The fitting of experimental data to adsorption isotherms indicated that inhibitors' adsorption followed the Langmuir isotherm model and mixed physicochemical adsorption on the metal surface. The DFTB simulation revealed that inhibitor molecules can create covalent and physical interactions with iron atoms, which is further confirmed by partial density of states (PDOSs) analysis.

GSK3 inhibitor suppresses cell growth and metabolic process in FLT3-ITD leukemia cells

Glycogen Synthase Kinase-3 (GSK-3) was recently implicated in the dysregulated biology of acute myeloid leukemia (AML). Low concentrations of GSK-3 inhibitors, SB216763 and BIO, suppressed the proliferation of AML cells with FLT3-ITD as early as 24 h after treatment. BIO was used in subsequent assays since it exhibited higher inhibitory effects than SB216763. BIO-induced G1 cell cycle arrest by regulating the expression of cyclin D2 and p21 in MV4-11 cells, and promoted apoptosis by regulating the cleaved-caspase3 signaling pathways. In vivo assays demonstrated that BIO suppressed tumor growth, while metabolomics assay showed that BIO reduced the levels of ATP and pyruvate in MV4-11 cells suggesting that it inhibited glycolysis. BIO markedly suppressed cell growth and induced apoptosis of AML cells with FLT3-ITD by partially inhibiting glycolysis, suggesting that BIO may be a promising therapeutic candidate for AML.

Modulation of Ultralarge Immune Complexes in Heparin-Induced Thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is serious prothrombotic disorder in which the target antigen, composed of tetramers of platelet factor 4 (PF4) and heparin or cellular glycosaminoglycans (GAGs), forms ultralarge immune complexes (ULICs) with a subset of anti-PF4 antibodies. ULICs initiate prothrombotic responses in large part by engaging Fcγ receptors on platelets, neutrophils, and monocytes. Contemporary anti-thrombotic therapy for HIT is neither entirely safe nor entirely successful, and acts downstream of ULIC formation and Fcγ receptor-initiated generation of thrombin. Therefore, we asked whether HIT antigen and ULIC formation and stability could be modified to attenuate cellular activation by inhibiting PF4-heparin interactions with fondaparinux in conjunction with disrupting PF4 tetramers with a humanized form of a monoclonal anti-PF4 monomer antibody (hRTO, Figure 1). Using dynamic light scattering to measure HIT antigen (PF4 10 µg/ml and heparin 0.2U/ml) and ULIC (PF4 10 µg/ml, heparin 0.2U/ml, KKO 35µg/ml) size, we found that either fondaparinux (FPX 5-20U/ml) or hRTO (400 - 1000 µg/ml) inhibited formation of HIT antigen and ULIC, and promoted HIT antigen and ULIC disassembly. Successively higher concentrations of hRTO were required as PF4 formed large antigenic complexes and then ULICs, likely because the bonds between PF4 and UFH have been strengthened and access to inhibitors lessened (Figure 1A). Combination of fondaparinux and hRTO was effective below the concentration of either alone (FPX 2.5U/ml + hRTO 330 µg/ml). Importantly, fondaparinux and hRTO blocked Fcγ receptor-dependent induction of factor Xa activity by monocytic THP1 cells and activation of human platelets in whole blood (Figure 1B). When combined with hRTO, fondaparinux inhibited HIT antigen and immune complex formation at concentrations at or below those used clinically to inhibit FXa coagulant activity. Even lower concentrations of inhibitors (FPX < 0.1-0.5 U/ml + hRTO 50 µg/ml) were required to block cell activation than were required to act on ULICs in solution, likely because the affinity of PF4 for GAGs is less than for UFH. These studies show that HIT antigen and immune complexes are dynamic and amenable to modulation. Fondaparinux can be converted from an anticoagulant that acts at a downstream amplification step into a rational, disease-specific intervention that blocks ULIC formation when used in combination with hRTO. Our studies demonstrate that interventions that prevent ULIC formation and stability might increase the efficacy, permit use of lower doses, and shorten the duration of anti-thrombotic therapy and help prevent this serious thrombotic disorder. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

DNA Gyrase Inhibitors Increase the Frequency of Bacteriophage-like RcGTA-Mediated Gene Transfer in Rhodobacter capsulatus.

Rhodobacter capsulatus produces a bacteriophage-like particle called the gene transfer agent (RcGTA) that mediates horizontal gene transfer. RcGTA particles transfer random ~4.5-kb fragments of genomic DNA that integrate into recipient genomes by allelic replacement. This work addresses the effect of sub-inhibitory concentrations of antibiotics on gene transfer by RcGTA. A transduction assay was developed to test the effects of various substances on gene transfer. Using this assay, low concentrations of DNA gyrase inhibitors were found to increase the frequency of gene transfer. Novobiocin was studied in more detail, and it was found that this antibiotic did not influence the production or release of RcGTA but instead appeared to act on the recipient cells. The target of novobiocin in other species has been shown to be the GyrB subunit of DNA gyrase (a heterotetramer of 2GyrA and 2GyrB). R. capsulatus encodes GyrA and GyrB homologues, and a GyrB overexpression plasmid was created and found to confer resistance to novobiocin. The presence of the overexpression plasmid in recipient cells greatly diminished the novobiocin-mediated increase in gene transfer, confirming that this effect is due to the binding of novobiocin by GyrB. The results of this work show that antibiotics affect gene transfer in R. capsulatus and may be relevant to microbial genetic exchange in natural ecosystems.

Smart lignin-based polyurethane conjugated with corrosion inhibitor as bio-based anticorrosive sublayer coating

Incorporating corrosion inhibitors in the formulation of coatings can yield active coatings which are able to provide a sustained release of the corrosion inhibitor in the case of emergence of microcrack in the structure of the coating. Herein, we developed bio-based polyurethane sublayer coatings with strong anticorrosion performances. First, lignin-corrosion inhibitor (LCI) conjugate was obtained through conjugation of nicotinic acid to lignin through hydrolytically cleavable ester linkage to afford the steady release of low concentrations of corrosion inhibitor in case of the emergence of microcracks. Subsequently, solution polyaddition of LCI with diisocyanates and polypropylene glycol and coating on the stainless steel surface afford the polyurethane coatings. Coating with a thickness of 16 µm increased the E corr from − 481 mV (for bare steel) to + 187 mV and reduced both I corr and corrosion rate more than 6700 times. As an added benefit, after creating artificial cracks on the surface of the coating, the release of corrosion inhibitors gradually increased the impedance value, indicating a thin barrier layer has formed within the cracks. • -Lignin-corrosion inhibitor conjugate was prepared as anticorrosive polyol precursor. • -Anticorrosive polyurethane coatings were fabricated based on lignin precursor. • -Thickness of 16 µm of this coating reduce the corrosion rate over 6700 times. • -The corrosion inhibitor released by the coating inhibits corrosion in microcracks.

Valorization of bamboo shoot shell waste for the coproduction of fermentable sugars and xylooligosaccharides.

In this work, hydrothermal pretreatment (autohydrolysis) was coupled with endo-xylanase enzymatic hydrolysis for bamboo shoot shell (BSS) to produce glucose and valuable xylooligosaccharides (XOS) rich in xylobiose (X2) and xylotriose (X3). Results showed that the enzymatic hydrolysis efficiency of pretreated BSS residue reached 88.4% with addition of PEG during the hydrolysis process. To enrich the portions of X2–X3 in XOS, endo-xylanase was used to hydrolyze the XOS in the prehydrolysate, which was obtained at the optimum condition (170°C, 50 min). After enzymatic hydrolysis, the yield of XOS reached 25.6%, which contained 76.7% of X2–X3. Moreover, the prehydrolysate contained a low concentration of fermentation inhibitors (formic acid 0.7 g/L, acetic acid 2.6 g/L, furfural 0.7 g/L). Based on mass balance, 32.1 g of glucose and 6.6 g of XOS (containing 5.1 g of X2-X3) could be produced from 100.0 g of BSS by the coupled technology. These results indicate that BSS could be an economical feedstock for the production of glucose and XOS.

Method Measures Effective Scale-Inhibitor Concentration at Low Detection Limit

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 209503, “A Fast and Accurate Method for Scale-Inhibitor Effective Concentration Measurement With Low Detection Limit,” by Xin Wang, Rice University; Zhaoyi Dai, SPE, China University of Geosciences; and Saebom Ko, Rice University, et al. The paper has not been peer reviewed. _ The accurate measurement of residual scale-inhibitor concentration in produced brine is essential for scale prevention. However, these scale inhibitors are effective at substoichiometric concentrations in most production conditions. It is difficult to measure such low inhibitor concentration with traditional methods, especially for non- or low-phosphorous polymeric scale inhibitors. In the complete paper, an assay method is developed to determine effective scale-inhibitor concentration. The presented assay method is quick, robust, and accurate, with a relative error of less than 10% even at 1 mg/L of inhibitor. Experimental Setup and Methods Brine Chemistry Inhibitor (BCIn) Continuous-Stirred-Tank Reactor (CSTR) Method. The schematic of the BCIn CSTR testing apparatus is shown in Fig. 1. The original supersaturated solution (OSS) with a designated barite scale inhibitor is injected into the reaction vial with no head space. This OSS may contain zero or a certain amount of scale inhibitor, and it will be stirred continuously and kept at room temperature during the whole test period. At Time 0, the cation titrant solution (TC) and the anion titrant solution (TA) start to be pumped continuously into the reaction vial with the same flow rate by using two syringe pumps. A green laser beam (with a wavelength of 532 nm) is shone through the reaction vial; light intensity is recorded continuously as current by using a multimeter with a photodiode detector in real time. The time between Time 0 and the solution turbidity change, which is detected as current drop, is defined as the critical time. Without the supply of scale inhibitor from the TC and TA solutions, the inhibitor concentration in the reaction vial decreases exponentially and the inhibitor concentration at Time t can be calculated. With continuous dilution of the inhibitor and continuous supply of the barite supersaturated solution in the reaction vial by TC and TA solution, the small nuclei and crystals begin to accumulate in the reaction vial, resulting in a turbidity change detected by the laser at the critical time. Because of the exponential decrease of the scale inhibitors, it is observed that, with the same solution composition and residence time, critical time increases linearly with the initial concentration of inhibitor. A series of tests is designed to match the composition of target brine with different amounts of scale inhibitors. The standard curve can then be developed. For the brine with an unknown amount of scale inhibitor, the inhibitor concentration can be calculated from the measured critical time. The known-additions method also can be used to determine the unknown inhibitor concentration in a sample. This process, and its associated equations, is provided in the complete paper, as is sample pretreatment.

Interaction of Venturicidin and Fo·F1-ATPase/ATP Synthase of Tightly Coupled Subbacterial Particles of Paracoccus denitrificans in Energized Membranes.

Proton-translocating Fo×F1-ATPase/synthase that catalyzes synthesis and hydrolysis of ATP is commonly considered to be a reversibly functioning complex. We have previously shown that venturicidin, a specific Fo-directed inhibitor, blocks the synthesis and hydrolysis of ATP with a significant difference in the affinity [Zharova, T. V. and Vinogradov, A. D. (2017) Biochim. Biophys. Acta, 1858, 939-944]. In this paper, we have studied in detail inhibition of Fo×F1-ATPase/synthase by venturicidin in tightly coupled membranes of Paracoccus denitrificans under conditions of membrane potential generation. ATP hydrolysis was followed by the ATP-dependent succinate-supported NAD+ reduction (potential-dependent reverse electron transfer) catalyzed by the respiratory chain complex I. It has been demonstrated that membrane energization did not affect the affinity of Fo×F1-ATPase/synthase for venturicidin. The dependence of the residual ATP synthase activity on the concentration of venturicidin approximated a linear function, whereas the dependence of ATP hydrolysis was sigmoidal: at low inhibitor concentrations venturicidin strongly inhibited ATP synthesis without decrease in the rate of ATP hydrolysis. A model is proposed suggesting that ATP synthesis and ATP hydrolysis are catalyzed by two different forms of Fo×F1.