Cationic Inhibitors Research Articles

The efficiency of protection of structural steel by cationic inhibitor under conditions of corrosion with bacterial sulfate reduction

The effectiveness of protecting a structural steel by cationic inhibitor against biocorrosion caused by Desulfovibrio sp. М-4.1, Desulfomicrobium sp. TC 4, and sulfidogenic microbial communities was investigated by using gravimetric and electrochemical methods. The research showed that at a concentration of 1 g/l, the inhibitor offers greater protection to steel St3ps against Desulfomicrobium sp. TC 4 (up to 81.0%) than to Desulfovibrio sp. М-4.1 (up to 72.2%). The structure of the molecules of the inhibitor's compounds determines their ability to form a protective layer on the surface of the metal and exhibit antimicrobial action to sulfate-reducing bacteria and their satellites (iron-reducing bacteria). The inhibitor provides a high degree of protection (>92.9%) in microbial corrosion under the influence of sulfidogenic microbial communities. The cationic inhibitor was shown to have a greater effect on the electrochemical performance of the corrosion process for the biofilm form of sulfate-reducing bacteria than for the planktonic form.

Allosteric regulation of α-amylase induced by ligands binding

The conformational changes in α-amylase induced by different ligands, including metal ions, substrates, and aromatic compounds in liquor production, were systematically studied using spectroscopy. Fluorescence acrylamide quenching analysis showed that the interaction with active metal cations (K+, Na+, and Ca2+) led to higher exposure of the active sites in α-amylase. In contrast, interactions with substrates (soluble starch, amylose, amylopectin, wheat starch, and dextrin) reduced the degree of exposure of active sites, and the conformation of the enzyme became more rigid and compact. Although the interaction with inhibitory metal cations (Mg2+, Zn2+) and aromatic compounds generated in the brewing process (guaiacol, eugenol, thymol, and vanillin) increased the exposure of active site with a relatively low amplitude, it reduced the enzymatic activity. This finding may be due to the overall structure of the enzyme becoming looser. Structural stability showed that the active cations and substrates increased the stability of the secondary structure of the α-amylase backbone, whereas the inhibitory cations and aromatic compounds reduced the stability of the backbone but increased the compact of domain A and B. Enzymatic assays and molecular docking experiments strongly supported these conclusions. The experimental results may provide a valuable reference for controlling related conditions and improving production efficiency.

Inhibition mechanism of cationic polyacrylamide on montmorillonite surface hydration: A molecular dynamics simulation study

Cationic polyacrylamide (CPAM), a typical drilling fluid shale inhibitor can prevent the clay swelling and maintain the wellbore stable. Understanding the adsorption behavior of CPAM on montmorillonite (MMT) surfaces is of great significance in explaining the excellent performance of cationic inhibitors. In this work, molecular dynamic simulations (MD) are applied to investigate the adsorption mechanism of CPAM on the Na-MMT surface. The simulation results show that there are two main adsorption configurations of CPAM: 1) trimethylamine group adsorption; 2) the co-adsorption of trimethylamine group and amide group, the latter has stronger interaction energy, also trimethylamine group accounted for a large proportion of the interaction energy. The CPAM coating will decrease the H-bond number, neutralize the negative charge of Na-MMT surface and weaken the surface hydration ability of Na-MMT. Due to the existence of the CPAM coating, the diffusion and transport ability of water molecules on Na-MMT surface are greatly reduced. This study provides a theoretical explanation for the coating-forming mechanism and adsorption characteristics of CPAM inhibitors on Na-MMT surfaces and may shed light on the design of high-performance water-based drilling fluid systems.

Dissecting the Nucleoside Antibiotics as Universal Translation Inhibitors.

Without question, natural products have provided the lion share of leads, if not drugs themselves, for the treatment of bacterial infections. The bacterial arms race, fueled by selection and survival pressures has delivered a natural arsenal of small molecules targeting the most essential of life processes. Antibiotics that target these critical intracellular processes face the formidable defense of both penetrating a bacterial cell membrane and avoiding efflux to exert their effect. These challenges are especially effective in Gram-negative (Gram-(-)) bacteria, which have a double membrane structure and efficient efflux systems from the combination of outer-membrane porins and inner membrane proton pumps. In this landscape of offense and defense, our clinically used antibiotics have only successfully targeted three intracellular processes for therapeutic intervention in Gram-(-) bacteria: dihydrofolate biosynthesis, transcription, and translation. Not surprisingly, such critical survival machinery is a popular target for bacterial warfare, and eight of our 14 classes of commonly used antibiotics target translation with the bacterial ribosome remaining one the most vetted targets for antimicrobial therapy. On the plus side, its anionic character attracts cationic inhibitors, which are generally more capable of penetrating the bacterial cell wall, and clinical resistance rates are usually manageable as mutation of such a highly evolved machine is difficult. On the down side, this highly evolved machine renders it difficult to inhibit selectively, and the inhibition of prokaryotic translation versus both eukaryotic cellular and mitochondrial translation is critical for clinical development and minimization of undesired toxicities.A class of natural products known as the "nucleoside antibiotics" have historically been recognized as universal inhibitors of the ribosome and can inhibit translation in prokaryotes, eukaryotes, and archaea. While they have served an essential role in dissecting the biochemical underpinnings of the enzymatic functions of the ribosome, they have not proven therapeutically useful as they target the highly conserved rRNA in the P-site and are toxic to mammalian cells. In this Account, we describe our studies on the natural product amicetin, a nucleoside antibiotic that we have demonstrated to break the rule of being a universal translation inhibitor. While the cytosine of amicetin mimics C75 of the 3'-CCA tail of the P-site tRNA akin to other nucleoside antibiotics, we advance a hypothesis that amicetin's unique interaction with the ribosomal protein uL16 exploits an untapped mechanism for selectively targeting the bacterial ribosome. A complex molecule comprised of a nucleoside, carbohydrates and amino acids, amicetin is also chemically unstable. Our initial attempts to stabilize and simplify this scaffold are presented with the ultimate goal of rebuilding the compound with improved penetrance to bacterial cells. If successful, this scaffold would demonstrate a path forward for a new class of antibiotics capable of selectively targeting the ribosomal P-site.

Expired food products and used disposable adult nappies mesophilic anaerobic co-digestion: Biochemical methane potential, feedstock pretreatment and two-stage system performance

Used absorbent hygiene products are complex materials (only partially biodegradable) that constitute a significant percentage of municipal solid wastes ending up in landfills. At the same time, food wastes disposed of in landfills have a major contribution to greenhouse gas emissions. In this study, the authors propose the separation of the biodegradable part of used disposable adult nappies and its co-digestion with expired food products, originating from supermarkets. Three different pretreatment schemes were examined, with the meat waste pasteurization treatment scenario leading to the recovery of 427 kJ/Lfeed, while acid hydrolysis and intense thermal treatment led to a reduction of the recovered energy by 25.5 and 49.4% respectively, even though the hydrogen production, after acid hydrolysis, is almost 2 times higher compared to the other pretreatment schemes. This was caused by impeded methanogenic reactor operation, probably triggered by inhibitory cation concentrations and complex compounds. Finally, the methanogenic reactor during two-stage system operation, with meat pasteurization, was capable of operating with an HRT of 10.6 d, with 67% COD reduction, from an initial feedstock COD of 42 g/L. The reduction of HRT from 20 to 10.6 d exhibited an insignificant effect in specific (per LFeed) methane production.

KLR-70: A Novel Cationic Inhibitor of the Bacterial Hsp70 Chaperone.

The heat-shock factor Hsp70 and other molecular chaperones play a central role in nascent protein folding. Elucidating the task performed by individual chaperones within the complex cellular milieu, however, has been challenging. One strategy for addressing this goal has been to monitor protein biogenesis in the absence and presence of inhibitors of a specific chaperone, followed by analysis of folding outcomes under both conditions. In this way, the role of the chaperone of interest can be discerned. However, development of chaperone inhibitors, including well-known proline-rich antimicrobial peptides, has been fraught with undesirable side effects, including decreased protein expression yields. Here, we introduce KLR-70, a rationally designed cationic inhibitor of the Escherichia coli Hsp70 chaperone (also known as DnaK). KLR-70 is a 14-amino acid peptide bearing naturally occurring residues and engineered to interact with the DnaK substrate-binding domain. The interaction of KLR-70 with DnaK is enantioselective and is characterized by high affinity in a buffered solution. Importantly, KLR-70 does not significantly interact with the DnaJ and GroEL/ES chaperones, and it does not alter nascent protein biosynthesis yields across a wide concentration range. Some attenuation of the anti-DnaK activity of KLR-70, however, has been observed in the complex E. coli cell-free environment. Interestingly, the d enantiomer D-KLR-70, unlike its all-L KLR-70 counterpart, does not bind the DnaK and DnaJ chaperones, yet it strongly inhibits translation. This outcome suggests that the two enantiomers (KLR-70 and D-KLR-70) may serve as orthogonal inhibitors of chaperone binding and translation. In summary, KLR-70 is a novel chaperone inhibitor with high affinity and selectivity for bacterial Hsp70 and with considerable potential to help in parsing out the role of Hsp70 in nascent protein folding.

Investigation of the corrosion inhibition performances of various inhibitors for carbon steel in CO2 and CO2/H2S environments

ABSTRACT The corrosion inhibition performances of thiourea (TU), l-cysteine (CYS), sodium dodecyl sulfonate (SDS), tetradecyl trimethyl ammonium bromide (TTAB), N-benzyl pyridinium chloride (BPC) and imidazoline quaternary ammonium salt (IAS) in CO2-saturated and CO2/H2S coexistent brine solutions were investigated by electrochemical measurement, weight-loss test, molecular dynamics simulation and SEM observation. The results show that H2S can remarkably affect the adsorption of some inhibitors on the steel surface and the inhibition performance. In detail, the inhibition performances of TU, CYS and SDS, which are effective in the CO2 environment, deteriorate in the CO2/H2S environment. However, the cationic inhibitors (TTAB, BPC and IAS) exhibit good inhibition performance in the CO2/H2S environment possibly because of a relatively strong interaction between inhibitor cations and HS− ions. The finding of this study delivers a provable method to predict the performance of inhibitors in the aggressive solution containing H2S.

Synergistic effect of the bromide and chloride ion on the inhibition of quaternary ammonium salts in haloid acid, corrosion inhibition of carbon steel measured by weight loss

Four quaternary quinolinium inhibitors were synthesized and characterized to investigate the synergistic effect of bromide or chloride anion for protecting the steel in acid corrosive medium. The inhibition was studied through gravimetric method in 4.410 M HCl and 4.410 M HBr and the results were confirmed by molecular dynamics stimulation. It is confirmed that Br− exhibits a better synergistic effect than Cl− and therefore the cationic inhibitor is much easier to get saturate adsorbed to show a better inhibition in HBr. Inhibitors with the same cation moiety can be fastened tightly and thus be able to experience chemisorption in HBr, while physisorption is the dominating mechanism in HCl.

Ocean acidification: synergistic inhibitory effects of protons and heavy metals on 45Ca uptake by lobster branchiostegite membrane vesicles.

Previous work with isolated outer membrane vesicles of lobster branchiostegite epithelial cells has shown that 45Ca2+ uptake by these structures is significantly (p < 0.02) reduced by an incremental decrease in saline pH (increased proton concentration) and that this decrease is due to competitive inhibition between carrier-mediated transport of 45Ca2+ and hydrogen ions. The present paper extends these previous findings and describes the combined effects of pH and cationic heavy metals on branchiostegite uptake of 45Ca2+. Partially purified membrane vesicles of branchiostegite cells were produced by a homogenization/centrifugation method and were loaded with mannitol at pH 7.0. The time course of 1mM 45Ca2+ uptake in a mannitol medium at pH 8.5 containing 100µM verapamil (Ca2+ channel blocker) was hyperbolic and approached equilibrium at 30min. This uptake was either significantly reduced (p < 0.05) by the addition of 5µM Zn2+ or essentially abolished with the addition of 5µM Cu2+. Increasing zinc concentrations (5-500µM) reduced 1mM 45Ca2+ uptake at pH 8.5 or 7.5 in a hyperbolic fashion with the remaining non-inhibited uptake due to apparent non-specific binding. Uptake of 1mM 45Ca2+ at pH 8.5, 7.5, 7.5 + Zn2+, and 7.5 + Zn2+ + Cu2+ + Cd2+ in the presence of 100µM verapamil displayed a stepwise reduction of 45Ca2+ uptake with the addition of each treatment until only non-specific isotope binding occurred with all cation inhibitors. 45Ca2+ influxes (15s uptakes; 0.25-5.0mM calcium + 100µM verapamil) in the presence and absence of 10µM Zn2+ were both hyperbolic functions of calcium concentration. The curve with Zn2+ displayed a transport Km twice that of the control (p < 0.05), while inhibitor and control curve Jmax values were not significantly different (p > 0.05), suggesting competitive inhibition between 45Ca2+ and Zn2+ influxes. Analysis of the relative inhibitory effects of increased proton or heavy metal interaction with 45Ca2+ uptake suggests that divalent metals may reduce the calcium transport about twice as much as a drop in pH, but together, they appear to abolish carrier-mediated transport.

Epoxy-polyamide nanocomposite coating with graphene oxide as cerium nanocontainer generating effective dual active/barrier corrosion protection

An epoxy-polyamide composite coating with dual active/barrier corrosion protection capabilities was formulated using graphene oxide (GO) as a gallery for storage and targeted release of cerium cation inhibitors by an ion exchange mechanism on the steel corrosion sites. The successful adsorption of cerium cations over the GO nanosheets was detected via SEM, TGA and Raman spectroscopy. The role of Ce-GO in the barrier properties and active inhibition was evidenced through EIS assessment of polymeric coatings with and without an artificial scratch. SEM/EDS analysis of the scratch region indicated formation of a protective layer resulting from release of Ce component from the nanocontainer.

Effect of an activated charcoal product (DOAC Stop™) intended for extracting DOACs on various other APTT-prolonging anticoagulants.

Background The aim of the study was to investigate the specificity of an activated charcoal-based product (DOAC Stop™) initially intended for the specific extraction of direct oral anticoagulants (DOACs) from test plasmas on a range of other anticoagulants. Methods Test plasmas were prepared by adding various anticoagulants to pooled normal plasma at concentrations prolonging an activated partial thromboplastin time (APTT) test by a factor of 1.5-3. These plasmas were treated with DOAC Stop™ for 5 and 20 min. Then APTTs were repeated and residual anticoagulant concentrations estimated from dose-response curves. Results The activated charcoal (AC)-based product was found to extract DOACs efficiently. It also bound the intravenous anticoagulants argatroban and lepirudin, but it had no effect on heparin, enoxaparin or danaparoid in plasma. Among other APTT-inhibiting agents that might be present in test plasmas from patients, it extracted protamine, aprotinin and polymyxin. It had no effect on annexin V, thrombomodulin, a typical lupus anticoagulant, a factor VIII antibody, activated protein C or its activator, but it did bind some cationic inhibitors of the APTT with molecular weight below approximately 30 kDa. Conclusions The AC-based product extracted DOACs efficiently with no effect on heparin-type anticoagulants. It did bind argatroban and hirudin-type anticoagulants, which might occur in plasmas from some inpatients, and APTT results obtained after its use should be interpreted after due consideration of patient medications.

Abstract 4916: OCT and MATE transporters mediate uptake and antiproliferative activity of the anticancer drug metformin in endometrial cancer cell lines

Abstract Purpose Metformin, a first-line drug for treatment of Type 2 diabetes, is effective against multiple type of cancers including endometrial cancer. The anticancer effects of metformin, in part, are mediated via activation of its intracellular target adenosine monophosphate-activated protein kinase (AMPK) and subsequent modulation of the downstream signaling of Mammalian Target of Rapamycin (mTOR) and P70S6K. Since metformin is positively charged (pKa 12.4) and hydrophilic (logD -6.13 at pH 6.0) it requires organic cation transporters (OCT) 1-3, plasma membrane monoamine transporter (PMAT) and multidrug and toxin extrusion transporters (MATE) 1 and 2 to mediate its cellular uptake/egress. The goal of this study is to assess the expression of these transporters in the endometrial cancer (EC) cell lines ECC-1, Ishikawa and SPEC-2. Methods EC cells (ECC-1, Ishikawa and SPEC-2) were treated with varying concentrations (0.1 mM-100 mM) of metformin for 72 hours, cell proliferation was assessed by MTT assay. Cellular uptake (5 min) of [14C] metformin at 50μM concentration was measured in the presence or absence of cation-selective transporter inhibitors, 1-methyl-4-phenylpyridinium (MPP+) (500 μM), desipiramine (200 μM) and pyrimethamine (2.4 μM). Expression of 6 cation-selective transporters (OCT 1-3, MATE1, MATE2 and PMAT) and phosphorylation of AMPK and P70S6K was evaluated by Western blot analysis. Results Metformin exhibited dose-dependent anti-proliferative activity against ECC-1, Ishikawa and SPEC-2 cell lines with an IC50 of 4.3, 2.2 and 8.8mM respectively. Protein expression analysis showed that OCT 1-3 were highly expressed in ECC-1 and Ishikawa cells whereas MATE1 and 2 were the predominant in SPEC-2 cells. [14C] metformin uptake into these 3 cell lines was mediated by cation-selective transporters as evidenced by the observation that &amp;gt;80% uptake was inhibited by the pan cation inhibitors MPP+ (500 μM). In the ECC-1 and Ishikawa cell lines, ≈50% of [14C]metformin uptake was inhibited by OCT1-3 and PMAT inhibitor desipiramine (200 μM) and ≈50% of uptake was inhibited by MATE1 and 2 inhibitor pyrimethamine (2.4 μM). In contrast, pyramithamine inhibited 72% of [14C]metformin uptake in SPEC-2 cells. Western blot analysis revealed that 5 µM pyrimethamine reversed metformin-mediated phosphorylation of AMPK and inhibition of pP70S6K in all the EC cell lines. Discussion Our results demonstrate that the OCT 1-3 and MATE 1-2 transporters play an approximately equal role in the uptake of metformin in ECC-1 and Ishikawa cells, whereas MATE 1-2 play a major role in metformin uptake into the SPEC-2 cells. As expected, metformin promoted phosphorylation of AMPK (activation) and attenuated phosphorylation of P70S6K (inhibition) in all of the EC cell lines. This work highlights the importance of transporters in the anti-proliferative activity of metformin in EC cells. Citation Format: Aruljothi Muralidharan, Victoria L. Bae-Jump, Dhiren R. Thakker. OCT and MATE transporters mediate uptake and antiproliferative activity of the anticancer drug metformin in endometrial cancer cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4916.

Montmorillonite nanoclay-based self-healing coatings on AA 2024-T4

Cation-exchanged montmorillonite (MMT), which is an aluminum-pillared clay, was dispersed into an organic–inorganic hybrid silica matrix sol. Cationic inhibitors Ce3+/Zr4+ were introduced into montmorillonite by two methods, namely (1) physical mixing of MMT with the inhibitor solutions and (2) physical mixing for short durations and evacuation of the mixture of MMT and inhibitor solutions. Coatings using these sols were deposited on aluminum alloy AA 2024-T4 substrates, by the dip coating technique followed by thermal curing at 130°C for 1 h. TEM, BET, and XRD analyses were carried out for the inhibitor-modified montmorillonite powders. Potentiodynamic polarization and electrochemical impedance spectroscopic analyses were carried out on uncoated and coated substrates to evaluate the corrosion protection property after exposure to 3.5 wt% NaCl for varying time durations, up to 120 h. Self-healing ability was evaluated using SVET analysis by creating an artificial scribe on the surface and exposure to 3.5 wt% NaCl. Elemental mapping was carried out on scribed substrates before and after exposure to 5 wt% salt fog. Sols containing montmorillonite intercalated with cationic inhibitors when deposited on AA 2024-T4 substrates exhibited low corrosion currents after a prolonged duration of exposure to corrosion medium.

Inhibition of trypanosome alternative oxidase without its N-terminal mitochondrial targeting signal (ΔMTS-TAO) by cationic and non-cationic 4-hydroxybenzoate and 4-alkoxybenzaldehyde derivatives active against T. brucei and T. congolense

African trypanosomiasis is a neglected parasitic disease that is still of great public health relevance, and a severe impediment to agriculture in endemic areas. The pathogens possess certain unique metabolic features that can be exploited for the development of new drugs. Notably, they rely on an essential, mitochondrially-localized enzyme, Trypanosome Alternative Oxidase (TAO) for their energy metabolism, which is absent in the mammalian hosts and therefore an attractive target for the design of safe drugs. In this study, we cloned, expressed and purified the physiologically relevant form of TAO, which lacks the N-terminal 25 amino acid mitochondrial targeting sequence (ΔMTS-TAO). A new class of 32 cationic and non-cationic 4-hydroxybenzoate and 4-alkoxybenzaldehyde inhibitors was designed and synthesized, enabling the first structure-activity relationship studies on ΔMTS-TAO. Remarkably, we obtained compounds with enzyme inhibition values (IC50) as low as 2 nM, which were efficacious against wild type and multidrug-resistant strains of T. brucei and T. congolense. The inhibitors 13, 15, 16, 19, and 30, designed with a mitochondrion-targeting lipophilic cation tail, displayed trypanocidal potencies comparable to the reference drugs pentamidine and diminazene, and showed no cross-resistance with the critical diamidine and melaminophenyl arsenical classes of trypanocides. The cationic inhibitors 15, 16, 19, 20, and 30 were also much more selective (900 - 344,000) over human cells than the non-targeted neutral derivatives (selectivity >8-fold). A preliminary in vivo study showed that modest doses of 15 and 16 reduced parasitaemia of mice infected with T. b. rhodesiense (STIB900). These compounds represent a promising new class of potent and selective hits against African trypanosomes.

Adaptability of Polymer-Containing Sewage Corrosion Inhibitor

The polymer content in the produced water from Tuoliu Station is about 20 mg/L. Cationic imidazoline-type corrosion inhibitor is used to corrosion control of sewage. The corrosion inhibitor can react with the negatively charged materials such as anionic polymer and suspended substance by adsorption and merging to form complex aggregates, so that the suspended solids content increases, resulting in suspended solids content of exported sewage has been high. So a new type of non-ionic corrosion inhibitor has been developed and field trials have been performed. The results show that non-ionic corrosion inhibitor can effectively reduce the suspended solids content of wastewater while ensuring the corrosion rate of wastewater.

Laser beam backscattering as a new tool to study the effect of inhibitors on shale particles-water interactions: A real-time analysis

The interaction between clay-rich shales formations and water is one of the most relevant factors for well instability in drilling operations, representing a significant challenge for the oil and gas industry. To minimize the problems related to water sensitivity, chemical additives or inhibitors are incorporated into water-based drilling fluids, acting over the water-shale interactions and maintaining the integrity of the sedimentary rock. In this work a novel approach is proposed to gain new information about the dynamics of the inhibitory process and to evaluate the shale inhibition efficiency of different chemical additives using a laser beam backscattering technique. This technique is based on the analysis of laser backscattering profiles promoted by dispersed particles in a suspension, which results in a particle chord length distribution (CLD). The technique was adequate for monitoring the consequences of the interactions between water and shales, differentiating its reactivities by monitoring the effect of different inhibitors on each system's CLD over time. Two cationic inhibitors (KCl and PDADMAC, a cationic polymer) were tested, and the obtained results showed that the inhibition phenomenon is more than the inhibitor itself, and it depends on the shale structure and the capability of the inhibitor to interact with its clay stacks. A methodology was also developed to calculate an inhibition efficiency score (IES), in which the technique's real-time factor enables it to estimate how much better an inhibitor is when compared to others over time. Among the evaluated systems, the inhibitor that achieved the biggest efficiency for shale was KCl, resulting in 69%.

High-voltage electrostatic fields increase nitrogen uptake and improve growth of tomato seedlings&#x0D;

High-voltage electrostatic fields (HVEFs) can increase the nitrogen uptake of plants. An ammonium cation inhibitor, tetraethylammonium chloride, and a nitrate ion inhibitor, 5-nitro-2-(3-phenylpropylamino)-benzoate, were added to ammonium and nitrate growing solutions with and without exposure to HVEFs to investigate the effects of these fields on tomato seedlings. The seedlings were exposed to HVEFs with field intensities of 2.25 and 2.5 kV cm−1, respectively, for 8 h and the dynamic absorption of nitrogen ions was comparatively analyzed. The seedlings exposed to HVEFs were planted in a greenhouse, the diameter and length of their stems were measured after a 20-d growth period, and their fruit yield was recorded after harvest. Results demonstrated that HVEFs with field intensities of 2.25 and 2.5 kV cm−1 could respectively improve the dynamic absorption of NH4+ and NO3− by the hydroponically grown tomato seedlings. Many channel proteins were also activated by HVEFs as nitrogen uptake increased. HVEF trea...

Nanoclay-based self-healing, corrosion protection coatings on aluminum, A356.0 and AZ91 substrates

Investigations were carried out to explore the feasibility of using Ce3+/Zr4+ encapsulated in environmental friendly nanoclay containers for prolonged corrosion protection of pure aluminum, aluminum alloy A356.0 and Mg alloy AZ91. Dimensions of clay nanotubes were studied using SEM and TEM analysis. They were subjected to pore volume and surface area analysis to confirm the loading of inhibitor into their lumen. The smart nanocontainers loaded with active cationic inhibitor were dispersed in an organic–inorganic hybrid sol–gel matrix synthesized from the hydrolysis and condensation of glycidoxypropyltrimethoxysilane and tetraethoxysilane. The loading of nanocontainers in the matrix sol was optimized. Coatings were generated on pure Al, A356.0, AZ91 substrates using a dip-coating technique and cured at 130°C for 1 h in air. The coated substrates were characterized for their corrosion resistance using potentiodynamic polarization and electrochemical impedance spectroscopic analysis by exposing them to 3.5 wt% NaCl solution for time intervals varying from 1 to 120 h. Micro-Raman spectroscopic studies were carried out to analyze the chemical composition of phases in the scribed area after exposure to corrosive medium. A few coated aluminum substrates were subjected to scanning vibrating electrode technique experiments to study the self-healing mechanism.

Alteration of blood clotting and lung damage by protamine are avoided using the heparin and polyphosphate inhibitor UHRA

AbstractAnticoagulant therapy–associated bleeding and pathological thrombosis pose serious risks to hospitalized patients. Both complications could be mitigated by developing new therapeutics that safely neutralize anticoagulant activity and inhibit activators of the intrinsic blood clotting pathway, such as polyphosphate (polyP) and extracellular nucleic acids. The latter strategy could reduce the use of anticoagulants, potentially decreasing bleeding events. However, previously described cationic inhibitors of polyP and extracellular nucleic acids exhibit both nonspecific binding and adverse effects on blood clotting that limit their use. Indeed, the polycation used to counteract heparin-associated bleeding in surgical settings, protamine, exhibits adverse effects. To address these clinical shortcomings, we developed a synthetic polycation, Universal Heparin Reversal Agent (UHRA), which is nontoxic and can neutralize the anticoagulant activity of heparins and the prothrombotic activity of polyP. Sharply contrasting protamine, we show that UHRA does not interact with fibrinogen, affect fibrin polymerization during clot formation, or abrogate plasma clotting. Using scanning electron microscopy, confocal microscopy, and clot lysis assays, we confirm that UHRA does not incorporate into clots, and that clots are stable with normal fibrin morphology. Conversely, protamine binds to the fibrin clot, which could explain how protamine instigates clot lysis and increases bleeding after surgery. Finally, studies in mice reveal that UHRA reverses heparin anticoagulant activity without the lung injury seen with protamine. The data presented here illustrate that UHRA could be safely used as an antidote during adverse therapeutic modulation of hemostasis.

An Exploration of Charge Compensating Ion Channels across the Phagocytic Vacuole of Neutrophils

Neutrophils phagocytosing bacteria and fungi exhibit a burst of non-mitochondrial respiration that is required to kill and digest the engulfed microbes. This respiration is accomplished by the movement of electrons across the wall of the phagocytic vacuole by the neutrophil NADPH oxidase, NOX2. In this study, we have attempted to identify the non-proton ion channels or transporters involved in charge compensation by examining the effect of inhibitors on vacuolar pH and cross-sectional area, and on oxygen consumption. The chloride channel inhibitors 4-[(2-Butyl-6,7-dichloro-2-cyclopentyl-2,3-dihydro-1-oxo-1H-inden-5-yl)oxy]butanoic acid (DCPIB) and flufenamic acid (FFA) were the most effective inhibitors of alkalinisation in human neutrophil vacuoles, suggesting an efflux of chloride from the vacuole. The proton channel inhibitor, zinc (Zn2+), combined with DCPIB caused more vacuolar swelling than either compound alone, suggesting the conductance of osmotically active cations into the vacuole. Support for cation influx was provided by the broad-spectrum cation transport inhibitors anandamide and quinidine which inhibited vacuolar alkalinisation and swelling when applied with zinc. Oxygen consumption was generally unaffected by these anion or cation inhibitors alone, but when combined with Zn2+ it was dramatically reduced, suggesting that multiple channels in combination can compensate the charge. In an attempt to identify specific channels, we tested neutrophils from knock-out mouse models including CLIC1, ClC3, ClC4, ClC7, KCC3, KCNQ1, KCNE3, KCNJ15, TRPC1/3/5/6, TRPA1/TRPV1, TRPM2, and TRPV2, and double knockouts of CLIC1, ClC3, KCC3, TRPM2, and KCNQ1 with HVCN1, and humans with channelopathies involving BEST1, ClC7, CFTR, and MCOLN1. No gross abnormalities in vacuolar pH or area were found in any of these cells suggesting that we had not tested the correct channel, or that there is redundancy in the system. The respiratory burst was suppressed in the KCC3-/- and enhanced in the CLIC1-/- cells, but was normal in all others, including ClC3-/-. These results suggest charge compensation by a chloride conductance out of the vacuole and by cation/s into it. The identity of these channels remains to be established.