Cationic Acid Research Articles

Carbonate Associated Sulfate Extraction Method Using Weakly Acidic Cation Exchange Resins

The sulfur (S) mass fraction of carbonate minerals can be used to reconstruct the environmental conditions and S sources at the time of precipitation. As S is present in a wide range of host materials, there is an urgent need to develop a method to extract S from a single mineral phase. We have developed a method to extract structurally substituted sulfate, termed carbonate‐associated sulfate (CAS), from geological and biogenic carbonate minerals using weakly acidic cation exchange resins. Two types of weakly acidic cation exchange resin (methacrylic acid and acrylic acid types) were tested to minimise the blank S contents and decompose carbonate. After repeated cleaning of the resins with high‐purity water or HCl, the blank S contents were reduced to < 0.1 μg, which is < 0.1% of the CAS in the samples. The cleaned resin was used to dissolve 10 and 25 mg of the JCp‐1 carbonate certified reference material (CRM; Japanese National Institute of Advanced Industrial Science and Technology, AIST). Samples and resin were added to 8 ml of high‐purity water at resin/sample ratios of 2, 5, 10 and 20, set on a shaking table, and reacted. The supernatant solutions were sampled sequentially from 0.5 h to 87 h after the start of experiments. The results show that the optimal conditions for decomposing 10 mg of carbonate is a resin/sample ratio of ≥ 10 with a reaction time of ≥ 40 h. Carbonate‐associated S mass fractions were measured for six geological and biogenic carbonate CRMs. The coefficient of variation in carbonate‐associated S mass fractions was ≤ 7%, regardless of the type of resins used. The mass fractions determined with this method recover 74–94% of the total S mass fractions reported in previous studies, suggesting that this method dissolved carbonate, and did not leach other S‐bearing fractions that are not resistant to weak acids. Another benefit of this method is that the decomposed solution can be introduced directly into the ion chromatograph, allowing for more sensitive analyses. We emphasise that this method can also be used for S isotopic measurements, as S contamination from other S‐bearing mineral phases is low.

Metabolomic profiling and quantification of polyphenols from leaves of seven Acacia species by UHPLC-QTOF-ESI-MS

The genus Acacia (Fabaceae) comprises >1350 species and has been used in traditional medicine as infusions and decoctions to treat wounds, sores, headaches, diarrhea, and cough. The leaf methanolic extracts of seven Acacia species growing in Egypt namely: Acacia saligna, Acacia seyal, Acacia xanthophloea, Acacia tortilis subsp. raddiana., Acacia tortilis, Acacia laeta, Acacia albida were analyzed using UPLC-QTOF-ESI-MS. A total of 37 polyphenols were identified and discussed in detail. They included phenolic acids, flavonoids, and procyanidins, among which sixteen polyphenols were identified in Acacia for the first time. Folin-ciocalteau assay and ferric reducing antioxidant power, cupric reducing antioxidant capacity, 2,20 -azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) cation radical and the scavenging capacity against 2,2-diphenyl-1- picrylhydrazyl radical were performed to investigate the total phenolic content and the antioxidant activity of the Acacia extracts, respectively. Furthermore, the absolute quantification of eighteen polyphenols common to most of the species was performed using UPLC-MS. It was evident that the differences in the chemical composition among the species accounted for the difference in antioxidant activity which was in line together with the total phenolic content.

A novel hollow CuMn-PBA@NiCo-LDH nanobox for efficient detection of glucose in food

Designing a rapid and sensitive glucose detection method is of great significance to public health. Herein, hollow CuMn-PBA@NiCo-LDH nanoboxes (CuMn-PBA@NiCo-LDH NBs) were prepared using acid etching, cation exchange, and reflux method. The modified electrode exhibited outstanding electrocatalytic performance for glucose oxidation due to the unique hollow nanostructure and synergistic effects. The CuMn-PBA@NiCo-LDH NBs electrode displayed excellent electrocatalytic oxidation activity for glucose in an alkaline solution. Under optimal conditions, the electrode achieved a wide linear range (0.0005–1 mmol L–1, and 1–7 mmol L–1) and high sensitivity (10,300 μA L/mmol cm−2 and 5310 μA L/mmol cm−2), with a limit of detection (LOD) of 19 nmol L–1. The feasibility of the sensor applied to the detection of glucose was verified in real food samples through spiked recovery experiments. This electrode material offers an alternative method for the non-enzymatic glucose sensors.

Pre-concentration and partial fractionation of rare earth elements by ion exchange

This work evaluated the pre-concentration and fractionation of rare earth elements (REE) from an acid mine drainage (AMD), by using ion exchange technique. The AMD presents pH 3.50, total REE content of approximately 45.5 mg g−1, 1.3 g L−1 of sulfate and 253 mg L−1 of Ca, Al, Mg as the main impurities. The tests were carried out in columns using a commercial strongly acidic cation exchange resin, LEWATIT® MDS 200H. Regarding the loading step, the resin proved to be more selective for La, Ce, Pr and Nd. A total loading capacity of 0.25 mmol g−1 was obtained for the REE and 2.64 mmol g−1 for the impurities, with efficiencies of 78% and 48%, respectively. Regarding fractionation, the 0.01 mol L−1 NH4EDTA promotes the best elution profiles with more narrow and separated bands. Elution efficiency was greater for the heavy REE, near 100% and only 40% for the light ones. Aluminum and Ca were eluted with an efficiency of approx. 3%. Aluminum was the most difficult impurity to separate from REE.

A new thiosemicarbazone and its 3d metal complexes: Synthetic, structural, and antioxidant studies

2-[1-Oxo-1-(piperidin-1-yl)propan-2-ylidene]- N-(prop-2-en-1-yl)hydrazinecarbothioamide (HL) and its six coordination compounds [Cu(L)X] (X = Cl− (1), NO3− (2)), [Cu(A)(L)NO3](A = 1,10-Phen (3), 2,2′-Bpy (4)), [Ni(HL)2](NO3)2 (5), and [Fe(L)2]Cl (6) are synthesized and characterized by elemental analysis, Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and single-crystal X-ray crystallography. Uncoordinated thiosemicarbazone HL shows higher antioxidant activity against 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS+•) cation radicals compared with most of the other complexes. Complex 5 is the most active and its activity exceeds that of HL and is close to that of trolox, which is used in medicine as an antioxidant. The introduction of N-heteroaromatic bases (1,10-phenanthroline and 2,2′-bipyridine) into the inner sphere of the complex [Cu(L)NO3] did not lead to an increase in antioxidant activity.

Ascorbic acid-enhanced Fe(III)/peracetic acid process for the degradation of diclofenac: Treatment efficiency, mechanism and influencing factors

To overcome the sluggish reduction from Fe(III) to Fe(II) and excessive iron sludge production in Fe(III)/peracetic acid (PAA) process, ascorbic acid (AA), an environmental-friendly and natural reductant, was proposed in this study to boost the oxidation ability of Fe(III)/PAA process by facilitating the cycling of Fe(III)/Fe(II). AA-enhanced Fe(III)/PAA process exhibited remarkable acceleration in the degradation of diclofenac (DCF), with the removal rate of DCF being around 51 times higher than that without AA. Multiple reactive species of FeIVO2+, R-O, and OH were involved in the abatement of DCF in the AA/Fe(III)/PAA process. FeIVO2+ was confirmed as the predominant contributor for the elimination of DCF, whereas R-O and OH also participated in DCF abatement. In the AA-enhanced Fe(III)/PAA process, AA rapidly complexed with Fe(III) to produce the Fe(III)-AA complex, which was subsequently decayed to generate Fe(II), and then reactive species were generated by activating PAA with Fe(II) to degrade DCF through the pathways of dichlorination-cyclization, decarboxylation, and hydroxylation. The acute toxicity of the reaction solution employing BioFixlumi as a toxicity indicator decreased with the abatement of DCF. Common inorganic ions, including Cl−, SO42−, CO32−, and NO3−, had no adverse influence on DCF degradation, while humic acid and common cations (Zn2+, Ca2+, and Mg2+) inhibited DCF abatement. AA/Fe(III)/PAA process was highly effective for DCF removal in actual water samples, including surface water and underground water. AA/Fe(III)/PAA process was prone to degrading micropollutants with higher fractions of deprotonated species and lower ionization potentials, and performed with high selectivity towards micropollutants. Overall, the outstanding oxidation capacity and environmental friendliness of AA/Fe(III)/PAA process render it a potential technology to remove micropollutants in wastewater treatment.

Chemical characterization of Glaucosciadum cordifolium extracts obtained by different extraction techniques and their biopharmaceutical effects

Glaucosciadium cordifolium (Apiaceae) is traditionally used against stomach ailments, as aphrodisiac and appetizer. This study endeavored to characterize several extracts of G. cordifolium aerial parts (prepared by various isolation procedures (ASE: Accelerated solvent extraction; HAE: homogenizer-assisted extract; MAE: Microwave-assisted extraction; MAC: Maceration; SFE: supercritical CO2 extraction; SOX: Soxhlet; UAE: Ultrasound-assisted extraction) and evaluate the antioxidant activity and inhibitory activity against clinical enzymes. In order to describe the composition of the extracts liquid chromatography-mass spectrometry (LC-MS) analysis was employed. Of the total number of confirmed polyphenol components (15 in total), four were dominant in their content: 5-O-caffeoylquinic acid, p-coumaric acid, quercetin-3-O-glucoside and quercetin-3-O-rhamnoside. Spectrophotometric analysis showed that the total phenolic and flavonoid contents differed among the extracts, which was influenced by extraction technique used for their preparation. The phenolic content of the different extracts varied in the order HAE > UAE > MAC > SOX > MAE > ASE > SFE. HAE extract yielded the highest phenolic content (49.97 mg gallic acid equivalent (GAE)/g) while SFE demonstrated the lowest phenolic content (21.65 mg GAE/g). MAC extracts contained the highest flavonoids (50.35 mg rutin equivalent (RE)/g) while SFE extract showed the lowest flavonoid content (10.87 mg RE/g). UAE, MAC, MAE, HAE, SOX and ASE showed significant DPPH antioxidant activities and the values of radical inhibitory capacity varied in the range of 55.79–54.99 mg TE/g. SFE demonstrated weak DPPH (1,1-diphenyl-2-picrylhydrazyl) radical inhibitory activity with a value 7.0 mg TE/g. UAE showed the highest ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) cation radical inhibitory potential (122.41 mg trolox equivalent (TE)/g). The CUPRAC (cupric reducing antioxidant capacity) activity of UAE was remarkable with a value of 193.58 mg TE/g. A gradual decrease in activity was observed with extracts obtained from other extraction techniques with the lowest antioxidant activity (77.0 mg TE/g) obtained from SFE extract. The highest antioxidant recorded by Phosphomolybdenum was found in HAE extract (1.62 mmol TE/g). SFE showed the highest metal chelating activity (27.30 mg ethylenediamine tetraacetic acid (EDTAE)/g). Regarding the acetylcholinesterase (AChE) inhibitory activity, MAE and ASE extracts showed the highest potential with a value of 4.06 and 4.05 mg galanthamine equivalent (GALAE)/g respectively. All tested extracts showed considerable whitening activity and SFE revealed the highest activity against tyrosinase (93.82 mg kojic acid equivalent (KAE)/g). In addition, SFE showed the best inhibitory ability against amylase (0.71 mmol acarbose equivalent (ACAE)/g). However, the extracts had similar glucosidase inhibitory effects (1.64–1.71 mmol ACAE/g). The rich chemical composition of the extracts and joint action of different classes of polyphenolic compounds in them may be responsible for their high biological activity. Extracts with the highest activity could serve in the future as an important tool for controlling the activity of clinically important enzymes and take their place in the official formulation after additional pharmacological tests.

Crystal structure of bis-(3-carb-oxy-1-methyl-pyrid-inium) octa-bromide.

The crystal structure of the title salt, bis-(3-carb-oxy-1-methyl-pyridinium) octa-bromide, 2C7H8NO2 +·Br8 2-, consists of 3-carb-oxy-1-methyl-pyridinium (N-methyl-nicotinic acid) cations, which are stacked between relatively rare [Br8]2- anions. The polybromide [Br8]2- anion has point group symmetry and can be described as being composed of two [Br3]- anions connected with a Br2 mol-ecule in a Z-shaped manner. Contacts between neighboring octa-bromide anions ensure the creation of pseudo-polymeric chains propagating along [111]. The organic cations are located between anionic chains and are connected to each other through O-H⋯O hydrogen bonds and to the [Br8]2- anions through π⋯Br inter-actions that induce the creation of a supra-molecular tri-periodic network. In addition, the presence of weak C-H⋯Br contacts leads to the creation of layers, which align parallel to (11).

In Vitro Antioxidant and In Vivo Antigenotoxic Features of a Series of 61 Essential Oils and Quantitative Composition-Activity Relationships Modeled through Machine Learning Algorithms.

The antioxidant activity of essential oils (EOs) is an important and frequently studied property, yet it is not sufficiently understood in terms of the contribution of EOs mixtures' constituents and biological properties. In this study, a series of 61 commercial EOs were first evaluated as antioxidants in vitro, following as closely as possible the cellular pathways of reactive oxygen species (ROS) generation. Hence, EOs were assessed for the ability either to chelate metal ions, thus interfering with ROS generation within the respiratory chain, or to neutralize 2,2-diphenyl-1-picrylhydrazyl (DPPH•) and lipid peroxide radicals (LOO•), thereby halting lipid peroxidation, as well as to neutralize 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid cation radicals (ABTS•+) and hydroxyl radicals (OH•), thereby preventing the ROS species from damaging DNA nucleotides. Showing noteworthy potencies to neutralize all of the radicals at the ng/mL level, the active EOs were also characterized as protectors of DNA double strands from damage induced by peroxyl radicals (ROO•), emerging from 2,2'-azobis-2-methyl-propanimidamide (AAPH) as a source, and OH•, indicating some genome protectivity and antigenotoxicity effectiveness in vitro. The chemical compositions of the EOs associated with the obtained activities were then analyzed by means of machine learning (ML) classification algorithms to generate quantitative composition-activity relationships (QCARs) models (models published in the AI4EssOil database available online). The QCARs models enabled us to highlight the key features (EOSs' chemical compounds) for exerting the redox potencies and to define the partial dependencies of the features, viz. percentages in the mixture required to exert a given potency. The ML-based models explained either the positive or negative contribution of the most important chemical components: limonene, linalool, carvacrol, eucalyptol, α-pinene, thymol, caryophyllene, p-cymene, eugenol, and chrysanthone. Finally, the most potent EOs in vitro, Ylang-ylang (Cananga odorata (Lam.)) and Ceylon cinnamon peel (Cinnamomum verum J. Presl), were promptly administered in vivo to evaluate the rescue ability against redox damage caused by CCl4, thereby verifying their antioxidant and antigenotoxic properties either in the liver or in the kidney.

Double layer capacitance of a platinum electrode in a protic ionic liquid: The influence of cation acidity

Protic ionic liquids (PILs) are promising candidates as electrolytes for future intermediate-temperature polymer electrolyte membrane fuel cells (PEMFCs). A deeper understanding of their double layer properties is essential for the improvement of oxygen reduction reaction (ORR) kinetics in the interface of the platinum catalyst and PIL. In this study, we investigate the double layer differential capacitance of platinum in the presence of PILs with acidic cations of various proton donor strengths as a function of the electrode potential, bulk water content, and temperature. Complex capacitance plots of impedance spectra enable the evaluation of a high-frequency double layer capacitance, C1, and a mid-frequency pseudo-double layer capacitance, C2. The C1-capacitance curves were simulated by two mean field models that account for the presence of water, short range correlations of ions, and, in the case of the second model, also for the non-monotonic charging of the Pt surface that has a strong impact on the double-layer structure and properties. The simulations reveal different double-layer properties of [2-Sema][TfO], a PIL with a highly acidic cation, compared to the less acidic [1-EIm][TfO] and [Dema][TfO]. These variations are associated with differences in interionic forces, degrees of ion pairing, and the compactness of ionic layers. Most likely, these effects correlate with hygroscopicity and ability to form the hydrogen bonds of the cation, rather than with its acidity. The different pseudo-double layer capacitances of [2-Sema][TfO] and of the less acidic PILs at higher potentials are explained by different mechanisms of oxide formation.

Effect of the Media in the Folin-Ciocalteu Assay for the Analysis of the Total Phenolic Content of Olive Products

The nutritional and economic value of oils is affected by its antioxidant properties linked to their total phenolic content (TPC). The analysis of antioxidants such as phenols may be affected by the lipophilic character of the media. Therefore, the accurate determination of TPC in oils deserves particular attention. This research has tested the effect of the alkaline medium in the quantification of TPC in extra virgin olive oil (EVOO) and olive pomace oil (OPO) using the Folin-Ciocalteu method. Seven different EVOO and OPO oils were used to gain representativity and study matrix effects in the analysis. Among the alkaline conditions assayed, the Folin-Ciocalteu method led to maximum TPC in EVOOs samples using 7.5% Na2CO3, whereas 35% Na2CO3 showed better characterization of TPC in OPOs than milder basic conditions. Therefore, when analyzing olive oil products, adjusting the alkaline media in the Folin Ciocalteu assay is important for optimal TPC determination. TPC analyses via Folin-Ciocalteu with different media was supported with antioxidant activities determined with reference assays: 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid cation radical and 2,2-diphenyl-1-picrylhydrazyl radical.

Dual Salt Cation-Swing Process for Electrochemical CO2 Separation.

Electrochemical CO2 separations, which use electricity rather than thermal energy to reverse sorption of CO2 from concentrated point sources or air, are emerging as compelling alternatives to conventional approaches given their isothermal, ambient operating conditions, and ability to integrate with renewable energy inputs. Despite several electrochemical approaches proposed in previous studies, further explorations of new electrochemical CO2 separation methods are crucial to widen choices for different emissions sources. Herein, we report an electrochemical cation-swing process that is able to reversibly modulate the CO2 loading on liquid amine sorbents in dimethyl sulfoxide (DMSO) solvent. The process exploits a reversible carbamic acid-to-carbamate conversion reaction that is induced by changing the identity of Lewis acid cations (e.g. K+, Li+, Ca2+, Mg2+, and Zn2+) coordinated to the amine-CO2 adduct in the electrolyte. Using ethoxyethylamine (EEA) as a model amine, we present NMR-based speciation studies of carbamic acid-to-carbamate conversion as a function of amine/salt concentrations and cation identity. The reaction is further probed using gas-flow reaction microcalorimetry, revealing the energetic driving forces between cations and the amine-CO2 adduct that play a key role in the described re-speciation. A prototype electrochemical cell was further constructed comprising a Prussian white (PW) potassium (K+) intercalation cathode, zinc (Zn) foil anode, and EEA/DMSO electrolyte containing a dual KTFSI/Zn(TFSI)2 salt. A low CO2 separation energy of ∼22-39 kJ/mol CO2 (0.1-0.5 mA cm-2) was achieved with a practical CO2 loading delta of ∼0.15 mol CO2/mol amine. Further optimizations in electrolyte design and cell architectures toward continuous CO2 capture-release are expected to enhance rate performance while retaining favorable separation energies.

Mechanism of Water Dissociation on Metal Oxide Surfaces in Bipolar Membrane Electrolyzers: A First-Principles Calculation

Bipolar membranes for water electrolysis, consisting of an acidic cation exchange layer and an alkaline anion exchange layer are a promising means for hydrogen production. The electrolyzer operates the oxygen evolution reaction (OER) under locally basic conditions and the hydrogen evolution reaction (HER) under locally acidic conditions. Water dissociation (WD) occurs within the junction, which is spatially separated from the HER and the OER. It has been shown that the addition of a layer of metal oxide nanoparticles at the junction significantly lowers the overpotential for the process of WD [Science, 2020, 369,1099]. However, the atomistic mechanism by which the metal oxide surface catalyzes the WD is still unclear. We will discuss the theoretical understanding of the WD mechanism at the metal-oxide/water interfaces and investigate the descriptors such as surface pKa, dielectric constants, and adsorption energies, etc. We will combine ab intio molecular dynamics simulations with the electronic structure calculations at the hybrid functional level. Further details of the reaction mechanisms during the WD process will also be explored with the nudged-elastic-band calculations.

In-vitro anti-diabetic, anti-Alzheimer, anti-tyrosinase, antioxidant activities of selected coumarin and dihydroisocoumarin derivatives

Benzo-α-pyrone structured coumarin derivatives are secondary metabolites first obtained from Coumarouna odorata in 1822. Coumarin and its structural isomer dihydroisocoumarin derivatives are found in many different sources in nature. Several different bioactivities of these compounds have been reported. In this study, preliminary activity screening and comparison of four purchased coumarin derivatives (esculetin, esculin monohydrate, umbelliferon, scoparone) and four previously isolated 3-phenyl-3,4-dihydroisocoumarin derivatives (thunberginol C, scorzocreticoside I, scorzocreticoside II, scorzopygmaecoside) from a medicinal plant were carried out by in-vitro methods. α-Glucosidase, acetylcholinesterase, butyrylcholinesterase, tyrosinase inhibitor activities and antioxidant potentials of the compounds were evaluated. Consequently, thunberginol C (free – not glycosylated form of 3,4-dihydroisocoumarin structure) showed better potential in all enzyme inhibitory activities compared to coumarin structure. Particularly, α-glucosidase inhibitory activity of this compound with a very low IC50 value (94.76±2.98 µM) compared to standard acarbose (1036.2±2.70 µM) should be noted. Glycosylation and/or methoxy substitution of 3,4-dihydroisocoumarin structure resulted a significant decrease in all tested enzyme inhibitory activities. The structures of esculin MH, umbelliferone, scoparone, scorzocreticoside I, and scorzopygmaeceoside might be considered in further synthetic studies as selective acetylcholinesterase inhibitors. Thunberginol C has a promising potential in tyrosinase inhibitory activity. Esculetin and thunberginol C showed the best results with high potentials in antioxidant activity via 2,2-diphenyl-1-picryl-hydrazyl-hydrate free radical scavenging, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid cation radical decolorization, and cupric ion reducing antioxidant capacity assays compared to the standards.

Influence of Lanthanum on Stern Layer Conductance in the Nanochannel.

In this report, high-frequency electric impedance spectroscopy was performed to investigate ionic transport through nanochannels. Special attention was focused on (i) conductance behaviors depending on the role of cation valence in three background electrolytes (XCln): monovalent 1-1 (K+ and Cl-), divalent 2-1 (Mg2+ and 2Cl-), and trivalent 3-1 (La3+ and 3Cl-), (ii) the effects of proton and bicarbonate ions on bulk and surface conductance, and (iii) the connected microchannel dimension (surface/height ratio aspect) within the nanochannel apparent conductance. The results highlight a net quantitative increase in surface silanol density and a strong decrease in surface ionization degree when lanthanum cations are employed. The results also demonstrate that La3+ strongly interacts with the silica surface, leading to negative values of standard free energy for ion-site interactions and chemical potential for ion-ion correlations in the Stern layer of -0.8 and -10.2 kT, respectively. We ascribed the evolution of surface charge density to the balance between the mole ratios of water molecules and adsorbed cations at equilibrium. We found that La3+ behaves as an acidic cation (Lewis conceptualization) that neutralizes the negative silica surface accompanying water molecule expulsion due to steric hindrance. This study constitutes a new contribution to ion-site interactions and to ion-ion correlation phenomena on the planar silica surface to explain charge inversion observation in micro-nanofluidic devices.

Differences in the Shiga Toxin (Stx) 2a Phage Regulatory Switch Region Influence Stx2 Localization and Virulence of Stx-Producing Escherichia coli in Mice.

Shiga toxin (Stx)-producing Escherichia coli (STEC) is a major cause of foodborne illness globally, and infection with serotype O157:H7 is associated with increased risk of hospitalization and death in the U.S. The Stxs are encoded on a temperate bacteriophage (stx-phage), and phage induction leads to Stx expression; subtype Stx2a in particular is associated with more severe disease. Our earlier studies showed significant levels of RecA-independent Stx2 production by STEC O157:H7 strain JH2010 (stx2astx2c), even though activated RecA is the canonical trigger for stx-phage induction. This study aimed to further compare and contrast RecA-independent toxin production in Stx2-producing clinical isolates. Deletion of recA in JH2010 resulted in higher in vitro supernatant cytotoxicity compared to that from JH2016ΔrecA, and the addition of the chelator ethylenediaminetetraacetic acid (EDTA) and various metal cations to the growth medium exacerbated the difference in cytotoxicity exhibited by the two deletion strains. Both the wild-type and ΔrecA deletion strains exhibited differential cytotoxicity in the feces of infected, streptomycin (Str)-treated mice. Comparison of the stx2a-phage predicted protein sequences from JH2010 and JH2016 revealed low amino acid identity of key phage regulatory proteins that are involved in RecA-mediated stx-phage induction. Additionally, other STEC isolates containing JH2010-like and JH2016-like stx2a-phage sequences led to similar Stx2 localization, as demonstrated by JH2010ΔrecA and JH2016ΔrecA, respectively. Deletion of the stx2a-phage regulatory region in the wild-type strains prevented the differential localization of Stx2 into the culture supernatant, a finding that suggests that the stx2a-phage regulatory region is involved in the differential ΔrecA phenotypes exhibited by the two strains. We hypothesize that the amino acid differences between the JH2010 and JH2016 phage repressor proteins (CIs) lead to structural differences that are responsible for differential interaction with RecA. Overall, we discovered that non-homologous stx2a-phage regulatory proteins differentially influence RecA-independent, and possibly RecA-dependent, Stx2 production. These findings emphasize the importance of studying non-homologous regulatory elements among stx2-phages and their influence on Stx2 production and virulence of STEC isolates.

Key to Life, Risks and Cycle of Nitrogen

Nitrogen is practically inert and largely unreactive, existing mostly in molecular form (N2) in the atmosphere and unsuitable for uptake by living matter. But it is one of the most commonly used practices to increase crop yields throughout the world because of the abundant availability of N fertilizers and their great effectiveness to increase yields compared with other organic fertilizers, such as manure and compost. It is essential to achieve production levels, which enable global food security, without compromising environmental security. Excessive application of N fertilizers in the last several decades, however, has resulted in undesirable consequences of soil and environmental degradations, such as soil acidification, N leaching to the groundwater, and greenhouse gas (N2O) emissions. Crop yields have declined in places where soil acidification is high due to the unavailability of major nutrients and basic cations and the toxic effect of acidic cations. Other disadvantages of excessive N fertilization include increased cost of fertilization, reduced N-use efficiency, and negative impact on human and livestock health. Diffuse pollution, caused by N fertilization in agriculture, has become a global problem that is difficult to solve. Nearly half of N fertilizer input is not used by crops and is lost into the environment via the emission of gases or by polluting water bodies. The N pollution level expected by 2050 is projected to be 150% higher than in 2010, with the agricultural sector accounting for 60% of this increase. So, to reduce these problems globally, understanding of nitrogen cycle and nutrient use efficiency is important.

Sorption of Lead, Zinc and Copper from Simulated Wastewater by Amberlite Ir-120 Resin

The presence of heavy metals in the environment is major concern due to their toxicity. In the present study a strong acid cation exchange resin, Amberlite IR 120 was used for the removal of lead, zinc and copper from simulated wastewater. The optimum conditions were determined in a batch system of concentration 100 mg/L, pH range between 1 and 8, contact time between 5 and 120 minutes, and amount of adsorbent was from 0.05 to 0.45 g/100 ml. A constant stirring speed, 180 rpm, was chosen during all of the experiments. The optimum conditions were found to be pH of 4 for copper and lead and pH 6 for zinc, contact time of 60 min and 0.35 g of adsorbent. Three different temperatures (25, 40 and 60°C) were selected to investigate the effect of adsorption temperature on heavy metals adsorption onto Amberlite IR. The equilibrium data were analyzed by the Langmuir and Freundlich isotherms. The thermodynamic parameters such as Gibbs free energy, enthalpy and entropy changes were calculated. Moreover, in order to understand the heavy metal extraction kinetics in the presence of Amberlite IR 120, the ion exchange kinetics was also studied. The ion exchange kinetics data were regressed by the pseudo first-order, second-order models. The results obtained show that the Amberlite IR 120 strong acid cation exchange resin performed well for the removal of lead, zinc and copper.

Direct tracking of ultrafast proton transfer in water dimers.

Upon ionization, water forms a highly acidic radical cation H2O+· that undergoes ultrafast proton transfer (PT)-a pivotal step in water radiation chemistry, initiating the production of reactive H3O+, OH[Formula: see text] radicals, and a (hydrated) electron. Until recently, the time scales, mechanisms, and state-dependent reactivity of ultrafast PT could not be directly traced. Here, we investigate PT in water dimers using time-resolved ion coincidence spectroscopy applying a free-electron laser. An extreme ultraviolet (XUV) pump photon initiates PT, and only dimers that have undergone PT at the instance of the ionizing XUV probe photon result in distinct H3O+ + OH+ pairs. By tracking the delay-dependent yield and kinetic energy release of these ion pairs, we measure a PT time of (55 ± 20) femtoseconds and image the geometrical rearrangement of the dimer cations during and after PT. Our direct measurement shows good agreement with nonadiabatic dynamics simulations for the initial PT and allows us to benchmark nonadiabatic theory.

Construction of arsenic selective chelating resin with iron precursor for removal of low-concentration arsenic: Breakthrough modeling and field deployment

The presence of exorbitant arsenic contamination in the aquatic environment causes astronomically immense health quandaries affecting millions of people, which may lead to death in the case of prolonged indigestion of arsenic-containing drinking water. Herein, we are reporting porous chelating resin with an iron precursor for the removal of arsenic ions from water. Weak acid cation resin was functionalized under varying experimental conditions to get a suitable resin with high arsenic uptake. The theoretical results revealed that the maximum Langmuir adsorption capacities of 3.27 mg g−1 and 1.13 mg g−1 were achieved for As(V) and As(III), respectively. The kinetics of adsorption followed the pseudo-second-order (PSO) model with a high determination coefficient (R2) of 0.9963 and 0.9895 for As(V) and As(III), respectively. The Adams-Bohart, Thomas, Yoon-Nelson, and Pore diffusion models were used to identify the breakthrough curve in the fixed bed adsorption column. The column performance improved with a larger bed height (55 cm), low concentration of influent (0.25 mg L−1), and low flow rate of influent (80 mL min−1). Under this condition, the breakthrough time and exhaustion time were 314 min and 408 min for As(V) and 124 min and 185 min for As(III), respectively.