Presence Of Different Metal Cations Research Articles

New G-Triplex DNA Dramatically Activates the Fluorescence of Thioflavin T and Acts as a Turn-On Fluorescent Sensor for Uracil-DNA Glycosylase Activity Detection.

G-triplexes are G-rich oligonucleotides composed of three G-tracts and have absorbed much attention due to their potential biological functions and attractive performance in biosensing. Through the optimization of loop compositions, DNA lengths, and 5'-flanking bases of G-rich sequences, a new stable G-triplex sequence with 14 bases (G3-F15) was discovered to dramatically activate the fluorescence of Thioflavin T (ThT), a water-soluble fluorogenic dye. The fluorescence enhancement of ThT after binding with G3-F15 reached 3200 times, which was the strongest one by far among all of the G-rich sequences. The conformations of G3-F15 and G3-F15/ThT were studied by circular dichroism. The thermal stability measurements indicated that G3-F15 was a highly stable G-triplex structure. The conformations of G3-F15 and G3-F15/ThT in the presence of different metal cations were studied thoroughly by fluorescent spectroscopy, circular dichroism, and nuclear magnetic resonance. Furthermore, using the G3-F15/ThT complex as a fluorescent probe, a robust and simple turn-on fluorescent sensor for uracil-DNA glycosylase activity was developed. This study proposes a new systematic strategy to explore new functional G-rich sequences and their ligands, which will promote their applications in diagnosis, therapy, and biosensing.

Solid-Electrolyte Interphase Formation in Amide-Type Ionic Liquids in the Presence of Different Metal Cations

The formation of solid-electrolyte interphase (SEI) on a glassy carbon (GC) electrode in 1-butyl-1-methylpyrrolidinium bis(fluorosulfonyl)amide (BMPFSA) and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA) containing Li+, Na+, K+, and Ni2+ was investigated using the redox reaction of ferrocene (Fc). The anodic peak potential (E pa) for the oxidation of Fc changed after holding the electrode at –1.4 to –1.5 V vs Ag|Ag(I) in BMPFSA in the presence of the alkali metal ions. The decomposition of FSA– was confirmed by X-ray photoelectron spectroscopy (XPS) on a GC electrode held at –1.5 V vs Ag|Ag(I) for 6 h in BMPFSA containing the alkali metal ions. The change in E pa may also suggest the formation of homogeneous SEI in the FSA–-type ionic liquid. Moreover, E pa changed after holding the electrode at the potential more negative than –0.9 V vs Ag|Ag(I) in 50 mM Ni(TFSA)2/BMPTFSA while the decomposition of TFSA– was not confirmed by XPS on the electrode held at –1.1 V vs Ag|Ag(I) for 6 h, suggesting the bonds except C-F (e.g., S-C) were dissociated to form the SEI. Since the deposition potential of Ni in BMPTFSA was more negative than the SEI formation potential, the deposition of Ni may be inhibited by the SEI.

Thermally Induced Transitions of d(G4T4G3) Quadruplexes Can Be Described as Kinetically Driven Processes.

DNA sequences that are rich in guanines and can form four-stranded structures are called G-quadruplexes. Due to the growing evidence that they may play an important role in several key biological processes, the G-quadruplexes have captured the interest of several researchers. G-quadruplexes may form in the presence of different metal cations as polymorphic structures formed in kinetically governed processes. Here we investigate a complex polymorphism of d(G4T4G3) quadruplexes at different K+ concentrations. We show that population size of different d(G4T4G3) quadruplex conformations can be manipulated by cooling rate and/or K+ concentration. We use a kinetic model to describe data obtained from DSC, CD and UV spectroscopy and PAGE experiments. Our model is able to describe the observed thermally induced conformational transitions of d(G4T4G3) quadruplexes at different K+ concentrations.

Metal Cation-Binding Mechanisms of Q-Proline Peptoid Macrocycles in Solution.

The rational design of foldable and functionalizable peptidomimetic scaffolds requires the concerted application of both computational and experimental methods. Recently, a new class of designed peptoid macrocycle incorporating spiroligomer proline mimics (Q-prolines) has been found to preorganize when bound by monovalent metal cations. To determine the solution-state structure of these cation-bound macrocycles, we employ a Bayesian inference method (BICePs) to reconcile enhanced-sampling molecular simulations with sparse ROESY correlations from experimental NMR studies to predict and design conformational and binding properties of macrocycles as functional scaffolds for peptidomimetics. Conformations predicted to be most populated in solution were then simulated in the presence of explicit cations to yield trajectories with observed binding events, revealing a highly preorganized all-trans amide conformation, whose formation is likely limited by the slow rate of cis/trans isomerization. Interestingly, this conformation differs from a racemic crystal structure solved in the absence of cation. Free energies of cation binding computed from distance-dependent potentials of mean force suggest Na+ has a higher affinity to the macrocycle than K+, with both cations binding much more strongly in acetonitrile than water. The simulated affinities are able to correctly rank the extent to which different macrocycle sequences exhibit preorganization in the presence of different metal cations and solvents, suggesting our approach is suitable for solution-state computational design.

Synthesized akhtenskites remove ammonium and manganese from aqueous solution: removal mechanism and the effect of structural cations.

Ammonium and manganese removal by tunnel-structured manganese oxide is still enigmatic. Herein, tunnel-structured akhtenskites with different structural cations (Na–MnOx, Mg–MnOx Ca–MnOx, Fe–MnOx) were synthesized by the KMnO4 and Mn2+ reaction in the presence of different metal cations, and were used to remove ammonium and manganese from aqueous solution. The results of the batch adsorption experiments indicated that akhtenskites effectively removed NH4+ and Mn2+, and the removal process fitted the pseudo-second-order model. By measuring the concentration of nitrate and nitrite, discriminating the adsorbed and oxidized Mn2+, and testing the zeta potential of the oxides, it can be concluded that NH4+ was merely removed by electrostatic adsorption via Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> Mn–O−; Mn2+ could also be adsorbed by ion exchange with Mn–OH, and the adsorbed Mn2+ could be partly oxidized. The structural properties of the akhtenskites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) specific area, and X-ray photoelectron spectroscopy (XPS). The experimental results showed that ions with higher valence can result in a higher percentage of Mn(iii) in akhtenskite. Mg2+ can result in a lower proportion of lattice oxygen in the oxide, and Fe3+ can increase the pH of the point of zero charge. Both of them were unfavored for the oxidation of Mn2+. Moreover, it was found that Ca–MnOx had optimal removal performance in the catalytic oxidation of Mn2+ owing to appropriate percentages of Olatt and Mn(iii) and lower zeta potential. This study provides new insights into the synthesis and application of manganese oxides.

Organically Functionalized Mesoporous SBA-15 Type Material Bearing Fluorescent Sites for Selective Detection of HgII from Aqueous Medium.

Hg(II) contamination in water resources is one of the major health issues in keeping the purity standard of the municipal water supply. Herein, we report a new mesoporous sensor probe material SBA-ABZ-PEA having a 2D-hexagonally ordered mesoporous framework bearing covalently bonded fluorescent sites, and this has been synthesized through a two-step post-synthesis grafting route. A pure silica mesoporous SBA-15 material has been functionalized with (3-chloropropyl)triethoxysilane (ClPTES) to obtain chloro-functionalized SBA-15, which was further reacted with 4-aminobenzaldehyde followed by treatment with 2-(2-pyridyl)-ethylamine resulting in functionalized 2D-hexagonal mesoporous sensor probe SBA-ABZ-PEA. Small angle PXRD, N2 adsorption/desorption, HRTEM, TGA, and FT-IR studies have been carried out to characterize these materials. Our experimental results suggested successful grafting of the organic moiety on the SBA-15 surface along with preservation of mesoporosity throughout the grafting process. Photoluminescence measurements were carried out in the aqueous suspension of SBA-ABZ-PEA in the presence of different metal cations, like NaI, MgII, AlIII, KI, CaII, MnII, CoII, CuII, ZnII, CdII, PbII, and HgII. This result revealed that, among the various metal-ions, the emission intensity of the mesoporous sensing probe material SBA-ABZ-PEA has been dramatically quenched in the presence of the HgII ion. To check the sensitivity of the sensor probe, the fluorescence emission was also studied in the presence of different concentrations of HgII ions. A perfect linear plot between the concentrations of HgII ions in the aqueous medium with their corresponding fluorescence intensities with a detection limit of 1.2 × 10–6 M has been observed.

Ammonia-Assisted Growth of CoSn(OH)6 Nanostructures and Their Electrochemical Performances for Supercapacitor.

In this work, ammonia-assisted one step growth of SnO₂ and mixed metal hydroxide CoSn(OH)6 on Ni foam is illustrated. The nanostructured films grown on Ni foam are highly porous in nature. The CoSn(OH)6 nanostructures were deposited using three different molar ratios of Sn/Co precursors i.e., 1:1, 1:2 and 2:1 and their performances as supercapacitor have been investigated and compared with pristine SnO₂. Interestingly, the CoSn(OH)6 thin films prepared with 1:2 molar ratio of Sn/Co showed remarkably high areal capacitance and good cyclic stability. It is believed that the presence of different metal cations and their valence states along with the porous nanostructure makes the material outstanding as supercapacitor. The highest areal capacitance of 4189 mF cm-2 was obtained at a current density of 2 mA cm-2 for CoSn(OH)6 thin films offering an excellent cyclic stability with a capacity retention of 90.3% after 2000 cycles.

Influence of amphotericin B on liquid crystal state of the Cholesterol/Dipalmitoylphosphatidylcholine monolayer in the presence of different metal cations**Project supported by the National Natural Science Foundation of China (Grant Nos. 21402114 and 11544009), the Natural Science Basic Research Plan in Shaanxi Province of China (Grant No. 2016JM2010), and the Fundamental Research Funds for the Central Universities of China (Grant No.

Amphotericin B is a very effective antifungal drug, but it has an adverse reaction to the membrane of mammals’ cells. The interaction between AmB and cholesterol (Chol) causes the formation of pores on the membrane to destroy its integrity. In particular, AmB has a significant effect on the permeability of membrane for K+ ions. It has been reported that Na+ ions and Ca2+ ions may have some influence on the interaction between amphotericin B and lipid molecules. In this work, the effects of these metal cations on the physical state and intermolecular interaction of the Cholesterol/ Dipalmitoylphosphatidylcholine (Chol/DPPC) monolayer with and without AmB have been investigated. The addition of AmB induces the change of physical state of the lipid monolayer from liquid-gel phase to liquid phase. Different metal cations could influence the phase transition of the AmB-lipid monolayer. The K+ ions and Ca2+ ions make the obvious phase transition disappear. However, the presence of Na+ ions has little influence on the phase transition of the AmB-lipid monolayer. The addition of AmB and the presence of different metal cations weaken the attractive force on the monolayers. After addition of AmB, the force between the molecules is the strongest in the environment of K+ ions, thus is the weakest in the environment of Ca2+ ions, which may be due to the distribution of these metal cations inside and outside of cells. A large number of K+ ions distribute inside of the cells, thus most of Na+ and Ca2+ ions exist out of the cells. Hence, it may be possible that when AmB molecules are out of the cells, the reaction between the drug and lipid molecules is weaker than that inside the cells. These results may have a great reference value for further studying the toxicity mechanism of AmB and the influence of metal cations on the membrane.

Layered manganese oxides for formaldehyde-oxidation at room temperature: the effect of interlayer cations

A series of K-, Mg-, Ca-, and Fe-containing birnessites were prepared by a facile comproportionation reaction of Mn2+ and MnO4− in the presence of different metal cations.

Inhibition Efficiency of Alkaline Metal Salts on Carbon Steel Corrosion in Acidic Media

Corrosion inhibitors are widely used in acid solutions during pickling and descaling. In this study, the inhibition performance of different alkaline metal salts in the concentration range 0-0.1 M has been found out. The corrosion behavior of low carbon steel in 1 M HCl in the presence of different metal cations and different anions is studied using weight loss and OCP (Open Circuit Potential) methods at 20 åC. It is found that the addition of these salts inhibits the corrosion markedly. The inhibition effect is in the following order Na2SO4 >NaI > LiCl > NaCl > KCl > NaNO3 > NaBr.

A New Fluorescent Chemosensor for Metal Ions Based upon 1,8‐Naphthalimide and 8‐Hydroxyquinoline

AbstractA new fluorescent chemosensor based upon 1,8‐naphthalimide and 8‐hydroxyquinoline was synthesized, and its fluorescent properties in the presence of different metal cations (Hg2+, Ag+, Zn2+, Fe2+, Cd2+, Pb2+, Ca2+, Cu2+, Mg2+, and Ba2+) were investigated. It displayed fluorescence quenching with some heavy and transition metal (HTM) ions, and the quenching strongly depended on the nature of HTM ions.

Synthesis and properties of photosensitive poly(urethane-acrylate) containing anil groups with application in the chemosensors area

Some aspects of the enol-imine to keto-enamine photoisomerism and fluorescent behavior of the new monomer with urethane and anil units in its structure, namely, methacryloyloxyethyl-2-carbamoyloxy(m-methyl, o-hydroxybenziliden)aniline (UAN), were studied comparatively with the corresponding copolymer poly (methacryloyloxyethyl-2-carbamoyloxy(m-methyl, o-hydroxybenziliden)aniline)-co-methyl methacrylate) (COP-UAN). The structure, thermal properties, and morphology of the anil compounds were investigated by Fourier transform infrared, proton nuclear magnetic resonance, fluorescence spectroscopies, UV spectrophotometry, thermogravimetric analysis, differential scanning calorimetry, and atomic force microscopy. The photochromic behavior of salicylideneanil units was investigated by UV/laser irradiation, and an inspection of their photophysical properties suggested that such structures could function as fluorescent chemosensors for some transition metals, a fluorescence quenching in the presence of different metal cations (Fe3+, Fe2+, Cu2+, and Ni2+) being evidenced. The direct observation of an enhancement in the fluorescence emission caused of the presence of Zn2+ (solution) or Fe2+, Cu2+, and Zn2+ (thin film) would be rather suitable for the production of turn-on fluorescent chemosensors. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

High affinity cation-binding sites in Complex I from Escherichia coli

Studies on the activity of Complex I from Escherichia coli in the presence of different metal cations revealed at least two high affinity metal-binding sites. Membrane-bound or isolated Complex I was activated by K + (apparent binding constant ∼ 125 μM) and inhibited by La 3+ ( IC 50 = 1 μM). K + and La 3+ do not occupy the same site. Possible localization of these metal-binding sites and their implication in catalysis are discussed.

Electrocatalytic determination of hydroxylamine with alizarin red S as a homogenous mediator on the glassy carbon electrode

Abstract The anodic oxidation of hydroxylamine has been studied on a glassy carbon electrode by electrocatalytic effect of Alizarine red S (ARS) as a homogenous mediator in 0.1 M the phosphate buffer (pH 6), using the diagnostic techniques of cyclic voltammetry, linear sweep voltammetry and chronoamperometry. Anodic oxidation of hydroxylamine by cyclic voltammetry showed that the catalytic current of the system depends on the hydroxylamine concentration. The magnitude of the peak current for ARS increased sharply in the presence of hydroxylamine and was proportional to its concentration. Hydroxylamine was detected over a linear concentration range of 10–800 μM with low detection limits, which was 7.2 μM with linear sweep voltammetric method. The diffusion coefficient of hydroxylamine was also estimated using chronoamperometry (D = 2.16 × 10−6 cm2 s−1). The chronoamperometric studies were also used to determine the catalytic rate constant for catalytic reaction of ARS with hydroxylamine (k = 1.86 × 103 M−1 s−1). The experimental results showed that the peak current varied in the presence of different metal cations but these effects were omitted in the presence of EDTA, while almost all of the anions had no effect on the peak current of hydroxylamine. This new voltammetric method of hydroxylamine determination is very rapid, reproducible, selective and sensitive, and can be used for the real sample analysis. The importance of the technique is because of its ability to electrocatalytically determine the hydroxylamine with ARS as homogenous electrocatalyst, while it does not need to be prepared as for the modified electrodes. The independency of the system from the interferences and its ability of easily removing the effect of most cationic interferences are the important features of the technique.

Studying the photophysical properties of a polymerizable 1,8‐naphthalimide dye and its copolymer with styrene as potential fluorescent sensors for metal cations

AbstractThe photophysical characteristics of a polymerizable 1,8‐naphthalimide dye and its copolymer with styrene have been investigated. The functional properties of both low and high molecular weight fluorophores in the presence of different metal cations have been discussed with regard to their potential application as fluorosensors for the metal cations and protons. In acetonitrile solution the monomeric 1,8‐naphthalimide enhances its fluorescence emission in the presence of metal cations (Zn2+, Fe3+, Co2+, Pb2+, Cu2+, Ni2+, and Mn2+). In aqueous media the poly(St‐co‐MD) exhibits a selective response to Fe3+ cations. The monomeric and polymeric fluorophores also exhibit a considerable increase in their fluorescence intensity at acidic pH values (pH < 6) which suggest that they could be used as ON–OFF probes in analytical devices for signaling the presence of protons. Copyright © 2008 John Wiley & Sons, Ltd.

A new fluorosensor based on bis-1,8-naphthalimide for metal cations and protons

The paper reports on the synthesis and spectral characteristics of a new fluorescent bis-1,8-disubstituted naphthalimide linked by a di-ethylenetriamine bridge (NI2TEA). The ability of the new compound to detect cations has been evaluated by monitoring spectrophotometrically the changes in the fluoresence intensity performed on its N, N-dimethylformamide (DMF) solution. The behaviour of the new compound has been tested in the presence of different metal cations: Fe 3+, Cr 3+, Mn 2+, Sr 2+, Ni 2+, Zn 2+, Cu 2+ and Co 2+. The results show clearly that only Fe 3+ and Cr 3+ cations are effectively detected. Besides, in N, N-di-methylformamide solution the NI2TEA can be used as a naked eye sensor for hydroxyl anions.

Electrocatalytic oxidation of hydrazine with pyrogallol red as a mediator on glassy carbon electrode

The anodic oxidation of hydrazine has been studied on a glassy carbon electrode by electrocatalytic effect of pyrogallol red as a homogenous mediator, using cyclic voltammetry, linear sweep voltammetry and chronoamperometry as diagnostic techniques. Using cyclic voltammetry study showed that, the catalytic current of the system depends on the concentration of hydrazine. The magnitude of the peak current for pyrogallol red increased sharply in the presence of hydrazine, and proportional to hydrazine concentration. The diffusion coefficient of hydrazine was also estimated using chronoamperometry. The chronoamperometry studies also were used to determine the catalytic rate constant for catalytic reaction of pyrogallol red with hydrazine. The experimental results showed that the peak current varied in the presence of different metal cations, but these effects were omitted in the presence of EDTA, while almost all of anions had no effect on the peak current of hydrazine. The proposed method was used for analysis of hydrazine in real samples.

Cation Recognition by Self-Assembled Layers of Novel Crown-Annelated Tetrathiafulvalenes

Thin-film electrochemical sensors are reported that are based on cation-sensitive redox-active molecules such as in the Figure (new TTF-crown derivatives with R = C(O)O(CH2)nSH or CH2SH) immobilized on a metal surface. The synthesis of the molecules and the self-assembly of the monolayers are outlined. The electrochemical recognition properties in solution and as monolayers in the presence of different metal cations are described.

Cation Recognition by Self-Assembled Layers of Novel Crown-Annelated Tetrathiafulvalenes

Thin-film electrochemical sensors are reported that are based on cation-sensitive redox-active molecules such as in the Figure (new TTF-crown derivatives with R = C(O)O(CH2)nSH or CH2SH) immobilized on a metal surface. The synthesis of the molecules and the self-assembly of the monolayers are outlined. The electrochemical recognition properties in solution and as monolayers in the presence of different metal cations are described.

Activation of pepsin (EC 3.4.4.1) by heavy-metal ions including a contribution to the mode of action of copper sulphate in pig nutrition.

1. Kinetic experimetns were done with pepsin (EC 3.4.4.1) using haemoglobin as a substrate in the presence of different metal cations. 2. The activation of peptic hydrolysis with higher concentration of cupric ions added to the reaction mixture was determined from turnover-rate curves in experiments with constant substrate concentration. With a Cu2+ concentration greater than 1.67 X 10(-4) M activation was obtained. 3. Nickel ions at a concentration of 8-33 X 10(-4) M and at higher concentrations also increased pepsin activity. Additions of ferrous ions and zinc ions had no effect. 4. Experiments were done using variable substrate concentrations in the presence of different Cu2+ concentrations. The concentrations of haemoglobin ([S]) at half maximum velocity were determined. The double-reciprocal plots of [S] v. reaction velocity (v) (i.e. 1/[S] v. 1/v) had no common intersection point. Therefore the kinetics did not correspond to any of the known kinetics. The activation brought about by Cu2+ cannot easily be explained by the study of the kinetics. Certain simple explanations of the phenomenon can be eliminated.