Method of measuring oligonucleotide-metal affinities: interactions of the thrombin binding aptamer with K+ and Sr2+

We report a new, mass spectrometry-based method for measuring affinity constants for specific metal ion binding to DNA, particularly for quadruplex DNA. This method, which is applicable to other systems, utilizes the gas-phase signal fractions, as determined by mass spectrometry, from the bound and unbound species as input into a mathematical model that determines various parameters, one of which is the binding affinity constant. The system used to develop and test the model was the thrombin-binding aptamer, an appropriate quadruplex structure that binds both K+ and Sr2+ cations. Using this method, we measured the binding constants of potassium and strontium cations with the quadruplex structure to be 5000 and 240 nM, respectively. We then applied the method to measure the change in enthalpy of the binding of strontium cations to the thrombin binding aptamer. The DeltaH for this interaction is -71 kJ/mol (-17 kcal/mol). The binding constant measurements are consistent with earlier measurements on the same system, and the measured change in enthalpy is in excellent agreement with previous work.     

Sorption properties of silicate materials based on Ca2SiO4 in humic acid solutions

The effect of humic acids (HA) in river water on the sorption properties of metallurgical slag (major component Ca₂SiO₄) was revealed in batch sorption experiments. Interaction of HA with sorbate cations in solution and with the sorbent surface affects the character of the sorption process found previously for dicalcium silicate. This interaction results in a decrease in the affinity of dicalcium silicate to multiple-charged cations [REE(III), U(VI), Th(IV)] in their sorption from river water by more than an order of magnitude. Possible chemical transformations responsible for a decrease in the sorption affinity of the silicate sorbent are discussed: complexation of HA with metal cations in the aqueous phase and competing reactions of the sorption of HA and calcium humate complexes on the surface of sorbent particles.     

Effect of competitive ions on the arsenic removal by mesoporous hydrous zirconium oxide from drinking water

Adsorption properties of 302-type commercially available hydrous zirconium oxide (302-HZO) towards arsenic and some competitive anions and cations have been studied under batch and column conditions. Due to amphoteric properties, anion exchange performance of hydrous zirconium oxide is pH dependent. Media exhibits high affinity towards arsenic in a broad pH range, with high adsorption capacity at pH < 8. It was shown that silicate and phosphate ions are arsenic's main competitors affecting media adsorption capacity. Presence of transition metal cations in <1 ppm does not affect 302-HZO capacity on arsenic, whereas alkaline-earth cations improve arsenic removal. The possibility for significant increase of 302-HZO adsorption capacity on arsenic at pH > 8 by using “solid acidifier” technique is discussed. Results of 302-HZO field trials are presented.     

Morphological Control Over Gel Structures of Mixed Semiconductor-Metal Nanoparticle Gel Networks with Multivalent Cations

In this work, the influence of two different types of cations on the gel formation and structure of mixed gel networks comprised of semiconductor (namely CdSe/CdS nanorods NR) and Au nanoparticles (NP) as well as on the respective monocomponent gels is investigated. Heteroassemblies built from colloidal building blocks are usually prepared by ligand removal or cross-linking, thus, both the surface chemistry and the destabilising agent play an essential role in the gelation process. Due to the diversity of the composition, morphology, and optical properties of the nanoparticles, a versatile route to fabricate functional heteroassemblies is of great demand. In the present work, the optics, morphology, and gelation mechanism of pure semiconductor and noble metal as well as their mixed nanoparticle gel networks are revealed. The influence of the gelation agents (bivalent and trivalent cations) on the structure-property correlation is elucidated by photoluminescence, X-ray photoelectron spectroscopy, and electron microscopy measurements. The selection of cations drastically influences the nano- and microstructure of the prepared gel network structures driven by the affinity of the cations to the ligands and the nanoparticle surface. This gelation technique provides a new platform to control the formation of porous assemblies based on semiconductor and metal nanoparticles.     

Preparative soft and reactive landing of multiply charged protein ions on a plasma-treated metal surface

Soft landing on a plasma-treated metal surface of multiply protonated protein ions from the gas phase results in a substantial retention of protein function, as demonstrated for trypsin and streptavidin. The majority of trypsin ions soft-landed at hyperthermal kinetic energies are undamaged and retain 72-98% of enzymatic activity after being washed into solution. A small fraction of trypsin ions that were landed at nominal kinetic energies of 130-200 eV remain tethered to the surface and show approximately 50% enzymatic activity. The streptavidin tetramer is found to dissociate to monomer units upon multiple charging in electrospray. The majority of soft-landed monomers can be washed into solution where they show affinity to biotin. The layer of streptavidin monomer that is immobilized on the surface can be detected if fluorescence-tagged and retains the ability to reversibly bind biotin. A mechanism is proposed to explain nondestructive protein ion discharge on the surface that considers proton migration from the soft-landed cations to the metal oxide layer and metal ion reduction by electron transfer from the bulk metal.     

Specific K+ Binding Sites as CO2 Traps in a Porous MOF for Enhanced CO2 Selective Sorption

Metal–organic frameworks (MOFs) can be fine‐tuned to boost sorbent‐sorbate interactions in order to improve gas sorption and separation performance, but the design of MOFs with ideal structural features for gas separation applications remains a challenge. Herein it is reported that unsaturated alkali metal sites can be immobilized in MOFs through a tetrazole based motif and that gas affinity can thereby be boosted. In the prototypal MOF of this type‐ NKU‐521 (NKU denotes Nankai University), K⁺ cations are effectively embedded in a trinuclear Co²⁺‐tetrazole coordination motif. The embedded K⁺ sites are exposed to the pores of NKU‐521 through water removal, and the isosteric heat (Q_st) for CO₂ is boosted to 41 kJ mol^‐1. The nature of the binding site is validated by molecular simulations and structural characterization. The K⁺ cations in effect serve as gas traps and boost the CO₂‐framework affinity, as measured by the Q_st, by 24%. In addition, the impact of unsaturated alkali metal sites upon the separation of hydrocarbons is evaluated for the first time in MOFs using ideal adsorbed solution theory (IAST) calculations and column breakthrough experiments. The results reveal that the presence of exposed K⁺ sites benefits gas sorption and hydrocarbon separation performances of this MOF.     

Comparative studies on the solvent extraction of transition metal cations by calixarene, phenol and ester derivatives

The ionophore solvent extraction of various alkali metal and transition metal cations from the aqueous phase to the organic phase was carried out by using diazo-coupling calix[n]arenes [p-(4-phenylazophenylazo)calix[4]arene (L1) and p-phenylazocalix[6]arene (L2)], phenol derivatives [2,6-dimethyl-3-phenylazophenol (L3), 2-(5-bromo-2-pyridylazo)-5-diethylamino phenol (L4), 2-chloro-4-nitro(phenylazo)-5-sec-butyl-2-phenol (L5) and 2-chloro-4-nitro(phenylazo)-5-tert-butyl-2-phenol (L6)], and ester derivatives [quinoline-8-benzoate (L7), phenyl-1,4-dibenzoate (L8), p-tolyltiobenzoate (L9)]. It was found that, all the compounds (L1-L9) examined showed selectivity for transition metal cations such as Ag+, Hg+ Hg2+, and poor efficiency for alkali metal cations (Na+ and K+). The best extraction efficiency was obtained with L1 and L4.     

The wetting of three component silicate glasses on platinum

Measurements of the contact angles of sessile drops of alkali silicate glasses, containing other oxide additions, on platinum have been used to study the role of the glass composition in the wetting processes. A model has been proposed which relates the degree of wetting to the competition between the substrate metal and cationic and anionic groups in the molten glass for the valency electron of non-bridging oxygen ions. An empirical relationship between equilibrium contact angle and the affinity for oxygen ions of cations in the glass supports this model.     

Polymeric precursor synthesis of Ba2Ti9O20

Ba₂Ti₉O₂₀ was synthesized by Pechini method using citric acid as a chelating agent and ethylene glycol as an esterification agent. The effects, of the pH of the starting solutions and the molar ratio of citric acid to total metal cations concentration on the formation of Ba₂Ti₉O₂₀, were investigated. Increasing the pH of the starting solutions enhances the formation of Ba₂Ti₉O₂₀, but the increase of the molar ratio of citric acid to total metal cations concentration retards the formation of Ba₂Ti₉O₂₀ due to increased diffusion distances. Single-phase Ba₂Ti₉O₂₀ was obtained at 1200 °C for 4 h when the molar ratio of citric acid to total metal cations concentration was unity, regardless of the pH of the starting solutions. Increasing the molar ratio of citric acid to total metal cations concentration up to 2, single-phase Ba₂Ti₉O₂ was synthesized at 1200 °C for 6 h for the precursors with pH 3.5 and 6, but not for the precursors with pH 2.0. DTA, TG, XRD, FT–IR spectroscopy and Raman spectroscopy were used to characterize the precursors and the derived oxide powders. Details of the synthesis and characterizations of the resultant products were given.     

Metal Cations in Efficient Perovskite Solar Cells: Progress and Perspective

Metal halide perovskite solar cells (PVSCs) have revolutionized photovoltaics since the first prototype in 2009, and up to now the highest efficiency has soared to 24.2%, which is on par with commercial thin film cells and not far from monocrystalline silicon solar cells. Optimizing device performance and improving stability have always been the research highlight of PVSCs. Metal cations are introduced into perovskites to further optimize the quality, and this strategy is showing a vigorous development trend. Here, the progress of research into metal cations for PVSCs is discussed by focusing on the position of the cations in perovskites, the modulation of the film quality, and the influence on the photovoltaic performance. Metal cations are considered in the order of alkali cations, alkaline earth cations, then metal cations in the ds and d regions, and ultimately trivalent cations (p‐ and f‐block metal cations) according to the periodic table of elements. Finally, this work is summarized and some relevant issues are discussed.     

Stimulus-responsive molecular rotors: Control of rotary motion in triptycene-ionophore systems with s-block metal cations

Triptycene derivatives bearing a pair of ionophores were synthesized and their rotational behaviors were observed with/without s-block metal cations as an external stimulus. In this study, oxyethylene-based ionophores were introduced at both bridgehead positions of triptycene as the stimulus receptors. The NMR experiments revealed the formation of complexes of the triptycenes with the s-block metal cations. We demonstrated that the rate (activation energy) of the internal rotation of the triptycyl moiety could be controlled by the formation of the complexes. We also found that the conformation of those complexes can be controllable with the species of metal cations.     

Photonic crystal aqueous metal cation sensing materials

We developed a polymerized crystalline colloidal array photonic material that senses metal cations in water at low concentrations (PCCACS). Metal cations such as Cu2+, Co2+, Ni2+, and Zn2+ bind to 8-hydroxyquinoline groups covalently attached to the PCCACS. At low metal concentrations (相似文献   

Synthesis and application of a novel mesoporous SBA-15 sorbent functionalized by 2,4 dinitrophenylhydrazine (DNPH) for simultaneous removal of Pb(II), Cr(III), Cd(II) and Co(II) from aqueous solutions: Experimental design,kinetic, thermodynamic,and isotherm aspects

Heavy metal cations are the most common group of pollutants which significantly contribute to the pollution of aquatic systems. Among the heavy metal cations, lead, chromium, cadmium and cobalt are the most abundant cations present in wastewaters. In this work, a novel sorbent was synthesized via functionalization of chloro-mesoporous SBA-15 with 2,4- dinitrophenylhydrazine. The adsorbent was identified by various characterization techniques and then was used for adsorption of Pb(II), Cr(III), Cd(II), and Co(II). and then the response surface methodology was employed to study the influence, and interaction of different parameters. According to the results, the optimized adsorption capacity of 242.50, 214.72, 187.86, 166.46 mg/g was obtained respectively for the studied cations. furthermore, the sorption of cations was fast and the process achieve to equilibrium within 23.65, 20.31, 24.05 min for Pb(II), Cr(III), Cd(II) and within 19.88 min for Co(II). The adsorbent regenerated by a mixture of nitric acid and methanol could be recycled without losing a remarkable amount of capacity. The results analyzed with various isotherm models were best conformed to the Langmuir model.     

复合金属离子抗菌沸石的制备及研究

以13X沸石为载体,用不同的方法制备了四类金属离子抗菌沸石.用WAXD、EDS、AAS、抑菌环法等表征了抗菌沸石的结构、抗菌金属离子相对含量和抗菌性能.结果表明,金属离子交换过程没有改变13X的基本结构,进入13X的抗菌金属离子具有缓释性. 采用复合离子交换法制备的多金属的含银抗菌沸石具有最佳抑菌性能,其相对抗菌强度优于阳性对照AGZ-330,且成本较低.复合金属离子抗菌沸石较高的多种抗菌离子含量及缓释能力具有协同抑菌作用和广谱抑菌性.     

Differentially ligand-functionalized microcantilever arrays for metal ion identification and sensing

A microcantilever array sensor with cantilevers differentially functionalized with self-assembled monolayers (SAMs) of thiolated ligands is prepared by simultaneous capillary coating. This array is described for the detection of metal ions including Li+, Cs+, Cu2+, Co2+, Fe3+, and Al3+. Binding of the charged metal cations to the surface of the microcantilever sensors produces surface stress that causes bending of the cantilevers that is detected as tip deflection using an array of vertical cavity surface emitting lasers and a position-sensitive detector. Optimization studies of the nanostructured dealloyed surface were performed for SAMs based on their response to Cu2+ cations. Sensor performance experiments demonstrate good sensitivity toward metal ions, with limits of detection as low as 10(-8) molar. A multiplex capillary coating method for cantilever array creation is demonstrated and validated based on surface-enhanced Raman spectra obtained from adjacent cantilevers that were functionalized with different thiolated SAMs. The cantilever array coated with a range of thiolated ligands was exposed to the group of metal ions. The response characteristics of each metal ion show substantial diversity, varying not only in response magnitude, but response kinetics. A pattern recognition algorithm based on a combination of independent component analysis and support vector machines was able to validate that the sensor array response profiles produced enough information content that metal ions could be reliably classified with probabilities as high as 89%.     

Engineering Solvation Complex–Membrane Interaction to Suppress Cation Crossover in 3 V Cu‐Al Battery

Metal–metal batteries such as the 3 V Cu‐Al system are highly desirable for large‐scale energy storage owing to their low cost and excellent scalability of Cu and Al foils. However, the dissolved Cu cations will crossover from the cathode to the anode leading to poor electrochemical performance. In this work, it is demonstrated that the reversibility of the Cu‐Al battery depends strongly on the interaction of the Cu ions with the electrolyte solvent and subsequently the affinity of the solvated Cu ion with the membrane separator. Specifically, a series of common carbonate‐based electrolyte solvents are investigated via molecular dynamics and contact angle measurements to understand the interaction between the solvents and a polypropylene (PP) membrane, as well as that between cations and solvent. Among different solvents, fluoroethylene carbonate (FEC) is shown to drastically enhance the coulombic efficiency to 97%, compared to that of 27% with dimethyl carbonate. Remarkable cyclability of a 3 V Cu‐Al battery with 3 m LiTFSI FEC and PP membrane up to 1000 cycles is further demonstrated. This finding opens new opportunities for the development of low‐cost, high performance Cu‐Al systems for stationary applications.     

Fluorescence sensor array for metal ion detection based on various coordination chemistries: general performance and potential application

A sensor array containing 9 cross-reactive sensing fluorescent elements with different affinity and selectivity to 10 metal cations (Ca(2+), Mg(2+), Cd(2+), Hg(2+), Co(2+), Zn(2+), Cu(2+), Ni(2+), Al(3+), Ga(3+)) is described. The discriminatory capacity of the array was tested at different ranges of pH and at different cation concentrations using linear discriminant analysis (LDA). Qualitative identification of cations can be determined with over 96% of accuracy in a concentration range covering 3 orders of a magnitude (5-5000 microM). Quantitative analysis can be achieved with over 90% accuracy in the concentration range between 10 and 5000 microM. The array performance was also tested in identification of nine different mineral water brands utilizing their various electrolyte compositions and their Ca(2+), Mg(2+), and Zn(2+) levels. LDA cross-validation routine shows 100% correct classification for all trials. Preliminary results suggest that similar arrays could be used in testing of the consistency of the purification and manufacturing process of purified and mineral waters.     

Colorimetric and fluorescent sensing of transition metal ions in aqueous medium by salicylaldimine based chemosensor

The cation sensing property of highly sensitive chromogenic receptor N, N′-bis (salicylidine)-o-phenylene diamine (receptor 1) was studied by visual observation, UV–vis spectroscopy and fluorescence spectroscopy. The proposed study has been targeted to sense the first transition series metal cations like Fe³⁺, Co²⁺, Ni²⁺ and Cu²⁺. Binding affinity toward Cu²⁺ is found to be of higher magnitude compared to the other three cations mentioned. Receptor 1 on binding with Fe³⁺, Co²⁺ Ni²⁺ and Cu²⁺ ions shows fluorescence enhancement which is due to the inhibition of PET mechanism.     

Studies on divalent ion uptake of transition metal cations by calcite through crystallization and cation exchange process

The uptake of transition metal cations of Fe, Cu, Zn, Cd and Pb with calcium carbonate in the form of calcite was investigated. The uptake reaction was found to be in the following order: Pb²⁺ > Cu²⁺ Zn²⁺ > Cd²⁺ Fe²⁺; and the amount of uptake (meq/g) cations has been found to increase with the increase of the metal ion concentration and reaction time. The uptake of these ions was mainly considered to be due to the crystallization that happens through decomposition reaction mechanism as in case of Pb²⁺, Cu²⁺ and Zn²⁺ and cation exchange of surface Ca²⁺-ions present in lattice structure of carbonate solid with metal cations, as in the case of Fe²⁺ and Cd²⁺. The different affinities of calcite toward these cations can be used for waste ions fixations or decontamination.