Addition Of Other Metal Ions Research Articles

Novel dipodal Schiff base compounds: Synthesis, characterization and spectroscopic studies

Two novel dipodal Schiff base compounds 1,2-benzyloxy-bis-[2-(benzylideneamino)phenol, L1 and 1,2-benzyloxy-bis[3-(benzylideneamino)pyridine], L2 were synthesized. Their sensing actions were confirmed by UV–Vis absorbance and emission spectroscopic studies in presence of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Sn(II), Cd(II) and Pb(II) in methanol medium (1×10–4M). It was found that the dipodal compounds can selectively bind to Cu(II) and Pb(II) metal ions with a significant change in its emission and absorption spectra, while the addition of other metal ions (Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Sn(II), Cd(II) and Pb(II)) produces insignificant or minor changes. The host–guest complexes formed were determined by Job’s plot method. As a chemosensor, L1 and L2 dipodal Schiff base compounds shows a specific selectivity towards Cu(II) and Pb(II) ions in according to all spectroscopic data.

Enhanced Fluorescence Quenching of 2‐Thiohydantoin‐Containing Conjugated Polymers: Applications for Ion Sensing

A novel poly(phenylene ethynylene) containing 2‐thiohydantoin [poly(1)] is synthesized. The addition of F− quenches the fluorescence, while the fluorescence of the solution only changes slightly upon addition of other anions, indicating the sensing ability of poly(1) toward F−. The addition of Ag+ quenches the fluorescence of the polymer, whereas the addition of other metal ions results in only slight changes to the fluorescence. Compared with its small‐molecule counterpart, the Stern–Volmer quenching constants of poly(1) toward F− and Ag+ are 165 and 105 times greater, respectively. This result indicates the amplified quenching effect of poly(1). image

Coumarin modified rhodamine derivative: Fluorescent chemosensor selectively recognizing Al3+ and Ca2+

A fluorescent probe with a coumarin moiety bound to rhodamine 6G hydrazide(1) was synthesized. Its sensing behavior toward various metal ions was investigated with fluorescence methods. Compound 1 displays different fluorescence emission responses to Al3+ and Ca2+ at the same excitation wavelength in the visible light region, while no changes occur after the addition of other metal ions. The binding ratios of the complexs of 1-Al3+ and 1-Ca2+ are both 2:1 according to the Job plot and high resolution mass spectrometer(HRMS) experiments. Moreover, emission spectrum of 1-Ca2+ complex and absorption spectrum of the rhodamine dyes overlap largely. When Al3+ was added to the 1-Ca2+ system, calcium in complex 1-Ca2+ can be displaced by Al3+, resulting in the output of another ratiometric sensing signal, which demonstrates that the 1-Ca2+ complex can be served as a new and effective fluorescence resonance energy transfer(FRET) donor for rhodamine derivatives.

Luminescent Fluorene-Based Bis-Pyrazolyl Aniline Ligand for Aluminum Detection.

The design, synthesis, and photophysical properties of a new fluorene-based fluorescent chemosensor, 4-((E)-2-(2-(benzo[d]thiazol-2-yl)-9,9-diethyl-9H-fluoren-7-yl)vinyl)-N,N-bis((3,5-dimethyl-1H-pyrazol-1-yl)methyl)benzenamine (AXF-Al), is described for the detection of Al3+. AXF-Al exhibited absorption at 382nm and strong fluorescence emission at 542nm (fluorescence quantum yield, Φ F, of 0.80). The capture of Al3+ by the pyrazolyl aniline receptor resulted in nominal change in the linear absorption (372nm) but a large hypsochromic shift of 161nm in the fluorescence spectrum (542 to 433nm, Φ F = 0.88), from which Al3+ was detected both ratiometrically and colorimetrically. The addition of other metal ions, namely Mg2+, Ca2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg 2+ and Pb2+, produced only minimal changes in the optical properties of this probe. The emission band of this probe was also accessed by two-photon excitation in the near-IR, as two-photon absorption (2PA) is important for potential applications in two-photon fluorescence microscopy (2PFM) imaging. The 2PA cross section of the free fluorenyl ligand AXF-Al was 220GM at 810nm and 235GM at 810nm for the Al-ligand complex, practically useful properties for 2PFM.

Azobenzene chemosensor based on nitrogen chelator for the detection of Cu (II) ion in aqueous medium

Abstract A bis-pyridine unit containing azobenzene chemosensor for Cu2 + ion is designed and synthesized with good yield. The structure of the receptor I is determined by FT-IR, 1H NMR, 13C NMR, ESI-MS and single crystal XRD. The receptor I is constructed on the basis of internal charge transfer (ICT) mechanism with bis-pyridine unit acting as the binding part for Cu2 + ion. In solution, the proposed receptor I produces a cation induced 120 nm blue shift for Cu2 + ion from 457 nm to 337 nm with remarkable colour change from red to colourless. Whereas no significant colour change is observed upon addition of other metal ions in aqueous HEPES buffer (pH 7.0). Moreover, spectroscopic studies confirm the formation of 1: 1 stoichiometry between the receptor I and Cu2 + ion with an association constant of ca. 1.45 × 106 M− 1. The receptor I is highly specific to Cu2 + ions in aqueous solution attributed to the rational design of the molecular structure.

A Highly Selective Chemosensor Probe for Ag<sup>+</sup> in 50% THF/H<sub>2</sub>O

A highly selective chemosensor for Ag+ based on heterocyclic compound Diethyl 6-anilino-5H-2,3-dithia-5,7-diazacyclopenta (cd) indene-1,4-dicarboxylate (D1) was investigated. The deprotonation of N-H was observed easily in spectra of D1 (2.5×10-5 M) in 50% H2O/THF solution after NaOH addition, and the deprotonated D1 could interact with Ag+, resulted in the sharp decrease of deprotonated absorption. The addition of other metal ions would not produce an obvious change, which means quite extreme selectivity for Ag+ compared with other metal ions. The LOD of the method to detect Ag+ was 8.07×10-8 M. It is indicated that a novel high selective chemosensor for Ag+ was build up.

SCREENING AND CHARACTERIZATION OF L-GLUTAMINASE PRODUCED BY BACTERIA ISOLATED FROM SANGIHE TALAUD SEA

L-glutaminase (L-glutamine amidohydrolase, EC 3.5.1.2) is a very important enzyme due to its role as flavor enhancer and antileukemic agent. Salt-tolerant L-glutaminase produced bymarine bacteria is favorable in food industries. This study describes the screening of L- glutaminase producing marine bacteria from Sangihe-Talaud Sea, North Sulawesi, Indonesia.Screening of L-glutaminase was performed using a liquid medium and identification of selected isolate was performed using molecular-based 16S rDNA. Results showed that there were 7 isolates produced positive results of L-glutaminase, and one of them (II.1 isolate) produced the highest activity, i.e 147.99 U/L, equivalent to the specific activity of 62.32 U/mg. The isolate then selected for further study. Bacterial identification based on 16S rRNA sequencing has revealed that the isolate was 96% similar to Pseudomonas aeruginosa strain CG-T8. Characterization of extracellular L-glutaminase from the II.1 isolate showed that the enzyme worked optimally at temperature of 37-45 °C and pH 7. The enzyme was stable when NaCl solution was added up to 8% and began to decrease on addition of NaCl solution of 16% and 20% with relative activity of 79% and 74%, respectively. The effect of metal ions, e.g Mn2+, Mg2+, and Co2+ in the form of chloride salt, were able to increase enzyme activity, whereas the addition of other metal ions (Zn2+, Fe3+, and Ca2+) decreased the activity. The molecular weights of L-glutaminase was estimated around42 kDa and 145 kDa.

Highly sensitive and selective chemosensor for Cu2+ based on a Schiff base

A new chemosensor based on a Schiff base has been designed and synthesized. Its sensing behavior toward various metal ions was investigated by fluorescence and UV-Vis spectroscopic methods. The fluorescence of the sensor was quenched and the color rapidly changed from canary yellow to brown after the addition of Cu2+, while no changes occurred after the addition of other metal ions, which contributes to the detection of Cu2+ with naked eyes. The fluorescence quantum yield of the ligand was calculated to be 0.52. The corresponding detection limit of Cu2+ was 5.721×10−7 mol/L, and the 1:1 binding mode of the sensor with Cu2+ was revealed by Job’s plot.

Dansyl derivative functionalized Fe3O4@SiO2fluorescent probe for detection and removal of Hg2+in aqueous solution

In the present work, a novel dansyl group functionalized Fe3O4@SiO2 magnetic nanomaterial with a core–shell structure was developed, aiming to detect and remove Hg2+ from aqueous media. The multifunctional nanocomposite shows excellent fluorescence sensitivity and selectivity towards Hg2+ over other metal ions (Na+, K+, Mg2+, Al3+, Ca2+, Cd2+, Ni2+, Co2+, Fe3+, Zn2+, Pb2+, Cu2+, Ag+). Concentrations as low as 10−8 M can be detected and the addition of other metal ions has a negligible influence on the fluorescence emission. Regarding the reversibility of the nanosized sensor, the fluorescence of the DAP-Fe3O4@SiO2 nanocomposite in the presence of Hg2+ ions is found to be almost reversible when treated with iodide anion. Additionally, the nanocomposite can be easily separated from solutions by adding an external magnetic field. Moreover, the functionalized nanosphere shows a good adsorption capacity to Hg2+, which makes it repeatedly applicable for simultaneous Hg2+ sensing and removal from polluted water. These results indicate that the multifunctional nanocomposite may find potential applications for simple detection and easy removal of Hg2+ in biological and environmental areas.

Selective fluorescence sensor for Al3+ and Pb2+ in physiological condition by a benzene based tripodal receptor

We have synthesized a benzene based tripodal receptor containing naphthalene motifs as signaling unit. The receptor can selectively bind Al3+/Pb2+ metal ions with a significant change in its fluorescence and UV/Vis spectra, while the addition of other metal ions (Na+, K+, Ca2+, Mg2+, Cr3+, Hg2, Cu2+, Zn2+, Fe2+, Co2+, Ni2+, Cd2+, and Ag+) produces insignificant or minor changes. The formation of receptor–metal ion complex is also proved by NMR and mass spectroscopic analysis.

Core-shell mesoporous silica nanospheres used as Zn2+ ratiometric fluorescent sensor and adsorbent

Core-shell mesoporous silica nanospheres encapsulated with rhodamine 101 into the solid core and 8-aminoquinoline derivatives into the mesoporous shell were used as a ratiometric fluorescent sensor to detect metal ions, which shows a high selectivity and sensitivity to Zn2+. Concentrations as low as 5 × 10−8 M can be detected and the addition of other metal ions has a negligible influence on the fluorescence emission. Moreover, the dye-doped nanospheres show excellent photostability, no dye leaking and a good adsorption capacity to Zn2+, which make it repeatedly applicable for simultaneous heavy metal ion sensing and removal from polluted water.

Creation of 3,4-bis-triazolocoumarin–sugar conjugates via flourogenic dual click chemistry and their quenching specificity with silver(I) in aqueous media

Fluorogenic click chemistry has recently emerged as an ingenious and powerful tool toward numerous biochemical purposes. We describe herein the use of dual click chemistry toward the fluorescence restoration of a fluorogenic coumarin on epimeric dipropargyl sugar scaffolds and their practical utility in selective metal ion detection. The dual click reactions were smoothly proceeded under microwave irradiation between silylated 3,4-di- O-propynyl gluco- or galactoside and 3-azidocoumarin, forming fluorescently reactivated bis-triazolocoumarins on sugar templates. Subsequent desilylation resulted in the OH-glycosides with desired water solubility. The following photochemical study disclosed that their fluorescence could be uniquely quenched by silver(I) in aqueous media with very minor responses to the addition of other metal ions. This research would presumably prompt the efficient creation of water soluble and potentially low toxic chemosensors via the fluorogenic dual click chemistry in using the universally existent sugars as the central scaffold.

Naphthylthiourea-modified permethylcyclodextrin as a highly sensitive and selective “turn-on” fluorescent chemosensor for Hg2+ in water and living cells

A naphthylthiourea-modified cyclodextrin (1) and its urea derivative (2) were synthesized, and their fluorescence behaviors in the presence of various metal ions were investigated. Significantly, 1 showed a highly sensitive and selective fluorescence sensing ability for Hg(2+) over other metal ions in both water and living cells. That is, the addition of Hg(2+) to an aqueous solution of 1 gave a significantly enhanced fluorescence at ~380 nm. In contrast, the addition of other metal ions induced negligible fluorescence changes. The possible mechanism may be due to the transformation of thiourea to urea by Hg(2+)-induced desulfurization in water.

Structures and luminescent properties of a series of Ln–Ag heterometallic coordination polymers

Eight new 4f–4d heterometallic coordination polymers have been synthesized using pyridine-2,6-dicarboxylic acid (H2PDA) as ligand under hydrothermal conditions. {[PrAg(PDA)2(H2O)3]·2.5H2O}n (1) comprises a 2D grid-like net, and the grid structure is assembled through a Pr4Ag2 motif as the building block. The subsequent six complexes [LnAg(PDA)2(H2O)3]·3H2O}n (Ln = Ce3+, 2; Nd3+, 3; Sm3+, 4; Eu3+, 5; Tb3+, 6; Dy3+, 7) are 1D double-chain coordination polymers. In 2–7, the Ln3+ and Ag+ ions are linked by carboxylic O bridges to form the helical chains, while the right-handed and left-handed chains are linked through carboxylic O bridges to form the double-helical chain. Additionally, the lattice H2O molecules linked by hydrogen bonds construct the helical water chain. {[CeAg2(PDA)3(Py)4]·H2O}n (8) (Py = pyridine) contains one Ce4+ ion and displays a 1D wave-like chain, in which partial H2PDA ligands were decomposed to pyridine. Luminescent studies reveal that the emission intensity of 7 significantly increases with the introduction of Mg2+ ions into the system of 7, whereas the addition of other metal ions causes emission intensity to remain the same or even decrease. Therefore, complex 7 may serve as a luminescent probe of Mg2+.

Morphological consequences of metal ion–peptide vesicle interaction

The triskelion peptide conjugate 1, having a Trp–Trp dipeptide unit on the three arms, was synthesized and studied for the interaction of peptide-based soft structures with metal ions, by fluorescence and microscopic analyses. We observed that fluorescence was significantly quenched upon addition of Cu(II) metal ions, whereas the addition of other metal ions also caused moderate to insignificant changes in the fluorescence emission, suggesting specificity of this triskelion peptide 1 for Cu(II) ions. The addition of Cu(II) and other metal ions also altered the morphology of preformed vesicles obtained from triskelion peptide 1 in a concentration-dependent fashion, as observed from microscopic analysis. Such metal-responsive soft structures may find potential use as novel materials for delivery and sensing applications.

A selective, fluorescent probe for Hg 2+ detection in aqueous solution

A novel fluorescent probe, 5-(2-benzothzaole)-2-thiophene boronic acid ( 1), for Hg 2+ detection in aqueous solution was synthesized. ( 1) exhibited very strong fluorescence emission ( ϕ = 0.92) in tris–HCl (pH 7.42) buffer aqueous solution. It was found that the fluorescence emission of ( 1) was quenched significantly upon addition of Hg 2+ in buffer aqueous solution, whereas no marked fluorescence quenching was detected with addition of other metal ions (Ba 2+, Ca 2+, Cd 2+, Co 2+, Cu 2+, Mg 2+, Fe 2+, Fe 3+, Ni 2+, Pb 2+, Zn 2+, Na +, K +) expect for Fe 2+ and Fe 3+, for which a small fluorescence quenching was detected in same condition. Competition experiment showed that no obvious interference was observed in its fluorescence while ( 1) performed the titration with Hg 2+ in the different mixtures of metal ions.

Mesitylene based azo-coupled chromogenic tripodal receptors—a visual detection of Ag(I) in aqueous medium

A series of novel tripodal ligands 3a– d, based on a mesitylene anchor, containing aza-thioethers as donor atoms and coupled with 4-(4/3/2-nitrophenyl)azophenol or 4-(2-chlorophenyl)azophenol have been synthesized as chromogenic receptors, which are highly selective for silver(I). The complexation behavior of 3a– d with various metal ions has been evaluated by UV–vis spectrometry in dioxane/water (1:9/v:v) solution at 25 °C. The UV–vis spectra show that the complexation of 3a– c with Ag + have pronounced bathochromic shifts accompanied by a unique color change in the solution from yellow to red, which is visible with the naked eye. The ligands do not show any significant change on addition of other metal ions like Li +, Na +, K +, Sr 2+, Ca 2+, Cd 2+, Zn 2+, Hg 2+, Pb 2+, Ni 2+, and Cu 2+ and thus are highly specific and selective for Ag + in the aqueous medium.

Effect of transition metal ions on photocatalytic activity of ZnO in bleaching of some dyes

The photocatalytic bleaching of some dyes (erythrosin-B, fast green FCF and eosin Y) was carried in the presence of semiconducting zinc oxide and was observed spectrophotometrically. The effects of various operating variables like pH, concentration of dyes, amount of semiconductor and light intensity on the efficiency of the reaction were also observed. Attempts have been made to study the effect of the addition of other metal ions (Fe2+, Ni2+, Ag+, Cu2+, Co2+, V2+ and Mn2+). All the added metal ions increase the reaction rate to some extent. It was also observed that Fe2+ is most effective in photobleaching of erythrosin-B, whereas V2+ is more effective in the cases of fast green FCF and eosin Y. A tentative mechanism has been proposed.

Identification of an ITPase/XTPase in Escherichia coli by Structural and Biochemical Analysis

Inosine triphosphate (ITP) and xanthosine triphosphate (XTP) are formed upon deamination of ATP and GTP as a result of exposure to chemical mutagens and oxidative damage. Nucleic acid synthesis requires safeguard mechanisms to minimize undesired lethal incorporation of ITP and XTP. Here, we present the crystal structure of YjjX, a protein of hitherto unknown function. The three-dimensional fold of YjjX is similar to those of Mj0226 from Methanococcus janschii, which possesses nucleotidase activity, and of Maf from Bacillus subtilis, which can bind nucleotides. Biochemical analyses of YjjX revealed it to exhibit specific phosphatase activity for inosine and xanthosine triphosphates and have a possible interaction with elongation factor Tu. The enzymatic activity of YjjX as an inosine/xanthosine triphosphatase provides evidence for a plausible protection mechanism by clearing the noncanonical nucleotides from the cell during oxidative stress in E. coli.

MtuA, a lipoprotein receptor antigen from Streptococcus uberis, is responsible for acquisition of manganese during growth in milk and is essential for infection of the lactating bovine mammary gland.

A mutant strain of Streptococcus uberis (AJS001) that was unable to grow in bovine milk was isolated following random insertional mutagenesis. The level of growth in milk was restored to that of the parental strain (strain 0140J) following addition of MnSO(4) but not following addition of other metal ions. The mutant contained a single insertion within mtuA, a homologue of mtsA and psaA, which encode metal-binding proteins in Streptococcus pyogenes and Streptococcus pneumoniae, respectively. Strain AJS001 was unable to infect any of eight quarters on four dairy cows following intramammary challenge with 10(5) CFU. Bacteria were never recovered directly from milk of these animals but were detected following enrichment in Todd-Hewitt broth in three of eight milk samples obtained within 24 h of challenge. The animals showed no inflammatory response and no signs of mastitis. Three mammary quarters on two different animals simultaneously challenged with 600 CFU of the parental strain, strain 0140J, became colonized, shed high numbers of S. uberis organisms in milk, displayed a marked inflammatory response to infection, and showed overt signs of mastitis. These data indicate that mtuA was required for efficient uptake of Mn(2+) during growth in bovine milk and infection of the lactating bovine mammary gland.