Tested Metal Ions Research Articles

Highly sensitive and selective rhodamine Schiff base “off-on” chemosensors for Cu2+ imaging in living cells

Abstract Three new rhodamine Schiff base sensors 1a–1c have been designed and synthesized as highly sensitive and selective “off-on” chemosensors for Cu2+ detection via the rhodamine ring-opening approach. The sensors display remarkably Cu2+-selective orange fluorescence and pink color switch over a wide range of tested metal ions. Fluorescent imaging of Cu2+ in living cells is also successfully demonstrated.

A Highly Copper‐Selective Ratiometric Fluorescent Sensor Based on BODIPY

AbstractA new ratiometric fluorescent sensor (1) for Cu2+ based on 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BODIPY) with di(2‐picolyl)amine (DPA) as ion recognition subunit has been synthesized and investigated in this work. The binding abilities of 1 towards different metal ions such as alkali and alkaline earth metal ions (Na+, K+, Mg2+, Ca2+) and other metal ions ( Ba2+, Zn2+, Cd2+, Fe2+, Fe3+, Pb2+, Ni2+, Co2+, Hg2+, Ag+) have been examined by UV‐vis and fluorescence spectroscopies. 1 displays high selectivity for Cu2+ among all test metal ions and a ∼10‐fold fluorescence enhancement in I582/I558 upon excitation at visible excitation wavelength. The binding mode of 1 and Cu2+ is a 1:1 stoichiometry determined via studies of Job plot, the nonlinear fitting of the fluorometric titration and ESI mass.

Sensor activity and logic behaviour of PET based dihydroimidazonaphthalimide diester

An ester terminated dihydroimidazonaphthalimide as multi-functional logic device is presented. Due to the optical changes as a function of pH this simple molecule is able to act as a molecular pH metre, a digital comparator and a half-adder. It was demonstrated that the dihydroimidazonaphthalimide comparator could be used as a fundamental element of an optical device for control of pH windows. Also, the ability of the device to detect metal ions in DMF and in water/DMF (3:1, v/v) at different pHs has been evaluated by monitoring the changes of its fluorescence intensity. Among the tested metal ions (Cd2+, Co2+, Cu2+, Fe3+, Ni2+, Pb2+, Zn2+, Bi3+, Hg2+ and Ag+) only Fe3+ and Bi3+ were efficiently detected. In water/DMF (3:1, v/v) XOR and XNOR logic gates are presented using pH and Fe3+ as chemical inputs based on encoding binary digits of logical conventions.

New water-soluble highly selective fluorescent chemosensor for Fe (III) ions and its application to living cell imaging

A new rhodamine-based chemosensor exhibits excellent selectivity for Fe3+ ions over a wide range of tested metal ions Ag+, Al3+, Ca2+, Cd2+, Co2+, Cr3+, Cu2+, Fe2+, Hg2+, Mg2+, Mn2+, Ni2+, Pb2+, and Zn2+ in an aqueous solution. The binding of Fe3+ to chemosensor 1 produces an absorption band at 564 nm and an emission band at 588 nm because Fe3+-binding induces ring-opening of the spirolactam in 1. The binding ratio of the 1–Fe3+ complexes was determined to be 1:1 according to a Job plot. The association constant (Ka) of Fe3+ binding in chemosensor 1 was 6.9 × 103 M−1. The maximum fluorescence enhancement caused by Fe3+ binding in chemosensor 1 occurred at a pH range of 6–7.5. The fluorescence microscopy experiments in this study demonstrated that chemosensor 1 can be used as a fluorescent probe for detecting Fe3+ in living cells.

Design, synthesis and sensor activity of a highly photostable blue emitting 1,8-naphthalimide

This work reports on the design, synthesis and photophysical properties of a highly photostable blue emitting 1,8-naphthalimide, containing hindered amine radical scavenger moiety and a tertiary amine cation receptor. The novel compound was configured as “fluorophore-spacer-receptor” system based on photoinduced electron transfer. Photophysical characteristics of the examined compound were investigated in DMF and water/DMF (4:1, v/v) solution. The ability of the new compound to detect cations was evaluated by the changes in its fluorescence intensity in the presence of metal ions (Cu2+, Pb2+, Cd2+, Ni2+, Co2+, Fe3+ and Zn2+) and protons. The presence of metal ions and protons was found to disallow a photoinduced electron transfer resulting in enhancement of the 1,8-naphthalimide fluorescence intensity. Among the tested metal ions only Cu2+ was efficiently detected. Also, it is clearly shown that the 2,2,6,6-tetramethylpiperidine fragment, incorporated in the structure of the novel 1,8-naphthalimide, considerably improves the sensor's photostability, sensitivity and selectivity.

Cloning, High-Level Expression, Purification, and Properties of a Novel Endo-β-1,4-Mannanase from Bacillus subtilis G1 in Pichia pastoris

A novel gene coding for an endo-beta-1,4-mannanase (manA) from Bacillus subtilis strain G1 was cloned and overexpressed in P. pastoris GS115, and the enzyme was purified and characterized. The manA gene consisted of an open reading frame of 1,092 nucleotides, encoding a 364-aa protein, with a predicted molecular mass of 41 kDa. The beta-mannanase showed an identity of 90.2-92.9% (< or =95%) with the corresponding amino acid sequences from B. subtilis strains deposited in GenBank. The purified beta- mannanase was a monomeric protein on SDS-PAGE with a specific activity of 2,718 U/mg and identified by MALDITOF mass spectrometry. The recombinant beta-mannanase had an optimum temperature of 45 degrees C and optimum pH of 6.5. The enzyme was stable at temperatures up to 50 degrees C (for 8 h) and in the pH range of 5-9. EDTA and most tested metal ions showed a slightly to an obviously inhibitory effect on enzyme activity, whereas metal ions (Hg2+, Pb2+, and Co2+) substantially inhibited the recombinant beta-mannanase. The chemical additives including detergents (Triton X- 100, Tween 20, and SDS) and organic solvents (methanol, ethanol, n-butanol, and acetone) decreased the enzyme activity, and especially no enzyme activity was observed by addition of SDS at the concentrations of 0.25-1.0% (w/v) or n-butanol at the concentrations of 20-30% (v/v). These results suggested that the beta-mannanase expressed in P. pastoris could potentially be used as an additive in the feed for monogastric animals.

A new photoinduced fluorescent switch based on a photochromic diarylethene with a rhodamine fluorophore

A new photoinduced fluorescent switch based on a photochromic diarylethene with a rhodamine fluorophore has been successfully explored. The target compound exhibits excellent photochromism with good fatigue-resistance upon photo-irradiation. Upon addition of Cr(III), the color of the diarylethene turns from colorless to pink accompanied with a 300-fold increase in fluorescence emission intensity in methanol. In the presence of Cr(III), an efficient FRET process from the rhodamine moiety (FRET donor) to the closed-ring diarylethene moiety (FRET acceptor) occurs upon UV light stimuli, and its emission intensity can be recovered upon irradiation with visible light. Also, the ability of the compound to detect metal ions has been evaluated by monitoring the changes of emission intensity in methanol. Amongst the tested metal ions, only Cr(III), Al(III) and Fe(III) are efficiently detected. The result indicates that the diarylethene can selectively recognize Cr(III) with significant color and fluorescence changes.

Gold Nanoparticle–Aluminum Oxide Adsorbent for Efficient Removal of Mercury Species from Natural Waters

We report a new adsorbent for removal of mercury species. By mixing Au nanoparticles (NPs) 13 nm in diameter with aluminum oxide (Al(2)O(3)) particles 50-200 μm in diameter, Au NP-Al(2)O(3) adsorbents are easily prepared. Three adsorbents, Al(2)O(3), Au NPs, and Au NP-Al(2)O(3), were tested for removal of mercury species [Hg(2+), methylmercury (MeHg(+)), ethylmercury (EtHg(+)), and phenylmercury (PhHg(+))]. The Au NP adsorbent has a higher binding affinity (dissociation constant; K(d) = 0.3 nM) for Hg(2+) ions than the Al(2)O(3) adsorbent (K(d) = 52.9 nM). The Au NP-Al(2)O(3) adsorbent has a higher affinity for mercury species and other tested metal ions than the Al(2)O(3) and Au NP adsorbents. The Au NP-Al(2)O(3) adsorbent provides a synergic effect and, thus, is effective for removal of most tested metal ions and organic mercury species. After preconcentration of mercury ions by an Au NP-Al(2)O(3) adsorbent, analysis of mercury ions down to the subppq level in aqueous solution was performed by inductively coupled plasma mass spectrometry (ICP-MS). The Au NP-Al(2)O(3) adsorbent allows effective removal of mercury species spiked in lake water, groundwater, and seawater with efficiencies greater than 97%. We also used Al(2)O(3) and Au NP-Al(2)O(3) adsorbents sequentially for selectively removing Hg(2+) and MeHg(+) ions from water. The low-cost, effective, and stable Au NP-Al(2)O(3) adsorbent shows great potential for economical removal of various mercury species.

A Novel endo-1,4-β-Mannanase from Bispora antennata with Good Adaptation and Stability over a Broad pH Range

An endo-β-1,4-mannanase encoding gene, man5, was cloned from Bispora antennata CBS 126.38, which was isolated from a beech stump. The cDNA of man5 consists of 1,299 base pairs and encodes a 432-amino-acid protein with a theoretical molecular mass of 46.6kDa. Deduced MAN5 exhibited the highest amino acid sequence identity of 58% to a β-mannanase of glycoside hydrolase family 5 from Aspergillus aculeatus. Recombinant MAN5 was expressed in Pichia pastoris and purified to electrophoretic homogeneity. The specific activity of the final preparation towards locust bean gum was 289 U mg(-1). MAN5 showed optimal activity at pH 6.0 and 70°C and had good adaptation and stability over a broad range of pH values. The enzyme showed more than 60% of peak activity at pH 3.0-8.0 and retained more than 80% of activity after incubation at 37°C for 1h in both acid and alkaline conditions (pH 4.0-11.0). The K (m) and V (max) values were 1.33mgml(-1) and 444μmolmin(-1)mg(-1) and 1.17mgml(-1) and 196μmolmin(-1)mg(-1) for locust bean gum and konjac flour, respectively. Of all tested metal ions and chemical reagents, Co(2+), Ni(2+), and β-mercaptoethanol enhanced the enzyme activity at 1mM, whereas other chemicals had no effect on or partially inhibited the enzyme activity. MAN5 was highly resistant to acidic and neutral proteases (trypsin, α-chymotrypsin, collagenase, subtilisin A, and proteinase K). By virtue of the favorable properties of MAN5, it is possible to apply this enzyme in the paper and food industries.

Peroxidase mimicking DNA–gold nanoparticles for fluorescence detection of the lead ions in blood

Oligonucleotide (T30695) modified gold nanoparticles (T30695-Au NPs) have been prepared and employed for quantification of lead ions (Pb(2+)) in blood. The detection of Pb(2+) ions is through the formation of Au-Pb alloys and oligonucleotide-Pb(2+) complexes that catalyze the H(2)O(2)-mediated oxidation of non-fluorescent Amplex UltraRed (AUR) to form a highly fluorescent oxidized AUR product. Surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOF MS) and inductively coupled plasma mass spectrometry (ICP-MS) revealed the formation of Au-Pb alloys on the surfaces of the 40T30695-Au NPs (i.e., the system featuring 40 molecules of T30695 per Au NP) in the presence of Pb(2+) ions, leading to increased catalytic activity for the H(2)O(2)-mediated oxidation of AUR. The fluorescence intensity (excitation/emission maxima: ca. 540/584 nm) of the oxidized AUR product is proportional to the concentration of Pb(2+) ions over the range 0.1-100 nM, with a linear correlation (R(2) = 0.99). The 40T30695-Au NP/AUR probe is highly selective toward Pb(2+) ions (by at least 200-fold over other tested metal ions). The 40T30695-Au NPs/AUR probe provided limits of detection (LOD, at a signal-to-noise ratio 3) for Pb(2+) ions of 0.05 and 0.1 nM, in Tris-acetate solution (5 mM, pH 8.0) without and with salt (150 mM NaCl, 5 mM KCl, 1 mM MgCl(2), and 1 mM CaCl(2)), respectively. Without conducting tedious sample pretreatment, the approach allows detection of Pb(2+) ions in blood samples, showing the potential of the 40T30695-Au NPs/AUR assay for on-site and real-time detection of Pb(2+) ions in biological samples.

Selective and sensitive ratiometric detection of Hg2+ in 100% aqueous solution with triazole-based dansyl probe

An amino acid-based fluorescent sensor (3) bearing a triazole group was synthesized by solid phase synthesis using click chemistry. 3 showed highly sensitive ratiometric response to Hg2+ in 100% aqueous solution. The dissociation constant for Hg2+ in aqueous solution was calculated to be 672 nM. 3 exhibited selective response to Hg2+ among 13 tested metal ions and the sensitive detection of Hg2+ by 3 was not interfered by other heavy metal ions, Group I and II metal ions. 1H NMR analysis revealed that two sulfonamide and triazole groups of 3 played a critical role in the interactions with Hg2+. 3 penetrated live cells and detected intracellular Hg2+. 3 allowed selective and sensitive ratiometric detection of Hg2+ in live cells as well as in 100% aqueous solution.

Purification and characterization of an acid-stable and organic solvent-tolerant xylanase from Aspergillus awamori VTCC-F312

An acid-stable and organic solvent-tolerant extracellular xylanase was isolated and purified from Aspergillus awamori VTCC-F312 and its properties were investigated. The xylanase was purified by Sephadex G-100 gel filtration chromatography and DEAE-Sephadex A-50 ion exchange chromatography to homogeneity. The enzyme had a molecular mass of 32 kDa and a specific activity of 217 U/mg protein, with optimum temperature of 50-55 °C and optimum pH of 5. This enzyme was stable at up to 45 °C and no loss of enzyme activity was observed after incubation for 6 h at 40 °C. The xylanase was stable within the pH range of 4-8 with no loss of enzyme activity after incubation at 30 °C for 1-4 h, even the enzyme activity was found to increase by 60% after incubation at pH 4 for 4 h. The Km and Vmax values were 12.6 mg oat spelt xylan per ml and 1000 U/mg protein, respectively. Dithiothreitol, -mercaptoethanol, and EDTA were found to increase the xylanase activity by 19%, 46%, and 138%, respectively. Except for Fe 3+ , the presence of 5 mM tested metal ions increased the enzyme activity by 18-52%. The enzyme showed high resistance to organic solvents and retained 63-86% and 44-61% of its activity in the presence of tested organic solvents at 30% and 80% (v/v), respectively. Triton X-100 and Tween 80 activated the xylanase to 128% and 116% of its activity, whereas SDS at the concentration of 5% completely inhibited the enzyme. These results suggested that the xylanase from A. awamori VTCC-F312 could potentially be used as a feed additive for monogastric animals.

Heavy metal ion inhibition studies of human, sheep and fish α-carbonic anhydrases

Carbonic anhydrases (CAs, EC 4.2.1.1) were purified from sheep kidney (sCA IV), from the liver of the teleost fish Dicentrarchus labrax (dCA) and from human erythrocytes (hCA I and hCA II). The purification procedure consisted of a single step affinity chromatography on Sepharose 4B-tyrosine-sulfanilamide. The kinetic parameters of these enzymes were determined for their esterase activity with 4-nitrophenyl acetate as substrate. The following metal ions, Pb2+, Co2+, Hg2+, Cd2+, Zn2+, Se2+, Cu2+, Al3+ and Mn3+ showed inhibitory effects on these enzymes. The tested metal ions inhibited these CAs competitively in the low milimolar/submillimolar range. The susceptibility to various cations inhibitors differs significantly between these vertebrate α-CAs and is probably due to their binding to His64 or the histidine cluster.

Synthesis, crystal structure and complexation behaviour of a thiacalix[4]arene bearing 1,2,3-triazole groups

The structure and complexation behaviour of 1,3-alternate-1,2,3-triazole based on thiacalix[4]arene,1,3-alternate-1 and 2 have been determined by means of X-ray analysis, fluorescence and 1H NMR spectroscopy. The X-ray results suggested that the nitrogen atom N3 on triazole ring can act as hydrogen bond acceptors in the self-assembly of a supramolecular structure. The fluorescence spectra changes indicated that the thiacalix[4]arene bearing 1,2,3-triazole groups were highly selective for Ag+ in comparison with other tested metal ions by enhancement of the monomer emission of pyrene. The 1H NMR results suggested that Ag+ can be strongly bonded by the triazole groups with the cooperation of the ionophoric cavity formed by the two inverted benzene rings and the sulfur atoms of the thiacalix[4]arene.

Highly sensitive and selective turn-on fluorescent chemosensor for Hg 2+ in pure water based on a rhodamine containing water-soluble copolymer

A novel easily available turn-on fluorescent polymeric chemosensor poly(VP-co-GMA-g-RhBH) based on water-soluble copolymer with pendant rhodamine B moiety was synthesized, which showed highly selective and sensitive recognition toward Hg 2+ in pure water over a wide range of tested metal ions with remarkably enhanced fluorescent intensities and also clear color changes from colorless to pink. In addition, the response of poly(VP-co-GMA-g-RhBH) to Hg 2+ is very quick without any time delay. The combination of water solubility and positive fluorescence response as well as color change is hence particularly promising for the practical utility of this sensor.

Heavy metal ions extraction from aqueous media using nanoporous silica

Nanoporous silica (NP) was synthesized and modified with thiol moiety [NPSi-SH]. Thermal gravimetric analysis (TGA) of [NPSi-SH] proved its high thermal stability in the temperature range of 25–600 °C. Structural identification of surface modification of [NPSi-SH] was also confirmed on the basis of surface coverage value from the study of thermal desorption method and FT-IR as well as electron impact-mass spectrometry (EI-MS) by the direct insertion probe. A study was performed to explore the metal adsorption, chelating and selectivity properties of [NPSi-SH] toward a series of di- and tri-valent toxic and nontoxic metal ions via determination of the metal capacity and distribution coefficient values. The incorporated selectivity characters of [NPSi-SH] were studied based on determination of the distribution coefficient and separation factor and the results have strongly referred to high affinity toward binding and up-take of anionic and cationic Hg(II) species in all the studied pH range (1.0–7.0). Also, The proposed mechanisms of adsorption of Hg(II) were suggested at different pH. The selective removal and extraction of Hg(II), via micro-column packed with [NPSi-SH], versus other toxic and nontoxic metal ions from drinking tap water samples were also explored. Excellent percentage extraction values of Hg(II) were characterized as 98.1 ± 4.0%, 98.0 ± 4.0% and 97.7 ± 3.0% from water samples buffered to pH 1.0, 2.0 and 7.0 respectively. The other tested metal ions were found to exhibit percentage extraction values of 94.0 ± 5.0% for Cd(II), 93.6 ± 4.0% for Cu(II) and 90.5 ± 5.0% for Zn(II) from pH 7.0 water samples. Different important analytical factors were applied to compare and show superiority of synthesized [NPSi-SH] phase with other previously reported silica gel phases-loaded-thiol [Si-SH].

A Highly Selective Colorimetric Chemosensor for Mn2+ Based on Bis(N-salicylidene)ethylenediamine in Pure Aqueous Solution

Abstract A novel easily available chemosensor 1 based on bis(N-salicylidene)ethylenediamine was reported, which exhibits highly selective and sensitive recognition toward Mn2+ in pure aqueous solution over a wide range of tested metal ions with a clear naked eye color change from colorless to red. This represents the first reported colorimetric chemosensor capable of detecting Mn2+ in aqueous solution.

Separation and sweeping of metal ions with EDTA in CZE‐ESI‐MS

Ethylenediaminetetraacetic acid (EDTA) in the background electrolyte (BGE) of capillary zone electrophoresis coupled to an electrospray ionization mass spectrometer is presented as an approach for the determination of metal ions. Significant signals for the metal-ligand complexes were observed even when EDTA was continually eluted from the capillary during the entire electrophoretic run. The signal-to-noise ratio was improved by the addition of ammonia to the sheath liquid and by using an acquisition m/z range above the m/z of EDTA. The LODs for the test metal ions (i.e. calcium(II), manganese(II), and zinc(II)) with conventional injection were around 1-2 mg/L with corrected peak areas that are linear from 8 to 100 mg/L. The presence of EDTA in the BGE was critical not only for the separation but also for sweeping via complexation as an on-line sample concentration technique. The peak height of the test metal ions was improved at least tenfold with sweeping via EDTA complexation and yielded LODs in the μg/L range.

A highly selective chemosensor for Cu2+ and Al3+ in two different ways based on Salicylaldehyde Schiff

Abstract A novel, easily available colorimetric and fluorescent double-sensor 1 based on Salicylaldehyde bis-Schiff has been investigated in this work. The sensor exhibits highly selective and sensitive recognition toward Cu2+ in aqueous solution via a naked eye colour change from colourless to yellow and toward Al3+ via a significant fluorescent enhancement in ethanol over a wide range of tested metal ions. This represents the first reported Salicylaldehyde Schiff-based sensor capable of detecting both Cu2+ and Al3+ using two different modes.

A naphthyridine based macrocyclic “switching on” fluorescent receptor for cadmium

A new macrocyclic receptor 1 having [1,8]-naphthyridine fluorophore is designed and synthesized for selective fluorescence sensing of Cd 2+. Receptor 1 selectively responds to Cd 2+ over other tested metal ions via a large enhancement of emission intensity due to the cation-induced CHEF (chelation enhanced fluorescence) effect. Receptor 1 although exhibits some affinity towards Zn 2+, it selectively binds Cd 2+ over Zn 2+. Binding and selectivity were examined by 1H-NMR, fluorescence, UV–vis, mass and IR-spectroscopic techniques.