Presence Of Various Metal Ions Research Articles

Purification and characterization of a cold-adapted pullulanase from a psychrophilic bacterial isolate.

There is a considerable potential of cold-active biocatalysts for versatile industrial applications. A psychrophilic bacterial strain, Shewanella arctica 40-3, has been isolated from arctic sea ice and was shown to exhibit pullulan-degrading activity. Purification of a monomeric, 150-kDa pullulanase was achieved using a five-step purification approach. The native enzyme was purified 50.0-fold to a final specific activity of 3.0 U/mg. The enzyme was active at a broad range of temperature (10-50 °C) and pH (5-9). Optimal activity was determined at 45 °C and pH 7. The presence of various metal ions is tolerated by the pullulanase, while detergents resulted in decreased activity. Complete conversion of pullulan to maltotriose as the sole product and N-terminal amino acid sequence indicated that the enzyme is a type-I pullulanase and belongs to rarely characterized pullulan-degrading enzymes from psychrophiles.

ICT based ratiometric fluorescent pH sensing using quinoline hydrazones

Two new quinoline hydrazones were synthesized, characterized and investigated as reversible ratiometric fluorescence pH sensors in the acidic pH region. The sensors were designed by the formation of simple donor–acceptor couple of quinoline aldehyde and phenyl hydrazine where protonation of quinoline-N triggered the pH sensing. No significant interference on emission behavior was observed in the presence of various metal ions. The sensors were used to visualize HeLa cells both at acidic and neutral pH with different emission. The MTT assay revealed negligible toxicity for both the hydrazones. The spectral properties, especially the large Stokes shift and the geometry of the molecules at the ground and excited states had been rationalized through DFT and TDDFT studies.

Hydrazone based luminescent receptors for fluorescent sensing of Cu2+: Structure and spectroscopy

Two new luminescent hydrazones, HL1 and HL2 were investigated for selective and sensitive fluorescent recognition of Cu2+ in aqueous medium (CH3CN/H2O (1:4, v/v) solvent system) with a 1:1 binding stoichiometry. The emission peak of HL (λem=405nm), undergoes significant quenching upon complexation with Cu2+. The quantum yields for the receptors and in situ formed Cu2+ complexes were determined. The absorption ratiometric analysis was carried out in presence of various metal ions to confirm the selectivity of the receptors towards Cu2+. They were able to detect Cu2+ with a ~0.9µM detection limit as indicated by fluorimetric measurements. The molecular structures of the receptors were determined by single crystal X-ray diffraction analysis.

Fluorescent Au(I)@Ag₂/Ag₃ giant cluster for selective sensing of mercury(II) ion.

Highly stable Au(I)(core)-Ag(0)(shell) particles have been synthesized in aqueous solution via a green chemistry pathway utilising sunlight irradiation. The shell of the particles is composed of fluorescent Ag2 and Ag3 clusters which make the large core-shell particles highly fluorescent. The Au(I) core of the particles offers long-term stability to the silver clusters, which are otherwise unstable in solution at room temperature, by the transfer of electron density from the shell. Successive additions of Hg(II) ions to the fluorescent solution cause efficient and selective quenching of the fluorescence with gradual red shifting of the emission peak. The metallophilic 5d(10)(Hg(2+))-4d(10)(Ag(δ+)) interaction as well as Hg(II) stimulated aggregation have been ascribed to causing the fluorescence quenching and red shift. The fluorescent Au(I)(core)-Ag(0)(shell) particles are a highly selective and sensitive sensing platform for the detection of Hg(II) down to 6 nM in the presence of various metal ions. The detection limit is far below the permissible level as determined by the EPA. Interferences due to Cu(II) and Fe(III) have been eliminated using Na2-EDTA and NH4HF2, respectively. The fluorescent particles are successfully transferred to various solvent systems making Hg(II) determination also possible in non-aqueous media. Finally, the temperature dependent fluorescence change with and without Hg(II) provides information about the metallophilic interaction.

Biochemical properties of a new cold-active mono- and diacylglycerol lipase from marine member Janibacter sp. strain HTCC2649.

Mono- and di-acylglycerol lipase has been applied to industrial usage in oil modification for its special substrate selectivity. Until now, the reported mono- and di-acylglycerol lipases from microorganism are limited, and there is no report on the mono- and di-acylglycerol lipase from bacteria. A predicted lipase (named MAJ1) from marine Janibacter sp. strain HTCC2649 was purified and biochemical characterized. MAJ1 was clustered in the family I.7 of esterase/lipase. The optimum activity of the purified MAJ1 occurred at pH 7.0 and 30 °C. The enzyme retained 50% of the optimum activity at 5 °C, indicating that MAJ1 is a cold-active lipase. The enzyme activity was stable in the presence of various metal ions, and inhibited in EDTA. MAJ1 was resistant to detergents. MAJ1 preferentially hydrolyzed mono- and di-acylglycerols, but did not show activity to triacylglycerols of camellia oil substrates. Further, MAJ1 is low homologous to that of the reported fungal diacylglycerol lipases, including Malassezia globosa lipase 1 (SMG1), Penicillium camembertii lipase U-150 (PCL), and Aspergillus oryzae lipase (AOL). Thus, we identified a novel cold-active bacterial lipase with a sn-1/3 preference towards mono- and di-acylglycerides for the first time. Moreover, it has the potential, in oil modification, for special substrate selectivity.

Novel rhodamine derivate as high selective detection lead sensor

A novel rhodamine based sensor 1 has been synthesized and characterized by NMR, FT-IR and mass. The binding properties of sensor 1 were investigated in the presence of various metal ions by UV–Vis spectroscopy and fluorescence spectroscopy. Sensor 1 showed colorimetric and high emission intensity enhancement in the presence of Pb2+ in chloroform-THF (7:3).

A theoretical study on the catalytic mechanism of the retaining α-1,2-mannosyltransferase Kre2p/Mnt1p: the impact of different metal ions on catalysis.

Glycosyltransferases are sugar-processing enzymes that require a specific metal ion cofactor for catalysis. In the presence of other ions the catalysis is often impaired. Here, for the first time, the enzymatic catalysis in the presence of various metal ions was modeled for a glycosyltransferase using a large enzymatic model. The catalytic mechanism of α-1,2-mannosyltransferase Kre2p/Mnt1p in the presence of Mn(2+) and other ions (Mg(2+), Zn(2+) and Ca(2+)) was modeled at the two hybrid DFT-QM/MM (M06-2X/OPLS2005 and B3LYP/OPLS2005) levels. Kinetic and structural parameters of transition states and intermediates, as well as kinetic isotope effects, were predicted and compared with available experimental and theoretical data. The catalysis in the presence of the metal ions is predicted as a stepwise SNi-like nucleophilic substitution reaction (DNint*AN(‡)DhAxh) via oxocarbenium ion intermediates. In the rate-determining step the leaving phosphate group of the donor substrate plays a role of the base catalyst. The predicted increased enzymatic reactivity (kcat: Zn(2+) ≈ Mg(2+) < Mn(2+) < Ca(2+)) correlated with the metal ion ability to polarize the Kre2p environment (Mg(2+) > Zn(2+) > Mn(2+) > Ca(2+)). The formation of the retained anomeric configuration in the product is controlled by a strict geometry of the active site of Kre2p. The 6-OH group of the attacking acceptor substrate may assist in protection of the anomeric carbon against unwanted hydrolysis by a through-space interaction with the electron deficient C1[double bond, length as m-dash]O5(+) moiety of the oxocarbenium-ion-like transition state.

Carbon dots production via pyrolysis of sago waste as potential probe for metal ions sensing

This work reports the synthesis of carbon dots (C-dots) from sago industrial waste using thermal pyrolysis approach. The pyrolysis condition was found to govern the carbonisation conversion of bulk sago waste into carbon rich residue that can be further isolated to obtain carbon dots. In order to obtain the best yield of the carbon dots, optimization of the thermal pyrolysis conditions have been performed which consisted of varying temperature of carbonisation at a constant heating duration. The C-dots can be dispersed in aqueous media and portrayed a significant fluorescent property that can be observed by naked eye under a UV light source. The optimum temperature of carbonisation was determined at 400°C in which the strongest fluorescence emission was record at 390nm with the optimum excitation wavelength of 315nm. The fluorescence of the C-dots was found to be significantly quenched in the presence of various metal ions. Thus, the C-dots can be adopted as a potential optical probe for sensing of metal ions in aqueous media. An analytical characterization has been performed in this study over a series of commonly available metal ions and the sensing characteristics were evaluated using the standard Stern–Volmer quenching model. This study has successfully demonstrated an innovative approach of converting agricultural waste into high value optical sensing receptors for metal ions detection.

Expression and chaperone-assisted refolding of a new cold-active lipase from Psychrobacter cryohalolentis K5T

We describe cloning and expression of genes coding for lipase Lip2Pc and lipase-specific foldase LifPc from a psychrotrophic microorganism Psychrobacter cryohalolentis K5T isolated from a Siberian cryopeg (the lense of overcooled brine within permafrost). Upon expression in Escherichiacoli Lip2Pc accumulated in inclusion bodies while chaperone was synthesized in a soluble form. An efficient protocol for solubilization and subsequent refolding of the recombinant lipase in the presence of the truncated chaperone was developed. Using this procedure Lip2Pc with specific activity of 6900U/mg was obtained. Contrary to published data on other lipase-chaperone complexes, refolded Lip2Pc was mostly recovered from the complex with chaperone by metal-affinity chromatography. Recombinant Lip2Pc displayed maximum lipolytic activity at 25°C and pH 8.0 with p-nitrophenyl palmitate (C16) as a substrate. Activity assays conducted at different temperatures revealed that the recombinant Lip2Pc is a cold-adapted lipase with ability to utilize substrates with long (C10–C16) hydrocarbon chains in the temperature range from +5 to +65°C. It demonstrated relatively high stability at temperatures above 60°C and in the presence of various metal ions or organic solvents (ethanol, methanol, etc.). Non-ionic detergents, such as Triton X-100 and Tween 20 decreased Lip2Pc activity and SDS completely inhibited it.

An Application of Wastewater Treatment in a Cold Environment and Stable Lipase Production of Antarctic Basidiomycetous Yeast Mrakia blollopis

Milk fat curdle in sewage is one of the refractory materials for active sludge treatment under low temperature conditions. For the purpose of solving this problem by using a bio-remediation agent, we screened Antarctic yeasts and isolated SK-4 strain from algal mat of sediments of Naga-ike, a lake in Skarvsnes, East Antarctica. The yeast strain showed high nucleotide sequence homologies (>99.6%) to Mrakia blollopis CBS8921T in ITS and D1/D2 sequences and had two unique characteristics when applied on an active sludge; i.e., it showed a potential to use various carbon sources and to grow under vitamin-free conditions. Indeed, it showed a biochemical oxygen demand (BOD) removal rate that was 1.25-fold higher than that of the control. We considered that the improved BOD removal rate by applying SK-4 strain was based on its lipase activity and characteristics. Finally, we purified the lipase from SK-4 and found that the enzyme was quite stable under wide ranges of temperatures and pH, even in the presence of various metal ions and organic solvents. SK-4, therefore, is a promising bio-remediation agent for cleaning up unwanted milk fat curdles from dairy milk wastewater under low temperature conditions.

Electrochemical Investigation of Anthraquinone‐Based Chemodosimeter for Cu2+ Metal Ion

The electrochemical properties of an anthraquinone‐containing Cu2+‐promoted desulfurization chemodosimeter (AQCD) in the presence of various metal ions were investigated by voltammetry. AQCD showed voltammetric changes toward divalent metal ions (M2+), which are similar to those of anthraquinone (AQ) and 1‐aminoanthraquinone (AQNH2) with the metal ions except Cu2+. This can be explained on the electrostatic interaction (AQCD‐M2+) and chemodosimetric reaction (AQCD‐Cu2+).

Highly sensitive detection of Hg2+ in aqueous solution using cationic polythiophene derivatives

Two novel water-soluble conjugated polymers poly{3-[1-(2-trimethylammoniumacetyl)piperidine-4-methylene]thiophene-2,5-diyl chloride} (PTAPT-Cl) and poly{3-[1-(2-trimethylammoniumbutyryl)piperidine-4-methylene] thiophene-2,5-diyl chloride} (PTBPT-Cl) have been synthesized via chemical oxidative polymerization and applied as a colorimetric and fluorometric probe for the detection of metal ions. Moreover, the fluorescence detection of metal ions using previously synthesized poly[N,N,N-trimethyl-4-(thiophen-3-ylmethylene)cyclohexanaminium chloride] (PTCA-Cl) and poly[3-(1,1′-dimethyl-4-piperidinemethylene)thiophene-2,5-diyl chloride] (PDPMT-Cl) was also investigated and discussed. All four conjugated polymers exhibited high sensitivity and selectivity to Hg2+ with a fluorescence “turn-off” mode at pH 3 in aqueous solutions. The best detection limit was as low as 10−9 M without interference from other common metal ions. Consequently, the distinctive quenching of the emission bands in the presence of various metal ions can lead to qualitative and quantitative Hg2+ detection in aqueous solution by a new approach using cationic polythiophene derivatives.

Logical regulation of the enzyme-like activity of gold nanoparticles by using heavy metal ions

In this study we employed self-deposition and competitive or synergistic interactions between metal ions and gold nanoparticles (Au NPs) to develop OR, AND, INHIBIT, and XOR logic gates through regulation of the enzyme-like activity of Au NPs. In the presence of various metal ions (Ag(+), Bi(3+), Pb(2+), Pt(4+), and Hg(2+)), we found that Au NPs (13 nm) exhibited peroxidase-, oxidase-, or catalase-like activity. After Ag(+), Bi(3+), or Pb(2+) ions had been deposited on the Au NPs, the particles displayed strong peroxidase-like activity; on the other hand, they exhibited strong oxidase- and catalase-like activities after reactions with Ag(+)/Hg(2+) and Hg(2+)/Bi(3+) ions, respectively. The catalytic activities of these Au NPs arose mainly from the various oxidation states of the surface metal atoms/ions. Taking advantage of this behavior, we constructed multiplex logic operations-OR, AND, INHIBIT, and XOR logic gates-through regulation of the enzyme-like activity after the introduction of metal ions into the Au NP solution. When we deposited Hg(2+) and/or Bi(3+) ions onto the Au NPs, the catalase-like activities of the Au NPs were strongly enhanced (>100-fold). Therefore, we could construct an OR logic gate by using Hg(2+)/Bi(3+) as inputs and the catalase-like activity of the Au NPs as the output. Likewise, we constructed an AND logic gate by using Pt(4+) and Hg(2+) as inputs and the oxidase-like activity of the Au NPs as the output; the co-deposition of Pt and Hg atoms/ions on the Au NPs was responsible for this oxidase-like activity. Competition between Pb(2+) and Hg(2+) ions for the Au NPs allowed us to develop an INHIBIT logic gate-using Pb(2+) and Hg(2+) as inputs and the peroxidase-like activity of the Au NPs as the output. Finally, regulation of the peroxidase-like activity of the Au NPs through the two inputs Ag(+) and Bi(3+) enabled us to construct an XOR logic gate.

Presence of Catechol Metabolizing Enzymes in Virgibacillus Salarius

Hydrocarbon contamination of marine ecosystems has been a major environmental concern. Hydrocarbon metabolizing capacity of four halotolerant bacteria (Bacillus atrophaeus, Halomonas shengliensis, Halomonas koreensis, and Virgibacillus sala- rius) isolated from saline soil of Khambhat, India was investigated. Presence of catechol metabolizing enzymes (catechol 2,3 dio- xygenase, chlorocatechol 1,2 dioxygenase, and protocatechuate 3,4 dioxygenase) was checked in V. salarius, as only this among all the test organisms could grow on the hydrocarbon substrates used, and compared with Pseudomonas oleovorans. Effect of salinity of the growth medium on activity of catechol metabolizing enzymes was also studied. Catechol 2,3 dioxygenase activity in both the organisms was more susceptible to increase in salinity of the growth medium than chlorocatechol 1,2-dioxygenase activity. To the best of our awareness, this is the first report of catechol metabolism in V. salarius. V. salarius was found to be capable of weak biofilm formation. As V. salarius is capable of growing at high salt concentration, alkaline pH, hydrocarbon degradation, and also of growth in presence of various metal ions, it can be an attractive candidate for bioremediation of marine oil spills. Organisms like V. salarius can also serve as a model for multiple stress tolerance in prokaryotes.

Bio-hydrogen production and the F0F1-ATPase activity of Rhodobacter sphaeroides: Effects of various heavy metal ions

Rhodobacter sphaeroides MDC 6521 isolated from Arzni mineral springs in Armenia is able to produce bio-hydrogen (H2) in anaerobic conditions upon illumination in the presence of various metal ions. The significant aspect in regulation of H2 production by these bacteria and its energetics is the requirement for F0F1-ATPase, the main membrane enzyme responsible for generation of proton motive force under anaerobic conditions. In order to determine the mediatory role of F0F1 in H2 production, the effects of various metal ions (Mn2+, Mg2+, Fe2+, Ni2+, and Mo6+) on N,N′-dicyclohexylcarbodiimide inhibited ATPase activity of R. sphaeroides membrane vesicles were investigated. These ions in appropriate concentrations considerably enhanced H2 production, which was not observed in the absence of Fe2+, indicate the requirement for Fe2+. The R. sphaeroides membrane vesicles demonstrated significant ATPase activity. In the absence of Fe2+ inhibition (∼80%) of ATPase activity was observed, which was increased by addition of metal ions. A higher ATPase activity was detected in the presence of Fe2+ (80 μM) and Mo6+ (16 μM). These results indicate a relationship between the F0F1-ATPase activity and H2 production that might be a significant pathway to provide novel evidence of a requirement for F0F1-ATPase in H2 production by R. sphaeroides.

Chemometric Analysis of Voltammetric Data on Metal Ion Binding by Selenocystine

The behavior of selenocystine (SeCyst) alone or in the presence of various metal ions (Bi(3+), Cd(2+), Co(2+), Cu(2+), Cr(3+), Ni(2+), Pb(2+), and Zn(2+)) was studied using differential pulse voltammetry (DPV) over a wide pH range. Voltammetric data matrices were analyzed using chemometric tools recently developed for nonlinear data: pHfit and Gaussian Peak Adjustment (GPA). Under the experimental conditions tested, no evidence was found for the formation of metal complexes with Bi(3+), Cu(2+), Cr(3+), and Pb(2+). In contrast, SeCyst formed electroinactive complexes with Co(2+) and Ni(2+) and kinetically inert but electroactive complexes with Cd(2+) and Zn(2+). Titrations with Cd(2+), Co(2+), Ni(2+), and Zn(2+) produced data that were reasonably consistent with the formation of stable 1:1 M(SeCyst) complexes.

INFLUENCE OF SELECTED METAL IONS ON STABILITY OF HYDROGEN PEROXIDE IN PRESENCE OF EDTA

UDK 546.215:546.4/.8&#x0D; Stability of hydrogen peroxide in time was investigated in the presence of various metal ions and a complexing agent ethylenediaminetetraacetic acid (EDTA). Metal ions: Fe(III), Mn(II), Co(II), Cu(II), Ni(II), Zn(II) and Pb(II) were applied at different concentrations with a chelator in a concentration of 1 ·10-5 mol/dm3, and the solutions were kept at 4oC between the measurements. Obtained data indicate the existence of pronounced catalytic effect for Fe(III), Mn(II), Co(II) ions on stability of hydrogen peroxide. Cu(II) ions showed significant catalytic influence only when applied at high concentration. Ni(II), Pb(II) and Zn(II) did not show significant catalytic effect on the decay of hydrogen peroxide at applied concentrations.

Thermostable Bacterial Endoglucanases Mined from Swiss-Prot Database

As one critical enzyme in deconstructing complicated cellulose matrix, endoglucanase (EG) is needed to exhibit high activity and thermostability under severe industrial conditions. Driven by this purpose, EGtf1 (Q08166) and EGtf2 (Q7X2N2), with relatively high specific activities, were selected out of 43 putative EG genes from SWISS-PROT database. These distinguished EGs were successfully overexpressed in Escherichia coli and purified by one-step affinity chromatography. The maximal activity was shown at approximate pH 5.0 and 50 °C. It is worth noting that EGtf1 and EGtf2 displayed outstanding thermostability with a half-life of up to 1,386 h at 50 °C, which is almost 100-fold higher than other reported EGs. Furthermore, the presence of various metal ions (1 mM) or organic solvents (50%, v/v) did not cause significant effect on the activities of EGtf1 and EGtf2 and even showed 2.1- and 2.7-fold enhancement in the case of dodecanol. All these features, especially the excellent thermostability of EGtf1 and EGtf2, enable them to become a good candidate for further protein engineering to realize the ultimate practical application in biomass industry.

A Fluorescent Chemosensor Based on 7-Nitrobenz-2-oxa-1,3-diazole (NBD) for the Selective Detection of Hg(II)

In this study, we prepared 2 by treating NBD chloride (4chloro-7-nitrobenz-2-oxa-1,3-diazole) with 1 at room temperature in the presence of potassium carbonate in tetrahydrofuran as shown in Scheme 1 and investigated the absorption and emission behaviors of 2 in the presence of various metal ions. The UV-vis absorption behaviors of 2 (100 μM) in 50% acetonitrile in water in the presence of various metal ions (100 equiv) are shown in Figure 1. In the absence of metal ions, 2 shows an intense absorption at 484 nm, which is assignable to the intramolecular charge transfer (ICT) transition from the N atom of the 3,9-dithia-6-azaundecane moiety to the nitro group of the NBD moiety of 2. 9 No significant change in the absorption of 2 was observed upon the

Transparent, Luminescent, Antibacterial and Patternable Film Forming Composites of Graphene Oxide/Reduced Graphene Oxide

Multifunctional graphene oxide/reduced graphene oxide (GO/RGO) composites were prepared through electrostatic interaction using biocompatible ingredients. Different functionalities were added to GO/RGO by anchoring materials such as native lactoferrin (NLf), NLf protected Au clusters (designated as Au@NLf), chitosan (Ch) and combinations thereof. Anchoring of Ch and NLf enhances the antibacterial property of RGO/GO. The addition of Ch to RGO/GO not only helped in forming stable dispersions but also helped in fabricating large (cm(2)) area films through a simple solvent evaporation technique. Functionalities such as photoluminescence were added to Ch-RGO/GO composites by anchoring Au@NLf on it. The composites thus formed showed stable luminescence in presence of various metal ions in the solid state. The composite showed reasonable stability against pH and temperature variations as well. The as-prepared films were transparent and the transparency could be modulated by controlling the concentration of RGO/GO in the composite. The antibacterial property and ability to form stable thin films may provide an opportunity to use such composites for medical and environmental remediation applications as well. Erasable patterns were fabricated on the film by stamping required patterns under compressive pressure. Luminescent patterns can be inscribed on the film and can be erased by simply wetting it. Such films with erasable information may be useful for security applications.