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Hg2+
Terms modified by Hg2+ Selected AbstractsSimultaneous Determination of Cadmium, Lead, Copper and Mercury Ions Using Organofunctionalized SBA-15 Nanostructured Silica Modified Graphite,Polyurethane Composite ElectrodeELECTROANALYSIS, Issue 1 2010Ivana Cesarino Abstract A new sensor has been developed for the simultaneous detection of cadmium, lead, copper and mercury, using differential pulse and square wave anodic stripping voltammetry (DPASV and SWASV) at a graphite,polyurethane composite electrode with SBA-15 silica organofunctionalized with 2-benzothiazolethiol as bulk modifier. The heavy metal ions were preconcentrated on the surface of the modified electrode at ,1.1,V vs. SCE where they complex with 2-benzothiazolethiol and are reduced to the metals, and are then reoxidized. Optimum SWASV conditions lead to nanomolar detection limits and simultaneous determination of Cd2+, Pb2+, Cu2+ and Hg2+ in natural waters was achieved. [source] Silver(I)-Selective PVC Membrane Potentiometric Sensor Based on a Recently Synthesized Calix[4]areneELECTROANALYSIS, Issue 10 2006Ayça Demirel Abstract A new PVC membrane potentiometric sensor for Ag(I) ion based on a recently synthesized calix[4]arene compound of 5,11,17,23-tetra- tert -butyl-25,27-dihydroxy-calix[4]arene-thiacrown-4 is developed. The electrode exhibits a Nernstian response for Ag(I) ions over a wide concentration range (1.0×10,2,1.0×10,6 M) with a slope of 53.8±1.6,mV per decade. It has a relatively fast response time (5,10,s) and can be used for at least 2 months without any considerable divergence in potentials. The proposed electrode shows high selectivity towards Ag+ ions over Pb2+, Cd2+, Co2+, Zn2+, Cu2+, Ni2+, Sr2+, Mg2+, Ca2+, Li+, K+, Na+, NH4+ ions and can be used in a pH range of 2,6. Only interference of Hg2+ is found. It is successfully used as an indicator electrode in potentiometric titration of a mixture of chloride, bromide and iodide ions. [source] A Bis-Oxime Derivative of Diaza-18-Crown-6 as an Ionophore for Silver IonELECTROANALYSIS, Issue 11 2005Michael Abstract A new pendant-arm derivative of diaza-18-crown-6, containing two oxime donor groups, has been synthesized and incorporated into a polyvinyl chloride (PVC) membrane ion-selective electrode. The electrode shows selectivity for Ag+ ion, with a near Nernstian response. Pb2+, Cu2+, Hg2+, and Tl+ are major interfering ions, with Cd2+ having minor interference. The electrode shows no potentiometric response for the ions Mg2+, Al3+, K+, Ca2+, Ni2+, Fe3+, and La3+, and is responsive to H+ at pH<6. [source] Different Morphological Organic,Inorganic Hybrid Nanomaterials as Fluorescent Chemosensors and Adsorbents for CuII IonsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 10 2008Soo Jin Lee Abstract Functionalized silica nanotubes (FSNT), functionalized mesoporous silica (FMS), and functionalized silica nanoparticles (FSNP-15) with an immobilized phenanthroline moiety as a fluorescent receptor were fabricated by a sol,gel reaction, and their binding abilities with metal ions were evaluated by fluorophotometry in water/acetonitrile (8:2, v/v) at pH 7. They selectively recognized Cu2+ ions among other metal cations such as Co2+, Cd2+, Hg2+, Ni2+, Fe3+, Ag+, Pb2+, and Zn2+, because the Cu2+ ion selectively binds to the nitrogen atoms of the phenanthroline moiety. Among the three silica nanomaterials with the immobilized receptor 1, the sensitivity of FSNT for Cu2+ ions is better than those of FMS and FSNP-15, indicating that the adsorption capacity for metal ions is dependent on the shape and surface area of the supporting nanomaterials. FSNT (10 mg) adsorb 75,% of the Cu2+ ions (2.0,×,10,4 mM) while FSNP-15 (10 mg) adsorb only 36,%. The detection limit of FSNT for Cu2+ ions was ca. 3.0,×,10,8M. FSNT and FMS can be easily renewed by treatment with a solution of HCl and tetrabutylammonium hydroxide. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Highly Organosoluble Metal-Free Phthalocyanines and Metallophthalocyanines: Synthesis and CharacterizationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2007Ahmet Bilgin Abstract The syntheses and characterization of metal-free and metal-containing (Zn and Ni) derivatives of a symmetrically octa-substituted phthalocyanine derived from 4,5:12,13-bis(4,- tert -butylbenzo)-8,9-(4,,5,-dicyanobenzo)-6,11-ditosyl-6,11-diaza-2,15-dithiacyclohexadeca-4,8,12-triene and CuPc from 4,5:12,13-bis(4,- tert -butylbenzo)-8,9-(4,,5,-dibromobenzo)-6,11-ditosyl-6,11-diaza-2,15-dithiacyclohexadeca-4,8,12-triene were carried out. Pentanuclear silver(I) and palladium(II) complexes have also been prepared from nickel(II) phthalocyaninate derivatives. The prepared phthalocyanines were semiconducting materials in the range of 10,5 to10,10 S,cm,1 in vacuo and under atmospheric pressure. The extraction abilities of NiPc and detosylated phthalocyanines were evaluated in chloroform/water by using several heavy-metal picrates such as Ag+, Cd2+, Cu2+, Hg2+, Pb2+, Pd2+, and Zn2+. The extraction affinities of NiPc and detosylated phthalocyanines for Ag+ were found to be the highest in solvent extraction experiments. The new compounds were characterized by using elemental analysis, UV/Vis, FTIR, NMR, MS spectroscopic data and DTA/TG. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Quantitative Removal of Mercury(II) from Water Through Bulk Liquid Membranes by Lipophilic PolyaminesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 19 2006Nicoletta Spreti Abstract Transport of mercury(II) and copper(II) ions through bulk liquid membranes has been studied, the former because of its toxicity and wide distribution in the environment, the latter for comparative purposes. The abilities of two carriers, the known N,N, -bis[2-(hexadecylamino)ethyl]- N,N, -bis(hydroxyethyl)ethylenediamine (bis-HE16ED) and the new N,N,-bis(p -octyloxybenzyl)-3,6-dioxaoctane-1,8-diamine (bis- pODODA), to complex and transport the selected metal ions are reported. Bis-HE16ED is a good carrier for Cu2+ ions, but the high stability of the carrier/Hg2+ ion complex in the membrane results in a lack of its transport. On the other hand, the new carrier displays a very high efficiency in Hg2+ ion transport, effecting quantitative transfer of the metal ion into the receiving phase within 24 h, despite its chelating region being only slightly different from that in bis-HE16ED. The ability of bis- pODODA to transport 100,% of Hg2+ efficiently in consecutive cycles is also reported. This result provides a basis for future development of a decontamination process based on a carrier-mediated transport system. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] A New Carrier for Selective Removal of Heavy Metal Ions from Aqueous Solutions through Bulk Liquid MembranesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 18 2004Nicoletta Spreti Abstract The carrier-mediated transport of heavy metal ions through bulk liquid membranes has been examined: toxic Hg2+, Cd2+ and Pb2+ ions were studied, along with Cu2+ ions for comparative purposes. The ability of a new carrier, 2,2,-bis(p -octyloxybenzyl)diethylenetriamine (bis- pODET), to complex and transport all the selected metal ions is reported. Differing affinities of the carrier for the different metal ions and the different experimental conditions required for their release into the receiving phase allowed the selective separation of equimolar binary mixtures. For Hg2+/Cd2+ and Hg2+/Pb2+ mixtures, two different separation methods were performed, while the inefficacy of the separation of Cd2+/Pb2+ and Hg2+/Cu2+ mixtures was for two different reasons: (i) the carrier is able to extract the metal ions with similar levels of ability, and (ii) the carrier metal ion complexes require the same acidity of the receiving phase to release the metal ions. The capability of the carrier to transport Hg2+ efficiently in consecutive cycles is also reported: over 90% of the metal ions were transferred into the receiving phase for three consecutive processes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Carrier-Mediated Transport of Toxic Heavy Metal Ions in Bulk Liquid MembranesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 6 2004Lucia Brinchi Abstract Transport through a dichloromethane liquid membrane has been studied to investigate the ability of 1,1,7,7-tetraethyl-4-tetradecyldiethylenetriamine (TE14DT), previously tested for the transport of copper, to act as a carrier for toxic heavy metal ions such as Cd2+, Pb2+ and Hg2+. The carrier displayed a remarkable capability to extract all the metal ions from the source to the organic phases but only cadmium was efficiently transported across the membrane. The experimental conditions optimised for the transport of copper are inadequate for lead and mercury. In fact, the inefficacy of their transport could be due, as regards lead, to the slow diffusion of the complex through the membrane, while mercury remained in the organic phase because of the high stability of the mercury-carrier complex. Selectivity tests using binary mixtures of the metal ions showed TE14DT's capability to transport copper or cadmium also in the presence of lead in the source phase. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Purification and characterization of the single-strand-specific and guanylic-acid-preferential deoxyribonuclease activity of the extracellular nuclease from Basidiobolus haptosporusFEBS JOURNAL, Issue 16 2000Neelam A. Desai An extracellular nuclease from Basidiobolus haptosporus (designated as nuclease Bh1) was purified to homogeneity by ammonium sulfate precipitation, heat treatment, negative adsorption on DEAE-cellulose, and chromatography on phenyl-Sepharose followed by FPLC on phenyl-Superose. The overall yield was 26%. The Mr of the purified enzyme, determined by gel filtration, was 41 000 whereas by SDS/PAGE (after deglycosylation) it was 30 000. It is a glycoprotein with a pI of 6.8. The optimum pH and temperature for DNA hydrolysis were 8.5 and 60 °C, respectively. Nuclease Bh1 is a metalloprotein but has no obligate requirement for metal ions to be active, nor is its activity stimulated in the presence of metal ions. The enzyme was inhibited by Zn2+, Ag2+, Hg2+, Fe3+ and Al3+, inorganic phosphate, pyrophosphate, dithiothreitol, 2-mercaptoethanol, NaCl and KCl. It was stable to high concentrations of organic solvents and urea but susceptible to low concentrations of SDS and guanidine hydrochloride. Nuclease Bh1 is a multifunctional enzyme and its substrate specificity is in the order of ssDNA , 3,AMP , RNA > dsDNA. Studies on its mode of action showed that it cleaved supercoiled pUC 18 DNA and phage M13 DNA, endonucleolytically, generating single base nicks. The enzyme hydrolyzed DNA with preferential liberation of 5,dGMP, suggesting it to be a guanylic acid preferential endoexonuclease. 5,dGMP, the end product of hydrolysis, was a competitive inhibitor of the enzyme. The absence of 5,dCMP as a hydrolytic product, coupled with the resistance of (dC)10 and deoxyribodinucleoside monophosphates having cytosine either at the 3, or the 5, end, indicates that C-linkages are resistant to cleavage by nuclease Bh1. [source] Phytase activity in Cryptococcus laurentii ABO 510FEMS YEAST RESEARCH, Issue 3 2007Jason Van Staden Abstract Ten Cryptococcus strains were screened for phytase activity, of which the Cryptococcus laurentii ABO 510 strain showed the highest level of activity. The cell wall-associated enzyme displayed temperature and pH optima of 62°C and 5.0, respectively. The enzyme was thermostable at 70°C, with a loss of 40% of its original activity after 3 h. The enzyme was active on a broad range of substrates, including ATP, d -glucose 6-phosphate, d -fructose 1,6-diphosphate and p -nitrophenyl phosphate (p -NPP), but its preferred substrate was phytic acid (Km of 21 ,M). The enzyme activity was completely inhibited by 0.5 mM inorganic phosphate or 5 mM phytic acid, and moderately inhibited in the presence of Hg2+, Zn2+, Cd2+ and Ca2+. These characteristics suggest that the Cry. laurentii ABO 510 phytase may be considered for application as an animal feed additive to assist in the hydrolysis of phytate complexes to improve the bioavailability of phosphorus in plant feedstuff. [source] Thermo-Switchable Charge Transport and Electrocatalysis Using Metal-Ion-Modified pNIPAM-Functionalized ElectrodesADVANCED FUNCTIONAL MATERIALS, Issue 15 2009Michael Riskin Abstract Metal ions (Ag+, Cu2+, Hg2+) are incorporated into an electropolymerized, poly(N -isopropyl acrylamide), pNIPAM, thermosensitive polymer associated with an electrode using the "breathing-in" method. The ion-functionalized pNIPAM matrices reveal ion-dependent gel-to-solid phase-transition temperatures (28,±,1,°C, 25,±,1,°C, 40,±,1,°C for the Ag+, Cu2+, and Hg2+ -modified pNIPAM, respectively). Furthermore, the ion-functionalized polymers exhibit quasi-reversible redox properties, and the ions are reduced to the respective Ag0, Cu0, and Hg0 nanocluster-modified polymers. The metal-nanocluster-functionalized pNIPAM matrices enhance the electron transfer (they exhibit lower electron-transfer resistances) in the compacted states. The electron-transfer resistances of the metal-nanocluster-modified pNIPAM can be cycled between low and high values by temperature-induced switching of the polymer between its contracted solid and expanded gel states, respectively. The enhanced electron-transfer properties of the metal nanocluster-functionalized polymer are attributed to the contacting of the metal nanoclusters in the contracted state of the polymers. This temperature-switchable electron transfer across a Ag0 -modified pNIPAM was implemented to design a thermo-switchable electrocatalytic process (the temperature-switchable electrocatalyzed reduction of H2O2 by Ag0 -pNIPAM). [source] H2xMnxSn3-xS6 (x,=,0.11,0.25): A Novel Reusable Sorbent for Highly Specific Mercury Capture Under Extreme pH ConditionsADVANCED FUNCTIONAL MATERIALS, Issue 7 2009Manolis J. Manos Abstract The H2xMnxSn3-xS6 (x,=,0.11,0.25) is a new solid acid with a layered hydrogen metal sulfide (LHMS). It derives from K2xMnxSn3,xS6 (x,=,0.5,0.95) (KMS-1) upon treating it with highly acidic solutions. We demonstrate that LHMS-1 has enormous affinity for the very soft metal ions such as Hg2+ and Ag+ which occurs via a rapid ion exchange process. The tremendous affinity of LHMS-1 for Hg2+ is reflected in very high distribution coefficient KdHg values (>106,mL g,1). The large affinity and selectivity of LHMS-1 for Hg2+ persists in a very wide pH range (from less than zero to nine) and even in the presence of highly concentrated HCl and HNO3 acids. LHMS-1 is significantly more selective for Hg2+ and Ag+ than for the less soft cations Pb2+ and Cd2+. The Hg2+ ions are immobilized in octahedral sites between the sulfide layers of the materials via Hg,S bonds as suggested by pair distribution function (PDF) analysis. LHMS-1 could decrease trace concentrations of Hg2+ (e.g. <100,ppb) to well below the acceptable limits for the drinking water in less than two min. Hg-laden LHMS-1 shows a remarkable hydrothermal stability and resistance in 6,M HCl solutions. LHMS-1 could be regenerated by treating Hg-loaded samples with 12,M HCl and re-used without loss of its initial exchange capacity. [source] Synthesis of a Fusion-Isomeric Cellobionoimidazole and Its Evaluation against the syn -Protonating Glycosidase Cel7AHELVETICA CHIMICA ACTA, Issue 12 2005Narinder Mohal The fusion-isomeric cellobinoimidazole 2, a potential inhibitor of the syn -protonating , -glycosidase Cel7A, was synthesised by Koenigs,Knorr glycosylation of the ,- D -arabinopyranoside 32, followed by selective hydrolysis. Glycosylation of 32 with acetobromoglucose 6 proceeded with poor diastereoselectivity, giving the desired 1,3-linked , - d- disaccharide 35 as minor product, besides the major 1,3-linked ,- d- disaccharide 36. Hg2+ -Promoted glycosylation of 32 led predominantly to the 1,2-ortho ester 33. Sequential removal of the silyl, acetyl, and allyl groups of 35 led to a 45,:,55 equilibrium mixture 2 and the manno -configured isomer 39. Similarly, deprotection of 36 gave a mixture of the maltonoimidazole 42 and the manno -configured isomer 43. According to a known protocol, the glycosyl acceptor 32 was synthesised in eleven steps and an overall yield of 8,13% from D -lyxose. The silylated arabinopyranosyl moiety of the ,- d- glucosides 13,19, 33, 34, and 36 adopts a 4C1 conformation, while the arabinopyranosyl moiety of the , - d- glucosides 17 and 35 exists as a 1,:,3,mixture of 4C1 and 1C4 conformers, as a result of the combined preferred axial orientation of bulky vicinal substituents and the anomeric effect. MM3* Modelling evidences a preferred 4C1 conformation of 35 and 36, and stronger steric interactions between the pyranosyl moieties of 35. The equilibrium mixture 2/39 proved a poor inhibitor of Cel7A with an IC50 value of ca. 4,mM. [source] Mercury Biosensors: Polydiacetylene,Liposome Microarrays for Selective and Sensitive Mercury(II) Detection (Adv. Mater.ADVANCED MATERIALS, Issue 36 200936/2009) Polydiacetylene (PDA) liposome microarrays have been developed for selective and sensitive mercury detection. The sensors, reported on p. 3674 by Jinsang Kim and co-workers, are designed to produce red fluorescence emission upon binding with Hg2+; when the single-stranded DNA aptamers on the microarray selectively wrap around the mercury ions, the resulting complexes repulse each other. The epoxy-based PDA liposome design is an excellent universal platform that can be readily extended to other sensor designs. [source] Polydiacetylene,Liposome Microarrays for Selective and Sensitive Mercury(II) DetectionADVANCED MATERIALS, Issue 36 2009Jiseok Lee Polydiacetylene (PDA) liposome microarrays are developed for selective and sensitive mercury (Hg2+) detection. The PDA mercury sensors are designed to produce red fluorescence emission upon binding with Hg2+, when the ssDNA aptamers on the PDA surface recognize and wrap around mercury ions and the resulting bulky T-Hg-T complexes repulse each other. [source] Optical Detection of Mercury(II) in Aqueous Solutions by Using Conjugated Polymers and Label-Free Oligonucleotides,ADVANCED MATERIALS, Issue 11 2007X. Liu A conjugated-polymer-based "mix-and-detect" optical sensor for mercury ions is fabricated by using a water-soluble poly[3-(3,- N,N,N -triethylamino-1,-propyloxy)-4-methyl-2,5-thiophene hydrochloride] (PMNT) and a label-free, mercury-specific oligonucleotide (MSO) probe. PMNT binds to the Hg2+ -free MSO and the Hg2+,MSO complex in different ways, and exhibits distinguishable and specific optical responses to the target-induced conformation change. [source] Adsorption of Hg2+ on a novel chelating fiber prepared by preirradiation grafting and aminationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2009Ying Yang Abstract A novel chelating fiber was prepared by the irradiation-induced grafting copolymerization of glycidyl methacrylate on polypropylene fiber and consequent amination with diethylenetriamine. The effects of the reaction conditions, such as reaction time, temperature, and monomer concentration, on the degree of grafting were investigated. The optimal conditions for grafting were found to be 3 h, 100°C, and a 50% (v/v) glycidyl methacrylate concentration in tetrahydrofuran solution. This fiber showed good adsorption performance at different concentrations of Hg2+, in particular for trace Hg2+. Under the adsorption conditions of pH = 4, initial concentration = 1000 mg/L, and time = 20 h, the adsorption capacity of the chelating fiber for Hg2+ reached 785.28 mg/g. It completely adsorbed the Hg2+ ions in solution within a short contact time, showing a very high adsorption rate for Hg2+. Furthermore, the chelating fiber also had a high selectivity for mercury, whereas Cu2+ coexisted in different concentrations. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Properties and application of poly(methacrylic acid- co -dodecyl methacrylate- cl - N,N -methylene bisacrylamide) hydrogel immobilized Bacillus cereus MTCC 8372 lipase for the synthesis of geranyl acetateJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008Madan Lal Verma Abstract A range of fatty acid esters is now being produced commercially with immobilized microbial lipases (glycerol ester hydrolases; EC) in nonaqueous solvents. In this study, a synthetic hydrogel was prepared by the copolymerization of methacrylic acid and dodecyl methacrylate in the presence of a crosslinker, N,N -methylene bisacrylamide. A purified alkaline thermotolerant bacterial lipase from Bacilluscereus MTCC 8372 was immobilized on a poly(methacrylic acid- co -dodecyl methacrylate- cl - N,N -methylene bisacrylamide) hydrogel by an adsorption method. The hydrogel showed a 95% binding efficiency for the lipase. The bound lipase was evaluated for its hydrolytic potential toward various p -nitrophenyl acyl esters with various C chain lengths. The bound lipase showed optimal hydrolytic activity toward p -nitrophenyl palmitate at a pH of 8.5 and a temperature of 55°C. The hydrolytic activity of the hydrogel-bound lipase was enhanced by Hg2+, Fe3+, and NH ions at a concentration of 1 mM. The hydrogel-bound lipase was used to synthesize geranyl acetate from geraniol and acetic acid in n -heptane. The optimization of the reaction conditions, such as catalyst loading, effect of substrate concentration, solvent (n -pentane, n -hexane, n -heptane, n -octane, and n -nonane), reaction time, temperature, molecular sieve (3 Å × 1.5 mm) and scale up (at 50-mL level), was studied. The immobilized lipase (25 mg/mL) was used to perform an esterification in n -alkane(s) that resulted in the synthesis of approximately 82.8 mM geranyl acetate at 55°C in n -heptane under continuous shaking (160 rpm) after 15 h when geraniol and acetic acid were used in a ratio of 100 : 100 mM. The addition of a molecular sieve (3 Å × 1.5 mm) to the reaction system at a concentration of 40 mg/mL in reaction volume (2 mL) resulted in an increase in the conversion of reactants into geranyl acetate (90.0 mM). During the repetitive esterification under optimum conditions, the hydrogel-bound lipase produced ester (37.0 mM) after the eighth cycle of reuse. When the reaction volume was scaled up to 50 mL, the ester synthesized was 58.7 mM under optimized conditions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Preparation of a heterogeneous hollow-fiber affinity membrane having a mercapto chelating resin and its recovery of Hg2+ cationsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008Bing Wang Abstract A kind of heterogeneous hollow-fiber affinity filter membrane with a high chelating capacity for Hg2+ was prepared by phase separation with blends of a mercapto chelating resin and polysulfone as the membrane materials, N,N -dimethylacetamide as the solvent, and water as the extraction solvent. The adsorption isotherms of the hollow-fiber affinity filter membrane for Hg2+ were determined. The heterogeneous hollow-fiber affinity filter membrane was used for the adsorption of Hg2+ cations through the coordination of the mercapto group and Hg2+ cations, and the effects of the morphology and structure of the affinity membrane on the chelating properties were investigated. The chelating conditions, including the chelating resin grain size, pH value, concentration of the metallic ion solution, mobile phase conditions, and operating parameters, had significant effects on the chelating capacity of the hollow-fiber affinity filter membrane. The results revealed that the greatest chelating capacity of the hollow-fiber affinity filter membrane for Hg2+ was 1090 ,g/cm2 of membrane under appropriate conditions, and the adsorption isotherms of Hg2+ could be described by the Langmuir isotherm. The dynamic chelating experiments indicated that the hollow-fiber affinity membrane could be operated at a high feed flow rate and that large-scale removal of Hg2+ could be realized. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Binding of several heavy metal ions by polyaspartyl polymers and their application to some Chinese herbal medicinesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007Bo Sun Abstract Water-insoluble polyaspartyl polymers were synthesized by using water as medium instead of organic medium. Taking Ca2+ as a reference, the binding of several heavy-metal ions, including Pb2+, Cd2+, Hg2+, Cr3+, Cu2+, and Mn2+, by polyaspartyl polymers was studied. The experimental results revealed that polyaspartate is an excellent binding agent for the investigated heavy-metal ions. These cation ions were bound to polyaspartate polymer by the same mechanism as Pb2+, which can be explained by ion exchange model. Since polyaspartate has a protein-resembling structure that is sensitive to trace heavy metal, it was used to remove some trace heavy-metal elements in Chinese herbal medicines. It was found that polyaspartate material was an effective agent for the removal of Pb2+, Cd2+, and Hg2+ ions from glycyrrhizin, angelica, and gynostemma pentaphyllum. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Properties of poly(AAc- co -HPMA- cl -EGDMA) hydrogel-bound lipase of Pseudomonas aeruginosa MTCC-4713 and its use in synthesis of methyl acrylateJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Shamsher Singh Kanwar Abstract Microbial lipases (E.C. 3.1.1.3) are preferred biocatalysts for the synthesis of esters in organic solvents. Various extracellular thermoalkaliphilic lipases have been reported from Pseudomonas sp. In the present study, a purified alkaline thermoalkalophilic extracellular lipase of Pseudomonas aeruginosa MTCC-4713 was efficiently immobilized onto a synthetic poly(AAc- co -HPMA- cl -EGDMA) hydrogel by adsorption and the bound lipase was evaluated for its hydrolytic potential towards various p -nitrophenyl acyl esters varying in their C-chain lengths. The bound lipase showed optimal hydrolytic activity towards p -nitrophenyl palmitate (p -NPP) at pH 8.5 and temperature 45°C. The hydrolytic activity of the hydrogel-bound lipase was markedly enhanced by the presence of Hg2+, Fe3+, and NH salt ions in that order. The hydrogel-immobilized lipase (25 mg) was used to perform esterification in various n -alkane(s) that resulted in , 84.9 mM of methyl acrylate at 45°C in n -heptane under shaking (120 rpm) after 6 h, when methanol and acrylic acid were used in a ratio of 100 mM:100 mM, respectively. Addition of a molecular sieve (3Å × 1.5 mm) to the reaction system at a concentration of 100 mg/reaction vol (1 mL) resulted in a moderate enhancement in conversion of reactants into methyl acrylate (85.6 mM). During the repetitive esterification under optimum conditions, the hydrogel-bound lipase produced 71.3 mM of ester after 10th cycle of reuse. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 183,191, 2007 [source] Novel thermostable serine collagenase from Thermoactinomyces sp.JOURNAL OF BASIC MICROBIOLOGY, Issue 4 200621E: purification, some properties A thermophilic actinomycete strain Thermoactinomyces sp. 21E producing a highly thermostable serine collagenase was isolated from Bulgarian soil. The collagenase, produced extracellular by Thermoactinomyces sp. 21E, was purified to homogeneity by heat treatment, ultrafiltration, saturation with ammonium sulfate and gel filtration chromatography with a 101-fold increase in specific activity and 58% recovery. The collagenase has a relative molecular mass of 50000 by SDS-PAGE. The optimum temperature for the enzyme activity was 60,65 °C in the absence of Ca2+ and 70,75 °C in the presence of Ca2+. About 40% of the original activity remaining after incubation at 85 °C for 30 min in the presence of Ca2+. The optimum pH for the enzyme activity was 9.0,9.5 and the enzyme was stable for 1h at 70 °C in the pH range from 7.5 to 12.5. The collagenase was strongly inhibited by active-site inhibitors of serine protease PMSF and DFP, which indicated that the enzyme is serine protease. The enzyme activity was completely inhibited by Hg2+, Cu2+ and Fe2+. However, Ca2+ strongly activated the collagenase activity. The collagenase from Thermoactinomyces sp. 21E showed high activity toward type I collagen, acid-soluble collagen, gelatin and Pz-PLGPR. However, elastin for collagenase was inert as substrate. The properties of the collagenase from strain 21E suggest that this enzyme is a new collagenolytic protease that differs from the collagenases and serine proteases reported so far. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Purification and characterization of the main laccase produced by the white-rot fungus Pleurotus pulmonarius on wheat bran solid state mediumJOURNAL OF BASIC MICROBIOLOGY, Issue 4 2003Cristina Giatti Marques de Souza The wood-degrading fungus Pleurotuspulmonarius produces at least two laccase isoforms, Lcc1 and Lcc2, when grown on wheat bran solid state medium. The main laccase, Lcc2, was purified to apparent electrophoretic homogeneity by using acetone precipitation, anion-exchange chromatography and gel filtration. Lcc2 had been purified 5.9-fold with a yield of 49%. A specific activity of 19,750 U/mg protein was found using syringaldazine as a substrate under standard assay conditions. The enzyme is a homodimeric glycoprotein containing 44% glycosilation and an apparent molecular mass of 46 kDa. Type I and type III Cu2+ centers were identified by spectrophotometry. The laccase showed optimal activity at pH 6.2,6.5, 4.0,5.5, and 6.0,8.0 with syringaldazine, ABTS and guaiacol as substrates, respectively. For all substrates, the highest oxidation rates were obtained at 50 °C. The enzyme was stable over a large range of pH (4.5,8.0) and at temperatures up to 50 °C. Under standard assay conditions, the apparent KM values were 12, 210 and 550 ,M for syringaldazine, ABTS and guaiacol, respectively. Purified Lcc2 was strongly inhibited by sodium azide, 2-mercaptoethanol and Hg2+, and slightly inhibited by Mn+2 and the chelant agents, EDTA and EGTA. The enzyme was activated by Cu2+ and it retained a high percentage of its activity in the presence of organic solvents, such as acetonitrile and acetone. [source] Purification and Characterization of an ,-L-Rhamnosidase from Aspergillus terreus of Interest in WinemakingJOURNAL OF FOOD SCIENCE, Issue 2 2001M.V. Gallego ABSTRACT: An enzyme with ,-L-rhamnosidase activity was purified to homogeneity from a culture filtrate of Aspergillus terreus after growth in a medium containing L-rhamnose as the sole carbon source. The biosynthesis of this enzyme was repressed by glucose. The enzyme had a molecular mass of 96 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and an isoelectric point of 4.6 as determined by analytical isoelectric focusing. The pH and temperature optima for the enzyme were found to be 4.0 and 44 °C, respectively. Using p-nitrophenyl-,-L-rhamnopyranoside as a substrate, the enzyme exhibited Michaelis-Menten kinetics with KM and Vmax values of 0.17 mM and 84 U/mg, respectively. The enzyme was inhibited competitively by L-rhamnose (K1 2.5 mM). Divalent cations such as Ca2+ Mg2+ Zn2+ and Co2+ stimulated the a-L-rhamnosidase activity, whereas this was inhibited by Hg2+ and Cd2+. Ethanol (12% v/v) and glucose (21% w/v) decreased enzyme activity by approximately 20%, while this was not affected by SO2. [source] Technical Approach to Simplify the Purification Method and Characterization of Microbial Transglutaminase Produced from Streptoverticillium ladakanumJOURNAL OF FOOD SCIENCE, Issue 1 2000M.-L. Ho ABSTRACT: In order to fast and economically purify MTGase from Streptoverticillium ladakanum, a stepwise elution method was developed and compared with linear gradient elution method. MTGase was purified to electrophoretical homogeneity by using CM Sepharose CL-6B and Blue Sepharose Fast Flow chromatographies by linear gradient or stepwise methods. The recovery of MTGase by linear gradient and stepwise methods were 68.4% and 81.0%, respectively. The optimal temperature and pH were 40 °C and 5.5, respectively. It was stable at pH 5.0 to 7.0 and had a rate constant (KD) of 6.21 °o 10 -5 min -1 for thermal inactivation at 45 °C. The purified MTGase was activated by K+ Na+, Ca2+, Mn2+, and Mg2+, not affected by Fe3+, EDTA, but inhibited by Cu2+, Zn2+, Hg2+, Ni2+, Co2+, Cd2+, PCMB, NEM, IAA, and PMSF. A simple stepwise method was developed for the purification of MTGase from S. ladakanum. [source] Fluorescent behavior of 2-(3,4,5,6-tetrafluoro-2-hydroxyphenyl)imidazo-[1,2- a]pyridine in the presence of metal perchlorateJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 2 2007Kiyoshi Tanaka 2-(3,4,5,6-Tetrafluoro-2-hydroxyphenyl)imidazo[1,2- a]pyridine (1) emits long wavelength light around 540 nm both in polar and in nonpolar solvents. Zn2+ perchlorate in acetonitrile causes the intermediate wavelength emission around 430 nm, which is ascribed to the species where the imidazole nitrogen atom and the phenolate oxygen atom bridge Zn2+. In the presence of Hg2+ and Al3+ perchlorates, short wavelength emission around 370 nm is strongly increased and this fluorescent enhancement is attributable not to the coordination of Hg2+ and Al3+ to 1 but to the formation of the salt of perchloric acid of 1. [source] Interaction of cysteine with Cu2+ and group IIb (Zn2+, Cd2+, Hg2+) metal cations: a theoretical studyJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 3 2005M. Belcastro Abstract The structure and energetics of complexes obtained upon interaction between cysteine and Zn2+, Cd2+, Hg2+ and Cu2+ cations were studied using quantum chemical density functional theory calculations with the 6,311++G** orbital basis set and relativistic pseudopotentials for the cations. Different coordination sites for metal ions on several cysteine conformers were considered. In their lowest energy complexes with the amino acid, the Zn2+ and Cd2+ cations appear to be three-coordinated to carbonyl oxygen, nitrogen and sulfur atoms, whereas the Cu2+ and Hg2+ ions are coordinated to both the carbonyl oxygen and sulfur atoms of one of the zwitterion forms of the amino acid. Bonds of metal cations with the coordination sites are mainly ionic except those established with sulfur, which show a small covalent character that become most significant when Cu2+ and Hg2+ are involved. The order of metal ion affinity proposed is Cu > Zn > Hg > Cd. Copyright © 2005 John Wiley & Sons, Ltd. [source] Neuronal uptake and metabolism of glycerol and the neuronal expression of mitochondrial glycerol-3-phosphate dehydrogenaseJOURNAL OF NEUROCHEMISTRY, Issue 4 2003Nga Huynh Tran Nguyen Abstract Glycerol is effective in the treatment of brain oedema but it is unclear if this is due solely to osmotic effects of glycerol or whether the brain may metabolize glycerol. We found that intracerebral injection of [14C]glycerol in rat gave a higher specific activity of glutamate than of glutamine, indicating neuronal metabolism of glycerol. Interestingly, the specific activity of GABA became higher than that of glutamate. NMR spectroscopy of brains of mice given 150 µmol [U- 13C]glycerol (0.5 m i.v.) confirmed this predominant labelling of GABA, indicating avid glycerol metabolism in GABAergic neurones. Uptake of [14C]glycerol into cultured cerebellar granule cells was inhibited by Hg2+, suggesting uptake through aquaporins, whereas Hg2+ stimulated glycerol uptake into cultured astrocytes. The neuronal metabolism of glycerol, which was confirmed in experiments with purified synaptosomes and cultured cerebellar granule cells, suggested neuronal expression of glycerol kinase and some isoform of glycerol-3-phosphate dehydrogenase. Histochemically, we demonstrated mitochondrial glycerol-3-phosphate dehydrogenase in neurones, whereas cytosolic glycerol-3-phosphate dehydrogenase was three to four times more active in white matter than in grey matter, reflecting its selective expression in oligodendroglia. The localization of mitochondrial and cytosolic glycerol-3-phosphate dehydrogenases in different cell types implies that the glycerol-3-phosphate shuttle is of little importance in the brain. [source] Polymer-based fluorescence sensors incorporating chiral binaphthyl and benzo[2,1,3]thiadiazole moieties for Hg2+ detectionJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2010Xiaobo Huang Abstract Three chiral polymers P-1, P-2, and P-3 could be obtained by the polymerization of (R)-6,6,-dibutyl-3,3,-diiodo-2, 2,-binaphthol (R -M-1), (R)-6,6,-dibutyl-3,3,-diiodo-2,2,-bisoctoxy-1,1,-binaphthyl (R -M-2), and (R)-6,6,-dibutyl-3,3,-diiodo-2,2,-bis (diethylaminoethoxy)-1,1,-binaphthyl (R -M-3) with 4,7-diethynyl-benzo[2,1,3]-thiadiazole (M-1) via Pd-catalyzed Sonogashira reaction, respectively. P-1, P-2, and P-3 can show pale red, blue,green, and orange fluorescence. The responsive optical properties of these polymers on various metal ions were investigated by fluorescence spectra. Compared with other cations, such as Co2+, Ni2+, Ag+, Cd2+, Cu2+, and Zn2+, Hg2+ can exhibit the most pronounced fluorescence response of these polymers. P-1 and P-2 show obvious fluorescence quenching effect upon addition of Hg2+, on the contrary, P-3 shows fluorescence enhancement. Three polymer-based fluorescent sensors also show excellent fluorescence response for Hg2+ detection without interference from other metal ions. The results indicate that these kinds of tunable chiral polybinaphthyls can be used as fluorescence sensors for Hg2+ detection. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 997,1006, 2010 [source] Purification and biochemical characterisation of a novel glutamate decarboxylase from rice branJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 6 2010Li Wang Abstract BACKGROUND: Glutamate decarboxylase (GAD) is a useful enzyme whose main function is to catalyse the irreversible ,-decarboxylation of L -glutamate to produce ,-aminobutyric acid. The cheap and abundant rice-processing by-product rice bran contains a high amount of GAD, the purification and characterisation of which have not yet been reported. In this study, research on rice bran GAD was initiated. RESULTS: Rice bran GAD was purified to homogeneity via a combined purification protocol of ammonium sulfate fractionation, ion exchange chromatography and two gel filtrations, with a purification fold of 128.6 and an activity recovery of 21.3%. The enzyme was active at pH 5.5 and 40 °C and retained 80% of its original activity in the pH range 5,9 and the temperature range 30,50 °C. GAD activity was significantly enhanced in the presence of Ca2+ but strongly inhibited by Ag+, Hg2+, sodium dodecyl sulfate and CH3COOH. Kinetic determination of the apparent Km for L -glutamate and pyridoxal 5,-phosphate gave values of 27.4 mmol L,1 and 1.16 µmol L,1 respectively. CONCLUSION: Considering that rice bran is cheap and commercially available and that rice bran GAD is relatively stable, the development of cost-effective rice bran GAD-related functional foods would seem to be feasible. Copyright © 2010 Society of Chemical Industry [source] | ||||||||||||||||||||||||||||||||||