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Kinds of OH Terms modified by OH Selected AbstractsNew Heterodimetallic Platinum(II) Complexes Potentially Useful as Molecular SwitchesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 10 2008Sonia Pérez Abstract Four types of platinum(II) complexes of general formulae [Pt(FcCH=NC6H4OH-2)Cl2(L)] [Fc = (,5 -C5H5)Fe(,5 -C5H4), L = dmso (2) or PhCN (3)], [Pt(FcCH=NC6H4O-2)Cl(dmso)] (4), [Pt{(,5 -C5H3CH=NC6H4O-2)Fe(,5 -C5H5)}(L)] [L = dmso (5) or PPh3 (6)] or [Pt{(,5 -C5H3CH=NC6H4OH-2)Fe(,5 -C5H5)}Cl(L)] [L = dmso (7) or PPh3 (8)] have been prepared. These compounds differ in the mode of binding of the ligand: (N) (in 2 and 3), (N,O), (in 4), [C(sp2, ferrocene),N,O]2, (in 5 and 6) or [C(sp2, ferrocene),N], (in 7 and 8). NMR, UV/Vis and electrochemical studies of 2 and 4,8 reveal that these products can be grouped in three pairs [(2c, 4b), (5, 7) and (6, 8)], and one of the compounds of each pair can be easily converted into its partner by a H+/OH, chemical input. The results obtained revealed that these transformations, that affect the spectroscopic and electrochemical properties, are reversible and robust. A study of the relevancy of the mode of binding of compounds 2 and 4,8 upon their potential utility of the new platinum(II) complexes as molecular switches is reported. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Production and X-ray crystallographic analysis of fully deuterated human carbonic anhydrase IIACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 1 2006Monika Budayova-Spano Human carbonic anhydrase II (HCA II) is a zinc metalloenzyme that catalyzes the reversible hydration and dehydration of carbon dioxide and bicarbonate, respectively. The rate-limiting step in catalysis is the intramolecular transfer of a proton between the zinc-bound solvent (H2O/OH,) and the proton-shuttling residue His64. This distance (,7.5,Å) is spanned by a well defined active-site solvent network stabilized by amino-acid side chains (Tyr7, Asn62, Asn67, Thr199 and Thr200). Despite the availability of high-resolution (,1.0,Å) X-ray crystal structures of HCA II, there is currently no definitive information available on the positions and orientations of the H atoms of the solvent network or active-site amino acids and their ionization states. In preparation for neutron diffraction studies to elucidate this hydrogen-bonding network, perdeuterated HCA II has been expressed, purified, crystallized and its X-ray structure determined to 1.5,Å resolution. The refined structure is highly isomorphous with hydrogenated HCA II, especially with regard to the active-site architecture and solvent network. This work demonstrates the suitability of these crystals for neutron macromolecular crystallography. [source] Enzyme immobilization on ultrafine cellulose fibers via poly(acrylic acid) electrolyte graftsBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2005Hong Chen Abstract Ultrafine cellulose fiber (diameter 200,400 nm) surfaces were grafted with polyacrylic acid (PAA) via either ceric ion initiated polymerization or methacrylation of cellulose with methacrylate chloride (MACl) and subsequent free-radical polymerization of acrylic acid. PAA grafts by ceric ion initiated polymerization increased with increasing reaction time (2,24 h), monomer (0.3,2.4 M), and initiator (1,10 mM) concentrations, and spanned a broad range from 5.5,850%. PAA grafts on the methacrylated cellulose fibers also increased with increasing molar ratios of MACl to cellulosic hydroxyl groups (MACl/OH, 2,6.4) and monomer acrylic acid (AA) to initiator potassium persulfate (KPS) ratios ([AA]/[KPS], 1.5,6), and were in a much narrower range between 12.8% and 29.4%. The adsorption of lipase (at 1 mg/ml lipase and pH 7) and the activity of adsorbed lipase (pH 8.5, 30°C), in both cases decreased with increasing PAA grafts. The highest adsorption and activity of the lipase on the ceric ion initiated grafted fibers were 1.28 g/g PAA and 4.3 U/mg lipase, respectively, at the lowest grafting level of 5.5% PAA, whereas they were 0.33 g/g PAA and 7.1 U/mg lipase, respectively, at 12.8% PAA grafts on the methacrylated and grafted fibers. The properties of the grafted fibers and the absorption behavior and activity of lipase suggest that the PAA grafts are gel-like by ceric-initiated reaction and brush-like by methacrylation and polymerization. The adsorbed lipase on the ceric ion-initiated grafted surface possessed greatly improved organic solvent stability over the crude lipase. The adsorbed lipases exhibited 0.5 and 0.3 of the initial activity in the second and third assay cycles, respectively. © 2004 Wiley Periodicals, Inc. [source] Studies on thermoplastic polyurethanes based on new diphenylethane-derivative diols.JOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2008Abstract Two series of poly(ether urethane)s and one series of poly(ester urethane)s were synthesized, containing, respectively, poly(oxytetramethylene) diol (PTMO) of Mn = 1000 and 2000 and poly(,-caprolactone) diol of Mn = 2000 as soft segments. In each series the same hard segment, i.e., 4,4,-(ethane-1,2-diyl)bis(benzenethiohexanol)/hexane-1,6-diyl diisocyanate, with different content (, 14,72 wt %) was used. The polymers were prepared by a one-step melt polymerization in the presence of dibutyltin dilaurate as a catalyst, at the molar ratio of NCO/OH = 1 (in the case of the polymers from PTMO of Mn = 1000 also at 1.05). For all polymers structures (by FTIR and X-ray diffraction analysis) and physicochemical, thermal (by differential scanning calorimetry and thermogravimetric analysis), and tensile properties as well as Shore A/D hardness were determined. The resulting polymers were thermoplastic materials with partially crystalline structures (except the polymer with the highest content of PTMO of Mn = 2000). It was found that the poly(ether urethane)s showed lower crystallinity, glass-transition temperature (Tg), and hardness as well as better thermal stability than the poly(ester urethane)s. Poly(ether urethane)s also exhibited higher tensile strength (up to 23.5 MPa vs. 20.3 MPa) and elongation at break (up to , 1950% vs. 1200%) in comparison with the corresponding poly(ester urethane)s. Among the poly(ether urethane)s an increase in soft-segment length was accompanied by an increase in thermal stability, tensile strength, and elongation at break, as well as a decrease in Tg, crystallinity, and hardness. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Reactions leading to the formation and breakdown of stilpnomelane in the Otago Schist, New ZealandJOURNAL OF METAMORPHIC GEOLOGY, Issue 4 2000G. Li Semi-pelitic rocks ranging in grade from the prehnite,pumpellyite to the greenschist facies from south-eastern Otago, New Zealand, have been investigated in order to evaluate the reactions leading to formation and breakdown of stilpnomelane. Detrital grains of mica and chlorite along with fine-grained authigenic illite and chlorite occur in lower-grade rocks with compactional fabric parallel to bedding. At higher grades, detrital grains have undergone dissolution, and metamorphic phyllosilicates have crystallized with preferred orientation (sub)parallel to bedding, leading to slaty cleavage. Stilpnomelane is found in metapelites of the pumpellyite,actinolite facies and the chlorite zone of the greenschist facies, but only rarely in the biotite zone of the greenschist facies. Illite or phengite is ubiquitous, whereas chlorite occurs only rarely with stilpnomelane upgrade of the pumpellyite-out isograd. Chemical and textural relationships suggest that stilpnomelane formed from chlorite, phengite, quartz, K-feldspar and iron oxides. Stilpnomelane was produced by grain-boundary replacement of chlorite and by precipitation from solution, overprinting earlier textures. Some relict 14 Å chlorite layers are observed by TEM to be in the process of transforming to 12 Å stilpnomelane layers. The AEM analyses show that Fe is strongly partitioned over Mg into stilpnomelane relative to chlorite (KD,2.5) and into chlorite relative to phengite (KD,1.9). Modified A,FM diagrams, projected from the measured phengite composition rather than from ideal KAl3Si3O10(OH)2, are used to elucidate reactions among chlorite, stilpnomelane, phengite and biotite. In addition to pressure, temperature and bulk rock composition, the stilpnomelane-in isograd is controlled by variations in K, Fe3+/Fe2+, O/OH and H2O contents, and the locus of the isograd is expected to vary in rocks of different oxidation states and permeabilities. Biotite, quartz and less phengitic muscovite form from stilpnomelane, chlorite and phengite in the biotite zone. Projection of bulk rock compositions from phengite, NaAlO2, SiO2 and H2O reveals that they lie close to the polyhedra defined by the A,FM minerals and albite. Other extended A,FM diagrams, such as one projected from phengite, NaAlO2, CaAl2O4, SiO2 and H2O, may prove useful in the evaluation of other low-grade assemblages. [source] Defect structure and spectroscopic characteristics of codoped Hf: Er: LiNbO3 crystalsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 4 2009Liang Sun Abstract Codoped Hf: Er: LiNbO3 crystals have been grown by the Czochralski technique. Defect structures of the crystals were analyzed by IR absorption spectra, and the compositions of the crystals were measured by X-ray fluorescent spectrograph. A new OH, -associated vibrational peak at 3492 cm,1 was revealed in 6 mol % Hf: 1 mol % Er: LiNbO3 crystal. It was attributed to (HfNb), -OH, -(ErNb)2, defect centers. The Er3+ concentrations in crystals gradually decreased with the increase of the codoped Hf4+ concentrations in the melts. The emission characteristics of the crystals were investigated by the fluorescence spectrum. It was found that the luminescent intensity in codoped 6 mol % Hf: 1 mol % Er: LiNbO3 crystal was 3.5 times stronger than that in single doped 1 mol % Er: LiNbO3 crystal. The luminescent enhancement effect was successfully explained on the basis of defect structure of the crystals. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Structural and spectroscopic study of Mg13.4(OH)6(HVO4)2(H0.2VO4)6CRYSTAL RESEARCH AND TECHNOLOGY, Issue 11 2008Abstract Single-crystals of the polar compound magnesium hydrogen vanadate(V), Mg13.4(OH)6(HVO4)2(H0.2VO4)6, were synthesized hydrothermally. It represents the first hydrogen vanadate(V) among inorganic compounds. Its structure was determined by single-crystal X-ray diffraction [space group P 63mc, a = 12.9096(2), c = 5.0755(1) Å, V = 732.55(2) ų, Z = 1]. The crystal structure of Mg13.4(OH)6(HVO4)2(H0.2VO4)6 consists of well separated, vacancy-interrupted chains of face sharing Mg2O6 octahedra, with short Mg2,Mg2 distances of 2.537(1) Å, embedded in a porous magnesium vanadate 3D framework having the topology of the zeolite cancrinite. All three hydrogen positions in the structure were confirmed by FTIR spectroscopy. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Influence of citric acid on calcium sulfate dihydrate crystallization in aqueous mediaCRYSTAL RESEARCH AND TECHNOLOGY, Issue 2 2007S. Titiz-Sargut Abstract The crystallization of Calcium sulfate dihydrate produced by the reaction between pure Ca(OH)2 suspension and H2SO4 solution was investigated at different pH values, temperatures and citric acid concentrations. Crystal size distributions, filtration rates and zeta potentials of gypsum were determined as a function of citric acid concentrations at pH 3.5 and 65°C. The influence of citric acid on the morphology of gypsum was also investigated and discussed. The average particle size of gypsum was reached to maximum in the presence of approximately 2500 ppm citric acid concentration, where the minimum cake resistance and maximum filtration rate were obtained. In the presence of citric acid, various crystal morphologies such as tabular, plate-like, double-taper leaf-like and flower-like, etc., were obtained. The change of morphology is related to the preferential adsorption of citric acid on different crystallographic faces. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Comparative assessment of time-related bioactive glass and calcium hydroxide effects on mechanical properties of human root dentinDENTAL TRAUMATOLOGY, Issue 1 2009Monika Marending These materials have a disinfecting capacity similar to Ca(OH)2, but bear the advantage of bioactivity. However, because bioactive glasses initially act as alkaline biocides just as Ca(OH)2 does, they may also negatively affect mechanical dentin properties over time. This was assessed in the current study using standardized human root dentin bars. Specimens were immersed in 1:20 (wt vol,1) suspensions of nanometric bioactive glass 45S5 or calcium hydroxide for 1, 10, or 30 days. Control specimens were immersed in pure saline for 30 days (n = 20 per group). Subsequently, modulus of elasticity (E) and flexural strength (FS) of the specimens were determined. Results were compared between groups using one-way anova and Scheffé's post-hoc test. Ca(OH)2 caused a significant (P < 0.001) 35% drop in mean flexural strength values compared to the control treatment after 10 days. No further change was observed between 10 days and 30 days. Bioactive glass caused a 20% drop in mean flexural strength as compared to the control after 10 days. However, this difference did not reach statistical significance (P > 0.05). No effects of either material on dentin modulus of elasticity values were observed. It was concluded that the calcium hydroxide suspension affected the dentin more than the bioactive glass counterpart; however, the effect was self-limiting and probably restricted to superficial dentin layers, as suggested by the mere decrease in flexural strength but not in modulus of elasticity values. [source] Comparison of acidic fibroblast growth factor on collagen carrier with calcium hydroxide as pulp capping agents in monkeysDENTAL TRAUMATOLOGY, Issue 5 2007Zhimei Li Abstract,,, Acidic fibroblast growth factor (aFGF) has been shown to facilitate wound healing by stimulating fibroblast proliferation and angiogenesis. It has also been reported to possess a powerful anti-apoptotic function This study compared the histological pulp responses to aFGF on collagen carrier and Ca(OH)2 placed on the mechanically exposed dental pulp in monkeys at two observation periods. Thirty-six teeth with pulp exposures were distributed into three groups according to the capping agents used prior to application of the coronal seal: collagen-based matrix carrier (group 1), aFGF on the collagen-based matrix carrier (group 2) and aqueous calcium hydroxide [Ca(OH)2] paste (group 3). Specimens were harvested at 6 and 13 weeks postoperatively and prepared for hematoxylin and eosin, and Gram staining. Histological qualitative evaluation of pulp responses were performed under the light microscope following criteria modified from Cox et al. (17) and Hu et al. (18). Semi-quantitative analysis was also carried out using Kruskal,Wallis and Mann,Whitney U -tests. There was neither negligible inflammatory infiltrates with no bacteria present in the three groups at both timings, nor was there any significant difference in the soft tissue organization among the three groups at or between the 6- and 13-week observation periods. At 6 weeks, the hard tissue barrier produced by Ca(OH)2 group (1.040 ± 0.089) was significantly more superior than aFGF/collagen carrier group (1.930 ± 0.825) (P = 0.030) as well as collagen carrier group (3.142 ± 1.069, P = 0.018). At 13 weeks, both aFGF/collagen carrier group (1.214 ± 0.485) and the collagen carrier group (1.457 ± 0.814) produced significantly better hard tissue barrier (P = 0.040 and P = 0.017, respectively) than earlier timing. However, these two groups did not induce significantly improved hard tissue barrier compared to that produced by aqueous Ca(OH)2 paste which stimulated matrix secretion in a polar tubular dentin-like pattern. [source] Baseline serum 25-hydroxyvitamin D concentrations in the Tromsø Study 1994,95 and risk of developing type 2 diabetes mellitus during 11 years of follow-upDIABETIC MEDICINE, Issue 10 2010G. Grimnes Diabet. Med. 27, 1107,1115 (2010) Abstract Aims, We wanted to test the hypothesis that low serum 25-hydroxyvitamin D (25(OH)D) concentrations are associated with increased risk of developing Type 2 diabetes mellitus (DM) in a population-based cohort during 11 years of follow-up. Methods, The analyses included 4157 non-smokers and 1962 smokers from the Tromsø Study 1994,95 without diabetes at baseline. Subsequent Type 2 DM was defined using a hospital journal-based end-point registry, completed through the year 2005. Participants were allocated into quartiles of serum 25(OH)D within each month to account for seasonal variation, and serum 25(OH)D values both as a continuous variable and in quartiles were used in Cox regression models. The analyses were stratified by smoking. Adjustments were made for age, sex, body mass index (BMI), physical activity and, in non-smokers, former smoking. Results, Type 2 DM was registered in 183 non-smoking and 64 smoking participants. Using the fourth (highest) quartile of serum 25(OH)D as the reference, non-smoking participants in the third, second and first quartiles had age- and sex-adjusted hazard ratios (95% confidence intervals) of incident Type 2 DM of 1.00 (0.62,1.61), 1.50 (0.97,2.31) and 1.89 (1.25,2.88), respectively, whereas the corresponding values for smokers were 1.79 (0.77,4.19), 2.33 (1.02,5.35) and 2.68 (1.18,6.08). Adjustment for BMI attenuated the hazard ratios, and they were no longer significant. Conclusions, Baseline serum 25(OH)D was inversely associated with subsequent Type 2 DM in a population-based 11 year follow-up study, but not after adjustment for BMI. Randomized trials are needed to define the possible role of serum 25(OH)D status, and thereby the role of supplementation, in the prevention of Type 2 DM. [source] Prospective screening for biopsy proven coeliac disease, autoimmunity and malabsorption markers in Belgian subjects with Type 1 diabetesDIABETIC MEDICINE, Issue 7 2005M. Buysschaert Abstract Aims To determine prospectively the prevalence of biopsy proven coeliac disease (CD) in an adult Type 1 diabetic population from Belgium with regards to associated auto-immunity and malabsorption. Methods and results Determination in 400 Type 1 diabetic patients of serum anti-endomysial and/or anti-transglutaminase auto-antibodies. All subjects with abnormal serology underwent an intestinal biopsy. Ten patients (2.5%) had positive antibodies. Diagnosis of CD was confirmed by an intestinal biopsy. Eight patients were symptom-free, although laboratory findings suggesting malabsorption were prominent in the presence of CD [microcytic anaemia, iron and folate deficiencies, low levels of 25(OH)vitamin D3, calcium and cholesterol]. Other auto-immune conditions, especially vitiligo, were found in patients with CD. Conclusions Asymptomatic coeliac disease occurs frequently in adult Type 1 diabetic patients, and is often associated with subclinical malabsorption. Screening should be part of routine evaluation, to implement life-long dietary gluten avoidance. [source] Multi-year tracking of sediment sources in a small agricultural watershed using rare earth elementsEARTH SURFACE PROCESSES AND LANDFORMS, Issue 14 2006A. Kimoto Abstract Rare earth elements (REEs) have been successfully used as a sediment tracer, but the REE technique has never been used for studying sediment sources for a multi-year period. A nearly four-year field experiment was conducted on a small agricultural watershed near Coshocton, OH, USA, to assess the applicability of the REE technique for a multi-year period and to evaluate the relative contributions of sediment sources in the watershed. Tracer depletion and tracer enrichment ratio (ratio of the tracer concentrations in sediment to the concentrations in the soil in the areas of application) were evaluated to examine the applicability and accuracy of the technique. A minimum of 91 per cent of the mass of the applied elements was still available on any individual morphological element at the end of the experimental period. The tracer enrichment ratio varied from 0·4 to 2·3, and it was not significantly related to time. The relative contributions of six morphological elements within the watershed were evaluated as proportions to total sediment yield. The relative contribution of the lower channel was significantly increased as a function of the amount of sediment yield, while that of the lower backslope was significantly decreased. The relative contribution of the lower channel significantly decreased as a function of cumulative sediment yield, while the contributions of the shoulder and the upper backslope significantly increased. Our results showed that the REE technique can be used to track sediment sources for a relatively long period with two limitations or potential sources of error associated with a selective depletion of tracers and a contamination of downslope areas with tagged sediments from upslope areas. Copyright © 2006 John Wiley & Sons, Ltd. [source] The Determination of Methanol Using an Electrolytically Fabricated Nickel Microparticle Modified Boron Doped Diamond ElectrodeELECTROANALYSIS, Issue 5 2010Kathryn Abstract A nickel modified boron doped diamond (Ni-BDD) electrode and nickel foil electrode were used in the determination of methanol in alkaline solutions. The Ni-BDD electrode was electrodeposited from a 1,mM Ni(NO3)2 solution (pH,5), followed by repeat cycling in KOH. Subsequent analysis utilised the Ni(OH)2/NiOOH redox couple to electrocatalyse the oxidation of methanol. Methanol was determined to limits of 0.3,mM with a sensitivity of 110,nA/mM at the Ni-BDD electrode. The foil electrode was less sensitive achieving a limit of 1.6,mM and sensitivity of 27,nA/mM. SEM analysis of the electrodes found the Ni-BDD to be modified by a quasi-random microparticle array. [source] Electrochemical Study of Anionic Ferrocene Derivatives Intercalated in Layered Double Hydroxides: Application to Glucose Amperometric BiosensorsELECTROANALYSIS, Issue 3-5 2009Christine Mousty Abstract Layered double hydroxides (Zn2Cr(OH)6X,nH2O LDH) containing (3-sulfopropyl)ferrocene-carboxylate (FcPSO3) and 1,1,-bis(3-sulfopropyl)ferrocene-carboxylate (Fc(PSO3)2) as interlayer anions (X) have been prepared by the co-precipitation method and characterized by PXRD, FTIR, SEM and XPS. The electrochemical behavior of these hybrid materials has been evaluated by cyclic voltammetry. A new amperometric biosensor based on the immobilization of glucose oxidase in ZnCr-FcPSO3 hybrid material was presented, the intercalated anions playing the role of mediators that shuttle electrons between the FAD centers in the enzyme and the electrode surface. The performance of the resulting biosensor for glucose determination under anaerobic conditions was evaluated by chronoamperometry at 0.5,V. The sensitivity (65,mA M,1 cm,2) determined in the concentration range 10,25,,M is higher than sensitivities reported for other glucose biosensors based on LDH host matrices. [source] Preparation of Novel Arrays Silver Nanoparticles Modified Polyrutin Coat-Paraffin-Impregnated Graphite Electrode for Tyrosine and Tryptophan's OxidationELECTROANALYSIS, Issue 8 2008Guan-Ping Jin Abstract A novel array silver nanoparticles and Rutin complex film modified paraffin-impregnated graphite electrode was proposed in this work (denoted as Ag/Rutin/WGE). The characteristics were investigated by the field emission scanning electron microscopy (FE-SEM), infrared spectra (IR), UV-visible (UV), X-ray photoelectron spectroscopy (XPS) and electrochemical techniques. Silver ions were gradually chelated by polyrutin film at 4,-oxo-5,-OH and 5-OH-4-oxo sites accompanying adsorption, then. Silver nanoparticles were highly-dispersed electrodeposited on polyrutin film. The electrochemical behaviors of tyrosine (Tyr) and tryptophan (Trp) were studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The Ag/Rutin/WGE electrode shows overlapping catalysis for the oxidation of Tyr and Trp. The linear response of Tyr and Trp were 0.3,10.0 and 0.7,70.0,,M with detection limit of 0.07 and 0.1,,M in a signal-to-noise ratio of 3. [source] Fabrication of Active Horseradish Peroxidase Micropatterns with a High Resolution by Scanning Electrochemical MicroscopyELECTROANALYSIS, Issue 16 2007Xuemei Li Abstract We used a new reactive species OH, to fabricate active horseradish peroxidase (HRP) micropatterns with a high resolution by scanning electrochemical microscopy (SECM) coupled with a carbon fiber disk electrode as the SECM tip. In this method, except for active HRP micropatterns predesigned other regions on a HRP-immobilized substrate were deactivated by OH, generated at the tip held at ,1.7,V in 1.0,mol/L KCl containing 2.0×10,3 mol/L benzoquinone (BQ) (pH,8.0). The feedback mode of SECM with a tip potential of ,0.2,V was used to characterize the active HRP micropatterns in 1.0,mol/L KCl containing 2.0×10,3 mol/L BQ and 2.0×10,3 mol/L H2O2. [source] Complex Formation in the Region of Metal Hydrolysis and M(OH)2 Precipitation.ELECTROANALYSIS, Issue 7 2006(AMPSO)x, (OH)y, (OH)y Systems, A Glass Electrode Potentiometric, Polarographic Study of Cd Abstract The interaction between cadmium or zinc and AMPSO was investigated by DCP and GEP, at fixed total ligand to total metal concentration ratios and various pH values, at 25.0,°C and 0.1,M KNO3 ionic strength. For Cd,(AMPSO)x,(OH)y system, CdL and CdL(OH) species, were identified, with stability constants values set to (as log,,): 2.1±0.1 and 6.2±0.2, respectively. For Zn,(AMPSO)x,(OH)y system, the proposed final model with stability constants set to (as log,,) is: ZnL=2.5±0.1 and ZnL(OH)2=12.9±0.2. For both systems, the fact that AMPSO deprotonation occurs in the metal hydrolysis and M(OH)2 precipitation and the complexes formed are not too strong added a real challenge to data interpretation. [source] Evaluation of carrier ampholyte-based capillary electrophoresis for separation of peptides and peptide mimetics,ELECTROPHORESIS, Issue 18 2008an Koval Abstract Carrier ampholyte-based capillary electrophoresis (CABCE) has recently been introduced as an alternative to CE (CZE) in the classical buffers. In this study, isoelectric BGEs were obtained by fractionation of Servalyt pH 4,9 carrier ampholytes to cuts of typical width of 0.2 pH unit. CABCE feasibility was examined on a series of insect oostatic peptides, i.e. proline-rich di- to decapeptides, and phosphinic pseudopeptides , tetrapeptide mimetics synthesized as a mixture of four diastereomers having the ,P(O)(OH),CH2, moiety embedded into the peptide backbone. With identical selectivity, the separation efficiency of CABCE proved to be as good as classical CE for the insect oostatic peptides and better for diastereomers of the phosphinic pseudopeptides. In addition, despite the numerous species present in the narrow pH cuts of carrier ampholytes, CABCE seems to be free of system zones that could hamper the analysis. Peak symmetry was good for moderately to low mobile peptides, whereas some peak distortion due to electromigration dispersion, was observed for short peptides of rather high mobility. [source] Glycoform characterization of erythropoietin combining glycan and intact protein analysis by capillary electrophoresis , electrospray , time-of-flight mass spectrometryELECTROPHORESIS, Issue 13 2006Elvira Balaguer Abstract Glycosylation of recombinant human erythropoietin (rHuEPO) is a post-translational process that alters biological activity, solubility and lifetime of the glycoprotein in blood, and strongly depends on the type of cell and the cell culture conditions. A fast and simple method providing extensive carbohydrate information about the glycans present in rHuEPO and other glycoproteins is needed in order to improve current methods in drug development or product quality control. Here, an improved method for intact rHuEPO glycoform characterization by CZE-ESI-TOF MS has been developed using a novel capillary coating and compared to a previous study. Both methods allow a fast separation in combination with accurate mass characterization of the single protein isoforms. The novel dynamic coating provides a separation at an EOF close to zero, enabling better separation. This results in an improved mass spectrometric resolution and the detection of minor isoforms. In order to assign an unequivocal carbohydrate composition to every intact glycoform, a CZE-ESI-MS separation method for enzymatically released underivatized N -glycans has been developed. The TOF,MS allows the correct identification of the glycans due to its high mass accuracy and resolution. Therefore, glycan modifications such as acetylation, oxidation, sulfation and even the exchange of OH by NH2 are successfully characterized. Information of the protein-backbone molecular mass has been combined with results from peptide analysis (revealing information about O -glycosylation) and from the glycan analysis, including the detection of as yet undescribed glycans containing four antennae and five sialic acids. This allows an unequivocal assignment of an overall glycosylation composition to the molecular masses obtained for the intact rHuEPO glycoforms. [source] Importance of the counterion in optimization of a borate electrolyte system for analyses of anions in samples with complex matrices performed by capillary zone electrophoresisELECTROPHORESIS, Issue 20 2004Ludmila K, ivánková Abstract Borate buffers are common background electrolytes for analyses of anions in capillary zone electrophoresis. Usually, sodium borate at a given pH is used and this specification seems to be sufficient for a successful analysis. In this paper, we show that free migration of OH - may deteriorate the analysis of a typical anionic analysis of clinical samples due to uncontrolled migration of OH - throughout the systems of analyzed zones and may damage the stacking of anionic analytes of interest. We have proven that the use of ammonium borate may remedy the situation where the presence of ammonium may selectively stop the free migration of OH - ions, slow down their effective mobility and bring their safe behavior resulting in reproducible stacking of clinically important anions. Results of real analyses of human serum samples confirmed the proposed method and proved that substitution of sodium for ammonium in borate buffers offers reliable analyses of clinical samples having chloride as the bulk component. The experimental results given in this paper are supported also by computer simulation, which can not only support the positive results but also show the dynamics of the separation that is otherwise hidden to any detection possibilities. [source] Antioxidant and antimutagenic effects of the crude foliar extract and the alkaloid brachycerine of Psychotria brachycerasENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 9 2007Naíla Cannes do Nascimento Abstract The monoterpene indole alkaloid brachycerine from Psychotria brachyceras has been shown to be induced by UV and to have in vitro antioxidant activity, indicating a possible protective role against the secondary effects of this radiation. In this work, we have studied the antioxidant properties of brachycerine and a crude foliar extract from P. brachyceras by using Saccharomyces cerevisiae strains proficient and deficient in antioxidant defenses. The mutagenic and antimutagenic potential of these substances were assayed in S.cerevisiae N123 strain in the presence and absence of H2O2. In addition, we tested the antioxidant capacity of brachycerine and a crude foliar extract from P. brachyceras on hydroxyl radicals (OH,) using the hypoxanthine/xanthine oxidase assay. The results show that brachycerine and the crude foliar extract of P. brachyceras have antioxidant and antimutagenic effects in yeast and probably this action is mainly due to the scavenging of OH, radicals. Environ. Mol. Mutagen., 2007. © 2007 Wiley-Liss, Inc. [source] Characteristic improvement of metal-contaminated sludge using mineralization technologyENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 1 2010Shao-Hua Hu Abstract This study focuses on improving crystalline characteristics of metal-contaminated sludge. The mineralization behavior of Cu/Al or Cu/Fe coexisting in solution is surveyed, and the characteristics of residue and suspension settling are discussed in the context of water content of residue and settling/specific filtration resistance of suspensions. Experimental data show that the hydrate of Cu4SO4(OH)6 forms during mineralization of copper sulfate solution when hydroxide ion concentration, reaction time, and temperature are not controlled appropriately. Mineral characteristics of the residue are usually poor when the Cu4SO4(OH)6 forms in Cu/Al or Cu/Fe solution. However, Cu4SO4(OH)6 can be further transformed into CuO with wet oxidation or ferrite method, respectively (i.e., mineralization treatment). Water reduction of the residue is from 96.8% to 72.8% in the Cu/Al case or 95.6% to 66.6% in the Cu/Fe case, and the mineralized residue volume is only 1/10 of the hydrate sediment. This is particularly beneficial for sludge disposal. © 2009 American Institute of Chemical Engineers Environ Prog, 2010 [source] Adsorbing colloid flotation for removal of metal ions in waters from base metal minesENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 1 2002H. Sabti Adsorbing Colloid Flotation (ACF) has been shown in laboratory experiments to be effective for the removal of heavy metals (Zn, Cu, Cd and Pb) from dilute solutions. Sodium dodecyl sulphate (SDS) and sodium oleate (NaOl) were used as surfactants in single or mixed form, with Fe(OH)3 as a flocculant for colloid formation. These reagents worked best for zinc and copper ions for a feed concentration of 50 parts per million (ppm). The removal of lead improved significantly by the use of Fe(OH)3 and NaLS (Sodium lauryl sulphate), while the best removal of cadmium was achieved by the use of Al(OH)3 and HTMABr (hexadecyltrimethylammonium bromide). Flotation experiments were conducted with feed concentrations of 50 and 500 parts per billion (ppb) and 50 ppm (parts per million). The experimental results showed that the residual concentration of metal ions decreased significantly with the decrease in the feed concentration. This could be the effect of excessive (much more than stoichiometric ratio) amounts of surfactant and flocculant, compared to the feed concentrations, required in the effective flotation of dilute feed solutions. The surfactant concentration and feed pH had the largest effects on the process, as observed in the case of cadmium removal. This can be attributed to the flocformation and flotation tendencies of the colloid-metal complexes at various solution pH and surfactant concentrations. The ACF method was applied to a number of natural drainage solutions from the metal mines at Te Aroha, New Zealand, and the experimental results demonstrate that significant removal is achieved for most of the heavy metals. [source] Bioaccumulation and ROS generation in liver of freshwater fish, goldfish Carassius auratus under HC Orange No. 1 exposureENVIRONMENTAL TOXICOLOGY, Issue 3 2007Yuanyuan Sun Abstract HC Orange No. 1 (CAS No. 54381-08-7, 2-nitro-4,-hydroxydiphenylamine) is used as a color additive in hair dyes. In this study, laboratory experiment was carried out to determine HC Orange No. 1 bioaccumulation and oxidative stress in the liver of freshwater fish, goldfish Carassius auratus. Fish were exposed to different concentrations (0.05, 0.1, 0.2, 0.5, and 1.0 mg/L) of HC Orange No. 1 for 10 days, with one group assigned as control. The accumulation of HC Orange No. 1 in liver increased with the exposure concentration (R2 = 0.94). A secondary spin trapping technique was used followed by electron paramagnetic resonance (EPR) analysis to study the reactive oxygen species (ROS) production. On the basis of the hyperfine splitting constants and shape of the EPR spectrum, the ROS generated in fish liver after exposure was identified as hydroxyl radical (,OH). There is a good correlation between the exposure concentrations and ,OH generation (R2 = 0.92). The ,OH signal intensity of the EPR spectrum showed a significant increase (P < 0.05) when the HC Orange No. 1 concentration was 1.0 mg/L, compared with that of the control. A good positive relationship (R2 = 0.95) was found between the ,OH formation and accumulation level of HC Orange No. 1 in liver. The changes of the activities of catalase (CAT), superoxide dismutase (SOD), glutathione S -transferase (GST), and contents of reduced glutathione (GSH) were also detected. These observations indicated a possible mechanism of oxidative stress induced by HC Orange No. 1 on fish. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 256,263, 2007. [source] Comparative hepatic activity of xenobiotic-metabolizing enzymes and concentrations of organohalogens and their hydroxylated analogues in captive greenland sledge dogs (Canis familiaris),ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2009Jonathan Verreault Abstract A captive study was performed with Greenland sledge dogs (Canis familiaris) fed a naturally organohalogen-contaminated diet (Greenland minke whale [Balaenoptera acutorostrata] blubber; exposed group) or a control diet (pork fat; control group). The catalytic activity of major xenobiotic-metabolizing phase I and II hepatic microsomal enzymes was assessed. Relative to control dogs, ethoxyresorufin- O -deethylase (EROD) activity in exposed dogs was twofold higher (p = 0.001). Testosterone hydroxylation yielded 6,- and 16,-hydroxy (OH) testosterone and androstenedione, with higher rates of production (23,27%; p , 0.03) in the exposed individuals. In the exposed dogs, epoxide hydrolase (EH) activity was 31% higher (p = 0.02) relative to the control dogs, whereas uridine diphosphoglucuronosyl transferase (UDPGT) activity was not different (p = 0.62). When the exposed and control dogs were combined, the summed (,) plasma concentrations of OH-polychlorinated biphenyl (PCB) congeners were predicted by plasma ,PCB concentrations and EROD activity (p , 0.04), whereas testosterone hydroxylase, EH, and UDPGT activities were not significant predictors of these concentrations. Consistent results were found for individual OH-PCB congeners and their theoretical precursor PCBs (e.g., 4-OH-CB-187 and CB-183, and 4-OH-CB-146 and CB-146) and for EROD activity. No association was found between ,OH,polybrominated diphenyl ether (PBDE) and ,PBDE plasma concentrations, or between potential precursor-metabolite pairs, and the enzyme activities. The present results suggest that liver microsomal EROD activity and plasma PCB concentrations have a greater (e.g., relative to EH activity) predictive power for the occurrence of plasma OH-PCB residues in sledge dogs. These results also suggest that plasma OH-PBDEs likely are not products of cytochrome P450-mediated transformation but, rather, are accumulated via the diet. [source] Developmental toxicity in zebrafish (Danio rerio) embryos after exposure to manufactured nanomaterials: Buckminsterfullerene aggregates (nC60) and fullerolENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2007Xiaoshan Zhu Abstract The present paper summarizes, to our knowledge, the first study regarding the developmental toxicity of stable buck-minsterfullerene aggregates suspended in water (nC60) using zebrafish (Danio rerio) as a vertebrate model. Zebrafish embryo survival, hatching rate, heartbeat, and pericardial edema were noted and described within 96 h of exposure. Fullerol (a hydroxylated C60 derivative, C60(OH)16,18) at 50 mg/L did not exert toxicity to zebrafish embryos. In contrast, nC60 at 1.5 mg/L delayed zebrafish embryo and larval development, decreased survival and hatching rates, and caused pericardial edema. Toxicity was mitigated by adding an antioxidant (glutathione), which suggests that a free radical,induced mechanism or another form of oxidative stress played a role in developmental toxicity. [source] Organohalogen contaminants and reproductive hormones in incubating glaucous gulls (Larus hyperboreus) from the Norwegian ArcticENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2006Jonathan Verreault Abstract Organohalogen contaminants detected globally in avian wildlife, including populations from the Arctic, have been related to various reproductive hormone potencies, and altered hormonal balance and functions. Besides legacy organochlorine (OC) substances, that is, polychlorinated biphenyls (PCBs) and OC pesticides and by-products, endocrine-disruptive properties have been defined for chemicals of new and emerging environmental concern, such as polybrominated diphenyl ethers (PBDEs) and metabolically derived products like methylsulfonyl (MeSO2)- and hydroxyl (OH)-PCBs. We investigated the relationships between plasma concentrations of selected legacy OCs, PBDEs, and MeSO2 - and OH-PCB metabolites and the circulating reproductive hormones testosterone (T), 17,-estradiol (E2), and progesterone (P4) in incubating male and female glaucous gulls (Larus hyperboreus) from the Norwegian Arctic. Principal component and regression analyses demonstrated that P4 levels in male glaucous gulls were associated positively with variations of sum (,) PCB, dichloro-diphenyl-trichloroethane (,DDT), chlordane (,CHL), and ,PBDE concentrations, which were the most recalcitrant organohalogens determined in glaucous gulls. No such relationship was found for female glaucous gulls as well as between concentrations of any of the selected organohalogens and levels of T for both sexes. The E2 was not detected in any plasma samples. Present results were highly suggestive that exposure to high organohalogen concentrations in glaucous gulls, particularly the most persistent compound classes, may have the potential to interfere with steroidogenesis and impinge on circulating P4 homeostasis. Because significant effects were found in males exclusively, it cannot be completely ruled out that male glaucous gulls are more sensitive than females to organohalogen-mediated alteration of P4 synthesis and breakdown. [source] A Geographic Information Systems,based, weights-of-evidence approach for diagnosing aquatic ecosystem impairmentENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2006Katherine E. Kapo Abstract A Geographic Information Systems,based, watershed-level assessment using Bayesian weights of evidence (WOE) and weighted logistic regression (WLR) provides a method to determine and compare potential environmental stressors in lotic ecosystems and to create predictive models of general or species-specific biological impairment across numerous spatial scales based on limited existing sample data. The WOE/WLR technique used in the present study is a data-driven, probabilistic approach conceptualized in epidemiological research and both developed for and currently used in minerals exploration. Extrapolation of this methodology to a case-study watershed assessment of the Great and Little Miami watersheds (OH, USA) using archival data yielded baseline results consistent with previous assessments. The method additionally produced a quantitative determination of physical and chemical watershed stressor associations with biological impairment and a predicted comparative probability (i.e., favorability) of biological impairment at a spatial resolution of 0.5 km2 over the watershed study region. Habitat stressors showed the greatest spatial association with biological impairment in low-order streams (on average, 56% of total spatial association), whereas water chemistry, particularly that of wastewater effluent, was associated most strongly with biological impairment in high-order reaches (on average, 79% of total spatial association, 28% of which was attributed to effluent). Significant potential stressors varied by land-use and stream order as well as by species. This WOE/WLR method provides a highly useful "tier 1" watershed risk assessment product through the integration of various existing data sources, and it produces a clear visual communication of areas favorable for biological impairment and a quantitative ranking of candidate stressors and associated uncertainty. [source] Gene expression in caged fish as a first-tier indicator of contaminant exposure in streamsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2005Aaron P. Roberts Abstract The development of sensitive, biologically based indicators of contaminant exposure (i.e., biomarkers) is an ongoing topic of research. These indicators have been proposed as a first-tier method of identifying contaminant exposure. The primary objective of this research was to implement a biomarker-based method of exposure assessment using caged fish and real-time reverse-transcriptase polymerase chain reaction (rtRT-PCR) measurements of gene expression. Primers were developed for the CYPIA, metallothionein, and vitellogenin genes in rainbow trout (Oncorhynchyus mykiss), cutbow trout (Oncorhynchyus clarkii × mykiss), and Atlantic salmon (Salmo salar). Each of these genes has been shown to respond specifically to planar aromatic compounds, heavy metals, and environmental estrogens, respectively. Juvenile fish were placed in cages and exposed in situ at reference and contaminated sites on the Cache la Poudre River (CO, USA), the Arkansas River (CO, USA), the St. John River (NB, Canada), and two urban creeks near Dayton (OH, USA). Quantitative gene expression was determined using rtRT-PCR. Biomarker expression profiles were obtained that demonstrated differences in CYP1A, metallothionein, and vitellogenin mRNA production unique to each site, indicating that specific types of compounds were bioavailable and present in sufficient concentrations to elicit transcriptional responses in the organism. These findings support the use of a biomarker-based approach to exposure identification and assessment. [source] | |||||||||||||||||||||||||||||||||||||||||||