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Metallic Ions (metallic + ion)
Selected AbstractsConfiguration of Octahedral Metal Compounds , Equilibrium, Crystal and Molecular Structure of Nickel(II) Complexes of Linear N2O4, N4S2 or N6 Donors Set Atoms LigandsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2004Aminou Mohamadou Abstract Two new nickel(II) complexes of symmetric hexadentate mixed-ligand N,O [1,12-bis(2-pyridyl)-5,8-dioxa-2,11-diazadodecane (pydado)] and N,S [1,12-bis(2-pyridyl)-5,8-dithia-2,11-diazadodecane (pydadt)] donor atoms have been synthesised as perchlorate salts and characterised by X-ray crystallography and ligand-field spectroscopy. In both complexes the Ni2+ ion is hexacoordinate. The cation [Ni(pydado)]2+ is pseudo-octahedral with the two pyridyl groups in trans position; all Ni,N and Ni,O bond lengths are practically equivalent. In [Ni(pydadt)]2+ complex, however, the size of the thioether sulfur atoms imposes a C2v symmetry; the pyridyl groups and the sulfur atoms are in trans positions and all Ni,N bond lengths are equivalent. The comparison of these structures with those of octahedral cobalt, copper and zinc complexes with the same ligands shows that their configurations depend not only on the nature of the two central donor atoms of the ligand, but also on the nature of the metallic ion. In aqueous solution, the stability constants of the NiII chelates with these two ligands, determined by potentiometry, show the formation of [Ni(LH)]3+ and [NiL]2+ species in all cases. The chelating power of the pydadt ligand is slightly greater than that of pydado. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Application of a Carbon Paste Electrode Modified with a Schiff Base Ligand to Mercury Speciation in WaterELECTROANALYSIS, Issue 11 2005Montserrat Colilla Abstract A carbon paste electrode, modified with benzylbisthiosemicarbazone is used for mercury speciation in water samples. Mercury ion is selectively accumulated on the electrode surface at open circuit and its analysis was performed by cyclic voltammetry or square-wave voltammetry (SWV). A detection limit of 8,,g L,1 (3,) was found for 15,min of accumulation using SWV as measurement technique. The effect of several metallic ions and organic substances on voltammetric signal is examined. For speciation purposes, a ligand competition methodology between ligands in solution and electrode is used. Model mercury complexes are characterized as a function of their dissociation kinetics. The method was applied to mercury speciation in water samples from the Jarama River in Madrid. [source] Early Polarographic Studies on ProteinsELECTROANALYSIS, Issue 13-14 2004Michael Heyrovsky Abstract The first effects of proteins observed with the dropping mercury electrode were catalytic, due to evolution of hydrogen in weakly alkaline solutions. Catalytic lowering of hydrogen overvoltage in presence of cobalt ions, the so-called Brdicka reaction, became the main means for polarographic study of proteins. Apart from that, polarography has been used for following proteins in their adsorption on the electrode surface, in their anodic reaction with mercury at positive potentials, in reduction of the disulfidic bonds of their components, in their complexation with metallic ions in the solution, in electrode reactions of their prosthetic groups and in antigen-antibody interactions. Our review is limited to applications of the dropping mercury electrode. [source] Metals in human placenta: focus on the effects of cadmium on steroid hormones and leptin,JOURNAL OF APPLIED TOXICOLOGY, Issue 3 2010Sandra Stasenko Abstract Cadmium and other metallic ions can act as metalloestrogens and endocrine disruptors of reproductive tissues and fetal development in mammals, including humans. The detrimental effects occur with respect to the synthesis of both steroid and polypeptide hormones in the placenta. Leptin is produced by the trophoblast and may regulate fetal organogenesis and development. In human term placentas, concentrations of toxic metals and their effects on steroidogenesis were assessed in healthy parturients (109 non-smokers and 99 smokers) in relation to tobacco smoking. Trace elements (cadmium, lead, iron, zinc and copper) were analyzed in placentas using atomic absorption spectroscopy, and steroid hormones (progesterone and estradiol) were assayed in placental samples by an enzyme-immunometric method. Cadmium concentrations were doubled in placentas of smokers as compared with non-smokers, and placental lead and zinc concentrations increased significantly. Placental concentrations of iron, copper, progesterone and estradiol did not differ. In addition, human trophoblast cells were co-cultured with 0, 5, 10 or 20,,µm CdCl2 for 96,,h and leptin mRNA assessed by quantitative polymerase chain reaction. Leptin mRNA declined dose-responsively as a result of CdCl2 exposure. Collectively, the results confirm that human placental tissue offers a unique opportunity to biomonitor cadmium exposure in both the maternal and the internal fetal environments. In addition, the results strongly suggest that cadmium may cause a decline in placental leptin synthesis, as we have previously shown for placental progesterone production. This may constitute further evidence of the endocrine-disrupting effects of cadmium, as a constituent of tobacco smoke, on reproduction in women. Copyright © 2009 John Wiley & Sons, Ltd. [source] Purification and partial characterization of glutathione S -transferase from insecticide-resistant field populations of Liposcelis paeta Pearman (Psocoptera: Liposcelididae)ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 2 2009Shuang Wu Abstract Enzymes that possess glutathione S-transferase (GST) activity were purified to homogeneity by glutathione-agarose affinity chromatography from three field populations of Liposcelis paeta (Pearman). These populations were collected from Nanyang city of Henan Province (NY), Wuzhou (WZ) and Hezhou (HZ) cities of Guangxi Province, China, and had different susceptibilities to dichlorvos [LC50s of the NY (281.48,mg/m2), the WZ (285.07,mg/m2), and the HZ (243.52,mg/m2), respectively]. The specific activities of purified enzymes from these three populations increased 32.24-, 99.81-, and 42.52-fold, respectively. Kinetic analyses showed that the catalytic activity of purified GST from NY population towards GSH was much higher than the others, while WZ population reached the highest in V. SDS,polyacrylamide electrophoresis revealed that the purified GST had two subunits with a molecular mass of 23.31 and 20.43,kDa for NY, 53.14 and 20.13,kDa for WZ, and 50.79 and 19.42,kDa for HZ, respectively. The in vitro inhibition studies of GSTs indicated that three kinds of insecticides (chlorpyrifos, carbosulfan, and cypermethrin) and five metallic ions (Zn2+, Ba2+, Ca2+, Hg2+, Mn2+, and Mg2+) all possessed inhibitory effects on purified GST, and ethacrynic acid (EA, a specific inhibitor of GST) expressed inhibitory effects. In the bioassay, three populations of L. paeta had different susceptibilities to different insecticides, even after they were reared on diets consisting of 25% EA. The GST activities of L. paeta from different areas also showed different temperature and pH stabilities. The differences in GST among the three populations may be attributed partially to the differences in control practices for psocids between Henan and Guangxi Provinces. © 2009 Wiley Periodicals, Inc. [source] | ||||||||||