The stability of hydrogen peroxide (H2O2) is a critical factor for the brightening of mechanical pulps. Inorganic ions, including Fe, Mn and Cu catalytically decompose H2O2. These troublesome metals promote the rapid transformation of H2O2 to nonselective hydroxyl radicals that degrade the cellulose fibres and decrease yields. / The interaction of aqueous metal•complexes with magnesium metal (Mg°) or bimetallic mixtures of magnesium with either palladium (Pd°/Mg°) or silver (Ag°/Mg°) were optimized to remove metals (Mn, Cu and Fe) from solution with concomitant release of the complexing reagent. The analyte metals were removed by both cementation on the surfaces of the excess Mg° and by precipitation as hydroxides. Overall, the reactions were rapid (3 or 10 min) and very efficient. The accelerators (Ag or Pd) were deposited on the surfaces of the Mg°. In a separate study, the excess of Mg° could be reused to mediate more metals removal without apparent loss of reactivity. Among the other iminodiacetate analogs (CDTA, MEDTA, EGTA, HEDTA, DPTA and MTBE), the EGTA and HEDTA proved to be possible substitutes for both efficient metal removal of Mn, Cu and Fe from solution and efficient release of chelating reagent. The measurement of particle size, performed by laser granulometry, demonstrated that smaller particles of precipitate were generated from metal-EDTA complexes by reaction with NaOH than by reaction with Pd°/Mg° bimetallic mixture. If the suspensions of particles were analyzed in the absence of ultrasound, the particles became aggregated into large flocs (up to 150 mum3 ). The reactivity of the bimetallic mixtures was exploited to remove Cu, Mn, Fe, Zn and Al that had been initially chelated with EDTA or DTPA from a thermomechanical pulp (TMP). After 15 min, the metals had been removed efficiently with the bimetallic mixtures. The EDTA released from the TMP filtrate could be recycled efficiently for a total of three cycles. On the other hand, the DTPA was not released as efficiently. Measurements of turbidity and chemical oxygen demand (COD) indicated no appreciable difference between the pulp samples with either chelating reagent. Residual H2O2 and ISO brightness measurements indicated no apparent differences among pulps that had been treated wi

Thesis (PhD) -- McMaster University, 1997. / Also available via World Wide Web.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaf 140). Also available via the Internet.

Thesis (Ph. D.)--University of Missouri--Columbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves: 157-166). Also available on the Internet.

Thesis (Ph.D.)--Baylor University, 2009. / Includes bibliographical references (p. 233-237).

Os minerais essenciais participam de várias funções vitais do organismo, suas deficiências contribuem de maneira significante para a morbidade e mortalidade na infância, especialmente nos países em desenvolvimento, sendo consideradas como problema de saúde pública em todo o mundo. Minerais apresentados na forma de complexos orgânicos têm sido propostos para correção destas deficiências por apresentarem maior biodisponibilidade, quando comparados aos equivalentes sais inorgânicos. Os minerais cobre, ferro, manganês e zinco são essenciais aos organismos vivos (humano e animal), a manutenção de seus níveis de acordo com as necessidade fisiológicas contribuem para a manutenção da saúde, resultando em benefícios econômicos. No presente trabalho foi realizada a preparação e caracterização físico-química de complexos dos minerais Cobre (Cu), Ferro (Fe), Manganês (Mn) e Zinco (Zn) com hidrolisados parciais de proteína de soja. As hidrólises utilizando as enzimas Aranzime e Alcalase foram mais eficientes que as demais hidrólises enzimáticas ou ácidas, entretanto somente a Alcalase foi aprovada para a manufatura de produtos alimentares de consumo humano. A coordenação entre os metais e o hidrolisado pode ser confirmada por pelo deslocamento das bandas ?NH2, ?aCOO- e ?sCOO-. Os complexos obtidos de cobre, ferro, manganês e zinco, posuem em sua composição os respectivos percentuais de ligação: 2,21%, 1,22%, 12,38% e 10,40%. / The essential minerals participate in many vital functions in the organism, its deficiencies contribute in significant way for the morbidity and mortality in the childhood, especially in developing countries, being considered as public health problem in the whole world. Minerals presented in the form of organics complexes have been considered a good choice for these deficiencies, because it presents greater bioavailability when compared with the equivalents inorganic salts. The minerals copper, iron, manganese and zinc are essential to the organisms (human and animal), its physiological levels in accordance with the necessity contribute for the health maintence, resulting in economical benefits. In the present work it was carried through preparation and physical and chemical characterization of mineral complexes of Copper (Cu), Iron (Fe), Manganese (Mn) and Zinc (Zn) with partial hydrolysates of soy protein. The hydrolyses using the Aranzime and Alcalase enzymes had been more efficient than other enzymatic or acid hydrolyses, however only the Alcalase enzyme is approved for the manufacture of alimentary products for human consumption. Coordination between metals and the hydrolysate can be confirmed by the displacement of the ?NH2, ?aCOO- and ?sCOO- bands. The gotten copper, iron, manganese and zinc complexes, had the respective percentages of metal in its composition: 2,21%, 1,22%, 12,38% e 10,40%.

A series of 31 sulfur-nitrogen donor ligands and 64 metal(II) complexes have been investigated. The thiomethylated aniline ligands 2–(methylthiomethyl)aniline 2MT and 2–(methylthio)aniline 2MA were synthesized with their substituted derivatives (-Me, -MeO, -Cl, -Br, -NO2) to serve as chelating agents. These ligands behave as bidentate ligands with SN donor group with Co(II), Ni(II) and Cu(II). The Co(II) and Ni(II) complexes have the ML2Cl2 molecular formula while the Cu(II) complexes formed with MLCl2 stoichiometry where L is the bidentate ligand. The ligands and their metal(II) complexes have been characterized by elemental analysis and with spectroscopic techniques. The trend observed in the NMR spectra and IR frequencies of the thiomethylated compounds shows there is a significant difference between the 2MT and 2MA series as a result of sulfur lone pairs extending the conjugation of the aromatic ring in the case of the latter. The effect of the position and electronic nature of ring substituent on the NMR shifts of the amine protons is discussed. The 6- and 5-membered chelate complexes formed by the 2MT and 2MA ligands respectively do not show significant diversity in their spectroscopic properties. From the elemental analysis for the Co(II) and Ni(II) complexes, their compositions reveal 1:2 M:L stoichiometry with 2 chlorine atoms from the respective metal salts. In addition, the spectroscopic data are largely indicative of tetragonally distorted structures for these solid complexes. The X-ray crystallography data reveal the Cu(II) complexes exist as square pyramidal dimers and with long Cu–Cl equitorial bonds fit into the tetragonally distorted octahedral structure. The electrolytic nature of Co(II) and Cu(II) complexes in DMF were found to be similar, they behave as non electrolytes in contrast to Ni(II) complexes which are 1:1 electrolytes. The electronic spectra of these metal(II) complexes were found to be different for both their solid forms and in solutions of DMF and DMSO and this has been discussed. The thiomethylated aniline ligands possess the amine and thioether groups which are present in many known biologically active compounds, hence the biological activity of the ligands and their metal complexes were tested against three strains of bacteria and one fungus. The methoxy-substituted derivatives were found to possess better inhibitory activity and this was similarly reflected in the metal(II) complexes. The activity of the complexes can be said to be in the order, Cu(II) > Co(II) > Ni(II). The Schiff-base derivatives were prepared from the ligands and para-methoxysalicylaldehyde and their Cu(II) complexes were synthesized in order to determine their biological activity. The Schiff-base ligands were found to be less active than their parent ligands. The Cu(II) complexes are not soluble in water, DMSO or DMF, as a result and could not be evaluated for their biological activity. Based on the good results from the antimicrobial evaluation, the antiplasmodial activity of some of the Co(II), Ni(II) and Cu(II) complexes of the thiomethylated ligands against Plasmodium falciparum (FCR-3) was determined. At 50 μM concentration level, the Cu(II) complexes show activity equal or better than the prophylactic chloroquine. The Cu(II) complexes with the methoxy-substituted demonstrated exceptional activity but their Co(II) and Ni(II) analogues did not show any activity. The cytotoxicity of the active Cu(II) complexes at 50 μM concentration was determined against the breast cancer cell line (MDA-MB-231). The compounds destroyed the cancer cell in the range of 28–40%, thus showing their preferred activity against the parasitic cell instead of the cancer cell. The selectivity demonstrated by these compounds have shown them to be potential antimalarial agents and this could be further investigated.

Lanthanide chelates are effective agents for improving contrast in MR images. Optimizing the relaxation of inner sphere water molecules is a common focus of research in this field. However, the efforts to design an optimal contrast agent have commonly over-looked the relationship of water position and water exchange kinetics. This work explores structural conformation, the impact of very fast water exchange kinetics on hydration, and differing tumbling rates for regioisomers of a number of lanthanide chelates. We have grown crystals of LnDOTMA and obtained structural data by X-ray diffraction that provide a picture of the chelate during water exchange and demonstrate that chelate conformation is associated with water position. We observe increased population of the major isomer with increased water exchange rates in variable temperature 1H NMR studies of HoDOTMA. This suggests that water position and water exchange rates are linked. We therefore recommend that accurate water exchange data be included in the application of the SBM equations when interpreting experimental data. As further support of this recommendation, we measured water exchange kinetics with 17O NMR for the rigid GdNB-DOTMA chelates. These results were used in the fitting of 1H NMRD profiles to establish tumbling parameters. Similar results were also observed in the less rigid GdNB-DOTA, establishing the first identification of regioisomers in these chelates and their biphenyl derivatives. Binding studies of GdBP-DOTA indicate that the side isomer is a more effective agent, but it is the minor species in solution. Our work herein shows that predicting efficacy of contrast agents with SBM equations requires a more complete consideration of chelate hydration (q/r6).

The primary objective of this research was to determine if changes in iron availability influence the periodicity of blue-green algal growth. A secondary goal was to resolve how iron availability was related to events such as calcite (calcium carbonate) precipitation and sediment nutrient release. The biogeochemical regulation of blue-green algal succession was studied in three eutrophic hardwater lakes located upon the Thompson Plateau in south-central British Columbia. The experimental approaches included iri situ bottle and limnocorral experiments, sediment core analysis, monitoring of seasonal changes in water chemistry, and whole-lake manipulation by hypolimnetic aeration, or calcium hydroxide addition. Growth and primary production bioassays were used to evaluate iron availability. Microbial chelators were isolated from algal cultures and lake water, quantified by a chelation assay, and used to determine their in situ effects on algal productivity and bacterial heterotrophy. Microbes were able to regulate the bioavailability of iron. Algal siderophore isolates were rapidly assimilated in lake water and they were highly specific for iron chelation. Moreover, chelator concentrations in Black Lake usually exceeded the dissolved iron concentration. Algae excreted chelators that could suppress growth of some other species of algae by 90%, enhance the primary production of some other algal species by 30%, or suppress the heterotrophic activity of bacteria by 14-98%. The degree of iron limitation varied greatly during the summer. In Black Lake, iron limitation was more than ten-fold more intense in early summer than in late summer. Dense blooms of blue-green algae occurred in Black Lake only after the iron content of the lake increased from 20 to more than 100 ug/L. An increase in iron concentration in the water column of the three lakes was caused by a midsummer sediment release of iron. Although sediment pyrite formation converted available iron into refractory iron in both Chain and Frisken lakes, the degree of iron limitation varied greatly among the lakes. Unlike in Black Lake, the algae in Chain Lake were not limited by iron availability. Phosphorus solubility was a good index of iron availability. Black and Frisken lakes had too little iron for iron phosphate to precipitate, but the higher iron concentration in Chain Lake regulated phosphorus solubility. The differences among lakes was primarily a function of external iron loading, not sediment iron release. Chain Lake received 10³ more iron per m² than Frisken or Black lakes. Carbonate equilibria integrated the microbial responses to iron enrichment. When iron availability was increased in the epilimnion of Black Lake, algal productivity was enhanced which resulted in an increase in pH and the coprecipitation of more calcite and phosphorus than in control treatments. The precipitation of calcite could sediment as much as 90% of the algae and 97% of the phosphorus from the epilimnion. The hypolimnia of the iron-enriched limnocorrals had the lowest pH and highest dissolution of precipitated phosphorus. Three reactions, iron chelation, sediment iron release, and calcite precipitation, can regulate much of the periodicity of blue-green algal growth in hardwater lakes. / Science, Faculty of / Zoology, Department of / Graduate

Orientador: Sônia Maria Alves Bueno / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-18T14:28:20Z (GMT). No. of bitstreams: 1 Tsai_YuanMing_M.pdf: 3416327 bytes, checksum: d37231cf12f3af7bab5f7826907d5180 (MD5) Previous issue date: 2011 / Resumo: O presente trabalho teve como objetivo principal, o estudo comparativo dos agentes quelantes CM-Asp e IDA no processo da purificação de IgG humana por cromatografia de afinidade por íon metálico cobalto imobilizado em diferentes sistemas tamponantes na presença e ausência do sal NaCl. Observou-se, para todos os sistemas tamponantes estudados, a adição de sal foi desfavorável em termos de capacidade e seletividade de adsorção de IgG para ambos os agentes quelantes. De acordo com eletroforeses SDS-PAGE e análises nefelométricas, os melhores resultados foram observados em presença de Tris-HCl 25 mmol/L, pH 7,0 para o quelato CM-Asp-Co2+ e fosfato de sódio 25 mmol/L com imidazol 2 mmol/L, pH 7,0 para o quelato IDA-Co2+, obtendo-se fatores de purificação de 8,1 e 4,1 e pureza de 100% e 96%, respectivamente. Foram determinadas as curvas de ruptura por meio de experimentos cromatográficos realizados a diferentes diluições do soro humano, os resultados obtidos evidenciaram uma maior eficiência em termos da capacidade de adsorção nas diluições a 5 e 10 vezes (0,89 e 1,03 mg de proteína total/mL gel) comparado a soro diluído a 2,5 vezes (0,40 mg de proteína total/mL gel), tendo estes demonstrado comportamentos similares ao apresentado em etapa cromatográfica. Os dados de adsorção de IgG foram bem representados pelo modelo de Langmuir-Freundlich, a 25ºC, fornecendo valor de Qm igual a 94,44 mg IgG/mL gel e constante de dissociação de 8,18 x 10-5 mol/L, ordem de grandeza característica para ligantes pseudobioespecíficos / Abstract: In this work, we targeted the comparative study between chelating ligands agarose-CM-Asp and agarose-IDA in the purification of human IgG by Immobilized Metal-ion Affinity Chromatography (IMAC) with immobilized cobalt ion in different buffering systems in the presence or absence of salt. For all buffering systems the addition of salt was unfavorable in terms of adsorption capacity of IgG for both chelating ligands. The best results were obtained in the absence of salt. According to SDS-PAGE electrophoresis and nephelometric analysis, the best conditions observed were Tris-HCl 25 mmol/L, pH 7,0 for the agarose-CM-Asp and sodium phosphate 25 mmol/L with imidazole 2 mmol/L for the agarose-IDA (purification factor of 8,1 and 4,1 and purity of 100% and 96%, respectively). Chromatographic experiments were carried out with different dilutions of human serum to determine the breakthrough curves. The results showed a higher efficiency in terms of adsorption capacity at dilutions of 5 and 10 times (0.89 and 1.03 mg of protein Total / mL gel) compared to serum diluted 2.5 times (0.40 mg total protein / mL gel), these results had similar behaviors as those showed in the chomatografic stage. The adsorption data of IgG at 25ºC were well represented by Langmuir-Freundlich model. Values of Qm equal 94,44 mg of IgG/mL gel and dissociation constant of 8,18 x 10-5 mol/L, characteristic magnitude of pseudospecific ligands / Mestrado / Desenvolvimento de Processos Biotecnologicos / Mestre em Engenharia Química