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  • 1
    ISSN: 1435-0157
    Keywords: Key words New Zealand ; hydrochemistry ; groundwater quality ; metamorphic rocks ; unconsolidated sediments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Résumé Dans les aquifères alluviaux des bassins de Wakatipu et de Wanaka (Otago central, Nouvelle-Zélande), la composition chimique des eaux souterraines peut être résumée ainsi, en équivalents: Ca2+≫Mg2+≅Na+ 〉K+ pour les cations, et HCO3 –≫SO4 2-〉NO3 – et Cl– pour les anions. En équivalents, le rapport entre Ca2+ et HCO3 – est de l'ordre de 1; ces ions représentent plus de 80% des ions présents dans la solution. Cependant, une partie de ces eaux souterraines possède des teneurs plus élevées en Na+ et SO4 2-, ce qui traduit une origine différente. Les matériaux constituant les aquifères alluviaux de ces deux bassins proviennent de l'érosion et de l'altération des schistes métamorphiques d'Otago (schistes gris et verts). La calcite est un minéral accessoire présent pour moins de 5% aussi bien dans les schistes gris que dans les verts. La cartographie géologique des deux bassins montre que la dissolution de la calcite des schistes est le seul mécanisme possible pour donner à l'eau souterraine une composition chimique aussi constante et caractérisée par un rapport 1 entre Ca2+ et HCO3 –. L'eau souterraine possédant les plus fortes teneurs en Na+ et en SO4 2- est présente près des zones où affleurent les schistes; cette eau souterraine est une eau d'origine plus profonde et probablement plus ancienne, provenant du substratum. Les concentrations anormalement fortes en K+ dans le bassin de Wakatipu et les concentrations élevées en NO3 – dans celui de Wanaka ne peuvent pas être attribuées à une interaction avec les roches du substratum; de telles teneurs correspondent probablement à l'influence anthropique sur la composition de l'eau souterraine.
    Abstract: Resumen Las aguas subterráneas en los acuíferos aluviales de las cuencas de Wakatipu y Wanaka, en Central Otago, Nueva Zelanda, tienen una composición química de manera que, expresándolos en términos de en equivalentes, los iones se pueden ordenar como Ca2+≫Mg2+≅Na+〉K+ para los cationes, y HCO3 –≫SO4 2-〉NO3 –≅Cl–para los aniones. Ca2+ y HCO3 – presentan una equivalencia 1 : 1, y entre los dos suponen más del 80% de los iones en disolución. Sin embargo, algunas aguas subterráneas presentan cantidades mayores de Na+ y SO4 2-, lo que refleja una procedencia diferente. El material rocoso de los acuíferos aluviales en ambas cuencas procede de la erosión y la alteración del Esquisto de Otago (esquistos grises y verdes). La calcita es un mineral presente en ambos esquistos, aunque con proporciones menores del 5%. Los mapas geológicos de ambas cuencas indican que la disolución de calcita procedente de los esquistos es el único mecanismo probable para producir unas aguas subterráneas con una composición tan constante de carbonato cálcico. Aguas subterráneas con mayores contenidos de Na+ y SO4 2- tienen lugar en zonas donde los esquistos afloran en superficie, por lo que estas aguas son más profundas y más viejas y provienen de circulación profunda, por la base del acuífero. Valores anormalmente altos de K+ en la cuenca de Wakatipu y de NO3 – en la de Wanaka no pueden justificarse por la interacción con los materiales de la base del acuífero, por lo que estas concentraciones están probablemente influenciadas por fuentes antrópicas.
    Notes: Abstract  Groundwater in alluvial aquifers of the Wakatipu and Wanaka basins, Central Otago, New Zealand, has a composition expressed in equivalent units of Ca2+≫Mg2+≅Na+〉K+ for cations, and HCO3 –≫SO4 2-〉NO3 –≅Cl– for anions. Ca2+ and HCO3 – occur on a 1 : 1 equivalent basis and account for 〉80% of the ions in solution. However, some groundwater has increased proportions of Na+ and SO4 2-, reflecting a different source for this water. The rock material of the alluvial aquifers of both basins is derived from the erosion and weathering of metamorphic Otago Schist (grey and green schists). Calcite is an accessory mineral in both the grey and green schists at 〈5% of the rock. Geological mapping of both basins indicates that dissolution of calcite from the schist is the only likely mechanism for producing groundwater with such a constant composition dominated by Ca2+ and HCO3 – on a 1 : 1 equivalent basis. Groundwater with higher proportions of Na+ and SO4 2- occurs near areas where the schist crops out at the surface, and this groundwater represents deeper and possibly older water derived from basement fluids. Anomalously high K+ in the Wakatipu basin and high NO3 – concentrations in the Wanaka basin cannot be accounted for by interaction with basement lithologies, and these concentrations probably represent the influence of anthropogenic sources on groundwater composition.
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  • 2
    ISSN: 1573-5001
    Keywords: FKBP12 ; NMR detection ; sensitivity enhancement ; side chain–side chain hydrogen bonds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract We describe the direct observation of side chain–side chain hydrogen bonding interactions in proteins with sensitivity-enhanced NMR spectroscopy. Specifically, the remote correlation between the guanidinium nitrogen 15Nε of arginine 71, which serves as the hydrogen donor, and the acceptor carboxylate carbon 13CO2 γ of aspartate 100 in a 12 kDa protein, human FKBP12, is detected via the trans-hydrogen bond 3h J Nε CO2γ coupling by employing a novel HNCO-type experiment, soft CPD-HNCO. The 3h J Nε CO2γ coupling constant appears to be even smaller than the average value of backbone 3h J NC′ couplings, consistent with more extensive local dynamics in protein side chains. The identification of trans-hydrogen bond J-couplings between protein side chains should provide useful markers for monitoring hydrogen bonding interactions that contribute to the stability of protein folds, to alignments within enzyme active sites and to recognition events at macromolecular interfaces.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-5001
    Keywords: FKBP12 ; NMR detection ; sensitivity enhancement ; side chain–main chain hydrogen bonds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract We describe the direct observation of very weak side chain–main chain hydrogen bonding interactions in medium-size 13C/15N-labeled proteins with sensitivity-enhanced NMR spectroscopy. Specifically, the remote correlation between the hydrogen acceptor side chain carboxylate carbon 13CO2 δ of glutamate 54 and the hydrogen donor backbone amide 15N of methionine 49 in a 12 kDa protein, human FKBP12, is detected via the trans-hydrogen bond 3h J NCO2δ coupling by employing a novel sensitivity-enhanced HNCO-type experiment, CPD-HNCO. The 3h J NCO2δ coupling constant appears to be even smaller than the average value of backbone 3h J NC′ couplings, consistent with more extensive local dynamics in protein side chains.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 25 (1983), S. 1897-1904 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Hydrogen photoproduction from water in Scenedesmus cells requires removal of oxygen by a reagent in contact with the algae. Both deoxyhemoglobin and deoxymyoglobin stimulated hydrogen production by reversible absorption of oxygen. Their effectiveness was greatly increased when other oxygen-combining reagents were present in a separate chamber with deoxyhemoglobin and deoxymyoglobin serving as reversible oxygen transfer agents.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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