Browsing by Author "Koch, K"

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    DNA-mediated biomineralization of a new planar Pt-complex
    (2006) Klump, H H; Koch, K; Lin, C T
    The crystal growth morphology of a coordination complex of Pt(II) that crystallizes from solution can be controlled by using a second molecular species such as peptides or other organic compounds. Examples of crystal growth controlled by nucleic acids are few. In this article we describe the use of branched three-way junction (3WJ) DNA to influence the crystal growth of a planar platinum compound, cis-[(2, 2′-bipyridyl)N,N-di(2-hydroxyethyl)-N′-benzoylthioureatoplatinum(II)]chloride. Platinum complexes with extended planar aromatic residues are capable of stacking in the absence as well as in the presence of linear DNA double helices. This feature is based on the interaction of the compound with DNA through intercalation, resulting in the prevention of binding of DNA polymerase. Microscopic one-dimensional crystals were observed under these conditions. In the presence of the branched 3WJ DNA, however, additional nucleation sites are present, resulting in extended crystal growth of unique Pt compounds. At least two different crystal modifications were observed using transmission electron microscopy.
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    The solvent extraction of CU (II) from chloride solutions with certain non-chelating nitrogen donor ligands
    (1986) Soldenhoff, Karin; Preston, J S; Orren, M J; Koch, K
    The extraction of copper from chloride solutions with some aliphatic oximes as well as some pyridine carboxylates was studied and the complexes formed in the organic phase identified. The association of octanal oxime in toluene was taken into account in the extraction studies and formation constants for dimers and trimers obtained. Copper (II), Nickel (II) and Cobalt (II) are extracted by a solvating mechanism in which only the neutral MCl2 species is extractable. This reaction is largely independent of pH. Studies were also carried out on the use of the commercial reagent ACORGA CLX-20, for the selective extraction of copper from a synthetic solution simulating leach liquors obtained by ferric chloride leaching of complex sulphide ores. Results show that separation of copper from iron is dependent on the amount of acid and chloride present in the aqueous phase.