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Studies of the structure and the stability of complexes formed by metal ions and D-galacturonic acid

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Description: Sphagnum Peat Moss has the ability to act as a cation exchanger. Various sites within this plant have been proposed as the exchange site, including the cell wall. The cell walls of these plants are mainly constructed from pectins, such as polygalacturonic acid, which can make up 30% of the plants dry weight. I have determined stability constants between the monomer D-galacturonic acid and various divalent metal ions, as a model system for metal ion-Sphagnum Peat Moss interactions. The measured effective stability constants ranged from 1 $1\over 2$ log units for the group IIB metals, to $\sim$2 log units for Cu$\sp{+2}$ and Pb$\sp{+2}$ ions. These values were then broken down further, so as to determine stability values for the individual tautomers of D-galacturonic acid. Investigations into the aqueous binding site of these metal ions was then conducted. Various methods were employed to determine the binding site including ir, NMR (including both diamagnetic shifts and the use of paramagnetic ions as resonance line broadening agents), and solid state NMR. The results indicated that the uronate ion chelates metal ions through the carboxylate and either ring ether oxygen or the C-4 hydroxy group.
Language: English
Format: Degree Work