Metal Binding To Macromolecules: Bacterial Polysaccharides For Heavy Metal Capture And Rhenium Complexes As Anticancer Agents
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Type of WorkText
ProgramMaster of Science
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The major macromolecules of life are proteins, polysaccharides, lipids, and nucleic acids. Some of the functional groups present in these molecules provide particularly useful sites for binding of metals. This work explores ways that metal binding to these groups in polysaccharides and nucleic acids can be potentially used for two distinct yet important purposes: removal of environmental pollutants and anti-cancer treatment. Polysaccharides are long chain polymers of monosaccharide units linked together by glycosidic bonds. Polysaccharides contain ionizable functional groups such as carboxylic, phosphoric, amino and hydroxyl groups which makes them an excellent metal binding agent. This property can be used in the field of bioremediation. Bioremediation is the process of consumption and breakdown of environmental pollutants especially metal cations and their complexes using bacterial biopolymers. One goal of this thesis is to study the metal binding capacity of capsular polysaccharides of two serogroups of Neisseria meningitidis, serogroup B (containing repeating units of the negatively-charged sialic acid) and serogroup W (containing repeating units of the neutral sugar galactose and negatively-charged sialic acid) with Pb2+ and Cu2+ cations. Our initial approach was to produce a capsular heteropolysaccharide of Neisseria meningitidis serogroup W using a chemoenzymatic method on a solid support. Based on initial studies showing metal binding with resin without polysaccharide, we used the commercially available polysaccharide for our metal binding studies until a more suitable solid support is determined. Colominic acid (structurally equivalent to N. meningitidis B polysaccharide) was found to bind well to both Pb2+ and Cu2+ cations. The N. meningitidis W polysaccharide was also found to bind with Pb2+ ion. The other goal of this thesis was to determine the DNA-binding modes of a series (15 total) of organorhenium sulfonate and carboxylate complexes from Mandal's Synthesis using viscosity. The organorhenium compounds were all found to bind to DNA through intercalation. However, of the 15 compounds, 5 of these compounds bound the best with observed changes in viscosity similar to the known intercalating agent ethidium bromide (EtBr). The polysaccharide metal-binding studies are the foundation of future planned studies to model and chemoenzymatically synthesize new derivatives of these polysaccharides. Future work for DNA binding will also focus on testing new derivatives of organorhenium complexes.