First Faculty Mentor

Dr. Edwin G. Olmstead

Department

Chemistry

Award

3rd Empirical Undergraduate

Classification

Undergraduate (Senior)

Description

Siderophores are molecules produced by bacteria which bind iron so strongly they are capable of extracting iron from its insoluble forms in the environment. Ferrioxamine B is the iron(III) complex of desferrioxamine B, a hexadentate siderophore with three hydroxamic acid subunits. It is secreted by various species of Streptomyces and Nocardia bacteria to acquire iron. Given the extraordinary stability of ferrioximine B, one topic of interest is how microbes engineer the release of iron from the complex. One possible strategy proposed in the literature is the formation of ternary complexes. Ternary complexes are molecular combinations formed from three components: iron, siderophore, and a competing iron binding molecule. Ternary complex formation is hypothesized to enhance the iron exchange process between the siderophore and an iron transport molecule or receptor site within the organism. The competing ligand studied in this reaction, 8-hydroxyquinoline-5-sulfonate, is a bidentate chelator. The 8-hydroxyquinoline-5- sulfonate ligand is also biologically relevant as the quinoline functional group is present in flavin mononucleotide, a physiological reductant shown to be capable of reducing ferrixomine B in vitro, and in the siderophore quinolobactin. We investigated the reaction of 8-hydroxyquinoline-5-sulfonate with ferrioxamine B in aqueous solution using potentiometry and UV-VIS spectroscopy. By varying the pH and the concentration of 8-hydroxyquinoline-5-sulfonate, we initiated shifts in the equilibrium position while monitoring changes in the reaction component concentrations. Through analysis of the potentiometric and spectrophotometric data, we have determined the products and equilibrium constants associated with this reaction.

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Equilibrium Studies of the Iron Exchange Reaction of Ferrioxamine B with 8-hydroxyquinoline-5-sulfonate

Siderophores are molecules produced by bacteria which bind iron so strongly they are capable of extracting iron from its insoluble forms in the environment. Ferrioxamine B is the iron(III) complex of desferrioxamine B, a hexadentate siderophore with three hydroxamic acid subunits. It is secreted by various species of Streptomyces and Nocardia bacteria to acquire iron. Given the extraordinary stability of ferrioximine B, one topic of interest is how microbes engineer the release of iron from the complex. One possible strategy proposed in the literature is the formation of ternary complexes. Ternary complexes are molecular combinations formed from three components: iron, siderophore, and a competing iron binding molecule. Ternary complex formation is hypothesized to enhance the iron exchange process between the siderophore and an iron transport molecule or receptor site within the organism. The competing ligand studied in this reaction, 8-hydroxyquinoline-5-sulfonate, is a bidentate chelator. The 8-hydroxyquinoline-5- sulfonate ligand is also biologically relevant as the quinoline functional group is present in flavin mononucleotide, a physiological reductant shown to be capable of reducing ferrixomine B in vitro, and in the siderophore quinolobactin. We investigated the reaction of 8-hydroxyquinoline-5-sulfonate with ferrioxamine B in aqueous solution using potentiometry and UV-VIS spectroscopy. By varying the pH and the concentration of 8-hydroxyquinoline-5-sulfonate, we initiated shifts in the equilibrium position while monitoring changes in the reaction component concentrations. Through analysis of the potentiometric and spectrophotometric data, we have determined the products and equilibrium constants associated with this reaction.