Part I: Investigation of mechanism(s) of Cu(II) and Zn(II) neurotoxicity Part II: Pre-steady state kinetics of the reduction of cytochrome b561 with ascorbate
Kollalpitiya, Konara Yamuna
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The adverse effects of copper on the catecholaminergic nervous system have been well documented and primarily attributed to its redox related properties. To determine the significance of the redox properties of copper, a comprehensive study of the catecholaminergic toxicity of Cu(II) has been carried out using MN9D, PC12 and SH-SY5Y cells and compared the results with that of non-redox active Zn(II) and nonneuronal HepG2 cells. While Cu(II) is more toxic than Zn(II), membrane permeable metal chelators increase the toxicities of the both metals to catecholaminergic cells in comparison to HepG2 cells. The toxicities of the two metals are parallel to their uptakes and no protection from toxicity is observed with high concentrations of bathocuproine which stabilizes the redox active Cu(I). Thus, the redox properties of Cu(II) are not the primary cause of catecholaminergic toxicity. The increase of reactive oxygen species (ROS) and the apoptotic DNA fragmentation induced by both metals suggest that the apoptotic cell death is due to the excessive ROS production. Significance these findings with respect to intracellular calcium perturbation is discussed. Part II of my research is focused on structural characterization of cyt b561. The protein was isolated from bovine adrenal glands and pre-steady state kinetics of oxidized protein was carried out using stopped-flow absorption spectrophotometry. The reduction kinetics was complex and would be fitted into a linear combination of three exponential functions, providing further evidence for the presence of two heme b centers in the protein.
Thesis (Ph.D.)--Wichita State University, College of Liberal Arts and Sciences, Dept. of Chemistry