Title page for ETD etd-0612102-234815


Type of Document Dissertation
Author Bolzan, Rachel
Author's Email Address rmattin@lsu.edu
URN etd-0612102-234815
Title Peroxynitrite-Mediated Oxidations: Nitration and Nitrosation
Degree Doctor of Philosophy (Ph.D.)
Department Chemistry
Advisory Committee
Advisor Name Title
William A. Pryor Committee Chair
Frank K. Cartledge Committee Member
Neil R. Kestner Committee Member
William H. Daly Committee Member
Arthur M. Sterling Dean's Representative
Keywords
  • mechanism
Date of Defense 2002-05-22
Availability unrestricted
Abstract
Using a direct ultraviolet second-derivative spectroscopy method, three peroxynitrite preparative methods were investigated for the nitrite and nitrate present either as impurities or produced during peroxynitrite decomposition: (I) ozonation of azide, reaction of hydrogen peroxide with (II) isoamyl nitrite and (III) nitrous acid.

The oxidation of morpholine by peroxynitrite in the presence and absence of added carbonate gives N-nitromorpholine and N-nitrosomorpholine. Nitration and nitrosation of morpholine are catalyzed by low levels of CO2; however, excess CO2 dramatically reduces the yields of nitrosation but not nitration, and the combined yields of the products are about the same under conditions of high and low concentrations of CO2. These data indicate that both nitration and nitrosation by peroxynitrite are free radical processes. The morpholine radical, formed from the reactions of carbonate and/or hydroxyl radicals with morpholine, reacts with either NO or NO2 and serves as a common precursor for both products.

The peroxynitrite-mediated oxidation of α-tocopherol and γ-tocopherol dispersed in 1,2-dilauroyl-sn-glycero-3-phosphocholine liposomes in the presence and absence of added carbonate gives α-tocopherylquinone and 5-nitro-γ-tocopherol, respectively. The formation of the products is consistent with the current understanding of the free radical nature of oxidations of peroxynitrite and its CO2-adducts; the overall reaction involves a one-electron oxidation of α-tocopherol and γ-tocopherol by HO or CO3-, followed by the reaction with NO2. When α-tocopherol and γ-tocopherol were present in the same liposome and exposed to peroxynitrite, there was preferential oxidation of α-tocopherol over γ-tocopherol. An explanation for the protection of γ-tocopherol by α-tocopherol could be that γ- and α-tocopheryl radicals, formed from the respective reactions of α-tocopherol and γ-tocopherol with HO or CO3-, disproportionate to give α-tocopherylquinone and regenerated γ-tocopherol. This is consistent with the lack of protection of γ-tocopherol by α-tocopherol when α-tocopherol and γ-tocopherol dispersed in different liposomes but present in the same incubation mixer are subjected to oxidation by peroxynitrite.

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