The Synthesis, Separation, and Identification of Methyl Arachidonate Hydroperoxide Positional Isomers and Their Effect as Components of Large Unilamellar Vesicles on Vesicle Calcium Ion Uptake
Moriarity, Nancy Jean
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https://hdl.handle.net/2142/77461
Description
Title
The Synthesis, Separation, and Identification of Methyl Arachidonate Hydroperoxide Positional Isomers and Their Effect as Components of Large Unilamellar Vesicles on Vesicle Calcium Ion Uptake
Author(s)
Moriarity, Nancy Jean
Issue Date
1987
Department of Study
Food Science
Discipline
Food Science
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Biochemistry
Language
eng
Abstract
Lipid peroxidation has been shown to occur in vitro and in vivo. Physiologically, the process appears to be especially important in detoxification reactions and in prostaglandin and leukotriene production. It has been linked with in vivo aging and peroxides of linoleic and arachidonic acids have been associated with membrane damage.
One of the basic functions of the lipid bilayer membrane is its ability to restrict random ion penetration due to its highly hydrophobic interior. Many cellular processes and enzyme activities are affected by intracellular Ca$\sp{2+}$ concentrations.
The purpose of this study was two-fold. Methyl arachidonate hydroperoxide positional isomers were synthesized, separated, and identified. These compounds were then incorporated into large unilamellar vesicles to investigate their effects on liposomal Ca$\sp{2+}$ uptake.
Hydroperoxides were synthesized by methylene blue-generated singlet oxygen catalysis. Normal and reverse phase HPLC were utilized to separate various positional isomers. Products were identified by GC-MS and quantitated by liquid scintillation counting.
Levels of hydroperoxide incorporation into vesicles were not uniform but were quantitated. Trends indicated that increased vesicle content of methyl arachidonate or its hydroperoxides resulted in decreased Ca$\sp{2+}$ uptake. Vesicles containing neither methyl arachidonate nor its hydroperoxides exhibited the greatest Ca$\sp{2+}$ uptake.
Several positional isomers displayed effects which were exceptions to the overall trends. The 5-hydroperoxide did not decrease Ca$\sp{2+}$ uptake of vesicles to the extent that all other compounds did. Additionally, 6-, and 14-hydroperoxy-methyl arachidonate (the non-conjugated isomers) decreased Ca$\sp{2+}$ uptake even more than methyl arachidonate controls.
When cholesterol was a vesicle component, Ca$\sp{2+}$ uptake data were different. In this case, methyl arachidonate incorporation at low levels resulted in dramatic decreases in vesicle Ca$\sp{2+}$ uptake. However, 15-hydroperoxy-methyl arachidonate incorporation barely effected Ca$\sp{2+}$ uptake.
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