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Are dioxetanes chemiluminescent intermediates in lipoperoxidation?
P Di Mascio1, L H Catalani, E J Bechara
1Instituto de Química, Universidade de São Paulo, Brazil.
Free Radical Biology & Medicine
|January 1, 1992
Summary
This study investigates chemiluminescence in lipoperoxidation, questioning the role of dioxetane intermediates. Findings exclude dioxetane formation in lipoperoxidation, clarifying the mechanisms behind ultraweak chemiluminescence.
Area of Science:
- Biochemistry
- Organic Chemistry
- Physical Chemistry
Background:
- Ultraweak chemiluminescence in lipoperoxidation is often attributed to singlet oxygen and triplet carbonyls.
- These emitters are hypothesized to arise from radical annihilation or dioxetane thermolysis during singlet oxygen addition to fatty acids.
Purpose of the Study:
- To question the proposed dioxetane intermediacy in lipoperoxidation.
- To reexamine the chemiluminescence properties of dioxygenated compounds and compare them with a known dioxetane.
Main Methods:
- Comparative analysis of chemiluminescence from dioxygenated tetramethylethylene, linoleic acid, and tetraethyldioxetane.
- Proton nuclear magnetic resonance (1H-NMR) spectroscopy.
- Dioxygen quenching and energy transfer studies using 9,10-dibromoanthracene.
- Gas chromatography (GC) analysis of dioxygenated olefins.
Main Results:
- Literature supports allylic hydroperoxide formation over dioxetanes from singlet oxygen addition to alpha-hydrogen-containing olefins.
- Steric hindrance is necessary for dioxetane formation, yielding very low amounts.
- Experimental data corroborate that dioxetanes are not formed during lipoperoxidation.
Conclusions:
- Dioxetane formation can be safely excluded as a mechanism in lipoperoxidation based on available data.
- Understanding these chemiluminescence pathways is crucial for lipid oxidation research.