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Publication type: Journal Article
Document type: Full Paper

Year: 1997

Author(s): Liu, Y; Stolze, K; Dadak, A; Nohl, H

Title: Light emission resulting from hydroxylamine-induced singlet oxygen formation of oxidizing LDL particles.

Source: Photochem Photobiol. 1997; 66(4):443-449



Authors Vetmeduni Vienna:

Dadak Agnes
Nohl Hans
Stolze Klaus

Vetmed Research Units
Institute of Pharmacology and Toxicology


Abstract:
Oxidation of low-density lipoprotein (LDL) by low amounts of cupric ions resulted in the formation of singlet oxygen (O-1(2), (1) Delta(g)) when hydroxylamine (NH2OH) was added. Direct evidence on this excited species came from partial spectral resolution of the emitted light in the red spectral region (634 nm and 703 nm), which can be attributed to the dimol decay of singlet oxygen. Additional evidence for the existence of singlet oxygen came from the enhancing effect of deuterium oxide buffer (D2O) on chemiluminescence intensity and the quenching effect of sodium azide. A linear correlation between NH2OH-dependent chemiluminescence intensity and the amount of diene conjugates (DC) formed in this reaction was observed, Removal of adventitious transition metals by adequate chelators prevented chemiluminescence in this system; NH2OH was also found to efficiently decrease metabolites of lipid peroxidation (LPO). Our findings are consistent with a sequence of reactions in which NH2OH first converts transition metals to their reduced state, thereby stimulating the formation of alkoxy-and peroxyradicals. Peroxyradicals decompose in a bimolecular Russel reaction to hydroxyl compounds and singlet oxygen while the majority of alkoxy radicals are eliminated by a secondary reaction with NH2OH. Identical effects were observed when reducing antioxidants such as ascorbic acid or trolox C were used instead of hydroxylamine.

Keywords Pubmed: Antioxidants - pharmacology : Ascorbic Acid - pharmacology : Chemiluminescent Measurements - pharmacology : Chromans - pharmacology : Humans - pharmacology : Hydroxylamine - pharmacology : Light - pharmacology : Lipoproteins, LDL - chemistry : Oxygen - chemistry : Photochemistry - chemistry : Singlet Oxygen - chemistry

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