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The hydroxyl radical can damage virtually all types of macromolecules: carbohydrates, nucleic acids , lipids (lipid peroxidation) and amino acids (e.g. conversion of Phe to m-Tyrosine and o-Tyrosine). The hydroxyl radical has a very short in vivo half-life of approximately 10 −9 seconds and a high reactivity. [5]
Haber, Wilstätter and Weiss simply wrote HO 2 or O 2 H, but sometimes HO 2 • or • O 2 H can also be found to stress the radical character of the species. The hydroperoxyl radical is a weak acid and gives rise to the superoxide radical (O 2 •–) when it loses a proton: HO 2 → H + + O 2 – sometimes also written as: HO 2 • → H ...
Hydroxyl radical (HO·) is generated by Fenton reaction of hydrogen peroxide with ferrous compounds and related reducing agents: Fe(II) + H 2 O 2 → Fe(III)OH + HO· In its fleeting existence, the hydroxyl radical reacts rapidly irreversibly with all organic compounds. superoxide (O − 2) is produced by reduction of O 2. [4]
Hydroxyl radicals are then generated via the Haber–Weiss reaction or the Fenton reaction, of which are both catalyzed by Fe 2+. O 2 •– + H 2 O 2 —> • OH + OH – + O 2 In the presence of halide ions, prominently chloride ions, myeloperoxidase uses hydrogen peroxide to produce hypochlorous acid .
The fact that oxygen changes the radiation chemistry might be one reason why oxygenated tissues are more sensitive to irradiation than the deoxygenated tissue at the center of a tumor. The free radicals, such as the hydroxyl radical, chemically modify biomolecules such as DNA, leading to damage such as breaks in the DNA strands. Some substances ...
In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula −OH and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry , alcohols and carboxylic acids contain one or more hydroxy groups.
The hydroxyl radical reacts with the various hydrogen atoms of the deoxyribose in the order 5′ H > 4′ H > 3′ H ≈ 2′ H ≈ 1′ H. This order of reactivity parallels the exposure to solvent of the deoxyribose hydrogens. [6] Hydroxyl radicals react with DNA bases via addition to the electron-rich, pi bonds.
The free radicals generated by this process engage in secondary reactions. For example, the hydroxyl is a powerful, non-selective oxidant. [6] Oxidation of an organic compound by Fenton's reagent is rapid and exothermic and results in the oxidation of contaminants to primarily carbon dioxide and water.