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Free radical damage to DNA can occur as a result of exposure to UV radiation or to radiomimetic〔 compounds. Damage to DNA as a result of free radical attack is called indirect DNA damage because the radicals formed can diffuse throughout the body and affect other organs. Malignant melanoma can be caused by indirect DNA damage because it is found in parts of the body not exposed to sunlight. DNA is vulnerable to radical attack because of the very labile hydrogens that can be abstracted and the prevalence of double bonds in the DNA bases that radicals can easily add to. ==Damage via radiation exposure== Radiolysis of intracellular water by UV radiation creates peroxides, which are relatively stable precursors to hydroxyl radicals. 60%- 70% of cellular DNA damage is caused by hydroxyl radicals, yet hydroxyl radicals are so reactive that they can only diffuse one or two molecular diameters before reacting with cellular components. Thus, hydroxyl radicals must be formed immediately adjacent to nucleic acids in order to react. Radiolysis of water creates peroxides that can act as diffusable, latent forms of hydroxyl radicals. Some metal ions in the vicinity of DNA generate the hydroxyl radicals from peroxide. ::: H2O + ''hν'' → H2O+ + e− ::: H2O + e− → H2O− ::: H2O+ → H+ + OH· ::: H2O− → OH− + H· :::2 OH· →H2O2 Once a free radical DNA segment is loose, it can cause cancer and leukemia within the body. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Free radical damage to DNA」の詳細全文を読む スポンサード リンク
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