Cheeseman K H, Slater T F
Department of Biology and Biochemistry, Brunel University, Uxbridge, UK.
Br Med Bull. 1993 Jul;49(3):481-93. doi: 10.1093/oxfordjournals.bmb.a072625.
Free radicals are chemical species possessing an unpaired electron that can be considered as fragments of molecules and which are generally very reactive. They are produced continuously in cells either as accidental by-products of metabolism or deliberately during, for example, phagocytosis. The most important reactants in free radical biochemistry in aerobic cells are oxygen and its radical derivatives (superoxide and hydroxyl radical), hydrogen peroxide and transition metals. Cells have developed a comprehensive array of antioxidant defences to prevent free radical formation or limit their damaging effects. These include enzymes to decompose peroxides, proteins to sequester transition metals and a range of compounds to 'scavenge' free radicals. Reactive free radicals formed within cells can oxidise biomolecules and lead to cell death and tissue injury. Establishing the involvement of free radicals in the pathogenesis of a disease is extremely difficult due to the short lifetimes of these species.
自由基是具有未配对电子的化学物质，可被视为分子片段，通常具有很强的反应性。它们在细胞中持续产生，要么是新陈代谢的意外副产物，要么是在例如吞噬作用过程中有意产生的。需氧细胞中自由基生物化学中最重要的反应物是氧气及其自由基衍生物（超氧化物和羟基自由基）、过氧化氢和过渡金属。细胞已发展出一系列全面的抗氧化防御机制，以防止自由基形成或限制其破坏作用。这些机制包括分解过氧化物的酶、螯合过渡金属的蛋白质以及一系列“清除”自由基的化合物。细胞内形成的活性自由基可氧化生物分子并导致细胞死亡和组织损伤。由于这些物质的寿命很短，确定自由基在疾病发病机制中的作用极其困难。
