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free radicalsHighly chemically active atoms or group of atoms capable of free existence, under special conditions, for very short periods, each having at least one unpaired electron in the outer shell. Oxygen free radicals can be very damaging to DNA and proteins and to the fat in cell membranes where a free radical chain reaction can be set up. They are normally mopped up by ANTIOXIDANTS and associated substances such as vitamins E and C, FLAVONOIDS, selenium, copper, zinc, and manganese. Produced in excess, or insufficiently opposed, free radicals are believed to be implicated in the production of ATHEROSCLEROSIS, cancer, RHEUMATOID ARTHRITIS, radiation sickness and many other conditions. They are thought to be responsible for much of the damage to the heart during the reperfusion that follows a coronary thrombosis. They are said to be promoted by many agents including radiation, atmospheric pollutants and smoking. The body's natural antioxidants include superoxide dismutase and vitamins C and E. See also NANOPARTICLES.
n.pl compounds with an unpaired electron, which makes them extremely reactive.