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Free Radicals: The Rogues of Chemistry
| Article
# : |
14566 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
3 / 1988 |
2,001 Words |
| Author
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Michael G. Simic and Karen A. Taylor
Michael G. Simic is a research biochemist at the National
Bureau of Standards in Gaithersburg, Maryland. Karen A. Taylor
is a biologist working for the International Life Science
Institute in Washington, D.C. |
Free radicals are all around and within us, participating in myriad process. Yet only now, with the advent of sophisticated instrumentation and detection systems, are scientists beginning to understand the far-reaching implications of these unstable, highly reactive, and short-lived chemical species.
Part I of this three-part series on free radicals introduces the basic concept of free radicals and surveys the history and development of this field. Parts II and III will explore the important, newly discovered roles of free radicals in biology and medicine respectively.
The tremendous energy and destructive potential of free radicals was demonstrated on January 28, 1986, by the tragic explosion of the space shuttle Challenger. When a defective O-ring failed, leaking hot gases began to burn outside the solid rocket motor. Within seconds, the flame breached the external tank containing liquid hydrogen fuel and liquid oxygen oxidizer. Uncontrolled mixing of the hydrogen and oxygen occurred, leading--almost instantaneously--to an explosion, which is a chain-branching free radical reaction. The spectacular fireball and explosion resulting from these free radical reactions destroyed the Challenger, an event permanently etched in the memory of all who witnessed the disaster.
Almost 50 years earlier, the devastating consequences of free-radical-based reactions of hydrogen with oxygen were imprinted on the consciousness of another generation. In 1937 the German airship Hindenburg, a huge hydrogen-filled zeppelin, caught fire and burned in seconds, killing 36 passengers and crew members. A spark--perhaps due to static electricity discharge from the atmosphere or even sabotage--caused free radicals to form in the mixture of hydrogen leaking from the airship and atmospheric oxygen. Both incidents serve as reminders that hydrogen, one of the cleanest and most efficient fuels, may also participate in violent reactions driven by its free radical form.
Free radicals are involved in many processes, from those that threaten the delicate balance of life to those that are essential to life. Although few people know of their existence, free radicals of many different kinds are part of our everyday life. Far from being exotic, they are intrinsic to many natural and technological processes. Sunlight generates free radicals in the upper atmosphere. Combustion engines that power cars and trucks depend on free radicals as intermediates in the generation of energy from fuel. At the same time, this process of hydrocarbon combustion in the engines
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